Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada.
Strata-bound, gold-bearing quartz-breccia zones at Gordon Lake, near Yellowknife, N.W.T., occur within carbon-rich siltstone beds of the Archean Burwash Formation, and are located within the hinge domain of a subvertical regional refold. Structural analysis indicates that although some quartz veinin...
Main Author: | |
---|---|
Other Authors: | |
Format: | Text |
Language: | English |
Published: |
Dalhousie University
2014
|
Subjects: | |
Online Access: | http://hdl.handle.net/10222/55295 |
id |
ftdalhouse:oai:DalSpace.library.dal.ca:10222/55295 |
---|---|
record_format |
openpolar |
spelling |
ftdalhouse:oai:DalSpace.library.dal.ca:10222/55295 2023-05-15T17:46:46+02:00 Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. Stokes, Timothy Robert. Ph.D. 2014-10-21T12:38:11Z http://hdl.handle.net/10222/55295 eng eng Dalhousie University AAINN71569 http://hdl.handle.net/10222/55295 Geology text 2014 ftdalhouse 2021-12-29T18:11:48Z Strata-bound, gold-bearing quartz-breccia zones at Gordon Lake, near Yellowknife, N.W.T., occur within carbon-rich siltstone beds of the Archean Burwash Formation, and are located within the hinge domain of a subvertical regional refold. Structural analysis indicates that although some quartz veining developed before peak metamorphism and formation of a regional cleavage (S$\sb3$), more significant quartz veining, brecciation, and gold mineralization occurred later (late-D$\sb3$ to syn-D$\sb4$), concurrent with formation of a crenulation cleavage (S$\sb4$) and counter-clockwise rotation of the east limb of the refold. Microfractures within the quartz-breccias have abundant fluid inclusions of high salinity ($\sim$25 wt% NaCl-CaCl$\sb2$) and hydrocarbon concentration (e.g., CH$\sb4$ and C$\sb2$H$\sb2$). Gold in the quartz breccias occurs with arsenopyrite, pyrite, and pyrrhotite, and was probably emplaced at ca. 450 $\pm$ 40$\sp\circ$C and a depth of 7-12 km. Hydrothermal alteration enriched the siltstone host in Au, As, Sb, (Br), S, K, Ca, and Na. The high C and low SiO$\sb2$ content of the host siltstone is probably a primary feature of the metasediments rather than a product of alteration. $\sp{40}$Ar/$\sp{39}$Ar dating of a metamorphic hornblende and a muscovite from a post-metamorphic pluton constrain the time of (D$\sb3$) peak metamorphism to ca. 2600 Ma. A plateau age of 2573 $\pm$ 9 Ma for a biotite from the largest quartz-breccia zone gives a minimum age for mineralization, consistent with the late metamorphic timing of the brecciation event. The data are compatible with a genetic model that derives the gold and the fluids from the arc-related volcaniclastic metaturbidite pile, transports the gold as chloride complexes in a moderately saline (and oxidized?) fluid, and deposits the gold, quartz, and sulphides in hydraulically-induced brittle fractures within the reducing carbon-rich silstones. Thesis (Ph.D.)--Dalhousie University (Canada), 1991. Text Northwest Territories Yellowknife Dalhousie University: DalSpace Institutional Repository Canada Northwest Territories Yellowknife |
institution |
Open Polar |
collection |
Dalhousie University: DalSpace Institutional Repository |
op_collection_id |
ftdalhouse |
language |
English |
topic |
Geology |
spellingShingle |
Geology Stokes, Timothy Robert. Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
topic_facet |
Geology |
description |
Strata-bound, gold-bearing quartz-breccia zones at Gordon Lake, near Yellowknife, N.W.T., occur within carbon-rich siltstone beds of the Archean Burwash Formation, and are located within the hinge domain of a subvertical regional refold. Structural analysis indicates that although some quartz veining developed before peak metamorphism and formation of a regional cleavage (S$\sb3$), more significant quartz veining, brecciation, and gold mineralization occurred later (late-D$\sb3$ to syn-D$\sb4$), concurrent with formation of a crenulation cleavage (S$\sb4$) and counter-clockwise rotation of the east limb of the refold. Microfractures within the quartz-breccias have abundant fluid inclusions of high salinity ($\sim$25 wt% NaCl-CaCl$\sb2$) and hydrocarbon concentration (e.g., CH$\sb4$ and C$\sb2$H$\sb2$). Gold in the quartz breccias occurs with arsenopyrite, pyrite, and pyrrhotite, and was probably emplaced at ca. 450 $\pm$ 40$\sp\circ$C and a depth of 7-12 km. Hydrothermal alteration enriched the siltstone host in Au, As, Sb, (Br), S, K, Ca, and Na. The high C and low SiO$\sb2$ content of the host siltstone is probably a primary feature of the metasediments rather than a product of alteration. $\sp{40}$Ar/$\sp{39}$Ar dating of a metamorphic hornblende and a muscovite from a post-metamorphic pluton constrain the time of (D$\sb3$) peak metamorphism to ca. 2600 Ma. A plateau age of 2573 $\pm$ 9 Ma for a biotite from the largest quartz-breccia zone gives a minimum age for mineralization, consistent with the late metamorphic timing of the brecciation event. The data are compatible with a genetic model that derives the gold and the fluids from the arc-related volcaniclastic metaturbidite pile, transports the gold as chloride complexes in a moderately saline (and oxidized?) fluid, and deposits the gold, quartz, and sulphides in hydraulically-induced brittle fractures within the reducing carbon-rich silstones. Thesis (Ph.D.)--Dalhousie University (Canada), 1991. |
author2 |
Ph.D. |
format |
Text |
author |
Stokes, Timothy Robert. |
author_facet |
Stokes, Timothy Robert. |
author_sort |
Stokes, Timothy Robert. |
title |
Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
title_short |
Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
title_full |
Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
title_fullStr |
Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
title_full_unstemmed |
Gold-bearing quartz-breccia zones in Archean metasediments of the Gordon Lake region, Northwest Territories, Canada. |
title_sort |
gold-bearing quartz-breccia zones in archean metasediments of the gordon lake region, northwest territories, canada. |
publisher |
Dalhousie University |
publishDate |
2014 |
url |
http://hdl.handle.net/10222/55295 |
geographic |
Canada Northwest Territories Yellowknife |
geographic_facet |
Canada Northwest Territories Yellowknife |
genre |
Northwest Territories Yellowknife |
genre_facet |
Northwest Territories Yellowknife |
op_relation |
AAINN71569 http://hdl.handle.net/10222/55295 |
_version_ |
1766150616148606976 |