147SM-143ND AND 87RB-87SR AGES OF THE EUCRITE PIPLIA KALAN - A PRELIMINARY STUDY

Abstract

Prompted by the finding that the eucrite Piplia Kalan could have retained Pu fission Xe earlier than the eucrites so far studied and hence be very ancient, we have measured a precise internal 147Sm-143Nd isochron for this meteorite. The age and initial Nd ratio relative to CHUR are 4.570 +/- 0.023 Ga and -1.3 +/- 0.7 εu, respectively. A Rb-Sr whole rock (clast) isochron for this meteorite corresponds to an age of 3.963 +/- 0.119 Ga and initial 87Sr/86Sr ratio of 0.69902 +/- 3. But initial 87Sr/86Sr ratio calculated for an age of 4.57 Ga is 0.698956 +/- 25, which is indistinguishable from 0.698970 +/- 15 reported for the angrites LEW and ADOR dated at 4.5578 +/- 0.0005 Ga. These results indicating that Piplia Kalan could have formed within only a few million years of the earliest condensates in the Solar System are strongly supported by the recent discovery of live 26Al in it.