CHEMICAL FRACTIONATIONS IN METEORITES. II. ABUNDANCE PATTERNS AND THEIR INTERPRETATION.

摘要: Abstract Abundances of thirty-one volatile elements in meteorites are reviewed. In carbonaceous chondrites Types I, II, and III enstatite Type abundances decrease by constant factors, ratios 1/0·6/0·3/0·7. ordinary II chondrites, nine (Au, Cu, F, Ga, Ge, S, Sb, Se Sn) likewise depleted factors ~0·25 ~0·5, while eighteen others (Ag, Bi, Br, C, Cd, Cl, Cs, H, Hg, In, Kr, N, Pb, Te, Tl, Xe Zn) show more drastic depletions, to 0·002. Apparently a mixture two types material: low-temperature fraction (= matrix) that retained most its volatiles high-temperature chondrules, metal grains) lost them. Evidence is presented these fractionations occurred the solar nebula as it cooled from high temperatures. They cannot have been produced meteorite parent bodies. The following accretion temperatures inferred abundance patterns: ≤400 °K; I 400–480 530–650 °K, unequilibrated ≤530 °K. These much higher than present black-body temperature asteroid belt, 170 However, they could reached during collapse or high-luminosity, pre-main-sequence stage protosun. This model also accounts for presence organic compounds primordial noble gases meteorites; extreme depletion chondrites; low alkali content earth chondrites. tentative distance assignments given: come inner fringe belt; center half; form outer comets.