Further measurements on isotopic anomalies of 196Hg/202Hg ratio in some of acid insoluble residues of Sikhote Alin and other iron meteorites.

Abstract

In residues of several iron meteorites, obtained by dissolution of a metal piece in 2M H2 SO4i isotopic ratio of 196Hg/2o2Hg has been measured by radiochemical neutron activation analysis in Hg frac tions, released by stepwise heating. Both positive and negative deviations relative to terrestrial composi tion, have been found. Anomalies are more frequently observed in the high temperature fractions (200<T<600°C) as compared to the low temperature distillates (T<_200°C). The largest deviations so far seen are, respectively, enrichment of 116 Hg by 67% in a 400°C fraction of Carlton and depletion of the same isotope by 86% in a 300°C fraction of Sikhote Alin residue (magnetic) of < 38 ,um grain size.The anomalous components appear to be sporadic and heterogeneously distributed. A lack of homogenisation of the two isotopes that are produced in different nucleosynthetic processes suggests that iron meteorites have been formed in a non-magmatic process, entrapping presolar grains. Alter natively, some foreign materials presumably of different isotopic compositions might have been in troduced in meteorite parent bodies during their collisions with other cosmic objects and or dense cloud of interstellar dust.

Search for p-isotopic anomaly of cerium in the bulk Allende meteorite.

“…Jorgensen (1988) proposed that Xe-HL which is produced in a type I supernova of a white dwarf is implanted into the diamond produced in a carbon star in the case where both stars belong to the same double star system. acid residues of Sikhote Alin and other iron mete orites (Thakur and Goel, 1989;Kumar and Goel, 1992b); the Moon and achondrite samples (Jovanovic and Reed, 1990) as well as in stone meteorites (Kumar and Goel, 1992a). The p-iso topic anomalies of 1840s are found in stone mete orites and acid residues of the Sikhote Alin iron meteorite.…”

Determination of 190Os/184Os ratio in the carbon-rich residues of stone meteorites by neutron activation method combined with fire-assay technique.

“…Osmium isotopic anomalies found in bulk and sieve frac tions of stone meteorites (Kumar and Goel, 1991) could be a contribution of materials like CR-resi dues. Furthermore, residues of iron meteorites have shown Os isotopes anomalies (Goel and Murthy, 1983;Goel, 1987;Kumar and Goel, 1992b), which are suggestive of existence of presolar materials. Walker and Morgan (1989) have reported that some samples of Semarkona and Murray plot 4 6% above the iron meteorite isochron (Re-Os systematics), well above the field delineated by other chondrites, which indicate that these mete orites either accumulated from isotopically het erogeneous materials or that Re was leached at some stage following their accretion.…”

Historical Variations in the Stable Isotope Composition of Mercury in Arctic Lake Sediments

“…However, the possibility that the proportions of the stable isotopes of Hg vary significantly in nature has rarely been investigated. Evidence for natural fractionation of Hg isotopes has been found in Hg ores (9)(10)(11) and in meteorites and moon rocks (12)(13)(14), and, although doubts about these findings have been raised (15), the existence of differences in Hg isotope content among samples of Hg ore from different sources has been confirmed (16). Yet comparison of coal and fly ash samples yielded negative results (17).…”