Ore Microscopy and Genesis of the Copper-Shale Deposit at Creta, Oklahoma

Ore microscopic study of copper-bearing shale at the Creta mine in southwestern Oklahoma reveals a variety of copper sulfide grains and shows that each has originated by replacement of original constituents in the Permian Flowerpot Shale at Creta. The largest grains, about 120 μm in diameter, are replacements of megaspores with triletes morphology. Their interiors are shown by Auger microprobe analyses to be organic matter. The interior organic matter and the spore exines have been replaced by anilite and djurleite. The results of this study indicate that the copper minerals are epigenetic and were deposited from fluids introduced into the Creta shale when it was relatively uncompacted and permeable. The shale served as a favorable reducing environment that contained a source of sulfur in the form of pyrite and pyrrhotite.