Taseko Management Zone: Evolution of Porphyry and Epithermal Mineralization within a Magmatic-Hydrothermal System (NTS 92O/04)
- Lori Kennedy, University of British Columbia

Taseko Lakes Study Area This two-year research project will investigate the characteristics of volcano-plutonic architecture and associated porphyry- epithermal mineralization in the Taseko Lakes region, located in southwestern British Columbia. We will integrate detailed geological, structural and alteration mapping, petrology, isotope geochemistry and geochronological analyses with the aim of developing a conceptual geological model for the structural and economic evolution of the area for the purpose and application of predictive exploration.

The project area is located within the Coast Belt, along the boundary between the Southeast Coast Belt and Southwest Coast Belt (Monger and Journeay, 1994). This area is located at the eastern limit of the Coast Plutonic Complex, and it is along this boundary that many Cu-Mo-Au showings are located in the southern Coast Belt (McLaren, 1990). This highly tectonized belt includes Paleozoic to mid-Mesozoic oceanic and volcanic arc rocks assigned to several different terranes, together with Late Middle Jurassic through mid-Cretaceous sedimentary rocks of the Tyaughton- Methow basin, Upper Cretaceous continental arc volcanic rocks of the Powell Creek formation and mid-Cretaceous to Tertiary intrusive rocks of the Coast Plutonic Complex (Schiarizza et. al., 1997).

Posters and Presentations
2008 : For Prosperity's sake: A Late Cretaceous theme to porphyry systems in the SW Coast Mountains
- Mineral Exploration Roundup Poster (pdf, 1.76MB)

2008 : Contrasting Copper and Gold Mineralization Styles along the Contact between the Coast Plutonic Complex and the Southeast Coast Belt, Taseko Lakes Region (NTS 092O/04), Southwestern British Columbia
- Mineral Exploration Roundup Poster (pdf, 19.7MB)

2007 : Mineralization, Alteration and Structure in the Taseko Lakes Region, Southwestern BC: Preliminary Analysis
- Mineral Exploration Roundup Poster (pdf, 2.46MB)

Technical Articles
2008 : "Mineralization and alteration of Cretaceous rocks of the Taseko Lakes region, southwestern British Columbia (NTS 092O/04)"
- Summary of Activities 2008, Report 2009-1 p.75-90 (pdf, 14.6MB)

2007 : "Controls on copper and gold mineralization along the contact between the Coast Plutonic Complex and the southeast Coast Belt, Taseko Lakes region, southwestern British Columbia (NTS 092O/04)"
- Summary of Activities 2007, Report 2008-1 p.21-34 (pdf, 4.64MB)

2007 : "Mineralization and alteration associated with an hypothesized copper (molybdenum) porphyry system in the Taseko Lakes area, southwestern British Columbia (NTS 092O/04)"
- Summary of Activities 2007, Report 2008-1 p.55-66 (pdf, 16.8MB)

2006 : "Mineralization, Alteration and Structure of the Taseko Lakes Region (NTS 092O/04), Southwestern British Columbia: Preliminary Analysis"
- Geological Fieldwork 2006, Paper 2007-1 p.297-306 (pdf, 4.68MB)

Final Deliverables
M.Sc. Thesis - S.K. Blevings
Geologic framework for late Cretaceous magmatic-hydrothermal mineralization in the Taseko Lakes region, Southwestern BC - University of British Columbia, 2008 - Available digitally through the University of British Columbia (pdf, 11.08MB)

Abstract: The Taseko Lakes region is located in Southwestern British Columbia along the contact between the Coast Plutonic Complex (CPC) and the Southeast Coast Belt (SECB). Three separate generations of faults occur in the region: sub-vertical sinistral-reverse faults (Dl), moderate- to high-angle south- and north-vergent contractional faults (D2) and large-scale dextral faults (D3). Several mineral deposits are located in the southern Taseko Lakes region. Three of these deposits were examined during this study: the Empress (porphyry Cu), Pellaire (gold-telluride) and Taylor-Windfall (high-suiphidation epithermal Au-Ag) deposits. The deposits were examined in order to characterize the known mineralization in the Taseko Lakes region and better understand the conditions and times at which mineralization took place. The Empress deposit formed at approximately 88 to 87 Ma at depths of roughly 5 km when large volumes of high-temperature, oxidized magmatic-hydrothermal fluids from an unidentified source intrusion migrated laterally along a trough-shaped topographic low along the upper margin of an underlying intrusion --- the Empress pluton. This horizontal flow produced subhorizontal-layered alteration and mineralization within the overlying Falls River succession. The Taylor-Windfall deposit formed at about 89 to 87 Ma when magmatic-dominated, moderate- to low-temperature hydothermal fluids ascended along faults and fractures. An initial high-temperature vapour phase produced a central core of vuggy-silica and corundum-andalusite alteration. A second phase of cooler, re-condensed vapours overprinted early high-temperature assemblages with lower temperature intermediate and advanced argillic alteration assemblages. The Pellaire deposit formed at 85 Ma when mineralizing fluids migrated distally from a magmatic source along (D2) south-vergent contractional faults. Mineralization occurred when fluids crossed from the Falls River succession into the Mount McLeod granodiorite and were cooled and disturbed from chemical equilibrium, which resulted in the emplacement of quartzveins in the south-vergent faults and deposition of ore minerals. All three deposits formed from magmatic-dominated fluids (with variable meteoric input) between approximately 89 and 85 Ma. The similarities in ages, fluid compositions and sources between the deposits indicate they formed from similar magmatic-hydrothermal systems. The varying mineralization styles exhibited by the deposits in this study illustrate the variability of mineralizing styles that can occur in magmatic-hydrothemal systems. This variability arises largely due to differing characteristics of pre-existing geology and the location of the deposits with respect to the overall system.

M.Sc. Thesis - L. Hollis
Cretaceous porphyry magmatic-hydrothermal systems in the Tchaikazan River area, southwest B.C - University of British Columbia, 2009 - Available digitally through the University of British Columbia (pdf, 13.73MB)

Abstract: The Hub, Charlie and Northwest Copper are spatially related mineral showings (Cu Mo) located in the Tchaikazan River area of southwest British Columbia. The Tchaikazan River area is located on the boundary between the Intermontane Belt and southeast Coast Belt (SECB). Evidence of magmatic-hydrothermal alteration is preserved throughout the study area. Multiple episodes of magmatic-hydrothermal activity are associated with these three centres of porphyry-style mineralization. The Hub diorite is the oldest dated pluton in the area, with a U-Pb zircon emplacement age of 81.19 0.78 Ma. ZFT/AFT data suggests an emplacement depth of> 4km for the Hub diorite. The Hub diorite is crosscut by a biotite magnetite ( quartz) matrix/cemented hydrothermal breccia. A feldspar hornblende dyke crosscuts both the diorite and hydrothermal breccia and gives a U-Pb zircon age of 79.9 1.5 Ma. Copper, molybdenite galena occurs in quartz veining and cement to the hydrothermal breccia. ZFT/U-Pb and Ar-Ar ages for the Hub diorite are within error of each other. AFT data suggests an average erosion rate of 40 m/myr for intrusive rocks in the Taseko Lakes area. Field relationships, geophysical anomalies, geochronology, and stable isotope data suggest that there are three centres for magmatic-hydrothermal activity in the Tchaikazan River area: The Hub, Northwest Copper pluton, and Ravioli Ridge. The area displays evidence for multiple, temporally-distinct intrusive, alteration and mineralizing events.


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