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UBC Theses and Dissertations
UBC Theses and Dissertations
Petrology and tectonic setting of felsic and mafic volcanic and intrusive rocks in the Finlayson Lake volcanic-hosted massive sulphide (VHMS) district, Yukon, Canada : a record of mid-Paleozoic arc and back-arc magmatism and metallogeny Piercey, Stephen John
Abstract
The Yukon-Tanana Terrane (YTT) in the Finlayson Lake region (FLR), southeastern Yukon, Canada is host to five volcanic-hosted massive sulphide (VHMS) deposits (total -34 Mt) that have been discovered since the mid-1990's. In this thesis, field, lithogeochemical and Nd isotopic data are presented for felsic and mafic igneous rocks in the FLR to understand the tectonic setting, style of magmatism, and their relationships to VHMS mineralization. All rocks in the FLR were built upon a continental (or continent-derived) substrate of pre-Mississippian (>365 Ma) age. The Fire Lake unit (FLU) reflects Devonian-Mississippian (-365-360 Ma) arc and back-arc magmatism built upon a composite basement of oceanic and continental (or continent-derived) crust above an east-dipping subduction zone. Models proposed herein for the magmatic and tectonic evolution of FLU include: 1) arc magmatism punctuated by back-arc basin generation; 2) ridge propagation into an evolving arc with subsequent evolution to back-arc magmatism; and/or 3) ridge-subduction (slab-window) with eventual back-arc basin magmatism. The Kudz Ze Kayah (KZK) unit overlies the FLU and consists predominantly of crustally derived Devonian-Mississippian (-360-356 Ma) felsic volcanic and high-level subvolcanic rocks and variably carbonaceous sedimentary rocks; the latter are crosscut and overlain by alkalic mafic rocks. The high field strength element (HFSE)-enriched (A-type) felsic rocks and alkalic mafic rocks in the KZK unit are inferred to represent magmatism within an ensialic back-arc basin upon evolved crust. The Wolverine succession (WS) unconformably overlies the KZK unit and consists of a lower succession of felsic volcanic and subvolcanic rocks with carbonaceous sedimentary rocks; the upper portion of the succession, above the Wolverine VHMS deposit, consists predominantly of aphyric rhyolitic rocks that are overlain basalt flows. Felsic rocks ofthe WS are broadly similar to those in the KZK unit and represent ensialic back-arc basin magmatism. However, the succession is younger (-356-346 Ma), and post-dates a period of uplift, deformation, and erosion prior to commencement of back-arc magmatism. Back-arc spreading eventually evolved to true seafloor spreading within the WS. Massive sulphide deposits in the FLR are preferentially associated with rocks indicative of high temperature magmatism (e.g., boninites, A-type felsic rocks) and extensional tectonic activity (e.g., back-arc rifting and spreading).
Item Metadata
Title |
Petrology and tectonic setting of felsic and mafic volcanic and intrusive rocks in the Finlayson Lake volcanic-hosted massive sulphide (VHMS) district, Yukon, Canada : a record of mid-Paleozoic arc and back-arc magmatism and metallogeny
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2001
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Description |
The Yukon-Tanana Terrane (YTT) in the Finlayson Lake region (FLR), southeastern
Yukon, Canada is host to five volcanic-hosted massive sulphide (VHMS) deposits (total -34 Mt)
that have been discovered since the mid-1990's. In this thesis, field, lithogeochemical and Nd
isotopic data are presented for felsic and mafic igneous rocks in the FLR to understand the
tectonic setting, style of magmatism, and their relationships to VHMS mineralization. All rocks
in the FLR were built upon a continental (or continent-derived) substrate of pre-Mississippian
(>365 Ma) age. The Fire Lake unit (FLU) reflects Devonian-Mississippian (-365-360 Ma) arc
and back-arc magmatism built upon a composite basement of oceanic and continental (or
continent-derived) crust above an east-dipping subduction zone. Models proposed herein for the
magmatic and tectonic evolution of FLU include: 1) arc magmatism punctuated by back-arc basin
generation; 2) ridge propagation into an evolving arc with subsequent evolution to back-arc
magmatism; and/or 3) ridge-subduction (slab-window) with eventual back-arc basin magmatism.
The Kudz Ze Kayah (KZK) unit overlies the FLU and consists predominantly of crustally
derived Devonian-Mississippian (-360-356 Ma) felsic volcanic and high-level subvolcanic rocks
and variably carbonaceous sedimentary rocks; the latter are crosscut and overlain by alkalic mafic
rocks. The high field strength element (HFSE)-enriched (A-type) felsic rocks and alkalic mafic
rocks in the KZK unit are inferred to represent magmatism within an ensialic back-arc basin upon
evolved crust.
The Wolverine succession (WS) unconformably overlies the KZK unit and consists of a
lower succession of felsic volcanic and subvolcanic rocks with carbonaceous sedimentary rocks;
the upper portion of the succession, above the Wolverine VHMS deposit, consists predominantly
of aphyric rhyolitic rocks that are overlain basalt flows. Felsic rocks ofthe WS are broadly
similar to those in the KZK unit and represent ensialic back-arc basin magmatism. However, the
succession is younger (-356-346 Ma), and post-dates a period of uplift, deformation, and erosion
prior to commencement of back-arc magmatism. Back-arc spreading eventually evolved to true
seafloor spreading within the WS.
Massive sulphide deposits in the FLR are preferentially associated with rocks indicative
of high temperature magmatism (e.g., boninites, A-type felsic rocks) and extensional tectonic
activity (e.g., back-arc rifting and spreading).
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Extent |
37198472 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-10-10
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0052473
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2001-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.