Geology and mineral deposits of the Needle Mountains District, Southwestern Colorado

Geology and uranium mineralization of the Florida Mountain area, Needle Mountains, southwestern Colorado

“…for the older body and 10 ± 1.1 m.y. for the younger body (Schmitt and Raymond, 1977). The relative ages of the two bodies are clearly established by field relationships; the discrepancy in absolute ages is well within the analytical error and is highly suggestive that the two intrusions were closely related temporally.…”

“…Disseminated pyrite is abundant throughout the intrusion. Schmitt and Raymond (1977) identified IMd, 1M, and 2M polytypes of sericite, which supposedly indicate increasing temperatures of alteration. The most abundant polytype is 1M, although in the western part of the body 2M sericite predominates and is associated with kaolinite, indicating more intense hydrothermal activity.…”

“…Field data from this investigation were later expanded upon and published separately (Schmitt and Raymond, 1977). This latter work concentrated principally on the Chicago Basin stock, a small composite Tertiary intrusion in the northern part of the study area.…”

“…These fragments, which consist mostly of very fine grained to cobble-size clasts of quartz and quartzite, were considered by Cross and others (1905) to be xenoliths of the Uncompahgre Formation. Schmitt and Raymond (1977) considered it unlikely that the Uncompahgre Formation should underlie the Eolus Granite in this area and also believed that the breccia fragments more closely resemble conglomerates of the Cambrian Ignacio Formation. Projecting from the nearest outcrops of Cambrian rocks on Mountain View Crest and Lime and Stag mesas, it is estimated that the current level of exposure is 700-800 m below the Cambrian erosion surface at the time the stock was emplaced.…”

Mineral resource potential of National Forest RARE II and wilderness areas in Colorado

“…Gold and silver were produced from vein deposits throughout the district, and copper, lead, and zinc also occur in these veins although they were not produced. Geologic mapping, geophysical and geochemical data suggest the strong likelihood of large disseminated molybdenum deposits at depth (Schmitt and Raymond, 1977). The Beartown mining district is adjacent to the northwestern part of the wilderness area and produced gold, silver, copper, and lead from several mines in the district, none of which is located within the wilderness.…”