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Geology topics

Robert G. Bates

Publications and source records attributed to Robert G. Bates.

6 recordsLinked to original sources
USGS1974

Correlation between geophysical data and rock types in the Piedmont and coastal plain of northeast Virginia and related areas

Physical, chemical, and mineralogic characteristics of rock units in parts of the northeast Virginia Piedmont are reflected in the aeromagnelic, aeroradioactivity, and gravity data for this area. Magnetic anomalies show the areal distribution of rocks containing magnetite. Aeroradiometric anomalies in the Piedmont and Coastal Plain provinces are directly related to the K 2 O content of the formations. In the crystalline rocks of the Piedmont this is reflected in their muscovite and microcline content, whereas in the Coastal Plain province it is related to the glauconite content of the Aquia Formation. Locally, in the crystalline rocks of the Piedmont, uranium- and thorium-bearing mineral content is of greater importance than K 2 O-bearing mineral content in producing aeroradiometric anomalies. The region also is characterized by (1) a northern gravity high, (2) a southern gravity high presumed to be caused by mafic rocks, and (3) an intervening zone characterized by low gravity relief and underlain by schist and gneiss. Geologic and geophysical extrapolation southward toward the Arvonia area show that the Chopawamsic Formation and the volcanic rocks of the Evington group are coeval. Also, on the northwest side of these volcanic rocks is a belt of small rootless mafic and ultramafic rocks diapirically ceplaced in folded rocks of Early Cambrian (?) age.

Virginia↗
USGS1957

Reconnaissance for uranium and thorium in Alaska, 1954

During 1954 reconnaissance investigations to locate minable deposits of uranium and thorium in Alaska were unsuccessful. Areas examined, from which prospectors had submitted radioactive samples, include Cap Yakataga, Kodiak Island, and Shirley Lake. Unconcentrated gravels from the beach at Cape Yakataga average about 0.001 percent equivalent uranium. Uranothorianite has been identified by X-ray diffraction data and is the principal source of radioactivity in the Cape Yakataga beach sands studied; but the zircon, monazite, and uranothorite are also radioactive. The black, opaque uranothorianite generally occurs as minute euhedral cubs, the majority of which will pass through a 100-mesh screen. The bedrock source of the radioactive samples from Kodiak Island was not found; the maximum radioactivity of samples from the Shirley Lake area was equivalent to about 0.02 percent uranium. Radiometric traverses of the 460-foot level of the Garnet shaft of the Nixon Fork mine in the Nixon Fork mining district indicated a maximum of 0.15 mr/hr. In the Hot Springs district, drill hole concentrates of gravels examined contained a maximum of 0.03 percent equivalent uranium. A radioactivity anomaly noted during the Survey's airborne reconnaissance of portions of the Territory during 1954 is located in the Fairhaven district. A ground check disclosed that the radioactivity was due to accessory minerals in the granitic rock.

Alaska↗
USGS1955

Reconnaissance for radioactive deposits in Alaska, 1953

During the summer of 1953 the areas investigated for radioactive deposits in Alaska were on Nikolai Creek near Tyonek and on Likes Creek near Seward in south-central Alaska where carnotite-type minerals had been reported; in the headwaters of the Peace River in the eastern part of the Seward Peninsula and at Gold Bench on the South Fork of the Koyukuk River in east-central Alaska, where uranothorianite occurs in places associated with base metal sulfides and hematite; in the vicinity of Port Malmesbury in southeastern Alaska to check a reported occurrence of pitchblende; and, in the Miller House-Circle Hot Springs area of east-central Alaska where geochemical studies were made. No significant lode deposits of radioactive materials were found. However, the placer uranothorianite in the headwaters of the Peace River yet remains as an important lead to bedrock radioactive source materials in Alaska. Tundra cover prevents satisfactory radiometric reconnaissance of the area, and methods of geochemical prospecting such as soil and vegetation sampling may ultimately prove more fruitful in the search for the uranothorianite-sulfide lode source than geophysical methods.

Alaska↗
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↗