Geology, alteration, lithogeochemistry and hydrothermal fluid characterization of the Neoproterozoic Niblack polymetallic volcanic-hosted massive sulfide camp, southeast Alaska, USA
department or school: Science, Faculty of
department or school: Earth, Ocean and Atmospheric Sciences, Department of
data provider: DSpace
degree campus: UBCV
creator: McNulty, Brian
issued: 2014-02-11T22:25:54Z
issued: 2014
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: The Neoproterozoic Alexander terrane Niblack Cu-Au-Zn-Ag volcanic-hosted massive sulfide camp is on Prince of Wales Island, southeast Alaska. Multiple massive sulfide deposits occur at different stratigraphic levels in 565 ±1.25 Ma felsic volcanic strata. Host rocks are vent-proximal felsic pyroclastic volcanic breccia, lapilli tuff, coherent flows (Lookout deposit, Trio zone) and vent-distal felsic ash tuffs (Niblack Mine, Mammoth and Dama zones). New geochemical data and volcanic lithofacies indicate the host stratigraphy was deposited in a juvenile oceanic back-arc basin. Sub-seafloor mineralization (Lookout deposit, Trio zone) consists of 15-75% sulfide with disseminated to net-textured to semi-massive sulfide textures. These ores precipitated in unconsolidated water-laden vent-proximal felsic volcanic stratigraphy. Seafloor exhalative mineralization (Niblack Mine, Mammoth and Dama zones) is comprised of massive (>90%) poorly-banded sulfide. This type of sulfide precipitated on the paleo-seafloor in, or above, less-permeable vent-distal felsic ash tuff stratigraphy. Sub-seafloor sulfide, related hydrothermal alteration assemblages, and variations in metal ratios represent hydrothermal fluid flow and cooling through the host stratigraphy. Temperature estimates from chlorite microprobe data indicate sub-seafloor 1:1 Cu:Zn and 1:10 Au:Ag chlorite-rich alteration (Lookout deposit) formed at 321 ±19°C and seafloor exhalative 3:1 Cu:Zn and 1:10 Au:Ag magnesium-rich chlorite alteration (Niblack Mine) formed at 307 ±16°C. Sulfur, oxygen, deuterium and carbon stable isotope results are used to identify the origin of hydrothermal fluids. Sulfide mineral separates have δ³⁴S values of +6.6 to +10.5‰. Calculated fluid compositions of chlorite and sericite have values of +2.3 to +5.9‰ δ¹⁸O(water) and -24.9 to -77.1‰ δD(water). Calculated δ¹⁸O(water) values of magnetite are +8.1 to +15.5‰ and values of carbonate are -13.5 to +9.0‰ δ¹⁸O(water) and -4.4 to -0.5‰ δ¹³C(calcite). T…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/46005
note: Geology, Alteration, Lithogeochemistry and Hydrothermal Fluid Characterization of theNeoproterozoic Niblack Polymetallic Volcanic-Hosted Massive Sulfide Camp, Southeast Alaska, USAbyBrian McNultyB.Sc., The University of Alaska Fairbanks, 2007A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIRMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES(Geological Sciences)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)February 2014? Brian McNulty 2014AbstractThe Neoproterozoic Alexander terrane Niblack Cu-Au-Zn-Ag volcanic-hosted massive sulfide camp is on Prince of Wales Island, southeast Alaska. Multiple massive sulfide deposits occur at different stratigraphic levels in 565 ?1.25 Ma felsic volcanic strata. Host rocks are vent-proximal felsic pyroclastic volcanic breccia, lapilli tuff, coherent flows (Lookout deposit, Trio zone) and vent-distal felsic ash tuffs (Niblack Mine, Mammoth and Dama zones). New geochemical data and volcanic lithofacies indicate the host stratigraphy was deposited in a juvenile oceanic back-arc basin. Sub-seafloor mineralization (Lookout deposit, Trio zone) consists of 15-75% sulfide with disseminated to net-textured to semi-massive sulfide textures. These ores precipitated in unconsolidated water-laden vent-proximal felsic volcanic stratigraphy. Seafloor exhalative mineralization (Niblack Mine, Mammoth and Dama zones) is comprised of massive (>90%) poorly-banded sulfide. This type of sulfide precipitated on the paleo-seafloor in, or above, less-permeable vent-distal felsic ash tuff stratigraphy.Sub-seafloor sulfide, related hydrothermal alteration assemblages, and variations in metal ratios represent hydrothermal fluid flow and cooling through the host stratigraphy. Temperature estimates from chlorite microprobe data indicate sub-seafloor 1:1 Cu:Zn and 1:10 Au:Ag chlorite-rich alteration (Lookout deposit) formed at 321 ?19?C and seafloor exhalative 3:1 Cu:Zn and 1:10 Au:Ag magnesium-rich chlorite alteration…
has type: Thesis/Dissertation
date issued: 2014-05
is shown at: 10.14288/1.0165874
language: eng
degree discipline: Geological Sciences
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/46005