Geochemistry of Mineral-Water Interactions in Basaltic Lava Caves as Earth Analogs (Screen 4)

Basaltic lava caves are important Earth analogs in our search for life on Mars and other planets. Terrestrial lava caves exhibit morphologically diverse secondary mineral deposits (speleothems) often associated with liquid water. The detailed geochemical characterization of cave water and speleothems can provide valuable insights on potential biotic or abiotic mechanisms that lead to formation of these features. Our results showed that the cave water chemistry is consistent with basaltic host rock chemical composition. The water contained high levels of dissolved organic carbon and nitrogen, which could support microbial growth. The dissolved organic matter showed macromolecular structure and appears to be plant-derived, highly humified and microbially processed. Elevated nitrate in cave water may be due to agriculturally influenced regional surface water source or in situ oxidation of ammonia or organic N. Speleothems contained 29-79 wt% of crystalline, cryptocrystalline, or amorphous SiO2, and secondary...