New Mexico Geological Society Annual Spring Meeting — Abstracts

Manganese, barite, and fluorite have been mined and prospected in the Little Florida Mountains. Mineral deposits in the big Florida Mountains include manganese, barite, fluorite, zinc, lead, copper, silver, and gold. Mineralized veins in the Little Florida Mountains are in post-23.6-my-old rocks. Veins and oxidized replacement deposits in the Big Florida Mountains are mostly in early Paleozoic carbonate and alkalic plutonic rocks. A few veins are in faulted Eocene rocks. Propylitic alteration is pervasive in Tertiary volcanic breccias and conspicuous epidote coats fractures of these and older rocks in the Florida Mountains. Argillic alteration has significantly changed the alkalic syenites throughout the central Florida Mountains. Source of Eocene volcaniclastics is unknown but andesitic sills and dikes intruded into them indicate post-early Eocene igneous activity in the Florida Mountains. Fanglomerates shed from 23.6-my-old rhyolites in the Little Florida Mountains were lithified and faulted preceding mineralization. A dacitic volcanic vent in the southeastern Little Florida Mountains is believed to coincide with this stage of mineralization. Several small intrusions of finely-crystalline adamellite in the big Florida Mountains, although of unknown age, intrude small Laramide thrust sheets. Lithologically identical rocks intrude middle Oligocene volcanic rocks in the Mimbres basin near Deming.

An adamellite batholith probably underlies the Florida Mountains and northeastern part of the Mimbres basin. The dacite plug in the southeastern Little Florida Mountains resents a surficial venting of this magma during early to middIe Miocene time. Penecontemporaneously hypabyssal adamellite intruded the Paleozoic and Cenozoic roof rocks in the Florida Mountain-Deming area. Associated hydrothermal pneumatolytic fluids formed the ore deposits and extensive alteration.