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Gros, J.

Publications and source records attributed to Gros, J..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Ries impact crater, southern Germany - Search for meteoritic material

Twenty-three samples covering a wide range of shock metamorphism from the Ries impact crater in southern Germany were analyzed for siderophile and volatile elements in order to determine the chemical nature of the impacting meteorite. Slight enrichments in the siderophile elements Ir and Os above the indigenous level of 0.015 ppb were observed in only eight samples, including a shocked, metal-bearing amphibolite and two weakly shocked biotite gneisses, whereas those samples expected to contain meteoritic material (heavily shocked glasses) do not exhibit a perceptible siderophile enrichment. The Ir, Os and Ni enrichments of the metal bearing amphibolite are found to be compatible with chondritic ratios, while in the other enriched samples, Ir, Ni and Se relationships suggest an achondritic meteoritic origin. An aubritic projectile is concluded to be most compatible with the data.

Morgan, J. W.↗
NASA NTRS1978

Volatile elements in chondrites - Metamorphism or nebular fractionation

Three of the most highly metamorphosed meteorites of their respective classes, Shaw (LL7), Karoonda (C5), and Coolidge (C4), were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Comparison with data by Lipschutz and coworkers (1977) on artificially heated primitive meteorites shows that the natural metamorphism of meteorites cannot have taken place in a system open to volatiles. Shaw, metamorphosed at 1300 C for more than 1 million yr, is less depleted in In, Bi, Ag, Te, Zn, and Tl than Krymka heated at 1000 C for 1 week. Karoonda, metamorphosed at 600 C for many millennia, is less depleted in Bi and Tl than Allende heated at 600 C for 1 week. Data on primordial noble gases also show that the volatile-element patterns of ordinary and carbonaceous chondrites were established by nebular condensation and changed little, if at all, during metamorphism. For enstatite chondrites, the evidence is still incomplete but seems to favor a nebular origin of the volatile pattern.

Takahashi, H.↗
NASA NTRS1977

Noble gases in separated meteoritic minerals - Murchison /C2/, Ornans /C3/, Karoonda /C5/, and Abee /E4/

The distribution of all five noble gases was measured in four meteorites of different classes by mass spectrometry and stepwise heating of HCl-HF-insoluble residues and of samples treated with HNO3 and atomic oxygen. The distribution of the gases among the three main phases, chromite, polymer, and the ill-defined Q-phase, was determined, and also the isotopic distribution of the gases in the phases was obtained.

Srinivasan, S.↗
NASA NTRS1977

Gas-rich minerals in the Allende meteorite - Attempted chemical characterization

A ten-step etching experiment with HNO3 was performed on a chromite-carbon residue from Allende, in order to characterize the HNO3-soluble minor phase 'Q' that contains most of the primordial Ar, Kr, and Xe. Each etch fraction was analyzed by neutron activation analysis for Cr, Fe, Co, Ir, and Au. The results suggest that Q consists of two minerals, each comprising about 5 per cent of the residue. Phase Q1, of Fe/Cr ratio greater than 20, is soluble in cold dilute HNO3 and seems to contain most of the heavy noble gases. It may be an HCl-insoluble sulfide of nominal composition (Fe84Ni12Cr4)Sx. Phase Q2, of Fe/Cr ratio about 0.5 and somewhat enriched in Co, is slowly soluble in hot concentrated HNO3 and seems to be at least an order of magnitude poorer in heavy noble gases than Q1. It may be daubre-elite or an acid-soluble variety of chromite.

Gros, J.↗
NASA NTRS1976

Meteorite-free Apollo 15 crystalline KREEP

Electron microprobe and petrographic analyses of an Apollo 15 sample, 15382, from the Apennine Front, have revealed KREEP chemistry and very low concentrations of the characteristic meteorite siderophile elements: Ir, Os, Re, Au, and Ni. It is a crystalline basalt, practically identical in texture and mineral zoning patterns to other lunar high-alumina basalts.

Dowty, S.↗
NASA NTRS1976

Composition of the projectiles that bombarded the lunar highlands

Twenty highland samples from Apollo 14, 15, and 17 and the eucrites Juvinas and Morre County were analyzed by radiochemical neutron activation for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. The meteoritic components of 82 highland rocks were recalculated with the new corrections for the indigenous contribution and were classified by discriminant and cluster analysis as well as ternary diagrams, using Ir, Re, Au and Ni as diagnostic elements. To characterize these groups more fully, average abundances of meteoritic volatiles (Sb, Ge, Ag, Se, Te, and Bi) were calculated from regressions against Ir.

Gros, J.↗
NASA NTRS1975

Extinct superheavy element in the Allende meteorite

Radiochemical neutron activation analysis of seven Allende samples for 26 trace elements were conducted. In addition, Cr and Fe were studied with the aid of instrumental neutron activation analysis. The investigation had the objective to identify the extinct superheavy element which was present in meteorites and decayed to Xe isotopes by spontaneous fission. The superheavy element was found to reside mainly in a rare mineral (probably a Fe, Ni, Cr, Al-sulfide), comprising only 0.04% of the meteorite. It is pointed out that of the nine volatile superheavy elements 111 to 119, only 115, 114, and 113 are expected to condense as sulfides in the temperature interval between 400 and 500 K corresponding to mineral formation conditions in the solar nebula.

Anders, E.↗