New Mexico Geological Society Annual Spring Meeting — Abstracts

The San Mateo Mountains of south-central Socorro County are located within the Mogollon-Datil volcanic field of southwestern New Mexico. A thick sequence of Tertiary-aged tuffs, lavas, and associated volcaniclastic and sedimentary rocks in the southern San Mateo Mountains is exposed in large tilted fault blocks surrounded by alluvial fans, low-relief pedimented bed-rock surfaces, and scattered exposures of pre-Tertiary basement rocks. Repeated volcanotectonic activity in the area has produced complex stratigraphic and structural relationships.

Tertiary (Oligocene) rock units of the southern San mateo Mountains include the Red Rock Ranch Formation (up to 1000 m thick), Rock spring Formation (up to 1200 m thick), La Jencia Tuff (0-25 m thick), Vicks Peak Tuff (300-1400 m thick), tuff unit of Turkey Springs (60-120 m thick), tuff unit of Milliken Park (0-60 m thick), and interbedded lavas including the Springtime Canyon Quartz Latite (0-180 m thick). Mafic, intermediate, and felsic intrusive rocks are locally exposed along fault systems in the area.

Ore deposits of the southern San Mateo Mountains occur within distinct host-rocks. Gold-silver mineralization located in the San Jose mining district is hosted by Vicks Peak Tuff within fracture zones, hydrpthermal breccias, and quartz veins. Silver-gold base-metal deposits in the Diggins prospect area occur in mineralized tuffs and lavas of the Rock Spring Formation and cross-cutting intrusive rocks. Gold mineralization is associated with late-phase felsic intrusive rocks, fracture systems, and alteration zones which are discernable in classified satellite imagery.