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Telluride mineralogy at the Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit, Lindquist Peak, west-central British Columbia : implications for the generation of tellurides Roberts, Jordan


The Deer Horn property is located 150 km south of Smithers in west-central British Columbia and covers 51 km². The deposit is an intrusion-related polymetallic system enriched in Au-Ag-Te-W-Cu with lesser amounts of Bi-Pb-Zn-Mo; the Au and Ag are hosted in telluride minerals. The quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and sericite alteration is found in the hanging wall of a local, spatially related thrust fault. The age of the sericite alteration is 56 ± 2 Ma. Biotite K-Ar ages of 57–48 Ma for the nearby Nanika granodiorite intrusive suite indicates that it is likely genetically responsible for the Au-Ag-Te mineralizing event. The telluride minerals are 0.1–525 μm and commonly form whole euhedral to subhedral grains or composite grains of Ag-, Bi-, Pb-, and Au-rich telluride minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Locally, oscillatory zoning observed in quartz II suggests the participation of hydrothermal fluids. Fine-grained veinlets of quartz III and IV intersect quartz I and II, which is evidence of at least two shearing events; veinlets of calcite intersect all generations of quartz. Three types of fluid inclusions were observed: (1) aqueous liquid and vapour inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (V-rich). Fluid inclusions that are thought to be primary or pseudosecondary and related to the telluride mineralization were tested with microthermometry. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Four of eight aqueous carbonic inclusions had solid CO2 melting temperatures from –56.8 to –62.1 °C, indicating the presence of 0.5–13.2% dissolved methane in these inclusions. Sulfur isotope analysis of ³⁴S/³²S using 20 samples of pyrite was conducted. δ³⁴S readings are close to 0 (from –1.6 to 1.6 per mil) and confirm that the sulfur is very likely magmatic/igneous in origin.

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