Peter M. Gerrild 1972 <p>A tarry, benzene-soluble material is present in metal-rich veins in the Idarado mine, Ouray, Colo., in an area not known to have petroleum resources. The material was compared chemically, spectrometrically, and chromatographically with oils from four fields in the nearby Paradox basin. Each oil field contains reservoir rocks equivalent to rock units known to extend beneath volcanic rocks near the mine. Carbon and sulfur isotope data and gas chromatographic data indicate a similarity between the oil from the Sierra field and the "oil" from the mine. Thus, the origin of the vein oil from Cretaceous sediments seems both geologically and chemically possible.</p> application/pdf 10.3133/ofr72129 en U.S. Geological Survey Genesis of oil in metalliferous veins, San Juan Mountains, Colorado reports