The Pecos Mine: A Deep Dive Into Precambrian Geology

The pecos mine is largest of these deposits in new mexico. The area of some 12,500 mi 2 is dominantly. Four trondhjemitic bodies — three of intrusive and one of extrusive origin — 1. 7 to 1. 8 b. y. In age occur in the precambrian rocks of northern new mexico and southwestern colorado. Riesmeyer (1978) discusses the precambrian volcanic and sedimentary geology, and the ore deposits of the pecos mine area in more detail than the present summary.

The precambrian terrane north of pecos, new mexico, contains meta­volcanic and metasedimentary rocks. The subaqueous volcanic rocks are of bimodal composition (basalt. Anomalous amounts of silver and/or gold have been identified in 153 mining districts or prospect areas of new mexico. Production from most of these occurrences has been small; From west to east along willow creek, the intrusives are diabase, dacite, granodiorite and granite.