The age of Dar al Gani 476 and the differentiation history of the martian meteorites inferred from their radiogenic isotopic systematics

Chemical compositions of martian basalts (shergottites): Some inferences on b; formation, mantle metasomatism, and differentiation in Mars

“…Here, these groupings by REE patterns are generalized to the whole of G1 and G2 elements-regularities in the REE patterns of shergottites must be seen in light of the broad scope of G1 and G2 element groups. These shergottite families are also evident in Sm-Nd isotopic ratios and in oxygen fugacities (Borg et al , 2003Herd et al 2002).…”

“…Second, new radioisotopic data on the shergottites, especially on those critical samples, have resolved several uncertainties in their petrogenesis. Since the definitive works listed above, the crystallization ages of the shergottites have been firmly established: most at ~180 Ma, QUE 94201 at 327 Ma, and DaG 476 at 474 Ma (Borg et al 1997(Borg et al , 2003. Consideration of initial radioisotopic ratios has led to the recognition that Mars underwent an extreme geochemical fractionation very early in its history and, thus, that the chemical compositions of the shergottites need not represent only recent fractionations.…”

39Ar‐40Ar “ages” and origin of excess 40Ar in Martian shergottites

“…The formation ages of many shergottites have been determined from the Sm-Nd, Rb-Sr and U-Pb radiometric systems (Borg et al 2001(Borg et al , 2003(Borg et al , 2005Nyquist et al 2001a;Shih et al 2003Shih et al , 2005Shih et al , 2007Bouvier et al 2005;Misawa et al 2006aMisawa et al , 2008. Most dated basaltic shergottites and a few lherzolitic shergottites give formation ages of approximately Ma.…”

Science Priorities for Mars Sample Return

“…MSR (e.g. McPherson et al, 2001; Wadhwa, 2001;Borg et al, 2003;Symes et al, 2008;Shearer et al, 2008) and subsequent evolution of the crust, mantle, and core (e.g. Treiman, 1990;Shearer et al, 2008).…”

“…Gooding et al 1991, McKay et al 1996, Bridges et al 2001. Although the trace element and isotopic variability of the Martian meteorite suite far exceeds that observed in equivalent suites of basalts from Earth and Moon (Borg et al, 2003) (Schultz and Mustard, 2004), volcanic ash (Wilson and Head, 2007) , 2, 3, 4, 6, 7, 8 ( (Davis, 1998;NRC, 2002;Jones et al, 2004 (Warmflash et al, 2007 10. Interpret the initial composition of the Martian atmosphere, the rates and processes of atmospheric loss/gain over geologic time, and the rates and processes of atmospheric exchange with surface condensed species.…”