Introduction: Triple oxygen isotope analyses have great significance in understanding meteorite c... more Introduction: Triple oxygen isotope analyses have great significance in understanding meteorite classification, constrain-ing primary and secondary processes on parent bodies and finding genetic relationships among meteorites. We have recently refined protocols for high precision and high accuracy analyses of triple oxygen isotopes using CO 2 laser-assisted fluorination extraction mass spectrometry [1]. We have also set up a CO 2 clumped isotopologue system to study carbonates in meteorites. Triple Oxygen Isotope System: Our laser-assisted fluorination line is equipped with a 20W CO 2 laser system and computerized beam intensity controller device. The extracted oxygen, after lasing the sample under BrF 5 atmosphere, is purified with cryogenic traps and finally adsorbed on a 5Å molecular sieve. A Delta V plus IRMS is used to analyse triple oxygen isotope compositions. This high precision and high accuracy laser-assisted fluorination system provides several enhancements over tradition...
–We report precise triple oxygen isotope data of bulk materials and separated fractions of severa... more –We report precise triple oxygen isotope data of bulk materials and separated fractions of several Shergotty–Nakhla–Chassigny (SNC) meteorites using enhanced laser-assisted fluorination technique. This study shows that SNCs have remarkably identical D 17 O and a narrow range in d 18 O values suggesting that these meteorites have assimilated negligibly small surface materials (<5%), which is undetectable in the oxygen isotope compositions reported here. Also, fractionation factors in coexisting silicate mineral pairs (px-ol and mask-ol) further demonstrate isotopic equilibrium at magmatic temperatures. We present a mass-dependent fractionation line for bulk materials with a slope of 0.526 AE 0.016 (1SE) comparable to the slope obtained in an earlier study (0.526 AE 0.013; Franchi et al. 1999). We also present a new Martian fractionation line for SNCs constructed from separated fractions (i.e., pyroxene, olivine, and maskelynite) with a slope of 0.532 AE 0.009 (1SE). The identical fractionation lines run above and parallel to our terrestrial fractionation line with D 17 O = 0.318 AE 0.016& (SD) for bulk materials and 0.316 AE 0.009& (SD) for separated fractions. The conformity in slopes and D 17 O between bulk materials and separated fractions confirm oxygen isotope homogeneity in the Martian mantle though recent studies suggest that the Martian lithosphere may potentially have multiple oxygen isotope reservoirs.
Introduction: Triple oxygen isotope analyses have great significance in understanding meteorite c... more Introduction: Triple oxygen isotope analyses have great significance in understanding meteorite classification, constrain-ing primary and secondary processes on parent bodies and finding genetic relationships among meteorites. We have recently refined protocols for high precision and high accuracy analyses of triple oxygen isotopes using CO 2 laser-assisted fluorination extraction mass spectrometry [1]. We have also set up a CO 2 clumped isotopologue system to study carbonates in meteorites. Triple Oxygen Isotope System: Our laser-assisted fluorination line is equipped with a 20W CO 2 laser system and computerized beam intensity controller device. The extracted oxygen, after lasing the sample under BrF 5 atmosphere, is purified with cryogenic traps and finally adsorbed on a 5Å molecular sieve. A Delta V plus IRMS is used to analyse triple oxygen isotope compositions. This high precision and high accuracy laser-assisted fluorination system provides several enhancements over tradition...
–We report precise triple oxygen isotope data of bulk materials and separated fractions of severa... more –We report precise triple oxygen isotope data of bulk materials and separated fractions of several Shergotty–Nakhla–Chassigny (SNC) meteorites using enhanced laser-assisted fluorination technique. This study shows that SNCs have remarkably identical D 17 O and a narrow range in d 18 O values suggesting that these meteorites have assimilated negligibly small surface materials (<5%), which is undetectable in the oxygen isotope compositions reported here. Also, fractionation factors in coexisting silicate mineral pairs (px-ol and mask-ol) further demonstrate isotopic equilibrium at magmatic temperatures. We present a mass-dependent fractionation line for bulk materials with a slope of 0.526 AE 0.016 (1SE) comparable to the slope obtained in an earlier study (0.526 AE 0.013; Franchi et al. 1999). We also present a new Martian fractionation line for SNCs constructed from separated fractions (i.e., pyroxene, olivine, and maskelynite) with a slope of 0.532 AE 0.009 (1SE). The identical fractionation lines run above and parallel to our terrestrial fractionation line with D 17 O = 0.318 AE 0.016& (SD) for bulk materials and 0.316 AE 0.009& (SD) for separated fractions. The conformity in slopes and D 17 O between bulk materials and separated fractions confirm oxygen isotope homogeneity in the Martian mantle though recent studies suggest that the Martian lithosphere may potentially have multiple oxygen isotope reservoirs.
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Papers by Arshad Ali