Evidence for a late thermal event of unequilibrated enstatite chondrites: A Rb‐Sr study of Qingzhen and Yamato 6901 (EH3) and Khairpur (EL6)

摘要: — The Rb-Sr whole rock and internal systematics of two EH3 chondrites, Qingzhen Yamato 6901, one EL6 chondrite, Khairpur, were determined. Sulfides separated using a stepwise dissolution technique. mineral species in each fraction estimated based on the chemical analyses 12 major elements. chondrites are highly disturbed. Fractions corresponding to sulfide phases show excess 87Sr, while other fractions silicate produce linear trend evolution diagram. If these relations interpreted as isochrons, ages 2.12 ± 0.23 Ga 2.05 0.33 with initial Sr isotopic ratios 0.7112 0.0018 0.7089 0.0032, for respectively. process disturbance probably involved breakdown K-bearing (djerfisherite), lack exchange between indicates moderate temperatures reheating. Although complete re-homogenization among was not attained, we interpret results indicative late thermal event about 2 ago parent bodies chondrites. These agree well previously published K-Ar ages. An older isochron age 4.481 0.036 low ratio 0.69866 0.00038 obtained data from indicating early petrological equilibration body