PU-244 FISSION XENON AND PRIMORDIAL XENON IN THE ALLENDE METEORITE

The carbonaceous chondrite Allende contains (22+/-1). 10(-12) cm(3)STP /g of Pu-244 fission xenon and two kinds of primordial xenon: Type I a nd Type ii. The former represents the isotopic composition of a primor dial xenon, which resided in the vicinity of a supernova shortly befor e it exploded, white the latter represents that of the xenon, which re sided in the supernova. The isotopic composition of xenon found in the pink inclusion of the Allende meteorite, corrected for the presence o f very large excesses of Pu-244 fission xenon, Xe-129 from the decay o f I-129, and of Xe-128 from the neutron-capture reactions on I-127, re sembles that of Type-I primordial xenon. The isotopic composition of x enon found in the diamond inclusions of the Allende meteorite, on the other hand, represents that of Type-II primordial xenon and it resembl es that of a mixture of Type-I primordial xenon whose isotopic composi tion is severely altered by a combined effect of(a) mass-fractionation , (b) spallation, (c) stellar-temperature neutron-capture reactions, a nd (d) the presence of a large excess of Pu-244 fission xenon.