POTENTIAL HYDROTHERMAL ACTIVITY AT A LARGE CARBONATE MOUND: IMPLICATIONS FOR PLUVIAL LAKE PANAMINT

Samples collected from a large carbonate mound in Panamint Valley, CA may indicate the presence of a hot spring contributing to pluvial Lake Panamint. Initial petrographic analysis indicates unusual assemblages for a fresh water tufa deposit. The presence of the ostracode Limnocythere staplini suggests a saline solute composition with a low alkalinity/Ca ratio and juvenile ostracode cyprid shells suggest a spring discharge. Linear structures and alignment noted in aerial photographic analyses suggest possible fault control of the mound’s shape and location.

A Mn-rich material, determined through ICP-AES analyses, is associated with the uppermost layer of the mound. This material could have formed in a hydrothermal environment or could be suggestive of bacterial activity. Another potential indicator of hydrothermal activity at this deposit is the presence of a halo structure surrounding some mineral grains at both the microscopic and SEM level. Similar structures have been described by other workers in hydrothermally altered sedimentary material.

With ongoing Sr-isotope analyses, we hope to determine the origin of this deposit, and contribute to the understanding of the pluvial history of the region.