|
|||||
|
|
Oxygen isotopic constraints on the origin of magnesian chondrules and on the gaseous reservoirs in the early Solar System |
|
| Authors: | Marc Chaussidon Guy Libourel Alexander N Krot |
| Institution: | a CRPG-CNRS, BP 20, 54501, Vandoeuvre-lès-Nancy Cedex, France b Ecole Nationale Supérieure de Géologie, INPL, Rue du Doyen Marcel Roubault, BP 40, 54501 Vandoeuvre-lès-Nancy, France c Hawai′i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai′i at Manoa, Honolulu, HI 96822, USA |
| Abstract: | We report in situ ion microprobe analyses of the oxygen isotopic composition of the major silicate phases (olivine, low-Ca pyroxene, silica, and mesostasis) of 37 magnesian porphyritic (type I) chondrules from CV (Vigarano USNM 477-2, Vigarano UH5, Mokoia, and Efremovka) and CR (EET 92042, EET 92147, EET 87770, El Djouf 001, MAC 87320, and GRA 95229) carbonaceous chondrites. In spite of significant variations of the modal proportions of major mineral phases in CR and CV chondrules, the same isotopic characteristics are observed: (i) olivines are isotopically homogeneous at the ‰ level within a chondrule although they may vary significantly from one chondrule to another, (ii) low-Ca pyroxenes are also isotopically homogeneous but systematically 16O-depleted relative to olivines of the same chondrule, and (iii) all chondrule minerals analyzed show 16O-enrichments relative to the terrestrial mass fractionation line, enrichments that decrease from olivine (±spinel) to low-Ca pyroxene and to silica and mesostasis. The observation that, in most of the type I chondrules studied, the coexisting olivine and pyroxene crystals and glassy mesostasis have different oxygen isotopic compositions implies that the olivine and pyroxene grains are not co-magmatic and that the glassy mesostasis is not the parent liquid of the olivine. The δ18O and δ17O values of pyroxene and olivine appear to be strongly correlated for all the studied CR and CV chondrules according to: |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ | |