Thermal metamorphism of primitive meteorites

Neutron activation data are reported for Ag, As, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Se, Te, Tl and Zn in samples of Abee heated at temperatures of 1000 to 14000C in a low-pressure environment and in 9 enstatite achondrites (aubrites) and the silicate portion of the unique stony-iron, Mt. Egerton. Trace element losses in heated Abee progress with temperature, the lowest retention being 2.4 x 10-6 of initial contents. These data indicate trace element loss above 10000C via diffusion-controlled processes having apparent activation energies of 8 to 55 kcal/mol; only Co exhibits a significantly higher energy. These trace element data and those for aubrites, Mt. Egerton and E4-6 chondrites, and mineralogic and isotopic evidence link all enstatite meteorites to a common parent body. Volatile/mobile elements vary inversely with cobalt content in aubrites and Mt. Egerton but directly in E4-6 chondrites. The results are discussed. (author)