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Geochemical data for stream water and stream sediment samples from the northeast part of the Tanacross quadrangle, Alaska

February 2, 2022

This data release is part of a study designed to test geochemical methods that best delineate known mineral deposits in the northeast part of the Tanacross 1 x 3 quadrangle, within the Yukon-Tanana Upland region, Alaska. The total area sampled is about 3,200 km2. Extensive tundra cover and patchy spruce/alder vegetation and very limited outcrop exposure characterize the area. Soils and stream sediments contain mixtures of weathered bedrock, sand derived from dunes developed during the Pleistocene, and volcanic ash deposits from the 1.2 Ky eruption of the nearby Mount Churchill volcano. Several mineral deposits are known in the area, including the Late Cretaceous to earliest Tertiary porphyry Cu (+/-Mo-Au) deposits at Taurus, Bluff, and Oreo; and poorly understood epithermal(?) Cu-Au (+/- Pb-Zn) deposits at Pika, Fishhook, and Pushbush. Stream water and sediment samples were collected near these occurrences, as well as in surrounding areas, to determine methods that most effectively enhance geochemical signals related to mineralization. Sediment samples were collected during two sampling campaigns (2017 and 2018). Each sample was dried, homogenized, and split into multiple aliquots. One aliquot of sediment was subsequently sieved to recover the minus-80 mesh portion of the sample, whereas a second was sieved to recover the minus-230 mesh portion of the sample. Both aliquots were analyzed by three techniques, all of which included ICP-OES/ICP-MS analysis following (1) sodium peroxide fusion, 2) leaching by aqua regia; and 3) leaching by cold hydroxylamine-HCL. Stream water samples were collected from select sites in August 2018 and analyzed for cation and anion concentrations using high-resolution ICP-MS for cations and Ion Chromatography (IC) for anions.