New Mexico Geological Society Annual Spring Meeting — Abstracts

The silver-gold deposits of the Carbonate Creek area are entirely contained within Paleozoic sedimentary rocks. The Fusselman dolomite, El Paso limestone, and Lake Valley limestone were extensively replaced by fine-grained silica (jasperoid) along a series of N-W trending faults prior to silver-gold mineralization. These faults are the major ore control of mineralization in the area.

Silicification took place in two stages, with mineralization during the second stage. In the first stage, after faulting, hydrothermal solutions flowed up along the faults silicifying the wall rocks. The carbonate rocks, mostly the Lake Valley and Fusselman limestones, that were in contact with the faults, were highly silicified forming large jasperoid zones along the faults. In the second stage, reactivation of faults in the area brecciated and fractured the silicified wall rock and jasperoid zones. Epithermal solutions then flowed up through the faults silicifying and mineralizing the brecciated and fractured zones. The peculiar alteration that preceded or coincided with mineralization renders limestone to a powdery, soft calcite-clay mixture which, along with fault gouge, clogged faults where they traversed limestone and reduced open space.

Ore mineralization is mostl y acanthite, pyrargyrite, prustite, polybasite, with some native silver, native gold, chalcocite, and small amounts of azurite, malachite, and cerargyrite. Gangue mineralization is mostly silica, with some calcite, limonite, hematite, and small amounts of manganese oxides, pyrite, fluorite, dickite, and roscoelite.