Germanium Enrichments in Sedimentary Rocks in Gale Crater, Mars: Constraining the Timing of Alteration and Character of the ProtolithRocks enriched in Ge have been discovered in Gale Crater, Mars, by the Alpha-particle X-ray spectrometer (APXS) on the Mars Science Lab (MSL) rover, Curiosity. The Ge concentrations in Gale Crater (commonly >50 ppm) are remarkably high in comparison to Earth, where Ge ranges from 0.5-4.0 ppm in igneous rocks and 0.2-3.3 ppm in siliciclastic sediment. Primary meteoritic input is not likely the source of high Ge because Ge/Ni in chondrites (approx.0.003) and irons (<0.04) is lower than in Gale rocks (0.08-0.2). Earth studies show Ge is a useful geochemical tracer because it is coherent with Si during magmatic processes and Ge/Si varies less than 20% in basalts. Ge and Si fractionate during soil/regolith weathering, with Ge preferentially sequestered in clays. Ge is also concentrated in Cu- and Zn-rich hydrothermal sulfide deposits and Fe- and Mnrich oxide deposits. Other fluid-mobile elements (K, Zn, Cl, Br, S) are also enriched at Gale and further constrain aqueous alteration processes. Here, we interpret the sediment alteration history and present a possible model for Ge enrichments at Gale involving fluid alteration of the protolith.
Document ID
20150001960
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Berger, J. A. (University of Western Ontario London, Ontario, Canada)
Schmidt, M. E. (Brock Univ. Saint Catherines, Ontario, Canada)
Gellert, R. (Guelph Univ. Ontario, Canada)
Campbell, J. L. (Guelph Univ. Ontario, Canada)
Boyd, N. I. (Guelph Univ. Ontario, Canada)
Elliott, B. E. (New Brunswick Univ. Fredericton, New Brunswick, Canada)
Fisk, M. R. (Oregon State Univ. Corvallis, OR, United States)
King, P. L. (Australian National Univ. Canberra, Australia)
Ming, D. W. (NASA Johnson Space Center Houston, TX, United States)
Perrett, G. M. (Guelph Univ. Ontario, Canada)
Thompson, L. M. (New Brunswick Univ. Fredericton, New Brunswick, Canada)
VanBommel, S. J. (Guelph Univ. Ontario, Canada)
Yen, A. (California Inst. of Tech. Pasadena, CA, United States)