New Mexico Geological Society Annual Spring Meeting — Abstracts

Fossil geothermal systems at Box Canyon and San Diego Mountain, in southern New Mexico, are hosted within the Plio-Pleistocene Camp Rice Formation. The Box Canyon geothermal system is focused around an east-west trending, fractured Oligocene-age rhyolite dike, while the San Diego Mountain system is exposed along an arroyo escarpment near the 10rnada fault zone. The Camp Rice was mapped into lithofacies using grain-size, depositional environment, and sedimentary structures. The geothermal mineralization of the Camp Rice is classified into pore cement assemblages based on the dominant pore cement and emplacement within specific zones of the lithofacies. The Box Canyon pore cement assemblages are: silicate-clay, iron oxide-calcite-silicates, calcite dominant, and iron oxide-calcite. The majority of the alteration at Box Canyon is in the form of poikilotopic calcite cement in coarsegrained fluvial sandstones. These calcite cemented sandstones extend up to 1.5 km southwest from the rhyolite dike. The San Diego Mountain pore cement assemblages are: minor quartz, hematite-silicate, hematite-calcite-silicates, silicate dominant, and potassic-silicate. The silicate cementation is more extensive within the fault zone and extends laterally outwards within the coarse fluvial sandstone. The majority of the cementation extends less than 0.5 km away from the fault zone. The Box Canyon and San Diego Mountain geothermal systems were quite distinct in their chemistry and fluid movement. The Box Canyon outflow plume was calcite-saturated, and spread southwest for up to 1.5 km from the source. Whereas the San Diego Mountain outflow plume reached a higher temperature and was silica-saturated, spreading less than 0.5 km from the Jornada fault.