Uranium–lead isotope systematics of Mars inferred from the basaltic shergottite QUE 94201

Evolution of the martian mantle inferred from the 187Re–187Os isotope and highly siderophile element abundance systematics of shergottite meteorites

“…They concluded this based on the fact that terrestrial common Pb lies on (or nearly so) each of the secondary isochrons on the low 207 Pb/ 206 Pb-204 Pb/ 206 Pb side of each line. They also noted that 238 U-206 Pb systematics give a concordant age with the 87 Rb-87 Sr, 147 Sm-143 Nd internal isochrons for the shergottite Zagami, which is unlikely to occur via post-secondary igneous processes Gaffney et al, 2007). Jagoutz (1991) offered another possible interpretation of the secondary 207 Pb-206 Pb isochrons, concluding that they reflect closure ages for an event in the shergottite source region, similar to the bulk-rock apparent isochron of ca.…”

“…Young crystallization ages of shergottites have been questioned on the basis of 207 Pb-206 Pb secondary isochron ages that range from 4.1 to 4.3 Ga for Zagami, Los Angeles, EETA 79001, and Shergotty (Bouvier et al, 2005(Bouvier et al, , 2008a(Bouvier et al, ,b, 2009Gaffney et al, 2007). Bouvier et al (2005Bouvier et al ( , 2008aBouvier et al ( ,b, 2009) interpreted these secondary 207 Pb-206 Pb isochron ages to be igneous crystallization ages.…”

“…Gaffney et al (2007) interpreted secondary Pb isochron ages to reflect incomplete removal of modern terrestrial Pb by leaching from the mineral fractions analyzed. They concluded this based on the fact that terrestrial common Pb lies on (or nearly so) each of the secondary isochrons on the low 207 Pb/ 206 Pb-204 Pb/ 206 Pb side of each line.…”

39Ar–40Ar ages of martian nakhlites

“…Unlike martian shergottites, whose formation ages appear to vary considerably (Nyquist et al, 2001;Gaffney et al, 2007;Bouvier et al, 2008), the nakhlites appear to have very similar, if not identical radiometric ages of $1.3 Ga. Nyquist et al (2001) summarized for Nakhla, Lafayette, and Governador Valadares radiometric ages measured by various techniques, which span the range 1.19 ± 0.02 Ga to 1.37 ± 0.02 Ga. These authors gave ''preferred" ages of Nakhla = 1.27 ± 0.01 Ga, Lafayette = 1.32 ± 0.02 Ga, and Governador Valadares = 1.33 ± 0.01 Ga.…”

Experimental study of polybaric REE partitioning between olivine, pyroxene and melt of the Yamato 980459 composition: Insights into the petrogenesis of depleted shergottites

“…Bouvier et al (2005Bouvier et al ( , 2008b reported a $4.1 Ga date on the basis of 207 Pb-206 Pb whole rock data and interpreted it as the crystallization age of shergottites. This 'ancient' shergottite age could either represent the contamination by terrestrial Pb (e.g., Gaffney et al, 2007), disturbance of the U-Pb system or, in the view of our model, timing of the U-Pb system closure in the Deep Mantle and Nakhlite Sources.…”