Geology topics

Research about Blying Sound Quadrangle, Seward Quadrangle

Source-linked reports with geographic coverage including Blying Sound Quadrangle, Seward Quadrangle.

6 recordsLinked to original sources

USGS1982

Metalliferous mineral resource potential of the Seward and Blying Sound quadrangles, southern Alaska

This mineral potential map is the final report in a series of publications that makes up a folio on the Seward and Blying Sound quadrangles of southern Alaska. It draws on data largely presented in previous publications of the folio. The studies were undertaken as part of the Alaska Mineral Resource Assessment Program (AMRAP), a program designed to provide information for Federal, State, local, and industry decisions concerning the future uses of Alaskan lands and resources.

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USGS1979

Geologic interpretation of the gravity anomaly map of the Seward and Blying Sound quadrangles, Alaska

For more than 20 years, gravity surveys have been conducted in the vicinity of Prince William Sound, the epicentral region of the great Alaska earthquake of March 27, 1964. Some of the major regional gravity anomalies were outlined by Thiel, Ostenso, Bonini (1960), and additional anomalies were defined by pre- and post-earthquake gravity studies reported by Barnes and Allen (1965) and Case, Barnes, Plafker, and Robbins (1966). Another gravity anomaly map was prepared by personnel of the U.S. Coast and Geodetic Survey (now the National Oceanic and Atmospheric Administration) (Wood, 1966, p. 131; Rice, 1969, p. 5-20). Anomalies shown by Rice (1969) are broadly similar to those shown by Case, Barnes, Plafker, and Robbins (1966); Rice's interpretations concerned mainly gravity changed related to the earthquake, and the data were not interpreted in terms of regional geology. New gravity stations were established in 1976 as part of the mineral resource appraisal of the Seward and Blying Sound quadrangles. This report incorporates the new data obtained in 1976, reinterprets some anomalies previously discussed by Case, Barnes, Plafker, and Robbins (1966), and interprets other anomalies not previously discussed. Descriptions of the major rock units and structural features are found in the companion report by Tysdal and Case (in press). An interpretation of the aeromagnetic map of the region has been prepared by Case, Tysdal, Hillhouse, and Gromme (1979).

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USGS1979

Geologic interpretation of aeromagnetic map of the Seward and Blying Sound quadrangles, Alaska

An aeromagnetic survey of the Seward and northern part of the Blying Sound quadrangles was flown by Geometrics, Inc., during 1975-77 to provide magnetic data to aid in an appraisal of the mineral resources. Background details of the regional geology and major structures are described in a companion report by Tysdal and Case (1979), and interpretation of the gravity data are described in a report by Case and others (1979). Preliminary reports of a paleomagnetic investigation have been reported by Hillhouse and Gromme (1977), and a more complete analysis of the results is in preparation. The aeromagnetic survey was flown at a nominal height of 300 m above the surface and flight lines were spaced about 1.7 km apart. Total magnetic field was measured by a proton-precession magnetometer. The International Geomagnetic Reference Field (IGRF), updated to 1976, was removed, and the residual values were computer-contoured to produce the aeromagnetic map (sheet 1). Detailed aeromagnetic maps at scale 1:63,360 and a map at scale 1:250,000 have been released as Open File Reports 78-1080 through 1083 (U.S. Geological Survey, 1978). Magnetic anomalies in the Seward-Blying Sound region are somewhat less complex than in other parts of south-central Alaska, primarily because of the huge volume of relatively nonmagnetic flysch that constitutes the Valdez and Orca Groups. Several rather isolated groups of mafic-ultramafic rocks are significantly more magnetic than the flysch assemblages, and cause distinctive patterns of magnetic anomalies. A few of the granitic plutons are magnetic, but most appear to have little or no magnetic expression.

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USGS1978

Mines, prospects, and occurrences map of the Seward and Blying Sound quadrangles, Alaska

The Prince William Sound region may be considered as made up of two extensive and distinctive mineral belts defined by the preponderance of either gold or copper deposits (Capps and Johnson, 1915). In the Seward and Blying Sound quadrangles, the division of the two belts is approximately along the Contact fault, which trends northeast across the quadrangles. The gold belt includes the Moose Pass-Hope district and the Port Wells district. The copper belt is exposed mainly on Latouche, Elrington, Bainbridge, Knight, Chenega, and Glacier Islands and the mainland area between Unakwik Inlet and Columbia Bay.

Alaska↗

USGS1978

Geochemical map showing the distribution and abundance of copper in stream sediments 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). This map shows the distribution and abundance of copper in stream-sediment samples. Stream-sediment samples were collected at 569 sites 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. The 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 copper and 15 other elements by a semiquantitative spectrographic method (Grimes and Marranzino, 1968). Other splits were analyzed for gold and zinc by atomic absorption methods (Warren and others, 1969). Sample sites and copper values (in parts per million) are indicated on the map by symbols identified in the histogram. The weakly anomalous values are considered to be significant only where they were detected in stream-sediment or heavy-mineral concentrate samples that also contained strongly anomalous values of other metals such as arsenic, gold, lead or tungsten. The map shows two populations for copper in stream sediments. One population consisting of generally lower copper values represents the samples collected from the sedimentary terrane in the central and western parts of the quadrangles. The other population consisting of generally higher copper values includes samples collected in areas of sheeted basalt dikes and pillow basalts in the eastern part of the quadrangles and from the sedimentary terrane of Latouche Island; in these areas chalcopyrite and pyrite were observed as fine-grained disseminations in the rocks and as mineral particles in the heavy-mineral concentrates.

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.

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