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During the 2023 field season, geologists from the Alaska Division of Geological & Geophysical Surveys conducted bedrock geologic mapping in the Big Delta and Circle quadrangles in Alaska. The project areas are of interest for potential mineral resource development, including gold and copper deposits. This report provides field station locations, rock descriptions, and magnetic susceptibility measurements. The data is available for download from the DGGS website. The project aims to produce accurate geologic maps to support mineral resource exploration in eastern Interior Alaska. [Extracted from the article]

The Tok River area (Tanacross A-5 and A-6 quadrangles) of the eastern Alaska Range hosts a variety of ages and styles of mineralization, including stratabound basemetal sulfide, intrusion-related gold-copper-silver, and structurally controlled gold. Stratabound base-metal (Zn-Pb-Cu-Ag-Au) sulfide prospects occur in the Tanacross A-6 Quadrangle, where they are known in part as the Eagle trend. Mineralization is hosted by thin marble beds within a metamorphic package dominated by siliciclastic and rare volcanic protoliths. Sulfide minerals include sphalerite, galena, chalcopyrite, pyrrhotite, and pyrite; associated minerals include calcite, ankerite, siderite, albite, phengite, chlorite, ferro-actinolite, stilpnomelane, Fe-clinopyroxene, Ca-Mn garnet, ilvaite, and barite. Mineral assemblages, compositions, and textures indicate that base-metal sulfide mineralization experienced Permian through Jurassic regional metamorphism, and Pb-isotopic ratios are closely similar to those of Devonian to Mississippian syngenetic deposits of Interior Alaska. We interpret the Eagle trend to be a continuation of the PP-LZ trend of the Delta mineral belt, and that the Tok River area prospects are most similar to sedimentary-exhalative (SEDEX)-type systems. The Hona prospect comprises Au-Cu-Ag mineralization developed in association with a multiphase hypabyssal granodiorite stock of Late Cretaceous (ca. 75 Ma) age. Mineralization occurs with disseminated pyrrhotite, chalcopyrite, trace molybdenite, and secondary biotite within the intrusion, and with disseminated and veinlet-hosted pyrite and chalcopyrite in adjacent metamorphic rocks. Silicification, sodic, and argillic alteration occur locally, but well-developed sericitic alteration is lacking. The prospect is similar in age to the nearby Peak gold skarn and is associated with intrusions of similar composition. The geochemical signature of Hona mineralization (Au-Cu-Ag-As-Bi-Te) is similar to that of the Peak skarn and distinct from the coeval Taurus Cu-Mo-Au porphyry system. Structurally controlled gold prospects of the White Gold trend appear to have formed well after mid-Cretaceous metamorphic cooling. Mafic and felsic dikes of likely Paleogene age occur locally with structurally controlled gold mineralization and are both pre-/syn- and post-mineralization in timing. Advanced argillic alteration affects Au-As-mineralized dikes as well as mineralized country rock; such alteration reflects highly acidic hydrothermal fluids and is inconsistent with an orogenic gold deposit model. If the White Gold prospects were emplaced during the Paleocene, they are similar in age and style to the Hajdukovich property near Delta Junction and may be genetically linked to ca. 55 Ma extensional tectonics and magmatism. [ABSTRACT FROM AUTHOR]

The article discusses the Division of Geological & Geophysical Surveys (DGGS) geochemical sampling project and geologic mapping in the Tok River area, Tanacross A-5 and A-6 quadrangles, Alaska in 2016. Topics including rock samples collection such as mineralized rock and igneous rock for trace-element geochemistry purposes, rock samples preparation by ALS Geochemistry, and sample type analysis using flux digestion and elemental tests.

We report U-Pb zircon geochronology results for one metavolcanic and one metaplutonic rock sample from the Mount Hayes A-6 Quadrangle of central Alaska. These samples are representative of rock units assigned to the Clearwater terrane of Jones and others (1987), a sequence of greenschist-grade metavolcanic and metasedimentary rocks of poorly constrained age and tectonic origin. Our results indicate a crystallization age of 277.33 ± 11.84 Ma for a felsic metavolcanic rock, and a 268.05 ± 11.64 Ma crystallization age for a granitic metaplutonic unit intruding the former. [ABSTRACT FROM AUTHOR]

The article presents results of a preliminary report conducted by the State of Alaska, Department of Natural Resources, which explores the geological and geophysical survey on mineral occurrences at the Tok River Area in Alaska. A brief overview on the geophysical structure of the area is mentioned. It also notes on the Kennecott Exploration on surface exploration and drilling in 1997 and 1998.

An industry report of the mineral industry in Alaska is presented from publisher Alaska Division of Geological & Geophysical Surveys (DGGS), with topics including government revenue from the state's mineral industry, primary metals production from 1880-2015, and the Red Dog Mine.

The article offers information on a report by the Department of Natural Resources of Alaska on data of trace elements found in rocks of Wrangellia mineral assessment area in Alaska. Topics discussed include determination of rare-earth element in rock samples by inductively-coupled plasma-mass spectroscopy, analysis of palladium by inductively coupled plasma mass spectrometry (ICP-MS), and analysis of minor oxides by lithium metaborate fusion digestion.

The article offers information on the symbols used in map units. Topics discussed include use of Qa to describe undifferentiated floodplain alluvial deposits, use of Trrp to show high silica rhyolite, use of Kg indicates granite rocks and, use of KJmf to show metamorphosed and interbedded sandstone in the area.

This report presents 40AR/39AR step-heating geochronology results for igneous and metamorphic rocks from the Alaska Division of Geological & Geophysical Surveys' (DGGS) Talkeetna Mountains C-4 Quadrangle and Adjoining Areas geologic mapping project. The U.S. Geological Survey (USGS) National Cooperative Geologic Mapping Program partially funded work by DGGS to map approximately 450 mi2 of the Talkeetna Mountains region of central Alaska at 1:50,000 scale. This area contains significant exposures of Late Triassic mafic volcanics and gabbro sills that have been the focus of region-wide exploration for the Strategic and Critical platinum-group elements (PGEs). The area also exposes numerous inactive and possibly active faults that project through the area of the proposed Susitna-Watana hydroelectric dam and reservoir. Because this area was poorly mapped at a reconnaissance scale of 1:250,000, a team of eight DGGS geologists spent 42 days in the field to produce a new geologic map and a greatly improved understanding of the geology, structural history, and mineral potential of the area. Hornblende-bearing gabbro returned a Late Triassic crystallization age consistent with regional results for Nikolai Greenstone-related magmatism. We determined Early Jurassic metamorphic ages for hornblende and sericite from two samples of upper greenschist to amphibolite grade metavolcanic rocks. Our results indicate that a granodiorite pluton intruding Wrangellia in the study area has a Middle Jurassic age consistent with the Talkeetna Arc, indicating that the Wrangellia and Peninsular terranes were joined at that time. Cretaceous plutons and porphyry intrusions in the map area can be divided into two types: reduced granitic to felsic porphyry intrusions with latest Cretaceous ages, and an earlier, oxidized type with early Late Cretaceous ages. This observation corresponds to similar patterns in magmatism in the western Alaska Range, and may indicate geological potential for similar style intrusive-related gold, copper, and molybdenum mineralization in the study area. Finally, we obtained Eocene ages for andesite and rhyolite; these ages constrain the timing of displacement on some of the faults in the map area. [ABSTRACT FROM AUTHOR]

The article discusses the exploration for rare-earth elements by the Alaska Division of Geological & Geophysical Surveys at the Talkeetna Mountains C-4, C-3, and B-4 quadrangles off the western Wrangellia terrane. Sample collection and geopositioning for prospective Late Triassic magmatic Ni-Cu-Co-PGE deposits is described. Also included is the analytical methodology for specimen prepared with the PREP-31 package by ALS Minerals group under ISO/IEC 17025-2005 guidelines for trace element test.

This DGGS Raw Data File presents 40Ar/39Ar age dating results from selected mafic to intermediate intrusions encountered during a geological and geochemical resource assessment project in the Gulkana, Healy, Mount Hayes, and Talkeetna Mountains quadrangles. Three intrusions returned mid-Cretaceous crystallization ages, while one olivine gabbro returned a Late Triassic crystallization age. Two altered or metamorphosed samples yielded Late Jurassic and Early Cretaceous ages. Analyses were performed by the University of Alaska Fairbanks Geochronology Laboratory, and results were reported by Paul Layer and Jeff Benowitz. Products included in this data release are: a summary of sample collection methods, the laboratory report, analytical data tables and associated metadata, and plots of the 40Ar/39Ar age spectra, Ca/K and Cl/K ratios. All components of this data release are available on the DGGS website. [ABSTRACT FROM AUTHOR]

The article discusses a survey for rare-earth elements and precious minerals conducted by the Alaska Division of Geological & Geophysical Surveys (DGGS) along Styx River in the Lime Hills C-1 Quadrangle. Plutonic complexes in the area are noted. Collection, preparation and analysis of rock samples are described.

The article discusses the geochemical exploration of mafic intrusions in the Wrangellia terrane and the Talkeetna and Mount Hayes Quadrangles in Alaska. Collection and preparation protocols followed by the Division of Geological & Geophysical Surveys (DGGS) are indicated. Analytical procedures for each type of sample is presented.

The article offers information on a report by the Department of Natural Resources of Alaska on data of trace elements found in rocks of Tok area in Alaska. Topics discussed include testing of rock samples with inductively-coupled plasma-atomic emission spectrometry, analysis of palladium by inductively coupled plasma mass spectrometry (ICP-MS), and determination of rare earth elements by using lithium metaborate fusion digestion.