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Implications of Reactions Between SO 2 and Basaltic Glasses for the Mineralogy of Planetary Crusts
Author(s) -
Renggli Christian J.,
Palm Andrew B.,
King Penelope L.,
Guagliardo Paul
Publication year - 2019
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2019je006045
Subject(s) - basalt , geology , olivine , sulfate , mineralogy , geochemistry , chemistry , inorganic chemistry , organic chemistry
Basalts are ubiquitous in volcanic systems on several planetary bodies, including the Earth, Mars, Venus, and Jupiter's moon Io, and are commonly associated with sulfur dioxide (SO 2 ) degassing. We present the results of an experimental study of reactions between SO 2 and basaltic glasses. We examined Fe‐free basalt, and Fe‐bearing tholeiitic and alkali basalts with a range of Fe 3+ /Fe total (0.05 to 0.79) that encompass the oxygen fugacities proposed for most terrestrial planetary bodies. Tholeiitic and alkali basalts were exposed to SO 2 at 600, 700, and 800 °C for 1 hr and 24 hr. Surface coatings formed on the reacted basalts; these contain CaSO 4 , MgSO 4 , Na 2 SO 4 , Na 2 Ca(SO 4 ) 2 , Fe 2 O 3 , Fe 3 O 4 , Fe‐Ti‐(Al)‐oxides, and TiO 2 . Additionally, the SO 2 ‐basalt reaction drives nucleation of crystalline phases in the substrate to form pyroxenes and possible Fe‐oxides. A silica‐rich layer forms between the substrate and sulfate coatings. More oxidized basalts may readily react with SO 2 to form coatings dominated by large Ca‐sulfate and oxide grains. On less oxidized basalts (NNO−1.5 to NNO−5), reactions with SO 2 will form thin, fine‐grained aggregates of sulfates; such materials are less readily detected by spectroscopy and spectrometry techniques. In contrast, in very reduced basalts (lower than NNO−5), typical of the Moon and Mercury, SO 2 is typically a negligible component in the magmatic gas, and sulfides are more likely.