| Magmatic volatiles, specifically water, fluorine, chlorine and sulfur, play important and diverse roles in silicate melts by controlling many physiochemical processes such as thermal stabilities of minerals and melts, melt density and viscosity, magma eruptive processes, and the formation of hydrothermal fluids that transport economically important metals. Some of these volatiles, perhaps most notably water, likely play a crucial role in the origin of life. Although the terrestrial magmatic volatile budget is well constrained, much remains uncertain about the martian volatile budget. Mars has commonly been referred to as a "volatile-rich" planet, and there is little doubt about the presence of frozen water-ice at the martian poles and abundant Cl and S in rocks, soils and dust. Yet, contradictory information abounds, particularly regarding magmatic water contents and the accepted mantle water budget for Mars.This body of work provides the first studies focused on assessing the volatile budget of martian magmas and exploring the implications of these volatiles on ancient martian igneous and hydrothermal systems. We report, through textural analysis and electron probe microanalysis (EPMA) of minerals in martian meteorites, strong evidence for water, F, and Cl-bearing magmas and strong evidence for both water-rich and chlorine-rich hydrothermal fluids in martian magmatic systems. We collected new secondary ion mass spectrometry (SIMS) data on kaersutite from the Chassigny meteorite, which we use to show that at least some magma source regions on Mars likely have water contents similar to terrestrial values. In order to show that low-OH F-Cl apatite analyses obtained from the Chassigny meteorite are viable compositions (these compositions are rare in terrestrial rocks), low-OH F-Cl apatite was synthesized and characterized by EPMA, single-crystal X-ray diffraction and various nuclear magnetic resonance (NMR) techniques. Finally, the effect of water on the compositional diversity of magmas that can be produced from fractionation of a martian liquid at the base of a thick crust was investigated experimentally. Using a synthetic powder modeled after Humphrey (a picrobasalt analyzed in Gusev Crater, Mars), we verified the possibility of igneous crustal stratification, which does not require large-scale lithologic diversity among rocks on the martian surface. |
