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Are there Colombian-type emeralds in Canada's Northern Cordillera? Insights from regional silt geochemistry,… Lake, Donald John 2017

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  ARE THERE COLOMBIAN-TYPE EMERALDS IN CANADA’S NORTHERN CORDILLERA? Insights from regional silt geochemistry, and the genesis of emerald at Lened, NWT   by Donald John Lake    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) November 2017 © Donald John Lake, 2017     ii Abstract The unusual black shale hosted emerald deposits of Colombia are an important source of the finest quality emeralds. The majority of world emerald deposits are related to granite pegmatites and metamorphic environments, however Colombian-type emerald is amagmatic and is associated with sedimentary-hydrothermal brines of largely evaporitic origin where the key emerald-forming elements are remobilized from black shale during regional compressional tectonism. The valuable gem quality mineralization of Colombian emerald deposits is so far unique, however the basic geological conditions that led to mineralization may not be as unusual. Similar black shale basins hosting evaporites are found worldwide, and could be prospective for Colombian-type emerald mineralization. Canada’s Selwyn Basin and periphery is one similar setting with the distinction of hosting two interesting beryl showings: the Mountain River Beryl (a variation of the Colombian beryl model) and the Lened emerald showing (in which black shale provided vanadium as an emerald chromophore). This thesis presents the results of applying Colombian-type emerald exploration criteria to Selwyn Basin stream sediment geochemistry data, in addition to clarifying the origin of emerald at the Lened showing located within the Selwyn Basin. We identified several prospective areas in Selwyn basin for further Colombian-type emerald exploration based on Na, K, Be, Cr/V, and rare earth element values, however there are important caveats regarding analytical techniques and the regional nature of silt sampling. We found that Lened is a unique skarn-hosted hydrothermal emerald occurrence (~100 Ma) in which Be was provided by a nearby granite pluton of similar age. The chromophore V was provided by local black shale/mudstone.     iii Lay Summary Colombian emerald forms in a black shale sedimentary environment unlike other places where emerald is typically of igneous origin. I summarized the deposit model for Colombian-type emerald, and its exploration criteria. Northern Canada has vast areas of black shales similar to Colombia and two emerald occurrences in Canada have commonalities with Colombian emerald. I analyzed geochemical data using methods from Colombia to identify areas to prospect for emerald in the Yukon and Northwest Territories (NWT). I also studied the origin of emerald at Lened, NWT which is of particular interest because emerald-forming elements came from black shale. I found that Lened is a unique skarn-hosted hydrothermal vein emerald occurrence wherein the necessary elements for emerald were sourced from a nearby granitic intrusion and local black shale. All available evidence suggests there may be potential for Colombian-type emerald in Canada’s North.     iv Preface This dissertation is based on a concept formed by my supervisor (Dr. Lee Groat) and myself. Fieldwork and sample collection was done by myself, and Dr. Groat unless stated otherwise. Whole rock geochemical analyses and thin section photos for Lened were provided by Hendrik Falck of the Northwest Territories Geological Survey. Hydrogen isotope analysis of Lened emerald was provided by Dr. Gaston Giuliani who also edited a version of the Lened chapter. Stable isotope analyses for Lened were interpreted with the help of Dr. Daniel Kontak. Dr. Jan Cempírek provided laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses and Raman spectra for Lened emerald in addition to writing the interpretation of the Raman spectra and providing helpful ideas and edits on the mineral chemistry section. Dr. Daniel Marshall edited a version of the Lened chapter and provided helpful commentary. Thomas Mulja provided an outline for the description of Lened pluton and skarn, as well as electron probe microanalysis (EPMA) data for skarn minerals. I interpreted the data for presentation in this dissertation. Dr. Mostafa Fayek provided boron isotope analyses of Lened tourmaline. Dr. Groat edited the thesis, provided advice and ideas, and helped interpret data. A version of the Lened chapter of this thesis has been published with co-authors Lee Groat, Hendrik Falck, Thomas Mulja, Jan Cempírek, Daniel Kontak, Daniel Marshall, Gaston Giuliani, and Mostafa Fayek in the July 2017 issue of The Canadian Mineralogist.    v Table of Contents Abstract ......................................................................................................................... ii!Lay Summary ............................................................................................................... iii!Preface .......................................................................................................................... iv!Table of Contents .......................................................................................................... v!List of Tables ............................................................................................................... vii!List of Figures ............................................................................................................. vii!List of Abbreviations ..................................................................................................... x!Acknowledgements ...................................................................................................... xi!Dedication ................................................................................................................... xii! 1 – Introduction ............................................................................................................. 1 1.1! EMERALD ................................................................................................... 2!1.2! COLOMBIAN EMERALD ............................................................................... 3!1.3! GENETIC MODEL ......................................................................................... 6!1.4! WHY EXPLORE FOR COLOMBIAN-TYPE EMERALD IN CANADA? .................. 10!1.5! KNOWN EMERALD DEPOSITS OF CANADA’S NORTHERN CORDILLERA ........ 11!1.5.1! Tsa Da Glisza ............................................................................................ 11!1.5.2! Mountain River Beryl ................................................................................ 11!1.5.3! Lened ......................................................................................................... 12!2 – Exploring for Colombian-type Emerald ............................................................... 13!2.1! TECHNIQUES USED IN COLOMBIA .............................................................. 13!2.2! APPLICATION OF TECHNIQUES TO NORTHERN CANADA .............................. 15!2.3! METHODS ................................................................................................. 16!2.4! RESULTS ................................................................................................... 18!2.4.1! Field Assessments ..................................................................................... 19!2.5! DISCUSSION .............................................................................................. 20!2.5.1! Limitations ................................................................................................. 20!2.5.2! Suggested emerald prospecting techniques ............................................... 21!3 – Origin of Emerald at Lened, NWT ....................................................................... 23!3.1! INTRODUCTION ......................................................................................... 23!3.2! LOCAL GEOLOGY ...................................................................................... 24!3.2.1! Sedimentary Rock ..................................................................................... 24!3.2.2! Lened Pluton .............................................................................................. 25!3.2.3! Skarn .......................................................................................................... 26!3.2.4! Folding and Faulting ................................................................................. 28! vi 3.3! ANALYTICAL PROCEDURES ....................................................................... 28!3.4! EMERALD-BEARING QUARTZ-CARBONATE VEINS ...................................... 31!3.5! CHEMISTRY OF VEIN MINERALS ................................................................ 33!3.5.1! Beryl .......................................................................................................... 33!3.5.2! Tourmaline ................................................................................................ 35!3.5.3! Dioctahedral mica ...................................................................................... 35!3.5.4! Stable isotope analyses of O-H-C-B ......................................................... 36!3.5.5! Whole-rock geochemistry ......................................................................... 36!3.6! 40AR/39AR GEOCHRONOLOGY OF THE GRANITE AND EMERALD VEIN .......... 38!3.7! DISCUSSION .............................................................................................. 38!3.7.1! Age of the Lened pluton and the emerald-bearing veins ........................... 39!3.7.2! Muscovite chemistry and vein formation temperature .............................. 40!3.7.3! Equilibration temperature and inferred !18OH2O of magmatic fluid .......... 40!3.7.4! Equilibration temperature of the veins ...................................................... 41!3.7.5! O, H stable isotopic composition of the vein-forming fluid ...................... 41!3.7.6! Vein emplacement ..................................................................................... 43!3.7.7! Sources of Be, B, and the origin of the emerald vein parental fluid ......... 43!3.7.8! V-rich sedimentary rock as a chromophore source ................................... 45!3.7.9! Conclusions ............................................................................................... 46!4 – Conclusions ........................................................................................................... 48!4.1! MAIN FINDINGS ........................................................................................ 48!4.2! LIMITATIONS ............................................................................................. 49!4.3! FUTURE WORK .......................................................................................... 49!Tables .......................................................................................................................... 51 Figures......................................................................................................................... 74!References ................................................................................................................. 106!Appendix A: Utah ..................................................................................................... 120!   vii List of Tables Table 1. Average and Representative Compositions of Skarn Minerals at Lened ..... 51 Table 2. Average Compositions of Emerald Samples from Lened Quartz Veins ...... 54 Table 3. Selected Compositions of Tourmaline from Lened Quartz Veins ............... 56 Table 4. Average Compositions of Muscovite Samples from Lened ........................ 58 Table 5. Oxygen and Carbon Isotope Compositions .................................................. 60 Table 6. Boron Isotope Compositions of Lened Tourmaline (δ11B) ......................... 62 Table 7. Geochemistry of Lened Granites, Skarns, and Black Shales ....................... 63 Table 8. Geochemistry of Secondary Rock Types at Lened ...................................... 67 Table 9. 40Ar/39Ar Age Data (DM-02-05 Lened Granite Biotite) .............................. 70 Table 10. 40Ar/39Ar Age Data (DM-02-07 Lened Granite Biotite) ............................ 71 Table 11. 40Ar/39Ar Age Data (HF-22 Vein Muscovite) ............................................ 72 Table 12. 40Ar/39Ar Age Data (HF-22B Vein Muscovite) ......................................... 73    viii List of Figures Figure 1: Schematic representation of the beryl structure projected on the [001] basal plane from Lum et al. (2016) after Deer et al. (1966). ....................................... 74!Figure 2: Emerald mines and notable geologic features in the Eastern Cordillera, Colombia ( modified from Banks et al. 2000). ................................................... 75!Figure 3: The study area delineated by data coverage within Selwyn Basin. ........... 76!Figure 4: Data coverage for stream sediment geochemistry. ..................................... 77!Figure 5: Major thrust zones of the Selwyn Basin (compiled from Héon [2003]). ... 78!Figure 6: Data coverage for Na INAA analyses of stream sediment geochemistry. . 79!Figure 7: Anomalous sodium values in stream sediment within black shale lithologies.. ............................................................................................................................. 80!Figure 8: Potassium in stream sediment within anomalous sodium areas in black shale. ............................................................................................................................. 81!Figure 9: The “Beus” equation Na3/(Li*K*Mo) applied to sodium anomalies in black shale (Beus 1979). ............................................................................................... 82!Figure 10: Beryllium concentration in stream sediment within sodium anomalies in black shale. .......................................................................................................... 83!Figure 11: Chromium and vanadium in stream sediment within sodium anomalies in black shale. .......................................................................................................... 84!Figure 12: Be and Cr+V are multiplied to illustrate unusual drainages that are likely enriched in all of these elements. ........................................................................ 85!Figure 13: LREE values are plotted with sodium anomalies in black shale. High and low extremes are coloured such that interpretations of leaching and enrichment may be possible. .................................................................................................. 86!Figure 15: Summary of traverses and geologic features in the Mountain River Beryl region. .................................................................................................................. 87 Figure 14: The Rusty Shale Formation of the Little Dal Group is exposed just South of the Keele River. .............................................................................................. 88!Figure 16: Several prospective areas are outlined based on the previous figures. .... 89! ix Figure 17: Geology of the Lened occurrence (modified after Adie & Allen 1960, Wise 1973, Gordey 1992). ............................................................................................ 90!Figure 18: Black siliceous mudstone mineralogy and textures ................................. 91!Figure 19: (A) Emerald-bearing quartz veins cut a light grey skarn body (in box) high on Lened Ridge. .................................................................................................. 92!Figure 20: Skarn minerals and textures. .................................................................... 94!Figure 21: Details of emerald-bearing quartz veins from Lened. .............................. 95!Figure 22: Three pale bluish-green faceted emeralds from Lened. From left to right the cut gems weigh 0.14, 0.16, and 0.07 carats. .................................................. 96!Figure 23: Al versus the sum of other Y-site cations, in atoms per formula unit, for 88 Lened emerald compositions and 435 emerald compositions from the literature. ............................................................................................................................. 97!Figure 24: Mg + Mn + Fe vs. monovalent channel-site cations, in atoms per formula unit, for rim, intermediate, and core zones of Lened emeralds compared with V-emerald compositions from Eidsvoll, Norway (Loughrey et al. 2013), Dyakou, China (Huang et al. 2015), and Muzo, Colombia (Ottaway 1991). .................... 98!Figure 25: Triangular diagram of FeO-Cr2O3-V2O3 weight percentages from analyses of emerald in this study, and analyses from the literature (with all Fe as FeO). . 99!Figure 26: Al-Fe(tot)-Mg diagram (in molecular proportions) for tourmaline shows that Lened tourmaline is Mg-rich dravite and plots in fields characteristic of tourmaline from metapelites. ............................................................................. 100!Figure 27: Si-R2+ mica classification diagram in molecular proportions after Wiewióra & Weiss (1990). ................................................................................................ 101!Figure 28: 40Ar-39Ar incremental heating plateaus for Lened pluton and emerald veins. ........................................................................................................................... 102!Figure 29: Channel δDH2O versus calculated δ18OH2O (‰, V-SMOW) for emeralds from Lened and other granite-related and Canadian emerald localities. ........... 103  Figure 30: Calculated δ18OH2O for fluid in equilibrium with granite and veins. ...... 104!Figure 31: Boron isotopic composition of tourmaline from Lened, Tsa da Glisza (Galbraith et al. 2009) and a compilation of δ11B (‰) values for various lithologies (Jiang & Palmer 1998). ..................................................................................... 105  x  List of Abbreviations EPMA Electron Probe Microanalysis INAA Instrumental Neutron Activation Analysis IP Induced Polarization LA-ICP-MS Laser Ablation Inductively Coupled Plasma Mass Spectrometry LREE Light Rare Earth Element MRB Mountain River Beryl NTGS Northwest Territories Geological Survey NWT  Northwest Territories REE Rare Earth Element SD Standard Deviation SG Specific Gravity TdG Tsa da Glisza TSR Thermochemical Sulfate Reduction YGS Yukon Geological Survey YT Yukon Territories        xi Acknowledgements Many extraordinary people have helped me finish this thesis.  Two grants from the Northern Scientific Training Program made this work possible. Foremost I thank my supervisor, Dr. Lee Groat, who trusted in my ability and took me on as a student. Thank you for the unique opportunities and experiences during my time at UBC. Thank you to colleagues, mentors and friends Jan Cempírek, David Turner, Andrew Fagan, and Thomas Chudy for being generous with your time and advice. Everyone in the Mineralogical Research Group has contributed to this thesis along the way: Mackenzie Parker, Jordan Roberts, Emily Scribner, Jim Evans, and Dana Caudle. I would especially thank Philippe Belley for the many conversations we have had while driving to gem locales.  I am grateful to Daniel de Narváez who provided incredible support during a trip to Colombia that fueled a permanent interest in Colombian emerald. Thank you to Dr. Daniel Kontak, for the enthusiasm and help with the Lened project. Thank you to Tavis for your friendship and for enduring one of my fieldwork-on-the-cheap™ programs; indeed, a significant contribution of this work is the finding that two highly motivated men in a loaded packraft can paddle just slightly faster than a grizzly bear can swim.  I am eternally grateful for the incredible support of my grandfather and parents. Lindsay, your love and support helped me each day and I promise I will learn to have fun again if they let me graduate.     xii Dedication    for Papa and Elaine 1 1!  Introduction High quality gem emerald of the genetic type found in Colombia is only known to occur in a handful of locations within black shale of Colombia’s Eastern Cordillera. Similar black shales are common all over the world and are usually associated with global ocean anoxic events that form black shales at continental margins, rifts, and isolated basins. It may be reasonably expected that Colombian-type beryl could form in such widespread and geologically similar environments outside of Colombia. Black shale of Canada’s Yukon and Northwest Territories may be a particularly likely candidate for Colombian-type emerald mineralization that is underexplored with respect to emerald. Clues from several known beryl occurrences in this region point to the potential for Colombian-type emerald and the area therefore merits specific consideration. To take the first step in systematic Colombian-type emerald exploration within Canada’s Selwyn Basin, I review emerald exploration methods used in Colombia and apply several of these techniques to regional silt geochemistry data encompassing black shales of the Selwyn Basin. The second part of this thesis addresses important unconstrained details of emerald formation at the Lened emerald occurrence in the Northwest Territories (e.g. the role of local black shale, and timing of mineralization). We have contributed significantly to the understanding of Lened, and integrated these results into recommendations for future regional emerald exploration in light of findings from my analysis of silt geochemical data.  Colombia stands supreme in respect to emerald, for nowhere else are they found in such consistently high quality and quantity. - Sinkankas (1981)  2 1.1! EMERALD Emerald is the deep luminous green gem variety of the mineral beryl and is prized as a precious gemstone. Beryl is considered a ring silicate, but is more properly a tectosilicate (Deer et al. 1966) with the structural formula Be3Al2(SiO2)3. Chromium and vanadium are the dominant chromophore elements in emerald; they substitute for aluminum in the octahedral site (Fig. 1).  Emerald is particularly scarce on Earth because evolved felsic environments that concentrate beryllium (a highly incompatible element) are virtually devoid of the crucial emerald chromophores chromium and vanadium. Mafic rocks or metalliferous black shales are often rich in transition metal chromophore elements (including Cr, and V). As such, emerald mineralization requires geochemical contamination between diverse rock types and this is achieved in several known settings as defined broadly by Schwarz & Giuliani (2001):  •! Type I: Be-bearing granitic pegmatites intrude ultramafic rocks •! Type II: schist-hosted metamorphic emeralds, and  •! Type IIb: sedimentary-hydrothermal “Colombian-type” emeralds.  In Northwest Canada, only two emerald occurrences are known to have yielded faceted gems: Tsa da Glisza (TdG, formerly Regal Ridge), and Lened. Mountain River Beryl (MRB) is a third important occurrence in the Mackenzie Mountains, NWT which has only produced milky green beryl to date, but represents a modified Type-IIb “Colombian-type” emerald occurrence and is therefore of significant interest academically and for future testing of amagmatic emerald exploration models. Colombian emerald deposits occur in radically different geologic environments than the relatively common granite-related emerald occurrences, therefore if any Colombian-type emerald occurrences are exposed in northern Canada, they are likely to have been overlooked.  Very little systematic emerald exploration has been undertaken in Canada’s northern Cordillera. A small exploration effort was briefly sparked by interest in the TdG deposit ca. 2003 for granite-related Type-I emerald.   3 1.2! COLOMBIAN EMERALD Colombian emerald deposits in the Boyacá region of Colombia have been mined for over 500 years, producing some of the world’s most spectacular and valuable emerald specimens and cut gemstones (Groat et al., 2014 and references therein). The prolific mines were worked first by Muzo indigenous people who are thought to have settled the area around 1000 AD and later, Spanish conquistadors took over emerald mining as early as 1566, creating a world trade in Colombian emerald (Lane, 2010). Subsequently, many of these workings were slowly abandoned over the following two centuries until private (mostly French) and later government interests picked up mining and exploration in the early 19th century that has been more or less consistent to the present day (Journal of the Society of Arts 1872, Oppenheim 1948, Groat et al. 2008).  Scientific understanding of the emerald deposits is surprisingly limited, given the historic, economic and mineralogical importance of emerald mining in Colombia. The most comprehensive academic studies to date were largely completed in the 1990s and comprise the works of Banks, Branquet, Cheilletz, Giuliani, Laumonier, and Ottoway who were given the rare opportunity of field access to study the emerald deposits (e.g. Ottaway 1991). Recent work includes a review by Pignatelli et al. (2015) including an investigation into formation of trapiche emeralds as well as euclase from both East and West emerald belts (Pignatelli et al. 2017). The early publications demonstrated the unique hydrothermal character of Colombia’s emerald deposits (to be discussed), but also generated a number of new lines of inquiry that have yet to be resolved (e.g. satisfactory geochronology of emerald mineralization, and the presence of exotic rare earth minerals).  Regional Geology  Emerald deposits in Colombia form two northeast trending zones on the east and west flanks of the Eastern Cordillera. The Eastern Cordillera is a fold-thrust mountain belt overthrusted upon the flat-lying Llanos Foreland Basin to the East. Rocks of the Eastern Cordillera are composed of a marine sedimentary sequences including black shales, silt/mudstones, limestones/dolostones, evaporite horizons (including salt  4 diapirs) and significant economic hydrocarbon content. The sequences have not undergone significant metamorphism but the region is highly deformed as a result of accretion of the Nazca Plate and South American continent (Branquet et al. 2002). Igneous rocks are uncommon in this region and Vásquez et al. (2010) report rare volumetrically insignificant Cretaceous to Tertiary mafic dikes and sills consistent with a rift setting.  Deposition of the sedimentary sequences occurred in a rift province during the Jurassic to Paleogene, attaining a maximum depth of 4-6 km (vitrinite reflectance data, Sánchez et al. 2012). Compressional tectonics, basin inversion and exhumation began in the Eocene (~49 Ma) and continued through the early Pliocene (~5 Ma) (Ramirez-Arias et al. 2012).  The age of emerald mineralization has been dated at ~31.5-38 Ma in the western zone at Muzo and Coscuez (Ar-Ar on green mica, Cheilletz et al. 1994) and ~65 Ma for the eastern zone at Chivor (same technique, Cheilletz et al. 1995). Other workers have since presented conflicting ages; Romero-Ordoñez (2000) reported a 67 Ma Rb-Sr (emerald) errorchron for Peñas Blancas in the western zone, and a 61 Ma Rb-Sr (emerald) errorchron for Chivor. Svadlenak (2014) reported two Ar-Ar ages of ~60-62 Ma on Tequendama mine vein selvage muscovite alteration.    Stratigraphy There is significant ambiguity in the literature as to the precise hosting stratigraphy of emerald occurrences when considering all Colombian deposits and the regional scale. The western deposits (e.g. Muzo, Coscuez, Cunas, La Pita, and more) are reported to be hosted in black shales with intercalated dolomite and limestone of the Rosablanca and Paja Formations of the Villeta Group where the main emerald horizon is within Hauterivian (~133-129 Ma) siliceous black shales and Barremian to Aptian (~129-113 Ma) mudstones of the Paja Formation (Ottaway 1991, Pignatelli et al. 2015).  The eastern zone emerald mines (e.g. Chivor, Gachalá, Buena Vista) occur within limestone-sandstone-black shale sequences of the Berriasian Guavio Formation (~135-130 Ma) and overlying Valanginian Macanal Formation (~130-122 Ma, Pignatelli et al. 2015).   5  Emerald Mineralization In both zones emerald is hosted in arrays of extensional quartz-carbonate-pyrite ± albite veins and stringers associated with stratiform breccia zones, albitites and carbonated host rocks resulting from sodic and carbonic metasomatism of black shale. Metasomatism within mineralized tectonic blocks of the Muzo area leached major elements (K, Si, and Al) and slight leaching of trace Be is reported (Beus 1979). An important limitation of the current literature is that discussion of the “West” belt is usually reduced to study of several large Muzo mines close to one another (e.g. Catedral, Tequendama, Puerto Arturo, etc.) and studies of the “East” belt are focused almost exclusively on Chivor. As can be appreciated from Figure 2 there are numerous smaller emerald occurrences (and yet more that are not resolved on this regional map), some of which have not been studied in detail. Importantly, Banks et al. (2000) provides selected mineral chemistry for a number of the smaller mines.   Western Zone Mineralogy The mineralogy of western belt emerald deposits varies from mine to mine. The following major gangue minerals are associated with emerald-bearing vein stockworks: quartz, carbonates (calcite, dolomite, ankerite), albite, and pyrite. Other associated minerals include muscovite (locally green) and several clay minerals, fluorapatite, gypsum, hydrous iron oxide minerals, fluorite, copper sulfide minerals (Ottoway 1991, Beus 1979, Pignatelli et al. 2015). Parisite-(Ce) (CaCe2[CO3]3F2) is known to occur in emerald veins of the Muzo camp only. Recently euclase (BeAlSiO4[OH])–assumed only to occur in the eastern zone (e.g. Chivor)–has been extracted from La Marina mine in the western zone (Pignatelli et al. 2017).   Eastern Zone Mineralogy & Occurrence The vein mineralogy at Chivor is broadly similar to Muzo though simpler, and characterized by emerald, albite, pyrite, calcite, quartz, clay minerals, muscovite (locally green) (Ottoway 1991), and apatite (Klein 1941). Extensive weathering of massive stratiform pyrite forms three distinctive quartz and “limonite” iron oxidation  6 bands 50 m apart that are reported to be an important structural control on emerald mineralization (Ottoway 1991). 1.3! GENETIC MODEL The Colombian emerald mineralization model is unique among gem beryl deposits in that the evidence strongly suggests a completely amagmatic, basinal evaporitic fluid source for emerald mineralizing fluids (Ottaway 1991, Giuliani et al. 1995, Cheilletz & Giuliani 1996, Banks et al. 2000, Pignatelli et al. 2015).    Source of Emerald-Forming Elements (Be, Cr, V) Local black shales are the likely source of Be, Cr, and V in Colombian emerald. Beryllium leaching occurs within mineralized black shale zones which strongly suggests that Be is sourced from black shale (Beus 1979, Kozlowski et al. 1988, Ottaway 1991, Cheilletz et al. 1994, and Giuliani et al. 1999). Ottoway et al. (1994) suggests organic matter within the black shale is the host of Be and Cr/V. Beryllium is often organically bound in Be-enriched coal deposits, however typical coal and coaly shales have a lower Be deportment of ~1-5 ppm that can be hosted both inorganically (e.g. adsorption to clays) and in organic compounds (e.g. Eskenazy & Valceva 2003, Eskenazy 2006, Jianye 2007). Beryllium is not particularly enriched in Colombian black shales (1-4 ppm, Ottoway 1991) and therefore without further analysis it is difficult to assess whether Be is bound to organic matter or adsorbed to clay associated with organic matter. Giuliani et al. (1999) inferred that Be-mobility is dominantly associated with the breakdown of Fe-Mn oxyhydroxide phases (based on a hydroxylamine hydrochloride in acetic acid extraction procedure). The study represents the first attempt to isolate a Be source phase in shale, however the sample size is small (n=12, 1 g samples) and the fact that residual silicates contain ~2 orders of magnitude more Be than the Fe-Mn oxyhydroxides is not elaborated on. More recently, Banks et al. (2000) suggested that metasomatism of black shale released Be, but these authors did not specify a hosting phase. In conclusion, beryllium is likely hosted by one or more of several likely phases within the black shales and regardless  7 of the exact host-phase(s), the Be-leached alteration halo observed in several studies is strong evidence that local black shales are the source of Be in emerald.  Chromium (280 ppm) and vanadium (100 ppm) are enriched in the black shales associated with emerald formation in Colombia and are the only reasonable local source of the chromophores (Beus 1979). Transition metals, including V and Cr are commonly enriched in extremely reducing sedimentary environments. Sediments and organic matter deposited in anoxic environments (caused by numerous factors, such as high rates of burial) eventually become metalliferous carbonaceous marine shales through diagenesis (Premović et al. 1986, Vine & Tourtelot 1980, Francois 1988). Emerald is locally abundant and striking in appearance where it occurs, however it is only a minor phase and Be is only present on the order of parts per million in the vein system in contrast to the balance of elements that make up the major vein forming minerals (i.e. Si, Al, Ca, Na Fe, S, and C) (Giuliani et al. 1999, Ottoway 1991). In summary, the local shales supplied the required Be, Cr, and V for emerald mineralization (e.g. Giuliani et al. 1999).  Transport  Vein mineral fluid inclusions, isotopic studies, and vein mineral chemistry provide insight into the mechanism of liberation and transport of beryl-forming elements. The emerald veins of Colombia are sedimentary-hydrothermal in origin and fluid compositions of the parental vein fluid have been reconstructed most thoroughly in Banks et al. (2000).  There are no drastic differences in deposit mineralogy or inferred vein fluid chemistry between East and West emerald deposits which suggests the disparate deposits were formed by the same mechanism (Banks et al. 2000). Vein forming fluids are characterized by extremely high salinity on the order of 30-40 equivalent wt. % NaCl; the dominant cations are Na, Ca, Fe, K, and Cl is the dominant anion (Ottoway 1991, Giuliani et al. 1995, Banks et al. 2000). Cl:Br ratios of fluid inclusions suggest that the fluids are not simple formation brines; rather halite and evaporite strata were dissolved at various stages in the mineralizing fluids (Banks et al. 2000). Indeed, evaporite horizons are interbedded in black shale of the eastern deposits, and vein  8 formation has been linked to brine ascent along thrusts and intense fracture zones in the western emerald zone. The model of Ottaway (1991, 1994) proposes that Be was liberated from wall-rock shale during tectonism by OH-. Banks et al. (2000) proposes that fluoride-carbonate complexes are far more efficient for Be transport (in the range of several hundred ppm versus ~1 ppm for OH- complexes). The strongest support for the F-CO3 complexing hypothesis is the common association of fluorite (CaF2), carbonates, and fluoro-carbonate (i.e. parisite) with the emerald mineralization stage.  Pressure at the time of emerald formation has been constrained by Cheilletz et al. (1994) and Kozlowski et al. (1988) to approximately 1 kbar based largely on fluid inclusion decrepitation temperatures. Cheilletz et al. (1994) estimates the formation temperature as 290-360 °C based on fluid inclusion microthermometry.   Trap  The vast majority of emerald mineralization in Colombia occurs in structurally controlled vein systems; thrusts, tears, fold hinges, and stratiform breccia structures (at Chivor), and rarely emerald occurs in porous altered wall-rock (e.g. trapiche emerald, Pignatelli et al. 2015). Therefore, emerald is always associated with permeability and structural traps in the hosting formations. There is little consensus in the literature regarding the exact mechanism causing emerald precipitation at these locations however the likely scenarios will be discussed.   It is generally agreed upon in the literature that two stages of mineralization occurred in the Muzo area (Eastern belt paragenesis has not been described in as much detail). An initial barren stage of mineralization consists of fibrous calcite, pyrite, albite, quartz and green micas followed by a second stage of emerald mineralization consisting of rhombohedral calcite, dolomite, albite, pyrite, kerogens, and finally emeralds, REE-rich dolomite, parisite-(Ce), fluorite and lastly quartz (Giuliani et al. 1995, Banks et al. 2000).  Several authors propose fluid mixing of meteoric and formation waters (variously influenced by dissolution of local evaporites) in emerald vein formation as (1) the crucial mechanism causing emerald precipitation (Banks et al. 2000) and (2) as a means  9 of describing various observed O and H isotopic measurements in vein minerals (Giuliani et al. 2000). Thermochemical sulfate reduction (TSR) of sulfate-rich brines has been invoked often to explain important observed features of Colombia’s emerald deposits. Cheilletz & Giuliani (1996) propose Reaction 1:     Ra(CH2O)2 + SO42- = Rb + 2HCO3- + H2S (1) in which sulfate is evaporitic, CH2O is a carbohydrate and Ra/Rb are large organic molecules. HCO3- and H2S produced by the reaction above are thought to react with Ca and Fe present in hydrothermal fluids to precipitate pyrite (FeS2) and calcite (CaCO3) (Giuliani et al. 2000). Carbonation associated with TSR may have played a role in scavenging or releasing Be (complexing?) and Cr/V (overpressuring furthering permeability?), though it is unclear if TSR contributed at all to destabilizing Be complexes to form emerald (Ottoway 1991, Cheilletz & Giuliani 1996, Banks et al. 2000, Giuliani et al. 2000). TSR is thought to be indirectly responsible for the low iron content and therefore excellent colour of Colombian emerald– intense Fe scavenging by H2S would lead to the abundant pyrite mineralization which likely limited Fe from contaminating the available chromophores during beryl formation (Groat et al. 2014).  TSR of sulfate-rich evaporitic fluids is used by the above authors to explain extensive oxidation of organic matter in black shales, albitization, and brecciation from CO2 overpressuring.  Isotopic evidence (Giuliani et al. 2000) supports sulfate reduction through oxidation of organic matter and TSR accounts for important field observations that are otherwise difficult to reconcile such as (1) observed hydrothermal anthracite interpreted as coeval with emerald mineralization, (2) occurrence of the two most abundant vein minerals calcite and pyrite, (3) oxidation zones (“cenicero”) of organic matter in mineralized black shales, (4) albitization, and (5) brecciation inferred to result from CO2 overpressuring and subsequent collapse.  Synthesis of the Colombian Emerald Genetic Model To date, consensus on all important details of the Colombian emerald genetic model has remained elusive, however many important constraints have been resolved:  10 1.! The sedimentary-hydrothermal (amagmatic) nature of the mineralizing brines is clear and the widespread emerald occurrences in the eastern and western zones are of the same genetic type. Parental brines of ~30-40 equivalent wt. % NaCl and of similar chemistry are implicated in mineralization that is controlled largely by tectonic permeability, the presence of evaporites, and metalliferous organic-rich black shales.  2.! The parental brines were present at a regional scale and were influenced to some extent by evaporite dissolution in every case studied (though precise sources of evaporite vary between deposits). 3.! Thermal sulfate reduction (TSR) by organic matter during metasomatism of Be-Cr-V-bearing black shales seems to adequately explain most observed phenomena, including vein mineralogy. 4.! Some unresolved details of the current model include the exact mechanism of beryl saturation in fluid, original host-phase of REEs, compilation of deposit characteristics for all mines, and definitive geochronology.  1.4! WHY EXPLORE FOR COLOMBIAN-TYPE EMERALD IN CANADA? The conditions leading to gemstone deposits are usually rare but seldom unique. It is possible that Colombian-type gem emeralds are unique to Colombia, but it would seem unlikely given the common nature of the basic constituents of this deposit type: black shale, compressive tectonics and basinal brines. In the Selwyn Basin geological province of Canada’s Yukon and Northwest Territories, vast expanses of Ordovician-Missippian black shale of the Earn and Road River Groups are exposed (Fig. 3). These shales bear some important similarities to the emerald-bearing units in Colombia, and the region has never been systematically explored for Colombian-type emerald. Additionally, two unusual beryl occurrences in this region give cause for further investigation of surrounding black shales as a potential target for emerald exploration.    11 1.5! KNOWN EMERALD DEPOSITS OF CANADA’S NORTHERN CORDILLERA 1.5.1!Tsa Da Glisza  Tsa da Glisza is a Type I (igneous) emerald deposit that was discovered in 1998 by Bill Wengzynowski while prospecting for Cu and Zn (Groat et al. 2002). The deposit is located in the Finlayson Lake district of southeastern Yukon (Fig. 3) where pegmatites, aplites, and quartz-tourmaline veins associated with a proximal two-mica pluton of the Anvil suite (112-100 Ma) intrude mafic metavolcanic schist of the Upper Devonian Fire Lake Formation (Neufeld 2004). Emerald occurs within quartz-tourmaline veins, linear zones of altered schist, and in aplites (Groat et al. 2002, Neufeld 2004, Galbraith et al. 2009). Tsa da Glisza is the most prolific emerald occurrence yet discovered in Canada’s North. Fine gem quality emerald has been produced at this locality, and significant attempts at development have been made, however the deposit has not proven economic to date.  1.5.2!Mountain River Beryl In 2007, the Mountain River green beryl occurrence was discovered in the north-central Mackenzie Mountains of the Northwest Territories, south of the Mountain River in the vicinity of Shale (Palmer) Lake (Fig. 3). Edith Martel of the NTGS discovered the showing during regional mapping (pers. commun., Hendrik Falck). The beryl is hosted by extensional quartz–carbonate veins cutting Neoproterozoic sandstone and siltstone of the Twitya Formation within the hanging wall of a thrust fault that emplaced these strata above Paleozoic rocks (Hewton et al. 2013). δ18OH2O values of 15.9-17.2‰ were calculated for the vein fluid using the oxygen isotopic compositions of beryl (structural O, not channel H2O) and a fractionation factor for the beryl-water system at the estimated beryl formation temperature; these values are typical of evolved sedimentary sulfate brines (~16-17‰, Hewton et al. 2013). The beryl mineralization was proposed by Hewton et al. (2013) to have resulted from inorganic thermochemical sulfate reduction via the circulation of warm basinal brines through siliciclastic, carbonate, and evaporitic rocks. These brines were driven along deep basement structures and reactivated normal faults and divalent iron in local  12 sandstone is proposed as the sulfate reductant (Hewton et al. 2013). The Mountain River occurrence thus represents a variant of the Colombian-type emerald deposit model, the only known occurrence of similar type outside of the Muzo area and Chivor deposits in Colombia (Pignatelli et al. 2015, Cheilletz & Giuliani 1996).  1.5.3!Lened The origin of emerald at Lened (Fig. 3) has been considered igneous (Marshall et al. 2004). Emerald occurs in quartz veins in association with a skarn body, two-mica granite pluton, and abundant metalliferous black mudstone. Given the complex local geology, and presence of abundant black mudstone, the origin and timing of emerald mineralization at Lened is the subject of chapter three.    13   2!  Exploring for Colombian-type Emerald 2.1! TECHNIQUES USED IN COLOMBIA Emerald exploration in Colombia exploits several important mineralogical, geochemical, and structural characteristics of the deposit model. The single most important exploration indicator is reported to be elevated Na in stream sediment or soil (Beus 1979). Sodium levels in sediment are a proxy for the abundant albite (sodic alteration) that is directly associated with emerald mineralization. The ratio Na/K provides further discriminatory power and Beus (1979) recommends searching for a ratio of Na/K > 1. Mineralized tectonic zones are usually strongly depleted in Li, Mo, Ba, Zn, V, and Cr compared to background unaltered shale. A second geochemical formula that exploits the above observations to predict emerald mineralization is Na3/(K*Li*Mo) and is reported to have the highest predictive ability in Colombia (Beus, 1979). The Colombian deposits are structurally controlled by thrust faults and interconnecting transcurrent faults which act as conduits and traps for emerald-mineralizing fluids. As such, it is important to target an area for exploration that has been made adequately permeable through tectonic processes that it could plausibly have received hydrothermal alteration. Several structural indicators have been noted by Cheilletz (1996) as important indicators for emerald mineralization and these include:  14 1.! Intense fracturing and brecciation 2.! Intersection of fault systems or interstices between parallel faults 3.! Preference for veins crossing foliation of black shale 4.! Extensional environments (fold hinges and larger scale brecciation).   Unique mineralogy is also a benefit to emerald exploration efforts in Colombia. The type locality for the rare earth mineral parisite-(Ce) (CaCe2(CO3)3F2) is the Muzo emerald mine where it is cogenetic with emerald (Ottoway 1991). This is peculiar to the Muzo area, but very useful because parisite has a specific gravity (SG) of ~4.3 and is recovered in mineralized drainages by heavy mineral concentrate (HMC) sampling (pers. commun., William Rohtert). Other minerals that may be recovered in HMC sampling include fluorapatite (SG ~3.2), and fluorite (SG ~3.1) which can be analyzed for sedimentary hydrothermal provenance (see Makin et al. 2014). It is not effective to directly recover beryl by density separation because it has a specific gravity of ~2.7 which is very similar to most rock-forming minerals. Nonetheless, the green of emerald contrasts starkly with black shale sediment, and repeated washing of sediments is an effective and ubiquitous technique employed by local emerald-seeking “guaqueros” to reveal emerald in mineralized Colombian drainages.  In a preliminary unpublished study, I used electron probe microanalysis (EPMA) to identify 20-30 µ hexagonal florencite-(Ce) crystals intergrown with framboidal pyrite in slightly altered black shale of the Catedral mine, Muzo. I cautiously suggest (subject to further work and careful validation of this hypothesis) that detrital florencite-(Ce) (SG ~3.6) recovered by HMC sampling may be a proxy indicator of black shales formed in a similar environment to the emerald fertile lithology of Colombia. Reference to florencite in this work is based on this speculative hypothesis.  For several of the modern mining operations at Muzo and Chivor, geophysical techniques such as induced polarization (IP) and magnetic surveys have been used to delineate pyrite mineralization that is abundant and often associated with emerald-bearing veins (pers. commun., William Rohtert). Gutiérrez (2003) tested several radiometric and magnetometric techniques on Chivor district deposits with some success.   15  2.2! APPLICATION OF TECHNIQUES TO NORTHERN CANADA  Several techniques described above can be applied directly to the black shale-endowed Selwyn Basin in Canada’s Yukon and Northwest Territories. Unlike the Eastern Cordillera of Colombia where there are no significant occurrences of igneous rocks exposed, Ordovician-Mississippian black shales/mudstones of the Selwyn basin are commonly intruded by Cretaceous felsic stocks of the Selwyn and Tombstone Plutonic Suites. This means that there is abundant plutonic alkali feldspar weathering into black shale drainages which complicates the use of Na/K in regional stream sediment geochemical data for discovering albite-alteration related to emerald. Nonetheless, this technique is worth further discussion due to its ease and cost effectiveness in reducing a large prospective area.  Several relevant publicly available geochemical datasets are useful for this study and their coverage and sample density are shown in Figure 4.  Reanalysis of stream sediments across most of the Selwyn Basin was undertaken between 2011-2016 by the Yukon Geological Survey (Jackaman 2010, 2011a, 2011b, 2011c, 2012a, 2012b, 2012c, 2012d, 2012e, 2015a, 2015b, 2015c, 2015d, 2015e, 2015f, 2015g, 2015h, 2015i, 2016a, 2016b, 2016c, 2016d), improving the quality and number of elements assayed from archived samples (e.g. measurements of Be, K, and Li were added). The Mackenzie Mountains silt geochemistry has been regionally sampled by the Northwest Territories Geological Survey (Gordey et al. 2012, Falck et al. 2015) and the data is publicly available. Unfortunately, there is no analysis of Be in either study (though Li is available in Falck et al. 2015).  As mentioned above, preliminary analysis of Muzo black shales has indicated the presence of florencite-(Ce) (our unpublished data), suggesting a potentially authigenic source of light rare earth elements (LREE) that may have been remobilized to form parisite in hydrothermal veins at Muzo. Florencite-(Ce) is noted to occur in the Rusty Shale Formation in the Mackenzie Mountains (Pouliot & Hofmann 1981). It has also been recovered during HMC sampling west of Lened in the Selwyn Range (Falck et al. 2015). The presence of the authigenic LREE mineral florencite in the Selwyn  16 Basin might indicate some sedimentary facies formed under similar conditions as emerald-fertile Colombian black shale. If Colombian-type deposits exist in the northern Cordillera, HMC sampling could further yield parisite as a proxy for emerald mineralization or florencite-(Ce) as a plausible indicator of appropriate host rock. A third strategy for Colombian-type emerald exploration in northern Canada is to evaluate major thrust zones (Fig. 5) within Cr/V-bearing black shales, especially in proximity to evaporite units. The only significant evaporite unit in the region is the Gypsum Formation of the Little Dal Group which is sporadically exposed along the margin typically East of the Plateau Thrust (discussed later) and notably in the vicinity of Mountain River Beryl (Turner et al. 2011). Further consideration of this vicinity is merited because of the proximity of the Shale Lake Fault, the Plateau Thrust, and Gypsum Formation which have been implicated in the MRB occurrence.  2.3! METHODS Bedrock geological data was compiled for the study area in QGIS software, using stream sediment geochemistry datasets, fault, and geographic information (i.e. roads and provincial boundaries). Geochemical data points outside of black shale-bearing lithologies were removed to avoid confounding the dataset with “igneous-influenced” values as described above. Elemental values of interest (i.e. Na, K, REE etc.) were interpolated as a raster using inverse distance weighting. To identify geochemical anomalies quantitatively, a standard threshold of two standard deviations from the mean was used (Carranza 2009). For this dataset, Mean+2SDof Na/K is ~0.3 though K data coverage is limited to the 2016 reanalysis. This is far lower than Beus' recommended “Na/ K>1” criterion, but is used on the basis of statistical significance within the dataset rather than a direct comparison to Colombia. Any regionally spaced samples that drain Colombian-type emerald mineralization would have significant dilution of the Na signal compared to presumably much more localized surveys in known mineralized regions of Colombia, and this may explain the lower values (or there is no similar mineralization).   17 Contour polygons were drawn over the raster to delineate anomalous Na values herein defined as being greater than two standard deviations from the mean. To explore the relationship of anomalous Na with other geochemical indicators, rasters were interpolated for Cr+V, La+Ce, and Be, within the Na anomaly contours. Colour gradients inside the contour area represent the range between mean values (white/transparent) and anomalies of two standard deviations from the mean and greater (saturated colour).  Field checks have not been carried out in prospective areas identified by methods above, however some fieldwork complementary to this work consisted of searching for albite alteration, brecciation, or veining, and vetting mapped lithologies in the vicinity of the Mountain River Beryl site west of the Plateau Thrust (2014). Two extensive traverses were made in the Sayunei Range in 2014, including a brief visit to MRB. A trip was made to the South-Central Mackenzie Mountains in 2016 to prospect for emerald around the South Plateau Thrust in the vicinity of gypsum occurrences, black shale, and a nearby florencite occurrence. This additional work is outside the scope of searching for purely “Colombian-type emerald” in the sense that MRB represents a significant variation of the Colombian emerald deposit model (e.g. it is not hosted by black shale) and results of this work are briefly presented in the interest of future emerald prospectors. See Appendix A for a summary of fieldwork in Utah investigating another reported Colombian-type emerald occurrence that is not otherwise discussed herein. Yukon stream sediment survey samples were recently reanalyzed for YGS by Acme Labs of Vancouver using aqua regia digestion (Fig. 4, Jackaman 2010, 2011a, 2011b, 2011c, 2012a, 2012b, 2012c, 2012d, 2012e, 2015a, 2015b, 2015c, 2015d, 2015e, 2015f, 2015g, 2015h, 2015i, 2016a, 2016b, 2016c, 2016d) and inductively coupled plasma mass spectrometry (ICP-MS). Original YGS geochemical analyses of Na (re-released in a 2003 YGS compilation; Héon 2003) were performed by instrumental neutron activation analysis (INAA, see Fig. 6 for coverage).  Silt geochemistry coverage of Selwyn Basin is reasonably complete at a regional scale except for two missing NTS 250k sheets covering the central portion of the  18 Dawson, Tombstone, and Robert Service thrusts (NTS 106D, NTS 106A; see Figure 4).  Colombian-type emerald deposits have relatively small footprints, and regional scale geochemical analyses with data points 5-10 km apart may not be sufficient to identify an emerald occurrence. For example, the only known modified Colombian-type deposit (MRB) is not predicted by this work. Therefore, there is large uncertainty in the usefulness of this technique with the existing data density, however it is the logical first attempt at prospective area reduction given the success of the technique in Colombia (Beus 1979).  2.4! RESULTS Figure 7 presents the difference and overlap of Na anomaly contours within black shale lithologies as measured by either INAA (blue) or ICP-MS (red). The areas inside the contours represent > 2 SD Na anomalies. Grey areas represent black shale. There is significant disagreement between the results for each technique, though a smaller proportion of the anomalies overlap (purple areas) as should be expected (given the analyses are on splits of the same sample). Undifferentiated plutonic and volcanic rocks are also shown in Figure 7 showing the wide distribution of igneous rocks in association with the shales. For example, some anomalies clearly border round stocks that are Cretaceous felsic intrusions. The second criterium of Beus (1979) is high Na coupled with low K and to this end, values of K from nil to anomalous high are presented (Fig. 8).  The Beus (1979) discriminant equation: Na3/(K*Li*Mo) is applied in Figure 9 within Na anomalies in black shale. Note that Li data is only available in the Yukon RGS 2016 reanalysis area (Fig. 4), therefore the Beus equation is only applied to this area. High and anomalous Be values are shown within shale Na anomalies in Figure 10 and Cr + V anomalies are shown similarly in Figure 11. Individually Be, and Cr + V are useful but potentially even more predictive is the comparison of Be and Cr + V (Fig. 12) within the Na anomalies. Be usually has an inverse relationship with Cr + V because these elements are enriched in rock types that are typically not found together.  19 This relationship is shown to largely hold true in Figs. 10 and 11. In unusual geological circumstances (that might produce emerald) anomalous amounts of Be and Cr + V might be found together. Figure 12 shows the results of multiplying interpolated values of Be and Cr+V such that areas where both are enriched are exaggerated and more easily recognized.  LREEs (here defined as the sum of La and Ce in ppm) are enriched in a number of black shale drainages (Fig. 13) that are also associated with Be, and Cr + V highs (compare Figs. 12 and 13). Both negative and positive LREE anomalies are highlighted within Na-anomalous black shale because it is uncertain whether leaching or enrichment is likely at the scale of sampling. 2.4.1!Field Assessments Several trips were made to the MRB region. Two extensive traverses were made in the Sayunei range, including a brief visit to MRB (Fig. 14; traverses 2014a and 2014b). No new beryl occurrences were discovered. Several scattered showings of smithsonite and copper sulfides were encountered, but there was little evidence of further mineralization of the MRB type. A single traverse is emphatically not sufficient to make conclusions on the beryl potential of the area. Barren coarse fibrous quartz-siderite/ankerite veins are common throughout the range and are likely syn-orogenic.  Another trip was made in 2016 (Fig. 14; 2016) to prospect the South Plateau Thrust in the vicinity of reported black shale, gypsum, and florencite occurrences (Fig. 15). No new beryl occurrences were discovered. The Rusty Shale Formation of the Little Dal Group is known to host florencite-(Ce) in shale described as “black” by Pouliot et al. (1981). As expected, recessive gypsum/anhydrite units and the trace of the Plateau Thrust are rarely exposed, making prospecting challenging. The Rusty Shale Member is prominently exposed in the mountains West of the Keele River and the Plateau Thrust (Fig. 15). The rusty shale encountered during the traverse (Fig. 14; 2016) would not rightly be considered black shale and clastic sedimentary rocks were largely grey-beige with little apparent organic matter. Minor amounts of rusty-weathering pyrite in the shale leads to the formation’s striking rusty appearance when seen from a distance. The unit is likely variable laterally and may be true black shale  20 elsewhere. Florencite was sought but not found within rusty shale strata below cliff-forming stromatolitic dolostones (63° 52' 3.62" N, -127° 48' 30.36" W) assumed to be on strike with the known florencite occurrence of Pouliot (1981, 63°50’20” N, 127°33’55" W). 2.5! DISCUSSION Several regions of interest are identified from the results of silt geochemistry analysis. Green circles in Figure 16 show areas where an Na anomaly coincides with high Be, high Cr+V, and low K. These areas were assessed and drawn qualitatively on a binary “high or low?” basis for clarity and only the Na anomalies within these areas are suggested as prospective. Quantitative cutoff values for prospect determination were avoided (other than anomaly identification); there is insufficient Colombian data in the literature to inform a quantitative model excepting Beus’ (1979) rule of “Na/K > 1” which has been discussed. All anomalous areas within black shale units (Fig. 16) are also in the vicinity of important thrust zones; specifically, the Dawson, Tombstone and Robert Service Thrusts north of Dawson City and the Mackenzie fold and thrust belt in which Macmillan Pass is located (Fig. 4). Future Colombian-type emerald explorers would be advised to list the most prospective areas identified here and field check as many of these sites as possible. Systematic gemstone exploration in Canada is rarely funded, therefore companies already engaged in mineral exploration in these areas may profit from paying attention for signs of Colombian-type emerald during the course of exploration for other resources.  2.5.1!Limitations It is important to recognize that the only known modified Colombian-type beryl occurrence (MRB) was not predicted by this analysis. This may be due to the small size of the occurrence and the regional scale of stream sediment sampling. Clearly, the present analysis of publicly-available data cannot be expected to identify all occurrences though it is a logical (and economical) first step.   21 The 2016 YGS silt geochemistry samples were analysed by ICP-MS. Digestion of the sample pulps was by aqua regia, which Acme describes as only a “partial” digestion and “mineral species dependent” (Bureau Veritas Minerals 2015). It is unknown to what extent aqua regia might digest resistant albite in stream sediment samples and this is an important limitation of this dataset. The 2016 reanalysis provides analyses for more elements that are useful in this study (e.g. Be, K, and Li) that are not present in data from the Mackenzie Mountains and north of the reanalysis area (Figs. 4 and 6). Original YGS geochemical analyses of Na (e.g. re-released in the 2003 YGS compilation of Héon) were performed by instrumental neutron activation analysis (INAA, see Fig. 6 for coverage). In INAA a neutron flux is applied to the sample to produce radioactive nuclides, and the characteristic gamma ray emissions from these nuclides are measured (Alfassi 2007). INAA does not require sample dissolution (the newer ICP-MS analyses do), and thereby avoids the problem of aqua regia dissolution inherent to the 2016 YGS reanalysis dataset. Therefore, the INAA Na anomalies may be more likely to measure Na from albite, if present. 2.5.2!Suggested emerald prospecting techniques If emerald occurs in any of the prospective areas identified above (Fig. 16), there are several techniques that may be employed to find it. These include locating signs of abundant hydrothermal pyrite, washing of sediment in prospective drainages to directly recover emerald, and HMC recovery of parisite, fluorite/fluorapatite, euclase, or florencite.  Searching for the Na signal of albite in soil and stream sediment has been shown in Colombia to be a powerful predictor of emerald mineralization. In Canada’s North, this is problematic at a regional scale due to contamination of abundant Na-rich felsic intrusions, and Na-rich dolostones. However, a technique such as Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN) might be applied to directly measure the presence of the mineral albite (and other indicator minerals?) rather than a more ambiguous Na geochemical signal that could also arise from sodium-rich carbonate rocks, for example. I would recommend reanalysis of  22 stream sediment samples using rapid automated quantitative mineralogical techniques that can directly identify albite alteration or even potentially beryl.    23 3!  Origin of Emerald at Lened, NWT 3.1! INTRODUCTION The Lened emerald occurrence is located north of the Yukon/Northwest Territories border in the Logan Mountains (62°22’ N, 128°38’ W; NTS 105/I7; Fig. 17). Access is most easily achieved by helicopter, though a bulldozer track once connected the site, via Flat Lakes, from the town of Tungsten 55 km to the southeast. The name “Lened” historically refers to a W-skarn occurrence 300 m southwest of the beryl veins and centred on the Cretaceous Lened granitic intrusion (Glover & Burson 1987).  At Lened, emerald-bearing quartz-carbonate veins cut a dominantly pyroxene-garnet skarn developed in a dolomitic limestone (Glover & Burson 1987). The veins are hosted by skarn, penetrating no further than 3 m into limestone to the south and pinching out before the mudstone unit to the north. Marshall et al. (2004) reported that the dominant chromophore in the Lened emerald is V, which almost certainly is associated with nearby sedimentary rock that averages 2000 ppm V. Marshall et al. (2004) suggested that heated fluids derived from the proximal Lened pluton traveled along a thrust fault to produce the observed skarns which host the emerald-bearing veins. The latter veins were suggested to have formed from the subsequent expulsion of fluids from the same but more chemically evolved (i.e., fractionated) granite. A series of sub-parallel fractures developed in the early skarns, perhaps related to emplacement of the pluton, became conduits for  24 hydrothermal fluids expelled from the cooling pluton, with subsequent precipitation of quartz and beryl. Marshall et al. (2004) also stated that preliminary stable isotopic data for beryl (structural O) were consistent with fluids originating from the nearby Lened pluton, and hence of magmatic derivation. They also concluded that Lened is a Type I (igneous-activity-related) emerald occurrence and that its similarities with the Tsa Da Glisza deposit (Groat et al. 2002, Neufeld 2004), 160 km southwest of Lened in the Yukon Territory, suggest that emerald occurrences in the northern Cordillera are likely related to igneous activity, although they conceded that both prospects also display some characteristics of schist-type emerald occurrences (Marshall et al. 2004). Contrary to this hypothesis is the Mountain River green beryl occurrence in the north-central Mackenzie Mountains of the Northwest Territories, 230 km north of Lened (Mercier 2008). As discussed in the introductory chapter, the Mountain River Beryl occurrence is an intriguing anomaly that represents a modified Colombian-type beryl (Hewton 2013).  To accurately evaluate criteria for further emerald exploration in northwestern Canada it is necessary to present a model of how beryl formed at Lened and how this fits with the regional lithological and tectonic framework. The objective of this study, therefore, is to evaluate the source of Be and chromophores in the emeralds at Lened and to classify the deposit in the context of magmatic (Type I), metamorphic (Type II), or Colombian (Type IIb) types (see Schwarz & Giuliani 2001 for more on this classification scheme.) In order to address the latter we integrate herein our field observations with whole rock geochemistry, mineral chemistry, and isotopic data. 3.2! LOCAL GEOLOGY  3.2.1!Sedimentary Rock  The lithology in the area of the Lened emerald showing consists of four major sedimentary units and the Lened granitic pluton that later intruded them (Fig. 17).  25 Drill logs from the 1970s record Precambrian turbiditic quartz-rich clastics of the Hyland group to the south and southwest of the Lened skarn (Sergerie 1979, Gordey & Anderson 1993).  The overlying Cambro-Ordovician Rabbitkettle Formation that hosts the various skarn bodies consists of dark grey, thin- to medium-bedded limestone with silty argillaceous layers, and some siliceous and dolomitic limestone that is locally hornfelsed and recrystallized.  Black siliceous mudstone grades into siliciclastic lithic pebble conglomerate (to lithic arenite) north of the Rabbitkettle formation and these are probably part of either the stratigraphically overlying Ordo-Silurian Duo Lake Formation (Road River Group, if present), or the Devono-Mississippian Portrait Lake Formation (Earn Group) that unconformably overlies these units to the north (the boundary has not been well defined; Gordey & Anderson 1993). Siliceous black mudstone is visibly altered (Fig. 18A) with with contact metamorphosed (hornfelsed) examples bearing occasional vivid green chlorite-group mineral porphyroblasts up to about 5 mm in length (Fig. 18B). More intensely altered mudstone hornfels has a light grey “bleached” appearance and slaty to phyllitic fabric in close (~5 m) vicinity to the skarn and emerald-bearing veins (e.g., Figs. 18B-F). The most intensely altered samples show development of radial aggregates of silvery-green muscovite that are either porphyroblasts, or infill of pyrite casts, which is suggested by their frequently equant, sometimes cubic morphology (Fig. 18D), and the occasional presence of pyrite fragments at the edges of muscovite crystals. Amphibole porphyroblasts are infrequently developed in some mudstone hornfels samples (Figs. 18E, F).  Regional Jurassic-Cretaceous contraction caused various scales of northwest-trending folding and thrust faulting seen in the area and resulted in an axial-plane cleavage fabric. At Lened, this fabric is apparent in variously skarnified limestone units, where it overprints bedding. 3.2.2!Lened Pluton  The above sedimentary units are intruded concordantly by the multi-phase Lened quartz monzonite/granite pluton that is part of the Selwyn Plutonic Suite (SPS). Plutons  26 of this suite are often associated with reduced W-skarn mineralization such as the Lened occurrence (Rasmussen 2013, Rasmussen & Mortensen 2013, Dick 1980). The southern margin of the Lened pluton developed minor endoskarn bodies proximal to exoskarn bodies (Glover & Burson 1987). One 10 cm-wide pegmatitic dike containing coarse scheelite was reported near outcropping skarn (Adie & Allen 1960), but it was not located in this study. Drill logs from each side of Lened Ridge reflect the intersection of more or less concordant quartz monzonite sills or plutonic apophyses of various thicknesses (1-25 m) within 30 m of the surface. These sills are reported to range from being highly competent and fresh to highly sericitized and decomposed (Davidson & Forster 1977, Burson 1979, Sergerie 1979). Drill hole 7L7 (1977, 1750 m elevation on Lened Ridge, azimuth 045°, dip -75°) intersected 65.5 m of “quartz monzonite” beginning at a depth of 90 m (Burson 1979). This intercept was assumed to be an apophyse of the Lened pluton proper. Sedimentary cover and skarn at Lened ridge forms a thin (0-200 m) veneer above the locally buried Lened pluton that is extensively intruded by dikes and feeders related to it. Contact metamorphism and a network of magmatic intrusions likely contributed to the prominent topology of Lened Ridge and its resistance to weathering.  3.2.3!Skarn  The skarn (and associated quartz veining) is located approximately 300 m northeast of the Western and Stephen’s scheelite-bearing skarn bodies studied by Glover & Burson (1987). The exoskarn body hosting the emerald-bearing quartz veins is a lens with a maximum length of ~60 m and apparent thickness of ~20 m (Figs. 19A-H). The skarn is developed in limestone of the Rabbitkettle Formation where it completely replaces carbonate minerals proximal to the contact with mudstone, and grades into argillaceous limestone with minor skarn alteration (10 m SW), and visibly unaltered limestone (>20 m SW; Figs. 19B, E, H). There is some skarnification of intercalated mudstone at the contact of the skarn body, and above the skarn contact there is evidence of skarn-related alteration (Fig. 18) and hornfelsed mudstone. The contact between skarn and black mudstone appears to be gradational and intact (Figs.  27 19C, D), and closer visual inspection did not reveal any evidence for shearing or other fault-related textures as proposed in the initial deposit model by Marshall et al. (2004).  The dominant skarn assemblage consists of pyroxene-garnet-amphibole ± wollastonite ± vesuvianite. Electron microprobe compositions of pyroxene, garnet, and amphibole are presented in Table 1. The skarn is weathered grey in outcrop and has a mottled grey-green texture with bands of brown garnet porphyroblasts (Fig. 20A). The Ca-rich garnet compositions are dominantly grossular (Table 1). The garnet is sometimes anisotropic and twinned, and occurs as subhedral to euhedral crystals (~1 mm) containing clinopyroxene and calcite inclusions. Minor green goldmanite (V-garnet) is found in the Western and Stephen’s skarn bodies (Fig. 17, Table 1), but was not identified in this skarn body. Clinopyroxene and amphibole occur as discrete prismatic crystals (to ~1 mm), as a very fine-grained (~5 µm or less) polygonal mosaic intergrown with calcite and wollastonite (Fig. 20B), and as fracture-fillings in garnet. Clinopyroxene crystals display light-colored rims and cores that contain opaques. The clinopyroxene compositions are primarily diopside, with common hedenbergitic (Fe2+) substitution (Table 1). Wollastonite and amphibole minerals frequently occur as radiating sheaves of prismatic crystals interstitial to clinopyroxene and poikiloblastic garnet (Fig. 20C). Amphibole compositions vary from magnesian (Mg = 2.671 apfu) to ferroan (Fe2+ = 2.357 apfu), sometimes with significant Ca content (Ca = 1.948 apfu), and notably elevated F to 0.458 apfu. Coarse-grained vesuvianite is locally present as disseminated crystals (~1 mm) in skarn and >1 cm bands of coarse-grained crystals in altered limestone and skarn (Fig. 20D). Pyrite and chalcopyrite are sparsely present as ca. 1 mm subhedral to euhedral crystals.  Minor rhythmic skarn-alteration and recrystallization of intercalated mudstone in limestone is the dominant facies >10 m from the skarn-mudstone contact (Fig. 20E) and sparse hexagonal opaque flakes presumed to be graphite were observed in thin section. Alteration of limestone outside of the skarn consists of recrystallization of remaining calcite and development of anhedral-euhedral aggregates of amphibole porphyroblasts (identified by powder X-ray diffraction, Fig. 20F). Beyond 20 m from the skarn contact, such alteration of limestone is no longer apparent.  28 3.2.4!Folding and Faulting  South of Lened, the Appler thrust fault places the Precambrian-Cambrian clastic units over the Cambro-Ordovician Rabbitkettle Formation. This steeply-dipping thrust fault can be traced for about 20 km, and is offset by a N-S strike-slip fault that extends ~3 km through Lened Ridge, causing ~100-200 m of displacement at the top of the emerald vein-bearing skarn outcrop (Fig. 17). Structural evidence that would expose and reveal the exact nature of folding and faulting is generally lacking due to talus cover. Folding and imbricate thrust structures on a decimeter scale are visible in the black mudstone (Fig. 18A) where pre-mineralization calcareous veins show tight isoclinal micro-folds (Fig. 19F) adjacent to the emerald-bearing skarn. Limestone above the skarn is tightly folded on a metre scale with parasitic folds (Fig. 20E), suggesting larger-scale folding of a similar nature. Clast-supported fault breccia was found in the N-S fault that transects the black mudstones (and arenite or pebble conglomerate at higher elevation on Lened Ridge). These rocks are composed of angular lithic fragments, feldspar, and strained undulose quartz (some exhibit growth zoning) in a limonitic to opaque groundmass with a banded and sometimes calcareous cement. Later quartz ± muscovite veinlets cut the fault breccia. 3.3! ANALYTICAL PROCEDURES The Philips XL30 scanning electron microscope (SEM) at the University of British Columbia, which is equipped with an energy-dispersion X-ray spectrometer (EDS), was used for preliminary examination of the electron-microprobe mounts. Electron-probe micro-analyses of beryl, tourmaline, muscovite, pyroxene, amphibole, and garnet were done on a fully automated CAMECA SX-50 instrument, operating in the wavelength-dispersion mode with the following operating conditions: excitation voltage, 15 kV; beam current, 20 nA; peak count time, 20 s (10s for V; 40 s for F, Cl); background count-time, 10 s (5s for V; 20 s for F, Cl); spot diameter, 5 µm. Data reduction was done using the 'PAP' φ(ρZ) method (Pouchou & Pichoir, 1985). For tourmaline, B was fixed at the nominal value (3.25 wt.%).   29 X-ray powder-diffraction data for mineral identification were collected over a range of 3 to 80° 2θ (scanning step of 0.04° 2θ) with CuKα radiation (35 kV and 40 mA) on a Bruker D8 Focus Bragg-Brentano diffractometer with graphite monochromator. Samples were powdered under ethanol with an agate mortar. Stable isotope analysis of minerals in the Lened granite, veins and shale was carried out at Queen’s Facility for Isotope Research, Queen’s University. The δ18O and δ13C ratios of calcite were determined by reacting approximately 1 mg of powdered material with 100% anhydrous phosphoric acid at 72 °C for 4 hours. The CO2 released was analyzed using a Thermo-Finnigan Gas Bench coupled to a Thermo-Finnigan DeltaPlus XP Continuous-Flow Isotope-Ratio Mass Spectrometer (CF- IRMS). δ18O and δ13C values are reported using the delta (δ) notation in permil (‰), relative to Vienna Pee Dee Belemnite (VPDB) and Vienna Standard Mean Ocean Water (VSMOW) respectively, with precisions of 0.2‰. Oxygen in silicate minerals was extracted from 5 mg samples at 550-600 °C according to the conventional BrF5 procedure of Clayton and Mayeda (1963) and analyzed via dual inlet on a Thermo-Finnigan DeltaPlus XP Isotope-Ratio Mass Spectrometer (IRMS). δ18O values are reported using the delta (δ) notation in units of permil (‰) relative to Vienna Standard Mean Ocean Water (VSMOW) international standard, with a precision of 0.1‰. Hydrogen stable isotope data for the emerald crystals were collected at CRPG/CNRS in Vandoeuvre (France) according to the procedure of Giuliani et al. (1997a). The crystals were first heated to 500 °C to ensure decrepetation of the fluid inclusions. The extraction of channel H2O was carried out by dehydrating the crystals in a vacuum with a methane-oxygen flame. D/H ratios were determined using a VG 602 D mass spectrometer and are reported relative to Standard Mean Ocean Water (SMOW) using conventional notation, where  is the relative difference in isotopic ratio between a sample and the standard, expressed in per mil (‰). The 1σ analytical precision is ±2.0‰ for D.  Whole-rock analyses of the granite and vein quartz were done by ALS Chemex Limited of North Vancouver. Lithium, Be, Cr, and Mo concentrations were determined by atomic absorption spectroscopy, B and Cl by neutron activation analysis, and F by specific ion potentiometry. All other elements were measured by induction-coupled  30 plasma mass spectrometry (ICP-MS) or X-ray fluorescence (XRF). Most major elements were analyzed by XRF, FeO by wet-chemical methods, and CO2 and H2O by infrared spectroscopy. Trace element data were obtained by ICP-MS and -ES (emission spectrometry). For 40Ar/39Ar dating, samples were wrapped in Al foil and placed in a canister. Irradiation was for 70 h using fast neutrons at the McMaster reactor. Single grain 40Ar/39Ar stepwise heating analysis was carried out using a LEXEL 3500 continuous 6W argon-ion laser. Argon isotopes were measured with a MAP 215-50 mass spectrometer equipped with a Nier source and a Johnston MM1 electron multiplier at the University of Montpellier. Measured argon values were corrected for blanks, atmospheric contamination, mass discrimination, and irradiation-induced mass interference. Radioactive decay of 37Cl and 39Ar were taken into account. Age calculations were done using constants recommended by Steiger & Jäger (1977) and McDougall & Harrison (1988). Errors shown in the tables and on the age spectra and isotope correlation diagrams represent the analytical precision at 2σ unless otherwise stated, assuming that the errors in the ages of the flux monitors are zero. This is suitable for comparing within-spectrum variation and determining which steps form a plateau (McDougall & Harrison 1988). A conservative estimate of this error in the J-value is 0.5% and can be added for inter-sample comparison. The date and J-values for the intralaboratory standard MAC-83 biotite is 24.36 Ma referenced to FCs sanidine at 28.02 Ma (Renne et al. 1998). The boron isotope composition of tourmaline from Lened was analyzed at the University of Manitoba using a Cameca IMS 7f ion microprobe using secondary ion mass spectroscopy (SIMS), a primary O- beam (~5 nA accelerated at 12.5 kV) with a ~15 µm beam diameter, a sample accelerating voltage of +10 kV, with the electrostatic analyzer set at +10 kV. The dectector was an ETP 133H electron multiplier coupled with an ion-counting system resulting in overall deadtime of 21 ns. The entrance slit was set at 36 µm with a mass-resolving power of 1450. Counts for 11B, 10B, and 30Si were collected in succession for 50 cycles with 1 s measurements for each isotope per cycle, 30 s pre-sputter time, with 0 V offset. A similar analytical procedure is described in Chaussidon & Albarède (1992). Instrumental mass fractionation and analytical  31 quality were assessed by replicate analyses of an elbaite tourmaline reference material, standard No. 98114 (11B/10B = 4.0014 ± 0.0007; Leeman & Tonarini 2001). Repeatability of the reference material was 0.4‰. Precision for the unknown sample during the sessions was ±0.3‰ (1σ). The B isotope composition is expressed in delta notation, as a per mil deviation from boric-acid standard NIST SRM 951 (11B/10B = 4.0437 ± 0.0033, Catanzaro et al. 1970): δ11B = [(11B/10B)sample/(11B/10B)SRM951 – 1]*1000.  The LA-ICP-MS analyses were carried out at the Masaryk University, Brno, using a laser ablation system Analyte G2 (Teledyne CETAC Technologies) connected to a sector field ICP-MS spectrometer Element 2 (Thermo Fischer Scientific). An ArF* laser ablation device equipped with a HelEx II sample cell was operated at a wavelength of 193 nm. The ablated material was carried by He flow (0.65 l.min-1) and mixed with Ar (~1 l.min-1) prior to entering the ICP-MS spectrometer. Optimization of LA-ICP-MS parameters was performed with the glass reference material NIST SRM 612 with respect to the maximum signal to background ratio and 248ThO+/232Th+ < 1. The hole drilling mode of laser ablation was used with spot diameter 110 µm, laser fluence 4–2, repetition rate 10 Hz, and the duration of 35 s for each spot or background. All element contents were normalized using Si as an internal standard after baseline correction and integration of the peak area. The resulting ranges for the main trace elements of interest are provided in Table 2.  3.4! EMERALD-BEARING QUARTZ-CARBONATE VEINS An array of ~26 sub-vertical emerald-bearing quartz-carbonate veins at Lened strike southwest and are hosted by a 20-30 m thick lens of the skarn (Fig. 19B). The skarn transitions upwards into less-altered, finely crystalline argillaceous limestone. The veins only occur in the skarn band, and pinch out rapidly at the boundary of the skarn (Fig. 19E). The vein-skarn contacts are sharp, suggesting the skarn was relatively brittle when the veins were emplaced (Fig. 21A). Minor sericite alteration occurs sporadically as patchy 5-10 cm dark haloes around some veins, whereas other veins  32 have a selvage of coarse muscovite (Fig. 21B), although in many examples the host skarn largely retains its fabric and mineralogy in the selvage. In contrast to the host sedimentary units, the veins are not folded (Figs. 19F, G). The veins are composed of quartz (85-90%), calcite (5%), muscovite (5%), beryl (locally up to 3%), scheelite (<1%), dravitic tourmaline (<1%), and traces of pyrite. Polycrystalline and euhedral quartz are both present, often with open space-filling textures characteristic of extensional veins (Fig. 19I). In many veins quartz forms lustrous euhedral crystals (<10 cm) that are often transparent at the tip. The quartz is frequently Dauphiné-twinned (Thomas & Wooster 1951) and horizontal striations perpendicular to the c axis separate alternating matte and lustrous surface textures. The quartz is often milky at its base and some examples have a light smoky colour. Internal rehealed fracturing is prevalent, and many crystal tips recovered in situ are broken, suggesting that late tectonic activity has closed open space in the veins. Muscovite is found at vein margins and as variously oriented cluster inclusions in quartz and calcite (Fig. 21B). The muscovite varies from white to pale silvery-green, forming thin crystals 1-10 mm in width. Blades of translucent-white calcite 1-10 mm thick are commonly intergrown with the quartz. The calcite blades radiate at all angles from the vein walls inward to the center of the veins.  Beryl occurs as discrete elongate prismatic crystals 0.1-5 mm by up to 5 cm (Figs. 21A, B, C); microcrystalline beryl is uncommon and forms a massive interlocking texture in one of the quartz-carbonate veins. The beryl ranges from colorless to light yellow, grassy green, and blue-green; fewer than one percent display a lively blue-green color. Colorless beryl inclusions in quartz are commonly associated with tourmaline (Fig. 21D). Most crystals are opaque to translucent, although gem-quality beryl of good clarity does occur (e.g., left-most crystal, Fig. 21C). Faceted gems of good saturation, but very light tone, and finished weights to 0.17 ct have been produced, with the darker-toned examples considered to be emerald (Fig. 22). Zoning is evident in thin section and larger opaque beryl crystals are visibly zoned in hand specimen. This zoning commonly takes the form of a beryl core, a rusty corroded rim around the core, and an outer zone of opaque green beryl.  33 Tourmaline (dravite) is a minor accessory phase and often occurs as needle-like euhedral inclusions in quartz and calcite in close proximity to beryl (Fig. 21D). Slightly smoky transparent quartz near the vein margin seems to preferentially host tourmaline, and this may represent a secondary quartz phase. The dravite inclusions are typically in the form of radiating sprays or individual broken segments of prismatic dravite. Crystals to 3 cm × 1 mm have been found, but most are 1 cm × 0.1 mm. Another mode of dravite is as 1-2 cm patches of parallel-growth aggregates (individual crystals 0.05-1 mm) that grow inward from the edge of the veins. The crystals are lustrous and transparent; many are grey-brown, while approximately 10% of the crystals obtained in this study are light grey with a dark blue cap. Dravite (and often associated microscopic beryl) crystals form inclusions that crosscut boundaries between calcite and quartz in all veins where tourmaline is found, suggesting that tourmaline (and microscopic beryl) mineralization formed early in the vein paragenesis, followed by quartz and calcite as infilling phases. In contrast to microscopic beryl associated with tourmaline, macroscopic beryl crystals (as in Fig. 21A) often terminate at faces of bladed calcite, suggesting there may be at least two generations of beryl mineralization. Scheelite is seen sporadically as 0.5-1 mm solitary white to creamy pink, and rarely brownish pink, grains which fluoresce a bright white-blue color under ultraviolet light (Fig. 21A). Coarse white- to creamy-pink subhedral scheelite to 1 cm is intergrown with quartz and occurs mostly near the vein margins.  Pyrite and pyrrhotite (1-5 mm) are somewhat uncommon and occur as euhedral cubes with striated faces and as anhedral blebs interstitial to quartz. Isolated crystals are often found in massive quartz near the vein margins.  3.5! CHEMISTRY OF VEIN MINERALS 3.5.1!Beryl  Eighty-eight electron microprobe compositions were obtained from 33 emerald samples; results of the analyses are given in Table 2.  Both V and Cr are chromophores in emerald. The average V concentration in the Lened crystals is 0.02 apfu (maximum 0.04 apfu), and the Cr concentrations are  34 negligible. The Mg content varies from 0.02 to 0.24 apfu (average 0.12 apfu), with slightly lower Mg (and higher Al) in the rims. The Fe content varies from 0 to 0.04 apfu (average 0.02 apfu). The crystals contain significant concentrations of Sc (up to 782 ppm). Sodium contents vary from 0.02 to 0.29 apfu (average 0.15 apfu) and there are small amounts of Ca, K, and Cs. Figure 23 shows Al versus the sum of other Y site (octahedral) cations from Lened compared to worldwide examples from the literature. The Lened compositions are at the high-Al (low substitutions) end of the range, and are similar to the compositions of the V-dominant emeralds from the Dyakou occurrence in China (Xue et al. 2010). Figure 24 shows the correlation between (Fe + Mg) and monovalent cations for the compositions from this study and similar V-rich emerald from the literature. Compositions that plot below the 1:1 line indicate that some of the Fe is present as Fe3+; for the Lened samples these compositions are mainly from the crystal rims. Compositions that plot above the 1:1 line suggest the presence of Li which cannot be measured with the electron microprobe. Though two trend lines in Fig. 24 appear to exist (which could suggest two compositional populations of beryl), the data points do not clearly correspond to separate crystals or core/rim relationships. Many of the Lened compositions, particularly from the cores and the intermediate parts of the crystals, plot above the line, in contrast to V-bearing emeralds from other worldwide localities. The equation Li = (Na + K + Cs) – (Mg + Fe) suggests a maximum of 0.08 Li pfu (average 0.01 Li pfu) for the Lened compositions. The LA-ICP-MS (Table 2) results show that unzoned crystals and the cores of zoned crystals contain ca. 800-1300 ppm Li, whereas the rims of zoned crystals contain ca. 280-380 ppm Li. The results also show slightly more Mg and Rb in the unzoned crystals and cores of zoned crystals and less V (ca. 1500-2000 vs. 2000-2500 ppm) and Cs (ca. 650-750 vs. 1200-1500 ppm). Elements responsible for the most color variation in worldwide emeralds are plotted as oxides in Figure 25. In most cases, the Cr2O3 content is much greater than that of V2O3; the main exceptions are for samples from Muzo, Colombia (V2O3 to 0.1 wt.%, Ottoway 1991), Dyakou in Malipo, China (V2O3 to 0.65 wt.%, Xue et al. 2010), and the Byrud Gård mine in Eidsvoll, Norway (V2O3 to 0.47 wt.%, Loughrey et al.  35 2013). The Lened compositions are all V-dominant, but extend almost all the way along the FeO-V2O3 edge of the plot. 3.5.2!Tourmaline  Selected compositions are given in Table 3. The average composition of Lened tourmaline based on the electron microprobe analyses is X(Ca0.029Na0.752□0.215)Y(Mg2.059Al0.252Fe2+0.555Fe3+0.039V0.062Ti0.025Cr0.003Mn0.003Zn0.003)Z(Al6.000)T(Si5.917Al0.083O18)(BO3)3[O27.13(OH)3.872F0.13]. The average V content is 0.06 apfu (maximum 0.11 apfu) which should be considered V-enriched, but is far below the vanadium dravite species (Henry et al. 2011). Chromium is only present at trace levels slightly above detection limits. The tourmaline is Na-rich at the X site which allocates it to the alkali group, and variation at the W site is limited almost entirely to the hydroxy-species field, with some compositional variation toward fluor- and oxy-species (Henry et al. 2011). The tourmaline is Mg-rich dravite (average 2.06 Mg pfu) with minor substition of YFe2+ and YAl (average 0.55 apfu Fe, and 0.25 apfu Al) and minor X-site vacancy (0.21 pfu), pushing the composition away from endmember dravite slightly towards schorl and oxy-dravite/magnesio-foitite (Fig. 26). 3.5.3!Dioctahedral mica The micas in the Lened veins are dioctahedral with average IVSi of 3.25 apfu (muscovite: 3.0-3.1 apfu), VIAl = 1.6 apfu (muscovite: 1.9-2.0 apfu), VIR2+/(VIR2++ VIR3+) = ~0.8-1.0 apfu (muscovite: < 0.25 apfu), and interlayer charge I = 0.93+ (Table 4). Tetrahedral silicon is higher than expected for endmember muscovite, and Al is lower. The high VIR2+ content (Fe, Mg) distinguishes these micas from pure muscovite. VIR2+ is far higher than the definition of muscovite, even if we consider that some of the iron may be trivalent, although this seems unlikely given the presence of reduced iron in the whole rock analyses, vein pyrite, and CH4 in fluid inclusions (Marshall et al. 2004). However, in the case that all iron is trivalent, Mg averages 0.35 apfu and the total average iron content is Fe3+: ~0.08 apfu. Even in this extreme case, the minimum VIR2+/(VIR2++ VIR3+) is ~0.8 apfu, whereas endmember muscovite limits the substitution of VIR2+ to < 0.25 apfu. As such, these dioctahedral micas show substitution that puts  36 them outside the International Mineralogical Association definition of muscovite (Rieder et al. 1998). The dioctahedral vein micas are best classified by plotting Si vs. R2+ (Fig. 27). Many of the analyses plot between muscovite and the “phengite” midpoint of the phengite series.  Fluorine content in the vein mica varies between 0-0.34 apfu, and averages 0.13 apfu. Vanadium averages 0.01 apfu to a maximum of 0.03 apfu. Cr2O3 is present in much lower concentrations, with an average 0.04 wt. % and maximum 0.32 wt.% (0.02 Cr pfu). 3.5.4!Stable isotope analyses of O-H-C-B Oxygen isotope data were obtained for quartz and biotite from the Lened pluton, and for quartz, calcite, and muscovite from the emerald-bearing veins (Table 5). The δ18O values for quartz from the Lened pluton average 13.3 ± 0.2‰ (n = 3) versus values of 15.4 and 15.5 for quartz from the emerald-bearing veins. Biotite from the granite (Table 5) averages 8.5 ± 0.6‰ (n = 3). The δ18O values for other vein mineral samples include two muscovites (10.1 and 11.2‰) and two calcites (10.7 and 11.2‰). Hydrogen isotope data were acquired for channel water (constituting 1.84-2.04 wt.%) from five beryl samples. The results show two populations of δD with respective averages of -63.3‰ (n = 3) and -86.3‰ (n = 2)(Table 5). Carbon isotope analyses for the two calcites yielded δ13C values of -4.8 and -5.2‰ (Table 5).  Seven in situ δ11B values were measured from a traverse of one representative tourmaline crystal, in addition to three more measurements from suitable spots on the same sample (Table 6). The average δ11B value is -4.9 ± 0.3‰ (1σ, n = 10, see Appendix for further details). 3.5.5!Whole-rock geochemistry  Major and trace-element geochemical data were obtained from samples of emerald vein, granite, black mudstone, limestone, clastic rocks, and skarn (surrounding the emerald occurrence), and are listed in Table 7.  37 The major element chemistry for the emerald-bearing vein reflects its dominant composition of quartz and calcite. The sample chemistries are dominated by SiO2 (80 wt.%) with lesser CaO (9.95 wt.%), CO2 (7.5 wt.%), C (2 wt.%), and Al2O3 (0.82 wt.%), which are attributed to calcite and muscovite. Vanadium (47 ppm) and Cr (180 ppm) are somewhat enriched and the bulk V/Cr ratio is 0.26. The black meta-mudstone unit is highly siliceous (>80 wt.% SiO2) and is composed largely of microscopic quartz fragments and a small amount of muscovite identified by powder X-ray diffraction. The total C content of the shale is measured as 0.09 wt.% or less, however this likely does not represent organic C as discussed later. Al2O3 (5.59-7.39 wt.%), K2O (1.81-2.36 wt.%), and Fe2O3 (1.17-1.75 wt.%) are the only other significant elements present. The conglomerate above the mudstone is geochemically very similar with 89.64 wt.% SiO2, 4.39 wt.% Al2O3, 1.38 wt.% K2O, and 1.81 wt.% Fe2O3. The dominant quartz content and low alkali component in the mudstone indicates that it is most geochemically similar to the Paleozoic meta- quartz arenite wacke, or meta-arkose fields defined by Saupé & Vegas (1987). The Lened siliceous mudstone has the appearance of a classic black shale, but a much higher alkali content is found in the well-known black shales of the central Pyrenées in France (K2O >2.5 wt.%, Saupé & Vegas 1987) and black shale from the Muzo emerald deposit in Colombia (Na2O >4.4 wt.%, Ottaway 1991).Vanadium is extremely elevated in the Lened mudstone, averaging 2200 ppm over five samples. Skarn at the contact with the black shale shows the highest V enrichment with 4670 ppm (sample HF-14, Table 7). Chromium is ten times less enriched than V in the shale (V/Cr = 10) with an average of 208 ppm Cr in the five shale samples. Granite samples are not enriched in V (average 24 ppm) and show slight enrichment in Cr (average 125 ppm). The Cr values are about five times more enriched than V in the granite. Some shale and clastic sedimentary samples are extremely elevated in Ba (~800-4000 ppm) and a clast-supported breccia sample (fault gouge?) contained 8.96 wt.% BaO. The Lened granite samples are somewhat high in Ba (214-921 ppm).  38 3.6! 40AR/39AR GEOCHRONOLOGY OF THE GRANITE AND EMERALD VEIN To resolve the timing of emerald-bearing vein formation relative to emplacement of the Lened pluton, the following samples were analyzed for 40Ar/39Ar ages: (1) biotites from the peripheral equigranular granite/quartz monzonite (DM-02-05) and from the inner fine-grained granite/quartz monzonite (DM-02-07); and (2) border muscovite from two emerald-bearing quartz veins (HF-22, HF-22B). The data are provided in Appendix 1A-1D and the age spectra are plotted in Figure 28. The biotite from the equigranular granite (DM-02-05) yielded an age spectrum that shows a monotonic decrease in ages from low- to high-temperature but with most steps centred at ca. 100 Ma. The data give a calculated plateau age of 99.73 ± 2.24 Ma (2σ, DM-02-05, Fig. 28) and isochron age of 101.59 ± 2.35 Ma. Biotite from the fine-grained quartz monzonite (DM-02-07) is similar to the first biotite age spectrum but has much smaller errors for the individual steps (DM-02-07, Fig. 28). The sample returned a slightly younger plateau age of 97.16 ± 1.24 Ma (2σ) and isochron age of 96.85 ± 1.14 Ma. We note that the plateau ages overlap within analytical error.  Muscovite from the first vein sample (HF-22) returned an age spectrum that is somewhat irregular and generally shows a monotonic decrease in age from low to high temperature. The data defined a plateau age of 98.32 ± 0.86 Ma (2σ) and isochron age of 98.59 ± 0.50 Ma (HF-22, Fig. 28). The second vein muscovite sample (HF-22B) yielded a more regular age spectrum which defines a plateau age of 98.98 ± 0.83 Ma (2σ) and an isochron age of 98.59 ± 0.79 Ma (HF-22B, Fig. 28). 3.7! DISCUSSION The origin of emerald mineralization at Lened is not immediately obvious due to the complex nature of the local geology. The relationship of vein, skarn, and granite emplacement will be discussed in further detail, using evidence from field relationships, geochemistry, and mineralogy to constrain the conditions of emerald formation. The only previous publication on the Lened beryl (Marshall et al. 2004) sought to characterize the occurrence using fluid inclusion microanalysis, oxygen isotope analysis of beryl and mineral chemistry of beryl. We have built on this work to  39 further constrain the origin of emerald using evidence from whole rock geochemistry of local lithologies; mineral chemistry of relevant minerals; observation of tourmaline and scheelite in veins; oxygen, hydrogen, carbon, and boron isotopic analyses of relevant minerals, and Ar-Ar age dating of vein and pluton micas. 3.7.1!  Age of the Lened pluton and the emerald-bearing veins The Lened pluton is the only likely heat source, and thereby magmatic fluid source, that could be implicated in formation of the emerald-bearing veins. Outside of the Lened contact aureole, basinal strata are essentially unmetamorphosed, precluding the possibility of a metamorphic emerald deposit (Gordey & Anderson 1993). Therefore, it is useful to discuss the thermochronology of the Lened pluton as a key to constraining the age and temperature of the emerald vein formation. Previous dating of the Lened pluton provided the following constraints on the timing of its emplacement: (1) 85.6 to 92.2 Ma (K-Ar biotite; Archibald et al. 1978); (2) 93 ± 1 (K-Ar biotite; Gordey & Anderson 1993); and (3) 95.0 ± 0.6 Ma (U-Pb) and 94.5 ± 0.8 (Ar-Ar biotite) (Rasmussen 2013). These latter ages contrast with the new Ar-Ar biotite (pluton) and muscovite (vein) data presented here which converge at ca. 100 Ma. However the samples described in Rasmussen (2011) from the Lened pluton, in particular the sample for the concordant zircon age at 95 Ma, were collected ~2000 m from the Lened skarn. Thus it is entirely possible that these younger dates relate to a later magmatic phase in the composite pluton, or the discrepancy simply reflects inherent differences in the analytical methods employed. More detailed integrated petrological and geochronological work is required to address this aspect.  The biotite ages for both phases of the granite are considered to represent the time of Ar blockage in the host mineral, which is estimated at ca. 300ºC (McDougall & Harrison 1988). The pluton is of high level, as indicated from its texture and overall setting (e.g., Rasmussen et al. 2005) which means cooling was likely rapid following emplacement, and the ages obtained are a good approximation of the age of emplacement of the pluton. The same can be inferred for the muscovite data (Ar blocking temperature cautiously estimated at ca. 350 °C, Mcdougall & Harrison 1988) and the results are considered to indicate emplacement of the emerald-bearing veins at  40 ca. 100 Ma. The essentially flat age spectra signify that these samples do not record a complex thermal history and were not significantly modified post-formation and initial closure. The ages clearly establish a connection between emplacement of the Lened pluton and emerald formation at 100 Ma and this provides the basis for a genetic relationship between the two which is further explored below. 3.7.2!  Muscovite chemistry and vein formation temperature  “Phengitic” substitution in white mica is negligible at 600 °C and increases with decreasing temperature (Monier & Robert 1986), therefore partial phengitic substitution in Lened mica suggests the veins formed below 600 °C in accordance with the Marshall et al. (2004) model. Moreover, the high R2+ character of the vein mica (apparent as solid-solution mixing lines in Fig. 27) indicates some trioctahedral substitution. Monier & Robert (1986) describe this biotitic substitution as common in low-temperature (300-400 °C) muscovites sourced from hydrothermally altered granitic rocks, and the fact that Lened vein mica displays such substitution suggests that it formed in the 300-400 °C range. 3.7.3!  Equilibration temperature and inferred !18OH2O of magmatic fluid  The δ18O data for quartz and biotite from the Lened pluton (Table 5) can be used to explore the crystallization temperature assuming equilibrium between these phases was maintained. The fractionation equation for quartz-annite (Zheng 1993b) yields an estimate for average equilibrium temperature of 453±15 °C (2σ), the lowest value is 372±15 °C for sample DM-07 and the highest value is 574±15 °C for sample DM-06. These results suggest that equilibrium was not retained during subsolidus cooling, which is not uncommon for granites and likely due to interaction of the biotite with a fluid (e.g., Sheppard 1986). These results are consistent with previous work that found the Lened pluton to have an apatite saturation temperature in the melt of 860 °C (Rasmussen & Mortensen 2013). Importantly the δ18O values for the three quartz samples analyzed are all similar at 13.3‰, whereas it is the biotite data that vary, which suggests it is this latter phase which has exchanged O post-crystallization (i.e. re-equilibrated). Using the quartz values, the Δ18Oquartz-H2O fractionation equation  41 calculated by several authors (Clayton et al. 1972, Bottinga & Javoy 1973, Matsuhisa et al. 1979, Zheng 1993a) yields average Δ18Oquartz-H2O values of 0.6‰ at 700 ºC and 1.7‰ at 600 ºC. Using these values gives δ18OH2O values of 12.7‰ and 11.6‰, respectively. Such enriched δ18OH2O values would equate to the Cornubian fluids of Sheppard (1986) that are attributed to fluids sourced from S-type granites. 3.7.4!  Equilibration temperature of the veins The temperature of emerald formation at Lened was broadly constrained by Marshall et al. (2004) using fluid-inclusion thermometric data which suggested vein crystallization temperatures of 300 to 600 °C. This study attempted to better constrain the emerald formation temperature using oxygen isotope thermometry and carefully selected mineral pairs from vein samples. The use of quartz-muscovite and quartz-calcite mineral pairs yielded temperatures of 355±15 ºC and 266±10 ºC, and 185±20 ºC and 191±20 ºC, respectively (Table 5). However, the wide range of the data suggests that equilibrium was not attained (or was lost) among these minerals. In this regard we note that whereas the quartz δ18O values are very similar (15.4 and 15.5‰), the two muscovite samples yielded values of 11.2 and 10.1‰ and that the two calcite values are similar at 11.2 and 10.7‰. We cautiously interpret these data to indicate the following: (1) the higher temperature (355±15 °C) for one of the quartz-muscovite pairs provides the best approximation of the conditions of emerald vein formation, with the lower value (266±10 °C) reflecting equilibration of the muscovite to lower temperatures after emerald mineralization; and (2) the calcite data also reflect equilibration to lower temperatures, which is not uncommon for this phase. 3.7.5!  O, H stable isotopic composition of the vein-forming fluid The origin and character of the mineralizing fluid can be constrained by the D value of the emerald channel water, and by calculating the 18O value of H2O in equilibrium with quartz and emerald at the temperature of formation (which, based on the above discussion, is considered to be about 350 ºC). The following discussion is therefore based on quartz and beryl data from this study and the literature; the other phases are considered less reliable. Marshall et al. (2004) measured δ18O (structural O)  42 beryl values ranging from 12.4 to 14.05‰. At vein formation temperatures of 350 °C, the calculated δ18OH2O range from the beryl is 12.9-14.55‰ (∆qtz-brl = -0.5, Zheng 1993a, Fig. 30). This is enriched compared to the granitic fluid value calculated above (avg. granite δ18OH2O = 12.2‰) and might be interpreted to suggest that 18O enrichment was caused by fluid-rock interaction by percolation of fluids through metalimestone and metasediment prior to, or during vein emplacement (Bowman et al. 1985, Veizer & Hoefs 1976, Giuliani 1997b). Alternatively, it is very likely the Zheng (1993a) beryl-H2O calibration may be inaccurate as it is theoretical. Vein quartz analyzed in this study may be interpreted in a similar fashion. Using the δ18O quartz values of 15.5 and 15.4‰, and the assumed temperature of vein formation of 350 ºC, δ18OH2O is calculated as 10.2 and 10.1‰ (Matsuhisa et al. 1979). These values compare to the δ18OH2O values of 12.7 and 11.6‰ calculated for the fluid in equilibrium with granitic quartz described above (Fig. 30). The lighter vein δ18OH2O values may be attributed to crystallization of quartz and other relatively isotopically heavy vein minerals prior to the igneous fluid reaching the site of emerald vein formation (i.e. fluid evolution), or there may have been fluid mixing with an 18O-depleted fluid such as meteoric water. Figure 30 also shows the relative influence of analytical error (2σ) and sensitivity of temperature assignment.  Error on the isotope equilibration temperatures and fluid composition estimates results from analytical error in measuring the samples, as well as (often unquantified) error built in to the fractionation equations from the literature. Only analytical error has been taken into account here. The δDH2O of emerald channel water and calculated δ18OH2O are plotted with other granite-related and Canadian deposits in Figure 29. The range of δDH2O measured in emerald channel water at Lened (-87.4 to -62.0‰) is within the range defined for S-type granitic magmatism (i.e., Cornubian, Sheppard 1986) and is comparable to depleted values associated with other granitic intrusions such as Tsa Da Glisza (-62.1 < δDH2O < -55.8‰, Groat et al. 2014), the Australian deposits at Emmaville (δDH2O = 83.4‰) and Torrington (δDH2O = -89‰, Loughrey et al. 2012), Ianapera in Madagascar (-86 < δDH2O < -62‰, Giuliani et al. 2015), and Dyakou (δDH2O = -89‰, Xue et al. 2010). Giuliani et al. (1997b, 2015) discusses several potential causes of δD-depleted  43 channel waters that are compatible with Lened including (1) input of meteoric water, (2) H-exchange with D-depleted organic molecules, and (3) presence of F which is known to contribute to D/H fractionation (Richet et al. 1977). As discussed above, the calculated δ18OH2O is also compatible with a contribution of meteoric water. Hydrogen exchange may have occurred via volatilization of organic matter in the black siliceous sediments (or distal sedimentary rocks) during contact metamorphism. There is also evidence of F in the mineralizing fluid given by elevated F in vein muscovite (up to 0.33 apfu), and skarn amphibole (up to 0.458 apfu). 3.7.6!  Vein emplacement Late-stage quartz veining is seen in many tungsten skarns including Cantung, Mactung, Lost River in Alaska, and Feie’shan in China (Sainsbury 1963, Dick & Hodgson 1982, Kwak 1987, Newberry 1998, Yuvan 2006, Liu et al. 2017). This observation strongly suggests that the geochemical processes occurring during contact metamorphism, metasomatism, and skarn development can be genetically important for the development of such quartz veins. The formation of pyroxene and garnet at Lened requires significant decarbonation of the host rock and a commensurate large positive volume change, leading to fluid overpressuring, and release of fluid if the local lithostatic pressure is exceeded (Valley 1986). Vein emplacement at Lened must have been accommodated by either (1) inherent structural properties of unaltered limestone vs. mudstone during deformation, (2) an initial phase of skarn development by thermal diffusion creating a brittle carapace in advance of significant overpressuring from metasomatic decarbonation, or (3) contemporaneous metasomatic skarn formation, embrittlement, and overpressuring. The δ13C value of vein calcite (ca. -5‰) is such that a significant input of marine carbonate C to the vein-forming fluid is implied, and this is consistent with the vein emplacement being related to CO2 devolatilization of carbonates. 3.7.7!  Sources of Be, B, and the origin of the emerald vein parental fluid Beryllium and B are variously enriched in W-Sn skarns. For example, the Lost River, Alaska Sn-skarn has unusually high concentrations of B (750 ppm) and Be (3500  44 ppm) in averaged representative specimens, whereas the Cantung and Mactung reduced-W skarns have no measured B and low amounts of Be (26-28 ppm) (Sainsbury 1963, Newberry 1998). Despite low reported B in both the Mactung and Cantung skarns, there is definitely B in the system, as reflected by the presence, albeit volumetrically insignificant, of tourmaline in aplite dikes (Cantung) and quartz veins (Mactung) (Zaw 1976, Dick & Hodgson 1982, Rasmussen et al. 2011). Similarly, at Lened only a vanishingly small amount of Be and B would have been required to form the small amount of beryl and tourmaline, respectively, that occurs in the veins. Boron is a common element of magmatic origin in W skarns (Newberry 1998) and a granitic fluid is likely the source of B at Lened. Alternatively, the B could have been sourced from local mudstone (B = 240 ppm), although it is possible that the elevated B in the mudstone is inherited from metasomatic skarn alteration by magmatic fluid. The B isotopic composition of the Lened tourmaline (δ11B of -3.1 to -6.6‰) is higher than the magmatic-hydrothermal tourmaline at nearby Tsa da Glisza (δ11B of -15.6 to -4.2‰, Galbraith et al. 2009) but this is still within the permissible range for tourmaline associated with granite (Fig. 31; Jiang & Palmer 1998). Boron isotopes of tourmaline alone are not conclusive in determining whether the source of B was (meta?)-sedimentary or igneous, but based on this evidence it is probable that the B has a magmatic-hydrothermal origin. Other major elements in Lened tourmaline plot in the field of metasedimentary rocks in the discriminant diagram of Henry & Guidotti (1985, Fig. 26), suggesting Mg contribution from local carbonates. Beryllium, unlike B, is an incompatible element that was likely sourced from the terminal stages of crystallization of the inferred progenitor intrusion, the ca. 100 Ma Lened pluton. It is likely that the emerald vein parental fluids were highly evolved magmatic-hydrothermal fluids enriched in the incompatible or mobile elements W, Sn, Be, Li, F, and B. Beryllium is known to speciate with Cl, F, F-carbonate, and F-hydroxide complexes in magmatic-hydrothermal environments (Wood 1992). Chlorine and F were present in the Lened vein-forming fluid as shown by the presence of Cl in fluid inclusions (Marshall et al. 2004), and elevated F contents for vein and skarn minerals (this study). At Lened it is probable that Be was transported by F (and possibly Cl) complexes in low-pH magmatic-hydrothermal fluids that were destabilized after  45 interaction with local carbonates (resulting in pH increase, and decrease in F/Cl activity) and precipitated beryl, as is understood to occur in other Be-bearing skarns (Wood 1992, Newberry 1998). 3.7.8!  V-rich sedimentary rock as a chromophore source Vanadium is the main chromophore for Lened emerald where V is largely concentrated in the minor vein minerals beryl, muscovite, tourmaline, and not the quartz and calcite phases which make up ~90 vol.% of the veins. The two potential sources of V are the Lened pluton (24 ppm) and a local V-rich sedimentary unit (V > 2000 ppm, see below). Chromium and V have similar mobility and mineralogical availability, particularly in emerald (Groat et al. 2008). Therefore, the V/Cr ratio has the potential to distinguish between reservoirs of these elements. In this case, the V/Cr signatures are very different for the granite (~0.21), the skarn hosting the emerald veins (0.59), the Lened skarn (1.47), and the black mudstone (9.46). V/Cr in the vein minerals shows that V/Cr in emerald (~10-20), muscovite (~1-10), and dravite (~5-10) are all more consistent with a sedimentary source of V and Cr. The contribution of V from a sedimentary source was clearly a key aspect in formation of emerald at Lened and a discussion of the precise source is merited. Vanadium is commonly elevated in organic-rich mudstone and black shale. Previous workers correlated Lened “black shale” (here described as black siliceous mudstone) with the “Road River Formation” and named it the “Dracula Formation” due to several imposing black clastic spires (see Fig. 19A) formed in resistant fault gouge, apparently reminiscent of vampires when shrouded in misty mountain weather (Wise 1973). Duo Lake Formation (Road River Group) mudstone from the Howards Pass Zn-Pb district of the Yukon/Northwest Territories (~100 km NW of Lened) overlies Rabbitkettle limestone and the “Active Member” or “Lower Cherty Member” may correlate with the Lened mudstone. These members are geochemically very similar to the Lened mudstone with high silica (SiO2 >80 wt.%), less than 2% each of Al2O3 and (Na2O + K2O), and very high V concentrations (up to 2599 ppm) correlated with high total organic carbon (TOC) contents (up to 16.48 wt.%) (Slack et al. 2017). A potentially problematic difference for this comparison is that the Lened mudstone chemical  46 analyses returned very low C (<0.09 wt.%). This is a surprising result given the sooty carbonaceous appearance of the Lened mudstone; and it is black and virtually opaque in thin section. Notably, the loss on ignition (LOI) for mudstone is high with average 7.9 wt.% (n = 5), but the sum of volatiles H2O, CO2, and measured C together only average 1.847 wt.% (n = 5), which precludes a high carbonate or structural water loss. Vanadium content and LOI appear to be positively correlated in the mudstone (see Table 6A); an example of this relationship is sample HF-12 which has the highest LOI (12.95 wt.%) and V (3170 ppm), as would be expected if the LOI largely represents volatilization of a V-bearing organic C phase. Based on the high LOI that is not accounted for by volatiles and measured C, it is possible that there is more C of organic origin present in the Lened mudstone than explicitly stated by the present geochemical analysis. Further analysis with attention to organic carbon and graphite content should be conducted to confirm this result. Alternatively, the V in altered mudstone represents a skarn alteration front, in which case V has probably been remobilized from a hidden organic-rich sedimentary source in the area. Indeed, the presence of V-rich garnet (i.e., goldmanite) in skarn is further evidence of the ingress of a V-bearing fluid to this system. In either case the source of the V is interpreted to be sedimentary. 3.7.9!  Conclusions Lened is a unique Type I, skarn-hosted igneous emerald occurrence. The beryl is inferred to have formed in late-stage magmatic-hydrothermal quartz veins constrained to ca. 100 Ma based on Ar-Ar dating of vein muscovite. The emeraldiferous quartz veins likely relate to emplacement of the proximal Lened pluton and development of the Lened tungsten skarn. Vein emplacement occurred during or after skarn development and this is consistent with the identical Ar-Ar ages for vein muscovite and magmatic biotite. Isotopic data for the most reliable quartz-muscovite pairs suggest a vein formation temperature of 355±15 ºC (2σ), which agrees with the lower values from earlier fluid inclusion thermometric data and muscovite mineral chemistry.  The Be in the beryl is likely of magmatic origin for the following reasons: (1) Be is commonly associated with mineralizing fluids in W, Sn, and F skarns (e.g., Lost River, Alaska); (2) the presence of coarse scheelite and elevated Sn values for the  47 emerald veins strongly suggest that incompatible elements such as Be would be concentrated in magmatic skarn-forming fluid (which has been shown to be the main component in vein-forming fluid); and (3) the elevated Li content of the beryl is most consistent with an igneous origin. The Be was likely transported in low-pH magmatic hydrothermal fluid as F- and Cl-complexes. Interaction of this fluid with local carbonate rock during skarn metasomatism would have destabilized these complexes by raising pH and lowering the F- and Cl-activities, resulting in beryl precipitation.  Vanadium, the main chromophore for the Lened emeralds, was sourced from the adjacent mudstone or a hidden V-rich sedimentary source. The V was likely mobilized from organic matter or V-rich clay minerals by thermal breakdown and metasomatism related to pluton emplacement.  Calculated δ18OH2O values of ca. 10‰ for the vein fluids (at 350 ºC, δ18Oquartz) are compatible with a peraluminous granitic fluid source; the values are slightly isotopically lighter than fluids calculated to be in equilibrium with the Lened pluton (δ18OH2O = ~12‰; magmatic quartz, 600-700 °C) which can be explained as the result of fractionation during vein crystallization or mixing with 18O-depleted waters. The δD of emerald channel water (δDH2O = -87.4‰ to -62.0‰) is similar to other emerald occurrences related to S-type granitic magmatism. Magmatic fluid exsolved during cooling and crystallization of the Lened pluton, and incompatible elements such as W, Sn, Be, Li, B, and F partitioned into the fluid phase. Magmatic-hydrothermal fluid infiltrated country rocks, leading to extensive skarn mineralization, carbon dioxide release, and volume increase. The exposed veins at Lened are a series of en echelon quartz-calcite-beryl-scheelite-tourmaline-pyrite veins that record a brittle rupture event of primarily magmatic-hydrothermal fluid through an early skarn carapace. Metasomatism of local mudstone and the commensurate release of V was therefore an integral part of the process which led to the formation of emerald. Lened is, at the moment, a unique igneous skarn-hosted emerald occurrence.    48 4!  Conclusions 4.1! MAIN FINDINGS The obvious first step in exploring for Colombian-type emerald in northern Canada is to apply the techniques used successfully in Colombia. Numerous prospective areas in northern Canada have been delineated by this study on the basis of quantitatively anomalous Na, Be, Cr + V, and REEs in silt geochemistry within black shale units. Qualitatively, other considerations have been discussed, such as proximity to known fault structures. There are important lithological similarities between black shales in the Selwyn Basin and those of the Colombian emerald districts. Perhaps the most important difference pertaining to emerald potential in northern Canada is the lack of evaporite occurrence density compared to Colombia’s Eastern Cordillera where salt diapirs and gypsum occurrences are commonplace. Nonetheless, the Mountain River Beryl locality parental fluids are thought to be evaporite-derived brines, and it is significant that suitable conditions for hydrothermal emerald were achieved at least once in the Mackenzie Mountain fold and thrust belt. Based on silt geochemistry I have identified several regional scale targets north of Dawson City and in the Mackenzie Mountains northwest of Macmillan Pass. Field checks of MRB and the Rusty Shale Formation led to the conclusion that small beryl showings can be easily missed, and the designation “black shale” is too vague for exploration purposes. More precise criteria would be desireable (e.g. regarding levels of organic matter, and phosphate).   49 Lened is a unique skarn-hosted hydrothermal emerald occurrence (~100 Ma) in which Be was provided by a nearby granite pluton of similar age. The chromophore V was provided by local black shale/mudstone which suggests similar V-rich sedimentary rocks throughout Selwyn Basin represent a significant emerald chromophore reservoir.  4.2! LIMITATIONS Limitations of regional stream sediment survey data include low sample density and uncertainty of how well different analytical techniques might identify Na in albite. For example, there is no high resolution sampling in the vicinity of MRB, making it difficult to factor in any potentially distinctive “MRB-style” silt/soil geochemistry. It should be noted that companies with extensive field report collections and higher resolution silt or soil geochemical databases covering the prospective areas may already have essential data that could identify potential emerald deposits.   Traverses described herein only covered a very limited area and are clearly not exhaustive prospecting campaigns.  4.3! FUTURE WORK Field checking of all the prospective anomalies identified in this work would be a valuable exercise that could help refine the Colombian-type emerald exploration model or even lead to the discovery of new beryl occurrences. Ideally, workers already in these remote locations for mineral exploration or other work should watch for signs of mineralization.  Additional fluid inclusion work on MRB and Lened would be valuable to build on the work of Dan Marshall and others. It is of great academic interest to confirm whether the small showing at MRB is unique and definitively of sedimentary-hydrothermal origin as it seems. It should be noted that MRB has not been worked for specimens and it may yield facet grade material if new veins are exposed. I have noted microscopic (<1 mm) euhedral cavity-filling emerald of good colour and clarity that may indicate potential for better material.   50 With regard to future emerald exploration in the Selwyn Basin and Mackenzie Platform, it would be of great value to acquire four-acid digestion re-analysis of the YGS silt sample database if any splits of samples remain. Automated mineralogical analysis of these samples would also be of great interest in identifying emerald pathfinder minerals. Three novel emerald exploration tracks may be followed in the Selwyn Basin and Mackenzie Platform: (1) Colombian-type occurrences in black shale (2) MRB-type emerald occurrences, and (3) Lened-type emerald occurrences at the margin of Cretaceous SPS plutons. If the goal of future explorers is to discover emerald of any genetic type (not only Colombian-type), all of these models should be considered.   51 Tables  Table!1.!Average&and&Representative&Compositions&of&Skarn&Minerals&at&Lened !! !!Pyroxene! ! ! !!!!!!!!!Amphibole! ! ! ! !!!Garnet! !! !!! Avg.! St.$Dev.! Min.! Max.! Avg.! St.$Dev.! Min.! Max.! Grossular! ! ! Goldmanite+(Lened+Skarn+)!!! n"="8! n"="8! n"="8! n"="8! n"="6! n"="6! n"="6! n"="6! 17!1! 17!2! 17!3! 14B!1! 14B!2!SiO2!(wt%)! 52.99! 0.69! 52.30! 54.10! 48.25! 1.85! 45.55! 50.38! 38.59! 38.61! 38.22! 35.92! 36.18!TiO2! 0.01! 0.02! 0.00! 0.05! 0.24! 0.03! 0.21! 0.28! 0.53! 0.21! 0.79! 0.36! 1.03!Al2O3! 0.27! 0.08! 0.20! 0.44! 5.60! 1.48! 3.72! 7.69! 20.76! 20.89! 20.78! 3.93! 6.44!V2O3! !        0.05! 0.06! 0.02! 22.80! 20.60!Cr2O3! 0.02! 0.03! 0.00! 0.07! 0.01! 0.01! 0.00! 0.01! 0.00! 0.04! 0.03! 2.56! 0.97!Fe2O3(min.)! 8.23! 2.31! 4.11! 10.55! 3.32! 0.79! 2.55! 4.28! 3.52! 3.83! 3.08! 0.86! 0.22!FeO(max.)! !    15.41! 2.22! 13.31! 18.41! !     MnO! 0.72! 0.36! 0.08! 1.09! 0.81! 0.08! 0.76! 0.97! 0.38! 0.30! 0.26! 0.21! 0.14!MgO! 12.67! 1.76! 11.02! 15.79! 10.57! 1.64! 8.16! 12.22! 0.11! 0.08! 0.16! 0.15! 0.25!CaO! 25.02! 0.33! 24.62! 25.52! 11.91! 0.11! 11.77! 12.05! 36.50! 36.37! 36.35! 33.50! 33.84!Na2O! 0.06! 0.02! 0.02! 0.09! 0.80! 0.17! 0.55! 0.98! !     K2O!     0.48! 0.12! 0.37! 0.68! !      52 !! !!Pyroxene! ! ! !!!!!!!!!Amphibole! ! ! ! !!!Garnet! !! !!! Avg.! St.$Dev.! Min.! Max.! Avg.! St.$Dev.! Min.! Max.! Grossular! ! ! Goldmanite+(Lened+Skarn+)!!! n"="8! n"="8! n"="8! n"="8! n"="6! n"="6! n"="6! n"="6! 17!1! 17!2! 17!3! 14B!1! 14B!2!F!     0.75! 0.18! 0.52! 0.97! !     Cl!     0.03! 0.02! 0.00! 0.04! !     H2O**!     1.64! 0.06! 1.55! 1.72! !     !(O#=#F,Cl)! ! ! ! !0.32! 0.07! !0.41! !0.23! ! ! ! ! !Total! 99.99! 0.25! 99.71! 100.40! 99.48! 0.63! 98.95! 100.58! 100.44! 100.39! 99.70! 100.30! 99.67!! ! ! ! ! ! ! ! ! ! ! ! ! !Si4+!(apfu)! 1.990! 0.005! 1.983! 2.000! 7.219! 0.172! 6.972! 7.456! 2.975! 2.982! 2.959! 2.944! 2.932!IVAl! 0.009! 0.004! 0.000! 0.014! 0.781! 0.172! 0.544! 1.028! 0.025! 0.018! 0.041! 0.056! 0.068!VIAl! 0.003! 0.003! 0.000! 0.010! 0.210! 0.109! 0.074! 0.359! 1.861! 1.883! 1.855! 0.324! 0.548!Ti4+! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.027! 0.003! 0.023! 0.031! 0.031! 0.012! 0.046! 0.022! 0.063!Cr3+! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.000! 0.003! 0.002! 0.166! 0.062!V3+! !        0.003! 0.004! 0.001! 1.498! 1.338!*Fe3+!! 0.017! 0.012! 0.000! 0.036! 0.373! 0.084! 0.294! 0.481! 0.102! 0.111! 0.090! 0.026! 0.007!Fe2+!! 0.242! 0.076! 0.108! 0.307! 1.932! 0.309! 1.651! 2.357! 0.000! 0.000! 0.000! 0.000! 0.000!Mn2+! 0.023! 0.012! 0.003! 0.035! 0.103! 0.009! 0.096! 0.122! 0.025! 0.020! 0.017! 0.015! 0.009!Mg2+! 0.709! 0.088! 0.624! 0.864! 2.354! 0.331! 1.862! 2.671! 0.013! 0.010! 0.019! 0.019! 0.031!Ca2+! 1.007! 0.005! 0.999! 1.014! 1.909! 0.027! 1.879! 1.948! 3.015! 3.010! 3.015! 2.942! 2.939! 53 !! !!Pyroxene! ! ! !!!!!!!!!Amphibole! ! ! ! !!!Garnet! !! !!! Avg.! St.$Dev.! Min.! Max.! Avg.! St.$Dev.! Min.! Max.! Grossular! ! ! Goldmanite+(Lened+Skarn+)!!! n"="8! n"="8! n"="8! n"="8! n"="6! n"="6! n"="6! n"="6! 17!1! 17!2! 17!3! 14B!1! 14B!2!Na+! 0.004! 0.002! 0.002! 0.006! 0.091! 0.027! 0.052! 0.121! !     ANa+!     0.141! 0.074! 0.058! 0.239! !     K+!     0.092! 0.024! 0.071! 0.132! !     F!     0.352! 0.083! 0.250! 0.458! !     Cl!     0.007! 0.004! 0.000! 0.010! !     (OH)!     1.641! 0.080! 1.542! 1.740! !     !Note:&The&following&standards&were&used:&topaz&(FKα)"#albite#(NaKα)"#kyanite#(AlKα)"#diopside#(MgKα)"#diopside#(SiKα)"#scapolite#(ClKα)"#orthoclase#(KKα)"#diopside#(CaKα)"#rutile#(TiKα)"#vanadium#element#(VKα)"#synthetic#magnesiochromite#(CrKα)"#synthetic#rhodonite#(MnKα)"#and#synthetic#fayalite#(FeKα).##!Pyroxene(compositions(were(normalized(on(the(basis(of(4(cations(and(6(O.(Amphibole(compositions(were(normalized(on(the(basis(of#13#cations,#and#23#anions!(O,$OH,$F,$Cl).$**H2O"was$calculated$assuming$(OH$+$F$+$Cl)$–!2"apfu.!*Pyroxene)and)amphibole)Fe3+!was$estimated$with$the$formula$of$Droop$(1987).$Garnet$Fe$was$considered$to$be$entirely$Fe2+.!!!! 54 Table!2.!Average&Compositions&of&Emerald(Samples(from(Lened(Quartz(Veins!!! All! All! All! All! Core! Core! Core! Core! Inter.! Inter.! Inter.! Inter.! Rim! Rim! Rim! Rim!! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.!n"! 88! 88! 88! 88! 28! 28! 28! 28! 17! 17! 17! 17! 28! 28! 28! 28!SiO2!(wt.%)! 64.71! 0.56! 63.07! 65.87! 64.47! 0.56! 63.07! 65.64! 64.48! 0.66! 63.15! 65.24! 64.88! 0.42! 64.16! 65.87!Al2O3! 17.23! 0.47! 16.13! 18.73! 17.18! 0.54! 16.13! 18.62! 17.00! 0.44! 16.23! 17.62! 17.35! 0.44! 16.65! 18.73!Sc2O3! 0.03! 0.02! 0.00! 0.12! 0.02! 0.03! 0.00! 0.12! 0.03! 0.02! 0.00! 0.07! 0.03! 0.02! 0.00! 0.06!V2O3! 0.23! 0.11! 0.06! 0.52! 0.24! 0.13! 0.06! 0.51! 0.22! 0.13! 0.06! 0.45! 0.20! 0.07! 0.07! 0.35!Cr2O3! 0.01! 0.01! 0.00! 0.05! 0.01! 0.01! 0.00! 0.04! 0.01! 0.01! 0.00! 0.05! 0.01! 0.02! 0.00! 0.05!BeO*! 13.54! 0.11! 13.26! 13.76! 13.51! 0.10! 13.36! 13.76! 13.48! 0.12! 13.26! 13.63! 13.55! 0.09! 13.40! 13.76!MgO! 0.88! 0.25! 0.13! 1.76! 0.96! 0.32! 0.27! 1.76! 0.93! 0.19! 0.69! 1.27! 0.78! 0.21! 0.13! 1.09!CaO! 0.02! 0.02! 0.00! 0.18! 0.04! 0.04! 0.00! 0.18! 0.02! 0.01! 0.00! 0.04! 0.01! 0.01! 0.00! 0.03!FeO! 0.26! 0.14! 0.00! 0.55! 0.27! 0.13! 0.03! 0.52! 0.29! 0.15! 0.07! 0.55! 0.27! 0.13! 0.00! 0.46!Na2O! 0.82! 0.28! 0.13! 1.64! 0.96! 0.30! 0.13! 1.64! 0.89! 0.27! 0.23! 1.19! 0.67! 0.24! 0.18! 1.03!K2O! 0.02! 0.02! 0.00! 0.18! 0.03! 0.04! 0.00! 0.18! 0.02! 0.01! 0.01! 0.03! 0.01! 0.01! 0.00! 0.03!Cs2O! 0.10! 0.04! 0.00! 0.19! 0.08! 0.04! 0.01! 0.19! 0.10! 0.04! 0.03! 0.15! 0.11! 0.04! 0.00! 0.17!H2O**! 1.54! 0.24! 0.95! 2.23! 1.65! 0.26! 0.95! 2.23! 1.59! 0.23! 1.03! 1.85! 1.40! 0.20! 0.99! 1.71!Total! 100.45! 0.91! 98.01! 101.87! 100.64! 0.85! 98.01! 101.83! 100.81! 1.01! 98.15! 101.87! 100.33! 1.01! 98.27! 101.86!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !Si4+!(apfu)! 5.969! 0.018! 5.868! 5.998! 5.958! 0.024! 5.868! 5.981! 5.974! 0.017! 5.937! 5.998! 5.978! 0.007! 5.961! 5.989!Al3+! 1.873! 0.044! 1.775! 2.020! 1.871! 0.051! 1.777! 1.992! 1.856! 0.044! 1.775! 1.912! 1.884! 0.043! 1.810! 2.020! 55 !! All! All! All! All! Core! Core! Core! Core! Inter.! Inter.! Inter.! Inter.! Rim! Rim! Rim! Rim!! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.! Avg.! Std.%Dev.!Min.! Max.!n"! 88! 88! 88! 88! 28! 28! 28! 28! 17! 17! 17! 17! 28! 28! 28! 28!Sc3+! 0.002! 0.002! 0.000! 0.010! 0.002! 0.002! 0.000! 0.010! 0.003! 0.002! 0.000! 0.006! 0.002! 0.001! 0.000! 0.005!V3+! 0.017! 0.008! 0.004! 0.038! 0.018! 0.009! 0.004! 0.037! 0.017! 0.010! 0.004! 0.033! 0.015! 0.005! 0.005! 0.026!Cr3+! 0.001! 0.001! 0.000! 0.004! 0.001! 0.001! 0.000! 0.003! 0.001! 0.001! 0.000! 0.004! 0.001! 0.001! 0.000! 0.004!Be2+! 3.000! ! 3.000! 3.000! 3.000! ! 3.000! 3.000! 3.000! ! 3.000! 3.000! 3.000! ! 3.000! 3.000!Mg2+! 0.121! 0.034! 0.018! 0.243! 0.132! 0.044! 0.037! 0.243! 0.128! 0.026! 0.094! 0.176! 0.107! 0.029! 0.018! 0.150!Ca2+! 0.002! 0.002! 0.000! 0.018! 0.004! 0.004! 0.000! 0.018! 0.002! 0.001! 0.000! 0.004! 0.001! 0.001! 0.000! 0.003!Fe2+! 0.020! 0.011! 0.000! 0.043! 0.021! 0.010! 0.002! 0.041! 0.022! 0.012! 0.005! 0.043! 0.021! 0.010! 0.000! 0.036!Na+! 0.148! 0.051! 0.023! 0.294! 0.172! 0.055! 0.023! 0.294! 0.160! 0.049! 0.041! 0.216! 0.119! 0.043! 0.032! 0.186!K+! 0.002! 0.003! 0.000! 0.021! 0.004! 0.004! 0.000! 0.021! 0.002! 0.001! 0.001! 0.004! 0.001! 0.001! 0.000! 0.004!Cs+! 0.004! 0.002! 0.000! 0.007! 0.003! 0.002! 0.000! 0.007! 0.004! 0.002! 0.001! 0.006! 0.004! 0.002! 0.000! 0.007!LA!ICP!MS! ! ! ! ! ! ! ! ! Un!zoned! ! ! ! ! !n! ! ! ! ! 5! 5! 5! 5! 14! 14! 14! 14! 6! 6! 6! 6!Li#(ppm)! ! ! ! ! 1039! 192! 791! 1319! 945! 110! 751! 1135! 324! 36! 274! 379!V! ! ! ! ! 1798! 199! 1490! 2020! 1356! 121! 1084! 1575! 2262! 199! 2012! 2489!Cs! ! ! ! ! 698! 48! 634! 763! 705! 41! 634! 778! 1397! 118! 1230! 1538!Note:&&The&following&standards&were&used:&&albite&(SiKα,"AlKα,!NaKα),#Sc#metal#(ScKα),#V#metal#(VKα),#MgCr2O4!(CrKα),#diopside#(MgKα),#fayalite#(FeKα),#orthoclase*(KKα),#and#pollucite#(CsMα).##Mn,#Ti#sought#but#not#found.##Compositions#were#recalculated#on#the#basis#of#3#Be#and#18#O#apfu.!*Determined(by(stoichiometry.!**Calculated*using*H2O"="(0.84958"×"Na2O)#+#0.8373#(Giuliani#et#al.!1997b).! 56 Table!3.!Selected&Compositions&of&Tourmaline&from&Lened&Quartz&Veins!! TURQTZ!2!3!TURQTZ!2!1!2!TURQTZ!2!2!4!TURQTZ!2!4!1!TURQTZ!2!4!2!TURQTZ!2!4!3!TURQTZ!2!5!1!TURQTZ!2!5!2!TURQTZ!2!5!3!TURQTZ!2!6!1!TURQTZ!2!6!2!TURQTZ!2!6!3!Average!(n=20)!SiO2!(wt%)!36.27! 35.29! 35.68! 36.24! 36.38! 36.84! 35.78! 35.85! 36.66! 35.68! 36.27! 35.95! 36.08!TiO2! 0.11! 0.03! 0.19! 0.16! 0.16! 0.03! 0.05! 0.04! 0.03! 0.61! 0.67! 0.76! 0.20!B2O3! 10.64! 10.54! 10.53! 10.61! 10.70! 10.71! 10.61! 10.57! 10.62! 10.52! 10.73! 10.59! 10.60!Al2O3! 33.37! 33.53! 33.51! 31.69! 34.53! 34.30! 32.72! 32.49! 32.42! 31.12! 31.90! 31.60! 32.78!V2O3! 0.60! 0.29! 0.09! 0.21! 0.50! 0.49! 0.83! 0.89! 0.83! 0.84! 0.61! 0.42! 0.47!Cr2O3! 0.01! 0.04! 0.05! 0.06! 0.02! 0.02! 0.04! 0.00! 0.04! 0.06! 0.00! 0.02! 0.03!Fe2O3!(min)!0.00! 0.00! 0.00! 1.50! 0.00! 0.00! 0.97! 0.60! 0.00! 0.00! 0.07! 0.00! 0.31!FeO$(max)!5.12! 4.08! 4.51! 4.17! 3.72! 3.38! 2.99! 3.38! 3.69! 3.32! 3.42! 3.67! 4.04!MnO! 0.02! 0.02! 0.01! 0.04! 0.00! 0.00! 0.00! 0.00! 0.06! 0.01! 0.07! 0.01! 0.02!ZnO! 0.08! 0.02! 0.00! 0.02! 0.03! 0.00! 0.09! 0.03! 0.00! 0.08! 0.01! 0.00! 0.03!MgO! 7.57! 8.32! 7.81! 8.74! 7.78! 7.97! 8.83! 8.72! 8.69! 9.68! 9.89! 9.52! 8.42!CaO! 0.02! 0.24! 0.13! 0.12! 0.14! 0.08! 0.03! 0.03! 0.03! 0.43! 0.37! 0.34! 0.16!Na2O! 2.00! 2.28! 2.79! 2.25! 2.75! 2.72! 2.17! 2.17! 2.31! 2.45! 2.47! 2.62! 2.37!K2O! 0.01! 0.01! 0.02! 0.02! 0.04! 0.02! 0.03! 0.02! 0.02! 0.02! 0.01! 0.02! 0.02!F! 0.02! 0.21! 0.14! 0.04! 0.24! 0.15! 0.18! 0.05! 0.21! 0.85! 1.11! 0.91! 0.25!H2O! 3.64! 3.52! 3.29! 3.64! 3.15! 3.18! 3.57! 3.62! 3.46! 3.18! 3.18! 3.11! 3.42!!(O=F)! !0.01! !0.09! !0.06! !0.02! !0.10! !0.06! !0.08! !0.02! !0.09! !0.36! !0.47! !0.39! !0.10!Total! 99.48! 98.32! 98.68! 99.48! 100.04! 99.82! 98.82! 98.44! 99.00! 98.49! 100.29! 99.17! 99.10!! ! ! ! ! ! ! ! ! ! ! ! ! !Si4+!(apfu)!5.93! 5.82! 5.89! 5.93! 5.91! 5.98! 5.86! 5.90! 6.00! 5.89! 5.88! 5.90! 5.92!Ti4+! 0.01! 0.00! 0.02! 0.02! 0.02! 0.00! 0.01! 0.01! 0.00! 0.08! 0.08! 0.09! 0.03!B3+! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00! 3.00!Al3+! 6.43! 6.52! 6.52! 6.12! 6.61! 6.56! 6.32! 6.30! 6.25! 6.06! 6.09! 6.11! 6.34!V3+! 0.08! 0.04! 0.01! 0.03! 0.06! 0.06! 0.11! 0.12! 0.11! 0.11! 0.08! 0.06! 0.06!Cr3+! 0.00! 0.01! 0.01! 0.01! 0.00! 0.00! 0.01! 0.00! 0.00! 0.01! 0.00! 0.00! 0.00! 57 ! TURQTZ!2!3!TURQTZ!2!1!2!TURQTZ!2!2!4!TURQTZ!2!4!1!TURQTZ!2!4!2!TURQTZ!2!4!3!TURQTZ!2!5!1!TURQTZ!2!5!2!TURQTZ!2!5!3!TURQTZ!2!6!1!TURQTZ!2!6!2!TURQTZ!2!6!3!Average!(n=20)!Fe3+!(min)!0.00! 0.00! 0.00! 0.19! 0.00! 0.00! 0.12! 0.07! 0.00! 0.00! 0.01! 0.00! 0.04!Fe2+!(max)!0.70! 0.56! 0.62! 0.57! 0.50! 0.46! 0.41! 0.47! 0.50! 0.46! 0.46! 0.50! 0.55!! ! ! ! ! ! ! ! ! ! ! ! ! !Mn2+! 0.00! 0.00! 0.00! 0.01! 0.00! 0.00! 0.00! 0.00! 0.01! 0.00! 0.01! 0.00! 0.00!Zn2+! 0.01! 0.00! 0.00! 0.00! 0.00! 0.00! 0.01! 0.00! 0.00! 0.01! 0.00! 0.00! 0.00!Mg2+! 1.84! 2.05! 1.92! 2.13! 1.88! 1.93! 2.16! 2.14! 2.12! 2.38! 2.39! 2.33! 2.06!Ca2+! 0.00! 0.04! 0.02! 0.02! 0.03! 0.01! 0.01! 0.00! 0.01! 0.08! 0.06! 0.06! 0.03!Na+! 0.63! 0.73! 0.89! 0.71! 0.87! 0.85! 0.69! 0.69! 0.73! 0.79! 0.77! 0.83! 0.75!K+! 0.00! 0.00! 0.00! 0.00! 0.01! 0.00! 0.01! 0.00! 0.00! 0.00! 0.00! 0.00! 0.00!X!vac! 0.36! 0.23! 0.08! 0.26! 0.10! 0.13! 0.30! 0.30! 0.26! 0.14! 0.16! 0.10! 0.21!! ! ! ! ! ! ! ! ! ! ! ! ! !F!! 0.01! 0.11! 0.07! 0.02! 0.13! 0.08! 0.09! 0.02! 0.11! 0.44! 0.57! 0.47! 0.13!OH!! 3.96! 3.87! 3.62! 3.98! 3.41! 3.44! 3.91! 3.98! 3.78! 3.50! 3.43! 3.41! 3.74!Note:&The&following&standards&were&used:&topaz&(FKα)"#albite#(NaKα)"#kyanite#(AlKα)"#diopside#(MgKα)"#diopside#(SiKα)"#scapolite#(ClKα)"#orthoclase#(KKα)"#diopside#(CaKα)"#rutile#(TiKα)"#vanadium#element#(VKα)"#synthetic#magnesiochromite#(CrKα)"#synthetic#rhodonite#(MnKα)"#synthetic#fayalite#(FeKα)"#and#gahnite#(ZnKα).#!Compositions)were)normalized)on)the$basis$of$(T+Z+Y)$=$15$apfu,$assuming$B$=$3$apfu,$Li$=$0$apfu,$and$31$anions$(O,$OH,$F).$Cl$was$sought$but$not$detected.$A!minimum%Fe3+!content&was&calculated&such&that&the&formula(achieves(electroneutrality.(Water(content#was#calculated#based#on#(OH+F+Cl)#=#(31#anions#!!xO2!)"where"xO2!!includes)the)oxygens)from)3)B,)and)the)calculated)minimum)Fe3+.!! 58 Table!4.!Average&Compositions&of&Muscovite&Samples&from&Lened!n!="199! Average! Std.%Dev.! Min.! Max.!SiO2!(wt.% )! 48.23! 0.63! 46.77! 50.55!TiO2! 0.20! 0.12! 0.00! 0.71!Al2O3! 29.76! 1.31! 25.72! 34.81!Cr2O3! 0.04! 0.05! 0.00! 0.32!V2O5! 0.17! 0.12! 0.00! 0.77!! ! ! ! !FeO(tot.)! 1.41! 0.30! 0.59! 2.75!MnO! 0.04! 0.03! 0.00! 0.15!MgO! 3.37! 0.71! 0.83! 5.51!CaO! 0.06! 0.06! 0.00! 0.58!! ! ! ! !Na2O! 0.22! 0.05! 0.08! 0.36!K2O! 11.00! 0.21! 10.40! 11.45!F! 0.59! 0.24! 0.00! 1.57!H2O*! 4.18! 0.12! 3.72! 4.50!!(O=F,Cl)! !0.25! 0.10! !0.66! 0.00!Total! 99.23! 0.74! 97.24! 101.13!! ! ! ! !Si#(apfu)! 3.24! 0.04! 3.14! 3.39!Ti! 0.01! 0.01! 0.00! 0.04!Al! 2.36! 0.10! 2.07! 2.74!V! 0.01! 0.01! 0.00! 0.03!Cr! 0.00! 0.00! 0.00! 0.02!! ! ! ! !Fe! 0.08! 0.02! 0.03! 0.16!Mn! 0.00! 0.00! 0.00! 0.01! 59 n!="199! Average! Std.%Dev.! Min.! Max.!Mg! 0.34! 0.07! 0.08! 0.55!Ca! 0.00! 0.00! 0.00! 0.04!! ! ! ! !Na! 0.03! 0.01! 0.01! 0.05!K! 0.94! 0.02! 0.89! 0.99!F! 0.13! 0.05! 0.00! 0.33!OH! 1.87! 0.05! 1.67! 2.00!O! 10.00! 0.00! 10.00! 10.00!*Determined*by*stoichiometry*(F*+*OH)*=*2*apfu.*Calculation*is*based*on*12*anions.!Note:&Ba&was&sought&but&not&found.! 60 Table!5.!Oxygen&and&Carbon&Isotope&Compositions!Sample! Source! Mineral!!DH2O!(‰),"!!(wt.% %H2O)!!18O,#(!13C)! !18OH2O,%!(∆qtz!H2O)"700°C!!18OH2O,%!(∆qtz!H2O)"600°C!!18OH2O,%!(∆qtz!H2O)"350°C!Thermometry)Mineral(Pair!∆18Opair!(‰)!Oxygen'Equilibration'Temperature**(°C)!(2σ)!References:)mineral!mineral,)(mineral!water)!DM!05! Coarse'Granite!Quartz! ! 13.2! 12.6%(0.6)!11.5$(1.7)! 7.9$(5.3)!qtz!ann! 4.7! 412$±$15! 1,#(2)!DM!06! Weathered(Granite!Quartz! ! 13.3! 12.7%(0.6)!11.6$(1.7)! 8.0$(5.3)!qtz!ann! 4.8! 574$±$15! 1,#(2)!DM!07! Skarn!Granite(Contact!Quartz! ! 13.5! 12.9%(0.6)!11.8$(1.7)! 8.2$(5.3)!qtz!ann! 5.0! 372$±$15! 1,#(2)!L!01! Vein! Quartz! ! 15.5! !  10.2%(5.3)!qtz!ms! 4.9! 307$±$10! 1,#(1)!L!01! Vein! Quartz! ! 15.4! !  10.1$(5.3)!qtz!ms! 4.8! 315$$±$10! 1,#(1)!DM!05! Coarse'Granite!Biotite! ! 8! !   qtz!ann! 5.3! 412$±$15! 1!DM!06! Weathered(Granite!Biotite! ! 9.6! !   qtz!ann! 3.7! 574$±$15! 1!DM!07! Skarn!Granite(Contact!Biotite! ! 7.8! !   qtz!ann! 5.5! 372$±$15! 1!L!01! Vein! Muscovite! ! 11.2! !   qtz!ms! 4.3! 355!±"15! 1,#(1)!L!01! Vein! Muscovite! ! 10.1! !   qtz!ms! 5.3! 266##±#10! 1,#(1)!L!01! Vein! Calcite! ! 11.2,%(!4.8)!!   qtz!cal! 4.3! 185$$±$20! 3! 61 Sample! Source! Mineral!!DH2O!(‰),"!!(wt.% %H2O)!!18O,#(!13C)! !18OH2O,%!(∆qtz!H2O)"700°C!!18OH2O,%!(∆qtz!H2O)"600°C!!18OH2O,%!(∆qtz!H2O)"350°C!Thermometry)Mineral(Pair!∆18Opair!(‰)!Oxygen'Equilibration'Temperature**(°C)!(2σ)!References:)mineral!mineral,)(mineral!water)!L!01! Vein! Calcite! ! 10.7,&(!5.2)!!! !! !! qtz!cal! 4.7! 191##±#20! 3!Talus&1!Vein! Beryl! !62.0,&(1.92)!! ! ! ! ! ! ! !Talus&1a!Vein! Beryl! !60.2,&(1.98)!! ! ! ! ! ! ! !Talus&2!Vein! Beryl! !67.7,%(2.04)!! ! ! ! ! ! ! !Talus&3!Vein! Beryl! !87.4,&(1.84)!! ! ! ! ! ! ! !21! Vein! Beryl! !85.1,&(1.94)!! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! !Note:&Reproducibility&of&the&oxygen'isotope'measurements'is'0.1‰%(1σ)%for%quartz,"reproducibility-for-calcite-is-0.2‰%(1σ)%for%!18O"and"!13C.!Fractionation)equations)are)from:)1!(Zheng'1993b),'2!(Matsuhisa)et#al.!1979),&3!(Sharp'&'Kirschner'1994)!*Error%noted%for%equilibration%temperatures%only%accounts%for%analytical%error%(2σ).! 62 !!Table!6.!Boron$Isotope$Compositions$of$Lened$Tourmaline!(δ11B)!Spot*! δ11B"(‰)!1! !6.6#!2! !5.6$!3! !5.5#!4! !3.1$!5! !5.0$!6! !5.8$!7! !4.1$!8! !4.5$!9! !3.7$!10! !4.9$!*Series'from'sample'LO1!Turqtz!X1!Note:&Spot!to!spot%reproducibility%on%the"tourmaline"standard"="±0.3‰"(2σ)!! ! 63 Table!7.!!Geochemistry+of+Lened+Granites,+Skarns,+and+Black!Shales!!! GRANITE! ! ! ! BLACK! SHALE! ! ! ! ! SKARN! !! !! !! !!! ! ! ! ! ! ! 4"m"E*! 2"m"E*! 1"m"E*! 0"m"skarn?*!0"m"skarn*!1"m"W*!2"m"W*!4"m"W*!8"m"W*!Oxide/'element!DM!02!05!DM!02!09!DM!02!12a!DM!02!12b!HF#!!2! HF#!!7! HF#!!11! HF#!!12! HF#!!13! HF#!!10! HF#!!14! HF#!!15!HF#!!16!HF#!!17!HF#!!18!P2O5!(wt.%)! 0.12! 0.1! 0.12! 0.14! 0.06! 0.18! 0.23! 0.49! 0.21! 0.25! 0.51! 0.06! 0.05! 0.05! 0.08!SiO2! 72.96! 73.44! 69.05! 70.43! 85.33! 81.39! 75.9! 68.15! 83.7! 48.97! 67.67! 37.86! 41.88!34.02! 43.02!TiO2! 0.2! 0.18! 0.36! 0.33! 0.48! 0.34! 0.43! 0.54! 0.32! 0.26! 0.43! 0.32! 0.35! 0.28! 0.3!Al2O3! 13.8! 13.64! 14.93! 14.48! 7.39! 5.59! 6.93! 7.9! 5.03! 4.04! 8.12! 6.75! 7.62! 5.9! 8.11!Cr2O3! 0.01! b.d.l.! 0.01! 0.02! 0.03! 0.05! 0.05! 0.07! 0.05! 0.03! 0.1! 0.02! 0.02! 0.02! 0.03!Fe2O3! 0.32! 0.27! 0.37! 0.38! 0.78! 1.04! 0.59! 1.25! 0.82! 0.56! 0.60! 0.64! 0.66! 0.46! 1.19!FeO! 1.35! 1.09! 2.57! 2.51! 0.39! 0.71! 0.90! 0.71! 0.64! 2.83! 2.38! 3.34! 3.8! 2.32! 4.37!MgO! 0.52! 0.56! 0.65! 0.72! 0.46! 0.35! 0.45! 0.56! 0.31! 0.63! 1.06! 4.63! 5.31! 4.88! 5.55!CaO! 1.05! 0.98! 2.22! 2.09! 0.08! 0.64! 0.74! 3.81! 0.84! 41.19! 14! 35.54! 31.65!36.96! 29.05!MnO! 0.05! 0.04! 0.05! 0.06! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.02! 0.26! 0.32! 0.35! 0.2! 0.54!SrO! 0.03! 0.03! 0.06! 0.03! b.d.l.! b.d.l.! 0.01! 0.01! 0.02! 0.01! 0.02! 0.02! 0.02! 0.02! 0.02!BaO! 0.03! 0.02! 0.11! 0.09! 0.43! 0.12! 0.1! 0.13! 0.1! b.d.l.! 0.01! 0.01! 0.01! 0.01! 0.01!Na2O! 2.94! 2.97! 2.69! 2.68! 0.09! 0.12! 0.11! 0.14! 0.06! 0.02! 0.09! 0.12! 0.1! 0.04! 0.05!K2O! 4.74! 5.1! 5.01! 4.83! 2.36! 1.81! 2.35! 2.56! 1.69! 0.04! 0.17! 0.04! 0.02! 0.01! 0.02!LOI! 0.95! 0.88! 0.63! 0.81! 2.13! 7.49! 10.95! 12.95! 5.91! 0.56! 3.04! 9.67! 6.21! 13.15! 6.56!Total! 99.08! 99.31! 98.83! 99.46! 100.01! 99.83! 99.74! 99.27! 99.70! 99.41! 98.46! 98.34! 98.05!98.32! 98.89!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !H2O+!(wt.% )! 0.65! 0.58! 0.48! 0.63! 0.27! 0.88! 0.9! 1.05! 0.74! 0.15! 0.36! 0.14! 0.18! 0.2! 0.19!H2O!! 0.13! 0.08! 0.08! 0.09! 0.05! 0.07! 0.04! 0.06! 0.05! 0.02! 0.03! 0.03! 0.04! 0.05! 0.05!CO2! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.3! 0.2! 2.3! 0.4! 0.6! 2.5! 9.2! 5.7! 12.3! 5.9! 64 !! GRANITE! ! ! ! BLACK! SHALE! ! ! ! ! SKARN! !! !! !! !!! ! ! ! ! ! ! 4"m"E*! 2"m"E*! 1"m"E*! 0"m"skarn?*!0"m"skarn*!1"m"W*!2"m"W*!4"m"W*!8"m"W*!Oxide/'element!DM!02!05!DM!02!09!DM!02!12a!DM!02!12b!HF#!!2! HF#!!7! HF#!!11! HF#!!12! HF#!!13! HF#!!10! HF#!!14! HF#!!15!HF#!!16!HF#!!17!HF#!!18!C! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.09! 0.06! 0.64! 0.11! 0.16! 0.69! 2.5! 1.56! 3.36! 1.6!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !Li#(ppm)! 109! 52.3! 140.5! 174.69! 35.47! 35.54! 49.26! 54.14! 37.34! 4.31! 16.18! 22.84! 27.96!22.38! 16.91!Be! 6.43! 5.15! 5.25! 6.13! 1.98! 3.11! 4.09! 4.42! 3.59! 2! 2.72! 2.46! 3.07! 1.29! 2.5!B! 20! 20! b.d.l.! 20! 120! 240! 240! 450! 150! 20! 70! 190! 150! 120! 130!F! 320! 290! 580! 470! 370! 420! 720! 1000! 400! 350! 780! 1230! 1470! 790! 320!Sc! 5.5! 5.3! 8.4! 8.54! 10.59! 6.34! 10.16! 11.04! 7.4! 7.83! 16.41! 7.24! 8.02! 7.18! 8.6!V! 17! 14! 31! 34! 182! 2110! 2070! 3170! 2140! 1508! 4670! 68! 65! 42! 73!Cr! 150! 50! 140! 160! 160! 200! 200! 280! 240! 120! 410! 110! 110! 80! 120!Co! 2.4! 2! 4.2! 5.9! 2.1! 4.6! 2.4! 6.3! 4.4! 9.1! 5.5! 8.6! 10.8! 7.8! 10!Ni! b.d.l.! b.d.l.! b.d.l.! 10! 9! 142! 72! 217! 152! 141! 184! 26! 25! 19! 37!Cu! 16! 114! 33! 82! 22! 43! 33! 45! 39! 10! 17! 9! 6! 7! 5!Zn! 42! 30! 54! 52! 45! 308! 226! 654! 285! 206! 194! 360! 427! 307! 440!Ga! 17! 15! 18! 17! 12! 9! 11! 13! 9! 8! 21! 13! 14! 11! 18!Rb! 250! 231! 216! 219! 99.3! 68! 75! 89.9! 55.7! 0.5! 8.1! b.d.l.! b.d.l.! b.d.l.! 0.6!Sr! 114! 94.2! 318! 307.1! 22.8! 29.3! 25.7! 59.4! 31.8! 97.9! 134.6! 122.2! 81.2! 207! 93.6!Y! 17.7! 26.6! 18.4! 18.2! 18.2! 23.7! 30.8! 45.1! 22.2! 44.1! 71.3! 8.3! 7.6! 7.9! 7.5!Zr! 71.2! 54.9! 151! 133.1! 171.2! 59.6! 90.8! 83.6! 54.5! 48.6! 103.6! 45.8! 51.8! 47.7! 68.9!Nb! 16! 16! 18! 17! 7! 5! 5! 10! 5! 5! 13! 6! 4! 5! 7!Mo! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 3! 27! 16! 20! 32! 34! 281! 3! b.d.l.! b.d.l.! 25! 65 !! GRANITE! ! ! ! BLACK! SHALE! ! ! ! ! SKARN! !! !! !! !!! ! ! ! ! ! ! 4"m"E*! 2"m"E*! 1"m"E*! 0"m"skarn?*!0"m"skarn*!1"m"W*!2"m"W*!4"m"W*!8"m"W*!Oxide/'element!DM!02!05!DM!02!09!DM!02!12a!DM!02!12b!HF#!!2! HF#!!7! HF#!!11! HF#!!12! HF#!!13! HF#!!10! HF#!!14! HF#!!15!HF#!!16!HF#!!17!HF#!!18!Ag! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.!Sn! 3! 2! 5! 6! 2! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 18! 39! 120! 97! 81! 106!Cs! 8.5! 6.4! 10.7! 10.7! 5! 12.1! 11.1! 14.1! 11.5! 0.1! 1.6! 0.1! 0.1! 0.2! 0.3!Ba! 332! 214! 921! 917.3! 4030! 1029.5! 824! 1244! 880! 47.5! 133! 51.7! 12! 26.8! 25!La! 22.8! 22.2! 57.6! 55.9! 24.2! 16! 13.9! 24.4! 15.4! 23.4! 17.6! 19.2! 22.3! 18.6! 15!Ce! 45.3! 45.3! 118! 106.8! 47.9! 24.6! 22.4! 36.9! 24.4! 31.5! 25.1! 33.9! 41.2! 34.2! 29.1!Pr! 4.8! 4.9! 12.2! 12.1! 5.6! 3.7! 3.5! 6.1! 3.6! 4.8! 4.6! 3.7! 4.5! 3.9! 3.3!Nd! 17.3! 18.5! 44.8! 42.7! 21.1! 15.9! 15.9! 26.9! 15.3! 20.5! 21.9! 13.8! 15.6! 14.7! 12.5!Sm! 3.5! 4.1! 7.5! 7.5! 4! 3.1! 2.9! 5.5! 2.5! 4! 5.7! 2.1! 2.3! 2.4! 2.1!Eu! 0.5! 0.5! 1.4! 1.4! 0.8! 0.7! 0.7! 1.3! 0.6! 1.1! 1.1! 0.7! 0.6! 0.5! 0.4!Gd! 3.2! 3.7! 6.1! 6.1! 3.6! 3.3! 3.8! 5.6! 3.2! 4.7! 7.2! 2! 2.3! 2.2! 1.8!Tb! 0.5! 0.7! 0.8! 0.7! 0.5! 0.5! 0.6! 0.9! 5! 0.7! 1.2! 0.3! 0.3! 0.3! 0.3!Dy! 2.8! 3.9! 3.4! 3.4! 3.2! 2.8! 3.5! 4.9! 2.6! 4.5! 7.9! 1.4! 1.4! 1.5! 1.3!Ho! 0.5! 0.8! 0.6! 0.6! 0.6! 0.7! 0.8! 1.1! 0.6! 1! 1.8! 0.3! 0.3! 0.3! 0.3!Er! 1.7! 2.5! 1.7! 1.8! 1.9! 1.8! 2.3! 3.1! 1.7! 3! 5.4! 0.8! 0.8! 0.9! 0.8!Tm! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! 0.7! b.d.l.! b.d.l.! b.d.l.! b.d.l.!Yb! 1.7! 2.6! 1.6! 1.6! 1.9! 1.4! 1.9! 2.3! 1.6! 2.8! 5.2! 0.7! 0.7! 0.7! 0.7!Lu! 0.2! 0.4! 0.2! 0.2! 0.3! 0.2! 0.3! 0.4! 0.2! 0.5! 0.8! 0.1! 0.1! 0.1! 0.1!Hf! 3! 2! 5! 5! 4! 2! 2! 2! 1! 1! 3! 1! 1! 1! 2!Ta! 2.9! 3.6! 2.1! 2! 0.7! 0.6! 0.7! 0.9! 0.5! b.d.l.! 0.7! b.d.l.! b.d.l.! b.d.l.! 0.5!W! 3! 3! 3! 2! 3! 4! 5! 5! 6! 98! 808! 111! 92! 81! 329! 66 !! GRANITE! ! ! ! BLACK! SHALE! ! ! ! ! SKARN! !! !! !! !!! ! ! ! ! ! ! 4"m"E*! 2"m"E*! 1"m"E*! 0"m"skarn?*!0"m"skarn*!1"m"W*!2"m"W*!4"m"W*!8"m"W*!Oxide/'element!DM!02!05!DM!02!09!DM!02!12a!DM!02!12b!HF#!!2! HF#!!7! HF#!!11! HF#!!12! HF#!!13! HF#!!10! HF#!!14! HF#!!15!HF#!!16!HF#!!17!HF#!!18!Au! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.!TI! 1! 1! 1! 1! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.!Pb! 42! 46! 58! 30! 5! 6! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.! b.d.l.!Th! 12! 16! 27! 26! 8! 4! 4! 5! 3! 3! 3! 5! 6! 5! 5!U! 10.7! 6.2! 5.5! 6.2! 2.4! 5.9! 7.6! 5.8! 6.5! 25.9! 17.8! 1.1! 1.1! 0.9! 1.1!Eu/Eu*! 0.5! 0.4! 0.6! 0.6! 0.6! 0.7! 0.6! 0.7! 0.6! 0.8! 0.5! 1.0! 0.8! 0.7! 0.6!(La/Lu)CN! 11.8! 5.8! 29.0! 29.9! 8.4! 8.3! 4.8! 6.3! 8.0! 4.9! 2.3! 19.9! 23.1! 19.3! 15.6!Note:&&Most&major&elements&were&analyzed&using&XRF,&and&most&trace&elements&by&ICP!MS#or#ICP!ES.$$Li,$Be,$Cr,$Mo$were$determined$by$AAS6$$B$and$Cl$by$INAA6$$FeO$by$titration$(b.d.l.&=&below&detection(limits).(LOI(=(Loss(on(ignition.!Eu#anomaly#defined#as#Eu/Eu*=Eu#/#sqrt(SmCN*GdCN)"#Chondrite#values#from#Mcdonough#&#Sun#(1995)!*This&series&of&samples&is&a&transect&across&the&contact&of&black&shale&and&skarn&with&0&m&centered&on&the&contact.!!!!!!! ! 67 Table&8.!Geochemistry,of,Secondary,Rock,Types,at,Lened!!! EMERALD'VEIN!Shale&Vein1! Conglomerate2! Calc!arenite3! Limestone4! Skarn&Alteration5!Fault&Gouge6!Oxide/Element! HF!22! HF#!!8! HF#!!1! HF#!!3! HF#!!6! HF#!!9! HF#!!19!P2O5!(wt.%)! 0.01! 0.03! 0.05! 0.11! 0.06! 0.07! 0.37!SiO2! 79.94! 14.99! 89.64! 48.25! 13.91! 23.6! 68.38!TiO2! 0.05! 0.04! 0.27! 0.49! 0.16! 0.31! 0.1!Al2O3! 0.82! 0.52! 4.39! 7.95! 3.89! 7.72! 2.39!Cr2O3! 0.03! 0.01! 0.04! 0.02! <0.01! 0.01! 0.03!Fe2O3! 0.04! 0.25! 1.30! 0.55! 0.05! 0.37! 5.77!FeO! 0.26! 0.13! 0.51! 2.57! 1.16! 2.12! 0.64!MgO! <0.01! 0.06! 0.29! 10.61! 2.51! 5.25! <0.01!CaO! 9.95! 45.35! 0.09! 21.31! 44.41! 34.14! 0.17!MnO! 0.15! 0.04! <0.01! 0.07! 0.08! 0.03! <0.01!SrO! 0.02! 0.1! <0.01! 0.03! 0.11! 0.04! 0.04!BaO! 0.01! <0.01! 0.17! 0.17! 0.04! 0.05! 8.96!Na2O! 0.05! <0.01! 0.05! 0.21! <0.01! 0.05! 0.13!K2O! 0.07! 0.18! 1.38! 0.91! 1.48! 2.86! 0.71!LOI! 8.13! 36.6! 1.54! 5.06! 30.3! 22.9! 5.2!Total! 99.52! 98.26! 99.72! 98.20! 98.16! 99.52! 92.89!! ! ! ! ! ! ! !H2O+!(wt.% )! 0.09! 0.17! 0.59! 0.55! 0.14! 0.6! 1.66!H2O!! 0.03! 0.01! 0.03! 0.09! 0.03! 0.05! 0.29!CO2! 7.5! 35.1! <0.2! 4.3! 32.7! 21.8! <0.2!C! 2.04! 9.57! <0.05! 1.19! 8.91! 5.95! <0.05!! ! ! ! ! ! ! !Li#(ppm)! 15.2! 1.89! 19.16! 24.31! 14.39! 21.32! 14.25!Be! 746 0.19 1.16 1.67 0.45 0.8 1.24 B! <20! 40! 30! 20! 60! 20! 70!F! 20! 80! 210! 330! 700! 740! 420!Sc! 3.9! 0.66! 5.27! 8.52! 3.41! 6.69! 2.6! 68 !! EMERALD'VEIN!Shale&Vein1! Conglomerate2! Calc!arenite3! Limestone4! Skarn&Alteration5!Fault&Gouge6!Oxide/Element! HF!22! HF#!!8! HF#!!1! HF#!!3! HF#!!6! HF#!!9! HF#!!19!V! 47! 115! 67! 227! 24! 49! 651!Cr! 180! 30! 230! 90! 20! 50! 180!Co! 0.8! 2.6! 2.8! 6.5! 4.7! 11.2! 1.8!Ni! <5! 54! 13! 77! 12! 37! 57!Cu! 10! 21! 24! 67! 11! 17! 77!Zn! 13! 107! 26! 317! 12! 17! 773!Ga! 1! 1! 7! 13! 5! 11! 9!Rb! 5.3! 4.5! 62.6! 49! 38.8! 77.9! 36.7!Sr! 48.5! 778! 26.1! 337.4! 697! 379! 155.5!Sr!Y!48.5!6.2!778!14.3!26.1!9.3!337.4!21.7!697!5.5!379!9.1!155.5!38.5!Sr!Y!Zr!48.5!6.2!2.4!778!14.3!5.6!26.1!9.3!89.3!337.4!21.7!169.5!697!5.5!39.1!379!9.1!41.6!155.5!38.5!32.2!Nb! <1! 1! 4! ! 3! 5! !Mo! <2! 6! 3! 21! <2.00! <2.00! 59!Ag! <1! <1! <1! <1! <1! <1! <1!Sn! 108! <1.00! <1.00! 19! <1.00! <1.00! <1.00!Cs! 32.7! 0.8! 7.5! 5.1! 1.9! 4! 5.7!Ba! 23.8! 59! 1543.7! 1731! 513! 673! >10000!La! 3.1! 6.5! 17.1! 25.7! 12.4! 49.5! 7.3!Ce! 5! 11.4! 35.9! 48! 22.5! 113.4! 8.8!Pr! 0.6! 1.9! 4.1! 6.2! 2.3! 13.8! 1.7!Nd! 2.3! 9.8! 15.6! 23.5! 8.9! 53! 10.2!Sm! 0.5! 1.8! 2.9! 4.4! 1.3! 8.1! 2.9!Eu! 0.3! 1.2! 0.5! 0.8! 0.3! 2! 1.8!Gd! 0.6! 1.9! 2.5! 4.3! 1.4! 6.5! 4!Tb! 0.1! 0.3! 0.3! 0.6! 0.2! 0.7! 0.7!Dy! 0.7! 1.5! 1.6! 3.3! 0.9! 2.3! 4.1!Ho! 0.2! 0.3! 0.3! 0.7! 0.2! 0.4! 0.9! 69 !! EMERALD'VEIN!Shale&Vein1! Conglomerate2! Calc!arenite3! Limestone4! Skarn&Alteration5!Fault&Gouge6!Oxide/Element! HF!22! HF#!!8! HF#!!1! HF#!!3! HF#!!6! HF#!!9! HF#!!19!Er! 0.4! 0.8! 1! 2.1! 0.6! 1.1! 2.7!Tm! <0.5! <0.5! <0.5! <0.5! <0.5! <0.5! <0.5!Yb! 0.5! 0.5! 1! 2! 0.5! 0.8! 2.3!Lu! 0.1! 0.1! 0.1! 0.3! 0.1! 0.1! 0.4!Hf! <1! <1! 2! 5! 1! 1! 1!Ta! <0.5! <0.5! 0.5! 0.7! <0.5! <0.5! <0.5!W! 2! 2! 2! 3! 1! <1.00! 13!Au! <0.005! ! ! ! ! ! !TI! <1! <1! <1! <1! <1! <1! <1!Pb! 5! <5! 29 <5 5 5 <5 Th! <1! 1! 6! 8! 2! 23! 1!U! <0.5! 0.9! 1.6! 10.8! 1! 1.2! 9.7!Eu/Euª! 1.7! 2.0! 0.6! 0.6! 0.7! 0.8! 1.6!(La/Lu)CN! 3.2! 6.7! 17.7! 8.9! 12.9! 51.4! 1.9!Note:&Most&major&elements&were&analyzed&using&XRF,&and&most&trace&elements&by&ICP!MS#or#ICP!ES.$$Li,$Be,$Cr,$Mo$were$determined$by$AAS6$$B$and$Cl!by#INAA'##FeO#by#titration.!1Emerald!barren&calcite!(minor'qtz)'vein'in'black'shale'adjacent'to'skarn7'2Calc!arenite'to'quartz'pebble!lithic&fragment&conglomerate&from&Lened&Ridge&above&emerald&showing6&3Calc!arenite'interbedded'with'pyritic'black'shale2'4Rhythmically*bedded*limestone*from*the*weakly*skarn!altered'zone'of'showing'~20'm'SW'of'veins8'5Cross!cutting'fracture'and'dark'alteration)feature)in)skarn.)and)6Fault&breccia&of&black&shale&and&arenite,&with&a&competent&carbonate&cement&that&forms&a&prominent)resistant)spire)at)the)showing.!Eu#anomaly#defined#as#Eu/Eu*#=#Eu#/#(SmN*GdN)1/2!!Chondrite*values*from*Mcdonough*&*Sun*(1995)! 70 !!Table&9."40Ar/39Ar!Age$Data!(DM!02!05#Lened%Granite%Biotite)!Laser! Isotope'ratios!sample/mineral! !! !! !! !! !! !! !! !! !! !!Power&(%)! 36Ar/40Ar! 1σ! 39Ar/40Ar! 1σ! r! Ca/K! %40Atm! %39Ar! 40Ar*/39K! 1σ! Age$(Ma)! ! 2σ!0.50! 0.001686! 0.000646! 0.034991! 0.001580! 0.004! 0.052! 49.76! 8.57! 14.34! 5.52! 94.2! ±! 35.3!<"0.75! 0.000483! 0.000235! 0.055759! 0.000855! 0.001! 0.015! 14.24! 9.51! 15.38! 1.27! 100.8! ±! 8.1!<"1.25! 0.000000! 0.000124! 0.063293! 0.000666! !0.001! 0.000! !0.01! 16.20! 15.80! 0.60! 103.5! ±! 3.9!<"2.00! 0.000060! 0.000138! 0.064157! 0.000611! !0.001! 0.001! 1.76! 16.22! 15.31! 0.65! 100.4! ±! 4.2!<"3.00! 0.000818! 0.000103! 0.050306! 0.000460! 0.003! 0.001! 24.13! 17.47! 15.08! 0.62! 98.9! ±! 4.0!<"4.00! 0.000648! 0.000154! 0.055768! 0.000597! 0.002! 0.000! 19.11! 13.88! 14.50! 0.83! 95.2! ±! 5.3!<"5.00! 0.000347! 0.000229! 0.057470! 0.000848! 0.000! 0.002! 10.24! 8.48! 15.62! 1.20! 102.3! ±! 7.7!<"7.00! 0.000225! 0.000515! 0.062197! 0.001207! !0.001! 0.003! 6.62! 6.08! 15.01! 2.47! 98.5! ±! 15.8!<"8.00! 0.000163! 0.000264! 0.063761! 0.000862! !0.001! 0.038! 4.79! 10.25! 14.93! 1.24! 98.0! ±! 7.9!!! !! !! !! !          J"="0.003737"±"0.000024! !! Volume'39K"="1.12"x"1E!10#cm3#NTP! ! Integrated)Age:)99.63)±)2.30)Ma! !    Initial'40/36:'258.22'±'44.40'(MSWD'='0.84,'isochron'between'0.47'and'2.07)! !        Correlation*Age:*! 101.59&±&2.35&Ma&(100.0%&of&39Ar,$steps$marked$by$>)! MSWD%! 1.091! !     Plateau'Age:'! 99.73%±%2.24%Ma%(%98.1%%of%39Ar,$steps$marked$by$<)! Mod.%err.%! 1.99! !! !! !! !! !!! 71 Table&10.!40Ar/39Ar!Age$Data!(DM!02!07#Lened$Granite$Biotite)!Laser! Isotope'ratios! sample/mineral! !! !! !! !! !! !! !! !! !! !!Power&(%)! 36Ar/40Ar! 1σ! 39Ar/40Ar! 1σ! r! Ca/K! %40Atm! %39Ar! 40Ar*/39K! 1σ! Age$(Ma)! ! 2σ!0.50! 0.001950! 0.000814! 0.031025! 0.002020! 0.003! 0.041! 57.57! 0.85! 13.66! 7.84! 89.8! ±! 50.3!<"0.75! 0.000483! 0.000235! 0.055759! 0.000855! 0.001! 0.015! 14.24! 9.51! 15.38! 1.27! 100.8! ±! 8.1!<"1.25! 0.000000! 0.000124! 0.063293! 0.000666! !0.001! 0.000! !0.01! 16.20! 15.80! 0.60! 103.5! ±! 3.9!<"2.00! 0.000060! 0.000138! 0.064157! 0.000611! !0.001! 0.001! 1.76! 16.22! 15.31! 0.65! 100.4! ±! 4.2!<"3.00! 0.000818! 0.000103! 0.050306! 0.000460! 0.003! 0.001! 24.13! 17.47! 15.08! 0.62! 98.9! ±! 4.0!<"4.00! 0.000648! 0.000154! 0.055768! 0.000597! 0.002! 0.000! 19.11! 13.88! 14.50! 0.83! 95.2! ±! 5.3!<"5.00! 0.000347! 0.000229! 0.057470! 0.000848! 0.000! 0.002! 10.24! 8.48! 15.62! 1.20! 102.3! ±! 7.7!<"7.00! 0.000225! 0.000515! 0.062197! 0.001207! !0.001! 0.003! 6.62! 6.08! 15.01! 2.47! 98.5! ±! 15.8!<"8.00! 0.000163! 0.000264! 0.063761! 0.000862! !0.001! 0.038! 4.79! 10.25! 14.93! 1.24! 98.0! ±! 7.9!!! !! !! !! !          J"="0.003737"±"0.000024! !! Volume'39K"="2.00"x"1E!10#cm3#NTP! ! Integrated)Age:)97.09)±)1.30)Ma! !    Initial'40/36:'300.54'±'36.69'(MSWD'='0.30,'isochron'between'0.42!and$2.15)! !        Correlation*Age:*! 96.85&±&1.14&Ma&(100.0%&of&39Ar,$steps$marked$by$>)! MSWD%! 0.268! !     Plateau'Age:'! 97.16&±&1.24&Ma&(&99.2%&of&39Ar,$steps$marked$by$<)! Mod.%err.%! 1.79! !! !! !! !! !!!! 72 Table&11.!40Ar/39Ar!Age$Data!(HF!22"Vein%Muscovite)!Laser! Isotope'ratios! sample/mineral! !! !! !! !! !! !! !! !! !! !!Power&(%)! 36Ar/40Ar! 1σ! 39Ar/40Ar! 1σ! r! Ca/K! %40Atm! %39Ar! 40Ar*/39K! 1σ! Age! ! 2σ!1.50! 0.002782! 0.000712! 0.006948! 0.000984! 0.036! 0.000! 82.18! 0.10! 25.62! 31.06! 165.0! ±! 191.1!2.00! 0.000100! 0.001039! 0.052827! 0.002273! !0.008! 0.000! 2.97! 0.39! 18.37! 5.90! 119.8! ±! 37.3!<"2.50! 0.000445! 0.000663! 0.054869! 0.001180! !0.004! 0.044! 13.13! 0.79! 15.83! 3.59! 103.7! ±! 22.9!<"3.00! 0.000559! 0.000308! 0.052918! 0.000798! !0.002! 0.036! 16.48! 1.53! 15.78! 1.74! 103.4! ±! 11.1!<"3.50! 0.000332! 0.000419! 0.059168! 0.001172! !0.006! 0.000! 9.78! 1.05! 15.24! 2.12! 100.0! ±! 13.5!<"4.00! 0.000033! 0.000071! 0.064964! 0.000433! !0.004! 0.000! 0.98! 6.67! 15.24! 0.34! 99.9! ±! 2.2!<"4.50! 0.000126! 0.000023! 0.064214! 0.000303! 0.004! 0.007! 3.71! 25.31! 14.99! 0.13! 98.4! ±! 0.8!<"5.00! 0.000320! 0.000026! 0.061322! 0.000312! 0.009! 0.003! 9.44! 20.14! 14.76! 0.15! 96.9! ±! 1.0!<"5.50! 0.000063! 0.000158! 0.065498! 0.000602! !0.004! 0.000! 1.84! 3.86! 14.99! 0.73! 98.3! ±! 4.6!<"6.00! 0.000038! 0.000180! 0.064581! 0.000689! !0.003! 0.000! 1.11! 3.72! 15.31! 0.84! 100.4! ±! 5.4!<"6.50! 0.000267! 0.000190! 0.062182! 0.000639! !0.004! 0.013! 7.86! 2.79! 14.82! 0.92! 97.2! ±! 5.9!<"7.00! 0.000137! 0.000064! 0.064253! 0.000383! !0.001! 0.001! 4.03! 10.14! 14.93! 0.31! 98.0! ±! 2.0!<"8.00! 0.000003! 0.000017! 0.066616! 0.000289! !0.002! 0.000! 0.08! 23.51! 15.00! 0.10! 98.4! ±! 0.6!!! !! !! !! !          J"="0.003737"±"0.000024! !! Volume'39K"="5.59"x"1E!10#cm3#NTP! ! Integrated)Age:)98.47)±)0.89)Ma)! !    Initial'40/36:'256.77'±'29.74'(MSWD'='1.24,'isochron'between'0.57'and'1.85)! !        Correlation*Age:*! 98.59%±%0.50%Ma%(100.0%%of%39Ar,$steps$marked$by$>)$! MSWD%! 1.253! !     Plateau'Age:'! 98.32&±&0.86&Ma&(&99.5%&of&39Ar,$steps$marked$by$<)$! Mod.%err.%! 0.47! !! !! !! !! !!! 73 Table&12.!40Ar/39Ar!Age#Data#(HF!22B#Vein#Muscovite)!Laser! Isotope'ratios! sample/mineral! ! ! ! ! ! ! ! ! ! !Power&(%)! 36Ar/40Ar! 1σ! 39Ar/40Ar! 1σ! r! Ca/K! %40Atm! %39Ar! 40Ar*/39K! 1σ! Age$(Ma)! ! 2σ!3.00! 0.001732! 0.000057! 0.006948! 0.000984! 0.086! 0.087! 51.13! 8.57! 15.17! 0.55! 99.5! ±! 3.5!3.50! 0.000742! 0.000062! 0.050309! 0.000302! 0.004! 0.003! 21.90! 6.17! 15.52! 0.38! 101.7! ±! 2.4!<"4.00>! 0.000150! 0.000029! 0.063113! 0.000289! 0.001! 0.002! 4.43! 17.40! 15.14! 0.15! 99.3! ±! 1.0!<"4.50>! 0.000202! 0.000059! 0.061428! 0.000367! !0.001! 0.000! 5.95! 7.14! 15.31! 0.30! 100.4! ±! 1.9!<"5.00>! 0.000099! 0.000035! 0.064525! 0.000299! !0.001! 0.001! 2.92! 12.80! 15.04! 0.18! 98.7! ±! 1.1!<"5.50>! 0.000028! 0.000072! 0.065839! 0.000424! !0.002! 0.001! 0.82! 7.79! 15.06! 0.34! 98.8! ±! 2.2!<"6.00>! 0.000052! 0.000051! 0.065286! 0.000351! !0.003! 0.000! 1.54! 9.03! 15.08! 0.25! 98.9! ±! 1.6!<"6.50>! 0.000000! 0.000316! 0.064575! 0.001024! !0.002! 0.000! 0.00! 1.32! 15.49! 1.47! 101.5! ±! 9.3!<"7.00>! 0.000105! 0.000055! 0.065177! 0.000409! 0.000! 0.003! 3.10! 6.36! 14.87! 0.27! 97.5! ±! 1.7!<"8.00>! 0.000025! 0.000019! 0.065871! 0.000262! 0.000! 0.002! 0.75! 23.43! 15.07! 0.10! 98.8! ±! 0.7!!! !! !! !! !          J"="0.003737"±"0.000026! !! Volume'39K"="6.52"x"1E!10#cm3#NTP! ! Integrated)Age:)99.19)±)0.86)Ma)! !    Initial'40/36:'337.35'±'83.71'(MSWD'='0.63,'isochron'between'0.42'and'2.15)! !        Correlation*Age:*! 98.59%±%0.79%Ma%(%85.3%%of%39Ar,$steps$marked$by$>)! MSWD%! 0.869! !     Plateau'Age:'! 98.98$±$0.83$Ma$($85.3%$of$39Ar,$steps$marked$by$<)! Mod.%err.%! 0.46! !! !! !! !! !!!! ! 74 Figures        Figure 1: Schematic representation of the beryl structure projected on the [001] basal plane from Lum et al. (2016) after Deer et al. (1966). The ion occupancies given for structural sites are not exhaustive.   75   Figure 2: Emerald mines and notable geologic features in the Eastern Cordillera, Colombia (modified from Banks et al. 2000).  76     Figure 3: The study area delineated by data coverage within Selwyn Basin.  77    Figure 4: Data coverage for stream sediment geochemistry. Re-analysis of samples in 2016 added data for important elements (including K, Li, and Be) to many points within black shale lithologies as shown above.  78   Figure 5: Major thrust zones of the Selwyn Basin (compiled from Héon [2003]). !!!!!Major Thrust ZonesMackenzie Mountains (Thrust/Fold Belt)DAWSON THRUSTTOMBSTONE THRUSTROBERT SERVICE THRUSTFaroMayoDawsonCarmacksHaines Junction0 60 12030 km´Black Shale UnitsRoads 79     Figure 6: Data coverage for Na INAA analyses of stream sediment geochemistry.   80     Figure 7: Anomalous sodium values in stream sediment within black shale lithologies. Black shales are shown in grey, and undifferentiated igneous rocks are shown in pink. See data coverage figures for precise INAA and ICP-MS data boundaries. Overlapping anomalies of INAA and ICP-MS measurements are solid purple.  81    Figure 8: Potassium in stream sediment within anomalous sodium areas in black shale. Lower K values are considered more prospective for Colombian-type emerald.  82     Figure 9: The “Beus” equation Na3/(Li*K*Mo) applied to sodium anomalies in black shale (Beus 1979).  83    Figure 10:  Beryllium concentration in stream sediment within sodium anomalies in black shale.  84     Figure 11: Chromium and vanadium in stream sediment within sodium anomalies in black shale.  85  Figure 12: Be and Cr+V are multiplied to illustrate unusual drainages that are likely enriched in all of these elements. With reference to the individual Be, and Cr+V plots uneven weighting of either element can be ruled out.  86      Figure 13: LREE values are plotted with sodium anomalies in black shale. High and low extremes are coloured such that interpretations of leaching and enrichment may be possible.   87   Figure 14: Summary of traverses and geologic features in the Mountain River Beryl region.  88     Figure 15:  The Rusty Shale Formation of the Little Dal Group is exposed just South of the Keele River. Stromatolitic grey dolostone cliffs seen behind are stratigraphically above. Photo taken at approximately 63° 52' 44.71", -127° 51' 42.56" facing southwest.  89    Figure 16: Several prospective areas are outlined based on the previous figures. Otherwise interesting sediment geochemical anomalies with high K values were discarded.   90   Figure 17: Geology of the Lened occurrence (modified after Adie & Allen 1960, Wise 1973, Gordey 1992).  The units are from oldest, PЄV: Precambrian-Cambrian Vampire Formation (clastic sediments); ЄOR: Cambrian-Ordovician Rabbitkettle Formation (argillaceous limestone); OSD: Ordovician-Silurian Duo Lake Formation and DMP: Devonian-Mississippian Portrait Lake Formation: black siliceous mudstone and clastic sediments; Cretaceous Lened two-mica granite composite pluton; and undifferentiated skarn.  At least one sub-vertical fault strikes northwest, placing younger black shales to the East beside Precambrian-Ordovician clastic rocks and limestone to the West. Grid coordinates are UTM (WGS 84, zone 9).  91     Figure 18: Black siliceous mudstone near the skarn varies from a sooty texture (A and to a lesser-extent B) to light-grey and phyllitic (C), implying significant thermal alteration and metasomatism.  (A) Imbricate fold and thrust structures in mudstone are revealed by a barren calcite-quartz vein that predates the largely undeformed quartz-emerald veins.  (B) Chlorite porphyroblasts developed in altered mudstone.  (C) Altered mudstone with phyllitic texture and radial aggregates of muscovite that may be pseudomorphs of muscovite after pyrite as shown by dashed lines (D, sample L06).  Amphibole is sparsely developed in contact metamorphosed phyllitic mudstone and can be found twinned (E, scale is ~25 µm, sample HF-13) and as prismatic, vitreous, red-brown porphyroblasts (F), scale is ~0.8 mm, sample L06).  92   Figure 19: (A) Emerald-bearing quartz veins cut a light grey skarn body (in box) high on Lened Ridge; view is to the northeast with helicopter for scale. Continued next page…  93 Figure 19 Cont.: … (B) Quartz veins with calcite, muscovite, beryl, tourmaline, scheelite, and pyrite (larger veins indicated with grey arrows and pictured veins marked with inset letter) cut skarn (outlined in grey) on a steep outcrop.  Mudstone (Mds) outcrops structurally below skarn that is developed in the Rabbitkettle Formation limestone (ЄOR).  Photo looking to the southwest; Bradley S. Wilson provides scale at lower right.  C) View of the carbonate/skarn unit over black siliceous mudstone containing thin intercalated carbonate beds. The dashed white line traces out one of the many quartz veins that crosscut the skarn.  (D) Sharp contact between mudstone (left) and skarn (right). Examination of this contact did not reveal visual evidence of shearing, suggesting that a primary sedimentary contact is preserved in this stratigraphic section.  (E) Veins typically pinch out immediately in less-altered limestone as shown in red; the dashed line marks the approximate boundary between skarn and hornfelsed limestone.  (F) A tight isoclinal micro-fold in a calcareous layer within the black sedimentary unit. Note the subhorizontal fold axis and steeply dipping axial plane.  (G, H) Examples of emeraldiferous quartz veins crosscutting the carbonate/skarn unit, as traced out by white dashed lines. Importantly, the quartz veins are clearly not folded and must post-date the folding seen in structurally underlying sedimentary rocks (see image F, and Fig. 2A).  (I) Close-up view of emeraldiferous quartz vein showing euhedral quartz and open space texture typical of extensional veins.  94   Figure 20: Skarn minerals and textures.  (A) Representative skarn cut by two small quartz (qtz) veins. Clinopyroxene (cpx) and radial amphibole (am) crystals are delineated by the olive-green colour, garnet (grt) is brown, and white wollastonite (wo) is interstitial to garnet (sample HF-21).  (B) Porphyroblastic clinopyroxene and radial wollastonite are developed in fine-grained matrix of amphibole, mica, and calcite (cc) (sample HF-15).  (C) Skarn from the shale/carbonate contact shows porphyroblastic garnet crystals in a fine-grained matrix of amphibole, mica, and calcite (sample HF-10).  (D) Thin zones of coarse euhedral vesuvianite (ves) with interstitial calcite (shown) are developed on a pyroxene (±garnet) matrix.  (E) Rhythmic pyroxene-garnet-vesuvianite skarn banding overprints an earlier penetrative fabric delineated by folded calcite stringers with parasitic folds.  (F) Pervasive amphibole porphyroblast development has created a distinctive fabric at the periphery of skarn alteration hosted by Rabbitkettle Formation argillaceous carbonate rock.  95     Figure 21: Details of emerald-bearing quartz veins from Lened.  The composite visible-light and shortwave UV image shows vein minerals quartz (qtz), beryl (brl), tourmaline (tur), and blue-white fluorescing, white scheelite (sch), in sharp contact with the skarn host.  (B) Another quartz vein with beryl var. emerald (em), shows pervasive muscovite (ms) alteration in the selvage.  (C) Close-up of larger emerald crystals in quartz with aggregates of muscovite (ms).  (D) High aspect-ratio inclusions of (often colourless) beryl, and tourmaline, are seen under binocular microscope, here as inclusions in a larger euhedral quartz crystal.  The lower tourmaline crystal has a blue cap.  96   Figure 22: Three pale bluish-green faceted emeralds from Lened. From left to right the cut gems weigh 0.14, 0.16, and 0.07 carats. The largest faceted emerald known from this locality weighs 0.17 ct (Wilson 2014).  97   Figure 23: Al versus the sum of other Y-site cations, in atoms per formula unit, for 88 Lened emerald compositions and 435 emerald compositions from the literature.  The number of analyses per country is given in brackets in the legend.  Data from Groat et al. (2014) and references therein.  98   Figure 24: Mg + Mn + Fe vs. monovalent channel-site cations, in atoms per formula unit, for rim, intermediate, and core zones of Lened emeralds compared with V-emerald compositions from Eidsvoll, Norway (Loughrey et al. 2013), Dyakou, China (Huang et al. 2015), and Muzo, Colombia (Ottaway 1991).  99   Figure 25: Triangular diagram of FeO-Cr2O3-V2O3 weight percentages from analyses of emerald in this study, and analyses from the literature (with all Fe as FeO).  Compositional fields of worldwide V-emerald localities are outlined. Sources of data are the same as Figures 7 and 8.  The diagrams are after Hammarstrom (1989).  100     Figure 26: Al-Fe(tot)-Mg diagram (in molecular proportions) for tourmaline shows that Lened tourmaline is Mg-rich dravite and plots in fields characteristic of tourmaline from metapelites. Numbered compositional fields from Henry & Guidotti (1985) refer to tourmaline compositions characteristic of certain rock types: (1) Li-rich granitoid/aplites (2) Li-poor granitoids, aplites and pegmatites, (3) Fe3+-rich quartz-tourmaline rocks (hydrothermally altered granites), (4) metapelites and metapsammites with Al-saturating phase, (5) metapelites and metapsammites without Al-saturating phase, (6) Fe3+-rich quartz-tourmaline rocks, calc-silicates, and metapelites, (7) low-Ca metaultramafics and Cr,V-rich metasediments, and (8) metacarbonates and meta-pyroxenites.  101    Figure 27: Si-R2+ mica classification diagram in molecular proportions after Wiewióra & Weiss (1990).  Mica in emerald veins plots on the muscovite-aluminoceladonite tie line. It is best classified as a phengitic dioctahedral mica that shows a trend of limited trioctahedral substitution toward a biotitic composition between annite/phlogopite and siderophyllite/eastonite.  102   Figure 28: 40Ar-39Ar incremental heating plateaus for Lened pluton and emerald veins. Top left: annite from unfoliated coarse grained granite with 4 mm grain size and zoned feldspars (DM-02-05). Top right: annite from granite at the granite-skarn contact (DM-02-07). Lower left: emerald vein muscovite (HF-22). Lower right: emerald vein muscovite (HF-22B).  103 Figure 29: Channel δDH2O versus calculated δ18OH2O (‰, V-SMOW) for emeralds from Lened and other granite-related and Canadian emerald localities. The Habachtal, Austria field is given as an example of a schist-hosted metamorphic emerald deposit for comparison (Groat et al. 2014). The isotopic compositional fields are from Sheppard (1986). The H-δ18OH2O isotopic field for Lened (green box) was calculated at 350 °C. Channel δD is between -62.0 and -87.4‰ (see Table 5). Worldwide emerald isotopic fields are from Groat et al. (2014), Loughrey et al. (2013), and Giuliani et al. (2015). The diagram is after Giuliani et al. (1997b).  104   Figure 30: Calculated δ18OH2O (‰, V-SMOW) for fluid in equilibrium with granitic quartz (600-700°C; Matsuhisa et al. 1979), vein quartz, and vein beryl (both 300-400°C; Matsuhisa et al. 1979, and Zheng 1993a). The grey box corresponds to peraluminous “Cornubian” granitic fluid of Sheppard (1986). Error bars and light blue areas show a 2σ (analytical error only) confidence range, and the darker blue line in the center is the mean.    105  Figure 31: Boron isotopic composition of tourmaline from Lened and Tsa da Glisza (Galbraith et al. 2009) and a compilation of δ11B (‰) values for various lithologies (Jiang & Palmer 1998).  106 References Adie, L. & Allen, T.M. 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Thesis, University of Missouri-Columbia, Columbia, Missouri, U.S., 105 pp. Zaw, K. (1976) The Cantung E-Zone orebody, Tungsten, Northwest Territories; a major scheelite skarn deposit. Ph.D. Thesis, Queen’s University, Kingston, Ontario, Canada, 327 pp. Zheng, Y.-F. (1993a). Calculation of oxygen isotope fractionation in anhydrous silicate minerals. Geochimica et Cosmochimica Acta 57, 1079-1091.  Zheng, Y.-F. (1993b) Calculation of oxygen isotope fractionation in hydroxyl-bearing silicates. Earth and Planetary Science Letters 120, 247–263.  120 Appendix A: Utah Rumours of a Colombian-type emerald occurrence in Utah have circulated for several years. If valid, this would be the only such emerald occurrence known outside of Colombia and potentially a useful case study with direct relevance to this thesis. Two days in 2015 were spent with Philippe Belley (PhD. candidate) in the Uinta Mountains of Utah to investigate reports of Colombian-type emerald mineralization near Rock creek that have circulated since as early as the mid-1990s (e.g. Keith et al. 1996). This work was abandoned after two days of investigation in the “emerald discovery area” (described by Nelson et al. 2008). “Black” shale in this area is a typical dark brown-grey recessive marine shale lacking the visibly high organic matter contents that characterize Colombian black shale. Washing, sieving, and panning of several 20 L buckets of sediment from Rock Creek failed to recover beryl, albite, vein quartz, coarse pyrite or any heavy minerals that would be expected to occur in the drainage of a Colombian-type emerald occurrence. A small amount of fine-grained stratabound pyrite is found in dark grey-brown shale outcrop at Rock creek, and is probably diagenetic. We did not see evidence of significant hydrothermal alteration or veining in the area. Based on these observations it is the opinion of this author that the reported emerald occurrence is of questionable validity. This opinion is potentially corroborated by beryl– reportedly found in Rock Creek– having compositions closely matching Brazilian emerald compositions (Nelson et al. 2008). No further work or analysis was performed on sediment or whole rock shale samples from this site.  !!!


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