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Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for...

Pre-Tertiary rocks of the Blue Mountain region of central and northeastern Oregon comprise three major sedimentary and volcanic sequences and two distinct intrusive magma series. The ages of the sedimentary-volcanic sequences are Paleozoic, Late Triassic-Late Jurassic, and middle Cretaceous (Albian to Cenomanian), respectively. The earlier intrusive magma series ranges in composition from peridotite to albite granite and was emplaced during the major...

THROUGH a fortunate circumstance, a recording magnetometer was operating in the city of Kodiak, 30 km north-west of the surface trace of a fault zone along which movement occurred at the time when the earthquake occurred in Alaska on March 27, 1964. Fortunately, too, the instrument...

Right-lateral separation of about 120 miles along Chatham Strait Fault is suggested by apparent displacement of major geologic features on opposite sides of the fault....

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The United States has about 250 fresh-water lakes that are known to have surface areas of 10 square miles or more. Nearly 100 of these are in Alaska, and 100 in Minnesota, Wisconsin, Michigan, New York,, and Maine. Thirty-four fresh-water lakes, exclusive of the Great Lakes, are known to have maximum...

Placer tin, in the form of cassiterite (Sn02) and (or) tinstone (fragments including cassiterite and some vein or rock material), is known or reported in deposits that have been prospected or mined for placer gold in four areas adjacent to the Yukon River in central Alaska, 120 to 240 miles...

Deposits of beryllium ore in the Lost River area of the western Seward Peninsula, Alaska, consist of replacement veins, pipes, and stringer lodes is limestone in a zone about 7 miles long and 2 to 3 miles wide which is faulted and intruded by dikes and stocks. The ores are...

The general distribution of high-alumina kaolinitic clay deposits in the United States (exclusive of Alaska and Hawaii) is shown on the accompanying map. The locations of mines, pits, and prospects are shown by appropriate symbols. Certain clay-bearing areas are shown by patterns that designate the geologic age of the deposits....

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The accompanying map shows the location of the principal known deposits of niobium and tantalum minerals in the United States, exclusive of Alaska and Hawaii. Symbols of different shapes are used to depict deposits of different geologic types, and large symbols denote deposits with a record of production. Small symbols...