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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. 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...
The geodatabase for the Charlotte 1 degree × 2 degrees quadrangle by Goldsmith and others (1988) was compiled in the Geologic Map Schema (GeMS). The geologic map extends across four lithotectonic belts of the Piedmont from the Coastal Plain and Wadesboro Triassic basin on the east to the Blue Ridge belt in the vicinity of the Grandfather Mountain window on the west. The Wadesboro Triassic basin contains arkosic sandstone, siltstone and conglomerate unconformably overlain by small inliers of late Cretaceous Coastal Plain sediment of the Middendorf Formation (?). The Blue Ridge, Inner Piedmont, Kings Mountain, Charlotte, and Carolina Slate belts consist of different Mesoproterozoic to Late Paleozoic metamorphosed...
In conjunction with hosting field trips for the Association of American State Geologists 2016 annual meeting in Girdwood, Alaska, Alaska Division of Geological & Geophysical Surveys (DGGS) staff collected rock samples and obtained geochemical analysis from several readily accessible, but relatively unstudied outcrops. Samples were collected from Turnagain Arm (mile 104 Seward Highway), Whittier, Crow Pass, and Panorama Mountain (roughly mile 217 Parks Highway). Mineralized samples from veins and veinlets in granitic rocks from the Crow Pass and Whittier sites contain anomalous levels of gold ranging from 0.129 to 0.650 parts per million (ppm). Although none of the samples are from areas open to mineral entry, geochemical...
This Geologic Map Schema (GeMS) database contains all the geologic map information used to publish the Preliminary Bedrock Geologic Map of the Blythe 30' x 60' Quadrangle, California and Arizona, U.S. Geological Survey Open-File Report 2021-1097. The Blythe 30' x 60' quadrangle in southeastern California and southwestern Arizona displays complex geology that includes Mesozoic contractional deformation, metamorphism, and magmatism and Cenozoic extensional deformation and magmatism. The scope of the present map is limited to bedrock units of Miocene and older age because the younger deposits have not been mapped in sufficient detail across the quadrangle to support a systematic compilation. This geologic map database...
This map geodatabase digitally represents the general distribution of bedrock geologic map units in the Turtle Mountains area, California, as portrayed in Plate 1 of USGS Bulletin 1713-B, Mineral resources of the Turtle Mountains Wilderness Study Area, San Bernardino County, California (1988), https://doi.org/10.3133/b1713B. The map covers parts of the Rice, Turtle Mountains, and Savahia Peak 15’ quadrangles at 1:48,000 scale. Plate 1 is titled Mineral resource potential map of the Turtle Mountains Wilderness Study Area, San Bernardino County, California. The current database represents the geologic map base of Plate 1, but does not include mines, prospects, and mineral-potential evaluations that Plate 1 also portrays....
In conjunction with hosting field trips for the Association of American State Geologists 2016 annual meeting in Girdwood, Alaska, Alaska Division of Geological & Geophysical Surveys (DGGS) staff collected rock samples and obtained geochemical analysis from several readily accessible, but relatively unstudied outcrops. Samples were collected from Turnagain Arm (mile 104 Seward Highway), Whittier, Crow Pass, and Panorama Mountain (roughly mile 217 Parks Highway). Mineralized samples from veins and veinlets in granitic rocks from the Crow Pass and Whittier sites contain anomalous levels of gold ranging from 0.129 to 0.650 parts per million (ppm). Although none of the samples are from areas open to mineral entry, geochemical...
There is a growing demand for commodities (elements, compounds, minerals) used in today's advanced technologies. Critical minerals are usually found in ore deposits that are deemed vital to economic and national security. The National Geochemical Database on Ore Deposits: Legacy data (NGDOD) contains chemistry and geologic information for nearly 30,000 historic ore and ore-related rock samples from mineral deposits and mining districts in the United States. Geochemical data sets from various mineral deposits were submitted by geologists of the "Systems Approach to Critical Minerals Inventory, Research, and Assessment" (SACM) within the U.S. Geological Survey Mineral Resource Program (MRP). The data sets represent...
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