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Ghose, S.

Publications and source records attributed to Ghose, S..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Pyroxene-spinel intergrowths in lunar and terrestrial pyroxenes

The paper describes the oriented intergrowth of spinel and pyroxene in a pigeonite from Luna 20, an augite from Apollo 16 anorthosite 67075, and an orthopyroxene from a spinel lherzolite nodule from the San Quintin volcanic field, Mexico. Using Mo K alpha radiation, photographs were taken of small, hand-picked single-crystals. A mechanism of exsolution is suggested in which the oxygen framework remains intact and spinel nuclei are formed by the migration of cations from interstitial sites and tetrahedral sites in the original non-stoichiometric pyroxene.

Okamura, F. P.↗
NASA NTRS1974

Petrology and crystal chemistry of poikilitic anorthositic gabbro 77017

Aspects of mineralogy are considered, taking into account the occurrence and the characteristics of plagioclase, pyroxene, and olivine. Attention is also given to oxides, opaque minerals, and glass components. Questions regarding the temperature of formation and the origin of the considered lunar poikilitic rocks are discussed. It is pointed out that the presented hypothesis may not be applicable to other poikilitic lunar rocks.

Mccallum, I. S.↗
NASA NTRS1972

Mg/2+/-Fe/2+/ order-disorder in cummingtonite, /Mg, Fe/7Si8O22/OH/2 - A new geothermometer.

Determination of the temperature dependence of the Mg(2+)-Fe(2+) distribution between the M4 site and the M1, M2 and M3 sites in magnesium-rich cummingtonites by Fe-57 Mossbauer resonance spectroscopy. For the basic reversible ion-exchange reaction involved, the Gibbs free energy is estimated to be 3.6 to 4.1 kcal/mole, assuming an ideal solution model at each set of sites. The crystallization temperatures of two cummingtonite-bearing metamorphosed ultrabasic rocks are estimated to be 265 and 290 deg C. The Mossbauer resonance spectra are found to be an effective basis for detecting changes in site occupancies as a function of temperature.

Ghose, S.↗
NASA NTRS1972

Investigation of a possible solar-wind darkening of the lunar surface by photoelectron spectroscopy.

Detailed sequential study by photoelectron spectroscopy of the change in valence states of iron in Fe2O3, Fe3O4, FeO, and Fe foil samples, showing that chemical reduction does take place on the sample surface when argon ion bombardment occurs. These spectra give evidence that, after prolonged ion bombardment, the surface of all four samples consisted predominantly of iron in the metallic state. Argon ion sputtering of 15 silicate and oxide samples under similar experimental conditions produced surface darkening only in samples containing iron. Monitoring of the photoelectron peak of carbon during the experiment indicates that ion-bombardment darkening is not due to the buildup of hydrocarbon surface contaminants in the oil-free high-vacuum system used by the authors. On the basis of these studies, it is concluded that solar-wind bombardment should be included as one of the possible mechanisms for producing darkening of the lunar surface.

Yin, L. I.↗
NASA NTRS1972

Nuclear magnetic resonance of Al-27 in topaz, Al2SiO4/F, OH/2.

The Al-27 nuclear quadrupolar coupling constant and asymmetry parameter (eta) in topaz have been determined to be 1.67 (plus or minus 0.03) MHz and 0.38 plus or minus 0.05, respectively. These values and the orientations of the principal axes are consistent with the Fe(3+) paramagnetic resonance data and with the symmetry of the AlO4F2 octahedron.

Tsang, T.↗