Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
DSpace
UBCV
Zeko, David
Master of Science - MSc
University of British Columbia
Fully carbonated peridotite, known as listvenite, is well exposed along the basal thrust of the Oman ophiolite. Outcrops of listvenite are a fossilized record of fluid-rock interactions that resulted in the storage of billions of tonnes of CO₂, providing researchers insight into an important global carbon sink and a potential natural analogue to in situ carbon sequestration. The goal of this thesis is to investigate the formation of listvenite using samples from the Oman Drilling Project to 1) characterize the petrology and geochemistry of listvenite, 2) determine the mineral reaction sequence and the physical and chemical conditions required and 3) constrain the potential sources of CO₂ bearing fluids. Three carbonated lithologies were observed: 1) serpentine with variable amounts magnesite and dolomite veining (ophicarbonate); 2) serpentine with abundant vein and matrix hosted magnesite, dolomite, talc and quartz (talc-ophicarbonate); and 3) intergrown magnesite, dolomite and quartz (listvenite). With the exception of H₂O, CO₂ and variable amounts of Ca, the major element geochemical composition of all three lithologies approximates unaltered peridotite. Fluid mobile trace elements such as Cs, Rb and Sr are enriched in listvenite to over 100-times that of unaltered peridotite and correlate with increasing δ¹³C values. δ¹³C values increase with carbonation from ~-7 δ¹³C in ophicarbonate samples through to ~+2 δ¹³C in listvenite, representing the progressive dilution of mantle-derived carbon with marine-derived carbon. Detailed petrography and thermodynamic phase equilibria modelling demonstrate that listvenite formed via a series of mineral reactions resulting in the breakdown of serpentine and the formation of magnesite, dolomite, talc and quartz. Crosscutting relationships between carbonate minerals and deformation structures, in combination with oxygen isotopic exchange thermometry, reveal that carbonation reactions were driven by at least two pulses of CO₂-bearing fluids that originated from, or interacted with, the metamorphic rocks below. The first pulse is associated with deformed matrix- and vein-hosted magnesite carbonation at 150-250 ℃, which potentially occurred pre-syn obduction at shallow depths within a subduction zone. This was followed by a later pulse of calcium-rich fluids associated with late undeformed dolomite carbonation at 50-100 ℃, which potentially occurred syn-post obduction during thrusting over carbonate shelf sediments.
CARBONATION OF THE OMAN OPHIOLITE DURING SUBDUCTION AND EMPLACEMENT by David Zeko BEnvSci (Hons), The University of Wollongong, 2009 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Geological Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) January 2021 © David Zeko, 2021 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis entitled: Carbonation of the Oman Ophiolite During Subduction and Emplacement submitted by David Zeko in partial fulfillment of the requirements for the degree of Master of Science in Geological Sciences Examining Committee: Prof. Greg Dipple, Earth, Ocean and Atmospheric Sciences, UBC Supervisor Prof. Lee Groat, Earth, Ocean and Atmospheric Sciences, UBC Supervisory Committee Member Prof. Brendan Dyck, Earth, Ocean and Atmospheric Sciences, UBC Additional Examiner Additional Supervisory Committee Members: Dr. Tyler Ambrose, Yukon Geological Survey Supervisory Committee Member iii Abstract Fully carbonated peridotite, known as listvenite, is well exposed along the basal thrust of the Oman ophiolite. Outcrops of listvenite are a fossilized record of fluid-rock interactions that resulted in the storage of billions of tonnes of CO2, providing researchers insight into an important global carbon sink and a potential natural analogue to in situ carbon sequestration. The goal of this thesis is to investigate the formation of listvenite using samples from the Oman Drilling Project to 1) characterize the petrology and geochemistry of listvenite, 2) determine the mineral reaction sequence and the physical and chemical conditions required, and 3) constrain the potential sources of CO2-bearing fluids. Three carbonated lithologies were observed: 1) serpentine with variable amounts magnesite and dolomite veining (ophicarbonate); 2) serpentine with abundant vein and matrix hosted magnesite, dolomite, talc and quartz (talc-ophicarbonate); and 3) intergrown magnesite, dolomite and quartz (listvenite). With the exception of H2O, CO2 and variable amounts of Ca, the major element geochemical composition of all three lithologies approximates unaltered peridotite. Fluid mobile trace elements such as Cs, Rb and Sr are enriched in listvenite to over 100-times that of unaltered peridotite and correlate with increasing δ13C values. δ13C values increase with carbonation from ~-7 δ13C in ophicarbonate samples through to ~+2 δ13C in listvenite, representing the progressive dilution of mantle-derived carbon with marine-derived carbon. Detailed petrography and thermodynamic phase equilibria modelling demonstrate that listvenite formed via a series of mineral reactions resulting in the breakdown of serpentine and the formation of magnesite, dolomite, talc and quartz. Crosscutting relationships between carbonate minerals and deformation structures, in combination with oxygen isotopic exchange thermometry, reveal that carbonation reactions were driven by at least two pulses of CO2-bearing fluids that originated from, or interacted with, the metamorphic rocks below. The first pulse is associated with deformed matrix- and vein-hosted magnesite carbonation at 150-250 ℃, which potentially occurred pre-syn obduction at shallow depths within a subduction zone. This was followed by a later pulse of Ca-rich fluids associated with late undeformed dolomite carbonation at 50-100 ℃, which potentially occurred syn-post obduction during thrusting over carbonate shelf sediments. iv Lay Summary Ultramafic rocks are rich in metals such as Mg and Fe and have the ability to absorb large amounts of carbon dioxide by forming stable carbonate minerals such as magnesite. In the Sultanate of Oman, ultramafic rocks that formed deep below oceanic crust were tectonically thrust onto land. During this process, billions of tons of carbon dioxide was sequestered through mineral carbonation. This thesis shows that mineral carbonation in Oman proceeded via a series of chemical reactions that broke down minerals in the oceanic crust, such as olivine and orthopyroxene, to form new minerals such as talc, magnesite and dolomite. These reactions were driven by two pulses of carbonating fluids that originated from carbonate-bearing metamorphic rocks immediately below. The carbonating fluids varied in temperature between 50 and 250 ℃ and contained upwards of 0.01% carbon dioxide. These conditions could be replicated in engineered mineral carbonation systems to sequester CO2. v Preface The main academic supervisor of this project, Prof. Greg Dipple (University of British Columbia, Canada), is credited with the initial project design and facilitating my involvement with the Oman Drilling Project. Both the author and Prof. Greg Dipple are responsible for the identification of the research objectives. Research committee members Prof. Lee Groat (University of British Columbia) and Dr. Tyler Ambrose (Yukon Geological Survey, Canada) are credited with providing input through committee meetings, independent correspondence and reviewing this thesis. As the author of this thesis, I am accountable for the following: • Field work involving onsite supervision of drilling in Oman during March 2016 (4 weeks) and detailed core description and sampling onboard the Chikyu research vessel in Japan during September 2017 (4 weeks). Fieldwork was conducted as part of the Oman Drilling Project Science Team with direct supervision by chief scientist Prof. Peter Keleman (Columbia University, USA), Project Manager Dr. Jude Coggon (Southampton University, United Kingdom), and Project Steering Committee member Prof. Craig Manning (University of California, USA); • Sample preparation (rock cutting, micro-drilling, sample weighing and micronizing) conducted at the Department of Earth, Atmospheric and Ocean Sciences; • Petrographic analysis of thin sections using the light microscopy facility at the Mineral Deposit Research Unit (MDRU) at the University of British Columbia; • Quantitative X-Ray Diffraction at the Electron Microbeam/X-ray Diffraction Facility (University of British Columbia) with training and technical assistance provided by research scientists Dr Connor Turvey, Jenny Lai and Lan Kato; • Microbeam petrography and geochemistry by SEM and EMPA at the Electron Microbeam/X-ray Diffraction Facility (University of British Columbia), with training and technical assistance provided by research scientists Jacob Kabel, Edith Czech, Jenny Lai and Lan Kato; vi • Stable carbon and oxygen isotope analysis by OA-ICOS located in the CarbMin Lab at the University of British Columbia, with training and technical assistance provided by lab technicians Suleiman Mohamed and Francis Jones. The instrument was run by the author for approximately 50% of samples analysed, with the remainder run by the lab technicians. • Thermodynamic modelling using Perple_X software (Connolly, 2009), with training and technical assistance provided by research scientist Dr Tyler Ambrose; and • Data analysis and presentation with Matlab, ioGAS, MS Office and Adobe Suite, with guidance and feedback provided by Prof. Greg Dipple. Independent laboratories performed the following: • Thin section preparation at Vancouver Petrographics Ltd. in Langley, British Columbia; and • Whole-rock geochemical analysis at ALS laboratories in North Vancouver, British Columbia. This thesis used data and samples obtained from the Oman Drilling Project (see acknowledgements). A large collective data set was generated by the Oman Drilling Project Science Party which includes thin section petrography, XRD mineralogy, geochemistry, high resolution photography, CT scans, hyperspectral imaging, XRF maps, physical properties and downhole geophysics (see section 2.2.2). This collective data set informed the sampling strategy and geological interpretations presented in this thesis. Cross-cutting relationships between veins and structural features discussed in this study are largely based on the collective work of the Oman Drilling Project Science Team. I contributed to this collective data set during shipboard core description onboard the Chikyu with descriptions of the morphology and mineralogy of veins, measurement of the abundance and size of veins, determining cross-cutting relationships between veins, describing vein halo morphology and mineralogy, identification and description of structural features such as brecciation, cataclasites, shearing and faulting, and determination of cross-cutting relationships between structural features and veins. The collective data was under a two- and half-year moratorium (Sep 2017 - Feb 2020), only accessible to members of the Oman Drilling Project Science Team. This moratorium has vii expired, and the collective data is available to other researchers upon request (https://www.omandrilling.ac.uk/samples-data). All members of the OmanDP Science Parties who receive samples or data incur obligations to conduct research during the moratorium period and publish their data and results in an English language peer-reviewed scientific journal, or a peer-reviewed data report. viii Table of Contents Abstract ......................................................................................................................................... iii Lay Summary ............................................................................................................................... iv Preface .............................................................................................................................................v Table of Contents ....................................................................................................................... viii List of Tables ................................................................................................................................ xi List of Figures .............................................................................................................................. xii List of Abbreviations ...................................................................................................................xv Acknowledgements .................................................................................................................... xvi Dedication ................................................................................................................................. xviii Chapter 1: Introduction ................................................................................................................1 1.1 Introduction to fluid-rock interactions in subduction zones ........................................... 1 1.2 Introduction to listvenite ................................................................................................. 2 1.3 Volume expansion and reaction driven cracking ............................................................ 6 1.4 Sources of carbonating fluids .......................................................................................... 8 1.5 Thesis objectives ............................................................................................................. 9 1.6 Introduction to the Oman Drilling Project ...................................................................... 9 1.7 Geological background ................................................................................................. 11 1.7.1 Introduction to ophiolites ...................................................................................... 11 1.7.2 Stratigraphy of the Oman-United Arab Emirates ophiolite .................................. 12 1.7.3 Tectonic setting of the Oman-UAE ophiolite ....................................................... 13 1.7.4 Geochronology of the Oman-UAE ophiolite ........................................................ 14 Chapter 2: Carbonation of Peridotite at the Base of the Oman Ophiolite by Two Pulses of CO2-Bearing Fluids ......................................................................................................................15 2.1 Introduction ................................................................................................................... 15 2.2 Methods......................................................................................................................... 16 2.2.1 BT1 drill site ......................................................................................................... 16 2.2.2 Drill site sample collection and shipboard core description ................................. 18 2.2.3 Thesis sample collection ....................................................................................... 18 2.2.4 Sample preparation and geochemical analysis ..................................................... 19 ix 2.3 Quantitative mineralogy ................................................................................................ 20 2.4 Thermodynamic phase equilibria modelling ................................................................ 20 2.4.1 EMPA microbeam petrography and geochemistry ............................................... 22 2.4.1.1 Scanning electron microscope .......................................................................... 22 2.4.1.2 Electron microprobe .......................................................................................... 22 2.4.2 Stable isotopes ...................................................................................................... 23 2.5 Results ........................................................................................................................... 24 2.5.1 Overview of rock types ......................................................................................... 24 2.5.2 Microtextures and mineral assemblages ............................................................... 25 2.5.2.1 Ophicarbonate ................................................................................................... 26 2.5.2.2 Talc-ophicarbonate ........................................................................................... 32 2.5.2.3 Listvenite ........................................................................................................... 42 2.5.2.4 Carbonates and veining ..................................................................................... 48 2.5.3 Whole-rock quantitative mineralogy .................................................................... 52 2.5.4 Whole-rock geochemistry ..................................................................................... 54 2.5.4.1 Major elements .................................................................................................. 54 2.5.4.2 Trace elements .................................................................................................. 61 2.5.5 Stable carbon and oxygen isotopes ....................................................................... 66 2.5.6 Magnetite destruction ............................................................................................ 71 2.5.7 Expected assemblages from phase equilibria modelling ...................................... 75 2.6 Discussion ..................................................................................................................... 79 2.6.1 Formation of listvenite .......................................................................................... 79 2.6.1.1 Overview ........................................................................................................... 79 2.6.1.2 Ophicarbonate formation .................................................................................. 82 2.6.1.3 Talc-ophicarbonate formation ........................................................................... 85 2.6.1.4 Listvenite formation .......................................................................................... 87 2.6.2 Dolomite veins and structural relationships .......................................................... 88 2.6.3 Isotopes and carbonating fluid source ................................................................... 90 2.6.4 Fluid compositions ................................................................................................ 92 2.6.4.1 Element enrichments and fluid source .............................................................. 94 Chapter 3: Conclusions ...............................................................................................................98 x 3.1 Overview ....................................................................................................................... 98 3.2 Objectives ..................................................................................................................... 98 3.2.1 Characterization of mineral assemblages .............................................................. 98 3.2.2 Thermodynamic phase equilibria modelling of carbonation reactions ............... 100 3.2.3 Constraining the potential sources of carbonating fluids .................................... 101 3.3 Strengths and limitations of the research .................................................................... 102 Bibliography ...............................................................................................................................104 Appendices ..................................................................................................................................115 Appendix A .............................................................................................................................. 115 A.1 Sample descriptions ................................................................................................ 115 A.2 Whole-rock quantitative mineralogy ....................................................................... 136 A.3 Whole-rock quantitative mineralogy with amorphous content ............................... 138 A.4 Sources of crystal structure data for Rietveld refinement ...................................... 140 A.5 Whole-rock major element geochemistry ................................................................ 141 A.6 Whole-rock trace element geochemistry ................................................................. 144 A.7 Whole-rock stable carbon and oxygen isotopes ...................................................... 155 A.8 Electron microprobe analysis of carbonates .......................................................... 157 A.9 Quantitative mineralogy from microdrill ................................................................ 162 A.10 Stable carbon and oxygen isotopes from microdrill ............................................... 164 xi List of Tables Table 1-1: Summary of mineral assemblages and reactions published for three listvenite localities. ......................................................................................................................................... 4 Table 2-1. OmanDP shipboard data collection. ............................................................................ 19 Table 2-2. Bulk composition of average Oman harzburgite used for thermodynamic modelling........................................................................................................................................................ 21 Table 2-3. Solution models used in Perple_X to account for substitution of chemical components into minerals. ................................................................................................................................. 21 Table 2-4. Summary of vein types from oldest to youngest in serpentinite and listvenite above the basal thrust. ............................................................................................................................. 49 Table 2-5. Summary of whole-rock quantitative mineralogy obtained using XRD and Rietveld refinement. .................................................................................................................................... 53 Table 2-6. Summary of major element geochemistry by rock type. ............................................. 55 xii List of Figures Figure 1-1. Schematic cross section illustrating fluid expulsion in subducting oceanic crust. ...... 1 Figure 1-2. Examples of listvenite at the hand sample scale at three outcrops. ............................. 2 Figure 1-3. Soapstone reaction fronts at three localities. ................................................................ 3 Figure 1-4. Serpentine kernel pattern at Linnajavri Norway. ......................................................... 7 Figure 1-5. Location of Oman Drill Project holes linked to targeted features in the oceanic crust........................................................................................................................................................ 11 Figure 1-6. Simplified geological map of the Oman-UAE ophiolite and metamorphic sole. ...... 13 Figure 2-1. Simplified geological map illustrating the location of all holes drilled as part of the Oman Drilling project. .................................................................................................................. 17 Figure 2-2. Photomicrographs of ophicarbonate textures and veining from sample 17-DZ-39-4.27 Figure 2-3. Photomicrographs of ophicarbonate textures and veining from sample 17-DZ-39-4.28 Figure 2-4. BSE image and EDS element maps of ophicarbonate sample 17DZ-43-5. ............... 30 Figure 2-5. BSE image and EDS element maps of ophicarbonate sample 17DZ-39-4. ............... 31 Figure 2-6. BSE Image and EDS element maps of talc ophicarbonate sample 17DZ-44-4D. ..... 33 Figure 2-7. Photomicrographs displaying textural relationships in srp-mgs-tlc assemblages from sample 17DZ-44-2. ....................................................................................................................... 34 Figure 2-8. Photomicrographs displaying textural relationships in srp-mgs-tlc assemblage from sample 17DZ-44-2. ....................................................................................................................... 35 Figure 2-9. Photomicrographs of textures and veining displaying mgs-tlc-qtz assemblage in sample 17DZ-44-4D. .................................................................................................................... 36 Figure 2-10. EDS Element maps and BSE image of mgs-tlc-qtz assemblage from sample 17DZ-44-4C............................................................................................................................................. 37 Figure 2-11. EDS Element maps and BSE image of mgs-tlc-qtz assemblage from sample 17DZ-44-4C............................................................................................................................................. 38 Figure 2-12. Photomicrographs from sample 17DZ-44-2 displaying textural relationships in srp-mgs-tlc. .......................................................................................................................................... 39 Figure 2-13. BSE image and EDS Element maps of mgs-tlc-qtz and srp-mgs-qtz domains from sample 17DZ-44-4C. ..................................................................................................................... 40 xiii Figure 2-14. Magnesite, dolomite and quartz veining in a srp-mgs-qtz domain of sample 17DZ-44-4d. ............................................................................................................................................ 41 Figure 2-15. BSE Image and element maps of listvenite sample 17DZ-38-3.. ............................ 44 Figure 2-16. EDS Element maps and BSE image of magnesite-listvenite sample 17DZ-26-2. ... 45 Figure 2-17 Photomicrographs of brecciated red listvenite from sample 17DZ-17-4. ................. 46 Figure 2-18. Photomicrographs of grey and green listvenite from sample 17DZ-63-3. ............... 47 Figure 2-19. Composition of carbonate grains in the various rock types encountered. ................ 50 Figure 2-20. Cross polarized photomicrographs of vein types encountered. ............................... 51 Figure 2-21. Volatile free major element ratios in Oman listvenite in comparison to unaltered dunite and harzburgite. .................................................................................................................. 56 Figure 2-22. Volatile free major element ratios in Oman listvenite in comparison to unaltered dunite and harzburgite. .................................................................................................................. 57 Figure 2-23. Major element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite. ................................................................................................. 58 Figure 2-24. Major element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite. ................................................................................................. 59 Figure 2-25. Comparing CaO and dolomite concentrations. ........................................................ 60 Figure 2-26. Trace element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite. ................................................................................................. 62 Figure 2-27. Trace element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite. ................................................................................................. 63 Figure 2-28. Volatile free trace element ratios with Al2O3. .......................................................... 64 Figure 2-29. Volatile free trace element ratios with CaO and K2O. ............................................. 65 Figure 2-30. Cs and Rb concentrations categorized by major micaceous minerals identified with spectral analysis. ........................................................................................................................... 66 Figure 2-31. Stable carbon isotopes (δ13C) plotted against depth. ................................................ 68 Figure 2-32. Stable oxygen isotopes (δ18O) plotted against depth. .............................................. 69 Figure 2-33. Summary of stable carbon and oxygen isotopes of carbonates by lithology. .......... 70 Figure 2-34. Stable carbon and oxygen isotopes vs CO2. ............................................................. 71 Figure 2-35. Photomicrographs of hematite distribution surrounding a chromite grain in upper listvenite sample 17DZ-17-4. ........................................................................................................ 72 xiv Figure 2-36. Modal abundance of magnetite and hematite with increasing CO2 concentration of samples. ......................................................................................................................................... 73 Figure 2-37. Downhole magnetic susceptibility data obtained from the Oman Drilling Project Science Team plotted with magnetite and hematite abundance. .................................................. 74 Figure 2-38. Thermodynamic modelling showing the pressure, temperature and mole fraction of CO2 in the infiltrating fluid. .......................................................................................................... 77 Figure 2-39. Cumulative modal abundance of mineral phases with changes in pressure, temperature and CO2. .................................................................................................................... 78 Figure 2-40. Mineral reactions forming the various carbonated assemblages encountered at the base of the Oman ophiolite.. ......................................................................................................... 81 Figure 2-41. Thermodynamic modelling illustrating oxidation state of Fe below 200℃ in equilibrium with an excess of low CO2 fluid. ............................................................................... 84 Figure 2-42. Schematic of incipient carbonation in talc-ophicarbonate adjacent to the lower listvenite. ....................................................................................................................................... 86 Figure 2-43. Stable carbon and oxygen isotope values of carbonates labelled by lithology and compared to other carbonates ....................................................................................................... 90 Figure 2-44. Calculated oxygen isotope composition of carbonating fluids. ............................... 93 Figure 2-45. Stable carbon and oxygen isotopes plotted with volatile free Cs and Rb concentrations. .............................................................................................................................. 95 Figure 2-46. Stable carbon and oxygen isotopes vs relative dolomite abundance. ...................... 96 xv List of Abbreviations All mineral abbreviations after Whitney and Evans (2010) BSE: backscattered electron EDS: energy-dispersive X-ray spectroscopy EOAS: Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia EMXDF: Electron Microbeam and X-Ray Diffraction Facility EPMA: electron probe micro-analyzer Excel: Microsoft Excel HREE: heavy rare earth elements ICP-MS: inductively-coupled plasma mass spectrometry ioGAS: Reflex ioGAS software LREE: light rare earth element Matlab: MathWorks Matlab Software MDRU: Mineral Deposit Research Unit, University of British Columbia NSERC-CRD: Natural Sciences and Engineering Research Council of Canada Collaborative OA-ICOS: off-axis integrated cavity output spectrometer OmanDP: Oman Drilling Project PPL: plane polarized light REE: rare earth elements SEM: scanning electron microscope UBC: University of British Columbia XPL: cross polarized light XRD: X-ray diffraction XRF X-ray fluorescence xvi Acknowledgements I would like to offer my enduring gratitude for all people involved in the completion of this project. I owe particular thanks to Prof. Greg Dipple for accepting me as a student, facilitating my involvement in the Oman Drilling Project and providing many hours of direction and insightful feedback. I would also like to thank all of those who took time out of their busy schedules to provide me with the training and oversight necessary to complete my research: Prof. Lee Groat and Dr. Tyler Ambrose for questions and feedback during committee meetings and reviewing of this thesis; Dr. Tyler Ambrose for his mentorship in thermodynamic modelling; Dr. Connor Turvey for his training and oversight running the XRD instrument and software; and Jacob Kabel, Jenny Lai, Lan Kato and Edith Czech of the UBC EOAS Microbeam Facility for their guidance and patience as I learnt to use the SEM and microprobe. I owe great thanks to Prof. Peter Kelmen, Dr. Jude Coggon, Prof. Craig Manning and fellow researchers on the Oman Drilling Project Science Team for their guidance during fieldwork in Oman and onboard the Chikyu—what an adventure and privilege it was. I am thankful to have been involved with the department as both a student and teaching assistant. It was a pleasure to share the ups and downs of the learning journey with my fellow EOAS students and be given the opportunity to contribute to the training of undergraduate geologists. The research in this thesis was funded by a Natural Sciences and Engineering Research Council of Canada Discovery Grant (Dipple PI) and uses samples and data from the Oman Drilling Project. The Oman Drilling Project has been possible through co-mingled funds from the International Continental Scientific Drilling Project (ICDP; Kelemen, Matter, Teagle Lead PIs), the Sloan Foundation – Deep Carbon Observatory (Grant 2014-3-01, Kelemen PI), the National Science Foundation (NSF-EAR-1516300, Kelemen lead PI), NASA – Astrobiology Institute (NNA15BB02A, Templeton PI), the German Research Foundation (DFG: KO 1723/21-1, Koepke PI), the Japanese Society for the Promotion of Science (JSPS no:16H06347, Michibayashi PI; and KAKENHI 16H02742, Takazawa PI), the European Research Council (Adv: no.669972; Jamveit PI), the Swiss National Science Foundation (SNF:20FI21_163073, Früh-Green PI), JAMSTEC, the TAMU-JR Science Operator, and contributions from the Sultanate of Oman Ministry of Regional Municipalities and Water Resources, the Oman Public xvii Authority of Mining, Sultan Qaboos University, CNRS-Univ. Montpellier, Columbia University of New York, and the University of Southampton. xviii Dedication To my friends and family who supported me along this journey, without you it would not have been possible. It is my hope that this research will make some small contribution to our understanding of the carbon cycle and that this knowledge be utilized to lessen our impact on the planet. 1 Chapter 1: Introduction 1.1 Introduction to fluid-rock interactions in subduction zones Fluid-rock interactions in the oceanic lithosphere are an important component of hydrosphere-lithosphere volatile exchange and planetary-scale element cycles (Jamtveit et al., 2000). As seawater infiltrates mantle rocks, a variety of water-rock interactions can lead to the conversion of mafic minerals (olivine and pyroxene) to serpentine (antigorite, chrysotile and lizardite) and accessory phases (magnetite, brucite and talc; (O’Hanley, 1992). This process is known as serpentinization and has played a central role in the biogeochemical and tectonic evolution of the Earth (Smit & Mezger, 2017). In subduction zones, large volumes of water are released from subducting oceanic crust and sediments, leading to serpentinization of the overlying mantle wedge (Hyndman & Peacock, 2003) (Figure 1-1). Where subducting sediments are rich in carbonate material, carbonation of peridotite in the mantle wedge is also expected (Kelemen & Manning, 2015). Carbonation of peridotite is an important fluid-rock interaction resulting in the storage of billions of tonnes of CO2 and (Kelemen et al., 2011) and has been studied extensively as a natural analogue to in situ carbon sequestration (Kelemen & Matter, 2008; Lackner et al., 1995; Power et al., 2013). Figure 1-1. Schematic cross-section illustrating fluid expulsion in subducting oceanic crust that results in serpentinization ± carbonation of the overlying crust and mantle, modified after Hyndman and Peacock (2003). 2 1.2 Introduction to listvenite Peridotite is a dense, coarse grain ultramafic rock comprised mainly of olivine and pyroxene minerals rich in divalent cations, such as Mg, Fe and Ca. During fluid-rock interactions these divalent metal cations become liberated and readily combine with bicarbonate (HCO3-) and carbonate (CO32-) ions to form carbonate minerals such as magnesite (MgCO3), dolomite (MgCa(CO3)2) and calcite (CaCO3). Listvenite (Figure 1-2) is a fully carbonated peridotite, composed of carbonate minerals, quartz, chromian mica (fuchsite) and relict chromian spinel) (Halls & Zhao, 1995). The term “listvenite” is rooted in the Russian word listvennitsa, meaning larch tree, and was initially proposed by Gustav Rose in 1837 for the green rocks found in lode gold deposits of the Ural mountains (Belogub et al., 2017; Rose, 1837). More recent works on listvenite have focused on the conditions under which complete carbonation of peridotite can occur, highlighting listvenite outcrops as a natural analogue to in situ mineral carbon sequestration (Beinlich et al., 2012; Hansen et al., 2005; Kelemen et al., 2011). Figure 1-2. Examples of listvenite at the hand sample scale at three outcrops: (a) Wadi Mansah Oman with zoned discontinuous quartz-dolomite veins crosscutting the hematite rich magnesite-quartz listvenite matrix (after Falk and Kelemen, 2015); (b) Linnejavri Norway displaying coarse-grained listvenite veins with euhedral quartz and mgs crystals (after Beinlich et al., 2012); and (c) Advocate Ophiolite, Nova Scotia showing layered listvenite with crosscutting quartz-magnesite and fuchsite-veins (after Menzel et al., 2018). Present at many listvenite localities are zones of spatially distinct mineral assemblages that provide evidence for the mineral reactions that form listvenite (Hansen et al., 2005). Two key mineral reactions are the “soapstone” reaction (R2), which produces talc and magnesite, and the “listvenite” reaction (R3), which produces quartz and magnesite (Table 1-1). These 3 mineralogical zones record varying degrees of grain-scale fluid infiltration that has propagated relatively quickly (up to 10cm/yr.) over 100s of meters to kilometres (A Beinlich et al., 2020). Figure 1-3 below presents three examples of soapstone reaction fronts. Figure 1-3. Soapstone reaction fronts at three localities. Dashed lines represent reaction fronts with arrows depicting the direction of propagation into unreacted serpentinite. (a) Sharp reaction fronts between the soapstone and the serpentinite are hundreds of metres in length in Linnajavri, Norway (after Beinlich et al., 2012). (b) Contact of Atg-serpentinite and Ant-Tlc-Mgs assemblages in the Advocate Ophiolite, Nova Scotia (after Menzel et al., 2018) (c) Zoned soapstone reaction fronts from Wadi Abyad, Oman, composed primarily of magnesite + talc ± serpentine, occurring as localized centimetre to meter-scale zones within serpentinized peridotite (after Falk and Kelemen, 2015). Well-studied outcrop exposures of listvenite occur along the basal thrust of the Oman ophiolite (Falk & Kelemen, 2015; Nasir et al., 2007) and in ophiolites at other localities including Linnajavri, Norway (Beinlich et al., 2012); Atlin, British Columbia, Canada (Hansen et al., 2005); and the Baie Verte Peninsula, Newfoundland, Canada (Menzel et al., 2018). The listvenite occurrences in all these field areas are associated with thrust faults that emplace the ophiolite on top of dehydrated sediments; as such, it is likely that faulting plays a role in the development of permeability and that the sediments below are a potential source of fluid and carbon (Falk & Kelemen, 2015; Hansen et al., 2005; Kelemen & Manning, 2015). A summary of the mineral assemblages and chemical reactions for the Atlin, Linnejavri and Oman listvenite outcrops are presented in Table 1-1 below, followed by some comments on the similarities and differences between them. 4 Table 1-1: Summary of mineral assemblages and reactions published for three listvenite localities labelled according to Hansen et al. (2005). Location & Reference Mineral Assemblages* Reactions # Atlin, Northern British Columbia, Canada (Hansen et al., 2005) A1. serpentine + brucite ± olivine A2. serpentine + magnesite A3. talc + magnesite A4. quartz + magnesite Prograde R1a. 34 ol + 20 CO2 + 31 H2O à atg + 20 mgs R1b. bru + CO2 à mgs + H2O R2a. 2 atg + 45 CO2 à 45 mgs + 17 tlc + 45 H2O R3. tlc + 3 CO2 à 3 mgs + 4 qtz + H2O Linnajavri, Northern Norway (Beinlich et al., 2012) A2. serpentine + dol + clinochlore + magnetite ± talc/tremolite A3. talc + magnesite ± chlorite A4. quartz + magnesite ± chlorite, talc, tourmaline, muscovite, biotite, plagioclase and titanite Prograde R2a. 2 atg + 45 CO2 à 17 tlc + 45 mgs + 4 qtz + H2O R2b. atg + 15 di + 30 CO2 à 15 dol +16 tlc + 15 H20 R2c. atg + 15 tr + 60 CO2 à 30 dol + 47 tlc + 30 H2O R3. Tlc + 3 CO2 à 3 mgs + 4 qtz + H2O Wadi Mansah, Sumail Massif, Sultanate of Oman (Falk & Kelemen, 2015) A1. serpentine + magnetite ± olivine A2. serpentine + magnesite ± dolomite, talc, chlorite and qtz A4. magnesite + quartz ± dolomite, Fe-oxides and fuchsite Prograde R2a. 2 atg + 45 CO2 à 45 mgs + 17 tlc + 45 H2O R3. Tlc + 3 CO2 à 3 mgs + 4 qtz + H2O R4. atg + 48 CO2 à 48 mgs + 34 qtz + 31 H2O Retrograde R5. 16 tlc + 15 H20 à ant + 30 qtz * A1 = serpentinite, A2 = ophicarbonate, A3 = soapstone, A4 =listvenite # ol = olivine (Mg2SiO4); bru = brucite (Mg(OH)2); atg = antigorite (Mg3Si2O5(OH)4, di = diopside (CaMgSi2O6); tr = tremolite (Ca2Mg5Si8O22(OH)2); tlc= talc (Mg3Si4O10(OH)2); mgs = magnesite (MgCO3); dol = dolomite (MgCa(CO3)2); and qtz = quartz (SiO2). 5 The listvenite localities presented in Table 1-1 document a stepwise transition from peridotite to listvenite, starting with the serpentinization of peridotite (A1), the partial carbonation of serpentinite to form ophicarbonate (A2), an intermediary assemblage of soapstone (A3) and the fully carbonated listvenite (A4). Serpentinite is typically distal to listvenite and comprises lizardite and chrysotile with relict olivine and minor magnesite. Ophicarbonate is a partially carbonated serpentinite, ranging from proximal to distal to listvenite and is comprised of serpentine and magnesite ± talc. Both Beinlich et al. (2012) and Hansen and Dipple (2005) describe a soapstone phase composed of magnesite and talc and generally lacking serpentine minerals and quartz. Where serpentine minerals do occur in soapstones, it is as relict needles within magnesite and talc grains, indicative of the prograde replacement of antigorite by talc and magnesite (Beinlich et al., 2012). A transitional assemblage comprised of talc intergrown with serpentine minerals is present in Oman; however, a soapstone assemblage is lacking. Soapstone occurs at higher-temperature localities in Oman (Wadi Abyad), unrelated to the carbonating system at Wadi Mansah (Falk and Keleman, 2015; Figure 1-3). In reference to the chemical reactions presented above, all three authors have the same equation for soapstone formation via CO2 addition to serpentine (R2). Additionally, all three authors present the same equation for the formation of the listvenite by adding CO2 to talc (R3). Falk and Keleman (2015) provide an equation for the direct formation of listvenite from serpentine minerals (R4), in addition to an equation for the decarbonation of peridotite (R5), suggesting that the serpentinized and carbonated assemblages in Oman record multiple pulses of fluid with variable amounts of CO2. Beinlich (2012) accounts for the presence of dolomite after diopside and tremolite at Linnejavri (R2b; R2c); however, no author has accounted for the addition of Ca to the carbonating system. Falk and Keleman (2015) highlighted that dolomite is a major component in over 70% of listvenite samples, with CaO concentration ranging from <1 to 30 wt.%. The higher concentrations of Ca are not accounted for by protolith heterogeneity, with the Ca concentration in Oman dunite typically < 0.5% and <1% in harzburgite (Godard et al., 2000; Hanghøj et al., 2010). These large Ca gains are likely to have played an important role in the carbonation process and suggest CO2 from calcite-rich source rocks (Falk and Kelemen, 2015). 6 1.3 Volume expansion and reaction driven cracking In addition to the chemical reactions that occur during carbonation, several significant physical changes occur. Serpentinization of peridotite results in decreased density and increased magnetic susceptibility as hydrous serpentine minerals replace olivine and orthopyroxene (O’Hanley, 1992; Wicks & Whittaker, 1977). Subsequent carbonation results in increased density and solid volume, as carbonate minerals replace serpentine minerals and decreased magnetic susceptibility, as magnetite converts to hematite (Hansen et al., 2005; Tominaga et al., 2017). Overall, carbonation results in reduced density and gains in solid volume in excess of 50% relative to unaltered peridotite (Evans et al., 2020; Kelemen & Hirth, 2012). The precipitation of secondary minerals and associated volume expansion could result in clogging of pore space and armouring of surfaces by reaction products, potentially inhibiting the continuation of the carbonation reaction (Matter et al., 2011; Wilson et al., 2014). However, fully carbonated (listvenite) and hydrated (serpentinite) peridotite is observed at numerous localities globally. There is potential that a precursor for carbonation is the volume expansion associated with serpentinization (de Obeso & Kelemen, 2018a). Serpentine kernel patterns are an expansion-related feature consisting of a rim of completely serpentinized peridotite surrounding a core of partly serpentinized or un-serpentinized peridotite (Figure 1-4). Perpendicular expansion fractures commonly cut the boundary between the completely serpentinized rim and un-serpentinized core, the size and density of which are consistent with the volume change of the accompanying serpentinization (O’Hanley, 1992). Preservation of pre-existing kernel patterns is witnessed within soapstone at both the Atlin and Linnajavri listvenite localities, indicating that the intermediary soapstone assemblage forms via R2 (Table 1-1) is relatively isovolumetric (2016, Beinlich et al., 2012; Hansen and Dipple, 2005). However, the preservation of pre-existing textures in listvenite is rare, indicating that the formation of listvenite via R3 (Table 1-1) results in solid volume expansion. Listvenite displays abundant brecciation, cataclasis, shearing and faulting, suggesting that volume expansion is associated with deformation. The proximity of global listvenite occurrences to major thrust faults suggests that tectonic settings that facilitate the relief of stress built up by volume expansion may allow for the maintenance and enhancement of permeability structures. These permeability structures may be necessary to maintain the required flux of carbonate-rich 7 fluids for complete carbonation (Jamtveit et al., 2000). Alternatively, carbonation may continually generate porosity and fresh reactive surfaces. Figure 1-4. Serpentine kernel pattern at Linnajavri Norway with a soapstone reaction front replacing serpentine, after Beinlich et al. (2012). Dashed circle highlights the kernel pattern in the serpentinite (green) and soapstone (orange). Dashed orange line with arrows highlights the soapstone reaction front with orange arrows depicting direction of propagation. The kernel pattern with radial cross fractures is indicative of volume expansion during serpentinization; however, the preservation of the kernel pattern within the soapstone (grey colouration in lower half) is indicative of isovolumetric replacement by soapstone. 2 € coin centre right for scale. Macdonald and Fyfe (1985) suggested that volume changes associated with alteration reactions could generate stresses significant enough to fracture the rock. This process, known as reaction-driven cracking, has been hypothesized to be a positive feedback system that creates new fluid pathways and exposes fresh reactive surfaces at the cracks’ tip (Kelemen & Hirth, 2012). Reaction-driven cracking has been explored recently as a potential mechanism to explain the prevalence of dense, hierarchical crack networks extending to the grain scale in partially and fully serpentinized/carbonated rocks (Evans et al., 2020; Kelemen & Hirth, 2012). 8 1.4 Sources of carbonating fluids Carbonation of mantle peridotite at the leading edge of subduction zones is generally attributed to alteration by carbonate-rich fluids originating from subducting oceanic crust (Bebout & Penniston-Dorland, 2016; Kawamoto et al., 2013; Kelemen & Manning, 2015). At least three viable fluid sources for listvenite formation exist in subduction zones: (1) pore waters from footwall metasediments released during compaction, (2) low-temperature metamorphic fluids released by dehydration of opal and clay minerals in footwall metasediments, and (3) higher temperature metamorphic fluids released by devolatilization of the down-going slab, brought to the surface by channelized fluid flow up the subduction zone (Falk and Keleman, 2015). Field observations at Linnajavri by Beinlich et al. (2012) revealed that the extent of carbonation is greatest where hanging-wall peridotites overly carbonate-mica schists and weakest above garnet-mica schists with less carbonate material. Similarly, the Oman listvenite directly overly calcite-rich metasediments interpreted to be welded segments of down-going slabs in subduction zones (see section 1.7.2). However, peridotite carbonation can also occur via infiltration of meteoric water, such as in New Caledonia (Quesnel et al., 2013) and Wadi Dima Oman (Noël et al., 2018). Additionally, local decarbonation and reprecipitation of carbonates can occur surrounding intrusions (Ferry, 1995) or when carbonates become thermodynamically unstable in the presence of low-CO2 fluids (de Obeso & Kelemen, 2018a). Enrichments of elements common in potential source rocks, in addition to changes in carbon, oxygen and strontium isotopes, can be used to constrain potential fluid sources. Ca, CO2 and K are enriched in the Oman listvenite relative to fresh Oman peridotite (Falk & Kelemen, 2015; Godard et al., 2000; Hanghøj et al., 2010), potentially reflecting the transfer of Ca and CO2 from calcite-bearing footwall metasediments. Preliminary work by the Oman Drilling Project Science Team found that the Oman listvenite samples are enriched by up 103 times the Oman mantle concentrations of Rb and Ba, corresponding with values from the metasediments below (Obeso et al., 2018). Strontium isotope ratios (87Sr/86Sr) in listvenite measured by Falk and Keleman (2015) range from 0.7095- 0.7135, which are significantly higher than those in Cretaceous to modern seawater (Veizer et al., 1999), but correspond well with those of the metasediments, which range from 0.7061 to 0.7189. Temperatures may also be suggestive of carbonation sources. Clumped isotope analysis by Falk and Keleman (2015) yielded formation temperatures of 61-114 ℃ for listvenite and 37-9 71 ℃ for serpentine-listvenite transitional samples, corresponding with estimates of 64-171 ℃ for the underlying metasediments. The average clumped isotope temperature of 90 ±15 ℃ agrees well with petrological temperature estimates of 80-130 ℃; however, the variance of temperature estimates suggests multiple carbonation phases and recrystallization at different temperatures. The variance of temperature estimates may represent the influx of fluids from various sources via different pathways, i.e., hot mantle-derived fluids transported via high-flux conduits, such as faults and fractures, mixing with seawater-derived fluids or percolating meteoric fluids post obduction. 1.5 Thesis objectives This thesis aims to investigate processes of listvenite formation at the base of the Oman ophiolite using samples collected from hole BT1 of the Oman Drilling Project. The three specific objectives of this thesis are to: 1) Characterize the carbonated assemblages present by collecting and interpreting detailed optical and microbeam petrography, X-ray diffraction, whole-rock geochemistry, and stable carbon and oxygen isotope data. 2) Use thermodynamic phase equilibria modelling to determine the mineral reaction sequence, constrain the pressure-temperature conditions during carbonation, and constrain the mole fraction of CO2 in the carbonating fluids driving these carbonation reactions. 3) Constrain the source of the carbonating fluids and the number of carbonation events with detailed petrography, trace element geochemistry and stable carbon and oxygen isotope data. 1.6 Introduction to the Oman Drilling Project The Oman Drilling Project (OmanDP) is an international scientific research project in collaboration with Sultan Qaboos University, Ministry of Regional Municipalities and Water Resources and Public Authority of Mining, Oman. Operations are funded by ICDP, IODP, NASA, NSF, ERC, Deep Carbon Observatory, JAMSTEC, Japanese Society for the Promotion of Science, Swiss National Science Foundation, and the German Research Foundation. Scientific drilling of the Oman ophiolite aims to understand the full spectrum of processes that create and 10 modify oceanic crust and the upper mantle. Listed below are the specific scientific objectives of the Oman Drilling project: (1) Quantify the nature and timing of solid upwelling beneath a spreading ridge; (2) Quantify the nature and structural relationships of melt transport features in the shallow mantle to evaluate mechanisms that focus melt where igneous oceanic crust is formed; (3) Quantify chemical variability and deformation structures in the crust-mantle transition to determine the depth of crystallization, the nature of ductile flow, and mechanisms of melt transport; (4) Quantify hydrothermal alteration and cooling of the plutonic lower crust to determine the importance of hydrothermal convection in heat and mass transfer; (5) Characterize crosscutting igneous relationships, metamorphic mineral assemblages, and geochemical alteration to investigate processes in the dike-gabbro transition zone; (6) Quantify mass transfer from subducted sediments into overlying peridotite at the “leading edge of the mantle wedge” via petrologic and geochemical studies, with special focus on carbon cycling (BT1); (7) Study ongoing, subsurface hydration (serpentinization) and carbonate alteration of mantle peridotite, characterize the physical and chemical hydrogeology in peridotite aquifers, investigate reaction driven cracking and characterize the subsurface microbial biosphere. The objective of relevance to this thesis is number six. It is the basis for diamond drill hole BT1 (Figure 1-5), which targets hydrated and carbonated mantle peridotite at the base of the ophiolite, the basal thrust fault, and the underlying metamorphic sole. 11 Figure 1-5. Location of Oman Drill Project holes linked to targeted features in the oceanic crust (after Nicolas & Boudier, 1995). Blue represents gabbro, green for peridotite, red for metamorphic rocks and pale grey for undifferentiated ophiolitic material. This thesis focuses on samples solely from hole BT1, which drilled into carbonated peridotite at the ophiolite base and through the basal thrust before it terminated in the metasediments below. 1.7 Geological background 1.7.1 Introduction to ophiolites Ophiolites are thrust-bound sheets of oceanic lithosphere emplaced onto continental margins (Coleman, 1981). Ophiolites allow the investigation of the structure and genesis of oceanic crust with relative ease compared to in situ oceanic crust. Ophiolites form above subduction zones, providing the opportunity to investigate processes occurring at the leading edge of the mantle wedge, slab interface and down-going slab (Dilek & Furnes, 2011). The uppermost part of down-going slabs, referred to as metamorphic soles, are comprised of relatively thin (10s-1000s of m thick), highly sheared thrust sheets of sub-greenschist to granulite facies (Williams & Smyth, 1973). Although metamorphic soles represent the top of the down-going slab, the original slab that they were part of may no longer be present; the metamorphic sole can be juxtaposed against 12 the base of some ophiolites and remain welded as subduction continues beneath (Hacker et al., 1996; Hacker & Gnos, 1997; Rioux et al., 2016). Moores (1982) proposed two main groups of ophiolites: Tethyan and Cordilleran. Tethyan-type ophiolites such as the Oman-United Arab Emirates (UAE) and Troodos ophiolites were emplaced onto passive continental margins when the continent’s edge reached the subduction zone, preventing further subduction. Cordilleran-type ophiolites such as the Lachlan Orogen ophiolite in SE Australia (Spaggiari et al., 2004) and Franciscan ophiolite in California (HSÜ, 1968) were scraped off the down-going slab and emplaced as a mélange into accretionary prisms, with many of the original textures and sequences destroyed (Beccaluva et al., 2004). 1.7.2 Stratigraphy of the Oman-United Arab Emirates ophiolite The Oman-UAE ophiolite is a thrust sheet of Tethyan oceanic lithosphere emplaced onto the formerly passive continental margin of Arabia (Nicolas et al., 2000). It is 10-20 km thick, ~ 100 km wide and spans nearly 500 km, from the Dibba zone in northern UAE to the Whahiba sands southeast of Muscat (Shelton, 1984; Figure 1-6). The Oman-UAE ophiolite provides the largest and best-preserved type section of oceanic lithosphere globally (Allemann & Peters, 1972; Coleman, 1981; Glennie, 1974; Nicolas et al., 2000). It consists of upper mantle peridotite, layered and massive gabbro, sheeted dikes, pillow lavas and pelagic sediments (Coleman, 1981; Searle & Malpas, 1980) and is crosscut throughout by numerous felsic, mafic and ultramafic dikes (Cox et al., 1999; Rollinson, 2009). The ophiolite is bound by a basal thrust that separates it from the underlying metamorphic sole, consisting of sub-greenschist to granulite facies metasedimentary and metamafic rocks (Searle & Malpas, 1980). Thrust over the metamorphic sole is a series of Permian to Late Cretaceous distal to proximal passive margin successions (Searle & Malpas, 1980). Tilting of the ophiolite occurred syn to post emplacement, followed by the unconformable deposition of late Cretaceous to early Miocene transgressive shallow marine sediments above, followed by further uplift and erosion to create the present-day topography (Searle et al., 2015). 13 Figure 1-6. Simplified geological map of the Oman-UAE ophiolite and metamorphic sole (after Cox et al., 1999). The Sumail and Ibra Massifs highlighted in brown were drilled during the Oman Drilling project; see Figure 1-5 for a more detailed map of these massifs and location of drill holes. 1.7.3 Tectonic setting of the Oman-UAE ophiolite The Oman-UAE ophiolite and mountains record the opening and closure of the Neo-Tethys ocean basin (Allemann & Peters, 1972). Rifting of the Arabian plate in the Late-Permian led to the opening of the Neo-Tethys and associated passive margin sedimentation through most of the Mesozoic (Glennie, 1974). Initiation of subduction circa 104 Ma (Guilmette et al., 2018) marked the onset of ocean closure; however, the tectonic setting in which subduction initiates remains debated (Pearce et al., 1981). Numeric models suggest tectonic stresses may cause subduction 14 initiation at weak pre-existing structures such as transform faults (Shervais & Choi, 2012), while observations from modern subduction zones suggest initiation through spontaneous lithospheric gravitational collapse at spreading centres (Stern & Gerya, 2018). Lu-Hf and U-Pb geochronology of the upper and lower plate material in the Oman ophiolite illustrates that the lower plate’s initial burial occurred circa 104 Ma, predating the formation of the oceanic crust by at least 8 Ma (Guilmette et al., 2018). This time lag reveals a tectonically forced subduction initiation mechanism (Guilmette et al., 2018). Unlike other Tethyan-type ophiolites, such as the Himalayan (Corfield et al., 2001) and Alpine (Marroni & Pandolfi, 2003), the Oman-UAE ophiolite is relatively undeformed over large areas, with most tectonic deformation considered to be ridge related (Nicolas et al., 2000; Nicolas & Boudier, 1995). The ophiolite sequence forms the hanging-wall of a former subduction zone, while the metamorphic sole forms the footwall, the latter of which comprises accreted slices of the down-going slab (Searle & Malpas, 1980). Thus, the ophiolite base allows for direct examination of subduction zone geochemical processes such as serpentinization and carbonation (Kelemen & Manning, 2015). 1.7.4 Geochronology of the Oman-UAE ophiolite U-Pb zircon ages from the ophiolite and crosscutting plagiogranite dikes indicate the ophiolite crystallized over a short period from 96.5-95.5 Ma (Rioux et al., 2012). Crystallization was followed by rapid cooling below 550 ℃ over 1-2 million years (Hacker et al., 1996; Hacker & Gnos, 1997). U-Pb zircon dates indicate that metamorphism of the sole was coeval with the crystallization of the ophiolite (Rioux et al., 2016), while 40Ar/39Ar ages of mica and hornblende from the metamorphic sole constrain thrusting of the ophiolite onto Arabian continental margin between 95 and 80 Ma (Cowan et al., 2014). Pressure-temperature estimates of garnet-clinopyroxene amphibolite in the sole are consistently between 10-12 kbar (30-40km) and 700-900 ℃ (Hacker & Gnos, 1997), sufficient to drive dehydration and decarbonation reactions (Sulem & Famin, 2009). Rb-Sr ages of listvenite fuchsite obtained by Falk and Keleman (2015) loosely constrain carbonation to 97 ± 29 Ma, which in light of listvenite occurring immediately above the basal thrust in highly deformed zones, suggests carbonation is contemporaneous with thrusting of the ophiolite onto the continental margin. 15 Chapter 2: Carbonation of Peridotite at the Base of the Oman Ophiolite by Two Pulses of CO2-Bearing Fluids 2.1 Introduction Carbonation of peridotite is an important fluid-rock interaction resulting in the storage of large quantities of CO2 (Kelemen et al., 2011), changes to the physical and chemical properties of the altered rocks (Hansen et al., 2005; Tominaga et al., 2017) and provides a natural analogue to in situ carbon sequestration (Kelemen & Matter, 2008; Lackner et al., 1995; Power et al., 2013). The carbonation potential of peridotite is particularly strong due to the presence of anhydrous minerals rich in divalent metal cations needed to form carbonate minerals. Carbonate-rich fluids readily react with mafic minerals, such as olivine and pyroxene, liberating abundant Mg2+, Fe2+ and Ca2+, which subsequently combine with CO32- ions to form magnesite, dolomite and siderite. The end product of the carbonate alteration of peridotite, termed listvenite (Rose, 1837), is composed of carbonate minerals such as magnesite, dolomite and siderite, with quartz, relict chromian spinel and chromian mica (fuchsite) (Halls & Zhao, 1995). Listvenite at the base of the Oman ophiolite at Wadi Mansah is a carbonate-altered peridotite, which has been thrust over carbonate-bearing metasediments, forming a rarely observed outcrop exposure of serpentinization and carbonation in the hanging wall of a subduction zone (Falk & Kelemen, 2015; Nasir et al., 2007). Recent work on the Oman listvenite by Falk and Keleman (2015) provided mineralogical, chemical and isotopic evidence of the temperatures, timing and fluid compositions involved in carbonation. Insights from this preliminary work informed the placement of drill hole BT1 of the Oman Drilling Project into the listvenite at Wadi Mansah in 2017 (Figure 2-1). This drill hole was the first in the world to drill through the base of an ophiolite and into the underlying metamorphic sole, providing 300 m of continuous drill core. The upper 200 m of this drill core comprises variably carbonated and serpentinized peridotite, making it the longest continuous sample of carbonated peridotite ever collected and provides an ideal opportunity to study the alteration of peridotite at a range of scales. Below the peridotite lies 100 m of intensely deformed calcite-bearing metasediments and metabasalt, allowing researchers to assess the metamorphic sole’s potential as a fluid and carbonate source for the alteration of the ophiolite above. 16 This chapter presents observations from a range of carbonated lithologies and the metasediments at the base of the Oman ophiolite, using samples collected from hole BT1 of the Oman Drilling Project. Detailed optical and microbeam petrography, X-ray diffraction, whole-rock geochemistry, and stable carbon and oxygen isotope data were used to characterize the various rock types and mineral assemblages sampled. These petrographic observations are then compared with thermodynamic phase equilibria modelling to present a reaction sequence and constrain the temperature and mole fraction of CO2 in infiltrating fluids. Constraints on the potential fluid sources and evidence for at least two carbonation events are presented, with discussions on these carbonation events’ timing relative to obduction-related deformation. 2.2 Methods 2.2.1 BT1 drill site Samples used for this thesis were collected from the drill core of hole BT1 of the Oman Drill project. BT1 was drilled in March 2017 at Wadi Mansah (23°21.861’ E, 58°20.149’ N) to a depth of 300.1 m (Figure 2-1). It comprises an upper layer of alluvium (2%), ophicarbonate (8%), listvenite (56%) and the underlying metamorphic sole (34%) (Figure 2-1). 17 Figure 2-1. Simplified geological map illustrating the location of all holes drilled as part of the Oman Drilling Project, with hole BT1 highlighted by the black star (after Nicolas & Boudier, 1995). b) Simplified downhole stratigraphy of core BT1, showing the alternating bands of listvenite and carbonated serpentine (ophicarbonate) at the base of the Oman ophiolite immediately above the underlying metamorphic rocks. The yellow and blue dots indicate the approximate depth of samples collected, with core photos (c-g) denoted by black and blue dots and corresponding letters. Each core photograph is of 30 cm of drill core depicting the following lithologies: c) ophicarbonate, d) talc-ophicarbonate, e) magnesite-listvenite, f) dolomite veined listvenite, and g) metamorphic with calcite vein. 18 2.2.2 Drill site sample collection and shipboard core description Drill core from hole BT1 was delivered in split tubes to a core-processing tent adjacent to the drill rig, where the core was photographed, scanned, labelled, and boxed prior to shipment. Initial logging of petrology, alteration, veining and structures was carried out on-site. In addition, a 5 cm section of the core was sampled every 20 m for geochemical and petrological analysis prior to more detailed logging, and geochemical sampling conducted off-site. The drill core was stored at the Ministry of Regional Municipalities and Water Resources in Muscat prior to being transported to port facilities, where the core was loaded onto the Japanese research vessel, the D/V Chikyu. Detailed rock description was carried out in the laboratories onboard the Chikyu. Host rock petrology, vein mineralogy, structural features and paragenetic relationships between macroscopic features were identified and described. The visual inspection of the drill core was supported by thin section petrography and semi-quantitative XRD analysis; further details of data collected during shipboard sampling can be viewed in Table 2-1 below. 2.2.3 Thesis sample collection A total of 29 HQ (63.5 mm core diameter) quarter core samples, 9 NQ (47.6 mm core diameter) quarter core samples, 10 HQ half-slab and 2 HQ fat-slab samples were collected from hole BT1 during shipboard sampling onboard the Chikyu. These samples represent the full spectrum of rock types encountered: various colours and textures of listvenite (30 samples), ophicarbonate (11 samples), talc ophicarbonate (seven samples) and the metamorphic sole (three samples) (Appendix A.1). In addition, vein material was frequently sampled, including early and late carbonate veins, abundant red/brown carbonate-oxide veins, serpentine veins and late-stage vuggy quartz-dolomite veins. Importantly, contacts and transition zones were sampled, particularly a talc-bearing serpentinite-listvenite transition zone between 97-101 m. 19 Table 2-1. OmanDP shipboard data collectiona. Data collected Description Thin sections Petrological and microstructural analysis of about 50 thin sections. Mineralogy TS and XRD mineralogy. Geochemistry Eighty-four samples were analyzed for major and trace element geochemistry using XRF beads and pellets, in addition to CHNS volatiles. High-resolution photography High-resolution 360-degree core scan photography was undertaken on-site during drilling, and high-resolution photography of half core cut faces onboard the Chikyu. CT scans Computer tomography scans allowing for the viewing of structures in 3D throughout the drill core. Hyperspectral imaging Hyperspectral imaging was conducted on half core and Oman DP thin section billets. XRF Point data and core mapping of select sections to reveal the spatial distribution of elements. Physical properties Porosity, acoustic velocity and thermal conductivity were collected on select samples. Downhole geophysicsb Density, magnetic susceptibility, P-wave velocity, P-wave amplitude, electrical resistivity and gamma to 300 mbgl, and optical and acoustic televiewer data to 100 mbgl. a Data collected by the Oman Drilling Program Science Party during four weeks of fieldwork on-site in Oman followed by four weeks of shipboard sampling and analysis aboard the research vessel Chikyu, docked in Shimizu, Japan. b Downhole geophysics were conducted by the Oman Ministry of Water. 2.2.4 Sample preparation and geochemical analysis Samples were cut into 27 × 46 × 8 mm thin section billets using a water-lubricated diamond rock saw at the Department of Earth, Ocean and Atmospheric Sciences (EOAS), University of British Columbia. A mirror image of the thin section billet was cut, wrapped in newspaper and sent to ALS laboratories in North Vancouver, British Columbia, Canada. At ALS, the samples were mechanically crushed (>75% < 2mm) then pulverized (85% < 0.75mm) using a mortar and pestle. Following pulverization, approximately 10g of pulverized material was dissolved with four-acid digestion (HCl, HNO3, HF, HClO4). Samples were then analyzed using ICP-AES for major and volatile trace elements and ICP-MS for non-volatile trace elements. Carbon and sulphur were tested by combustion analysis and LOI by heating to 500˚C at ALS laboratories. See appendices A.5 and A.6 for geochemistry data tables. 20 2.3 Quantitative mineralogy X-ray diffraction was performed on 50 mortar and pestle pulverized pulps (Appendix A.2). An additional 24 serpentine-free pulps were spiked with 20 wt.% corundum and micronized to determine amorphous content (Appendix A.3). Samples were loaded onto a back-loading cavity mount against 400 grit silicon carbide sandpaper to reduce the preferred orientation of crystals. The XRD patterns were collected using a Brunker D8 Advance X-ray diffractometer in the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia. Patterns were collected using a Cu X-ray tube operating at 35 kV and 40 mA and a LynxEye 1D position-sensitive detector operating over a 2θ range of 3-80˚, with a step size of 0.03˚ and dwell time of 0.7 seconds per step. Qualitative identification of minerals in the XRD patterns was performed using DIFFRAC.EVA V.2 (Brunker AXS) with reference to standard patterns from the International Centre for Diffraction Data (ICDD) Powder Diffraction File databases (PDF-2) (Appendix A.4). Quantitative phase analysis via Rietveld refinement was performed on the XRD patterns with DIFFRAC.TOPAS v.5 (Brunker AXS), using the fundamental parameters approach (Cheary and Coelho, 1992). 2.4 Thermodynamic phase equilibria modelling In order to constrain pressure and temperature conditions of the observed mineral assemblages, constrain the molarity of CO2 of infiltrating fluids and evaluate the carbonation reaction sequence, T-P, T-XCO2 and P-XCO2 diagrams were calculated using Perple_X software (Connolly, 2009; v. 6.6.6; http://www.perplex.eth.ch/). Phase equilibria were modelled using a bulk geochemical composition obtained from published data of unaltered harzburgite from the Oman ophiolite (Table 2-2). Reactions were calculated in the CFMSH-CO2 system using the “build”, “vertex” and “werami” functions of Perple_X (Connolly, 1990) and the thermodynamic database hp02ver.dat (T. J. B. Holland & Powell, 1998). The CFMSH-CO2 system was chosen as it includes all the elements relevant to the carbonation of harzburgite (Ca, Fe, Mg, Si, H2O and CO2) and accounts for Fe substitution. The CFMSH-CO2 system has been used in previous publications on listvenite (Beinlich et al., 2012; Menzel et al., 2018) and builds on previous work in Oman by Falk and Kelemen (2015), who modelled using the MSH-CO2 system with an antigorite bulk composition. Cr, Al, K, S and trace elements present in accessory phases such as 21 fuchsite and relict chromite were not included to maintain simplicity and relevance to carbonation. Table 2-3 lists the solution models used, with Si, H2O and CO2 modelled as pure phases. Model output was plotted using the “pssect” function in Perple_X and the Matlab script “perplexplot”. Adobe Illustrator was used to refining the presentation of the pixelated output, which is due to the grid-based minimization of Gibbs Free Energy by Perple_X (Connolly, 2009). Table 2-2. Bulk composition of average Oman harzburgite used for thermodynamic modelling*. Component wt.% CaO 1.04 FeO 8.48 MgO 45.64 SiO2 44.83 *Data obtained from Godard et al. (2000) and Hanghøj et al. (2010). Table 2-3. Solution models used in Perple_X to account for substitution of chemical components into minerals. Mineral Perple_X code Formula Reference Clinopyroxene Cpx(HP) Na1–yCayMgxyFe(1–x)yAlySi2O6 (T. Holland & Powell, 1996) Orthopyroxene Opx(HP) [MgxFe1–x]2–yAl2ySi2–yO6 (T. Holland & Powell, 1996) Clinoamphibole cAmph(DP) Ca2(y+u+v)Nau+2(w+z) [MgxFe1–x]7–3u–2v–4(w+z)Fe3+2zAl4y+3v+2w Si8–(y+v)O22(OH)2, u+v+w+y+z≤1 (Diener et al., 2007) Tremolite* Tr Ca2Mg5xFe5(1–x)Si8O22(OH)2 - Olivine O(HP) Mg2xFe2yMn2(1–x–y)SiO4, x+y≤1 (T. J. B. Holland & Powell, 1998) Talc* T [MgxFe1–x]3–yAl2ySi4–yO10(OH)2 - Dolomite Do(HP) CaMgxFe1–x(CO3)2 (T. J. B. Holland & Powell, 1998) Magnesite M(HP) MgxFe1–xCO3 (T. J. B. Holland & Powell, 1998) Antigorite Atg(PN) Mg48xFe48(1–x)Si34O85(OH)62 - Brucite* B MgxFe1–x(OH)2 - * Ideal solution models were used for tremolite, talc and brucite. 22 2.4.1 EMPA microbeam petrography and geochemistry The fine-grained nature of both the listvenite and ophicarbonate samples limits the applicability of the petrographic microscope for the identification of mineral phases and observing textures (Striet et al., 2012). Scanning electron microscopy (SEM) and electron-microprobe analysis (EMPA) were important for determining mineralogy and mineral composition in both major and minor phases, distinguishing between different types of carbonates and amorphous phases, and observing fine-scale textural relationships. 2.4.1.1 Scanning electron microscope Polished thin sections were qualitatively analyzed using an FEI Quanta 650 large chamber Tungsten hairpin filament SEM in the Materials Electron Microscopy Lab located at the University of British Columbia. The instrument was operated with a 10 μm beam diameter and a 20 kV accelerating voltage, 50× magnification, measurement time of 100 s, and a dwell time of 5 microseconds for the backscattered electron microscope (BSE) and 64 microseconds for energy dispersive spectroscopy (EDS) element mapping. 2.4.1.2 Electron microprobe Electron-probe compositions of carbonates were obtained with a fully automated CAMECA SX-50 instrument in the Electron Microbeam & X-Ray Diffraction Facility located at the University of British Columbia (Appendix A.8). The instrument was operated in wavelength-dispersion mode with the following operating conditions: 15 kV excitation voltage; 10 nA beam current; 20 s peak count time; 10 s background count-time; and 10 µm spot diameter. Data reduction was done using the ‘PAP’ f(rZ) method (Pouchou & Pichoir, 1985), with both O and C determined by stoichiometry. Measurements that that did not fall within 2% of what is expected from stichometry were discarded. For the elements considered, the following standards, X-ray lines and crystals were used: dolomite, MgKa, TAP; calcite, CaKa, PET; rhodochrosite, MnKa, LIF; siderite, FeKa, LIF. 23 2.4.2 Stable isotopes Stable carbon and oxygen isotope analysis of 51 whole-rock (Appendix A.7) and 26 targeted vein, and matrix samples (Appendix A.10) was undertaken using a Los Gatos Research off-axis integrated cavity output spectrometer (OA-ICOS) located in the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia. The OA-ICOS uses a laser source that produces light at a suitable wavelength for interacting with CO2. The laser light enters a reflective mirrored cavity, reflecting thousands of times before exiting onto a photodetector. The long optical path (multiple kilometres) provides the opportunity for the infrared light to interact with the CO2 present, resulting in the absorption of certain wavelengths of infrared light. By changing the wavelength over which the laser operates, the concentration of different isotopologues (molecules that differ only by isotopic composition) can be measured to determine isotopic ratios, with a precision similar to Isotope Ratio Mass Spectrometry (Beinlich et al., 2017). A more detailed summary of the OA-ICOS theory and its application to carbonate minerals can be found in Baer et al. (2012) Barker et al. (2011). Samples were placed into 3.7 mL borosilicate glass vials that were sealed with butyl rubber septa. A CO2 concentration of 2000 ± 500 ppm within the vials is needed to deliver a suitable amount of CO2 to the OA-ICOS isotope analyzer. 2000 ppm can be achieved with 6 mg of calcite or the equivalent amount of CO3 ions. Quantitative XRD analysis was used to determine the carbonate concentration of various carbonates, which was used to calculate the amount of sample needed. Following sample loading and an air-tight sealing of the vial, a syringe was used to pierce the septa and deliver ~0.2 mL H3PO4 (85% pure) to liberate C and O in carbonates as CO2 gas. The vial was angled to prevent contact of the acid with the sample until the syringe was removed. The acid and sample were then mixed with a VWR analogue vortex mixer for 5 seconds, and the tube was placed in a heating rack for 1 hour at 72 °C to allow for the liberation of CO2 gas from all the carbonate material present. Analysis of the liberated CO2 gas was performed using the OA-ICOS isotope analyzer in ‘batch’ mode as per Beinlich et al., 2017. The septa of each vial were manually pierced with a hypodermic needle connected to the isotope analyzer via a sample introduction line. The sample introduction line is comprised of a series of stainless steel and perfluoroether tubes and valves connected to a vacuum for CO2 evacuation, in addition to an in-line stainless steel cold trap (-72 ℃) to freeze out water vapour, which can interfere with the absorption spectra. Upon injection of 24 CO2 gas into the measurement cell, the instrument measures isotopologue concentrations (12C16O16O, 13C16O16O, 12C16O18O ), which are then converted to isotope ratio numbers (R): R (13C) = 13C/12C and R(18O) = 18O/16O). R values were then converted to conventional δ notation (δ13CVPDB, δ18OVSMOW; Coplen, 1994) by reference to calibration lines developed using reference materials with a known δ concentration (Barker et al., 2011; Werner & Brand, 2001). Prior to sample gas injection, a series of pumping and flushing cycles using dry, CO2-free “zero gas” occurs in both the introduction line (six cycles) and instrument (two cycles) to remove the remaining CO2 gas and mitigate memory effects. Every analytical session began and ended with four analyses of the UBC-EOAS in-house BN13 calcite standard, which was also analyzed after every sixth unknown sample. Additional standards were analyzed as unknowns for quality control. Repeated analyses of the BN13 standard indicate that the measurements are accurate with a standard error of 0.6‰ (1 SE) for δ18O and 0.5‰ (1 SE) for δ13C (Barker et al., 2011). 2.5 Results 2.5.1 Overview of rock types Drill core samples were categorized into a range of carbonated lithologies, the names of which reflect the dominant mineral assemblages present at the hand sample scale. Below is a description of the various carbonated lithologies based mostly on macroscopic descriptions of drill core and samples from drill hole BT1. Figure 2-1 above contains images (c-g) of drill core bearing the lithologies described in this section. Macroscopic core description initially distinguished serpentinite from ophicarbonate; however, microtextural analysis and XRD show that all serpentine-bearing samples collected contain variable amounts of magnesite and dolomite (9–78%) and are referred to as ophicarbonate, after Trommsdorff and Evans (1977). Ophicarbonate is present in two bands, one between 80–100 m depth (upper ophicarbonate) and another between 181–186 m (lower ophicarbonate). Only the upper ophicarbonate band was sampled. Ophicarbonate comprises dark-green to black massive cryptocrystalline serpentine and magnetite intersected by abundant light-green serpentine and white-cream carbonate veins (Figure 2-1 c). The density of carbonate veining varies in the upper ophicarbonate, with carbonate-rich zones between 80.54–80.73 m, 25 81.47–83.63 m and 86.82–88.07 m. In general, the amount of carbonate veining increases adjacent to gradational contacts between ophicarbonate and listvenite. Talc-ophicarbonate (97–100 m) is a more intensely carbonated ophicarbonate assemblage that is dark to light green in colour, with patchy light green domains containing talc, magnesite and quartz in higher abundance relative to the darker green serpentine-rich zones (Figure 2-1 d). The expected soapstone assemblage (magnesite + talc) found at other localities (Beinlich et al., 2012; Hansen et al., 2005; Menzel et al., 2018) was not observed; however, talc-ophicarbonate samples contained transitional assemblages of magnesite, talc and quartz adjacent to domains of carbonated serpentine (see section 2.5.2.2). Listvenite is the dominant carbonated assemblage above 196.6 m. It is composed of a matrix of cryptocrystalline magnesite and quartz cross-cut by abundant micro and macroscopic magnesite, dolomite and quartz veining. Listvenite is generally devoid of relict serpentine or textures suggestive of a serpentinite precursor; however, abundant relict chromite grains provide evidence of an ultramafic parent rock (Falk & Kelemen, 2015). The colouration and texture of listvenite are variable and includes brecciated red and orange listvenite in the upper part of the hole, pale grey and green listvenite with centimetre-scale quartz-fuchsite intergrowths (Figure 2-1 e) between the upper and lower ophicarbonate bands, and highly sheared, dolomite-rich, red to grey listvenite (Figure 2-1 f) in the lower listvenite, immediately above the basal thrust. The basal thrust (196.6–197.1 m) comprises a shear zone spanning the base of the lower listvenite, an intervening 0.42 m of brown to grey-green fault gouge and the upper part of the underlying metamorphic sole. The metamorphic sole (197.1–300 m) comprises intercalated, strongly foliated, fine grain to micro-crystalline, dark green metabasalt and metasediments with calcite, feldspar and chlorite-rich veining throughout (Figure 2-1 g). The base of the metamorphic sole was not reached during the drilling of BT1. 2.5.2 Microtextures and mineral assemblages Variability in mineral assemblages occurs at both the macroscopic and microscopic scale, particularly in the transitional zones between ophicarbonate and listvenite. In such cases, a thin section billet-sized sample (~5 × 3 × 0.5 cm) may contain domains of fully carbonated listvenite and ophicarbonate with variable amounts of carbonation. This section presents detailed 26 petrography of the various rock types and characterizes the mineral assemblages present within each rock type at both the macro and microscopic scale. 2.5.2.1 Ophicarbonate Ophicarbonate samples show a partially carbonated serpentinite comprised of srp-mgs-dol and srp-mgs-dol-qtz assemblages with incipient carbonation most conspicuous as magnesite and dolomite veins. The carbonate concentration of the ophicarbonate varies between 9–78%, and these samples contain an average of 9 wt.% CO2 (see sections 2.5.3 and 2.5.4). The samples collected did not contain any primary olivine or pyroxene; however, abundant mesh-textured serpentine after olivine and serpentinized pyroxene minerals (bastite) suggests a harzburgite parent rock. The extent of serpentinization prior to carbonation is unclear; however, no relict olivine or orthopyroxene is present in collected drill-core samples, suggesting complete serpentinization occurred prior to or during carbonation. At least two cross-cutting serpentinization textures were identified: an earlier typically mesh-textured or interlocking serpentine, overprinted by fibrous chrysotile veins and shear veins (Figure 2-2). These chrysotile veins appear to form an important pathway for propagating carbonate veins, with magnesite veins replacing, bending towards or emanating from chrysotile veins (Figure 2-3). Cross-cutting relationships indicate at least two generations of fibrous chrysotile veins preceded at least three generations of carbonate veining (Table 2-4) in ophicarbonate samples. The first generation of serpentine veins comprises magnetite-rich serpentine, most conspicuous as the dark magnetite-rich mesh surrounding serpentine grains or sub-linear, magnetite-rich serpentine veins, visible as dark lineations and striations at the hand-sample scale (Figure 2-4). The second generation of serpentine veins is composed of continuous to discontinuous fibrous chrysotile veins and shear veins, often associated with brecciation and cataclasis (Figure 2-2). Carbonate veins frequently exploit weaknesses associated with serpentine veins, such as along the vein-wall rock contact and replacing fibres in chrysotile-rich shear veins (Figure 2-2 a). The carbonate veins include an earlier generation of antitaxial magnesite veins with a hematite centreline, overprinted by coarser grain magnesite and dolomite veins. 27 Figure 2-2. Photomicrographs of ophicarbonate textures and veining from sample 17-DZ-39-4, with XPL images on the left (a,c,e) and corresponding PPL images on the right hand (b,d,f). (a–b) Serpentine breccia with ctl shear partially replaced by mgs. (c–d) Chrysotile replacement of mesh-textured srp with overprinting magnesite veins. (e–f) Chrysotile-rich serpentine domain with abundant chromite grains. 28 Figure 2-3. Photomicrographs of ophicarbonate textures and veining from sample 17-DZ-39-4, with XPL images on the left (a,c,e) and corresponding PPL images on the right hand (b,d,f). (a–b) Aligned chrysotile-filled fractures at the terminus of mgs vein. Individual magnesite grains replacing serpentine in the matrix. (c–d) Splaying magnesite veining replacing a domain of chrysotile. (e–f) Mesh textured serpentine with bastite overprinted by magnesite veining. Magnesite partially replaces the chrysotile vein on the left. 29 Thin-section-scale SEM-EDS element maps indicate that Mg and Si distribution in the ophicarbonate matrix is relatively homogenous with cryptocrystalline to fine-grain serpentine throughout (Figure 2-4). In more carbonated samples, Mg becomes concentrated in magnesite veins, and rare blebs of quartz appear to be replacing serpentine grains adjacent to magnesite veining (Figure 2-5). Fe is hosted throughout the serpentine matrix and is most prominent in magnetite-rich serpentine veins. In carbonated domains, Fe is present in magnesite and dolomite grains, typically concentrating in the outer rim of spheroidal magnesite grains (Beinlich et al., 2019) and the centreline of antitaxial carbonate veins. Ca was usually distributed as late-stage dolomite veins that overprint magnesite veins and less frequently as grains of dolomite in the serpentine matrix, likely replacing bastite grains. 30 Figure 2-4. BSE image and EDS element maps of ophicarbonate sample 17DZ-43-5. Each image is of the entire thin section (27 × 46 mm) and is composed of a mosaic of 21 × 11 tiles. (a) BSE image. (b) Multielement map displaying an overlay of images c–f with mineral phases labelled. (c) Mg map. (d) Si map. (e) Fe map showing magneitie-rich serpentine veins. (f) Ca map displaying late dolomite veins following fractures. 31 Figure 2-5. BSE image and EDS element maps of ophicarbonate sample 17DZ-39-4. Each image is of the entire thin section (27 × 46 mm) and is composed of a mosaic of 21 × 11 tiles. (a) BSE image. (b) Multielement map displaying an overlay of images c–f with mineral phases labelled. (c) Mg map showing moderately aligned magnesite veining. (d) Si map. (e) Fe map. (f) Ca map displaying small dolomite fault-vein that truncates magnesite veins. 32 2.5.2.2 Talc-ophicarbonate Talc-ophicarbonate samples contain discrete domains of three mineral assemblages: srp-mgs-tlc, mgs-qtz-tlc and srp-mgs-qtz and have an average of 22.4 wt.% CO2. This variability in mineralogy results in a more heterogeneous distribution of Mg and Si at the thin-section scale (Figure 2-6), relative to ophicarbonate samples (Figure 2-4; Figure 2-5). Although serpentine minerals are less common than ophicarbonate rocks, the textures are identical; a mixture of mesh-textured, interpenetrating and fibrous. As for ophicarbonate samples, carbonate minerals most commonly occur as abundant magnesite and dolomite veining; however, matrix carbonation is common. Srp-mgs-tlc domains in talc ophicarbonate samples typically occur as halos adjacent to magnesite veining where talc replaces serpentine (Figure 2-7). Talc also occurs as fine-grained anastomosing talc veins, often adjacent to quartz veining (see section 2.5.2.4), and at the tips of talc ± quartz veinlets splaying off larger carbonate veins (Figure 2-7). These talc veinlets exploit permeability at grain boundaries and are associated with the replacement of serpentine with talc. The close spatial association between talc and magnesite/dolomite veining suggests talc growth, and ultimately silicification and H2O release from the matrix is driven by the consumption of Mg during vein formation. Mgs-tlc-qtz domains comprise matrix- and vein-hosted magnesite, quartz and talc and are devoid of serpentine minerals (Figure 2-8; Figure 2-9). All three minerals' grain size is highly variable from cryptocrystalline to >1 mm (Figure 2-8). Talc in mgs-tlc-qtz domains occurs intergrown with chalcedony, rimming and pseudomorphing magnesite grains (Figure 2-10) and occasionally overprinting discontinuous magnesite veins (Figure 2-11). This assemblage also occurs in shear structures with abundant anastomosing quartz veining (Figure 2-6), suggesting silica activity is an important driver of talc formation. 33 Figure 2-6. BSE Image and EDS element maps of talc-ophicarbonate sample 17DZ-44-4D. Each image is of the entire thin section (27 × 46 mm) and is composed of a mosaic of 21 × 11 tiles. (a) BSE image. (b) Multielement map displaying an overlay of images c–f with mineral phases labelled. (c) Mg map. (d) Si map showing abundant anastomosing quartz veins in shear. (e) Fe map. (f) Ca map displaying late coarse-grained dolomite veins exploiting shear fabric. 34 Figure 2-7. Photomicrographs displaying textural relationships in srp-mgs-tlc assemblages from sample 17DZ-44-2, with XPL images on left (a,c,e) and corresponding PPL images on the right (b,d,f). (a–b) Talc replacement of serpentine at tips of veinlets splaying of a larger magnesite vein. (c–d) Talc that is intergrown with magnesite veining, with traces of incipient talc growth in the serpentine matrix. (e–f) Coarse-grained talc replacing serpentine overprinted by a later stage of magnesite veining. 35 Figure 2-8. Photomicrographs displaying textural relationships in srp-mgs-tlc assemblage from sample 17DZ-44-2 (a) and mgs-tlc-qtz assemblage from sample 17DZ-44-4A (b-f). (a) Talc replacing serpentine adjacent to coarse grain mgs. Note talc halos surrounding darker Fe-rich magnesite veins. (b) Small-scale image of mgs-tlc-qtz assemblage (c) Coarse grain dolomite surrounded by mgs-tlc-qtz assemblage. (d) Small-scale image of mgs-tlc-qtz assemblage in c. (e) Coarse-grained talc that is intergrown with chalcedony and surrounded by fine-grained mgs-tlc-qtz. (f) Smaller-scale image of the mgs-tlc-qtz assemblage presented in c. 36 Figure 2-9. Photomicrographs of textures and veining displaying mgs-tlc-qtz assemblage in sample 17DZ-44-4D. (a–b) Talc- and chalcedony-rich domains adjacent to coarse-grained dolomite veins. (c–d) Close up of talc and chalcedony domain with talc grains intergrown/alternating with chalcedony veins. (e–f) A domain of talc and chalcedony ringed by quartz and magnesite veins. 37 Figure 2-10. EDS element maps and BSE image of mgs-tlc-qtz assemblage from sample 17DZ-44-4C displaying talc rimming magnesite in a quartz-rich domain. (a) Multielement map with minerals identified using a combination of EDS element ratios and optical microscopy, with red=magnesite, pink =talc, blue=quartz and green=dolomite. (b) BSE image of the same domain as for image a. (c) Mg element map. (d) Si element map (e) Ca element map. Note the presence of Mg and Si in areas of talc. AEDCBTlcTlcQtzDolDolMgsQtz38 Figure 2-11. EDS Element maps and BSE image of mgs-tlc-qtz assemblage from sample 17DZ-44-4C (C1). (a) Multielement map with minerals identified using a combination of EDS element ratios and optical microscopy, with red=magnesite, pink=talc, blue=quartz and orange=siderite/hematite. (b) BSE image of the same domain as for image a. (c) Mg element map. (d) Si element map (e) Fe element map highlighting pre. Note the presence of both Mg and Si in areas of talc. Srp-mgs-qtz domains comprise serpentine with abundant matrix-hosted magnesite and quartz (Figure 2-12). Co-existing quartz and serpentine are most conspicuous in areas of shearing and cataclasis where quartz appears to replace serpentine grains (Figure 2-12). Srp-mgs-qtz domains in shears contain abundant anastomosing quartz veins overprinting Fe-rich magnesite veining within a largely serpentine-rich matrix (Figure 2-13 and Figure 2-14). Within shears, magnesite grains are rimmed by serpentine (Figure 2-13), indicating a later stage of serpentinization, which was syn to post magnesite carbonation and likely related to tectonic activity. 39 Figure 2-12. Photomicrographs from sample 17DZ-44-2 displaying textural relationships in srp-mgs-tlc (a-d) and srp-mgs-qtz assemblages (e–f). XPL images are on left (a,c,e) and corresponding PPL images on the right (b,d,f). (a–b) Serpentine with incipient carbonation comprises round magnesite grains along veinlets, which appear to be exploiting weaknesses in pre-existing magnetite-rich serpentine veins. (c–d) Talc replacing serpentine adjacent to splaying magnesite veins with a domain of serpentine above. (e–f) Intergrown srp-mgs-qtz with relict grains of serpentine in a zone of cataclasis, overprinted by a late quartz vein. 40 Figure 2-13. BSE image and EDS Element maps of mgs-tlc-qtz and srp-mgs-qtz of sample 17DZ-44-4C. (a–b) Magnesite-rich matrix cross-cut by ferroan magnesite veins. Note quartz-rich matrix with cryptocrystalline magnesite and tlc in SW of image and dolomite rimmed by Fe-rich magnesite in NE of image. (c–d) Pervasive anastomosing quartz veining in serpentine-rich matrix cross-cut by ferroan magnesite veins. Note serpentine that is intergrown with quartz and rims magnesite grains. 41 Figure 2-14. Magnesite, dolomite and quartz veining in a mgs-tlc-qtz domain of sample 17DZ-44-4d. (a–b) dolomite vein cross-cutting qtz-tlc matrix. Note talc that is intergrown with quartz and rims Fe magnesite grain in the middle right, suggestive of late-stage replacement. (c–d) Coarse-grained dolomite vein set in a quartz and talc matrix. Note that the quartz fills fractures between dolomite grains and occurs as patches within the talc- and magnesite-rich domain in the SE. 42 2.5.2.3 Listvenite Listvenite is composed of the magnesite-dolomite-quartz mineral assemblage and contains an average of 33.9 wt.% CO2. Abundant magnesite, quartz and dolomite veins overprint discrete domains of fine-grain-grained magnesite and cryptocrystalline quartz in listvenite. Listvenite in BT1 is devoid of olivine, pyroxene and serpentine minerals but does contain relict chromite grains pointing to a peridotite precursor. Trace minerals include hematite, goethite, muscovite, chlorite and clays. Optical petrography and EDS element mapping revealed discrete magnesite and silica domains at both macro and microscopic scales, with Fe spatially coincident with magnesite and chromite (Figure 2-15; Figure 2-16). Spheroidal magnesite grains are visible in the matrix of the listvenite surrounded by cryptocrystalline quartz (Figure 2-16). Listvenite did not contain a significant enrichment in silica, except for samples containing structures such as shearing (Figure 2-15). Ca is mostly distributed in late-stage dolomite veins and less commonly within the matrix. Listvenite occurs in various colours reflecting variations in mineralogy, deformation, veining, depth and weathering. Red listvenite tends to occur above the upper ophicarbonate band and is often brecciated and sheared (Figure 2-17). The red colouration is due to the presence of hematite (typically <3%), often occurring within the centreline of antitaxial magnesite veins, breccia cement infill and blebs within cryptocrystalline quartz-rich domains of the matrix (Figure 2-16). Chalcedony occurs as void space infill, breccia cement and within breccia clasts (Figure 2-17) or as anastomosing veinlets splaying out of coarse-grained quartz veins (see section 2.5.2.4) in red listvenite above the serpentine band. Lighter pink, cream and beige coloured listvenite tends to occur immediately below the upper serpentine band and is associated with higher proportions of dolomite and less-intense carbonate veining. Grey and green listvenite also occurs between the upper and lower ophicarbonates and is characterized by conspicuous mm-scale blebs of fuchsite intergrown with quartz, set in a dark grey magnesite-rich matrix (Figure 2-18). Grey and green listvenite contains less macroscopic veining and is generally devoid of deformation, making these samples the most appropriate for investigating the matrix characteristics of the listvenite. Listvenite below the lower ophicarbonate band and through to the basal thrust is pink, red and grey in colour, rich in cataclasites and shearing and hosts large (>0.5–30 cm) macroscopic dolomite veins. The lower listvenite is generally richer in dolomite and becomes progressively more deformed toward the basal thrust. 43 Structures observed in the listvenite include shears, faults, breccia and cataclasites. Cataclasites occur as domains of rounded fine-grain fragments of listvenite, often within the matrix of breccia and along fault planes. These structures cross-cut matrix- and vein-hosted magnesite and matrix-hosted dolomite but do not cross-cut late-stage dolomite veins (Figure 2-15). Listvenite samples with conspicuous amounts of shearing, brecciation or cataclasites often contained higher abundances of quartz relative to the listvenite average, potentially due to passive enrichment of silica as magnesite mobilized elsewhere. Menzel et al. (2020) provide further detail on the characteristics of structural features in BT1 and relationships to carbonation. 44 Figure 2-15. BSE Image and element maps of listvenite sample 17DZ-38-3. This sample has been sheared and is enriched in quartz (33%) relative to the average concentration of listvenite (18%). Each image is of the entire thin section (27 × 46 mm) and is composed of a mosaic of 21 × 11 tiles. (a) BSE Image. (b) EDS multielement map displaying an overlay of images c–f with mineral phases labelled. (c) Mg map showing sheared magnesite. (d) Si map showing a late generation of quartz veins cross-cutting the shear fabric. (e) Fe map. (f) Ca map displaying undeformed dolomite veins that cross-cut both the shear fabric and late-quartz veins. 45 Figure 2-16. EDS Element maps and BSE image of magnesite-listvenite sample 17DZ-26-2 (C3). (a) Multielement map with minerals identified using a combination of EDS element ratios and optical microscopy, with red=magnesite, blue=quartz and orange=siderite/hematite. (b) BSE image of the same domain as for image a. (c) Mg element map. (d) Si element map (e) Fe element map. 46 Figure 2-17 Photomicrographs of brecciated red listvenite from sample 17DZ-17-4. (a–b) Angular breccia clast, composed of previously brecciated chalcedony-rich listvenite, set in a hematite-rich fine-grained magnesite matrix. (c–d) fine-grained magnesite with chalcedony cross-cut by magnesite veins. (e–f) Rounded to angular breccia clasts set in a hematite-rich fine-grained magnesite matrix cut by antitaxial magnesite-hematite veins. 47 Figure 2-18. Photomicrographs of grey and green listvenite from sample 17DZ-63-3. (a) Coarse, round magnesite grains intergrown with fine-grained to cryptocrystalline quartz. (b) Fuchsite intergrown with quartz set in coarse-grained magnesite intergrown with cryptocrystalline quartz. (c) Coarse-grained magnesite with fine-grained quartz. (d) Coarse-grained magnesite and antitaxial magnesite intergrown with cryptocrystalline quartz and fuchsite. 48 2.5.2.4 Carbonates and veining SEM-EDS element mapping and electron microprobe analysis reveal carbonates in ophicarbonate, talc-ophicarbonate and listvenite samples are composed almost entirely of ferroan magnesite and dolomite. The microprobe did not detect calcite; however, whole-rock XRD analysis indicates traces are present in dolomite rich samples (see section 2.3). Microprobe compositions of magnesite in listvenite and ophicarbonate rocks are very similar; however, dolomite in listvenite is slightly more Fe and Ca-rich relative to ophicarbonate (Figure 2-19; Appendix A.8). Magnesite in both ophicarbonate and listvenite rocks are identical in composition, while magnesite in talc ophicarbonate rocks displays greater variability in Fe and Ca relative to magnesite in listvenite and ophicarbonate (Figure 2-19). Matrix hosted magnesite grains range in size from crypto-crystalline to <100 um, are often spheroidal in shape, frequently display Fe zonation and are set within a cryptocrystalline quartz matrix (Figure 2-16). Matrix carbonates tend to be inconspicuous, often being obscured by abundant carbonate veining, brecciation and development of mylonitic fabrics. Four generations of magnesite veining were identified, with anastomosing microcrystalline-sub mm antitaxial magnesite veins with a hematite-goethite rich centreline being the most prominent (Table 2-4; Figure 2-20). These antitaxial veins are frequently overprinted by coarser-grained, microcrystalline to macroscopic, branching magnesite and magnesite-quartz veins (Figure 2-20). Dolomite occurs as late-stage vuggy veins, coarse-grained veins often overprinting magnesite and quartz and as vein fragments in breccias. Dolomite veining frequently overprints deformation structures such as shearing and cataclasites (Figure 2-15). However, in the lower listvenite, samples with a dolomite-rich matrix are observed to be sheared, suggestive of a reactivation of the basal thrust syn to post dolomite carbonation. 49 Table 2-4. Summary of vein types from oldest to youngest in serpentinite and listvenite above the basal thrust*. Paragenetic Sequence Host Lithologies Vein Type Mineralogy Features 1 Ophicarbonate Serpentine mesh serpentine, magnetite typically black mesh texture 2 Ophicarbonate Serpentine veins serpentine with minor carbonate green to white, continuous to discontinuous 3 Ophicarbonate and Listvenite Carbonate- oxide magnesite, hematite, goethite anastomosing net veins, hem centre-line, antitaxial magnesite often deformed 4 Ophicarbonate and Listvenite Carbonate magnesite with minor quartz grey to white, continuous to discontinuous 5 Listvenite Carbonate- quartz magnesite, chalcedony, quartz thick late veins, which can have growth textures 6 Listvenite Late carbonate dolomite and/or magnesite Sparry dolomite, yellow magnesite, often vuggy * Sequence determined by analysis of cross-cutting relationships between veins at both the macro and microscopic scale, with analysis conducted during shipboard logging on the Chikyu by the Oman Drilling Project Science Party. 50 Figure 2-19. Composition of carbonate grains in different rock types. Note clustering of data reveals two carbonate compositions: magnesite and dolomite. Two smaller ternary diagrams are close-ups of clustered data displaying slight variations in carbonate composition between rock type. 51 Figure 2-20. Cross-polarized photomicrographs of vein types encountered. (a) 43-5 magnesite vein cross-cutting magnetite-rich veins in serpentine. (b) 17DZ-43-5 discontinuous chrysotile veining overprinted by antitaxial magnesite-hematite veins at the base of the image. (c) 17DZ-44-2B anastomosing and branching talc veins adjacent to coarse-grained quartz vein, both overprinted by later magnesite veining. (d) 17DZ-38-3 composite antitaxial magnesite-hematite vein overprinted by quartz veining. (e) 17DZ-38-3 magnesite veins overprinted by quartz vein with veinlets of chalcedony splaying from central quartz vein. (f) 17DZ-26-2 macroscopic composite coarse-grained quartz-carbonate vein. 52 2.5.3 Whole-rock quantitative mineralogy Forty-nine, thin-section-billet-sized samples were categorized into mineral assemblages based on mineralogical composition obtained from XRD analysis. From least to most carbonated these assemblages are: ophicarbonate (srp-mgs-dol ± qtz), talc ophicarbonate (srp-mgs-dol-tlc-qtz), magnesite-listvenite (mgs-dol-qtz), dolomite-listvenite (dol-mgs-qtz). Table 2-5 outlines the average abundance of minerals encountered in each category, including the metasediments (greenschist facies) below the basal thrust. Ophicarbonate samples contain an average of 25% carbonate minerals, talc ophicarbonate 48%, magnesite-listvenite 81%, dolomite-listvenite 88% and the metamorphic sole 12% (Table 2-5). Ophicarbonate samples contain 15–81% serpentine in addition to variable amounts of magnesite (5–53%) and dolomite (0–25%), with the relative proportion of serpentine decreasing as carbonates increased. Samples adjacent to the listvenite contacts contain substantially higher amounts of carbonate material, mostly in the form of magnesite veining, without significant increases in quartz. Minor amounts of quartz (0–3%) occur in all ophicarbonate samples, except for a heavily veined sample containing 11% quartz. Talc ophicarbonate samples contain 13–52% serpentine and 8–21% talc, with no clear relationship between the abundance of talc and other mineralogical constituents. Relative to ophicarbonate samples, the abundance of quartz increases (1–9%), suggestive of co-existing quartz and serpentine. However, detailed petrography described in section 2.5.2 revealed that quartz in ophicarbonate rocks mostly occurs as veins or intergrown with talc in talc-listvenite rocks in domains that are devoid of serpentine. Listvenite is devoid of serpentine minerals and comprises 50–88% magnesite, 0–33% dolomite and 8–33% quartz. Magnesite-listvenite and dolomite-listvenite were distinguished based on samples containing >50% of each type of carbonate. Magnesite-listvenite from the upper listvenite (above 80.28 m) contains a higher abundance of quartz relative to magnesite-listvenite from the lower listvenite (100.23–196.56 m). The lower listvenite has over twice the average dolomite concentration of the upper listvenite (4 vs. 10% dolomite), accompanied by a similar decrease in quartz (21 vs. 14% quartz, for upper and lower listvenite, respectively). Magnesite-rich listvenite tends to have more quartz relative to dolomite-rich listvenite, likely due to the majority of dolomite being vein hosted, diluting the quartz abundance. Although Cr-muscovite (fuchsite) is readily identifiable in listvenite hand samples due to its conspicuous green colouration, it was only identified by XRD in one sample containing 4% fuchsite. 53 The metasediments below the basal thrust contain a greenschist facies assemblage composed of 9–42% muscovite, 3–10% clinochlore, 5–13% albite, 11–42% epidote and 0–11% laumontite. The main carbonate in the metasediments is calcite (1–22%) with trace magnesite and dolomite. Calcite occurs in veins intergrown with albite and chlorite and within the matrix of thinly laminated metasediments. Table 2-5. Summary of whole-rock quantitative mineralogy obtained using XRD and Rietveld refinement*. Location Mineral Magnesite Listvenite Dolomite Listvenite Talc Ophicarbonate Ophicarbonate Metamorphic Above Fault Magnesite 70.3 10.0 41.2 17.6 0.8 Dolomite 9.9 76.0 6.5 6.8 0.5 Calcite 0.1 1.0 0.0 0.0 9.7 Talc 0.0 0.0 14.3 0.0 0.0 Lizardite 0.0 0.0 31.6 63.5 0.0 Quartz 17.6 8.0 5.2 2.1 3.0 Hematite 2.0 2.0 0.0 0.2 1.6 Magnetite 0.0 0.0 1.1 9.8 0.0 Baryte 0.0 3.0$ 0.0 0.0 0.0 Below Fault Muscovite 0.2 0.0 0.0 0.0 20.4 Clinochlore 0.0 0.0 0.0 0.0 7.2 Actinolite 0.0 0.0 0.0 0.0 9.2 Albite 0.0 0.0 0.0 0.0 20.9 Epidote 0.0 0.0 0.0 0.0 22.9 Laumontite 0.0 0.0 0.0 0.0 3.8 * Values represent category averages with samples grouped based on mineralogy; see appendices A.2 and A.3 for individual sample data. The limit of detection for individual samples is ~0.5%, with a measurement precision of ± 2%. $ One sample with 15% vein hosted baryte. # <0.5% muscovite as fuchsite common in listvenite samples, one sample contained 4%. 54 2.5.4 Whole-rock geochemistry 2.5.4.1 Major elements The average major element compositions of each lithology are presented below in Table 2-6. Less-altered ophicarbonate samples approximate the compositions and element ratios of average unaltered Oman peridotites (Godard, et al., 2000; Hanghøj et al., 2010) (Figure 2-21). The average compositions of listvenite samples also mirror that of the Oman peridotites; however, there is significantly more variability than for ophicarbonate samples (Figure 2-21). A clear trend in Mg and Si dilution is visible with progressive carbonation, as the relative amounts of these elements decrease with the addition of CO2 (Table 2-6). An inverse correlation between Si and Mg and Ca exists, with the most Si-depleted samples higher in Mg and Ca (Figure 2-21). Enrichments in both Ca and Mg correspond with a proportionate decrease in Si, indicative of the local mobilization of elements and variable amounts of quartz, magnesite and dolomite veining (Figure 2-21). The Si/Mg ratio of dolomite-rich listvenite is lower than the Oman harzburgite, and the Si/Mg ratio of all samples collected becomes more variable with increasing Ca addition (Figure 2-22). Fe concentrations in ophicarbonate samples correspond with that of Oman Harzburgite, with increasing variability when dolomite is present. The Fe concentration in listvenite remains within the expected range of mantle peridotite, with dolomite-listvenite hosting the lowest proportion of Fe relative to Mg (Figure 2-22; Figure 2-23). Large gains in Ca were frequently observed (Figure 2-23; Figure 2-24), with Ca-rich samples typically displaying an enrichment in CO2 with depletion in Mg and Si, indicative of dolomite vein formation diluting the relative amount of matrix-hosted magnesite and quartz. The concentration of Ca above the basal-thrust strongly correlates with dolomite abundance (Figure 2-25). Progressive carbonation in ophicarbonate rocks results in a loss of approximately 2 wt.% H2O for every 1 wt.% of CO2 gained (Figure 2-22; Figure 2-23), which is expected with the conversion of serpentine minerals to magnesite and quartz. The CO2 concentration of listvenite ranges from ~22 wt.% in quartz-rich samples up to ~35 wt.% in magnesite-listvenite samples and 45 wt.% in dolomite-listvenite samples. The CO2 concentration of footwall metasediments is highly variable (~1–11 wt.%) and is mostly related to the amount of calcite-rich veining. 55 Table 2-6. Summary of major element geochemistry by rock type* (values in wt.%). Element Ophicarbonate Tlc-ophicarbonate Listvenite Metamorphic SiO2 35.23 28.73 27.07 41.10 Al2O3 0.36 0.31 0.62 15.73 FeO 6.26 5.65 5.46 10.08 CaO 1.66 2.45 6.14 12.10 MgO 36.08 33.94 24.91 3.44 Na2O 0.05 0.05 0.03 2.20 K2O 0.01 0.01 0.08 2.70 Cr2O3 0.35 0.30 0.25 0.02 TiO2 0.01 0.01 0.01 1.95 MnO 0.09 0.09 0.10 0.15 P2O5 0.01 0.01 0.01 0.39 SrO 0.01 0.02 0.02 0.04 BaO 0.02 0.01 0.40 0.03 LOI 19.60 28.10 33.70 7.53 H2O 10.34 5.71 0.11 2.57 CO2 9.26 22.39 33.92 4.96 * Values are averages of multiple samples for each rock type. See appendix A.5 for individual sample measurements. 56 Figure 2-21. Volatile-free major element ratios in Oman listvenite (filled circles) in comparison to unaltered dunite (empty triangles) and harzburgite (squares) from Godard et al. (2000) and Hanghoj et al. (2009). (a) SiO2 vs. MgO, (b) SiO2 vs. CaO, (c) MgO vs. CaO and (d) MgO vs. FeO. 57 Figure 2-22. Volatile-free (excluding CO2 and H2O) major element ratios in Oman listvenite (filled circles) in comparison to unaltered dunite (empty triangles) and harzburgite (squares) from Godard et al. (2000) and Hanghoj et al. (2009). (a) H2O vs. CO2. (b) LOI vs. Si/Mg ratio. (c) CaO vs. Si/Mg. (d) CaO vs. Mg#, where Mg# = 100 × mol Mg/(mol Mg + mol Fe2+), all FeO is assumed to be Fe2+. 58 Figure 2-23. Major element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite from the Oman Ophiolite (Godard et al., 2000; Hanghøj et al., 2010). These ratios are plotted on a log scale, where a value of one (thick black line) is identical to the average composition of the Oman harzburgite. Values above one indicate an enrichment, while values below one indicate a depletion. Each line represents the average concentration of each element for a given rock type. The Oman harzburgite range is provided as a 90% confidence interval, calculated as two standard deviations, with the maximum and minimum limited to the data's true range. See Figure 2-24 below for the range in values of each mineral assemblage. 59 Figure 2-24. Major element geochemistry of (a) ophicarbonate and talc-ophicarbonate rocks and (b) magnesite- and dolomite-listvenite rocks compared to the composition of fresh harzburgite from the Oman ophiolite (Godard et al., 2000; Hanghøj et al., 2010). These ratios are plotted on a log scale, where a value of one (thick black line) is identical to the average composition of the Oman harzburgite. Values above one indicate an enrichment, while values below one indicate a depletion. Each coloured patch represents the 90% confidence interval for each element's range of concentrations for a given rock type, with the maximum and minimum limited to the true range of the data. See Figure 2-23 for the average values of each mineral assemblage. 60 Figure 2-25. Comparing CaO concentration against dolomite abundance. The solid red line depicts the relationship calculated by the least-squares regression using all samples, excluding the metamorphic sole, while the dashed lines show the 95% confidence interval. Samples falling below the solid line contain dolomite with a higher Ca concentration, or small amounts of calcite, while samples above the line contain dolomite with higher amounts of Mg. At lower dolomite abundances, the precision of XRD abundance drops; however, the 95% confidence interval captures almost all samples with <5% dol. The y-intercept of 0.7167 falls within the expected ±1% precision of the XRD instrument; however, this may reflect the slightly Mg enriched dolomite observed in ophicarbonate rocks or the relative Fe concentration (Figure 2-19). 61 2.5.4.2 Trace elements Both ophicarbonate and listvenite assemblages are enriched in large-ion-lithophile elements (Ba, Cs, Rb, Sr and Pb) and some high field-strength elements (U and Ta). These trace elements are enriched to approximately 100-times the concentration of unaltered Oman harzburgite (Godard et al., 2000; Hanghøj et al., 2010) and are in relatively high abundance in the metamorphic sole (Figure 2-26; Figure 2-27; Appendix A.6). As illustrated by element ratio plots, K, Cs, Rb, and Sc correlate positively with increasing Al concentration (Figure 2-28), and Cs and Rb correlate positively with potassium (Figure 2-29), indicating that these elements have substituted into micas or adsorbed onto the surface of clays. The highest concentrations of Cs and Rb, which are positively correlated, occur in magnesite-listvenite samples that contain fuchsite (Figure 2-30). The highest concentrations of Sr occur in dolomite listvenite samples. Ca-poor dolomite-listvenite samples have Sr concentrations overlapping with the Oman harzburgite. However, Sr and Ca are positively correlated, with dolomite-rich samples having Sr concentrations two orders of magnitude higher than the average Oman Harzburgite (Figure 2-29). Conclusions regarding light- and heavy-rare-earth elements are difficult to make as the limit of detection in this study is above the background levels in unaltered Oman harzburgite. However, listvenite appears to be enriched in light- and heavy-rare-earth elements relative to ophicarbonate samples (Figure 2-26 and Figure 2-27). This enrichment coincides with much higher levels of these elements in the metamorphic sole. In all lithologies, the concentration of siderophiles, such as Cr, Co and Ni, are equivalent to values in unaltered Oman harzburgite. Magnesite-listvenite and ophicarbonate samples have Cu concentrations equivalent to the Oman Harzburgite, while dolomite-listvenite samples are lower Cu concentration. 62 Figure 2-26. Trace element geochemistry of serpentinized and carbonated rocks compared to the composition of fresh harzburgite from the Samail Ophiolite (Godard et al., 2000; Hanghøj et al., 2010). These ratios are plotted on a log scale, where a value of one (thick black line) is identical to the average composition of the Oman harzburgite. Values above one indicate an enrichment, while values below one indicate a depletion. Each line represents the average concentration of each element for a given rock type. The Oman harzburgite range is provided as a 90% confidence interval, calculated as two standard deviations, with the maximum and minimum limited to the data's true range. See Figure 2-27 below for the range in values of each rock type. The pink dashed line illustrates the limit of detection, which is frequently above the low concentrations of light and rare earth elements in the depleted Oman peridotites. 63 Figure 2-27. Trace element geochemistry of (a) ophicarbonate and talc-ophicarbonate rocks and (b) magnesite- and dolomite-listvenite rocks compared to the composition of fresh harzburgite from the Oman ophiolite (Godard et al., 2000; Hanghøj et al., 2010). These ratios are plotted on a log scale, where a value of one (thick black line) is identical to the average composition of the Oman harzburgite. Values above one indicate an enrichment, while values below one indicate a depletion. Each coloured patch represents the 90% confidence interval for each element's range of concentrations in a given rock type, with the maximum and minimum limited to the data's true range. See Figure 2-26 for the average values of each rock type. 64 Figure 2-28. Volatile free trace element ratios with Al2O3 in serpentinized and carbonated rocks (filled circles) in comparison to unaltered dunite (empty triangles) and harzburgite (squares) from Godard et al. (2000) and Hanghoj et al. (2009). Note positive correlations of large ion lithophile elements with Al2O3 and higher abundance in the metamorphic sole. (a) K2O vs. Al2O3. (b) Sc vs. Al2O3. Note that K2O and Sc approximate that of Oman Harzburgite while correlating positively with Al. (c) Cs vs. Al2O3. (d) Rb vs. Al2O3. Note the significant enrichment in these elements relative to the Oman harzburgite, in addition to the increased abundance in magnesite-listvenite relative to other assemblages. 65 Figure 2-29. Volatile free trace element ratios with CaO and K2O in serpentinized and carbonated rocks (filled circles) in comparison to unaltered dunite (empty triangles) and harzburgite (empty squares) from Godard et al. (2000) and Hanghoj et al. (2009). (a) Sr vs. CaO. Strontium displays enrichment relative to the unaltered Oman peridotite and correlates with Ca. Ophicarbonate samples with lower levels of CaO fall within the upper range of the Oman harzburgite. In comparison, listvenite with higher levels of CaO can have up to 100 times the concentration of Sr, relative to the Oman peridotite. (b) Rb vs. Cs displaying a strong positive correlation with each other and significant enrichment of Cs + Rb relative to the Oman peridotites. Note that samples with the highest concentration of Cs and Rb approximate the underlying metasediments, suggesting it is a potential source of these elements. (c) Cs vs. K2O. (d) Rb vs. K2O. Note the positive correlation of Cs and Rb with K2O, suggesting that these elements substitute for K in micas and clays. 66 Figure 2-30. Major micaceous minerals identified by spectral analysis with Cesium and Rb concentrations. Samples were categorized by the micaceous mineral generating the strongest spectral response, which was interpreted to be the most abundant. Some samples with no micas identified have elevated Cs and Rb, suggesting not all micaceous phases were detected by the instrument. Muscovite appears to be the primary host to Cs and Rb, followed by montmorillonite, the latter of which may be a weathering product of muscovite. 2.5.5 Stable carbon and oxygen isotopes Figure 2-31 and Figure 2-32 present δ13C (VPDB) and δ18O values (VSMOW) of individual samples with sample depth. Both δ13C and δ18O values are summarized by lithology in Figure 2-33. δ 13C values range from -7 in ophicarbonate to +2.6 in vein calcite from the metamorphic sole, with δ13C values of the most carbonated assemblages overlapping with values in the metasediments. δ 18O values range from +10 for magnesite veins to +26 for dolomite veins. Progressive carbonation results in clustering of samples by lithology with the following groups identified: ophicarbonate samples with the most negative δ13C values (~-7) overlap with values in mantle carbonatites (-4 to -8), while δ18O values of +15 to +20 in ophicarbonates are within the range of magnesite-listvenite and the metamorphic sole. Talc ophicarbonate samples have δ13C values of -5 to -3.5 and have approximately the same δ18O values as the ophicarbonate samples. δ 13C values of matrix magnesite approximate the whole-rock samples, while magnesite veins overlap entirely with the δ13C value of the metasediments. Some magnesite matrix samples 67 from magnesite-listvenite fall within the carbon range of talc-ophicarbonate rocks. Whole-rock magnesite-listvenite samples display greater variability in δ13C values (-4 to 0) relative to dolomite-listvenite samples (-2 to 0) and become notably differentiated in δ18O values as the relative dolomite concentration increases (see sections 2.6.3 and 2.6.5). δ13C values increase in an approximately linear fashion with increasing CO2; however, such a clear trend is not visible in δ18O (Figure 2-34). 68 Figure 2-31. δ13C values plotted against depth. Error bars denote each sample measurement's standard error, calculated as the average variance of bracketing standards from known values. The scale is broken between 205 and 270 m, and the inset displays the talc ophicarbonate in greater detail. Pale background colouration denotes lithology with white for listvenite, green for ophicarbonate, yellow for talc-ophicarbonate and blue for the metamorphic rocks below the basal thrust. Circles denote whole-rock samples (wr), squares matrix (mtx) material and triangles vein material (vn). Ophicarbonate and talc ophicarbonate samples tend to have the most negative values, with carbonated assemblages approaching and overlapping with δ13C values of the metasediments below. Overall matrix samples tend to display more negative δ13C values, veins the most positive and whole-rock samples displaying intermediate values. 69 Figure 2-32. δ18O values plotted against depth. Error bars denote each sample measurement's standard error calculated as the average variance of bracketing standards from known values. Pale background colouration denotes lithology with white for listvenite, green for ophicarbonate, yellow for talc-ophicarbonate and blue for the metamorphic rocks below the basal thrust. Circles denote whole-rock samples (wr), squares matrix (mtx) material and triangles vein material (vn). Magnesite vein samples have the lowest δ18O values, while dolomite veins the highest. 70 Figure 2-33. Summary of stable carbon and oxygen isotopes of carbonates by lithology; ophicarbonate whole-rock, talc-ophicarbonate whole-rock, magnesite matrix from talc-ophicarbonate, magnesites-listvenite whole-rock, magnesite matrix from listvenite, magnesite vein from listvenite, dolomite-listvenite whole-rock, dolomite matrix from listvenite, dolomite vein from listvenite, metamorphic sole whole-rock and calcite vein from the metamorphic sole. Whole-rock samples (w.r) are pulverized thin section sized billet sized samples (Appendix A.7), while matrix (mtx) and vein (vn) samples are drilled material from targeted features, with mineralogy for all samples determined by XRD (Appendix A.9; Appendix A.10). On each box, the central mark indicates the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme data points not considered outliers, and the outliers are plotted individually using the '+' symbol. Samples were considered outliers if they are greater than q3 + w × (q3 – q1) or less than q1 – w × (q3 – q1), where w is the maximum whisker length, and q1 and q3 are the 25th and 75th percentiles of the sample data, respectively. 71 Figure 2-34. Stable carbon (δ13C; a) and oxygen (δ18O; b) isotopes vs. CO2. Note segregation of δ13C with increasing CO2 concentration. 2.5.6 Magnetite destruction Magnetite crystallization during serpentinization leads to an increase in magnetic susceptibility (O'Hanley, 1992). Generally, magnetite occurs as replacements of chromite grains and disseminated throughout the ophicarbonate matrix, with an increased abundance of disseminated magnetite associated with microfractures or late serpentine veins (Figure 2-4 and Figure 2-5). Petrographic observations show hematite occurs as disseminations and blebs throughout the listvenite matrix, rimming coarse magnesite grains, replacing chromite grains, and as a discrete centerline in magnesite-hematite antitaxial veins (Figure 2-20 and Figure 2-35). In both ophicarbonate and talc-ophicarbonate samples, the decrease of magnetite does not correspond with a proportionate increase in hematite, suggesting that carbonates incorporate Fe before hematite is formed (Figure 2-36). Furthermore, the amount of hematite present in listvenite does not account for the amount of magnetite destroyed or for the measured FeO concentration in each sample (Figure 2-36). Microprobe measurements indicate that Fe substitutes into carbonates, with magnesite grains containing 1–4% Fe and dolomite 1–9% Fe (Figure 2-19). The Fe concentration of dolomite is also related to the degree of carbonation, with the lowest Fe concentration measured in dolomite grains of ophicarbonate and the highest in dolomite grains of 72 listvenite (Figure 2-19). Hansen et al. (2005) used the relationship between listvenite formation and magnetite destruction to map carbonation reaction progress in field outcrops. Similarly, Figure 2-37 compares downhole magnetic susceptibility data from hole BT1 of the Oman drill project to hematite and magnetite abundance, with higher magnetite abundance corresponding to elevated magnetic susceptibility. However, magnetic susceptibility values were not proportional to magnetite abundance or CO2, as in Hansen et al. (2005), possibly due to the downhole survey taking spatially averaged measurements over a larger depth range, relative to the samples analyzed for mineralogy. Figure 2-35. Photomicrographs of hematite distribution surrounding a chromite grain in upper listvenite sample 17DZ-17-4. (a) a mixture of reflected and plane-polarized light to highlight hematite (orange-red-brown) and (b) standard reflected light for reference. Hematite is distributed as fine-scale disseminations in and around matrix carbonate, replacing chromite grains, and as the discrete centerline in hematite-mgs antitaxial veins (bottom left). 73 Figure 2-36. (a–b) The modal abundance of magnetite and hematite with increasing CO2 concentration of samples. Magnetite is present in the serpentine-bearing ophicarbonate rocks with modal abundances of 1–27% and, to a lesser extent, talc-ophicarbonate samples (0–6%). Hematite is generally present in listvenite samples in modal abundances of 0–5% compared to 0–27% magnetite in ophicarbonate samples. Modal abundances were determined by quantitative XRD; see section 2.3 for further details on the analytical procedure. (b-c) magnetic susceptibility with magnetite and CO2 concentration. Magnetic susceptibility obtained by downhole survey with values presented representing an average of 10 measurements spanning approximately 10 cm of drill core. The averaging was used to account for measurement variability and the potential lack of precision in depth measurements from the downhole survey. The dashed line displays the regression of Hansen et al. (2005) (-3.50544(CO2) + 61.003), which has been adjusted in this diagram for magnetic susceptibility values 104 times higher in this study. 74 Figure 2-37. Downhole magnetic susceptibility data obtained from the Oman Drilling Project Science Team plotted with magnetite and hematite abundance. Note the clustering of magnetite-rich samples between 80 and 100 m, corresponding to a serpentine band and elevated magnetic susceptibility readings (>6000). A second smaller band of serpentine is present between 181 and 186 m resulting in a spike in magnetic susceptibility (>8000); however, no samples were collected. Note the upper listvenite above (80 m) displays elevated and variable magnetic susceptibility (<500 to >2000), while the lower listvenite (100–200m) displays low and relatively stable magnetic susceptibility (<500). Below 200 m, the footwall metamorphic rocks display elevated and variable magnetic susceptibility (<500 to >3000). 0510152025300200040006000800010000120000 50 100 150 200 250 300Modal Abundance (%)Magnetic Susceptibility (M/H)Depth (mbgl)Magnetic Susceptibility Magneti te Hematite 50 per. Mov. Avg. (Magnetic Susceptibility)75 2.5.7 Expected assemblages from phase equilibria modelling Phase equilibria modelling of serpentinized harzburgite accounts for the following sequence of carbonated assemblages observed in the drill core: 1) ophicarbonate (serpentine + magnesite ± dolomite); 2) talc ophicarbonate (serpentine + magnesite + talc ± dolomite); 3) talc listvenite (quartz, talc and magnesite ± dolomite); and 4) listvenite (magnesite + quartz ± dolomite) (Figure 2-38). This sequence requires a higher concentration of CO2 at each step and generally occurs at greenschist or lower metamorphic conditions. Modelling from this study (Figure 2-38) suggests that infiltrating fluids require a relatively low minimum concentration of CO2 (<0.1%) to form listvenite at the expected pressure-temperature conditions of 1–3 kbar and 50–270 ℃ (Beinlich et al., 2019; Falk & Kelemen, 2015). Assuming an average temperature of listvenite formation at 150 ℃ (Beinlich et al., 2019), the minimum mole fraction of CO2 needed to form listvenite is approximately 1.2 x 10-3 at 1 kbar and 5 x10-4 at 2 kbar. This value is at least an order of magnitude lower than other higher-temperature (200-300 ℃) listvenite occurrences, which have calculated CO2 mole fractions of 1–8 x 10-2 at similar pressures (Beinlich et al., 2012; Menzel et al., 2018). The relatively low concentration of CO2 in infiltrating fluids necessitates a high time-integrated fluid flux for listvenite formation, which may provide part of the explanation as to why listvenite occurrences are often associated with structures that enhance permeability such as large thrust faults, shearing and brecciation (Beinlich et al., 2012; Falk & Kelemen, 2015; Hansen et al., 2005; Menzel et al., 2018). Decreasing the amount of CO2 in infiltrating fluids lowers the maximum temperature for the formation of listvenite and reduces talc-bearing assemblages' temperature range (Figure 2-39). The relatively small proportion of talc-bearing assemblages in this study, coupled with the missing soapstone assemblage, can be expected with low-temperature and low-XCO2 fluids. Figure 2-38 shows that at very low XCO2 values (<15 x 10-5) and low temperatures (<70 ℃), talc may not even form; instead, a rare assemblage of co-existing dolomite, magnesite, serpentine and quartz may form. Co-existing quartz and serpentine has been documented in previous work by Falk and Keleman (2015), and a clumped isotope temperature of 45 ℃ for a talc ophicarbonate sample from BT1 (Beinlich et al., 2019) provides further support that talc bearing lithologies did form at low temperatures relative to the listvenite above and below. However, an ophicarbonate 76 sample with a clumped isotope temperature of 227 ℃ (Beinlich et al., 2019) is likely to have a maximum XCO2 of 0.0025, which is an order of magnitude higher than the talc-bearing sample. The range of mineral assemblages present in the Oman listvenite, in addition to textural (see section 2.5.2) and isotopic (see section 2.5.5) evidence for multiple carbonation (early magnesite + late dolomite) and serpentinization (early lizardite/antigorite + late chrysotile) events suggests listvenite formation occurred under variable pressure-temperature and XCO2 conditions. Published temperature estimates from clumped isotopes vary between 45 and 270 ℃ (Beinlich et al., 2019; Falk & Kelemen, 2015). It is possible that during carbonation, pressure and temperature conditions at the base of the ophiolite varied spatially and temporally, with pulses of hot mantle-derived fluids mixing with trapped seawater and, at a later stage, carbonation-derived water, to produce carbonates at varying temperatures with variable isotopic compositions (Figure 2-43). Pressure and temperature conditions are likely to have varied post-obduction, with regional-scale tectonic stress increasing pressure gradients that may have facilitated the flow of fluids from above or the pumping of fluids from below. At a later stage, uplift and erosion of overlying material may have allowed for the percolation of meteoric fluids into the basal thrust zone, further modifying the isotopic composition of carbonates. 77 Figure 2-38. Thermodynamic phase equilibria modelling showing the pressure, temperature and mole fraction of CO2 in the infiltrating fluid (XCO2). (a) P-T diagram. Note that mineral assemblages are much more sensitive to changes in T than P. (b) P-XCO2 diagram. (c) T-XCO2 diagram (higher T and XCO2). (d) XCO2 diagram (lower T and XCO2). Fields with three minerals present represent equilibrium assemblages, while fields with four or minerals represent reaction fields, where co-existing reactants and products occur in equilibrium. Phase equilibria were calculated using Perple_X software (Connolly, 2009; v. 6.6.6; http://www.perplex.eth.ch/) in the CFMSH-CO2 system, using a bulk mineralogical composition obtained from published data of unaltered harzburgite from the Oman ophiolite (Godard et al., 2000; Hanghøj et al., 2010). Fe present was assumed to be FeO, and minor dolomite present in all assemblages was not labelled on the diagrams to simplify the model. 78 Figure 2-39. Thermodynamic phase equilibria modelling showing the cumulative modal abundance of mineral phases with changes in pressure, temperature, and XCO2. (a) Modal abundance with varying CO2 at 1 kbar and 150 ℃. (b) Modal abundance with varying CO2 at 1 kbar and 60 ℃. (c and d) modal abundance with temperature at different mole fractions of CO2. Note that as XCO2 decreases, both the minimum temperature for listvenite formation and the temperature range of talc bearing assemblages decrease. Phase equilibria were calculated using Perple_X software (Connolly, 2009; v. 6.6.6; http://www.perplex.eth.ch/) in the CFMSH-CO2 system using a bulk mineralogical composition obtained published data from unaltered harzburgite from the Oman ophiolite (Godard et al., 2000; Hanghøj et al., 2010). All Fe present was assumed to be FeO for simplification of the model. 79 2.6 Discussion 2.6.1 Formation of listvenite 2.6.1.1 Overview Detailed petrology (section 2.5.2) combined with thermodynamic modelling (section 2.5.7) have shown that carbonation in the Oman ophiolite proceeds via a series of mineral reactions, consistent with previous work on listvenite (Beinlich et al., 2012; Falk & Kelemen, 2015; Hansen et al., 2005; Menzel et al., 2018). The products of these mineral reactions are mineralogical assemblages characterized by increasing carbonate concentration at the expense of serpentine minerals, culminating in the formation of fully carbonated listvenite (mgs-qtz ± dol). Figure 2-40 presents a series of reactions that account for the carbonated assemblages present in the Oman ophiolite. Reactions R1–3 and assemblages A1–4 in Figure 2-40 correspond with the reactions by Hansen and Dipple (2005) and represent the classic sequence of serpentine, soapstone and listvenite documented at Linnejavri Norway (Beinlich et al., 2020; Beinlich et al., 2012) and the Advocate Ophiolite in Nova Scotia (Menzel et al., 2018). Reactions R4–5 and assemblage 5 correspond to the low temperature (<80 ℃) reactions presented by Falk and Keleman (2015) and provide an alternate pathway for listvenite formation and talc breakdown via an intermediary srp-mgs-qtz assemblage (Figure 2-40). An alternate pathway for listvenite formation is of particular relevance to this study as a discernable soapstone assemblage is lacking at both the hand sample and microscopic scale (beyond a couple of grains). Other studies have published sufficiently low clumped-isotope temperatures (45–75 ℃) from carbonates in talc-bearing assemblages to suggest at least some magnesite in transitional assemblages formed at low temperatures (Beinlich et al., 2019; Falk & Kelemen, 2015). Low-temperature fluids may have been a late feature associated with cooling of the system or with the cooler late-stage Ca-rich fluids that precipitated abundant dolomite (see section 2.6.4). Infiltration of low temperature and CO2-poor fluids after carbonation has the potential to convert talc into antigorite and quartz via R5 (Figure 2-40), which may account for the coexistence of serpentine and quartz in talc-bearing samples from this study. However, isotopic temperature estimates for both matrix and vein-hosted magnesite-listvenite from this study (see section 2.6.4) and others (Beinlich et al., 2019) exceed 100 ℃, which doesn’t provide support for the low-80 temperature pathway being a major driver of carbonation. Based on isotopic temperature estimates, the classic carbonation pathway with a soapstone intermediary is most likely responsible for most of the listvenite formation at Wadi Mansah. The lack of an intermediary soapstone assemblage reflects higher concentrations of CO2 in infiltrating fluids driving carbonation to completion. 81 Figure 2-40. Mineral reactions forming the various carbonated assemblages encountered at the base of the Oman ophiolite. (a) T-XCO2 diagram (see Figure 2-38 for more details) with assemblages labelled in squares and reactions labelled in circles. Fields with two minerals present are assemblages, while fields with three assemblages are reaction fields with co-existing reactants and products at equilibrium. Arrows denote reaction pathways displayed in the flow chart (Figure c). (b) list of reactions responsible for mineral transformations. (c) Flow chart illustrating reaction pathways with solid lines for prograde carbonation reactions and dashed lines for retrograde hydration reactions. Assemblages are labelled A1–5 and reactions and corresponding reaction assemblages R0–4. Assemblages in boxes represent the endpoint of the various reactions presented, while assemblages in ellipses are transitional capable of further reaction with increasing changes in pressure, temperature and mole fraction of CO2/H2O. 82 2.6.1.2 Ophicarbonate formation Ophicarbonate samples are a partially carbonated serpentinite comprised of the srp-mgs assemblage. Magnesite is formed by the reaction of brucite in serpentinized harzburgite with CO2 via reaction R1: !"($%)! + ($! → !"($" + %!$ Brucite is needed for this assemblage to form as direct carbonation of olivine is not thermodynamically favourable, and the carbonation of serpentine minerals is expected to result in either the srp-mgs-talc or srp-mgs-qtz assemblages, rather than srp-mgs (Figure 2-40). Brucite forms because olivine contains insufficient SiO2 to completely convert to serpentine and is most common in partially serpentinized dunite around olivine grains or intermixed with serpentine veins (Templeton & Ellison, 2020). Silica-rich minerals such as pyroxenes can inhibit brucite formation; however, it can still be present in harzburgite undergoing low-temperature water-rock interaction (Alt et al., 2007). In such cases, olivine reacts more rapidly than pyroxene and the relatively low silica activity needed to form brucite is maintained. In a fully serpentinized peridotite, approximately 5-20% brucite is expected, with the greatest abundance forming at low water-rock ratios (Frost et al., 2013). All serpentinite samples contained magnesite and dolomite in amounts corresponding to expected brucite concentrations and are completely devoid of relict brucite, mirroring the observations of Hansen and Dipple (2005) at Atlin, where no co-existing brucite and magnesite was observed. In the Advocate Ophiolite, incipient carbonation occurs in brucite-bearing magnetite veins defining mesh-textured lizardite (Menzel et al., 2018). Mesh textures are generally attributed to the serpentinization of olivine grains (Viti & Mellini, 1998), and brucite was likely present in magnetite-rich veins prior to carbonation at Wadi Mansah. The extent of serpentinization prior to carbonation is unclear; however, no relict olivine or orthopyroxene is present in collected drill core samples, suggesting complete serpentinization occurred prior to or during carbonation. Falk & Kelemen (2015) previously observed partially serpentinized harzburgite with abundant relict olivine in surface samples from the same location, suggesting a secondary serpentinization event may have occurred with carbonation in drill hole BT1. Results from this study show at least two serpentinization events occurred prior to carbonation: an earlier typically mesh-textured or interlocking serpentine followed by fibrous chrysotile veins and shear veins (Figure 2-2). It is likely that chrysotile veining formed higher-permeability pathways for CO2-bearing fluids and/or contained higher concentrations of brucite, 83 similar to other localities in Oman such as Wadi Dima (Noël et al., 2018) Wadi Fins (de Obeso & Kelemen, 2020), where serpentinization occurred as a precursor to carbonation. The majority of carbonation in the ophicarbonate samples occurs as branching carbonate veins, with matrix-hosted magnesite only witnessed in the more carbonated talc-ophicarbonate samples (Figure 2-12) and listvenite (Figure 2-16). However, intergrown antigorite and magnesite (Falk & Kelemen, 2015) and spheroidal magnesite hosted in ophicarbonate (Beinlich et al., 2019) are documented at Wadi Mansah. The abundance of branching hierarchical veins in ophicarbonate has been linked to the process of reaction-driven cracking (Kelemen et al., 2018). During reaction-driven cracking, volume changes associated with carbonation can generate stresses significant enough to fracture the host rock, forming new fluid pathways and fresh reactive surfaces at the tips of veins and fractures (Evans et al., 2020; Kelemen & Hirth, 2012; Macdonald & Fyfe, 1985). If the carbonation system was volume limited, carbonation would eventually cease due to armouring of reactive surfaces and clogging of pore space (Evans et al., 2020). However, carbonation of ophicarbonate occurs in quantities greater than the 2.68 ± 1.02% porosity present (Beinlich et al., 2019), and the amount of carbonate material present in ophicarbonate is a direct reflection of the abundance of veining. Quantitative XRD results show that magnetite formed during serpentinization, still present in ophicarbonate samples, is lost during listvenite formation (Figure 2-36). Carbonates initially incorporate Fe from magnetite breakdown, with only traces of hematite present in ophicarbonate (see section 2.5.6). Thermodynamic modelling indicates that magnetite is destroyed with carbonation of serpentine in the ophicarbonate assemblage, being completely replaced by hematite before talc appears (Figure 2-41). The following simplified equation can describe the conversion of magnetite to hematite and siderite in the presence of CO2: *+"$# + ($! → *+!$" + *+($" It should be noted that the above equation is a simplification of the process and equal volumes of hematite and Fe carbonate are not present in ophicarbonate or listvenite rocks. Quantitative XRD and microprobe results from this study indicate that most Fe present in listvenite has partitioned into carbonates (see section 2.5.6). 84 Figure 2-41. Thermodynamic phase equilibria modelling illustrating the oxidation state of Fe below 200 ℃ in equilibrium with an excess of low-CO2 fluid. Stars indicate the fields in which the mineral assemblages are present and colour-coded by lithology; green for ophicarbonate, gold for talc-ophicarbonate and red-brown for listvenite. All carbonate was assumed to be magnesite to simplify the model. Fields with three minerals present represent equilibrium assemblages, while fields with four or minerals represent reaction fields, where co-existing reactants and products occur in equilibrium. The red double-sided arrow highlights the reaction field for the conversion of magnetite to hematite. Phase equilibria were calculated using Perple_X software (Connolly, 2009; v. 6.6.6; http://www.perplex.eth.ch/) in the FMSH-CO2 system using a bulk mineralogical composition obtained published data from unaltered harzburgite from the Oman ophiolite (Godard et al., 2000; Hanghøj et al., 2010). The completely serpentinized harzburgite observed in this study and by others (Beinlich et al., 2019) contrasts earlier work by Falk and Kelemen (2015), which found variable amounts of relict olivine and pyroxenes present in partially serpentinized “fresher peridotite”. Complete serpentinization of the peridotite observed in hole BT1 would necessitate a high flux of CO2-poor fluids or a sufficient amount of time to react fully with the peridotite (de Obeso & Kelemen, 2018b). Such high fluxes are likely to have occurred in a subduction zone environment (Hyndman & Peacock, 2003) but may have also occurred in zones of active shearing, faulting and cataclasis. 85 2.6.1.3 Talc-ophicarbonate formation The transitional talc-ophicarbonate rocks contain three reaction assemblages: srp-mgs-tlc, mgs-tlc-qtz and srp-mgs-qtz; however, the expected soapstone assemblage of mgs-tlc is absent. Textures in these rocks reflect reaction progress rather than equilibrium (see section 2.5.2.2), with four mineral reactions (R2–5) occurring to produce the observed reaction assemblages: R2. Carbonation of serpentine to produce talc and magnesite in the srp-mgs-tlc assemblage: 2!""./!$$($%)# + 3($! → !""./#$%&($%)! + 3!"($" + 3%!$ R3. Carbonation of talc to produce magnesite and quartz in the mgs-tlc-qtz assemblage: !""./!$$($%)# + 3($! → 3!"($" + ./$! + 2%!$ R4. Carbonation of serpentine to produce magnesite and quartz in the srp-mgs-qtz assemblage !""./!$$($%)# + 3($! → 3!"($" + 2./$! + 2%!$ R5. Hydration of talc to produce serpentine and quartz in the srp-mgs-qtz assemblage: !""./#$%&($%)! + %!$ → !""./!$$($%)# + 4./$! Although rarely observed, talc-ophicarbonate rocks provide evidence for talc being an intermediary mineral phase replacing serpentine minerals. Talc replaces serpentine grains adjacent to magnesite veining, in small amounts within the matrix adjacent to larger talc grains, and as anastomosing talc veins that often occur adjacent to quartz veins (Figure 2-7; Figure 2-20). The proximity of talc to magnesite and quartz veining may shed light on the processes resulting in matrix carbonation and quartz crystallization. Talc formation during serpentinization is related to the infiltrating fluids’ silica activity and proximity to quartz veining (Oyanagi et al., 2020). Modelling by de Obeso and Keleman (2020) shows the silica concentration of carbonating fluids increases with the onset of magnesite formation, favouring talc formation. Additionally, during incipient carbonation of olivine grains, silica-rich and Mg-poor fluids have been observed at the tip of magnesite veins, where magnesite crystallization preferentially consumes Mg in zones of sufficient fluid-flux (Peuble et al., 2018). Magnesite vein formation in the talc-ophicarbonate could result in the localized enrichment of silica via two processes: 1) the 86 scavenging of Mg from serpentine adjacent to magnesite veins, leaving behind silica-rich fluids favouring the precipitation of talc; or 2) the consumption of Mg, Ca and Fe in infiltrating fluids, leaving behind silica-rich fluids that interact with the surrounding serpentine, favouring the formation of talc. Both these processes can create talc halos surrounding magnesite veins and potentially large amounts of silica-rich CO2-poor fluids (Figure 2-42). Figure 2-42. Schematic of incipient carbonation in talc-ophicarbonate adjacent to the lower listvenite. Magnesite veins preferentially propagate through and replace late serpentine, which is typically fibrous chrysotile (ctl). Coarse grain talc replaces serpentine in halos adjacent to magnesite veins. Small talc crystals also appear in the matrix adjacent to coarse-grained talc. Silica is passively enriched in the serpentine matrix by mobilization of Mg into the growing magnesite crystals. If carbonating fluids contain dissolved serpentine, silica may be passively enriched in the fluid, resulting in the precipitation of talc ± quartz veinlets. The mgs-qtz-tlc reaction assemblage is the final mineral assemblage before listvenite formation in a prograde sequence (Figure 2-38). However, talc may also represent the initial products of retrograde reactions along the perimeter of the listvenite. Phase equilibria modelling shows that magnesite and quartz in listvenite are no longer stable with the infiltration of low-CO2 hydrous fluids and can revert to talc and serpentine (Figure 2-39). In shear zones with abundant anastomosing quartz veins, talc and serpentine occur as rims that have partially replaced magnesite (Figure 2-10; Figure 2-13), suggesting a late influx of CO2-poor fluids led to decarbonation within and adjacent to structures in talc-ophicarbonate rocks. 87 2.6.1.4 Listvenite formation Listvenite represents the end product of peridotite carbonation and contains discrete, variably sized magnesite and quartz domains, with abundant magnesite, quartz and dolomite veins. The transitional talc-ophicarbonate band between 98 and 100 m provides evidence for talc formation via R2 prior to listvenite; however, the expected soapstone (mgs-talc) assemblage is lacking. The lack of a soapstone phase is indicative of either 1) low-temperature carbonation via R4, with an intermediate srp-mgs-qtz assemblage, or 2) carbonation conditions favouring the rapid consumption of talc via R3, resulting in complete carbonation with little to no intermediary assemblages remaining. Complete carbonation of serpentinite to listvenite is thermodynamically favourable at relatively low pressures (<2 kbar), low temperatures (<150 ℃) and low molar concentrations of CO2 (<10-3) (Figure 2-38), with limited opportunity to form intermediary talc-bearing assemblages common in other higher temperature listvenite localities, such as Atlin Canada (Hansen et al., 2005) and Linnajavri Norway (Beinlich et al., 2012). Average Si/Mg ratios in listvenite approximate the Oman harzburgite, indicating that no silica or Mg has been added to the system during carbonation (Figure 2-23). However, Si/Mg ratios of individual samples typically vary between 0.5 and 1.5 (Figure 2-21; Figure 2-22), representing the small-scale mobility of Mg and silica in the system. Following the dissolution of serpentine and talc minerals, preferential precipitation of magnesite is likely to have resulted in the accumulation of silica in the remaining fluids (de Obeso & Kelemen, 2018a). This enrichment of silica in remaining fluids favours quartz precipitation in areas where Mg has been removed, generating the discrete domains of magnesite and quartz that characterize many listvenite samples. Silica-rich fluids may have also been mobile at a larger scale, with recent work by Menzel et al. (2020) finding that cataclastic deformation in the Oman listvenite is associated with higher Si/Mg ratios. The proximity of the Oman listvenite and other global occurrences to large-scale thrust faulting suggests deformation may have an important role in forming permeability and enhancing fluid flux. However, much of the conspicuous deformation overprints magnesite-listvenite (Figure 2-15) at Wadi Mansah, suggesting other factors have also contributed to permeability enhancement and fluid flux. Volume expansion during carbonation has been modelled to be more than 100% of the original rock volume (de Obeso & Kelemen, 2018a; Kelemen & Matter, 88 2008), with forces of crystallization shown to be capable of exceeding peridotite rock strength during reaction-driven cracking (Kelemen et al., 2011; Kelemen & Hirth, 2012). Such forces of crystallization have the potential to enhance permeability and generate fresh reactive surfaces at the tips of propagating veins and fractures (Evans et al., 2020), but in other instances may have the potential to collapse pre-existing porosity, particularly where shear stress is applied (Curran & Carroll, 1979; Zhu et al., 2010). Collapsing of porosity may force out the remaining silica-rich fluids into other domains locally or into veins and high-permeability structures, such as faults and shear zones, where an interplay between tectonic activity and fluid flux can occur. Petrologic evidence of this process occurring in the Oman listvenite includes the presence of late quartz veins cutting serpentine minerals in ophicarbonate samples, the silicification of shear zones (Figure 2-6; Figure 2-15), mgs-tlc-qtz domains in shear zones with textures indicative of late-stage decarbonation by silica-rich fluids (Figure 2-10) and abundant late-stage quartz veining in listvenite overprinting matrix and vein hosted magnesite (Figure 2-20). 2.6.2 Dolomite veins and structural relationships Relatively large amounts of Ca have been added at a late–stage, forming dolomite veins that cross-cut the initial magnesite-rich carbonation. It appears that the full carbonation potential of the listvenite at Wadi Mansah is realized with the formation of dolomite, with the highest levels of CO2 found in dolomite-rich samples (Figure 2-22). If Ca-bearing fluids drove the initial carbonation, primary dolomite could be expected in the matrix of listvenite and veins of ophicarbonate rocks. Alternatively, if late-stage Ca-bearing fluids dissolved magnesite and reprecipitated dolomite, replacement and dissolution textures, such as dolomite rimming and pseudomorphing magnesite, are expected. The EDS element maps reveal that all lithologies contain variable but relatively small amounts of matrix-hosted dolomite (< 5%), with some evidence of replacement of magnesite with dolomite (see section 2.5.2). Although matrix dolomite is present, most dolomite occurs as late conspicuous veins overprinting matrix and vein-hosted magnesite and often postdates deformation in the listvenite (Figure 2-15). Recent work by Menzel et al. (2020) confirms that cataclastic deformation in the Oman listvenite postdates listvenite formation, with observations of truncated clasts of listvenite set in cataclasites mirroring those presented in this study (Figure 2-17). If such deformation is assumed to be largely obduction -related (Nicolas et al., 2000), the approximate timing of two carbonation 89 events can be inferred: the first being pre-syn obduction resulting in the formation of matrix- and vein-hosted magnesite; and the second being syn-post obduction resulting in the formation of late-stage dolomite veins. Menzel et al. (2020) note that although dolomite brecciation at the base of BT1 is similar in appearance to the cataclastic brecciation of magnesite-listvenite, the cement is uniformly dolomite, lacks ground-up listvenite matrix component, and grades into dolomite vein networks. Based on these observations, Menzel et al. (2020) conclude that dolomite brecciation and veins were more likely to be due to hydrothermal fluid overpressure rather than brittle deformation due to significant amounts of strain. However, the increased abundance of dolomite with proximity to the basal thrust points to a potential link to tectonic activity. Activation of the basal thrust has the potential to have pumped large amounts of Ca-rich fluids into the listvenite system at high enough pressures to have exceeded rock strength (Sibson et al., 1975). Furthermore, localized extension or fracturing associated with the basal thrust’s activation may have enhanced permeability and accommodated the additional volume of dolomite added to the listvenite. Late reactivation of the basal thrust is likely to have been driven by regional extensional forces related to the uplift of the Jebal Akhdar and Saih Hatat domes in the late Cretaceous (Mattern & Scharf, 2018). Structures related to extension, such as normal and strike-slip faulting, can also act as fluid conduits for Ca-bearing fluids, particularly if the structures link with the allochthonous Hawasina sediments below. 90 2.6.3 Isotopes and carbonating fluid source Stable isotopes of carbon and oxygen can be viewed as a tracer for CO2 and its potential sources. If carbonate crystallization is assumed to occur in chemical and isotopic equilibrium with carbonating fluids, the isotopic composition of carbonates in listvenite can be used to constrain the composition of the carbonating fluids and, ultimately, the potential source rocks (Alice et al., 2020; Chacko & Deines, 2008; Matthews & Katz, 1977; O’Neil et al., 1969). Figure 2-43 displays the stable carbon and oxygen isotope values of the Oman listvenite, with fields representing the composition of three potential reservoirs of CO2: the mantle, oceanic water and meteoric water. Figure 2-43. Stable carbon and oxygen isotope values of carbonates labelled by lithology (symbols) and compared to other carbonates (fields). The field for meteoric and cryptocrystalline magnesite is from Quesnel et al. (2013), mantle carbonatites from Deines (2002) and marine calcite from Qing and Veizer (1994). w.r = whole-rock, mtx=mgs and vn = vein. 91 The isotopic composition of carbonates differs by mineralogy and reflects different fluid sources. The most conspicuous trend in stable isotope data in Figure 2-43 is the general increase of δ13C values with carbonation from mantle values through to values associated with marine calcite: ~-7 for the least-carbonated ophicarbonate, ~-3.5 for the transitional talc-ophicarbonate, ~ 0 in listvenite whole-rock samples and up to ~+2 in magnesite veins, representing the increased flux of carbonate-bearing fluids with higher δ13C values. δ13C values from ophicarbonate, and to a lesser extent, talc-ophicarbonate and magnesite-listvenite matrix samples, overlap with mantle-derived carbonatites (Figure 2-43), suggesting that ophicarbonate, talc-ophicarbonate and some magnesite-listvenite have been subject to a mantle-derived carbon source. Mantle derived carbon may have been sourced from CO2-rich fluids at depth that was channelled up the subduction interface into the hanging wall peridotite. Samples with the lowest values in δ13C are limited to two horizons: 1) 5 ophicarbonate samples, 81.5–89 m, δ13C -7.3 to -4.6; and 2) 5 talc-ophicarbonate samples 98–100 m, 4.1 to -4.3. Although these horizons occur in serpentine-bearing lithologies, ophicarbonate samples with greater amounts of carbonation can have more positive δ13C values due to dilution of the mantle carbon signature. In general, the relative amount of mantle-derived carbon decreases with increasing CO2 concentration of samples (Figure 2-34) and both magnesite and dolomite-listvenite reflect the marine calcite signature present in the metasediments (Figure 2-43). Carbonating fluids in veins are less likely to be in isotopic exchange with the surrounding host rock relative to fluids moving through and interacting with matrix minerals (Alice et al., 2020); as such, the isotopic composition of veins provides the closest approximation of the carbonating fluid and, ultimately, the source rock. δ13C values in magnesite veins overlap with that of calcite from the footwall metasediments, while both the δ13C and δ18O values of dolomite veins overlap with that of marine calcite (Figure 2-43). Magnesite-listvenite whole-rock samples fall approximately in between the compositions of dolomite veins and magnesite veins. The high degree of overlap between δ13C values from both magnesite and dolomite veins with calcite from the metamorphic sole provides strong evidence for the metamorphic sole being the source of fluids and carbon. 92 2.6.4 Fluid compositions Assuming that carbonate minerals formed in equilibrium with the carbonating fluids, the isotopic composition of carbonating fluids at various temperatures can be calculated using the measured carbonate compositions from this study and published temperature-dependent fractionation factors (Alice et al., 2020; Chacko & Deines, 2008; Matthews & Katz, 1977; O’Neil et al., 1969) with the following formulas: 2'(3(*+,-./0+1) ≈ 5666 78 ⍺ = ; ('3!)4" + < ('3#)4 + = where A, B, and C are constants; and 2'(3(./0+1) = 2'(3(*+,) − 2'(3(*+,-./0+1). Figure 2-44 below presents the average oxygen isotope fluid-composition (δ18O(fluid)) for magnesite, dolomite and calcite at temperatures between 50 and 450 ℃. Assuming a constant temperature of 150 ℃ across all assemblages, the δ18O(fluid) varies for each carbonate type, with magnesite veins precipitating from fluids showing a δ18O(fluid) value of ~-5, whole-rock ophicarbonate and magnesite matrix carbonates ~-1, calcite veins from the metamorphic sole ~+5, and dolomite veins ~+10. Alternatively, if carbonating fluids are assumed to be purely marine in origin (δ18O(fluid) = 0), the temperature for each carbonate also varies from ~62 ℃ for dolomite veins in listvenite, 100 ℃ for calcite veins in the metamorphic sole, 155 ℃ for matrix magnesite in listvenite and 200 ℃ for magnesite veins in listvenite. The substantial difference in fluid composition and temperature between magnesite and dolomite veins suggests these carbonates precipitated from at least two different fluids: 1) an earlier, higher-temperature carbonating fluid resulting in magnesite-rich vein and matrix carbonation associated with enrichment of K, Cs and Rb; and 2) a late lower-temperature fluid precipitating dolomite veins associated with enrichment of Ca and Sr. Temperature estimates obtained from isotopic exchange thermometry can also be compared to phase equilibria modelling to constrain the potential carbonation pathway associated with each fluid pulse. Phase equilibria modelling from this study shows that if magnesite-listvenite formed above 100 ℃, an intermediary soapstone assemblage existed and was subsequently overprinted by the listvenite assemblage via R3 (Figure 2-40). If dolomite-listvenite formed at 50–100 ℃, 93 potentially no intermediary soapstone assemblage existed, and carbonation proceeded via R4 when fluids were <80 ℃ (Figure 2-40). As most of the carbonation in all assemblages is matrix- and vein-hosted magnesite that formed above 100 ℃, the main carbonation pathway for listvenite included the formation of a soapstone assemblage. Figure 2-44. Calculated oxygen isotope composition of carbonating fluids (δ18O(fluid)). Calculations are based on δ18O values for carbonate minerals obtained from this study and published fractionation factors for magnesite (Chacko & Deines, 2008), dolomite (Matthews & Katz, 1977) and calcite (O’Neil et al., 1969). Coloured lines are averages with shaded areas surrounding coloured lines represent the 25% and 75% quartiles to indicate the range (rng) of variation amongst most samples while limiting the presentation of variability related to sampling and measurement error. Vein and matrix material were obtained by drilling and mineralogy determined by XRD. Note the δ18O(fluid) values for dolomite veins are approximately 15 ‰ higher than magnesite veins at 150–250 ℃, with the difference most pronounced at lower temperatures. 94 2.6.5 Element enrichments and fluid source The transfer of fluid-mobile elements from source rocks to the listvenite can be used in conjunction with isotopes to constrain potential fluid sources. Large amounts of Ca (Figure 2-23), Sr, Cs and Rb (Figure 2-26) have been added to both listvenite and ophicarbonate samples, compared to average Oman harzburgite values. Importantly, these elements are more concentrated in listvenite than ophicarbonate samples and occur in relatively high concentrations in the metamorphic sole. Also, of note is that Cs, Rb and δ13C are positively correlated (Figure 2-45), which links the source of these elements with that of carbon. The wide range of Cs and Rb values within listvenite is related to the availability of micas and clays for these elements to adsorb onto and substitute into (Figure 2-30); however, the strong positive correlation with δ13C suggests that the abundance of micaceous minerals may be a function of the degree of carbonation and fluid flux. No relationship between Cs, Rb and δ18O is present; however, δ18O values correlate positively with the relative abundance of dolomite (Figure 2-46). Sr is enriched in ophicarbonate and listvenite rocks, with the highest levels in dolomite-listvenite, where it substitutes for Ca in dolomite. 95 Figure 2-45. Stable carbon and oxygen isotopes plotted with volatile-free Cs and Rb concentrations. Note the positive correlation between δ13C and Cs and Rb, reflecting an increase in these elements with the relative degree of carbonation. 96 Figure 2-46. Stable carbon and oxygen isotopes vs. the relative dolomite concentration of carbonates in whole-rock (wr), vein (vn) and matrix (mtx) samples. Dolomite is displayed as a percentage of the total carbonate minerals present. Note the moderate positive correlation between δ18O and dolomite concentration in most samples. Results from this study support earlier work conducted by Falk and Keleman (2015) that attributed gains of Ca in listvenite to the dissolution of calcite in the metamorphic sole. However, Ca-bearing fluids may not have been sourced entirely from the metamorphic sole, with some contribution possible from the underlying Hawasina and Natih formations. These underlying formations display evidence of intense fluid circulation strongly associated with thrust faulting, dolomitization and cementation of fractures (Arndt et al., 2014; Callot et al., 2010; Cheary & Coelho, 1992; Phillips et al., 2006). Cretaceous calcite veins from the Natih formation, which underlies both the Oman ophiolite and Hawasina sediments, range in composition from 21.8–26.2 for δ18O and -0.8– 2.1 for δ13C (Arndt et al., 2014). δ13C values from both the metamorphic sole and dolomite veins overlap with values from the Natih formation, as does δ18O from dolomite veins. However, δ18O in the metamorphic sole is approximately 5‰ lower than calcite in the Natih formation, which may be related to diagenetic alteration or fluid evolution as carbonates precipitated. Sampling of the underlying shelf sediments was not conducted as part of the Oman drilling program as drill hole BT1 terminated in the metamorphic sole. Future work is needed to 97 evaluate the potential of carbonating fluids originating from the Hawasina formation, particularly for the late dolomite veins—this will provide valuable data to re-evaluate previous quantifications of fluid and carbon fluxes in subduction zones (Kelemen & Manning, 2015). 98 Chapter 3: Conclusions 3.1 Overview This thesis aimed to investigate processes of listvenite formation in the Oman ophiolite using samples collected from hole BT1 of the Oman Drilling Project. Serpentinization and subsequent carbonation by Ca-bearing CO2-rich fluids added an average of 33.9 wt.% CO2 to fresh harzburgite, with the CO2 stored in the form of stable magnesite and dolomite. Carbonation proceeded via a series of mineral reactions resulting in the breakdown of serpentine-group minerals and the formation of magnesite, dolomite, talc and quartz. Petrological observations and stable oxygen isotopes (δ18O) show that mineral reactions were driven by at least two pulses of CO2-bearing fluids that originated from, or interacted with, the metamorphic rocks immediately below the listvenite. Phase equilibrium modelling suggests carbonating fluids are likely to have had a minimum mole fraction of CO2 of <1x 10-3 and varied in temperature between 50 and 200 ℃ at pressures of 1–3 kbar. This thesis illustrates how mantle peridotite in the hanging-wall of subduction zones absorbs CO2, forming an important reservoir in the carbon cycle. Understanding the formation of listvenite in the Oman ophiolite provides valuable information for developing in situ carbon sequestration technologies that aim to utilize the naturally occurring carbonation processes presented in this thesis. 3.2 Objectives 3.2.1 Characterization of mineral assemblages The first objective of this thesis was to characterize the serpentinized and carbonated lithologies and identify the mineral assemblages present in BT1. Two equilibrium (ophicarbonate and listvenite) and three transitional reaction assemblages were identified: Equilibrium Assemblages 1. Ophicarbonate (serpentine + magnesite) Ophicarbonate samples are composed of partially carbonated serpentinite with an average of 9 wt.% CO2. Ophicarbonate samples are fully serpentinized with no relict olivine or pyroxene and are devoid of brucite from incipient serpentinization. Serpentine minerals occur as interlocking antigorite, mesh-textured lizardite, vein-hosted chrysotile, and bastite. Carbonation is predominantly in the form of vein-hosted magnesite and dolomite 99 with rarely observed matrix-hosted magnesite. Carbonation is associated with a later stage of chrysotile serpentinization with magnesite veins following chrysotile veins and shear veins, and incipient matrix carbonation occurring with chrysotile halos. 2. Listvenite (magnesite + quartz). Listvenite is a fully carbonated peridotite containing discrete domains of fine-grained magnesite and cryptocrystalline quartz overprinted by abundant quartz and carbonate veining. Trace minerals include chromite, hematite, goethite, muscovite, chlorite and clays. Listvenite samples have an average of 33.9 wt.% CO2, are devoid of serpentine and magnetite and frequently display sheared and brecciated textures. Cataclastic deformation that overprints initial magnesite-rich carbonation is often enriched in silica and cross-cut by late-stage dolomite veins. Transitional Reaction Assemblages Talc ophicarbonate samples are a more intensely carbonated serpentine and talc bearing lithology with an average of 22.4 wt.% CO2. Talc ophicarbonate samples contain three reaction assemblages representing two carbonation pathways; the classic carbonation pathway characterized by the breakdown of serpentine into magnesite and talc, and a low-temperature (<80 ℃) pathway characterized by the breakdown of serpentine into magnesite and quartz (see section 3.2.2). 1. serpentine + magnesite + talc Srp-mgs-tlc domains typically occur as halos adjacent to magnesite veining where talc replaces serpentine grains. Talc also occurs as fine-grained anastomosing talc veins, often adjacent to quartz veining. The close spatial association between talc and magnesite/dolomite veining suggests talc growth, and ultimately H2O release and the silicification of the matrix are driven by the consumption of Mg during vein formation. 2. magnesite + talc + quartz Mgs-tlc-qtz domains are a nearly fully carbonated assemblage comprised of matrix- and vein-hosted magnesite, quartz and talc and are devoid of serpentine minerals. Talc occurs intergrown with chalcedony, often rimming and pseudomorphing magnesite grains and occasionally overprints discontinuous magnesite veins. This assemblage also occurs in 100 shear structures with abundant anastomosing quartz veining, suggesting silica activity is a driver of talc formation. 3. serpentine + magnesite + quartz (<80 ℃) Srp-mgs-qtz domains contain intergrown serpentine and quartz with abundant matrix- and vein hosted magnesite. Within this domain, magnesite grains are rimmed by serpentine indicative of a later stage of serpentinization syn- to-post-magnesite carbonation. Co-existing quartz and serpentine were most conspicuous in shears and in cataclasites where quartz occurs as abundant anastomosing veins and appears to be replacing serpentine grains. The major element geochemical composition of all samples approximates fresh Oman harzburgite except for H2O, CO2 and variable amounts of Ca. Fluid mobile trace elements such as Cs, Rb and Sr in listvenite are enriched by at least two orders of magnitude relative to background harzburgite levels and correlate with increasing δ13C values. δ13C values increase with carbonation: from ~-7 δ13C for the least carbonated ophicarbonate, ~-3.5 δ13C for the transitional talc ophicarbonate, ~ 0 δ13C in listvenite whole-rock samples and up to ~+2 δ13C in magnesite veins, representing the increased flux of carbonate-bearing fluids with higher δ13C values. Oxygen isotopic composition does not exhibit a trend with progressive carbonation; however, a substantial difference in δ18O values between magnesite and dolomite indicates differing fluid compositions or temperatures. 3.2.2 Thermodynamic phase equilibria modelling of carbonation reactions The second objective of this thesis was to use thermodynamic phase equilibria modelling to determine the expected equilibrium mineral assemblages and the mineral reaction sequence. In addition, phase equilibria modelling was used to constrain both the pressure-temperature conditions and concentration of CO2 in the carbonating fluids during the formation of listvenite. Phase equilibria modelling reveals two potential reaction pathways between serpentinized harzburgite and fully-carbonated listvenite (mgs-qtz): 1) the classic carbonation pathway with an intermediary soapstone (mgs-tlc) assemblage; and 2) a direct low-temperature <80 ℃ pathway with no intermediary equilibrium assemblages. Both reaction pathways require a higher concentration of CO2 at each step and occur at greenschist or lower metamorphic conditions. 101 Formation of listvenite requires a relatively low concentration of CO2 (<0.1%) in the carbonating fluids (Figure 2-38) at the expected pressure-temperature conditions of 1-3 kbar and 50-200 ℃ (see section 3.2.3 below). Assuming an average temperature of 150 ℃ (matrix magnesite), the minimum mole fraction of CO2 needed to form listvenite is approximately 0.0012 at 1 kbar and 0.0005 at 2 kbar, which is at least an order of magnitude lower than other higher temperature (200-300 ℃) listvenite occurrences (Beinlich et al., 2012). The relatively low concentration of CO2 in carbonating fluids necessitates a high time-integrated fluid-flux to deliver the amount of CO2 necessary for the formation of large bodies of listvenite. The need for such high fluid-flux may explain why global listvenite occurrences are associated with structures that enhance permeability, such as large thrust faults, fracturing and brecciation. 3.2.3 Constraining the potential sources of carbonating fluids The third objective of this thesis was to constrain the source of the carbonating fluids and the number of carbonation events. Stable isotope and trace element geochemistry were used to characterize the fluid composition of vein- and matrix-hosted carbonates. The isotopic compositions of carbonating fluids at various temperatures were calculated using measured isotope compositions from this study and previously published temperature-dependent fractionation factors. If a constant temperature of 150 ℃ is assumed across all assemblages, the δ18O(fluid) varies for each carbonate type, with magnesite veins precipitating from fluids with an oxygen isotopic composition (δ18O(fluid)) of ~-5 δ18O, whole-rock ophicarbonate and magnesite matrix carbonates ~-1 δ18O, calcite veins from the metamorphic sole ~+5 δ18O, and dolomite veins ~+10 δ18O. If carbonating fluids are assumed to be purely marine in origin (δ18O(fluid) = 0), the temperature for each carbonate varies from ~62 ℃ for dolomite veins in listvenite, ~100 ℃ for calcite veins the metamorphic sole, ~155 ℃ for matrix magnesite in listvenite and ~200 ℃ for magnesite veins in listvenite. The substantial difference in fluid composition or temperature between magnesite and dolomite veins suggests these carbonates precipitated from at least two different fluids: 1) an earlier, higher-temperature carbonating fluid resulting in magnesite-rich vein and matrix carbonation that is associated with gains of K, Cs and Rb; and 2) a late lower-temperature fluid precipitating dolomite veins that are associated with gains in Ca and Sr. Negative δ13C values in ophicarbonate, talc-ophicarbonate and some magnesite matrix samples from listvenite overlap with values of mantle carbonatites. These negative values 102 suggest higher-temperature fluids responsible for forming the magnesite veins, magnesite matrix, and potentially serpentinization originated from or interacted with the mantle. The volume of magnesite precipitated during the initial carbonation phase necessitates a high flux of water and CO2, both of which are readily available in subduction-zone environments. Cross-cutting relationships between magnesite, dolomite and deformation structures, such as shearing, faulting and cataclasites, indicate that the cooler, dolomite precipitating fluids were introduced syn-post obduction. The implication of this is that carbonation continued well beyond the cessation of subduction, through to obduction of the ophiolite onto the Arabian continental margin. 3.3 Strengths and limitations of the research The data collected in this study is from the first drill hole to have ever successfully drilled through a paleo-subduction interface into the underlying footwall. All data generated will be unique to previous work on listvenite in Oman, which has relied on surface sampling. Specifically, this project has: • Provided a detailed account of carbonate alteration at the base of the Oman ophiolite that can inform future work on the remaining drill core; • Created an extensive quantitative data set comprised of mineralogy, major and trace element geochemistry, carbonate microprobe compositions and stable carbon and oxygen isotopes. This data can be used by other workers in the field, aiming to investigate carbonation processes in Oman and compare this data to other localities; • Reconciled detailed petrography and a broad range of quantitative data with thermodynamic modelling to bring together a geological story for the formation of listvenite at Wadi Mansah that supports and builds upon previous work by Falk and Kelemen (2015); • Highlighted the importance of differentiating between carbonation that occurs during subduction from that which occurs during thrusting onto the continental margin, which is of significance to those studying carbon fluxes in subduction zones; • Supported previous thermodynamic phase equilibria modelling on listvenite conducted by Beinlich et al. (2012), Falk and Keleman (2015), de Obeso and Kelemen (2018) and Menzel et al. (2018), helping to constrain the most likely conditions that result in the full carbonation of peridotite; and 103 • Provided information that can inform the development of in situ carbon sequestration technologies that aim to utilize the naturally occurring carbonation reactions presented in this thesis. Observations warranting future research include the potential for fluids to have originated from the Hawasina sediments, determining the relative amount of carbonation occurring within a subduction zone setting vs. on the continental margin, constraining how volume is accommodated outside of reaction-driven cracking by tectonic forces, and uncovering how much of the serpentine band is a retrograde reaction. Further questions regarding the relative timing of the mineral reactions remain, as does a definitive explanation for the lack of a conspicuous soapstone assemblage. Improvements to the data collected could involve creating a more extensive isotope data set with more detailed vein and matrix sampling, more sampling of the metasediments below to better constrain their isotopic composition, undertaking more detailed petrography of dolomite-rich listvenite immediately above the basal thrust, better constraining the timing of dolomite (potentially with isotopic dating) and more accurate trace-element geochemistry that allows for the detection of rare-earth elements at the concentrations found in depleted mantle peridotite. Ultimately, future studies using engineered systems that inject CO2 into peridotite, such as that proposed by Kelemen and Matter (2008), are needed to evaluate the suitability of the Oman-UAE ophiolite for in situ carbon sequestration. 104 Bibliography Alice, V., Pierre, L., & Daniela, R. (2020). An internally-consistent database for oxygen isotope fractionation between minerals. In Journal of petrology. 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Thin section billets which were sampled using a microdrill for mineralogy and stable carbon and oxygen isotopes have an image with labelled drill holes. Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-8-3 10.46 - 10.51 m Red brown listvenite with shear fabric defined by alignment of deformed, elongated and boudinaged <1-7mm wide pink qtz-carb veins and vein fragments dipping ~45 deg to core axis (TCA). Upper 10 mm of cut face contains abundant Fe oxide veins and a fine grain/cataclasite breccia. 116 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-13-2 22.665 - 22.715 m Red brown and grey listvenite with a prominent 5 mm wide, cream to pale yellow carb-qtz vein. Shear fabric through centre of sample defined by moderate alignment of angular to sub angular translucent carb-qtz vein fragments, boudinaged yellow dolomite veins and carb-oxide veins. 17DZ-17-4 32.56 - 32.61 m N/A Purple to red brown listvenite breccia with 2-7mm wide mgs-qtz and dol-qtz vein fragments set in a fine grain cataclasite groundmass with abundant sub mm Fe oxide veins. 17DZ-20-3 41.44 - 41.49 m N/A Dark grey listvenite with orange-brown carbonate (siderite?) pseudomorphing mesh textured srp. Matrix is overprinted by 1-2 mm red brown carb-oxide veins that frequently truncate orange and brown carbonates. Prominent 5-7mm qtz rich vein skirted by 1-2 mm of red-brown carb-oxide veins. All veining overprinted by 1-3 mm wide late quartz veining running sub parallel TCA. 117 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-24-1 49.05 - 49.1 m Dark grey to pink listvenite with weakly sheared texture defined by alignment of boudinaged pink mgs-qtz vein fragments. Trace 1-2 mm blebs of soft light green mineral (logged as tlc) throughout. Late-stage sub mm red-brown carb-oxide veins outline and overprint vein fragments. 17DZ-26-2 55.46 - 55.51 m Grey, green and brown mylonitic listvenite, with foliation dipping 30-40 deg to core axis. Prominent 5-10 mm white to yellow carb-qtz vein roughly marks the boundary to a higher porosity more weathered and oxidised zone. A 5-10 mm brown to yellow brown (goethite/limonite?) oxidation front exists between the vein and the weathered zone, where vivid green fuchsite becomes earthy orange-brown in weathered zone. 17DZ-26-3 56.67 - 56.72 m N/A Grey listvenite with white to translucent 1-2 mm carb-qtz veins overprinted by red brown 1-2 mm carb-oxide veins with mgs-oxide-fuchsite alteration selvedges. Vuggy dol-qtz-oxide veins and red brown carb-oxide veins and voids appear to be recent features related to tension cracking. 118 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-27-2 58.295 - 58.345 m Grey to red-brown listvenite pseudomorphing srp mesh texture, defined by lighter blebs of mgs-qtz and fuchsite set in a grey mgs-qtz-oxide matrix. Multiple generations of veins comprised of abundant sub mm red brown carb-oxide veins, Fe oxide filled tension gashes with visible aperture and 1-2 mm white to translucent qtz-rich veins oriented sub parallel to core axis. Chromite grains visible with fuchsite and Fe oxide rich alteration halos. 17DZ-34-1 71.5 - 71.55 m N/A Brecciated white, cream and red brown qtz rich listvenite comprised of 1-5 mm angular listvenite fragments set in qtz cement. Moderately oriented <1mm red brown veins cut by qtz rich breccia. 119 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-37-2 77.235 - 77.285 m Brecciated red brown listvenite with 1-15 mm cream boudinaged carb-qtz vein fragments set in a sheared fine grain groundmass with pervasive sub mm carb-oxide veining. Discontinuous 1-2 mm translucent qtz veining overprints sub mm carb oxide veins and are occasionally deformed. 17DZ-38-3 80.01 - 80.06 m N/A Sheared grey to red-brown listvenite with a mylonitic fabric defined by strong orientation of sub mm carb-oxide veins and vein fragments and sigmoidal tension gashes. Trace chromite grains which appear to have withstood deformation and trace amounts of a reflective mica. Late stage 1-2 mm branching dolomite veins cross-cut shear fabric. 17DZ-38-4A 81.42 - 81.47 m Red brown, light green and grey ophicarbonate with highly porous honeycomb weathering. 2-5 mm wide antigorite domains rimmed by resistant sub mm red brown carb oxide veins. One third of sample comprised of sheared grey mgs with minimal weathering. 17DZ-38-4A 120 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-38-4B 81.47 - 81.52 m Pale green to grey ophicarbonate with srp and early carb-oxide veins overprinting weathered mesh texture. Soft pale green veins (tlc?) in upper portion of sample. 17DZ-39-2 82.9 - 82.95 m Dark green sheared ophicarbonate with deformed 1-4 mm srp veins overprinted by dendritic 1-2 mm carbonate veins and two planar <1 mm red brown carb-oxide fault veins. 17DZ-39-3 84.05 - 84.09 m N/A Green to red-brown ophicarbonate with multiple generations of veins. Dark green to light green srp veins are the youngest and are overprinted by dendritic white carbonate veins. Carbonate veins often mark planes of displacement and occasionally bend towards or follow srp veins. 17DZ-38-4B 17DZ-39-2 121 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-39-4 84.645 - 84.695 m N/A Light green to red-brown ophicarbonate with multiple generations of veining. Abundant 1-3 mm pink to white branching carbonate veins overprint deformed dark red-brown carb-oxide veins, which in turn overprint earlier deformed srp veins. Black <1-3 mm blebs of relict chromite throughout. 5 mm dark green and white srp and carbonate shear zone dipping ~25 deg to core axis and ~5 sub mm faults displacing textures and veins. 17DZ-41-2 89.07 - 89.12 m No TS N/A Green, white and orange ophicarbonate comprised of dark green relics of original srp rimmed by lighter green secondary srp, overprinted by abundant 1-4 mm white-red brown carb oxide veins. 17DZ-43-1 94.26 - 94.31 m N/A Dark to light green ophicarbonate with mesh textured srp with early magnetite rich srp veins that are overprinted by <1-3 mm carbonate veins. 122 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-43-4 96.275 - 96.325 m N/A Dark green ophicarbonate with 1-3 mm dark green magnetite rich branching veins with dark green alteration halos, overprinted by abundant branching and anastomosing 1-5 mm white carbonate veins. Relict sub-mm black chromite grains with dark green alteration halos throughout. Small amounts of light blue green mineral (willemsite?) in carbonate veins running through magnetite rich srp in middle of piece. 17DZ-43-5 97.155 - 97.205 m N/A Green to black ophicarbonate with abundant white to grey branching carbonate veining overprinting srp mesh texture. Harder and more translucent carb-qtz veining and some breccia fragments associated with magnetite rich srp at the base of cut surface. 17DZ-44-1 97.33 - 97.38 m No TS N/A Green ophicarbonate with moderately oriented 1-3 mm srp and branching carbonate veins that are overprinted by late carb-qtz and qtz veins. Abundant planar sub mm carb-qtz veins oriented 45 deg to core axis overprint srp and carbonate veining, but do not appear to overprint conspicuous qtz vein in lower third of cut face. 123 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-44-2A 98.38 - 98.42 m Light green ophicarbonate with abundant carbonate and carb-qtz veining. Planar white carb-qtz sub mm vein set continues from previous sample, overprinted by branching light green to translucent grey carb-qtz vein. 17DZ-44-2B 98.63 - 98.68 m N/A Light green tlc-ophicarbonate with relict mesh texture srp overprinted by 2-5 mm transparent qtz veins and abundant dendritic and anastomosing <1-2 mm qtz-carb veins. <1-2 mm relict chromite grains throughout. Very soft light green minerals in veins may be srp or tlc mixed with carbonate. 17DZ-44-3A 98.91 - 98.96 m Light green tlc-ophicarbonate with 5-20 mm heavily veined tlc bearing zone in centre of cut face. Domains of srp overprinted by abundant white to light green carbonate veins, some of which have lighter green tlc and mgs rich alteration halos. Later composite carb-qtz veins with a translucent grey blue centreline comprised of qtz, srp and a light blue talc (XRD matches well for willemsite) running approximately 45 degrees to core axis branch into an 124 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description anastomosing complex of srp, mgs, tlc and qtz. 17DZ-44-3B 99.36 - 99.41 m Dark to light green tlc-ophicarbonate with <1 mm translucent light grey green carb-qtz vein set oriented approximately 45 deg to core axis. Vein set is overprinted by 1mm translucent qtz vein. Small shear at base of piece defined by abundance of anastomosing sub mm white carb-qtz veins, potentially with tlc. 17DZ-44-4A 99.655 - 99.7 m Light to dark green tlc-ophicarbonate with light green tlc bearing domains. Tlc rich domains often occurring as alteration halos following sub mm carb-qtz veins and as patches pseudomorphing lighter areas of srp mesh. <1-3 mm translucent grey to white qtz-carb veins overprint all matrix carbonation. 125 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-44-4B 99.715 - 99.765 m N/A Light green talc ophicarbonate with pale green mgs + tlc bearing zones. Domains of pale green srp with tlc occur as alteration halos around abundant <1 - 10 mm carb qtz. Two prominent composite white carb-qtz veins with translucent light aqua blue talc (willemsite) in lower half of cut face overprint srp, mgs and tlc in pale green zones. Moderate alignment of all veining dipping approximately 20 deg to core axis. 17DZ-44-4C 99.805 - 99.855 Green mylonitic tlc-ophicarbonate with shear fabric in lower half of sample dipping ~50 deg to core axis. Upper half of sample contains pale green domain rich in matrix hosted talc and prominent boudinaged 1-6 mm translucent light blue willemsite bering vein oriented sub-perpendicular to core axis. Pale green talc alteration is associated with weakly deformed carb-qtz, qtz and willemsite veins. Relict <1 mm chromian spinels throughout. 126 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-44-4D 100.055 - 100.105 m Light green to light blue grey talc-ophicarbonate comprised of an upper light blue grey mgs, tlc and qtz domain and a weathered light-pale green srp, mgs and tlc domain. A heavily porous 4 mm cream shear vein defines the border between the two domains. 17DZ-45-1 100.23 - 100.28 m Silicified light pink to cream listvenite with relict srp textures and pale blue green tlc bearing domains. Upper portion of piece is the contact with the tlc-ophicarbonate and contains abundant sub mm red brown carb-oxide veins. 2-8 mm irregular transparent qtz vein at base of piece. Approximately 1% < 1mm relict chromite grains scattered throughout. 17DZ-45-1B 100.37 - 100.42 m Sheared red brown and pink listvenite with fabric dipping 60-80 deg to core axis. Multiple micro faults displacing textures by <1-7 mm. Deformed breccia veins with subrounded carb-qtz vein fragments traced by abundant sub mm carb oxide veins in lower third. White mgs-qtz domains at the base of the sample appear to be boudinaged carb-qtz vein fragments and are associated with blebs of fuchsite. 127 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-45-2 101.19 - 101.24 m N/A Red brown listvenite with abundant branching sub mm carb-oxide veins and 1-5 mm blebs of fuchsite often rimming <1mm chromite grains. Prominent 3-4 mm composite carb-qtz-oxide fault vein dipping 65 deg to core axis with a qtz rich centreline. The upper contact of the composite vein is defined by a 1 mm cataclasite band and several discontinuous/fragmented mm scale cataclasite veins/bands throughout the vein, indicative of episodical movement, brittle deformation and healing. Listvenite above the composite vein has a mylonitic texture defined by moderate alignment of anastomosing sub mm carb-oxide veins dipping ~60 deg TCA. 17DZ-46-2 104.54 - 104.59 m Red-brown, grey and white listvenite comprised of an upper quartz rich breccia that truncates textures and veins from the carbonate rich domain below. Clasts in breccia are ~5-15 mm subangular and silicified with red/brown quartz and carb-oxide cement. Undulating qtz-carb-oxide compound vein at top of sample overprints breccia and cement. ~1% chromite grains scattered throughout. 128 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-52-1 118.91 - 118.96 m Grey, green and red-brown listvenite with abundant 1-5 mm blebs of fuchsite alteration and anastomosing sub mm red-brown and grey-brown carb-oxide veins. Carb oxide veins are overprinted by late <1-2 mm white to pink irregular carb-qtz veins. 17DZ-53-3 123.58 - 123.63 m N/A Red brown, orange and green listvenite with prominent oxidation front defined by sharp colour change from red brown to orange in lower third of cut face. Orange listvenite mylonitic texture patches of vivid green fuchsite. Red/brown oxidation front contains abundant sub mm to aphanitic carb oxide veins that overprints most matrix carbonates and some fuchsite patches. A later set of 1-3 mm wide, 5-10 mm long tension gashes infilled with cream carb-qtz overprint all features 129 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-56-3 132.405 - 132.455 m N/A Red brown and green listvenite with abundant anastomosing sub mm red brown carb oxide veins overprinting grey to green, matrix mgs and fuchsite. Abundant anastomosing carb-oxide veins appear to preserve pre-existing serpentine mesh textures. <1-1 mm sub rounded chromite grains throughout. 17DZ-60-3 141.61 - 141.65 m Dark grey and green listvenite with 1-5 mm blebs of bright green fuchsite. Dark grey to brown sub mm magnesite veins are similar in appearance to more oxidised red-brown carb-oxide veins seen in other sections. Trace sub mm pyrite grains present (reduced environment?). Grey-brown veins and fuchsite overprinted by pink carb-qtz vein in upper right, which is overprinted by trace late-stage porous sub mm red-brown carb-oxide veins and tension gashes. 130 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-62-4 148.745 - 148.795 Red brown listvenite with faint patches of fuchsite overprinted by abundant branching sub mm carb-oxide veins, which are overprinted by quartz veining. All veining and textures overprinted by an irregular 5-8 mm dolomite-qtz vein dipping approx. 55 deg TCA. 17DZ-63-2 150.49 - 150.54 m N/A Dark grey and green listvenite with 1-5 mm blebs of bright green fuchsite (similar to 60Z-3, 25-29 cm). Dark grey-brown sub surrounding fuchsite are similar in appearance to more oxidised red-brown carb oxide veins seen in other samples. 1-3 mm red-brown carb oxide blebs overprint areas rich in grey-brown veining. Trace sub mm pyrite grains throughout. The latest features are a series of 1-2 mm planar well oriented carb-qtz and carb-oxide veins dipping 40-45 deg TCA. Sample appears to have slightly elevated porosity relative to 60Z-3. 131 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-67-3 163.195 - 163.245 m White and green, mgs and fuchsite rich listvenite with mylonitic texture dipping 55 deg TCA. Matrix is overprinted by a 200 x 5 mm carb oxide vein that is cut and displaced by sub mm grey micro-faults striking parallel to fabric (viewed from side of piece in z plane). All veining and micro-faults are overprinted by two 3-4 mm pale yellow dol veins. 1% sub mm black chromite grains throughout, some of which are elongated and oriented parallel to foliation when intersected by micro faults. Visible porosity associated with microfractures/faults. 17DZ-70-2 171.56 - 171.61 m Cream, green and grey listvenite cataclasite/breccia with 1-10 mm subrounded clasts set in a fine grain to aphanitic qtz-mgs-fcs matrix. Two generations of brecciation are present; an older qtz rich breccia with 3-10 mm clasts and followed by cataclasite rich grey-brown veins and matrix fill and partially open sub mm fractures. Texture interpreted as a recently reactivated fault. 132 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-72-2 177.53 - 177.58 m Pink and grey carbonate rich listvenite with 1-5 mm dark grey magnesite and hematite veins. Dark grey veins are overprinted by and slightly offset along 1-2 mm white carb-qtz veins. 17DZ-75-4 188.46 - 188.51 m Grey to light brown listvenite with branching 1-3 mm translucent to opaque red-brown qtz-carb-oxide veins overprinting light brown listvenite. Darker red-grey patches due to have higher proportion of hematite veins and alteration. 17DZ-77-1 192.35 - 192.41 m Cream, pink and red-brown dol-listvenite with brecciated contact of a large pink dol vein. Lower third of piece is the brecciated vein contact comprised of <1-10 mm fragments of pink dol vein material set in a matrix of anastomosing red-brown to grey carb-oxide veins. Two distinct colour zones are observable in the dol vein: a light pink (associated with carb-oxide veins) 133 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description and a cream to white (associated with <1-2 mm qtz veins) zone. Late sub-planar 1 mm dark red-brown carb-oxide vein overprints large dol vein and appears to be a tension related feature. 17DZ-77-4 194.385 - 194.465 m Grey and white dol-listvenite with abundant grey <1 mm anastomosing hematite veins defining a chaotic sheared texture. Strong alignment of veining and imbricated fragments of listvenite in the lower third of sample dipping approximately 50 deg to core axis. A 5-15 mm irregular white carb-qtz vein overprints shear fabric and is inconsistently rimmed by sub mm carb-oxide veins. 17DZ-78-3 196.43 - 196.48 m Red brown and grey listvenite breccia comprised of 1-6 mm subangular translucent to opaque white to grey carb-qtz clasts in a fine grain to aphanitic red-brown carb-oxide cataclasite matrix. A branching 2-5 mm carb-qtz vein overprints the breccia. 134 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-82-3 202.94 – 203 m Dark green chl, qtz, epi and cal bearing metasediment with 1mm think laminations dipping approximately 5-15 deg to core axis. ~10% 3-15 mm translucent to opaque, white to light pink subangular boudinaged qtz-cal vein fragments are rimmed by 1~ mm of chl and loosely associated with epidote alteration. Qtz rich vein fragments appear to have been more brittle and resistant to tectonic stress than surrounding metasediments. Bedding tends to be convoluted adjacent to fragments while the veins tend to be broken rather than deformed in a ductile manner. 17DZ-101-2 245.09 - 245.15 m Dark green chl-epi rich metabasalt with ~30% of cut face overprinted by faint anastomosing Fe-oxide veins, which are overprinted by late, typically <1 mm sigmoidal tension gashes and fractures, filled with dark green to black chlorite, dipping ~30 deg to core axis. Trace 2-5 mm epi altered qtz-calcite vein fragments with chl rims are occasionally overprinted by anastomosing Fe oxide veins. 135 Sample Label Sample Prior to Cutting TS Billet TS Scan XPL TS Billet/Micro drilling Description 17DZ-112-2 278.175 - 278.235 m Green metabasalt with foliation that is oriented sub perpendicular to core axis and ~20% elongate 1-12 mm light green qtz-epi filled amygdules oriented parallel to foliation. Prominent white qtz-cal veins in upper third of sample are oriented ~45 deg to core axis and are overprinted by 1-5 mm black irregular and discontinuous chlorite-tourmaline veins, vein fragments and tension gashes, typically spatially associated with the qtz veins. 136 A.2 Whole-rock quantitative mineralogy Quantitative mineralogy determined by Rietveld analysis of XRD patterns obtained from whole-rock powders. Sample Depth Lith Mgs Dol Cal Tlc Srp Qtz Hem Mgs Brt Ms Chl Act Alb Epi Lmt Total 17DZ-8-3 10.46 Mgs-List. 71 7 0 0 0 19 4 0 0 0 0 0 0 0 0 100 17DZ-13-2 22.67 Mgs-List. 79 2 0 0 0 17 2 0 0 0 0 0 0 0 0 100 17DZ-17-4 32.56 Mgs-List. 71 3 0 0 0 22 4 0 0 0 0 0 0 0 0 100 17DZ-20-3 41.44 Mgs-List. 77 0 2 0 0 18 4 0 0 0 0 0 0 0 0 100 17DZ-24-1 49.05 Dol-List. 3 91 0 0 0 4 2 0 0 0 0 0 0 0 0 100 17DZ-26-2 55.46 Mgs-List. 80 2 0 0 0 17 1 0 0 0 0 0 0 0 0 100 17DZ-26-3 56.67 Mgs-List. 73 3 0 0 0 20 4 0 0 0 0 0 0 0 0 100 17DZ-27-2 58.30 Mgs-List. 76 1 0 0 0 20 3 0 0 0 0 0 0 0 0 100 17DZ-34-1 71.50 Mgs-List. 72 6 0 0 0 22 0 0 0 0 0 0 0 0 0 100 17DZ-37-2 77.24 Dol-List. 8 56 0 0 0 19 1 0 15 0 0 0 0 0 0 100 17DZ-38-3 80.01 Mgs-List. 50 13 0 0 0 33 4 0 0 0 0 0 0 0 0 100 17DZ-38-4A 81.42 Ophi. 53 25 0 0 16 0 1 5 0 0 0 0 0 0 0 100 17DZ-38-4B 81.47 Ophi. 32 5 0 0 54 1 0 8 0 0 0 0 0 0 0 100 17DZ-39-2 82.90 Ophi. 16 2 0 0 64 12 0 6 0 0 0 0 0 0 0 100 17DZ-39-3 84.05 Ophi. 15 0 0 0 63 1 0 20 0 0 0 0 0 0 0 100 17-DZ-39-4 84.65 Ophi. 23 2 0 0 69 1 1 5 0 0 0 0 0 0 0 100 17DZ-41-2 89.07 Ophi. 9 0 0 0 63 1 0 27 0 0 0 0 0 0 0 100 17DZ-43-1 94.26 Ophi. 7 4 0 0 82 0 0 8 0 0 0 0 0 0 0 100 17DZ-43-4 96.28 Ophi. 4 13 0 0 75 1 0 7 0 0 0 0 0 0 0 100 17DZ-43-5 97.16 Ophi. 8 9 0 0 76 1 0 7 0 0 0 0 0 0 0 100 17DZ-44-1 97.33 Ophi. 7 9 0 0 75 3 0 5 0 0 0 0 0 0 0 100 17DZ-44-2A 98.38 Tlc-Ophi. 38 10 0 8 37 6 0 1 0 0 0 0 0 0 0 100 17DZ-44-2B 98.63 Tlc-Ophi. 32 2 0 10 52 3 0 1 0 0 0 0 0 0 0 100 17DZ-44-3A 98.91 Tlc-Ophi. 41 5 0 13 36 4 0 1 0 0 0 0 0 0 0 100 17DZ-44-3B 99.36 Tlc-Ophi. 41 5 0 13 36 4 0 1 0 0 0 0 0 0 0 100 17DZ-44-4A 99.66 Tlc-Ophi. 38 0 0 21 40 1 0 0 0 0 0 0 0 0 0 100 17DZ-44-4B 99.72 Tlc-Ophi. 35 16 0 19 22 9 0 0 0 0 0 0 0 0 0 100 137 17DZ-44-4C 99.81 Tlc-Ophi. 44 6 0 21 18 6 0 5 0 0 0 0 0 0 0 100 17DZ-44-4D 100.06 Tlc-Ophi. 61 7 0 11 13 8 0 0 0 0 0 0 0 0 0 100 17DZ-45-1A 100.23 Mgs-List. 71 14 0 0 0 14 0 0 0 0 0 0 0 0 0 100 17DZ-45-1B 100.37 Mgs-List. 61 6 0 0 0 30 4 0 0 0 0 0 0 0 0 100 17DZ45-2 101.19 Mgs-List. 55 33 0 0 0 12 0 0 0 0 0 0 0 0 0 100 17DZ-46-2 104.54 Mgs-List. 57 31 0 0 0 11 1 0 0 0 0 0 0 0 0 100 17DZ-52-1 118.91 Mgs-List. 63 13 0 0 0 22 2 0 0 0 0 0 0 0 0 100 17DZ-53-3 123.58 Mgs-List. 58 22 0 0 0 18 2 0 0 0 0 0 0 0 0 100 17DZ-56-3 132.41 Mgs-List. 78 5 0 0 0 15 2 0 0 0 0 0 0 0 0 100 17DZ-60-3 141.61 Mgs-List. 85 2 0 0 0 12 1 0 0 0 0 0 0 0 0 100 17DZ-62-4 148.75 Mgs-List. 88 2 0 0 0 8 2 0 0 0 0 0 0 0 0 100 17DZ-63-2 150.49 Mgs-List. 80 2 0 0 0 13 0 0 0 4 0 0 0 0 0 99 17DZ-67-3 163.20 Mgs-List. 82 3 0 0 0 14 1 0 0 0 0 0 0 0 0 100 17DZ-70-2 171.56 Mgs-List. 79 8 0 0 0 14 0 0 0 0 0 0 0 0 0 100 17DZ-72-2 177.53 Mgs-List. 50 31 0 0 0 15 4 0 0 0 0 0 0 0 0 100 17DZ-75-4 188.46 Mgs-List. 71 12 0 0 0 16 1 0 0 0 0 0 0 0 0 100 17DZ-77-1 192.35 Dol-List. 2 94 0 0 0 3 2 0 0 0 0 0 0 0 0 100 17DZ-77-4 194.39 Dol-List. 36 55 0 0 0 6 3 0 0 0 0 0 0 0 0 100 17DZ-78-3 196.43 Dol-List. 1 88 0 0 0 9 1 0 0 0 0 0 0 0 0 100 17DZ-82-3 202.94 Meta. Sole 2 0 6 0 0 4 5 0 0 42 3 5 10 11 11 100 17DZ-101-2 245.09 Meta. Sole 0 2 1 0 0 4 0 0 0 9 10 13 18 42 0 100 17DZ-112-2 278.18 Meta. Sole 0 0 22 0 0 0 0 0 0 10 9 10 34 15 0 100 138 A.3 Whole-rock quantitative mineralogy with amorphous content Quantitative mineralogy with an amorphous phase (Amorph) determined by Rietveld analysis of XRD patterns obtained from whole-rock powders. Sample Depth Lith Amorph Mgs Dol ZnCO3 Cal Tlc Srp Qtz Hem Mgs Brt Ms Chl Act Alb Epi Lmt Total 17DZ-8-3 10 Mgs-List 12 50 6 1 0 0 0 29 2 0 0 0 0 0 0 0 0 100 17DZ-13-2 23 Mgs-List 5 64 2 1 0 0 0 27 1 0 0 0 0 0 0 0 0 100 17DZ-17-4 33 Mgs-List 9 52 3 0 0 0 0 33 3 0 0 0 0 0 0 0 0 100 17DZ-26-2 55 Mgs-List 24 51 1 0 0 0 0 23 1 0 0 0 0 0 0 0 0 100 17DZ-26-3 57 Mgs-List 10 55 3 0 0 0 0 30 2 0 0 0 0 0 0 0 0 100 17DZ-27-2 58 Mgs-List 10 56 1 1 0 0 0 30 2 0 0 0 0 0 0 0 0 100 17DZ-38-3 80 Mgs-List 9 35 9 0 0 0 0 45 2 0 0 0 0 0 0 0 0 100 17DZ-45-1B 100 Mgs-List 3 47 5 0 0 2 0 43 0 0 0 0 0 0 0 0 0 100 17DZ-45-1A 100 Mgs-List 0 60 12 1 0 1 0 26 0 0 0 0 0 0 0 0 0 100 17DZ-46-2 105 Mgs-List 0 50 29 2 0 0 0 19 0 0 0 0 0 0 0 0 0 100 17DZ-52-1 119 Mgs-List 6 49 12 1 0 0 0 32 0 0 0 0 0 0 0 0 0 100 17DZ-53-3 124 Mgs-List 3 47 19 1 0 0 0 29 1 0 0 0 0 0 0 0 0 100 17DZ-56-3 132 Mgs-List 7 62 6 1 0 0 0 23 1 0 0 0 0 0 0 0 0 100 17DZ-60-3 142 Mgs-List 11 66 2 1 0 0 0 19 1 0 0 0 0 0 0 0 0 100 17DZ-63-2 150 Mgs-List 3 71 3 1 0 0 0 22 0 0 0 0 0 0 0 0 0 100 17DZ-67-3 163 Mgs-List 0 70 3 2 0 0 0 24 1 0 0 0 0 0 0 0 0 100 17DZ-70-2 172 Mgs-List 0 67 8 2 0 0 0 23 0 0 0 0 0 0 0 0 0 100 17DZ-72-2 178 Mgs-List 0 43 28 1 0 0 0 26 2 0 0 0 0 0 0 0 0 100 17DZ-24-1 49 Dol-List 0 2 90 0 0 0 0 6 2 0 0 0 0 0 0 0 0 100 17DZ-37-2 77 Dol-List 2 6 47 0 0 0 0 29 1 0 15 0 0 0 0 0 0 100 17DZ-77-4 194 Dol-List 0 34 54 0 0 0 0 12 0 0 0 0 0 0 0 0 0 100 139 Sample Depth Lith Amorph Mgs Dol ZnCO3 Cal Tlc Srp Qtz Hem Mgs Brt Ms Chl Act Alb Epi Lmt Total 17DZ-82-3 203 Meta 0 3 2 0 8 0 0 6 6 0 0 47 4 12 0 12 0 100 17DZ-101-2 245 Meta 9 2 1 0 1 0 0 4 0 0 0 5 11 18 9 40 0 100 17DZ-112-2 278 Meta 8 0 1 0 22 0 0 1 0 0 0 4 14 34 0 16 0 100 140 A.4 Sources of crystal structure data for Rietveld refinement Mineral PDF References: Primary Structure Corundum 00-046-1212 Huang, T., Parrish, W., Masciocchi, N., Wang, P. Adv. X-Ray Anal. 33, 295 (1990). Crystal Structure Source: LPF. 00-010-0173 Natl. Bur. Stand. (U. S. ), Circ. 539 9, 3 (1960). Crystal Structure Source: LPF. Magnesite 04-009-2317 Calculated from LPF using POWD-12++. "Electron-Density Distribution in Magnesite (MgCO3)". Gottlicher S., Vegas A. Acta Crystallogr., Sec. B: Struct. Sci. 44, 362 (1988). 00-008-0479 Natl. Bur. Stand. (U. S. ), Circ. 539 7, 28 (1957). Crystal Structure Source: LPF. Dolomite 00-036-0426 Keller, L., McCarthy, G., North Dakota State Univ., Fargo, ND, USA. ICDD Grant-in-Aid (1985). Crystal Structure Source: LPF. Smithsonite 00-008-0449 Natl. Bur. Stand. (U. S. ), Circ. 539 8, 69 (1959). Crystal Structure Source: LPF. Calcite 00-066-0867 Frolich, S., iNano and Dept. of Chemistry, Aarhus Univ., Denmark. Private Communication (2015). Talc 04-010-7170 Calculated from LPF using POWD-12++. "Strukturverfeinerung am Talk Mg3((OH)2Si4O10)". Perdikatsis, B., Burzlaff, H. Z. Kristallogr. 156, 177-186 (1981). Lizardite 00-050-1606 Krstanovic, I. Neues Jahrb. Mineral., Monatsh. 1997, 451 (1997). Quartz 00-046-1045 Kern, A., Eysel, W., Mineralogisch-Petrograph. Inst., Univ. Heidelberg, Germany. ICDD Grant-in-Aid (1993). Hematite 00-033-0664 Natl. Bur. Stand. (U. S. ) Monogr. 25 18, 37 (1981). Crystal Structure Source: LPF. Magnetite 00-019-0629 Natl. Bur. Stand. (U. S. ) Monogr. 25 5, 31 (1967). Crystal Structure Source: LPF. Baryte 04-007-7651 Calculated from LPF using POWD-12++. "The crystal structure of barite, â-BaSO4, at high temperatures". Haruo Sawada, Takeuchi Y. Z. Kristallogr. 191, 161 (1990). Muscovite 00-006-0263 Gillery, F., Penn State Univ., University Park, PA, USA. Private Communication. Crystal Structure Source: LPF. Clinochlore 00-012-0242 Shirozu. Mineral. J. 2, 209 (1958). Actinolite 00-041-1366 Keller, L., Arizona State University, Tempe, Arizona, USA. ICDD Grant-in-Aid (1988). Urusov, V. et al. Moscow University Geology Bulletin 42, 43 (1987). Albite 04-007-5466 Calculated from LPF using POWD-12++. "Structure of Intermediate Albite, NaAlSi3O8". Phillips M.W., Ribbe P.H., Pinkerton A.A. Acta Crystallogr., Sec. C: Cryst. Struct. Commun. 45, 542 (1989). Epidote 00-045-1446 Rosenstingl, J., Hoffmann, C., Irran, E., Lengauer, C., Tillmanns, E., Univ. Vienna, Austria. ICDD Grant-in-Aid (1992). Acta Crystallogr., Sec. B: Struct. Sci. 44, 351 (1988). 141 A.5 Whole-rock major element geochemistry Major element geochemistry by XRF and ICP-AES on whole-rock powders. Sample Units Depth m Lith TiO2 wt.% SiO2 wt.% Al2O3 wt.% FeO wt.% MnO wt.% MgO wt.% CaO wt.% Na2O wt.% K2O wt.% P2O5 wt.% Cr2O3 wt.% BaO wt.% SrO wt.% LOI wt.% Total wt.% C wt.% 17DZ-8-3 10.46 Mgs-List. 0.01 33.40 0.42 6.19 0.08 25.90 1.94 0.05 0.03 <0.01 0.23 <0.01 <0.01 31.00 99.94 8.50 17DZ-13-2 22.67 Mgs-List. 0.01 29.20 0.27 6.16 0.09 27.90 0.68 0.05 0.01 <0.01 0.33 <0.01 <0.01 33.30 98.69 9.28 17DZ-17-4 32.56 Mgs-List. 0.01 34.80 0.25 6.27 0.07 26.00 1.02 0.02 0.02 0.01 0.27 <0.01 <0.01 30.40 99.84 8.22 17DZ-20-3 41.44 Mgs-List. 0.01 28.80 0.59 6.50 0.10 28.40 1.03 0.03 0.02 0.01 0.30 0.01 <0.01 33.10 99.62 8.90 17DZ-24-1 49.05 Dol-List. 0.01 6.92 0.53 6.60 0.13 17.30 25.20 0.05 0.01 <0.01 0.30 <0.01 0.01 41.20 99.00 11.45 17DZ-26-2 55.46 Mgs-List. 0.02 32.10 0.48 4.20 0.22 28.10 0.79 0.08 0.04 <0.01 0.18 0.02 <0.01 32.90 99.60 8.96 17DZ-26-3 56.67 Mgs-List. 0.02 33.00 0.52 6.01 0.08 26.80 1.08 0.03 0.05 <0.01 0.32 0.01 <0.01 31.20 99.79 8.45 17DZ-27-2 58.30 Mgs-List. 0.01 33.30 0.65 5.94 0.11 27.30 0.48 0.04 0.13 0.01 0.27 <0.01 <0.01 31.20 100.10 8.58 17DZ-34-1 71.50 Mgs-List. <0.01 36.90 0.16 4.52 0.10 25.40 1.62 0.01 0.01 0.01 0.20 0.02 <0.01 30.30 99.75 8.42 17DZ-37-2 77.24 Dol-List. 0.01 29.60 0.22 3.00 0.06 11.25 13.65 0.02 0.06 0.01 0.16 11.10 0.14 23.60 93.21 6.39 17DZ-38-3 80.01 Mgs-List. 0.01 50.50 0.44 5.34 0.07 18.25 2.80 0.01 0.02 0.02 0.28 <0.01 <0.01 22.50 100.84 6.15 17DZ-38-4A 81.42 Ophi. 0.01 11.35 0.80 6.47 0.10 33.80 7.16 0.06 0.01 0.01 0.37 0.02 0.01 38.90 99.79 9.56 17DZ-38-4B 81.47 Ophi. 0.01 29.70 0.49 6.24 0.07 37.60 1.34 0.06 0.01 <0.01 0.34 <0.01 <0.01 23.60 100.15 3.79 17DZ-39-2 82.90 Ophi. <0.01 46.10 0.27 5.47 0.06 32.00 0.72 0.06 0.01 0.02 0.23 <0.01 <0.01 16.35 101.90 2.16 17DZ-39-3 84.05 Ophi. <0.01 33.20 0.47 7.61 0.04 37.40 0.40 0.05 0.01 0.01 0.34 0.02 <0.01 19.35 99.75 2.18 17DZ-39-4 84.65 Ophi. 0.01 32.00 0.48 6.17 0.07 38.80 0.95 0.02 0.01 0.02 0.41 <0.01 <0.01 21.50 101.13 2.87 17DZ-41-2 89.07 Ophi. <0.01 37.00 0.39 6.94 0.06 37.10 0.24 0.06 0.01 0.01 0.46 0.01 <0.01 17.05 100.10 1.25 17DZ-43-1 94.26 Ophi. <0.01 36.30 0.18 6.34 0.07 37.60 1.20 0.06 0.01 <0.01 0.35 0.10 <0.01 17.25 100.17 1.46 142 Sample Units Depth m Lith TiO2 wt.% SiO2 wt.% Al2O3 wt.% FeO wt.% MnO wt.% MgO wt.% CaO wt.% Na2O wt.% K2O wt.% P2O5 wt.% Cr2O3 wt.% BaO wt.% SrO wt.% LOI wt.% Total wt.% C wt.% 17DZ-8-3 10.46 Mgs-List. 0.01 33.40 0.42 6.19 0.08 25.90 1.94 0.05 0.03 <0.01 0.23 <0.01 <0.01 31.00 99.94 8.50 17DZ-43-4 96.28 Ophi. <0.01 34.20 0.30 5.94 0.14 35.70 3.42 0.05 0.01 <0.01 0.34 0.01 0.01 18.80 99.58 2.16 17DZ-43-5 97.16 Ophi. <0.01 35.80 0.36 6.22 0.15 36.30 2.58 0.02 0.01 <0.01 0.39 <0.01 0.01 18.05 100.58 1.98 17DZ-44-1 97.33 Ophi. 0.01 36.30 0.56 6.04 0.13 35.60 2.76 0.02 0.01 0.01 0.41 <0.01 0.01 18.10 100.63 1.99 17DZ-44-2A 98.38 Ophi. <0.01 31.70 0.14 5.61 0.10 32.70 2.94 0.05 <0.01 0.01 0.27 <0.01 0.02 25.90 100.07 5.43 17DZ-44-2B 98.63 Tlc-Ophi. <0.01 34.30 0.21 4.52 0.13 36.80 0.64 0.03 0.01 <0.01 0.28 <0.01 <0.01 22.90 100.32 4.01 17DZ-44-3A 98.91 Tlc-Ophi. <0.01 29.30 0.21 5.68 0.09 35.30 1.77 0.05 0.01 <0.01 0.24 <0.01 0.01 26.80 100.09 5.64 17DZ-44-3B 99.36 Tlc-Ophi. <0.01 31.50 0.36 5.56 0.11 37.50 0.70 0.05 0.01 <0.01 0.35 <0.01 <0.01 23.60 100.36 3.75 17DZ-44-4A 99.66 Tlc-Ophi. <0.01 26.80 0.24 6.36 0.06 30.10 2.61 0.09 0.02 <0.01 0.30 <0.01 0.01 32.80 100.10 8.77 17DZ-44-4B 99.72 Tlc-Ophi. <0.01 30.20 0.31 7.27 0.05 35.90 0.31 0.02 0.01 0.01 0.43 <0.01 <0.01 26.40 101.72 4.47 17DZ-44-4C 99.81 Tlc-Ophi. <0.01 34.20 0.17 4.87 0.07 29.50 4.40 0.03 0.01 <0.01 0.21 <0.01 0.06 26.10 100.16 6.12 17DZ-44-4D 100.06 Tlc-Ophi. <0.01 32.20 0.19 4.49 0.12 32.60 2.03 0.06 0.02 0.01 0.24 <0.01 0.03 27.30 99.79 6.56 17DZ-45-1A 100.23 Mgs-List. <0.01 27.80 0.13 4.41 0.07 27.50 3.78 0.06 0.01 0.01 0.19 0.01 0.03 34.90 99.39 9.68 17DZ-45-1B 100.37 Mgs-List. 0.01 45.70 0.51 4.39 0.10 21.30 1.65 0.03 0.03 <0.01 0.30 <0.01 0.01 25.20 99.72 6.77 17DZ-45-2 101.19 Mgs-List. <0.01 22.90 0.45 5.96 0.10 24.80 9.09 0.04 0.04 0.01 0.31 <0.01 0.03 35.90 100.29 9.88 17DZ-46-2 104.54 Mgs-List. 0.01 19.40 0.31 6.09 0.09 26.00 8.79 0.02 0.02 <0.01 0.18 <0.01 0.01 37.40 99.00 10.45 17DZ-52-1 118.91 Mgs-List. 0.02 35.50 1.14 3.78 0.06 24.10 3.58 0.02 0.21 0.01 0.23 <0.01 <0.01 30.50 99.57 8.36 17DZ-53-3 123.58 Mgs-List. 0.03 31.10 1.68 5.31 0.10 22.90 5.60 0.03 0.35 <0.01 0.28 0.02 0.01 31.60 99.60 8.50 17DZ-56-3 132.41 Mgs-List. 0.04 26.20 1.62 6.17 0.07 28.30 1.91 0.02 0.27 <0.01 0.31 <0.01 <0.01 34.30 99.90 9.29 17DZ-60-3 141.61 Mgs-List. 0.05 23.50 1.85 4.54 0.05 31.50 0.76 0.03 0.36 <0.01 0.29 <0.01 <0.01 36.50 99.94 9.78 17DZ-62-4 148.75 Mgs-List. <0.01 16.20 0.23 5.47 0.08 34.10 1.00 0.05 0.03 0.01 0.21 <0.01 <0.01 40.90 98.89 11.60 17DZ-63-2 150.49 Mgs-List. 0.04 24.70 1.38 4.35 0.09 30.60 1.11 0.02 0.22 0.02 0.28 <0.01 <0.01 36.30 99.60 9.87 143 Sample Units Depth m Lith TiO2 wt.% SiO2 wt.% Al2O3 wt.% FeO wt.% MnO wt.% MgO wt.% CaO wt.% Na2O wt.% K2O wt.% P2O5 wt.% Cr2O3 wt.% BaO wt.% SrO wt.% LOI wt.% Total wt.% C wt.% 17DZ-8-3 10.46 Mgs-List. 0.01 33.40 0.42 6.19 0.08 25.90 1.94 0.05 0.03 <0.01 0.23 <0.01 <0.01 31.00 99.94 8.50 17DZ-67-3 163.20 Mgs-List. 0.02 25.60 1.11 6.01 0.07 29.20 1.15 0.02 0.20 0.01 0.25 <0.01 <0.01 35.40 99.71 9.87 17DZ-70-2 171.56 Mgs-List. 0.02 25.00 1.03 5.55 0.07 28.00 2.28 0.05 0.15 0.01 0.30 <0.01 <0.01 35.70 98.78 9.84 17DZ-72-2 177.53 Mgs-List. 0.01 26.10 0.31 7.15 0.16 22.80 8.43 0.01 <0.01 0.01 0.16 <0.01 0.01 33.00 98.95 9.18 17DZ-75-4 188.46 Mgs-List. 0.01 28.00 0.41 5.64 0.15 26.80 3.51 0.01 0.02 <0.01 0.32 <0.01 <0.01 34.00 99.50 9.34 17DZ-77-1 192.35 Dol-List. <0.01 15.05 0.31 4.33 0.12 15.65 25.00 0.03 0.02 0.01 0.09 <0.01 0.03 38.50 99.62 10.60 17DZ-77-4 194.39 Dol-List. <0.01 11.45 0.29 7.28 0.13 24.10 16.05 0.02 0.01 0.01 0.28 0.01 0.03 40.10 100.57 11.00 17DZ-78-3 196.43 Dol-List. <0.01 5.25 0.15 5.79 0.11 17.35 27.80 0.02 0.01 <0.01 0.12 <0.01 0.06 42.60 99.90 11.90 17DZ-82-3 202.94 Meta. 2.78 40.00 16.55 12.91 0.15 2.87 7.49 1.12 5.86 0.74 0.01 0.04 0.01 6.41 98.38 0.96 17DZ-101-2 245.09 Meta. 1.59 45.60 16.40 11.07 0.16 4.49 11.95 1.77 1.11 0.22 0.03 0.03 0.07 3.53 99.25 0.21 17DZ-112-2 278.18 Meta. 1.47 37.70 14.25 6.25 0.13 2.97 16.85 3.70 1.13 0.20 0.01 0.03 0.05 12.65 98.09 2.89 17DZ-1-4 Surface Atlin Std. <0.01 38.60 0.76 7.03 0.10 40.60 0.82 0.01 <0.01 <0.01 0.34 100.39 <0.01 11.35 100.39 0.20 17DZ1-3 Surface Atlin Srp. <0.01 37.60 0.91 6.45 0.11 38.70 0.94 0.01 <0.01 0.02 0.35 100.11 <0.01 14.30 100.11 0.73 17DZ-1-6 Surface Atlin Srp. <0.01 37.60 0.91 6.42 0.11 38.70 0.91 0.01 0.01 <0.01 0.34 100.03 <0.01 14.30 100.03 0.68 17DZ-1-8 Surface Atlin Srp. <0.01 37.80 0.91 6.49 0.11 38.90 0.92 0.02 0.02 0.01 0.35 100.45 <0.01 14.20 100.45 0.69 17DZ-1-1 Surface Atlin Soap. <0.01 34.40 0.35 5.74 0.07 35.40 0.16 0.05 0.03 <0.01 0.42 99.46 <0.01 22.20 99.46 4.72 17DZ-1-2 Surface Atlin Soap. <0.01 34.50 0.34 5.70 0.07 35.80 0.17 0.02 0.01 <0.01 0.35 99.80 <0.01 22.20 99.80 4.70 17DZ-1-5 Surface Atlin Soap. <0.01 34.00 0.32 5.60 0.07 35.40 0.16 0.01 0.02 0.02 0.32 98.64 <0.01 22.10 98.64 4.67 17DZ-1-7 Surface Atlin Soap. <0.01 34.00 0.30 5.41 0.07 35.50 0.16 0.02 0.03 0.01 0.32 98.52 <0.01 22.10 98.52 4.68 144 A.6 Whole-rock trace element geochemistry Trace element geochemistry by XRF and ICP-AES on whole-rock powders. Sample Units Depth m Lith Ba ppm Cs ppm Rb ppm Sr ppm Pb ppm Tl ppm Li ppm Sc ppm Th ppm U ppm Zr ppm Hf ppm Nb ppm Ta ppm Y ppm 17DZ-8-3 10.46 Mgs-List. 18.50 0.21 0.70 26.00 3.00 <0.02 <10 8.00 0.05 25.80 <2 <0.2 <0.2 <0.1 0.30 17DZ-13-2 22.67 Mgs-List. 8.00 0.18 0.60 13.60 <2 <0.02 10.00 3.00 <0.05 16.50 <2 <0.2 <0.2 <0.1 0.10 17DZ-17-4 32.56 Mgs-List. 8.50 0.21 0.70 18.80 6.00 <0.02 10.00 4.00 <0.05 1.78 <2 <0.2 <0.2 <0.1 0.10 17DZ-20-3 41.44 Mgs-List. 47.80 0.63 1.20 19.50 2.00 <0.02 10.00 7.00 <0.05 0.47 <2 <0.2 <0.2 <0.1 0.30 17DZ-24-1 49.05 Dol-List. 9.40 0.09 0.30 118.50 25.00 <0.02 <10 10.00 <0.05 55.40 <2 <0.2 <0.2 <0.1 0.40 17DZ-26-2 55.46 Mgs-List. 151.00 1.06 1.60 30.20 7.00 <0.02 10.00 6.00 0.06 2.43 2.00 <0.2 0.20 <0.1 0.30 17DZ-26-3 56.67 Mgs-List. 67.80 1.62 2.80 27.60 6.00 <0.02 20.00 8.00 <0.05 0.69 <2 <0.2 <0.2 <0.1 0.20 17DZ-27-2 58.30 Mgs-List. 35.40 1.70 3.30 27.70 4.00 <0.02 20.00 6.00 0.06 7.78 <2 <0.2 <0.2 <0.1 0.30 17DZ-34-1 71.50 Mgs-List. 166.50 0.28 0.70 16.10 33.00 <0.02 10.00 3.00 <0.05 1.60 <2 <0.2 <0.2 <0.1 0.10 17DZ-37-2 77.24 Dol-List. >10000 0.35 0.80 1125.00 15.00 <0.02 10.00 2.00 <0.05 5.24 <2 <0.2 <0.2 <0.1 0.70 17DZ-38-3 80.01 Mgs-List. 18.20 0.22 1.20 46.90 5.00 <0.02 20.00 4.00 0.07 0.67 <2 <0.2 <0.2 <0.1 0.20 17DZ-38-4A 81.42 Ophi. 154.50 0.19 0.40 117.00 98.00 <0.02 <10 8.00 0.05 1.30 <2 <0.2 <0.2 <0.1 0.20 17DZ-38-4B 81.47 Ophi. 12.60 0.07 0.20 32.90 90.00 <0.02 10.00 7.00 <0.05 1.48 <2 <0.2 <0.2 <0.1 0.10 17DZ-39-2 82.90 Ophi. 14.10 0.10 0.20 18.30 6.00 <0.02 10.00 5.00 <0.05 0.75 <2 <0.2 <0.2 <0.1 0.10 17DZ-39-3 84.05 Ophi. 210.00 0.18 <0.2 16.90 3.00 <0.02 10.00 8.00 <0.05 1.17 <2 <0.2 <0.2 <0.1 0.10 17DZ-39-4 84.65 Ophi. 21.10 0.23 0.30 24.60 2.00 <0.02 10.00 9.00 <0.05 0.15 <2 <0.2 <0.2 <0.1 0.10 17DZ-41-2 89.07 Ophi. 77.70 0.24 0.20 15.60 <2 <0.02 10.00 8.00 <0.05 3.75 <2 <0.2 <0.2 <0.1 0.10 145 Sample Units Depth m Lith Ba ppm Cs ppm Rb ppm Sr ppm Pb ppm Tl ppm Li ppm Sc ppm Th ppm U ppm Zr ppm Hf ppm Nb ppm Ta ppm Y ppm 17DZ-43-1 94.26 Ophi. 929.00 0.14 0.20 36.90 <2 <0.02 10.00 6.00 <0.05 1.43 <2 <0.2 <0.2 <0.1 <0.1 17DZ-43-4 96.28 Ophi. 67.50 0.14 0.20 175.50 2.00 <0.02 10.00 5.00 <0.05 0.55 <2 <0.2 <0.2 <0.1 <0.1 17DZ-43-5 97.16 Ophi. 12.60 0.16 0.30 118.50 3.00 <0.02 10.00 7.00 <0.05 0.20 <2 <0.2 <0.2 <0.1 <0.1 17DZ-44-1 97.33 Ophi. 16.40 0.21 0.40 128.50 <2 <0.02 10.00 9.00 <0.05 0.12 <2 <0.2 <0.2 <0.1 0.10 17DZ-44-2A 98.38 Ophi. 18.70 0.06 <0.2 212.00 3.00 <0.02 10.00 3.00 <0.05 0.58 <2 <0.2 0.20 <0.1 0.10 17DZ-44-2B 98.63 Tlc-Ophi. 24.90 0.17 0.30 42.00 2.00 <0.02 10.00 4.00 <0.05 0.20 <2 <0.2 <0.2 <0.1 0.10 17DZ-44-3A 98.91 Tlc-Ophi. 10.60 0.11 <0.2 134.00 2.00 <0.02 20.00 4.00 0.28 0.63 <2 <0.2 4.90 <0.1 0.20 17DZ-44-3B 99.36 Tlc-Ophi. 14.70 0.22 <0.2 73.50 4.00 <0.02 20.00 6.00 0.07 1.14 <2 <0.2 1.00 <0.1 0.10 17DZ-44-4A 99.66 Tlc-Ophi. 30.60 0.22 0.20 174.00 31.00 <0.02 30.00 4.00 <0.05 5.67 <2 <0.2 <0.2 <0.1 0.10 17DZ-44-4B 99.72 Tlc-Ophi. 7.60 0.09 <0.2 34.10 3.00 <0.02 30.00 7.00 0.05 0.46 <2 <0.2 0.50 <0.1 0.10 17DZ-44-4C 99.81 Tlc-Ophi. 7.40 0.30 0.40 522.00 17.00 <0.02 30.00 3.00 <0.05 0.31 <2 <0.2 <0.2 <0.1 <0.1 17DZ-44-4D 100.06 Tlc-Ophi. 9.70 0.12 <0.2 299.00 11.00 <0.02 40.00 4.00 <0.05 1.43 <2 <0.2 0.30 <0.1 0.10 17DZ-45-1A 100.23 Mgs-List. 101.00 0.21 0.60 324.00 2.00 <0.02 10.00 2.00 <0.05 3.01 <2 <0.2 <0.2 <0.1 0.10 17DZ-45-1B 100.37 Mgs-List. 32.40 0.33 1.50 78.00 34.00 <0.02 20.00 3.00 0.26 3.04 2.00 <0.2 0.30 <0.1 0.30 17DZ-45-2 101.19 Mgs-List. 21.00 0.74 2.00 245.00 13.00 <0.02 10.00 5.00 <0.05 0.22 <2 <0.2 <0.2 <0.1 0.10 17DZ-46-2 104.54 Mgs-List. 11.90 0.37 1.20 94.00 19.00 <0.02 10.00 4.00 0.09 1.15 <2 <0.2 <0.2 <0.1 0.30 17DZ-52-1 118.91 Mgs-List. 25.80 2.67 11.50 44.10 5.00 <0.02 10.00 8.00 0.07 6.17 <2 <0.2 <0.2 <0.1 0.50 17DZ-53-3 123.58 Mgs-List. 197.00 7.68 20.30 76.00 9.00 <0.02 10.00 7.00 <0.05 0.34 <2 <0.2 <0.2 <0.1 1.30 17DZ-56-3 132.41 Mgs-List. 28.70 3.11 14.20 51.30 4.00 <0.02 40.00 8.00 <0.05 0.64 <2 <0.2 <0.2 <0.1 0.70 17DZ-60-3 141.61 Mgs-List. 17.50 6.04 20.90 22.10 6.00 <0.02 30.00 11.00 <0.05 1.42 <2 <0.2 <0.2 <0.1 0.80 17DZ-62-4 148.75 Mgs-List. 17.30 0.34 1.10 17.20 3.00 <0.02 <10 4.00 <0.05 1.59 <2 <0.2 <0.2 <0.1 0.20 17DZ-63-2 150.49 Mgs-List. 17.00 1.85 11.50 29.30 <2 <0.02 30.00 9.00 <0.05 0.31 <2 <0.2 <0.2 <0.1 1.10 146 Sample Units Depth m Lith Ba ppm Cs ppm Rb ppm Sr ppm Pb ppm Tl ppm Li ppm Sc ppm Th ppm U ppm Zr ppm Hf ppm Nb ppm Ta ppm Y ppm 17DZ-67-3 163.20 Mgs-List. 10.80 2.63 9.40 40.20 6.00 <0.02 20.00 6.00 <0.05 0.42 <2 <0.2 <0.2 <0.1 0.60 17DZ-70-2 171.56 Mgs-List. 26.50 2.79 7.80 53.10 8.00 <0.02 10.00 8.00 <0.05 7.06 <2 <0.2 <0.2 <0.1 0.40 17DZ-72-2 177.53 Mgs-List. 10.70 0.25 1.00 140.00 16.00 <0.02 10.00 2.00 0.06 2.36 <2 <0.2 <0.2 <0.1 0.10 17DZ-75-4 188.46 Mgs-List. 17.80 0.36 1.30 54.20 32.00 <0.02 10.00 5.00 0.07 1.85 <2 <0.2 <0.2 <0.1 0.10 17DZ-77-1 192.35 Dol-List. 39.50 0.22 1.10 265.00 10.00 <0.02 10.00 5.00 <0.05 0.33 <2 <0.2 <0.2 <0.1 1.50 17DZ-77-4 194.39 Dol-List. 45.50 0.26 0.50 272.00 17.00 <0.02 10.00 4.00 <0.05 3.56 <2 <0.2 <0.2 <0.1 0.30 17DZ-78-3 196.43 Dol-List. 9.20 0.17 0.50 546.00 13.00 <0.02 <10 2.00 <0.05 0.50 <2 <0.2 <0.2 <0.1 1.00 17DZ-82-3 202.94 Meta. 386.00 4.15 95.00 159.00 2.00 0.09 110.00 25.00 5.94 1.67 396.00 9.40 60.00 3.60 43.50 17DZ-101-2 245.09 Meta. 273.00 0.56 21.00 690.00 <2 <0.02 20.00 26.00 1.51 2.38 121.00 3.10 15.20 0.90 20.20 17DZ-112-2 278.18 Meta. 271.00 3.44 23.50 483.00 2.00 <0.02 20.00 22.00 1.42 5.10 110.00 2.60 16.00 0.90 17.40 17DZ-1-4 Surface Atlin Std. 1.50 <0.05 0.30 0.20 <2 <0.02 <10 9.00 <0.05 <0.05 <2 <0.2 <0.2 <0.1 0.10 17DZ1-3 Surface Atlin Srp. 3.40 <0.05 0.40 1.50 <2 <0.02 <10 9.00 <0.05 0.09 <2 <0.2 <0.2 <0.1 0.20 17DZ-1-6 Surface Atlin Srp. 2.40 <0.05 0.20 1.50 2.00 <0.02 <10 8.00 <0.05 0.08 <2 <0.2 <0.2 <0.1 0.10 17DZ-1-8 Surface Atlin Srp. 1.70 <0.05 0.20 1.40 2.00 <0.02 <10 8.00 <0.05 0.08 <2 <0.2 <0.2 <0.1 0.10 17DZ-1-1 Surface Atlin Soap. 26.90 <0.05 1.60 12.80 3.00 <0.02 <10 6.00 <0.05 <0.05 <2 <0.2 <0.2 <0.1 <0.1 17DZ-1-2 Surface Atlin Soap. 27.70 <0.05 1.80 12.50 <2 <0.02 <10 5.00 <0.05 <0.05 <2 <0.2 <0.2 <0.1 <0.1 17DZ-1-5 Surface Atlin Soap. 26.70 <0.05 1.80 12.20 <2 <0.02 <10 5.00 <0.05 <0.05 <2 <0.2 <0.2 <0.1 <0.1 17DZ-1-7 Surface Atlin Soap. 25.90 <0.05 1.70 11.70 <2 <0.02 <10 5.00 <0.05 <0.05 <2 <0.2 <0.2 <0.1 <0.1 147 Sample Depth Lith La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-8-3 10.46 Mgs-List. 0.20 0.40 0.04 0.20 0.06 <0.03 <0.05 0.01 0.05 0.01 <0.03 <0.01 0.05 <0.01 17DZ-13-2 22.67 Mgs-List. 0.20 0.40 0.04 0.20 0.05 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 0.04 <0.01 17DZ-17-4 32.56 Mgs-List. 0.20 0.30 0.03 0.10 <0.03 <0.03 <0.05 0.01 <0.05 0.01 <0.03 <0.01 <0.03 <0.01 17DZ-20-3 41.44 Mgs-List. 0.10 0.20 0.03 0.10 0.03 <0.03 <0.05 0.01 <0.05 0.02 0.05 0.01 0.04 0.01 17DZ-24-1 49.05 Dol-List. 0.20 0.20 0.04 0.10 <0.03 <0.03 <0.05 0.01 0.09 0.02 0.04 <0.01 0.06 <0.01 17DZ-26-2 55.46 Mgs-List. 0.30 0.60 0.06 0.30 0.08 <0.03 0.05 0.02 0.07 0.01 0.05 <0.01 0.04 <0.01 17DZ-26-3 56.67 Mgs-List. 0.10 0.10 <0.03 0.10 <0.03 <0.03 <0.05 0.01 <0.05 0.01 <0.03 0.01 0.03 <0.01 17DZ-27-2 58.30 Mgs-List. 0.20 0.30 0.05 0.20 0.05 <0.03 <0.05 0.01 <0.05 0.01 0.04 <0.01 0.03 <0.01 17DZ-34-1 71.50 Mgs-List. 0.10 0.20 0.03 0.10 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-37-2 77.24 Dol-List. 1.40 0.20 <0.03 0.40 0.61 <0.03 0.12 0.02 <0.05 <0.01 <0.03 <0.01 0.11 0.02 17DZ-38-3 80.01 Mgs-List. 0.30 0.60 0.07 0.20 0.03 <0.03 <0.05 <0.01 <0.05 0.01 <0.03 <0.01 <0.03 <0.01 17DZ-38-4A 81.42 Ophi. 0.10 0.30 0.04 0.10 0.03 <0.03 <0.05 0.01 <0.05 0.01 0.03 <0.01 0.07 <0.01 17DZ-38-4B 81.47 Ophi. 0.10 0.20 0.03 0.10 0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 0.03 <0.01 17DZ-39-2 82.90 Ophi. 0.10 0.10 <0.03 0.10 0.04 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-39-3 84.05 Ophi. <0.1 <0.1 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-39-4 84.65 Ophi. <0.1 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-41-2 89.07 Ophi. <0.1 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-43-1 94.26 Ophi. <0.1 <0.1 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-43-4 96.28 Ophi. <0.1 <0.1 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-43-5 97.16 Ophi. 0.10 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-1 97.33 Ophi. 0.10 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 0.01 <0.03 0.01 0.03 <0.01 17DZ-44-2A 98.38 Ophi. 0.20 0.40 0.04 0.10 <0.03 <0.03 <0.05 0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 148 Sample Depth Lith La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-44-2B 98.63 Tlc-Ophi. <0.1 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-3A 98.91 Tlc-Ophi. 1.80 4.50 0.59 2.30 0.34 0.08 0.15 0.01 0.07 <0.01 0.03 <0.01 <0.03 <0.01 17DZ-44-3B 99.36 Tlc-Ophi. 0.40 0.80 0.10 0.30 0.04 <0.03 <0.05 0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-4A 99.66 Tlc-Ophi. 0.10 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-4B 99.72 Tlc-Ophi. 0.20 0.50 0.06 0.20 0.04 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-4C 99.81 Tlc-Ophi. <0.1 0.10 <0.03 <0.1 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-44-4D 100.06 Tlc-Ophi. 0.10 0.40 0.04 0.20 0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-45-1A 100.23 Mgs-List. 0.10 0.20 0.03 0.10 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-45-1B 100.37 Mgs-List. 0.80 1.50 0.17 0.70 0.14 <0.03 0.08 0.01 0.06 0.01 0.03 0.01 0.03 0.01 17DZ-45-2 101.19 Mgs-List. 0.10 0.20 <0.03 0.10 <0.03 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 0.03 <0.01 17DZ-46-2 104.54 Mgs-List. 0.30 0.60 0.08 0.30 0.04 <0.03 0.06 0.01 <0.05 0.01 <0.03 0.01 <0.03 <0.01 17DZ-52-1 118.91 Mgs-List. 0.20 0.50 0.06 0.20 0.04 <0.03 0.07 0.01 0.10 0.02 0.07 0.01 0.07 0.01 17DZ-53-3 123.58 Mgs-List. <0.1 0.10 <0.03 0.10 0.04 <0.03 0.12 0.02 0.18 0.05 0.16 0.03 0.17 0.03 17DZ-56-3 132.41 Mgs-List. 0.10 0.10 <0.03 0.10 0.05 <0.03 <0.05 0.02 0.14 0.03 0.08 0.01 0.09 0.01 17DZ-60-3 141.61 Mgs-List. 0.10 0.30 0.03 0.10 0.06 <0.03 0.07 0.01 0.14 0.04 0.12 0.02 0.15 0.02 17DZ-62-4 148.75 Mgs-List. 0.10 0.20 0.03 0.10 <0.03 <0.03 <0.05 <0.01 <0.05 0.01 0.03 <0.01 0.04 <0.01 17DZ-63-2 150.49 Mgs-List. 0.10 0.20 <0.03 0.10 0.07 0.03 0.10 0.02 0.17 0.04 0.11 0.03 0.12 0.02 17DZ-67-3 163.20 Mgs-List. 0.10 0.10 <0.03 0.10 <0.03 <0.03 0.06 0.01 0.11 0.03 0.09 0.01 0.10 0.01 17DZ-70-2 171.56 Mgs-List. 0.10 0.20 <0.03 0.10 <0.03 <0.03 <0.05 <0.01 0.06 0.02 0.05 <0.01 0.09 <0.01 17DZ-72-2 177.53 Mgs-List. 0.20 0.40 0.04 0.20 0.06 <0.03 <0.05 <0.01 <0.05 <0.01 <0.03 <0.01 <0.03 <0.01 17DZ-75-4 188.46 Mgs-List. 0.30 0.50 0.05 0.10 0.05 <0.03 <0.05 0.01 <0.05 0.01 <0.03 <0.01 <0.03 <0.01 17DZ-77-1 192.35 Dol-List. 0.20 0.50 0.09 0.40 0.14 0.06 0.26 0.06 0.27 0.06 0.18 0.02 0.08 0.02 149 Sample Depth Lith La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-77-4 194.39 Dol-List. 0.10 0.30 0.04 0.10 0.05 <0.03 0.08 0.01 0.05 0.02 0.03 <0.01 <0.03 <0.01 17DZ-78-3 196.43 Dol-List. 0.40 0.70 0.10 0.30 0.14 0.04 0.15 0.02 0.15 0.02 0.06 0.01 0.06 <0.01 17DZ-82-3 202.94 Meta. 57.60 135.50 15.40 59.50 12.25 3.05 10.65 1.55 8.82 1.72 4.44 0.61 3.74 0.54 17DZ-101-2 245.09 Meta. 14.90 33.30 4.22 17.90 4.43 1.29 3.85 0.66 3.83 0.76 2.15 0.28 1.86 0.31 17DZ-112-2 278.18 Meta. 15.10 32.70 4.13 18.40 4.18 1.10 3.44 0.57 3.38 0.68 1.91 0.22 1.54 0.19 17DZ-1-4 Surface Atlin Std. 0.01 2320.00 <0.03 <0.1 <0.03 0.70 <5 <0.01 <0.03 <0.1 <0.03 <0.01 <0.03 <0.2 17DZ1-3 Surface Atlin Srp. <0.01 2430.00 <0.03 0.10 <0.03 0.90 <5 <0.01 <0.03 0.10 <0.03 <0.01 0.04 <0.2 17DZ-1-6 Surface Atlin Srp. <0.01 2290.00 <0.03 <0.1 <0.03 0.80 <5 <0.01 <0.03 <0.1 <0.03 <0.01 0.03 <0.2 17DZ-1-8 Surface Atlin Srp. 0.01 2330.00 <0.03 <0.1 <0.03 0.90 <5 <0.01 <0.03 <0.1 <0.03 <0.01 0.03 <0.2 17DZ-1-1 Surface Atlin Soap. <0.01 2880.00 <0.03 <0.1 <0.03 0.40 <5 <0.01 <0.03 <0.1 <0.03 <0.01 <0.03 <0.2 17DZ-1-2 Surface Atlin Soap. <0.01 2340.00 <0.03 <0.1 <0.03 0.40 <5 <0.01 <0.03 <0.1 <0.03 <0.01 <0.03 <0.2 17DZ-1-5 Surface Atlin Soap. <0.01 2200.00 <0.03 <0.1 <0.03 0.40 <5 <0.01 <0.03 <0.1 <0.03 <0.01 <0.03 <0.2 17DZ-1-7 Surface Atlin Soap. <0.01 2170.00 <0.03 <0.1 <0.03 0.30 <5 <0.01 <0.03 <0.1 <0.03 <0.01 <0.03 <0.2 150 Sample Depth Lith Cu Ag Zn Cd Hg Ga In Ge Sn As Sb Bi Se Te Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-8-3 10.46 Mgs-List. 7.00 <0.5 46.00 <0.5 0.09 0.70 0.01 <5 <1 4.70 0.17 0.01 <0.2 <0.01 17DZ-13-2 22.67 Mgs-List. 6.00 <0.5 55.00 <0.5 0.36 0.60 <0.005 <5 <1 5.90 0.08 <0.01 <0.2 0.01 17DZ-17-4 32.56 Mgs-List. 6.00 <0.5 65.00 <0.5 0.06 0.50 <0.005 <5 <1 13.90 0.35 0.02 <0.2 0.01 17DZ-20-3 41.44 Mgs-List. 10.00 <0.5 138.00 <0.5 0.11 0.70 0.01 <5 <1 33.60 0.19 0.01 0.30 <0.01 17DZ-24-1 49.05 Dol-List. 2.00 <0.5 167.00 0.60 0.20 0.90 0.01 <5 <1 6.40 4.05 <0.01 <0.2 0.01 17DZ-26-2 55.46 Mgs-List. 35.00 <0.5 104.00 <0.5 3.29 0.80 <0.005 <5 <1 6.00 0.08 0.01 <0.2 0.01 17DZ-26-3 56.67 Mgs-List. 9.00 <0.5 137.00 <0.5 0.12 0.70 <0.005 <5 <1 17.20 0.22 0.01 <0.2 0.01 17DZ-27-2 58.30 Mgs-List. 8.00 <0.5 70.00 <0.5 0.09 0.90 <0.005 <5 <1 8.80 0.13 0.01 <0.2 <0.01 17DZ-34-1 71.50 Mgs-List. 10.00 <0.5 215.00 <0.5 1.13 0.40 <0.005 <5 <1 165.00 0.29 0.01 0.30 0.02 17DZ-37-2 77.24 Dol-List. 3.00 <0.5 101.00 0.50 0.42 0.50 <0.005 <5 <1 16.50 0.42 <0.01 0.40 <0.01 17DZ-38-3 80.01 Mgs-List. 27.00 <0.5 45.00 <0.5 3.03 0.60 <0.005 <5 <1 12.80 1.48 0.01 0.30 <0.01 17DZ-38-4A 81.42 Ophi. 3.00 <0.5 197.00 0.50 2.06 0.80 0.01 <5 <1 6.10 0.07 <0.01 0.30 0.03 17DZ-38-4B 81.47 Ophi. 3.00 <0.5 109.00 <0.5 1.14 0.50 <0.005 <5 <1 5.20 <0.05 <0.01 0.60 <0.01 17DZ-39-2 82.90 Ophi. 28.00 <0.5 94.00 <0.5 0.11 0.40 <0.005 <5 <1 4.80 <0.05 <0.01 0.30 0.01 17DZ-39-3 84.05 Ophi. 1.00 <0.5 101.00 <0.5 0.18 0.40 <0.005 <5 <1 8.90 <0.05 <0.01 0.20 0.01 17DZ-39-4 84.65 Ophi. 7.00 <0.5 127.00 <0.5 0.15 0.50 <0.005 <5 <1 10.20 <0.05 0.01 0.20 0.01 17DZ-41-2 89.07 Ophi. 15.00 <0.5 88.00 <0.5 1.52 0.60 <0.005 <5 <1 15.00 <0.05 <0.01 0.40 0.02 17DZ-43-1 94.26 Ophi. 4.00 <0.5 70.00 <0.5 0.11 0.40 <0.005 <5 <1 6.80 <0.05 <0.01 <0.2 <0.01 17DZ-43-4 96.28 Ophi. 12.00 <0.5 48.00 <0.5 0.20 0.40 <0.005 <5 <1 2.90 0.05 <0.01 <0.2 0.01 17DZ-43-5 97.16 Ophi. 4.00 <0.5 41.00 <0.5 0.16 0.40 <0.005 <5 <1 3.20 <0.05 <0.01 0.20 0.02 17DZ-44-1 97.33 Ophi. 1.00 <0.5 46.00 <0.5 0.11 0.50 <0.005 <5 <1 5.90 <0.05 0.01 <0.2 0.01 17DZ-44-2A 98.38 Ophi. 1.00 <0.5 29.00 <0.5 0.02 0.20 <0.005 <5 <1 2.80 <0.05 <0.01 0.20 <0.01 151 Sample Depth Lith Cu Ag Zn Cd Hg Ga In Ge Sn As Sb Bi Se Te Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-44-2B 98.63 Tlc-Ophi. 3.00 <0.5 29.00 <0.5 0.07 0.30 <0.005 <5 <1 5.70 <0.05 0.01 0.20 0.02 17DZ-44-3A 98.91 Tlc-Ophi. <1 <0.5 46.00 <0.5 0.03 0.30 <0.005 <5 <1 6.70 <0.05 <0.01 <0.2 0.01 17DZ-44-3B 99.36 Tlc-Ophi. 2.00 <0.5 55.00 <0.5 0.05 0.30 <0.005 <5 <1 19.30 <0.05 <0.01 <0.2 <0.01 17DZ-44-4A 99.66 Tlc-Ophi. 7.00 <0.5 84.00 <0.5 0.14 0.40 <0.005 <5 <1 1.80 <0.05 <0.01 <0.2 <0.01 17DZ-44-4B 99.72 Tlc-Ophi. 1.00 <0.5 58.00 <0.5 0.07 0.40 <0.005 <5 <1 9.30 <0.05 <0.01 <0.2 0.01 17DZ-44-4C 99.81 Tlc-Ophi. 1.00 <0.5 48.00 0.50 0.08 0.30 <0.005 <5 <1 6.40 <0.05 <0.01 0.20 0.02 17DZ-44-4D 100.06 Tlc-Ophi. 1.00 <0.5 59.00 <0.5 0.01 0.30 <0.005 <5 <1 4.10 0.05 <0.01 <0.2 <0.01 17DZ-45-1A 100.23 Mgs-List. 4.00 <0.5 42.00 <0.5 0.12 0.20 <0.005 <5 <1 6.20 <0.05 <0.01 0.30 <0.01 17DZ-45-1B 100.37 Mgs-List. 11.00 <0.5 89.00 <0.5 3.07 0.80 <0.005 <5 <1 >250 0.62 <0.01 <0.2 0.02 17DZ-45-2 101.19 Mgs-List. 2.00 <0.5 149.00 0.60 0.28 0.50 <0.005 <5 <1 175.00 1.32 <0.01 0.30 0.03 17DZ-46-2 104.54 Mgs-List. 62.00 <0.5 101.00 1.20 3.36 0.40 <0.005 <5 <1 >250 46.00 0.03 0.30 0.01 17DZ-52-1 118.91 Mgs-List. 4.00 <0.5 99.00 <0.5 3.82 1.00 <0.005 <5 <1 17.40 0.82 0.01 <0.2 0.02 17DZ-53-3 123.58 Mgs-List. 12.00 <0.5 188.00 <0.5 0.06 2.00 0.01 <5 <1 40.10 0.12 <0.01 <0.2 0.01 17DZ-56-3 132.41 Mgs-List. 2.00 <0.5 321.00 <0.5 0.11 2.00 0.01 <5 <1 66.50 0.60 <0.01 0.30 <0.01 17DZ-60-3 141.61 Mgs-List. 2.00 <0.5 82.00 <0.5 1.03 1.60 0.01 <5 <1 5.50 0.40 <0.01 <0.2 0.02 17DZ-62-4 148.75 Mgs-List. 2.00 <0.5 53.00 <0.5 0.08 0.30 <0.005 <5 <1 0.70 0.09 <0.01 <0.2 0.01 17DZ-63-2 150.49 Mgs-List. 2.00 <0.5 111.00 <0.5 1.59 1.20 0.01 <5 <1 1.30 0.44 0.01 0.20 0.01 17DZ-67-3 163.20 Mgs-List. 2.00 <0.5 440.00 <0.5 0.14 1.30 <0.005 <5 <1 2.10 0.16 0.01 <0.2 0.01 17DZ-70-2 171.56 Mgs-List. 7.00 <0.5 190.00 <0.5 0.04 1.10 0.01 <5 <1 2.30 0.13 <0.01 <0.2 0.01 17DZ-72-2 177.53 Mgs-List. 2.00 <0.5 124.00 0.80 0.59 0.30 <0.005 <5 <1 1.70 0.62 <0.01 0.30 <0.01 17DZ-75-4 188.46 Mgs-List. 2.00 <0.5 129.00 <0.5 0.02 0.60 <0.005 <5 <1 1.30 1.61 <0.01 <0.2 <0.01 17DZ-77-1 192.35 Dol-List. <1 <0.5 92.00 0.50 0.02 0.50 0.01 <5 <1 17.80 2.43 <0.01 <0.2 0.02 152 Sample Depth Lith Cu Ag Zn Cd Hg Ga In Ge Sn As Sb Bi Se Te Units m ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm 17DZ-77-4 194.39 Dol-List. 2.00 <0.5 133.00 0.60 0.08 0.40 <0.005 <5 <1 2.20 6.25 <0.01 <0.2 0.01 17DZ-78-3 196.43 Dol-List. <1 <0.5 91.00 0.70 0.02 0.50 0.01 <5 <1 1.90 4.26 <0.01 <0.2 0.01 17DZ-82-3 202.94 Meta. 8.00 <0.5 182.00 0.80 0.02 30.60 0.02 <5 3.00 3.40 0.22 0.01 0.30 0.02 17DZ-101-2 245.09 Meta. 97.00 <0.5 111.00 <0.5 <0.005 20.50 0.02 <5 1.00 1.30 0.61 0.01 0.30 0.01 17DZ-112-2 278.18 Meta. 12.00 <0.5 73.00 <0.5 <0.005 15.60 0.02 <5 1.00 0.40 0.34 <0.01 <0.2 <0.01 17DZ-1-4 Surface Atlin Std. 2.00 <0.5 45.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 4.20 <0.05 0.01 0.40 0.01 17DZ1-3 Surface Atlin Srp. 1.00 <0.5 44.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 1.60 0.08 <0.01 <0.2 <0.01 17DZ-1-6 Surface Atlin Srp. 1.00 <0.5 41.00 <0.5 <0.005 <0.05 <0.005 0.01 <1 1.60 0.06 <0.01 <0.2 0.01 17DZ-1-8 Surface Atlin Srp. <1 <0.5 39.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 1.80 0.06 <0.01 <0.2 <0.01 17DZ-1-1 Surface Atlin Soap. 2.00 <0.5 39.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 0.30 0.07 <0.01 <0.2 0.01 17DZ-1-2 Surface Atlin Soap. 2.00 <0.5 38.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 0.50 0.06 0.01 <0.2 <0.01 17DZ-1-5 Surface Atlin Soap. 2.00 <0.5 38.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 0.30 0.06 <0.01 0.40 0.02 17DZ-1-7 Surface Atlin Soap. 2.00 <0.5 38.00 <0.5 <0.005 <0.05 <0.005 <0.01 <1 0.30 0.05 <0.01 0.20 0.02 153 Sample Depth Lith Cr Co Ni V Mo W Re Units m ppm ppm ppm ppm ppm ppm ppm 17DZ-8-3 10.46 Mgs-List. 1650.00 77.00 1575.00 40.00 1.00 1.00 0.00 17DZ-13-2 22.67 Mgs-List. 2350.00 82.00 1785.00 27.00 <1 <1 0.01 17DZ-17-4 32.56 Mgs-List. 1870.00 81.00 1665.00 19.00 1.00 <1 <0.001 17DZ-20-3 41.44 Mgs-List. 2090.00 91.00 1750.00 28.00 <1 1.00 0.00 17DZ-24-1 49.05 Dol-List. 2060.00 88.00 1855.00 65.00 <1 1.00 0.02 17DZ-26-2 55.46 Mgs-List. 1250.00 88.00 1090.00 12.00 1.00 1.00 <0.001 17DZ-26-3 56.67 Mgs-List. 2230.00 81.00 1715.00 31.00 <1 <1 <0.001 17DZ-27-2 58.30 Mgs-List. 1960.00 76.00 1520.00 38.00 1.00 <1 0.00 17DZ-34-1 71.50 Mgs-List. 1380.00 86.00 1320.00 14.00 1.00 1.00 <0.001 17DZ-37-2 77.24 Dol-List. 1130.00 35.00 661.00 <5 <1 1.00 0.00 17DZ-38-3 80.01 Mgs-List. 1930.00 91.00 1380.00 21.00 1.00 <1 <0.001 17DZ-38-4A 81.42 Ophi. 2570.00 98.00 1750.00 35.00 <1 1.00 0.00 17DZ-38-4B 81.47 Ophi. 2390.00 100.00 2340.00 39.00 <1 1.00 <0.001 17DZ-39-2 82.90 Ophi. 1550.00 86.00 1740.00 17.00 <1 <1 <0.001 17DZ-39-3 84.05 Ophi. 2400.00 103.00 2440.00 30.00 <1 <1 0.00 17DZ-39-4 84.65 Ophi. 2780.00 99.00 2070.00 30.00 <1 2.00 <0.001 17DZ-41-2 89.07 Ophi. 3250.00 96.00 2140.00 36.00 <1 <1 0.00 17DZ-43-1 94.26 Ophi. 2440.00 97.00 2300.00 20.00 <1 <1 0.00 17DZ-43-4 96.28 Ophi. 2330.00 107.00 2100.00 20.00 1.00 1.00 0.00 17DZ-43-5 97.16 Ophi. 2660.00 117.00 2160.00 30.00 1.00 <1 <0.001 17DZ-44-1 97.33 Ophi. 2800.00 106.00 2110.00 45.00 <1 1.00 <0.001 17DZ-44-2A 98.38 Ophi. 1870.00 86.00 1650.00 7.00 <1 1.00 <0.001 17DZ-44-2B 98.63 Tlc-Ophi. 1910.00 73.00 1785.00 15.00 1.00 <1 <0.001 17DZ-44-3A 98.91 Tlc-Ophi. 1720.00 83.00 1655.00 13.00 <1 1.00 <0.001 17DZ-44-3B 99.36 Tlc-Ophi. 2440.00 97.00 1920.00 27.00 <1 1.00 <0.001 17DZ-44-4A 99.66 Tlc-Ophi. 2070.00 92.00 1820.00 18.00 1.00 1.00 0.00 17DZ-44-4B 99.72 Tlc-Ophi. 2990.00 107.00 2400.00 24.00 <1 1.00 <0.001 17DZ-44-4C 99.81 Tlc-Ophi. 1400.00 67.00 1435.00 18.00 <1 1.00 <0.001 17DZ-44-4D 100.06 Tlc-Ophi. 1650.00 84.00 1935.00 17.00 <1 1.00 <0.001 17DZ-45-1A 100.23 Mgs-List. 1340.00 64.00 1125.00 <5 1.00 <1 <0.001 17DZ-45-1B 100.37 Mgs-List. 2100.00 63.00 1145.00 18.00 1.00 <1 0.00 154 Sample Depth Lith Cr Co Ni V Mo W Re Units m ppm ppm ppm ppm ppm ppm ppm 17DZ-45-2 101.19 Mgs-List. 2070.00 68.00 1050.00 27.00 <1 <1 <0.001 17DZ-46-2 104.54 Mgs-List. 1280.00 160.00 3950.00 21.00 <1 <1 0.00 17DZ-52-1 118.91 Mgs-List. 1580.00 62.00 904.00 35.00 1.00 2.00 0.00 17DZ-53-3 123.58 Mgs-List. 1930.00 57.00 939.00 34.00 <1 1.00 <0.001 17DZ-56-3 132.41 Mgs-List. 2110.00 56.00 1180.00 49.00 <1 1.00 <0.001 17DZ-60-3 141.61 Mgs-List. 1990.00 64.00 875.00 43.00 <1 1.00 <0.001 17DZ-62-4 148.75 Mgs-List. 1450.00 108.00 2880.00 <5 1.00 1.00 0.00 17DZ-63-2 150.49 Mgs-List. 1900.00 64.00 888.00 25.00 <1 1.00 <0.001 17DZ-67-3 163.20 Mgs-List. 1720.00 78.00 1520.00 34.00 1.00 1.00 <0.001 17DZ-70-2 171.56 Mgs-List. 2060.00 78.00 1755.00 40.00 1.00 44.00 0.00 17DZ-72-2 177.53 Mgs-List. 1100.00 89.00 1720.00 15.00 1.00 1.00 0.00 17DZ-75-4 188.46 Mgs-List. 2200.00 99.00 1635.00 21.00 <1 1.00 <0.001 17DZ-77-1 192.35 Dol-List. 610.00 53.00 1030.00 20.00 <1 1.00 <0.001 17DZ-77-4 194.39 Dol-List. 1860.00 75.00 1330.00 25.00 <1 1.00 0.00 17DZ-78-3 196.43 Dol-List. 800.00 65.00 1105.00 17.00 <1 <1 <0.001 17DZ-82-3 202.94 Meta. 80.00 30.00 76.00 195.00 1.00 2.00 <0.001 17DZ-101-2 245.09 Meta. 170.00 45.00 83.00 204.00 8.00 1.00 0.01 17DZ-112-2 278.18 Meta. 70.00 31.00 51.00 163.00 1.00 1.00 0.00 17DZ-1-4 Surface Atlin Std. 0.10 103.00 2220.00 39.00 <1 11.00 <0.001 17DZ1-3 Surface Atlin Srp. 0.06 104.00 2230.00 34.00 <1 49.00 <0.001 17DZ-1-6 Surface Atlin Srp. 0.10 94.00 2080.00 37.00 <1 48.00 <0.001 17DZ-1-8 Surface Atlin Srp. 0.08 87.00 1945.00 36.00 <1 47.00 <0.001 17DZ-1-1 Surface Atlin Soap. 2.52 99.00 2160.00 20.00 <1 51.00 0.00 17DZ-1-2 Surface Atlin Soap. 2.68 91.00 2050.00 23.00 <1 55.00 <0.001 17DZ-1-5 Surface Atlin Soap. 2.55 92.00 2140.00 20.00 <1 52.00 <0.001 17DZ-1-7 Surface Atlin Soap. 2.46 91.00 2040.00 21.00 <1 49.00 <0.001 155 A.7 Whole-rock stable carbon and oxygen isotopes Stable carbon and oxygen isotopes of carbonates in whole-rock powders determined by OA-ICOS. Sample Depth Lith Weight (mg) δ13C (VPDB) S.E. δ13C δ18O (VSMOW) S.E. δ18O 17DZ-8-3 10.46 Mgs-List. 7.70 -0.10 0.14 15.76 2.61 17DZ-13-2 22.67 Mgs-List. 7.30 -0.52 0.15 16.89 2.52 17DZ-17-4 32.56 Mgs-List. 8.20 -0.50 0.15 17.30 2.49 17DZ-20-3 41.44 Mgs-List. 7.40 -0.97 0.15 15.66 2.62 17DZ-24-1 49.05 Dol List. 6.70 -0.48 0.15 16.09 2.58 17DZ-26-2 55.46 Mgs-List. 7.40 -1.18 0.15 14.35 2.73 17DZ-26-3 56.67 Mgs-List. 7.90 -1.57 0.09 18.11 1.05 17DZ-27-2 58.30 Mgs-List. 7.80 -0.07 0.14 17.91 2.45 17DZ-34-1 71.50 Mgs-List. 7.70 -0.57 0.15 13.27 2.84 17DZ-37-2 77.24 Dol List. 9.90 0.13 0.14 20.77 2.30 17DZ-38-3 80.01 Mgs-List. 9.60 -3.44 0.15 13.61 2.80 17DZ-38-4A 81.42 Ophi. 7.90 -3.76 0.16 15.29 2.65 17DZ-38-4B 81.47 Ophi. 16.00 -4.56 0.16 14.91 2.68 17DZ-39-2 82.90 Ophi. 33.00 -6.81 0.13 15.89 1.16 17DZ-39-3 84.05 Ophi. 38.40 -7.02 0.17 19.52 2.36 17DZ-39-4 84.65 Ophi. 23.60 -7.00 0.17 15.20 2.66 17DZ-41-2 89.07 Ophi. 64.40 -7.33 0.17 17.66 2.47 17DZ-43-1 94.26 Ophi. 55.40 -1.54 0.20 14.78 2.70 17DZ-43-4 96.28 Ophi. 36.60 -2.61 0.15 19.25 2.37 17DZ-43-5 97.16 Ophi. 38.30 -3.24 0.15 16.94 2.52 17DZ-44-1 97.33 Ophi. 37.50 -3.15 0.15 17.23 2.50 17DZ-44-2A 98.38 Tlc-Ophi. 12.30 -4.14 0.16 16.15 2.58 17DZ-44-2B 98.63 Tlc-Ophi. 17.60 -4.46 0.16 16.41 2.56 17DZ-44-3A 98.91 Tlc-Ophi. 12.70 -4.89 0.12 16.05 1.15 17DZ-44-3B 99.36 Tlc-Ophi. 12.70 -4.13 0.13 17.94 0.86 17DZ-44-4A 99.66 Tlc-Ophi. 15.50 -4.19 0.11 14.94 1.22 17DZ-44-4B 99.72 Tlc-Ophi. 12.30 -4.33 0.11 17.01 1.10 156 Sample Depth Lith Weight (mg) δ13C (VPDB) S.E. δ13C δ18O (VSMOW) S.E. δ18O 17DZ-44-4C 99.81 Tlc-Ophi. 11.90 -3.63 0.10 16.77 1.11 17DZ-44-4D 100.06 Tlc-Ophi. 8.70 -3.21 0.10 18.60 1.03 17DZ-45-1A 100.23 Mgs-List. 7.00 -2.37 0.09 16.18 1.15 17DZ-45-1B 100.37 Mgs-List. 9.00 -3.14 0.10 14.24 1.26 17DZ-45-2 101.19 Mgs-List. 7.00 -1.34 0.09 18.09 1.05 17DZ-46-2 104.54 Mgs-List. 7.00 -0.04 0.08 16.45 1.13 17DZ-52-1 118.91 Mgs-List. 7.80 -0.10 0.08 13.10 1.33 17DZ-53-3 123.58 Mgs-List. 7.50 -1.10 0.09 13.84 1.28 17DZ-53-3 (Dup) 132.41 Mgs-List. 7.90 -0.98 0.09 16.61 1.12 17DZ-60-3 141.61 Mgs-List. 6.70 0.21 0.08 15.92 1.16 17DZ-62-4 148.75 Mgs-List. 6.60 0.08 0.08 15.93 1.16 17DZ-63-2 150.49 Mgs-List. 7.30 -0.72 0.08 16.71 1.12 17DZ-67-3 163.20 Mgs-List. 6.80 -0.36 0.08 15.21 1.20 17DZ-70-2 171.56 Mgs-List. 7.00 -0.14 0.08 15.86 1.16 17DZ-72-2 177.53 Mgs-List. 7.60 -0.99 0.09 16.97 1.10 17DZ-75-4 188.46 Mgs-List. 7.40 -3.92 0.13 15.37 0.94 17DZ-77-1 192.35 Dol List. 6.10 -0.05 0.08 21.20 0.94 17DZ-77-4 194.39 Dol List. 6.60 -1.56 0.09 19.93 0.98 17DZ-78-3 196.43 Dol List. 7.10 -0.67 0.09 21.84 0.92 17DZ-82-3 202.94 Meta. 77.10 1.73 0.08 18.81 1.02 17DZ-112-2 278.18 Meta. 21.00 0.59 0.12 20.54 0.81 157 A.8 Electron microprobe analysis of carbonates Geochemistry of carbonates determined by EMPA analysis. Approximate location of EMPA analyses on thin sections. Circles Labeled C1,2,3… correspond to C1,2,3… in EMPA analysis labels. Label# Min. MgO (wt.%) CaO (wt.%) MnO (wt.%) FeO ( wt.%) CO2 (wt.%) * Total 17-4-C5-1 Dol 19.25 29.63 0.13 3.88 46.73 99.62 17-4-C5-1 Dol 19.20 29.98 0.10 3.69 46.82 99.80 17-4-C5-2 Mgs 44.30 0.24 0.04 3.87 51.15 99.77 17-4-C5-2 Mgs 45.17 0.69 0.00 2.97 50.93 99.08 17-4-C1-1 Mgs 44.95 0.22 0.05 3.41 51.96 101.12 17-4-C1-1 Mgs 45.54 0.14 0.00 3.69 51.40 100.13 17-4-C1-1 Mgs 45.54 0.08 0.06 3.48 51.06 99.39 17-4-C1-1 Mgs 44.55 0.18 0.00 3.65 50.97 99.31 17-4-C1-2 Mgs 45.09 0.14 0.05 3.53 51.25 99.78 17-4-C1-2 Mgs 44.85 0.21 0.00 3.55 51.61 100.49 17-4-C1-3 Mgs 44.65 0.15 0.12 3.76 51.51 100.42 17-4-C1-4 Mgs 44.49 0.26 0.03 3.72 51.49 100.37 17-4-C1-5 Dol 22.31 27.53 0.00 2.70 47.62 100.16 17-4-C1-7 Dol 18.95 30.36 0.04 3.58 46.74 99.68 17-4-C1-7 Dol 19.75 30.11 0.02 2.98 47.04 99.90 158 Label# Min. MgO (wt.%) CaO (wt.%) MnO (wt.%) FeO ( wt.%) CO2 (wt.%) * Total 17-4-C1-8 Dol 19.56 29.92 0.02 3.07 46.73 99.30 17-4-C1-8 Dol 19.67 30.23 0.00 2.95 47.02 99.87 17-4-C1-9 Dol 19.66 29.81 0.00 2.86 46.62 98.96 17-4-C1-9 Dol 18.49 29.82 0.00 4.54 46.37 99.22 17-4-C2-3 Mgs 45.00 0.08 0.01 3.39 51.94 101.02 17-4-C3-1 Mgs 43.83 0.16 0.02 5.63 50.48 99.24 17-4-C3-4 Mgs 45.11 0.22 0.04 3.75 51.49 100.36 17-4-C3-4 Mgs 44.75 0.19 0.00 3.65 51.19 99.74 17-4-C3-5 Mgs 44.92 0.21 0.03 2.66 50.89 98.73 17-4-C3-5 Mgs 44.82 0.17 0.05 3.49 52.02 101.27 17-4-C3-5 Mgs 45.60 0.18 0.00 2.92 51.65 100.29 17-4-C3-6 Mgs 44.74 0.18 0.00 3.76 51.10 99.59 17-4-C3-6 Mgs 45.37 0.13 0.04 2.75 51.06 99.08 17-4-C4-1 Mgs 45.10 0.07 0.00 3.99 51.25 99.95 17-4-C4-1 Mgs 45.07 0.06 0.00 4.30 51.26 100.12 17-4-C4-3 Mgs 44.74 0.10 0.03 3.69 51.50 100.33 39-4-C2-1 Mgs 44.90 0.19 0.00 3.80 51.85 101.06 39-4-C2-3 Mgs 44.71 0.19 0.01 3.96 51.79 101.02 39-4-C2-7 Mgs 44.89 0.23 0.00 3.39 51.43 100.09 39-4-C2-8 Mgs 44.86 0.13 0.00 3.89 51.74 100.86 39-4-C2-8 Mgs 45.26 0.17 0.00 3.63 51.84 100.95 39-4-C2-8 Mgs 45.26 0.12 0.01 3.64 51.20 99.73 39-4-C3-1 Mgs 44.84 0.05 0.00 3.82 51.43 100.22 39-4-C3-3 Dol 21.41 30.19 0.04 0.69 47.52 99.85 39-4-C3-4 Mgs 44.98 0.49 0.02 3.12 51.25 99.71 39-4-C4-1 Mgs 45.60 0.10 0.00 3.29 51.88 100.87 39-4-C4-2 Mgs 45.57 0.40 0.00 3.07 51.05 99.26 39-4-C4-4 Dol 22.03 29.82 0.00 0.60 47.83 100.27 39-4-C4-5 Dol 21.44 30.10 0.04 0.61 47.43 99.61 39-4-C4-6 Dol 21.84 29.79 0.00 0.67 47.63 99.92 39-4-C4-7 Dol 21.34 29.93 0.00 0.66 47.19 99.12 39-4-C5-1 Dol 22.58 28.41 0.00 0.59 47.32 98.89 159 Label# Min. MgO (wt.%) CaO (wt.%) MnO (wt.%) FeO ( wt.%) CO2 (wt.%) * Total 39-4-C5-3 Mgs 45.50 0.10 0.00 3.53 51.68 100.58 39-4-C5-4 Mgs 44.73 0.04 0.00 3.64 51.51 100.29 39-4-C5-5 Mgs 45.01 0.15 0.02 3.08 51.23 99.54 39-4-C5-6 Mgs 45.93 0.12 0.00 3.22 51.91 100.89 39-4-C5-7 Mgs 44.90 0.13 0.00 3.71 52.03 101.35 39-4-C6-1 Mgs 45.34 0.20 0.00 3.42 50.71 98.71 39-4-C6-2 Dol 22.05 29.86 0.00 0.62 47.89 100.41 39-4-C6-3 Dol 21.36 30.51 0.05 0.51 47.61 100.03 43-5-C1-1 Dol 24.12 26.21 0.02 0.78 47.40 98.54 43-5-C1-2 Dol 23.27 26.59 0.00 1.80 47.39 99.05 43-5-C1-2 Dol 22.02 29.62 0.00 0.72 47.73 100.09 43-5-C1-3 Dol 23.03 27.64 0.00 0.83 47.35 98.86 43-5-C1-3 Dol 21.61 29.70 0.01 0.51 47.23 99.06 43-5-C1-4 Dol 25.09 25.08 0.00 1.35 47.90 99.42 43-5-C5-1 Dol 21.77 28.52 0.00 2.07 47.42 99.77 43-5-C5-1 Dol 22.54 26.99 0.00 2.07 47.06 98.65 43-5-C5-2 Dol 23.22 26.44 0.00 1.95 47.30 98.91 43-5-C5-2 Dol 22.34 27.52 0.04 1.90 47.18 98.98 43-5-C5-2 Dol 22.36 28.17 0.00 1.90 47.69 100.12 43-5-C5-3 Dol 22.04 28.18 0.08 1.84 47.36 99.50 43-5-C5-3 Dol 22.27 27.40 0.00 2.00 47.05 98.73 43-5-C6-2 Dol 20.34 29.53 0.02 2.33 46.82 99.04 43-5-C6-3 Dol 20.50 29.91 0.02 1.94 47.06 99.42 44-4B-C1-1 Mgs 44.13 0.41 0.06 5.08 51.66 101.34 44-4B-C1-1 Mgs 41.16 0.97 0.04 7.91 50.58 100.66 44-4B-C1-1 Mgs 45.14 0.47 0.00 2.76 51.35 99.72 44-4B-C1-4 Dol 20.40 30.02 0.02 1.90 47.02 99.36 44-4B-C1-4 Dol 20.21 29.76 0.04 2.15 46.77 98.93 44-4B-C1-4 Dol 20.60 30.26 0.03 2.12 47.56 100.56 44-4B-C1-4 Dol 20.31 30.08 0.00 2.02 47.02 99.43 44-4B-C1-4 Dol 20.29 29.98 0.00 1.96 46.88 99.11 44-4B-C1-4 Dol 19.74 30.24 0.02 2.72 46.96 99.68 160 Label# Min. MgO (wt.%) CaO (wt.%) MnO (wt.%) FeO ( wt.%) CO2 (wt.%) * Total 44-4B-C1-4 Dol 20.45 29.87 0.02 2.12 47.08 99.54 44-4B-C1-4 Dol 19.83 30.52 0.00 2.43 47.09 99.87 44-4B-C2-2 Dol 20.21 29.81 0.00 2.58 47.04 99.64 44-4B-C2-2 Dol 20.00 29.80 0.06 2.67 46.89 99.42 44-4B-C2-4 Dol 19.88 29.74 0.00 2.69 46.69 99.00 44-4B-C2-4 Dol 20.25 29.41 0.00 2.61 46.80 99.06 44-4B-C2-4 Dol 19.94 29.54 0.03 2.73 46.65 98.88 44-4B-C2-7 Mgs 40.09 0.10 0.02 10.50 50.29 101.00 44-4B-C2-7 Mgs 40.12 0.19 0.00 9.97 50.07 100.35 44-4B-C2-7 Mgs 41.09 0.08 0.00 9.45 50.72 101.34 44-4B-C3-1 Dol 20.20 29.70 0.00 2.06 46.62 98.57 44-4B-C3-1 Dol 20.23 29.33 0.07 2.44 46.65 98.72 44-4B-C3-2 Dol 20.30 29.82 0.00 2.26 46.96 99.34 44-4B-C3-2 Dol 20.09 29.84 0.00 2.45 46.85 99.23 44-4B-C3-3 Dol 19.49 30.06 0.04 3.26 46.90 99.76 44-4B-C3-3 Dol 20.15 30.25 0.00 2.90 47.52 100.82 44-4B-C3-4 Dol 19.91 29.78 0.00 2.81 46.84 99.34 44-4B-C3-4 Dol 19.68 29.73 0.03 2.86 46.59 98.89 44-4B-C3-5 Dol 19.87 29.78 0.01 2.51 46.61 98.78 44-4B-C3-5 Dol 20.36 30.02 0.00 2.36 47.24 99.98 44-4B-C3-5 Dol 20.06 29.93 0.01 2.47 46.91 99.38 44-4B-C4-1 Dol 19.84 30.21 0.03 2.82 47.13 100.04 44-4B-C4-1 Dol 19.90 29.82 0.04 2.93 46.96 99.65 44-4B-C4-1 Dol 19.85 29.69 0.01 2.65 46.60 98.80 44-4B-C4-1 Dol 20.32 29.88 0.02 2.22 47.01 99.44 44-4B-C4-2 Dol 20.48 29.80 0.00 2.38 47.21 99.86 44-4B-C4-2 Dol 20.35 30.33 0.03 2.34 47.48 100.53 44-4B-C4-2 Dol 20.41 30.10 0.00 1.98 47.13 99.62 44-4B-C4-2 Dol 20.08 29.98 0.00 2.63 47.06 99.75 44-4B-C4-2 Dol 20.30 29.97 0.02 2.59 47.29 100.17 44-4B-C4-3 Mgs 42.74 0.35 0.01 5.67 50.42 99.19 44-4B-C4-3 Mgs 42.93 0.43 0.00 5.76 50.74 99.86 161 Label# Min. MgO (wt.%) CaO (wt.%) MnO (wt.%) FeO ( wt.%) CO2 (wt.%) * Total 44-4B-C4-4 Mgs 44.67 1.00 0.00 2.21 50.91 98.78 44-4B-C4-4 Mgs 45.13 0.90 0.00 2.33 51.42 99.78 44-4B-C4-4 Mgs 44.24 0.70 0.03 3.77 51.18 99.91 44-4B-C4-4 Mgs 44.59 0.90 0.03 2.23 50.78 98.54 44-4B-C4-7 Dol 21.07 29.48 0.00 1.44 47.03 99.04 44-4B-C4-7 Dol 21.16 29.36 0.01 1.47 47.06 99.06 44-4B-C4-7 Dol 21.12 30.29 0.01 1.17 47.56 100.16 44-4B-C5-1 Mgs 44.42 0.95 0.01 3.00 51.09 99.47 44-4B-C5-1 Mgs 44.40 1.12 0.00 3.52 51.52 100.56 44-4B-C5-1 Mgs 44.83 0.71 0.00 2.83 51.24 99.60 44-4B-C5-1 Mgs 43.98 1.21 0.01 3.36 51.04 99.61 44-4B-C5-2 Mgs 45.00 1.10 0.01 2.15 51.32 99.59 44-4B-C5-2 Mgs 44.35 1.73 0.00 2.27 51.17 99.52 44-4B-C5-2 Mgs 45.66 0.34 0.01 1.96 51.33 99.31 44-4B-C5-3 Mgs 45.20 0.22 0.00 2.55 51.10 99.07 44-4B-C5-3 Mgs 45.70 0.19 0.00 2.50 51.58 99.96 44-4B-C5-3 Mgs 45.31 0.23 0.00 2.65 51.28 99.47 44-4B-C5-4 Dol 20.84 28.71 0.06 3.05 47.20 99.86 44-4B-C5-5 Dol 20.61 29.19 0.01 3.25 47.41 100.47 44-4B-C5-5 Dol 20.54 29.80 0.01 2.22 47.18 99.74 44-4B-C6-4 Mgs 44.43 0.32 0.00 3.36 50.83 98.94 # multiple analysis of the same mineral grain conducted to investigate heterogeneity and zoning. * CO2 determined by stoichiometry162 A.9 Quantitative mineralogy from microdrill Quantitative mineralogy determined by Rietveld analysis of XRD patterns obtained from microdrill powders. Label* Depth (m) Qtz Mgs Dol ZnCO3 Cal Tlc Srp Hem Mag Brt Ms Vrm Prh Chl Act Epi Total 17DZ-13-2(1) 22.67 8 92 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-13-2(2) 22.67 12 88 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-13-2(3) 22.67 6 91 3 0 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-26-2(1) 55.46 9 88 2 0 0 0 0 1 0 0 0 0 0 0 0 0 100 17DZ-26-2(2) 55.46 8 79 1 0 0 0 0 1 0 0 0 11 0 0 0 0 100 17DZ-26-2(3) 55.46 7 89 1 0 0 0 0 3 0 0 0 0 0 0 0 0 100 17DZ-37-2(1) 77.24 8 8 70 0 0 0 0 0 0 14 0 0 0 0 0 0 100 17DZ-37-2(2) 77.24 51 9 38 0 0 0 0 0 0 2 0 0 0 0 0 0 100 17DZ-39-3 (1) 84.65 27 17 17 0 0 0 34 0 5 0 0 0 0 0 0 0 100 17DZ-39-3 (2) 84.65 3 24 5 0 0 0 65 0 3 0 0 0 0 0 0 0 100 17DZ-39-3 (3) 84.65 0 63 5 0 0 0 32 0 0 0 0 0 0 0 0 0 100 17DZ-43-4 (1) 96.28 1 1 12 0 0 0 78 0 8 0 0 0 0 0 0 0 100 17DZ-43-4 (2) 96.28 5 34 45 0 0 0 16 0 0 0 0 0 0 0 0 0 100 17DZ-44-2A (1) 98.38 17 51 3 0 0 0 29 0 0 0 0 0 0 0 0 0 100 17DZ-44-4C (1) 99.81 3 43 1 0 0 20 33 0 0 0 0 0 0 0 0 0 100 17DZ-44-4C (2) 99.81 6 33 2 0 0 9 50 0 0 0 0 0 0 0 0 0 100 17DZ-44-2A (2) 98.38 1 11 5 0 0 4 79 0 0 0 0 0 0 0 0 0 100 17DZ-44-4C (3) 99.81 3 1 60 0 0 5 31 0 0 0 0 0 0 0 0 0 100 17DZ-44-4D (1) 100.06 0 42 44 0 0 4 10 0 0 0 0 0 0 0 0 0 100 17DZ-44-4D (2) 100.06 21 44 7 0 0 4 24 0 0 0 0 0 0 0 0 0 100 17DZ-46-2 (1) 100.37 29 3 66 2 0 0 0 0 0 0 0 0 0 0 0 0 100 163 Label* Depth (m) Qtz Mgs Dol ZnCO3 Cal Tlc Srp Hem Mag Brt Ms Vrm Prh Chl Act Epi Total 17DZ-46-2 (2) 100.37 9 2 86 2 0 0 0 1 0 0 0 0 0 0 0 0 100 17DZ-62-4 (1) 148.75 5 89 1 0 0 0 0 5 0 0 0 0 0 0 0 0 100 17DZ-62-4 (2) 148.75 2 95 2 0 0 0 0 1 0 0 0 0 0 0 0 0 100 17DZ-62-4 (3) 148.75 46 52 0 0 0 0 0 2 0 0 0 0 0 0 0 0 100 17DZ-67-3 (1) 163.20 3 95 1 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-67-3 (2) 163.20 26 71 2 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-67-3(3) 163.20 2 95 2 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-72-2 (1) 177.53 28 45 18 3 0 0 0 0 0 0 0 0 6 0 0 0 100 17DZ-72-2 (2) 177.53 12 81 5 1 0 0 0 0 0 0 0 0 1 0 0 0 100 17DZ-75-4 (1) 188.46 2 87 10 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-75-4 (2) 188.46 7 81 11 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-75-4 (2) 188.46 7 81 12 0 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-75-4 (3) 188.46 7 81 11 1 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-77-1A (1) 192.35 1 3 94 2 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-77-1B (1) 192.35 6 0 93 0 0 0 0 1 0 0 0 0 0 0 0 0 100 17DZ-77-1B (2) 192.35 18 7 71 0 0 0 0 4 0 0 0 0 0 0 0 0 100 17DZ-77-4 (1) 194.39 0 1 99 0 0 0 0 0 0 0 0 0 0 0 0 0 100 17DZ-77-4 (2) 194.39 8 47 43 0 0 0 0 2 0 0 0 0 0 0 0 0 100 17DZ-82-3 (1) 278.18 0 0 0 0 99 0 0 0 0 0 1 0 0 0 0 0 100 17DZ-112-2 (1) 278.18 0 0 0 0 95 0 0 0 0 0 0 0 0 1 2 2 100 17DZ-112-2 (2) 278.18 0 0 0 0 96 0 0 0 0 0 1 0 0 1 1 1 100 17DZ-112-2 (3) 278.18 0 0 0 0 97 0 0 0 0 0 1 0 0 1 1 0 100 * Numbers in brackets correspond to microdrill holes in TSB (see A.1) 164 A.10 Stable carbon and oxygen isotopes from microdrill Stable Carbon and Oxygen Isotopes of carbonates in microdrill powders determined by OA-ICOS. Molar ratios of carbonates are also presented to compare isotope values with carbonate type. Sample* Depth (m) Lith. Feature XMgs# XDol # XZnCO3# XCal# δ13C (VPDB) S.E. δ13C δ18O (VSMOW) S.E. δ18O 17DZ-44-4C (2) 99.81 Tlc Ophi. mgs matrix 0.97 0.03 0.00 0.00 -4.19 0.25 13.70 0.39 17DZ-44-4D (1) 100.06 Tlc Ophi. mgs matrix 0.68 0.32 0.00 0.00 -3.41 0.08 16.94 0.27 17DZ-44-4D (2) 100.06 Tlc Ophi. mgs matrix 0.93 0.07 0.00 0.00 -3.52 0.25 14.81 0.39 17DZ-13-2 (2) 22.67 List. mgs matrix 1.00 0.00 0.00 0.00 -1.77 0.08 14.87 0.27 17DZ-13-2 (3) 22.67 List. mgs matrix 0.99 0.01 0.00 0.00 -0.65 0.08 15.72 0.27 17DZ-26-2 (3) 55.46 List. mgs matrix 0.99 0.01 0.00 0.00 -0.40 0.08 15.92 0.27 17DZ-75-4 (1) 188.46 List. mgs matrix 0.94 0.05 0.01 0.00 -4.45 0.25 12.28 0.39 17DZ-75-4 (2) 188.46 List. mgs matrix 0.93 0.06 0.01 0.00 -4.16 0.25 13.02 0.39 17DZ-77-4 (2) 194.39 List. mgs matrix 0.71 0.29 0.00 0.00 -0.35 0.08 19.08 0.27 17DZ-26-2 (1) 55.46 List. mgs vein 0.99 0.01 0.00 0.00 0.84 0.08 14.08 0.27 17DZ-26-2 (2) 55.46 List. mgs vein 0.99 0.01 0.00 0.00 0.52 0.08 11.73 0.27 17DZ-62-4 (1) 148.75 List. mgs vein 0.99 0.01 0.00 0.00 0.83 0.08 10.03 0.27 17DZ-62-4 (2) 148.75 List. mgs vein 0.99 0.01 0.00 0.00 1.50 0.08 10.50 0.27 17DZ-67-3 (1) 163.20 List. mgs vein 0.99 0.00 0.01 0.00 2.12 0.08 11.26 0.27 17DZ-67-3 (3) 163.20 List. mgs vein 0.98 0.01 0.01 0.00 0.20 0.25 11.78 0.39 17DZ-72-2 (1) 177.53 List. mgs vein 0.81 0.15 0.04 0.00 -0.84 0.25 12.55 0.39 17DZ-46-2 (1) 104.54 List. dol matrix 0.09 0.87 0.04 0.00 0.44 0.08 21.95 0.27 17DZ-77-1B (2) 192.35 List. dol matrix 0.18 0.82 0.00 0.00 -0.10 0.25 23.12 0.39 165 Sample* Depth (m) Lith. Feature XMgs# XDol # XZnCO3# XCal# δ13C (VPDB) S.E. δ13C δ18O (VSMOW) S.E. δ18O 17DZ-37-2 (1) 77.24 List. dol vein 0.20 0.80 0.00 0.00 0.46 0.08 23.26 0.27 17DZ-46-2 (2) 104.54 List. dol vein 0.05 0.92 0.03 0.00 0.22 0.08 17.60 0.27 17DZ-77-1A (1) 192.35 List. dol vein 0.06 0.91 0.03 0.00 0.52 0.25 25.88 0.39 17DZ-77-1B (1) 192.35 List. dol vein 0.00 1.00 0.00 0.00 0.28 0.25 23.77 0.39 17DZ-82-3 (1) 202.94 Meta. cal vein 0.00 0.00 0.00 1.00 2.63 0.08 17.91 0.27 17DZ-112-2 (1) 278.18 Meta. cal vein 0.00 0.00 0.00 1.00 1.20 0.08 17.44 0.27 17DZ-112-2 (3) 278.18 Meta. cal vein 0.00 0.00 0.00 1.00 2.21 0.08 16.76 0.27 * Numbers in brackets correspond to microdrill holes in TSB (see A.1) # molar ratio of each carbonate in reference to the total carbonate present in each sample, calculated using quantitative XRD data in A.9.
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Carbonation of the Oman Ophiolite during subduction and emplacement
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