Mineral Resources Section personnel from the Alaska Division of Geological & Geophysical Surveys (DGGS) carried out a geologic field survey, including mapping and sampling, 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, Alaska, from June 16 through July 18, 2008. The fieldwork provides basic 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. Specifically, this work provides geologic context for geophysical surveys conducted in 2006. Interpretation and synthesis of this data has been presented in professional and trade meetings. This report and associated geologic map data are preliminary, have not undergone rigorous peer review, and will be superseded by a subsequent Report of Investigations map and report that will be issued later in 2016. The objective of the eastern Bonnifield project is to produce a 1:50,000-scale geologic map to foster a better understanding of the area's geology and mineral potential. Although DGGS concentrated on mapping the Paleozoic metamorphic rocks that host the volcanogenic massive sulfide deposits (VMS) and Mesozoic igneous rocks associated with Au-Ag-As-Sb veins, we also studied the Tertiary sedimentary section, which could contain coal resources. The geologic map data are available in digital format as ESRI shapefiles.

During the 2017 field season, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted geologic mapping and sampling of part of the Richardson mining district southeast of Fairbanks, Alaska. The project area is about 30 miles west of the Pogo gold mine and covers gold exploration activity at the Montecristo and Uncle Sam properties. This work aims to build an improved understanding of the area's geology and controls on gold mineralization for purposes of exploration targeting and mineral-resource assessment. The 260-square-mile map area lies between the Salcha River and Shaw Creek and is bounded by the Trans-Alaska Pipeline access road to the southwest. The area is characterized by forested, moderate-relief hills blanketed by vegetation, loess, and locally, sand dunes. Rock outcrop is less than one percent; consequently, the map interpretation relies heavily on the DGGS East Richardson airborne magnetic and electromagnetic survey as well as rocks collected from pits dug into rocky colluvial deposits below surficial loess or sand. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/30676.

Bedrock geologic map of the northern Fairbanks mining district, Circle Quadrangle, Alaska, Preliminary Interpretive Report 2022-2, presents whole-rock trace-element geochemistry of Nb, Rb, Sr, Y, Zr for samples collected to support geologic mapping and mineral exploration in the northern Fairbanks mining district. The analytical data tables associated with this report are available through the Alaska Geochemistry database (https://maps.dggs.alaska.gov/geochem). For a direct link to this data release, see http://doi.org/10.14509/30891.

Geologic map of the Fairbanks D-1 SW Quadrangle, Alaska, Miscellaneous Investigations Series Map 949, presents the findings of a geologic investigation into bedrock and surficial deposits within the Fairbanks D-1 quadrangle, a 60-square-mile region in central Alaska. The area encompasses parts of the Fairbanks urban area, including the community of North Pole. With a rich history of gold mining, the region continues to be actively mined for gravel and other geologic materials. A thick blanket of Quaternary-age loess, ranging from a few inches to several hundred feet, covers nearly the entire quadrangle. Urban developers face ongoing challenges related to groundwater contamination, thermokarst formation, and issues stemming from land subsidence. The map is designed to provide broad guidelines to assist city planners and land-use decision-makers in managing development within the area. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: https://dggs.alaska.gov/pubs/12954.

This map illustrates potential near-surface sources of geologic materials that may be useful for construction and other purposes. Field observations indicate that each geologic unit (for example, flood-plain alluvium) has a definite composition or range of composition. Therefore, the presence of material type is interpreted from the distribution of geologic units (Newberry and others, 1996 - PDF96-16). Assignment of Unified Soil Classes (Wagner, 1957) is based on visual observation and interpretation of the likely distribution of the materials; no grain-size analyses were performed. Descriptions of unconsolidated deposits are modified from Pewe and Bel (1975a-d) and Pewe and Bell (1976). This map is generalized and is not intended to show exact locations of specific materials.

Geologic map of the McGrath D-6 Quadrangle, Alaska, Professional Report 79, provides 1:63,360-scale geologic mapping of the McGrath D-6 Quadrangle, which lies on the eastern edge of the Kuskokwim Mountains, a maturely dissected upland of accordant rounded ridges and broad lowlands. Two highlands, the Candle Hills and Takotna Mountain, are surrounded by sediment-filled troughs of the Takotna, Tatalina, and Kuskokwim River valleys. Elevations range from 300 to 2,600 ft. This report is the result of 40 man-days of reconnaissance geologic mapping in 1977, 1978, and 1982. Bedrock exposures were mapped on foot and by boat. Four-fifths of the quadrangle is covered by Quaternary deposits, which have been subdivided on the basis of a photo-geologic reconnaissance and limited field checking. The report also includes detailed geologic, structural, stratigraphic, and geochronologic data. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/2253.

The Mineral Resources section of the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted bedrock geologic mapping of a 4,800-sq-km (1,860-sq-mi) area of eastern Interior Alaska, including Mount Fairplay and the Ladue River drainage. The area lies north of the Alaska Highway and is approximately 65 km (40 mi) east of Tok, Alaska; it runs west from the Alaska-Yukon border to encompass the Taylor Highway. DGGS and the U.S. Geological Survey (USGS) staff identified this area as having the potential to host deposits of critical minerals, including rare earth elements (REE), uranium, niobium, zirconium, tin, tungsten, bismuth, and rhenium, as well as conventional mineral resources including gold, copper, molybdenum, lead, zinc, and silver. Most of the known mineralization in the area is related to Cretaceous-Paleogene magmatism, which spans a broad diversity of compositions and ranges in scale from batholiths to shallowly emplaced dikes to volcanic rocks. The igneous rocks intrude a composite metamorphic province that includes both parautochthonous North America and components of the allochthonous Yukon Tanana Terrane, now juxtaposed against one another by Jurassic-Cretaceous low-angle faults and subsequently disrupted by multiple generations of Cretaceous-Cenozoic high-angle faults. Our map interpretation relies on observations of outcrop, subcrop, and float, and we make extensive use of airborne magnetic (Emond and others, 2015) and magnetic-electromagnetic surveys for interpolation between field stations. Our mapping of high-angle faults relies on tilt-derivative processing of aeromagnetic data, low resistivity anomalies in electromagnetic surveys, photo and topographic lineaments, and lithologic discontinuities between ridges. Rock names were assigned based on field and petrographic observations, modal-mineral percentages, and interpretations of geochemical data. Age determinations and interpretation of cross-cutting relationships were facilitated by 40Ar/39Ar and Zircon U-Pb geochronologic analysis. The complete report, geodatabase, and ESRI fonts and style files are available from the DGGS website: http://doi.org/10.14509/30735.

This data file presents 40Ar/39Ar step-heating geochronology results for a granite sample from the Livengood mining district. The Livengood area is a historically productive placer mining area approximately 80 road miles north of Fairbanks, Alaska. This data is a component of a geologic map and accompanying report that synthesizes recently collected and previously published agency and industry geologic data in a 1:50,000-scale comprehensive geologic map to build a better understanding of the geology and mineral-resource potential of the Livengood area.