Geochemical data from samples collected in 2022 for the Mount Harper geologic mapping project, Big Delta, Mount Hayes, and Eagle quadrangles, Alaska

Geochemical data from samples collected in 2022 for the Mount Harper geologic mapping project, Big Delta, Mount Hayes, and Eagle quadrangles, Alaska, Raw Data File 2023-24, presents whole-rock and major- and trace-element geochemistry of rock samples collected to support geologic mapping and mineral exploration in the Mount Harper area of the Melozitna mining district. During the 2022 field season, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted 1:100,000-scale bedrock geologic mapping of ~3,100 mi2 (~8,000 km2) within the Big Delta, Mount Hayes, and Eagle quadrangles. This project aims to produce more detailed and modern geologic maps and supporting datasets to promote mineral resource exploration in eastern Interior Alaska. The project area includes known gold (Au) mineralization, recently explored in the Richardson mining district, including the SAM project and the nearby Democrat Lode and associated prospects, and in the Goodpaster mining district at the LMS and Healy intrusion-related gold prospects. The Mount Harper area hosts a cluster of molybdenum (Mo) and tungsten (W) prospects, including porphyry Mo and W skarn styles, both of which have had industry interest over the decades. Ultramafic rocks occur in the South Fork and Volkmar river drainages; these bodies have an as-yet poorly understood potential to host platinum group elements (PGE), chrome (Cr), cobalt (Co), and nickel (Ni) resources. The DGGS map area includes a section of pre-Mississippian to Permian metasedimentary and metaigneous rocks and Triassic to Paleogene intrusive and volcanic rocks. Major- and trace-element geochemistry for these rocks was analyzed to further our understanding of the resources in the area, including distinguishing between igneous and sedimentary protoliths for metamorphic rocks and characterizing and differentiating Mesozoic and Cenozoic magmatic events in the area. Highlights of this geochemical report include sampling of the Healy and LMS projects and multiple prospects on Mount Harper and elsewhere in the map area. Sample 22Z336, collected south of the Brink prospect, yielded 1.52 ppm Au and 500 ppm W. A few samples collected at the LMS prospect yielded elevated silver (Ag) concentrations (for example, sample 22Z409 yielded up to 12.95 ppm). Additionally, sample 22Z406 yielded 1.48 ppm Au, 7.65 ppm Ag, and 1,787 ppm arsenic (As). Samples collected at Larsen Ridge/Lucky 13 prospect near the top of Mount Harper yielded high Ag and W values. For example, 22Z271 (a massive quartz vein) yielded 18.87 ppm Ag and 1,100 ppm W, 22TJN157 (a skarn) yielded 5.75 ppm Ag, 2,348 ppm copper, 4,422 ppm manganese (Mn), and 600 ppm W, and 22Z270 (a granite) yielded 2,356 ppm Mo and 200 ppm W. The Richardson mining district has been previously sampled by DGGS. This data file is released as a Raw Data File with an open end-user license. The data are available from the DGGS website: http://doi.org/10.14509/31089.

Tags: analyses, analyses and sampling, arsenic, base metals, bedrock, bedrock geology, bluebell creek, copper, dggs, economic geology, exploration, geochemical surveys, geochemistry, geologic, geology, gold, gold hill, granite, grimm creek, igneous, intrusion-hosted, intrusive, lead, lode, major oxides, manganese, melozimoran creek, melozitna mining district, metals, metamorphic, methods, minerals, mining, mississippian, molybdenum, moran creek, nickel, non-metals, paleogene, permian, petrogenesis, platinum, platinum group elements, porphyry, quartz, racine creek, rare earth elements, resource assessment, resources, rocks, silver, skarn, slate creek, spruce creek, tozimoran creek, triassic, tungsten, ultramafic, volcanic, webories creek, wells creek, wrongtrail creek, zinc
Organization: State of Alaska