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- Permian copper shales of southwestern United States
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Permian copper shales of southwestern United States
Abstract
Many stratiform copper deposits are known in Permian shales and sandstones of Texas, Oklahoma, and Kansas, but the most important of these are six copper-shale ore bodies exposed in the Flowerpot Shale and San Angelo Sandstone along a total distance of some 200 km in Oklahoma and Texas. Individual ore bodies range from 15 to 45 cm thick and cover about 30 km2. Chalcocite is the primary ore mineral, and malachite is the main oxidation product. The average grade of different deposits is 1 to 2 % copper: other metals are present only in small amounts, generally less than 500 ppm.
The flat-lying ore beds are medium-gray laminated silty shales that are interbedded with red-bed clastics and evaporites. One ore body is being strip mined, another is being developed, and the other four are being prospected.
The host shales apparently were deposited in a brackish-water or shallow-marine environment, and syngenetic or early diagenetic copper mineralization might have occurred by replacement of pyrite.