Other
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p51a0902d&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P51A-0902
Other
3672 Planetary Mineralogy And Petrology (5410), 5410 Composition (1060, 3672), 5480 Volcanism (6063, 8148, 8450), 6225 Mars, 8450 Planetary Volcanism (5480, 6063, 8148)
Scientific paper
There is significant geochemical evidence for assimilation of crustal material into sub-aerial, mantle-derived, terrestrial basaltic magmas. Some of the most powerful constraints on crustal assimilation come from oxygen isotope studies, because supracrustal rocks often have distinct 18O/16O ratios resulting from interaction with Earth's hydrosphere. From a planetary perspective, studies of carbonate concretions from meteorite ALH84001 have yielded evidence for low-temperature crustal interaction at or near the surface of its putative parent body, Mars. This finding raises the possibility that crustal assimilation processes may be tracked using oxygen isotopes in combination with geochemical data of other reputed martian (SNC) meteorites. The whole-rock oxygen isotope ratios (Laser fluorination δ18O = +4.21 to +5.85‰ VSMOW) of SNC meteorites, correlate with aspects of their incompatible element chemistry. Some of the oxygen isotope variability may be explained by post-magmatic alteration on Mars or Earth; however, it appears, based on petrographic and geochemical observations, that a number of SNC meteorites, especially Shergottites, retain the original whole-rock oxygen isotope values of their magmas prior to crystallisation. Correlations between oxygen isotopes and incompatible element geochemistry are consistent with assimilation of a high-18O/16O, incompatible-element rich, oxidizing crustal component by hot, mantle-derived magmas (δ18O = ~~4.2‰). A crustal component has previously been recognized from Sr-Nd-Os isotope systematics and oxygen fugacity measurements of SNC meteorites. Oxygen isotope evidence from SNC meteorites suggests high-18O/16O crustal contaminants on Mars result from low temperature (< 300°C) interaction with martian hydrosphere. The extent of apparent crustal contamination tracked by oxygen isotopes in SNC meteorites implies that the majority of martian crust may have undergone such interactions. Evidence for assimilation of high 18O/16O crust has important implications for 1) the oxygen isotope composition of the martian mantle; 2) the correct identification of martian surface Type-2 and; 3) the existence and longevity of the water-cycle on Mars.
Day J. M.
Spicuzza Michael J.
Taylor Lawrence A.
Valley John W.
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