The Discovery and Geology of the Western Flank Zone at the Kinsley Mountain Project, Elko County, Nevada

摘要

The Kinsley Mountain Project is located in eastern Elko and White Pine counties, approximately 80 km south of West Wendover, Nevada. Modern gold exploration began in 1984 with the discovery of gold-bearing jasperoids on the east side of the Kinsley Range by U. S. Minerals Exploration Company. Cominco American Resources, Inc. and Hecla Mining Company explored the project before Alta Gold Company acquired and mined it, producing approximately 138,000 ounces of gold from oxidized mineralization hosted in the Upper Cambrian Dunderberg Shale. Cominco and Alta also explored the western flank of the mountain, but the mineralized drill intercepts were unoxidized and not amenable to heap leaching. Pilot Gold (USA) Inc. acquired the Kinsley Project in 2011, noting geological similarities to the Long Canyon deposit. The Kinsley Range is underlain primarily by platformal limestone, dolostone and shale ranging from Middle Cambrian through Ordovician. The south end of the range is intruded by a small Tertiary stock with a hornfelsed aureole. Tertiary volcanic rocks are exposed in pediment areas on either side of the range. Strata were subject to ductile, contractional deformation in mid-Mesozoic time as well as Tertiary low- and high-angle normal faulting associated with regional extension. There are low-angle faults bounding most major lithological breaks, locally cutting out entire formations. High-angle faults strike north to northeast and are cut by northwest-trending faults. High-grade, sedimentary rock-hosted gold mineralization at the Western Flank Zone was discovered in late 2013 in core hole PK91CA, which returned 8.53 g/t Au over 36.6m. Pilot Gold targeted the intersection of a NNE alignment of historic shallow drill intercepts along the western flank of the range and the extension of the NW alignment of the historic pits, in a location 500 m northwest of the mine. Subsequent core and RC drilling in 2014 yielded additional high grade mineralization in the Western Flank Zone and tested other targets in this same stratigraphic horizon. The Western Flank high-grade zone is hosted primarily within the Secret Canyon Shale, comprising the Clarks Spring (thin-bedded limestone and shale) and the lower shale members, 100 to 200 m below historically-mined mineralization in the Dunderberg shale. The zone exhibits some control by NW- and NNE- striking, moderate- to high-angle structures. Highest gold grades are associated with variable silicification, very fine-grained disseminated and shear-hosted arsenical pyrite and late fracture-controlled stibnite, with local development of collapse breccia. The zone is locally strongly oxidized to limonite, hematite and jarosite, with minor scorodite. The Western Flank discovery demonstrates the potential for high-grade mineralization in newly-recognized stratigraphic units beneath the historic mine area. The discovery reinforces the potential for sediment-hosted gold systems in the eastern Great Basin to host high-grade gold mineralization in sedimentary units that remain largely unexplored to date.