Origin of the depletion of siderophile volatile elements in Earth, Mars and the aubrite parent body

• Applicant: Professor Dr. Harry Becker
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 242130583

• Final Report Year: 2016

Final Report Abstract

Approximately chondritic HSE ratios indicate that Earth, Mars and the parent body of Aubrites have undergone the addition of late accretion after core formation. The distinct behavior of S, Se and Te in the mantle of Earth and Mars suggest the different volatile element compositions of late accreted material on Mars and Earth, strongly volatile element-depleted on Mars, and volatile element-rich on Earth. Thus, delivery of Martian water from carbonaceous chondrite-like materials must have occurred before accretion of the Martian late veneer, likely within 2-3 million years after formation of the solar system, and implies that water was retained during early planetary growth. The volatile depletion of the precursors of planetary bodies during the predominant accretion period is not simply followed canonical condensation trends as in undifferentiated carbonaceous chondrites. Instead, the delivery and fractionation history of volatile elements vary among differentiated solar system objects and the accreted materials may have distinct volatile element depletion contents, out of our meteorites collection, like Earth. The limited fractionation of some siderophile volatile element pairs such as Cu and Ag during planetary differentiation, in combined with high P-T experimental data, could provide new perspectives to understand the volatile element composition of accreted materials. The new results also indicate that the Martian mantle and core contain low sulfur contents, in strong contrast to the widely used assumptions 5. If confirmed, the conclusion will have significant implications for the conditions of Martian core formation, the evolution of the physical state of the Martian core and the origin and transient occurrence of the magnetic field that shielded the early atmosphere and liquid water on the early Martian surface from the solar wind.

Publications

• (2014) Abundances of sulphur, selenium, tellurium, rhenium and platinum group elements in eighteen reference materials by isotope dilution sector-field ICP-MS and negative TIMS. Geostandards and Geoanalytical Research, 38, 189-209
  Wang, Zaicong & Becker, Harry
  
• (2015) Mass Fractions of S, Cu, Se, Mo, Ag, Cd, In, Te, Ba, Sm, W, Tl and Bi in Geological Reference Materials and Selected Carbonaceous Chondrites Determined by Isotope Dilution ICP-MS. Geostand. Geoanal. Res. 39, 185-208
  Wang, Zaicong; Becker, Harry & Wombacher, Frank
  
• (2015) Abundances of Ag and Cu in mantle peridotites and the implications for the behavior of chalcophile elements in the mantle. Geochim. Cosmochim. Acta 160, 209-226
  Wang, Zaicong & Becker, Harry
  
• (2015) Comment on “A non-primitive origin of near-chondritic S-Se-Te ratios in mantle peridotites: Implications for the Earth's late accretionary history” by König S. et al. [Earth Planet. Sci. Lett. 385, 110–121]. Earth Planet. Sci. Lett. 417, 164-166
  Wang, Zaicong & Becker, Harry
  
• (2015) Fractionation of highly siderophile and chalcogen elements during magma transport in the mantle: Constraints from pyroxenites of the Balmuccia peridotite massif. Geochim. Cosmochim. Acta 159, 244-263
  Wang, Zaicong & Becker, Harry
  
• (2016) Earth's moderately volatile element composition may not be chondritic: Evidence from In, Cd and Zn. Earth Planet. Sci. Lett. 435, 136-146
  Wang, Zaicong; Laurenz, Vera; Petitgirard, Sylvain & Becker, Harry