Petrographic observations of rocks collected in the Bonnifield mining district, Fairbanks A-1, Fairbanks A-2, Healy D-1, and Healy D-2 quadrangles, Alaska

Abstract

Mineral Resources Section personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a geologic field mapping survey in the eastern part of the Bonnifield mining district in the Fairbanks A-1 and A-2 and the Healy D-1 and D-2 quadrangles. The map area contains several significant polymetallic sulfide prospects and transects three metamorphic assemblages, which include the Healy Schist, Keevy Peak Formation, and the Totatlanika Schist. The fieldwork (June 16 through July 18, 2008) augments publically available information critical to building an understanding of Alaska's geology and is part of an integrated program of airborne geophysical surveys followed by geologic mapping. This raw data release provides petrographic thin section observations of 264 samples from the East Bonnifield Project rock collection. Project staff examined thin sections to better distinguish rock units, assist with evaluating the structural and stratigraphic relationships among the various lithologies, and to determine suitability for lithogeochemical and geochronological analysis. Observations in the data tables include lithologic classification, texture, mineral crystal structure, and mineral components. Users can access the complete report and digital data from the DGGS website: http://doi.org/10.14509/30171.