Geologic map of the Tok River area, Tanacross A-5 and A-6 quadrangles, eastern Alaska Range, Alaska

Preliminary Interpretive Report PIR 2017-3, Geologic map of the Tok River area, Tanacross A-5 and A-6 quadrangles, eastern Alaska Range, Alaska, provides 1:63,360-scale geologic mapping of the bedrock units and surficial deposits in the Tok River area, Tanacross A-5 and A-6 quadrangles, eastern Alaska Range, Alaska. The Tok River geologic mapping project is part of a multi-year effort focusing on improving the publicly available geological and geochemical data and assessing the mineral potential of the Tanacross quadrangle. The project focused on detailed mapping, identification, sampling, and characterization of Devonian-Mississippian metamorphic rocks, Triassic and Cretaceous intrusions, surficial geology, and modern geochemical characterizations of skarn, vein, and volcanogenic massive sulfide (VMS) hosted mineralization. The DGGS Mineral Resources section spent 321 person-days in the field in 2015 and 2016 to conduct approximately 540 square miles of 1:63,360-scale geologic mapping and sampling in the Tok River area of central Alaska. The new geologic map improves understanding of the area's geology, structural history, and mineral potential. This area includes exposures of Devonian-Mississippian metamorphic rocks, metamorphosed Triassic gabbroic intrusions, and Cretaceous granodiorite intrusions and basaltic andesite lava flows. The area lies between the Delta mineral belt to the west, which has been the focus of exploration into VMS, and skarn deposits of the Tetlin project to the east. The area also contains numerous inactive and possibly active faults and multiple stages of deformation and magmatism, which are critical for understanding the geologic history of the eastern Alaska Range. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/29722.

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Organization: State of Alaska