PhD Dissertation Defense: Sergey Konyshev
Title: Metasedimentary Rock-hosted Au (Sb-Hg) Deposits within the Stibnite Roof Pendant, Yellow Pine Mining District, Idaho
Advisor: Dr. John Muntean, NBMG
When: Monday, August 3rd at 10:00 AM, PDT, via Zoom
Contact: Sergey at skonyshev@nevada.unr.edu for Zoom meeting access information.

Abstract: The Yellow Pine Mining District, located in central Idaho, has produced nearly 900,000 ounces of gold and significant amounts of silver (>2.5 million ounces), antimony (50,000 tons) and tungsten (845K units). Midas Gold Idaho Inc., who is currently exploring the district, has defined a substantial gold resource along with the largest antimony deposit in the conterminous United States.

Gold mineralization in the district is located mainly within Late Cretaceous granitic rocks of the Atlanta lobe of the Idaho Batholith. Significant mineralization also occurs within lower Paleozoic metasedimentary rocks in the Stibnite roof pendant. Gold is typically found as disseminated mineralization, but also is present in several temporally distinct generations of veins, which overprint each other, thereby complicating the study. Determining which mineralization event deposited the bulk of the gold was an important objective of this study.

The work involved in this study began with field mapping and sampling of key metasedimentary-hosted gold occurrences, along with core logging, mapping of accessible benches in open pits and construction of compilation maps and cross-sections of the deposits. This was followed by petrography, including transmitted and reflected light microscopy, scanning electron microscopy, and cathodoluminescence; and analyses of pyrite and arsenopyrite with an electron microprobe and laser ablation ICP-MS, as well as geochronology and thermochronology. Particular emphasis was placed on understanding the specific lithologic, stratigraphic and structural controls on carbonate-hosted gold mineralization and identifying cross-cutting relationships between the various styles of mineralization, structures, and intrusions and understanding the deportment of gold and other metals in each style of mineralization.

Part one of the study focuses on the largest metasedimentary-hosted gold deposit in the area, West End. Part two describes the diversity of mineralization found in the roof pendant, with a major focus on gold. Part three focuses on an apatite fission track study, which was conducted to try to establish when the Stibnite roof pendant was exhumed, and combining other geochronologic work to understand the history and evolution of the different stages of mineralization.

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