100 Geochemistry (Posters)

EVAPORITIC AND HYDROTHERMAL GYPSUM FROM SE IBERIA: GEOLOGY, GEOCHEMISTRY, AND IMPLICATIONS FOR SEARCHING FOR LIFE ON MARS

Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

In the Mediterranean region, the Upper Miocene was a time of convergence and interaction of different geological processes including tectonism, volcanic activity, hydrothermalism and desiccation of the Mediterranean Sea. The Messinian salinity crisis probably was the most outstanding geological event of the late Cenozoic. The giant evaporitic (anhydrite/gypsum) sequence is well represented in the stratigraphic record and consists of several crises that fit the context of catastrophic modeling of a Mediterranean "saline giant".

The Cuevas del Almanzora (CA) geological section (Vera basin, western Mediterranean, SE Iberia) is one of the best biostratigraphic successions in which to document terminal Miocene events. Likewise, the CA area hosts a volcanics-related, stratabound-type mineral deposit (barite and Fe-(±Mn) oxides and hydroxides), which is capped by the largest exhalite deposit in Spain (alternating beds of barite, jasper and gypsum with tiny inclusions of hematite and sulfides). Hydrothermal gypsum veins are also found cutting the volcanic rocks.

Gypsum occurs in some Martian meteorites (e.g. Governador Valadares, Nakhla), and a Martian analog to the Earth's salt pans and saline lakes of arid regions may have existed in crater-basins during Mars' early (Noachian) epoch. Also, it has been suggested that, at a P-CO2 of several bar, gypsum precipitation could occur before calcite upon evaporation, if the initial SO42-:Ca2+ ratio is high and there is no water recharge. An evaporite setting for crater-basins on Mars has significant implications for the geological and even biological processes that could eventually be operating. Likewise, hydrothermal systems were probably present on the planet, and could have served as a habitat for primitive life.

The comparison of the geology and geochemistry of these two types of sulfate-rich systems (evaporitic and hydrothermal) which were active in CA can be used for the astrobiological exploration of Mars.