Re-Os isotope geochemistry of three Chinese chondrites

Three Chinese ordinary chondrites,including Jilin (H5),Boxian (LL3.8) and Lujiang (LL6),have been studied for their Re and Os abundances and Os isotopic composition in whole-chondrite samples,separated magnetic and nonmagnetic fractions,and nodules. The results indicate that the Re and Os abundances of the whole-chondrite samples are in the ranges of corresponding H-and LL-Groups,respectively. The Re and Os abundances of magnetic fraction from Boxian and Lujiang are within the range of high-Os ⅡAB and ⅢAB irons,whereas those of nonmagnetic fractions of Boxian and Lujiang are lower than the whole-chondrite values. The Re and Os abundances of nodules in Jilin are in the range of the LL-Group. 187Re/188Os and 187Os/188Os ratios of the three whole chondrites are in the range of ordinary chondrites which locate around the isochron of ⅡAB+ⅢAB irons. 187Re/188Os and 187Os/188Os ratios of the magnetic and nonmagnetic fractions from Boxian have a larger difference. The nonmag-netic fraction of Lujiang may contain a recent addition of Re,which causes deviation of the 187Re/188Os ratio from the irons isochron. The Re and Os abundances of nodules in Jilin are lower than those of the whole-chondrite,but their 187Os/188Os ratios are higher than that of the whole chondrite.

Three Chinese ordinary chondrites, including Jilin （H5）, Boxian （LL3.8） and Lujiang （LL6）, have been studied for their Re and Os abundances and Os isotopic composition in whole-chondrite samples, separated magnetic and nonmagnetic fractions, and nodules. The results indicate that the Re and Os abundances of the whole-chondrite samples are in the ranges of corresponding H- and LL-Groups, respectively. The Re and Os abundances of magnetic fraction from Boxian and Lujiang are within the range of high-Os IIAB and IIIAB irons, whereas those of nonmagnetic fractions of Boxian and Lujiang are lower than the whole-chondrite values. The Re and Os abundances of nodules in Jilin are in the range of the LL-Group. ^187Re/^188Os and ^187Os/^188Os ratios of the three whole chondrites are in the range of ordinary chondrites which locate around the isochron of IIAB＋IIIAB irons. 187Re/1SSOs and ^187Os/^188Os ratios of the magnetic and nonmagnetic fractions from Boxian have a larger difference. The nonmagnetic fraction of Lujiang may contain a recent addition of Re, which causes deviation of the ^187Re/^188Os ratio from the irons isochron. The Re and Os abundances of nodules in Jilin are lower than those of the whole-chondrite, but their ^187Os/^188Os ratios are higher than that of the whole chondrite.