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Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region
Author(s) -
Viviano Christina E.,
Moersch Jeffrey E.,
McSween Harry Y.
Publication year - 2013
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/jgre.20141
Subject(s) - noachian , protolith , geology , geochemistry , carbonation , carbonate , carbonate minerals , mineralogy , hydrothermal circulation , saponite , brucite , mafic , magnesite , mars exploration program , clay minerals , martian , chemistry , astrobiology , magnesium , paleontology , metamorphic rock , calcite , physics , organic chemistry
Previous identification of serpentine and magnesium carbonate in the eastern Nili Fossae region of Mars indicates hydrothermal alteration of an olivine‐rich protolith. Here we characterize Fe/Mg phyllosilicates associated with these units and present spectral evidence for the presence of a talc component, distinguishable from saponite. Locations with magnesium carbonate are exclusively associated with talc‐related phyllosilicates. In the westernmost portions of the Nili Fossae region, where a mafic protolith dominates, Fe/Mg phyllosilicates display spectral evidence for a wide degree of chloritization. We propose that Noachian Fe/Mg smectites were uniformly buried by Hesperian lava flows that initiated hydrothermal alteration in the eastern Nili Fossae region. The chloritization of smectites may have produced silica‐rich fluids necessary for the serpentinization of olivine; temperature and depth constraints indicated by their distribution also suggest a hydrothermal system was present. The subsequent carbonation of serpentine and/or olivine in eastern Nili Fossae, while requiring an additional CO 2 source, provides an explanation for the limited occurrence of serpentine and the colocation of carbonate and talc‐bearing material throughout this area. The consequence of the hypothesized carbonation reaction and the presence of serpentine provides geochemical constraints for the proportion of CO 2 present in the fluids that interacted with the protolith. If this carbonation reaction was a widespread phenomenon, it may have been an important process in the ancient Martian carbon cycle and could have provided a sink for CO 2 in the past.