Earth and Planetary Sciences ETDs

Publication Date

Summer 6-6-1946


The Dunmore lode is located near Ouray, Colorado in the northwest part of the San Juan Mountains. In structure as well as mineral assemblage it shows a connection between the chimneys and veins of the region. The lode averages about 100 feet wide for 1,200 feet along the Dunmore claim. The fissure zone is over two miles long and displacement along it has offset a folded pre-Cambrian complex 4,500 feet prior to the deposition of 2,400 feet of volcanic tuff. Fissures in the pre-Cambrian rocks controlled in part the intrusion of dikes and the formation of veins. Late Tertiary faulting extended the Dunmore fissure into the San Juan tuff, dropping the south side about 80 feet. Although most of the lode crops out in the pre-Cambrian rocks, it extends upward across the profound unconformity into the tuff. The complex lode contains sharply-marked fissure veins, sheared slate dragged into the fault zone, a sheared dike, breccia chimneys, and pebble dikes. An assemblage consisting of quartz, sericite, kaolin, and pyrite appears to be of early Tertiary age. The more productive part of the lode, however, is late Tertiary and consists of hematite chimney enclosing a copper shoot, and tungsten chimney, and compound base-metal fissure veins. These chimneys and veins are mostly localized along early Tertiary structures, but their mineral sequences correlate them with the social stage of late Tertiary deposition recognized by Burbank in the adjoining Red Mountain and other districts. The Dumore lode, however, is believed to have been deposited at greater depth and higher temperature and nearer to a source of supply than the lodes of these districts.

The ore possibilities are discussed in relation to the future development of the Dunmore mine, and recommendations are made for the development of various parts of the lode.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Vincent Cooper Kelley

Second Committee Member

Stuart Alvord Northrop

Third Committee Member

Harold Daniel Larson




Dunmore Mine, Ore Deposits, Tertiary Period

Document Type