Geology and Lithogeochemistry and Mineralization in the Buck Creek Area(1:1 000 000)
(NTS 093E, K, L)
Paper 1990 - 2
Paper (PDF 8 MB)
Maps (PDF 14 MB)
Download Appendix (Excel ZIP, 605 KB)
Paper 1990-2 describes the geology and mineral deposits of the Buck Creek area, which is approximately 3000 square kilometres of mostly rolling subalpine terrain in the Nechako Plateau region of central British Columbia. The area is underlain by a diverse suite of Mesozoic and Tertiary volcanic rocks and small igneous intrusions.
The main stratigraphic divisions comprise a basement sequence of metamorphosed strata of Jurassic and possibly Early Cretaceous age, and cover rocks of Late Cretaceous and Tertiary age. The basement rocks are commonly poorly exposed and little is known about their thickness and regional structure. The cover rocks, referred to here as the Francois Lake group have been mapped in detail and are divided into four volcanic formations and one sedimentary formation.
The intrusions are acid, intermediate and basic alkaline types. Most are clearly younger than the basement strata and some are volcanic necks and feeder dikes to the overlying Cretaceous and Tertiary volcanic rocks.
The subcircular distribution of rhyolite beds at the base of the Francois Lake group outlines a broad volcano-tectonic basin, with a central resurgent uplifted area near the Equity mine, and Lower Tertiary volcanic rocks within a peripheral moat. Along a prominent lineament, 30 kilometres in length and radial to the resurgent centre, the Equity and Silver Queen mines are connected by a series of feeder intrusions to the Francois Lake group volcanic rocks.
Porphyry copper and molybdenum mineralization is associated with Late Cretaceous-Early Tertiary granitoid intrusions and rhyolites on the rim and in the central area of the basin. Somewhat younger copper-lead-zinc veins, such as at the Silver Queen mine, and silver-copper-rich fracture fillings, disseminations and replacements, as at the Equity mine, are related to the Goosly syenomonzonite intrusions.
At the Equity mine erosion has exposed the upper part of the Goosly stock and subvolcanic structures. A thickened zone of disseminated and massive sulphides rich in pyrite, chalcopyrite and tetrahedrite, with some pyrrhotite, minor sphalerite and magnetite, is mostly adjacent to the stock. Aluminous alteration, characterized by andalusite, scorzalite, pyrophyllite and corundum, accompanies much of this mineralization. A narrow tail-like appendage to the ore zone strikes south and away from the main orebody.
The Silver Queen deposit is a system of mesothermal and epithermal polymetallic veins. These are mostly pyrite and sphalerite rich with accessory chalcopyrite, galena and tennantite within a quartz, rhodochrosite and barite-rich gangue.
The veins are enveloped by argillic rocks within a broader aureole of propylitic alteration. Dikes related to the Goosly intrusions are contemporaneous with vein emplacement.
It appears that the Silver Queen and Equity deposits are genetically related, and together represent a full spectrum in a hydrothermal plumbing system driven by the Goosly intrusions.
A lithogeochemical study of the Buck Creek basin confirms the subcircular form of this structure and highlights the many known mineral showings and ore deposits. The dispersion of elements about certain igneous intrusions, such as the Goosly stock at the Equity mine, supports the theory that correlates intrusive events with mineralization.
The lithogeochemical data table, available as an Excel file, represents analysis for 1791 rock samples.
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