FLUID EVOLUTION AT THE EXCELSIOR COPPER SKARN, ORGAN MOUNTAINS, NM

The Excelsior Mine is located in the northwest portion of the Organ Mountain district, NM, and is classified as a copper skarn. There are multiple ore districts within the Organ Mountains, varying between different types of deposits occurring in the area. Most of the ore deposits are hypothesized to be largely derived from hydrothermal fluids coming off of the Sugarloaf Peak quartz monzonite (Lueth and McLemore, 1998). These fluids intruded into the Paleozoic sedimentary sequences of marine carbonates, shales and sandstones (Newcomer and Giordano, 1986). There are different degrees of fluid maturity occurring in this area as well as specific zoning of the different mineralization that took place (Lueth and McLemore 1998). Our study is primarily looking to examine the fluid maturity in the Excelsior skarn to understand the development of the metasomatic fluids. This will be done by conducting petrographic studies to observe fluid inclusion assemblages within the minerals to study the multiple stages of fluid alteration and to constrain prograde versus retrograde mineralization. Microthermometry of the fluid inclusions was conducted on a heating-freezing stage on the different FI assemblages to understand the precise geochemistry of the fluids and provide minimum trapping conditions. The precise pressure and temperature conditions of the fluids involved in mineralization will be determined using the geochemistry of different mineral equilibria to better understand the complexity of the system and how it matured throughout time.