| Summary: | 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.
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