TIMING AND SOURCE OF HYDROTHERMAL FLUIDS IN THE MOGOLLON MINING DISTRICT, CATRON COUNTY, NM

The Mogollon Mining District in Catron County, New Mexico is a region of the Mogollon Mountains that was known for its gold and silver production. Between 1904 and 1942, 317,390 ounces of gold and 15,589,407 ounces of silver were produced from the Mogollon District which makes it the richest silver deposit in New Mexico. The district has been dormant since the 1940’s but exploration activity has persisted. The subsequent mineralization brought hydrothermal alteration, depleting the surrounding country rock of Ca, Sr, and Na while enriching the rock in Ag, Au, K, and Rb. Economically-rich ore bodies are commonly found where Fanney Rhyolite is juxtaposed against the younger Mineral Creek Andesite. Alteration in the Mineral Creek Andesite is more pronounced, and promoted precious metal precipitation away from the veins.

Mogollon Mining District mineralization is mostly low-sulfidation class deposits controlled by local structure filling in open spaces in fractures, faults from the collapse of the Bursum caldera and locally along bedding planes. Complex vein textures, especially brecciation and banded layering, are commonly associated with higher concentrations of metals. Four distinct stages of mineralization have been described based on the abundances of quartz, calcite, and fluorite and these phases hosted fluid inclusions. Stage I consists of quartz veins forming at >260˚C, Stage II consists of calcite that precipitated around 240˚C, Stage III precipitated quartz and calcite between 240˚C and 215˚C, and finally Stage IV consists of fluorite precipitation between 210˚C and 160˚C. Each of these stages had constant salinity of about 3.3 equivalent weight percent NaCl.

Here we present new trace element data and the first stable isotope values of calcite in the Queen Vein of the Mogollon Mining District to determine the partitioning of incompatible elements between the fluid and host rock, and how partitioning changed over time in the hydrothermal system. We suggest that the hydrothermal alteration coincided with the late phases of volcanism at ~22 Ma and that the fluids are epithermal and meteorically sourced.