Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “The Alaska Miner”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
USGS1982

Digital data base application to porphyry copper mineralization in Alaska; case study summary

The purpose of this report is to summarize the progress in use of digital image analysis techniques in developing a conceptual model for assessing porphyry copper mineral potential. The study area consists of approximately the southern one-half of the 1? by 3? Nabesna quadrangle in east-central Alaska. The digital geologic data base consists of data compiled under the Alaskan Mineral Resource Assessment Program (AMRAP) as well as digital elevation data and Landsat spectral reflectance data from the Multispectral Scanner System. The digital data base used to develop and implement a conceptual model for porphyry-type copper mineralization consisted of 16 original data types and 18 derived data sets formatted in a grid-cell (raster) structure and registered to a map base in the Universal Transverse Mercator (UTM) projection. Minimum curvature and inverse distance squared interpolation techniques were used to generate continuous surfaces from sets of irregularly spaced data points. Processing requirements included: (1) merging or overlaying of data sets, (2) display and color coding of maps and images, (3) univariate and multivariate statistical analyses, and (4) compound overlaying operations. Data sets were merged and processed to create stereoscopic displays of continuous surfaces. The ratio of several data sets were calculated to evaluate relative variations and to enhance the display of surface alteration (gossans). Factor analysis and principal components analysis techniques were used to determine complex relationships and correlations between data sets. The resultant model consists of 10 parameters that identify three areas most likely to contain porphyry copper mineralization; two of these areas are known occurrences of mineralization and the third is not well known. Field studies confirmed that the three areas identified by the model have significant copper potential.

Open-File Report↗
USGS1952

Preliminary summary review of thorium-bearing mineral occurrences in Alaska

Thorium-bearing minerals are known at 47 localities in Alaska. At these localities the thorium occurs as a major constituent or in minor amounts as an impurity in one or more of the following 12 minerals: allanite, columbite, ellsworthite, eschynite, gummite, monazite, orangite, parisite, thorianite, thorite, xenotime, and zircon. In addition other minerals, such as biotite and sphene, are radioactive and may contain thorium. Several unidentified columbate minerals with uranium or thorium and uranium as major constituents have been recognized at some localities. The distribution, by type of deposit, of the 57 thorium occurrences is as follows: lode - 3, lode and placer - 1, granitic rock - 3, granitic rock and related placer - 14, and placer - 26. Of the four lode occurrences only the radioactive veins at Salmon Bay in southeastern Alaska and the contact metamorphic deposit in the Nixon Fork area of central Alaska warrant further consideration, although insufficient data are available to determine whether these two deposits have commercial possibilities. The remaining occurrences of thorium-bearing minerals in Alaska are limited to placer deposits and disseminations of accessory minerals in granitic rocks. In most of these occurrences the thorium-bearing minerals occur in only trace amounts and consequently warrent little further consideration. More data are needed to determine the possibilities of byproduct recovery of thorium-bearing minerals from several of the gold and tin placers.

Alaska↗
USGS1978

Geochemical maps showing the distribution and abundance of gold in stream sediments and of gold and silver in heavy-mineral concentrates in the Seward and Blying Sound quadrangles, Alaska

Reconnaissance geochemical and mineralogical sampling was done in the Seward and Blying Sound quadrangles during 1975 and 1976 as part of the Alaska Mineral Resources Assessment Program (AMRAP). These maps show the distribution and abundance of gold and silver in heavy-mineral concentrates. Stream-sediment and heavy-mineral concentrate samples were collected from active stream channels and locally, from the interface of streambeds with intermediate- to low-tide beaches. Most of the stream sediment is fine- to coarse-grained sand, with a clay-silt fraction in streams discharging from glaciers. Stream sediment samples were air dried and sieved through a 80-mesh (0.2 mm) sieve, and the minus-80 mesh fraction was saved for analysis. A split of each sample was analyzed for gold by a 10 gram atomic-absorption method (Ward and others, 1969). Another split was analyzed for 16 elements by a semiquantitative spectrographic method (Grimes and Marranzino, 1968). The heavy-mineral concentrates were obtained by panning stream sediments in the field to remove most of the light minerals. The panned samples were sieved though a 20-mesh (0.8 mm) screen in the laboratory, and the minus-20 mesh fraction was further separated with bromoform (specific gravity: 2.86) to remove any remaining light-mineral grains. Magnetite and other strongly magnetic heavy minerals were removed from the heavy-mineral fraction by use of a hand magnet. The remaining sample was passed through a Frantz Isodynamic Separator 1 and a nonmagnetic fraction was obtained at a setting of 0.6 amperes. A split of this fraction was pulverized and analyzed for 16 elements including gold and silver by semiquantitative spectrographic method used for analyzing the stream sediment. The remaining split of the nonmagnetic fraction was examined for its mineralogic composition using a binocular microscope and X-ray diffraction. The nonmagnetic concentrates primarily contain muscovite, sphene, zircon, apatite, rutile, and anatase. Ore minerals such as gold, scheelite, minium, and most sulfides are also found in this fraction. Sample sites and gold and silver values (in parts per million) are indicated by symbols as defined in the histograms. The maps show two populations for gold in stream sediments and for gold and silver heavy mineral concentrates. One population consists of generally higher gold and silver values found in samples collected in the sedimentary terrane in the western half of the area. The other population consists of generally lower gold and silver values found in samples collected in areas of sheeted basalt dikes, pillow basalts, and sedimentary terrane in the eastern half of the area. The anomalous silver values found on Knight Island and Latouche Island are associated with chalcopyright- and pyrite-bearing rocks. 1 The use of trade names is for descriptive purposes only and does not constitute endorsement of those products by the U.S. Geological Survey.

Alaska↗
USGS1978

Mineralogical map showing the distribution and abundance of gold, scheelite, chalcopyrite, arsenopyrite, minium, and sapphire corundum in heavy-mineral concentrates in the Seward and Blying Sound quadrangles, Alaska

Reconnaissance geochemical and mineralogical sampling was done in the Seward and Blying Sound quadrangles during 1975 and 1976 as part of the Alaska Mineral Resources Assessment Program (AMRAP). These maps show the distribution and abundance of gold, scheelite, chalcopyrite, arsenopyrite, minium and sapphire corundum in heavy-mineral concentrates. Heavy-mineral concentrate samples were collected at 525 sites from active channels and, locally, from the interface of streambeds with intermediate- to low-tide beaches. The heavy-mineral concentrates were obtained by panning stream sediments in the field to remove most of the light minerals. The panned samples were sieved though a 20-mesh (0.8 mm) screen in the laboratory, and the minus-20 mesh fraction was further separated with bromoform (specific gravity: 2.86) to remove any remaining light-mineral grains. Magnetite and other strongly magnetic heavy minerals were removed from the heavy-mineral fraction by using a hand magnet. The remaining sample was passed through a Frantz Isodynamic Separator 1 and a nonmagnetic fraction was obtained at a setting of 0.6 amperes. A split of this nonmagnetic fraction was examined for its mineralogic content using a binocular microscope and X-ray diffraction. The nonmagnetic concentrates primarily contain muscovite, sphene, zircon, apatite, rutile, and anatase. Small amounts of other minerals such as gold, scheelite, minium, sapphire corundum, and most sulfides will also be found in this fraction. 1 The use of trade names is for descriptive purposes only and does not constitute endorsement of those products by the U.S. Geological Survey.

Alaska↗
USGS1996

Explanation of fields used in the Alaska Resource Data File of mines, prospects, and mineral occurrences in Alaska

Descriptions of mines, prospects, and mineral occurrences in the Alaska Resource Data File (ARDF) are published for individual U.S. Geological Survey 1:250,000 scale quadrangles in Alaska (see accompanying map) and are available for downloading from USGS World Wide Web site: http://www-rnrs-ak.wr.usgs.gov/ardf . These descriptions are divided into a number of fields which describe features of each mine, prospect, or mineral occurrence. These descriptions were complied from published literature and from unpublished reports and data from industry, the U.S. Bureau of Mines, and the U.S. Geological Survey and other sources. Compilation of this database is an ongoing process and each report is essentially a progress report. The authors of the individual quadrangle reports would appreciate any corrections or additional information that users may be able to contribute.

Alaska↗