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At least 199 records · Page 11Linked to original sources
USGS1980

Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the McCarthy Quadrangle, Alaska

These summaries of data on metallic and selected nonmetallic mineral occurrences and lists of selected references to .them in Geological Survey, U.S. Bureau of Mines, and State of Alaska Division of Geological and Geophysical Surveys (and predecessor State and Territorial agencies) reports and maps and a very.few journal articles are designed to aid in library research on the mineral resources of the McCarthy quadrangle, Alaska. The references listed are selected in the sense that mainly statistical reports such as the annual Minerals Yearbook of the U.S. Bureau of Mines and many annual and biennial reports of the Alaska Division of Geological and Geophysical Surveys and its predecessor agencies are not included. Also not included are data on claims about which little more than their locations is known (for example, localities 126- 130 in MacKevett and Holloway, 1977 (OF 77-169A). These omissions should not be interpreted as a judgement that the claims are not on valid mineral occurrences, but only chat there are insufficient data to describe any mineral deposits that might be present. Geochemical anomalies determined by analyses of rock and stream-sediment samples in which no metallic mineral was indentified are also omitted.

Alaska↗
USGS2009

Mesozoic magmatism and base-metal mineralization in the Fortymile mining district, eastern Alaska — Initial results of petrographic, geochemical, and isotopic studies in the Mount Veta area

We present here the initial results of a petrographic, geochemical, and isotopic study of Mesozoic intrusive rocks and spatially associated Zn-Pb-Ag-Cu-Au prospects in the Fortymile mining district in the southern Eagle quadrangle, Alaska. Analyzed samples include mineralized and unmineralized drill core from 2006 and 2007 exploration by Full Metal Minerals, USA, Inc., at the Little Whiteman (LWM) and Fish prospects, and other mineralized and plutonic samples collected within the mining district is part of the USGS study. Three new ion microprobe U-Pb zircon ages are: 210 ± 3 Ma for quartz diorite from LWM, 187 ± 3 Ma for quartz monzonite from Fish, and 70.5 ± 1.1 Ma for altered rhyolite porphyry from Fish. We also present 11 published and unpublished Mesozoic thermal ionization mass spectrometric U-Pb zircon and titanite ages and whole-rock geochemical data for the Mesozoic plutonic rocks. Late Triassic and Early Jurassic plutons generally have intermediate compositions and are slightly foliated, consistent with synkinematic intrusion. Several Early Jurassic plutons contain magmatic epidote, indicating emplacement of the host plutons at mesozonal crustal depths of greater than 15 km. Trace-element geochemical data indicate an arc origin for the granitoids, with an increase in the crustal component with time. Preliminary study of drill core from the LWM Zn-Pb-Cu-Ag prospect supports a carbonate-replacement model of mineralization. LWM massive sulfides consist of sphalerite, galena, and minor pyrite and chalcopyrite, in a gangue of calcite and lesser quartz; silver resides in Sb-As-Ag sulfosalts and pyrargyrite, and probably in submicroscopic inclusions within galena. Whole-rock analyses of LWM drill cores also show elevated In, an important metal in high-technology products. Hypogene mineralized rocks at Fish, below the secondary Zn-rich zone, are associated with a carbonate host and also may be of replacement origin, or alternatively, may be a magnetite-bearing Zn skarn. Cu-Zn-Pb-Ag-Au showings at the Oscar pros-pect occur in marble-hosted magnetite and pyrrhotite skarn that is spatially related to the stocks, dikes, and sills of the Early Jurassic syenite of Mount Veta. Mineralized rocks at the Eva Creek Ag-Zn-Pb-Cu prospect are within 1.5 km of the Mount Veta pluton, which is epidotized and locally altered along its contact with metamorphosed country rock east of the prospect. We report five new sulfide Pb-isotopic analyses from the LWM, Oscar, and Eva Creek prospects and compare these sulfide Pb-isotopic ratios with those for sulfides from nearby deposits and prospects in the Yukon-Tanana Upland and with feldspar Pb-isotopic ratios for Mesozoic plutons in the region. Disparities between the Pb-isotopic ratios for sulfides and igneous feldspars are consistent with a carbonate-replacement model for both the LWM and Eva Creek prospects. The presence in the Fortymile district of base-metal sulfides within both calc-silicate-rich skarns and the calc-silicate-free carbonate replacement deposits may reflect multistage mineralization by magmatic-hydrothermal systems during the emplacement of two or more magmatically unrelated igneous intrusions. Alternatively, all of the mineralized occurrences could be products of one regionally zoned system that formed during the intrusion of a single pluton. In addition to the likely origin of some of the base-metal occurrences by intrusion-related hydrothermal fluids, proximity of the LWM prospect to the northeast-striking, high-angle Kechumstuk Fault suggests that fluid flow along the fault also played an important role during carbonate-replacement mineralization.

Alaska↗
USGS2022

Focus areas for data acquisition for potential domestic resources of 13 critical minerals in the conterminous United States and Puerto Rico — Antimony, barite, beryllium, chromium, fluorspar, hafnium, helium, magnesium, manganese, potash, uranium, vanadium, and zirconium

The Earth Mapping Resources Initiative (Earth MRI) is conducted in phases to identify areas for acquiring new geologic framework data to identify potential domestic resources of the 35 mineral materials designated as critical minerals for the United States. This report describes the data sources and summary results for 13 critical minerals evaluated in the conterminous United States and Puerto Rico during phase 3 of the study (antimony, barite, beryllium, chromium, fluorspar, hafnium, helium, magnesium, manganese, potash, uranium, vanadium, and zirconium). Phases 1 and 2 of the Earth MRI addressed aluminum, cobalt, graphite, lithium, niobium, platinum-group elements (PGEs), rare earth elements (REEs), tantalum, tin, titanium, and tungsten. Critical minerals in Alaska are covered in a separate report. No focus areas for phase 3 critical minerals are delineated for Hawaii. The geologic, geochemical, topographic, and geophysical mapping provided by the Earth MRI documents geologic features that reflect the extent of individual mineral systems and provides information about critical mineral deposits that may not have been previously considered. The mineral-systems approach links critical mineral commodities to deposit types that represent the manifestations of large mineral systems. Each of the 13 critical mineral commodities for phase 3 of the Earth MRI is discussed in terms of its importance to the Nation’s economy, modes of occurrence, mineral systems, and deposit types, and is accompanied by maps and tables listing examples of focus areas in the conterminous United States and Puerto Rico. Examples of important mineral systems for this group of 13 critical minerals include basin brine path systems for barite and fluorspar, Carlin-type systems and Coeur d’Alene systems for antimony, chemical weathering and volcanogenic seafloor systems for manganese, Climax-type systems for beryllium, mafic magmatic systems for chromium, marine evaporite systems for potash and magnesium, meteoric recharge systems for uranium, petroleum systems for helium, and placer systems for zirconium and hafnium.

Open-File Report↗
USGS2006

Major- and trace-element concentrations in rock samples collected in 2004 from the Taylor Mountains 1:250,000-scale quadrangle, Alaska

The Kuskokwim mineral belt of Bundtzen and Miller (1997) forms an important metallogenic region in southwestern Alaska that has yielded more than 3.22 million ounces of gold and 400,000 ounces of silver. Precious-metal and related deposits in this region associated with Late Cretaceous to early Tertiary igneous complexes extend into the Taylor Mountains 1:250,000-scale quadrangle. The U.S. Geological Survey is conducting geologic mapping and a mineral resource assessment of this area that will provide a better understanding of the geologic framework, regional geochemistry, and may provide targets for mineral exploration and development. During the 2004 field season 137 rock samples were collected for a variety of purposes. The 4 digital files accompanying this report reflect the type of analysis performed and its intended purpose and are available for download as an Excel workbook, comma delimited format (*.csv), dBase 4 files (*.dbf) or as point coverages in ArcInfo interchange format (*.e00). Data values are provided in percent, pct (1gram per 100grams), or parts per million, ppm (1gram per 1,000,000grams) per the column heading in the table. All samples were analyzed for a suite of 42 trace-elements (icp42.*) to provide data for use in geochemical exploration as well as some baseline data. Selected samples were analyzed by additional methods; 104 targeted geochemical exploration samples were analyzed for gold, arsenic, and mercury (auashg.*); 21 of these samples were also analyzed to obtain concentrations of 10 loosely bound metals (icp10.*); 33 rock samples were analyzed for major element oxides to support the regional mapping program (reg.*), of which 28 sedimentary rock samples were also analyzed for total carbon, and carbonate carbon.

Open-File Report↗
USGS1980

Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Talkeetna Mountains Quadrangle, Alaska

These summaries of data on metallic and selected nonmetallic mineral occurrences and lists of selected references to them in Geological Survey, U.S. Bureau of Mines, and State of Alaska Division of Geological and Geophysical Surveys (and predecessor State agencies) reports and maps are designed to aid in library research on the mineral resources of the Talkeetna Mountains quadrangle, Alaska. The references listed are selected in the sense that mainly statistical reports such as the annual Minerals Yearbook of the U.S. Bureau of Mines and many annual and biennial reports of the Alaska Division of Geological and Geophysical Surveys and its predecessor agencies are not included. Also not included are data on many claims about which little more than their locations is known (for example, localities 3 and 6 in Csejtey and Miller, 1978 (OF 78- 558B)). These omissions should not be interpreted as a judgement that the claims are not on valid mineral occurrences, but only that there are insufficient data to describe any mineral deposit that might be present. Geochemical anomalies determined by analyses of rock and stream—sediment samples in which no metallic mineral was identified are also omitted. This report is divided into three parts: a section made up of summaries of data and reference lists arranged alphabetically by occurrence name; a second section that lists synonyms for names in the first section and the names of owners and operators of mines and prospects; and a final section that lists alphabetically by author all references mentioned in the first section and in these introductory paragraphs.

Alaska↗
USGS1976

Maps showing mineralogical and geochemical data for heavy-mineral concentrates in the Tanacross quadrangle, Alaska

This series of maps showing the following data for heavy mineral concentrates: distribution and abundance of selected ore-related minerals, distribution and abundance of copper in the magnetic fraction, and distribution and abundance of lead, copper, tin, beryllium, tungsten and bismuth in the nonmagnetic fraction. The data are plotted on base maps showing generalized geology, base metal prospects in the Yukon-Tanana Upland, and the drainage pattern. The distribution and abundance of ore-related minerals (fig. A) were obtained by microscopic examination of the heavy-mineral concentrates. The number of mineral grains observed is shown in the map explanation. Figures B through H are geochemical maps showing the distribution and abundance of metals as determined by six-step semi-quantitative emission spectrography. The geochemical map symbols show sample sites and the actual values for the element in the sample as determined by spectrography. An explanation of sampling, preparation, and analytical procedure is given in Circular 734 which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in an open-file report (O'Leary and others, 1976).

Alaska↗
USGS1974

Selected U.S. Bureau of Mines reports on Alaska indexed by quadrangle

Most U.S. Bureau of Mines reports on the geology and mineral resources of Alaska that were published or placed in open files through April 30, 1974, are listed by the quadrangles (scale 1:250,000) into which Alaska has been divided for topographic mapping (p. 2). References to reports that deal with Alaska as a whole and cannot be readily assigned to individual quadrangles or deal with many scattered parts of the state are listed under ALASKA - GENERAL, which appears before the alphabetically arranged quadrangle listings. References to the Minerals Yearbook, published annually, are not included as this periodical contains mainly statistical data. Also omitted are reports on mining, milling, and metallurgical practices; compilations of coal, oil, and gas analyses unless data on geological occurrences are also given; and reports on permissible explosives, health, and safety. This index is the second in a planned series of specialized lists, arranged by quadrangle, that will facilitate library research on the geology and mineral resources of Alaska. The first in the series is "Geological Survey open-file reports on Alaska indexed by quadrangle," by Edward H. Cobb, which was released as open-file report 74-7 on May 16, 1974.

Alaska↗
USGS1984

Heavy minerals in surficial sediments from lower Cook Inlet, Alaska

Amphiboles, orthopyroxenes, and clinopyroxenes dominate the heavy mineral suite of surficial sediments in lower Cook Inlet, Alaska. Sources for these sediments include the igneous arc terrane of the northeast Alaska Range, reworked intrabasinal sediments, and local drainages in lower Cook Inlet. The distribution of these deposits is a reflection of both the tidal currents and the prevailing southerly net movement from the head of Cook Inlet. The heavy mineral studies concur with similar findings from gravel analyses, clay mineral investigations, and quartz microtexture observations. ?? 1984 Springer-Verlag New York Inc.

Geo-Marine Letters↗
USGS2011

Alaska Geochemical Database (AGDB)-Geochemical data for rock, sediment, soil, mineral, and concentrate sample media

The Alaska Geochemical Database (AGDB) was created and designed to compile and integrate geochemical data from Alaska in order to facilitate geologic mapping, petrologic studies, mineral resource assessments, definition of geochemical baseline values and statistics, environmental impact assessments, and studies in medical geology. This Microsoft Access database serves as a data archive in support of present and future Alaskan geologic and geochemical projects, and contains data tables describing historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 85 laboratory and field analytical methods on 264,095 rock, sediment, soil, mineral and heavy-mineral concentrate samples. Most samples were collected by U.S. Geological Survey (USGS) personnel and analyzed in USGS laboratories or, under contracts, in commercial analytical laboratories. These data represent analyses of samples collected as part of various USGS programs and projects from 1962 to 2009. In addition, mineralogical data from 18,138 nonmagnetic heavy mineral concentrate samples are included in this database. The AGDB includes historical geochemical data originally archived in the USGS Rock Analysis Storage System (RASS) database, used from the mid-1960s through the late 1980s and the USGS PLUTO database used from the mid-1970s through the mid-1990s. All of these data are currently maintained in the Oracle-based National Geochemical Database (NGDB). Retrievals from the NGDB were used to generate most of the AGDB data set. These data were checked for accuracy regarding sample location, sample media type, and analytical methods used. This arduous process of reviewing, verifying and, where necessary, editing all USGS geochemical data resulted in a significantly improved Alaska geochemical dataset. USGS data that were not previously in the NGDB because the data predate the earliest USGS geochemical databases, or were once excluded for programmatic reasons, are included here in the AGDB and will be added to the NGDB. The AGDB data provided here are the most accurate and complete to date, and should be useful for a wide variety of geochemical studies. The AGDB data provided in the linked database may be updated or changed periodically. The data on the DVD and in the data downloads provided with this report are current as of date of publication.

Data Series↗
USGS2021

Bedrock gorge incision via anthropogenic meander cutoff

Bedrock river-gorge incision represents a fundamental landscape-shaping process, but a dearth of observational data at >10 yr timescales impedes understanding of gorge formation. I quantify 10 2 yr rates and processes of gorge incision using historical records, field observations, and topographic and image analysis of a human-caused bedrock meander cutoff along the North Fork Fortymile River in Alaska (USA). Miners cut off the meander in 1900 CE, abruptly lowering local base level by 6 m and forcing narrowing and steepening of the channel across a knickpoint that rapidly incised upstream. Tectonic quiescence, consistent rock erosivity, and low millennial erosion rates provide ideal boundary conditions for this 10 2 yr gorge-formation experiment. Initial fast knickpoint propagation (23 m/yr; 1900–1903 CE) slowed (4 m/yr; 1903–1981 CE) to diffusion (1981–2019 CE) as knickpoint slope decreased, yielding an ~350-m-long, 6-m-deep gorge within the pre–1900 CE channel. Today, diffusion dominates incision of a 500-m-long knickzone upstream of the gorge, where sediment transport likely limits ongoing adjustments to the anthropogenic cutoff. Results elucidate channel width, slope, discharge, and sediment dynamics consistent with a gradual transition from detachment- to transport-limited incision in fluvial adjustment to local base-level lowering.

Alaska↗