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The redox state, FeO content, and origin of sulfur‐rich magmas on Mercury
Author(s) -
Zolotov Mikhail Yu.,
Sprague Ann L.,
Hauck Steven A.,
Nittler Larry R.,
Solomon Sean C.,
Weider Shoshana Z.
Publication year - 2013
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2012je004274
Subject(s) - silicate , mineral redox buffer , mercury (programming language) , sulfide , enstatite , mineralogy , chondrite , ferrous , fugacity , chemistry , geology , analytical chemistry (journal) , geochemistry , meteorite , environmental chemistry , astrobiology , mantle (geology) , physics , organic chemistry , computer science , programming language
MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) orbital observations of Mercury have revealed elevated S abundances, Ca‐S and Mg‐S correlations, and a low upper limit for ferrous iron in surface silicates. These data indicate the presence of Ca and/or Mg sulfides in volcanic rocks and a low oxygen fugacity ( f O 2 ) in their parental magmas. We have evaluated coupled f O 2 and f S 2 values and FeO contents in Mercury's magmas from silicate‐sulfide equilibria and empirical models for silicate melts and metallurgical slags. The evaluated f O 2 at 1700–1800 K is 4.5 to 7.3 log 10 units below the iron‐wüstite buffer. These values correspond to 0.028–0.79 wt % FeO, implying that Fe must be also present in sulfides and metal and are also consistent with the composition of the partial melt of an enstatite chondrite. This derived upper limit for FeO is substantially lower than the limits obtained from reflectance measurements of Mercury's surface materials. The low f O 2 and FeO values provide new constraints for igneous processes on Mercury as well as the formation, evolution, and internal structure of the innermost planet.