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Paper No. 71-7
Presentation Time: 1:30 PM-5:30 PM
DOCUMENTING CHANGES IN FLUID EVOLUTION OF ORGAN MOUNTAIN ORE DISTRICT AT MEMPHIS MINE, NM
The Memphis Mine in the Organ Mountains of New Mexico is a zinc-copper skarn that was last mined in the 1920’s. Typically these hydrothermal deposits are associated with the emplacement of the Sugarloaf Peak batholith and associated volcanics. There are numerous other deposits of varying size throughout the Organ Mountains that include skarns, carbonate replacements, and porphyry deposits. Most of these deposits are copper-dominated but there are others dominated by zinc, lead, or silver mineralization (Lueth and McLemore, 1998). It is not entirely clear why the dominant metal(s) changes but they are proposed to be related to changes in temperature away from the intrusion. The unique aspect of the Memphis Mine is that it represents the one locality where the transition between these different metals has been documented, between the copper- and zinc-dominated mineralization. This study aims at understanding exactly how the fluid evolution at the transition take place by looking predominantly at the fluid inclusions found within these samples. Petrographic examination and microthermometry will be used to constrain the composition of the fluids involved with ore deposition and also provide minimum trapping temperature and pressure. Additionally, mineral phase equilibria will be determined to better constrain the pressure and temperature even more. Observing changes within the fluids between the prograde and retrograde mineral assemblages will aid in understanding how and why these ore deposits vary over a relatively small distance.