Abstract

CHROMITE IN OREGON

BY JOHN ELIOT ALLEN

Chromite deposits occur in the Klamath Mountains of southwestern Oregon and in the Blue Mountains of northeastern Oregon. They always occur in peridotite, dunite, serpentine, or associated ultrabasic rocks, thought to be Cretaceous.

The most common ore bodies are tabular lenses, though many are pod- or kidney‐shaped masses, and some are narrow dikelike seams, stringers, or irregular patches. With a few important exceptions, all are small. Of 229 bodies at 141 localities in the State, only 42 gave promise of yielding over 100 tons of ore.

The attitudes of the ore bodies with respect to each other and to the surrounding rock structures and contacts strongly suggest structural control of emplacement. They usually lie within zones of hydrothermally altered rock essentially parallel to the trend of the elongated peridotite or serpentine. These zones also intersect, forming diamond-shaped strain patterns with respect to the . . .

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