2:30 PM - 2:45 PM
[SGC50-04] Os isotope ratios and PGE abundances of the Pitcarn basalts: Implication for the EM-1 source
Keywords:PGE abundances, Os isotope ratio, EM-1
The Os isotope ratios for the samples with Os > 20 pg/g range from 0.135 to 0.152 and are similar to those measured in previous studies on EM-1-type basalts (~0.150 for samples with Os > 50 pg/g and ~0.180 with Os > 20 pg/g from Reisberg et al., 1993; Eisele et al., 2002; Garapic et al., 2015). The Os, Ir and Ru concentrations of the Pitcairn basalts are roughly correlated with MgO and Ni contents and tend to be lower than those of other OIB such as Hawaii and Canary Islands. Whereas Pd and Re concentration are similar to those for other OIBs. The chondrite-normalized PGE patterns of studied samples show systematic variation with or against the degree of the EM-1 flavor (e.g., decreasing of the 206Pb/204Pb and 143Nd/144Nd isotope ratios). Since crustal materials normally show large fractionation between I-PGE and P-PGE and the crustal materials have higher Os isotope ratios than mantle, the simple assimilation of crustal materials cannot explain our data. We carefully try to make an assumption of the source magma components to explain the genesis of Pitcairn Island basalts based on our data combined with previous studies.