FUMAROLES ON MARS: UNDERSTANDING THE POTENTIAL EFFECTS OF MAGMA DEGASSING ON SURROUNDING ROCK AND MELT CHEMISTRY

Much of the Martian surface shows both morphologic and mineralogical evidence of aqueous alteration. Orbital, and ground-based measurements of Martian soil have identified many areas of phyllosilicates, which, on Earth, are most commonly formed from weathering of rock. Yet, much of the alteration on Mars likely took place at low water/rock ratios. Therefore, we will explore the possibility that volcanic fumaroles are responsible for producing some of the observed alteration assemblages, and determine how a degassing magma will change composition in response to loss of water and halogens.

Using oxides and silicates, a typical Martian basalt (Irvine) is synthesized at pressure, with aliquots containing excess water, sulfur, and chlorine produced. These “magmas” are then brought to surface pressures, melted, and are allowed to degas in the presence of basaltic rocks and minerals (olivine, pyroxene, plagioclase, etc). Volcanic vapors interact with mineral samples at elevated temperatures, effectively altering them, changing their spectral signature- through a combination of deposition of sublimates and chemical alteration of the target. Analyses of vapor deposits using ICP-MS, indicates transport of Fe, Au, Zn, and Cl from the magma. EMPA of residual liquids indicate a loss of Fe, Mg, Na and K from the melt. Raman analysis of altered olivine and pyroxene suggest the formation of Fe-chlorides and sulfides at the surface these grains. XRD and SEM will be employed to determine precise mineralogy and morphology of any new phases.