New Mexico Geological Society Annual Spring Meeting — Abstracts

Fluorite-bearing deposits are common in southwestern New Mexico and include several genetic types. Epithermal fluorite-quartz ± barite± calcite ± galena veins and repl cements are numerous and occur within and adjacent to the Rio Grande Rift. Veins of this type occur peripherally to economic Au-Ag-cu mineralization at the Lordsburg and Steeple Rock districts but are themselves barren of metals. Many others have no knon association with economic deposits. The Hansonburg Pb-Zn-(Cu) deposits contain abundant fluorite and have distinctly diffrrent genetic histories. This study is an effort to compare and contrast deposits based on their fluorite geochemis ries, with the hope that specific signatures linked to deposit type will emerge.

Trace and rare-earth element analyses were performed by XRF and INAA on 45 fluorite samples from across southwestern New Mexico. REE profiles and Sr, Y, U, and Na₂O differentiate several deposit groups. Host lithologies exert strong influences on fluorite compositions. Genetic styles appear to also contribute small components to trace and REE compositions. Distinct signatures for the Hansonburg deposits and magmato-hydrothermal Th-U-REE quartz-fluorite veins in the Capitan pluton are evident. Differentiation of volcanic-hosted deposit types is tenuous although some discriminating features may exist.

With the exception of the Capitan samples, fluid inclusions are simple two phase liquid/vapor systems. No daughter minerals have been observed. The Capitan fluorites contain high-salinity fluids with as many as eight daughter phases present. Fluid inclusion salinities and homogenization temperatures from a large group of deposits covary, suggesting a genetic link. Boiling is indicated by variable phase ratios in at least two deposits. Evidence of fluid mixing exists in some samples.