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Research about Seward Peninsula

Source-linked reports with geographic coverage including Seward Peninsula.

At least 37 records · Page 2Linked to original sources
USGS1987

Geology and origin of the Death Valley uranium deposit, Seward Peninsula, Alaska

A uranium deposit discovered in 1977 in western Alaska, by means of airborne radiometric data, is the largest known in Alaska on the basis of industry reserve estimates. At about latitude 65 degrees N, it is the most northerly known sandstone-type uranium deposit in the world. The deposit lies in Eocene continental sandstone near the eastern end of the Seward Peninsula, in the southern end of a graben that extends northward into the Death Valley depositional basin.The deposit is apparently of epigenetic and supergene origin. The uranium was derived from the Cretaceous granite of the Darby pluton that forms part of the western side of Death Valley. Uranium from primary mineralization is in the subsurface in a marginal facies of the Tertiary sedimentary basin where nearshore coarse clastic rocks are interbedded with coal and lacustrine clay. Primary mineralization occurred when uranium-bearing oxidizing ground water moved downdip from the pluton eastward through transmissive clastic beds or on the surface. Uranium was deposited where the coal or other carbonaceous material produced a reducing environment in arkosic host rocks. The supergene enrichment is related to a soil horizon at the present ground surface. The most common uranium mineral is meta-autunite, but cofflnite has been identified in the primary deposits. The host rocks for the primary deposits were partly covered by basalt flows that issued from nearby vents. Some of the basalt is highly altered, and some basalt float from the supergene zone has alteration rinds that are enriched in uranium.Extensive exploratory drilling took place from 1979 to 1981. The average grade of the potential ore is 0.27 percent U 3 O 8 and the average thickness is 3 m. The calculated reserves are 1,000,000 lbs U 3 O 8 ; additional drilling would probably add to this figure.

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USGS1985

Sea cliff exposures of metamorphosed carbonate and schist, northern Seward Peninsula: A section in The United States Geological Survey in Alaska: Accomplishments during 1983

Extensive seacliff exposures of marble, metadolostone, and schist occur on the north shore of Seward Peninsula in the Kotzebue A-1 and A-2 Quadrangles (fig. 12). Some of the exposed units have no analogs when compared to rocks mapped to the south in the Bendeleben and Solomon Quadrangles. Others are similar to units exposed to the south, but they differ in metamorphic grade and minor, though significant, compositional characteristics. Carbonate rocks predominate from Ninemile Point westward; schists of varying composition occur with carbonate rocks to the east. The carbonate-dominated section is separated in the vicinity of Ninemile Point from the schist-dominated section by a major fault zone, thought to be the northern extension of the Kugruk fault zone of Sainsbury (1974).

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USGS1983

Tin granites of Seward Peninsula, Alaska

Seven granite plutons, spatially and genetically related to tin metalization, are exposed in a 170-km-long belt across northwestern Seward Peninsula, Alaska. These plutons are cupolas and epizonal composite stocks that consist of several textural varieties of biotite granite, including medium- to coarse-grained seriate biotite granite, porphyritic biotite granite with an aplitic groundmass, and fine- to medium-grained equigranular biotite granite. The common accessory minerals are fluorite, allanite, apatite, and zircon. Other accessory minerals that are locally present include tourmaline, sphene, opaque oxide minerals, and late-forming (deuteric) muscovite and chlorite. The granites range in major-element contents as follows: SiO 2 , 72.5% to 76.6%; A1 2 O 3 , 12.7% to 14.3%; Na 2 O, 2.9% to 4.0%; K 2 O, 3.9% to 5.6%; and CaO, 0.6% to 1.2%. The sum of FeO + Fe 2 O 3 + MgO ranges from 0.3% to 2.4%; and the K 2 O to Na 2 O ratio from 1.1 to 1.8. The 0.1% to 0.9% F and 0.01% to 0.2% Cl reflect the over-all volatile-rich nature of the granites. The granites contain average or below-average concentrations of Co, Sc, Cr, and Zn, and generally above-average to distinctly high concentrations of Th, U, Hf, and Ta. The large cations emphasize the evolved nature of the granites; the Rb/Sr ratio is as high as 90 in some samples. Initial 87 Sr/ 86 Sr ratios range from 0.708 to as high as 0.720. The three Rb-Sr isochrons defined by the data agree with K-Ar age determinations and show that the stocks were emplaced during the Late Cretaceous, between about 70 and 80 m.y. ago. The field, petrologic, and geochemical data indicate that the plutons had a multistage origin that involved large-scale melting of sialic crust, emplacement of magmas derived from batholithic fractionation at depth, and subsequent evolution of these magmas to generate small volumes of more highly evolved residual magmas. Although evolution of the granite complexes was largely governed by crystal-melt fractionation, some minor-element variations in the highly evolved granites cannot be explained by this process. For example, the distribution of rubidium and the light rare-earths appears to have been influenced by volatile depletion at the final stages of crystallization. The field data, petrologic data, and variation trends, such as distinct shifts toward higher albite contents in the residual granites, suggest that the coexistence of a volatile phase was important in their evolution. These results require that models seeking to explain compositional gradients in high-level granite (rhyolite) systems fully consider the role of a coexisting volatile phase.

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USGS1977

Preliminary geologic map of Seward Peninsula, Alaska

This preliminary map is the first of several data compilations being prepared as a foundation for evaluating the mineral resource potential of Seward Peninsula. In addition to the sources of geologic data credited in the index map, Sainsbury's recent (1975) summary of his extensive geologic studies on Seward Peninsula has been particularly helpful. The map, unit descriptions, and correlations reflect as closely as possible the geology as published in the principal sources of geological data. Important sources of additional and more detailed descriptive data are referenced in the description of map units.

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USGS1977

Carborne radiometric survey of the Nome area, Seward Peninsula, Alaska

A carborne radiometric survey was made along the accessible roads in the Nome, Alaska, area. The background radiation was generally found to be low, about 40 cps, but higher radioactivity near granite was noted. No radioactive anomalies of a magnitude greater than three times the average background were encountered.

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USGS1976

A reconnaissance study of the uranium and thorium contents of plutonic rocks of the southeastern Seward Peninsula, Alaska

Large granitic Cretaceous plutons are exposed along and adjacent to an arcuate belt of igneous and high-grade raetamorphic rocks in the southeastern Seward Peninsula of Alaska. Reconnaissance studies of these plutons have shown that the Darby pluton has well above average amounts of uranium and thorium (11.2 ppm and 58.7 ppm, respectively), the Kachauik pluton contains average to above average uranium and thorium (5.7 ppm and 22.5 ppm, respectively), and the Bendeleben pluton contains average amounts of uranium and thorium (3.4 ppm and 16.7 ppm, respectively). The three plutons show compositional and textural differences indicative of different source materials that may have controlled the distribution of uranium and thorium. The high uranium and thorium contents of the Darby pluton, similar to those of the Conway Granite of New Hampshire which has been mentioned as a possible low-grade thorium resource, suggest that this pluton may be a favorable area for economic concentrations of uranium and thorium.

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USGS1962

A new occurrence of beryllium minerals on the Seward Peninsula, Alaska

Beryllium in the form of chrysoberyl was found at a new locality on the public domain on the Seward Peninsula. The beryllium is associated with altered dikes and marmorized limestone veined with fluorite-tourmaline-chrysoberyl veinlets. Although the chrysoberyl is fine grained and intergrown intricately with the fluorite and tourmaline, it has been separated and identified by X-ray diffraction. Specimens of ore selected randomly from areas of fluoritized limestone contain beryllium in the range .01 to 3.3 percent BeO. The area warrants detailed mapping and sampling, which will be done by the U.S. Geological Survey in 1962.

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USGS1952

Preliminary summary of reconnaissance for uranium on the Seward Peninsula, Alaska, During 1951

Reconnaissance examinations for uranium were made at nine localities in the York, Nome, and Koyuk districts of the Seward Peninsula, Alaska, during .the 1951 field season. In addition carborne radiometric traverses were made of four roads in the Nome and Council districts. Only at Brooks Mountain in the York district are uranium-bearing deposits that required detailed study. On the southwest flank of Brooks Mountain, zeunerite occurs as a surface coating on quartz-tourmaline veins occupying joint fractures in granite| at a second locality, also on the southwest flank of the mountain, zeunerite is disseminated in a highly-weathered, altered zone of granite near a contact with limestone. Preliminary radiometric analyses show an average of about 0.05 percent equivalent uranium in the vein material and about 0.07 percent equivalent uranium in the weathered, altered granitic zone.

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USGS1944

Graphite deposits on the north side of the Kigluaik Mountains, Seward Peninsula, Alaska

The graphite deposits on the north side of the Kigluaik Mountains have been known for many years, and have yielded a small quantity of flake graphite, but they have been only slightly developed. The author spent 4 days of June 1943 in company with Mr. H. E. Heide, mining engineer of the Bureau of Mines, and Mr. Norman Tweet, part owner of one of the properties. Acknowledgment is due Mr. John Read and the Lomen Commercial Company for many favors rendered in connection with the investigation. The chemical analyses in this report were made by F. S. Grimaldi, of the Geological Survey. The deposits were examined many years ago by Harrington 1/ who discussed the general geology and described the developments up to the date of'his examination. Much of the history of the district given below is taken from his report. According to Harrington, the first claims were staked in 1900. Two principal groups of claims were worked, those of the Uncle Sam Alaska Mining Syndicate and those of the Alaska Graphite Mining Company. Harrington records that the claims of the Alaska Graphite Mining Company were staked in part in 1905 and in part in 1915 or 1916. A production of 35 tons picked from talus was reported for 1907. According to Mertie, 2/ the production in 1916 was about 100 tons, which according to Harrington, was shipped in 1917, together with several tons mined from an open cut in that year. In 1912, according to Mertie, shipments totalling 130 tons of graphite were made by the Uncle Sam. Alaska Mining Syndicate, and 300 tons were ready for shipment in 1916. Harrington, who visited the area in 1917, reported that no shipments were made in that year by that company. No records of subsequent production have been found. The properties apparently lay dormant until the summer of 1943, when renewed interest was expressed in the restaking of claims. Graphite deposits are widespread in the Kigluaik Mountains. 3/ The deposits described in the report have received the most attention because of their relative accessibility. These deposits are about 36 miles northwest of Nome and about 26 miles east of Teller (see fig. 1). The principal deposits are 2 to 3 miles from an arm of the Imuruk Basin, and about 27 miles by salt water from Teller. Most of the Imuruk Basin is shallow and does not exceed a fathom in depth at distances as much as a mile from shore. Arrangements may be made at Teller to charter small boats for the trip to the graphite-bearing area. The portion of the area between the Kigluaik Mountains and the Imuruk Basin (see fig. 2) is chiefly a gently-sloping alluvial fan, in which the larger creeks are intrenched from 10 to 30 feet near the mountain front. The creek herein called Graphite Creek, the northeasternmost creek shown on figure 2, is about 2 miles southwest of the Cobblestone River. Ruby, Ptarmigan and Trail Creeks transect the mountain front in the order named, proceeding southwestward from Glacier Creep. Farther to the southwest, some of the smaller creeks are unnamed. The creek about 1.4 miles southwest of Trail Creek is herein called Christophosen Creek in order to have a convenient means of reference.

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