Geochemical data from samples collected in 2023 for the Chena and Mount Harper projects, Big Delta, Circle, Fairbanks, and Eagle quadrangles, Alaska

Description

Geochemical data from samples collected in 2023 for the Chena and Mount Harper projects, Big Delta, Circle, Fairbanks, and Eagle quadrangles, Alaska, Raw Data File 2024-2, presents whole-rock and major- and trace-element geochemistry of rock samples collected to support 1:100,000-scale bedrock geologic mapping of ~5,750 mi2 (~15,000 km2) in portions of the Big Delta and Circle quadrangles and parts of the Fairbanks and Eagle quadrangles, Alaska. These samples were collected to support the Chena and Mount Harper/Richardson mapping projects, both of which are integral parts of the U.S. Geological Survey's Earth Mapping Resource Initiative (USGS Earth MRI) program. The aim of Earth MRI is to update the nation's surface and subsurface mapping to improve the knowledge of the country's overall geologic framework, with a specific focus on identifying areas that may contain undiscovered critical mineral resources. This raw data file (RDF) includes major oxide and trace element geochemistry of metamorphic and igneous rocks and potentially mineralized rocks sampled from the Chena and Mount Harper/Richardson project areas. Station location and field rock descriptions for the samples can be found in Gavel and others (2023). These geochemical analyses will further our understanding of potential mineral resources in the area, help distinguish between igneous and sedimentary protoliths in metamorphic rocks, and be used to characterize the Mesozoic and Cenozoic magmatic events. The regional geology is composed of structurally bound assemblages of polydeformed Paleozoic metasedimentary and metaigneous rocks ranging from lower greenschist to upper amphibolite facies. These rocks are structurally overlain by allochthonous oceanic mafic and ultramafic rocks of the Seventymile terrane at Nail Ridge. The metamorphic sequences are intruded by Cretaceous to Paleocene plutons. The Chena and Mount Harper/Richardson projects surround areas of historical mining activity, current production, and future potential mineral resource development. Granitic plutons were emplaced during multiple magmatic pulses in the mid-Cretaceous, spanning 115-90 Ma. This period of magmatism and deformation is associated with gold (+/- tellurium, bismuth, antimony, and arsenic) mineralization at the Pogo Mine and nearby prospects along the Pogo trend, including West Pogo, East Pogo, and Tibbs. Some latest Cretaceous to early Paleogene magmatism is associated with tungsten mineralization (Big Windy and Furs W skarn prospects). Tin- and rare earth element (REE)-bearing granites and peralkaline intrusions exist within the field areas and in historical and modern placer gold mines. 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/10.14509/31123.

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