Mineralogical and Geochemical Trends in Mini-Cores from Carbonate Seep Deposits in a Mars Analog Serpentinizing Environment

Serpentinization-driven subsurface habitats such as those found within the mafic-ultramafic Coast Range Ophiolite express diagnostic surface assemblages. This unique suite of precipitated and weathered materials includes carbonate cements (travertines) of varying chemistry deposited by seeping alkaline (pH up to 12) fluids. Ongoing studies suggest that alkaline springs and their associated mineralizations are direct surface expressions of presently occurring serpentinization reactions in the subsurface. As such, the springs can potentially shed light on the microbial diversity in the subsurface biosphere as well (Brazelton et al., 2011). This report includes a compilation of mineralogical and geochemical analyses of miniature rock cores (1" x 10"), taken within such seeps, with inferences into the nature of the depositional environment and subsurface conditions. The site locality is the UC Davis McLaughlin Natural Reserve, Lower Lake, CA, and surrounding areas, well within the Coast Range Ophiolite body. X-Ray diffraction, Scanning Electron Microscopy and petrographic evaluations were the most effective analyses on the cores. The travertine had undergone meteoric diagenesis due to heterogenous mixings of alkaline seep fluids and percolating waters at or near the surface. These alkaline springs and their carbonate deposits are an important analog for potentially biologic systems, and further studies suggest that the carbonates in particular may serve as a biosignature that may be very useful in searching for evidence for early life and life on Mars.