New Mexico Geological Society Annual Spring Meeting — Abstracts

Tin mineralization occurs within rhyolite and ash flow tuff in the Taylor Creek Tin District. The occurrences of vein and disseminated mineralization in ash flow tuff are in conflict with the age and spatial restrictions to the Taylor Creek Rhyolite as inferred by several previous investigators. Numerous, mineralized localities are typified by irregular networks of hematite-cassiterite-silica veins with replacement and open-space textures.

Semiquantitative spectographicanalyses of surface and drill hole samples demonstrate that As, Pb, Sb, and Zn enrichment as great as 5000 ppm, 15,000 ppm, 1000 ppm and 10,000 ppm respectively, are associated with tin mineralization. Fluorine is highly enriched in mineralized zones in the form of microcrystalline fluorite. Alteration of hosts are primarily chardcterized by the introduction of hematite and corresponding iron enrichment although silicification is locally significant.

Preliminary fluid inclusion studies of cassiterite exhibit homogenizaticn temperat ures ranging from 344°C to 417°C. Relatively high formational temperatures of crystalline cassiterite and intergrown wood tin are in contrast to low temperature inferences commonly made. Daughter crystals are commonly abundant in fluid inclusions and reflect the complexity of mineralizing solutions.

Mineralization is not restricted to the domes and flows of the Taylor Creek Rhyolite (25 m.y.) and the occurrences in overlying Railroad Canyon Tuff (23.5 m.y.) indicate tin introduction to be Significantly younger than Taylor Creek time. The temperature, chemical and mineralogical associations of cassiterite mineralization in the Taylor Creek Tin District are compatible with a hydrothermal origin.