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Chemical 3D-imaging of glass inclusions from allende (CV3) olivine via SIMS : A new insight on chondrule formation conditions

Florentin, L. ; Deloule, E. ; Faure, F. ; Mangin, D., GCA

Chemical 3D-imaging of glass inclusions from allende (CV3) olivine via SIMS : A new insight on chondrule formation conditions

Florentin, L. ; Deloule, E. ; Faure, F. ; Mangin, D.

Geochimica et Cosmochimica Acta, 2018, 230, 83-93

Abstract :

Natural glass inclusions - hosted in Mg-rich olivines from Allende (CV3) type I chondrules - and synthetic melt inclusions - trapped in forsterite crystallized from CMAS (CaO-MgO-Al2O3-SiO2) melts - were mapped by Secondary Ion Mass Spectrometry (SIMS) for CMAS major oxides. The first ever 3D chemical images of extra-terrestrial glass inclusions were obtained, along with chemical depth profiles for each oxide. Results show similar patterns for both synthetic glass inclusions (trapped in olivine formed by slow crystallization in a magmatic liquid) and natural inclusions from Allende’s olivines. No incompatible-rich boundary layer or diffusion pattern was observed in either case. The absence of an incompatible-rich boundary layer suggests that the olivine overgrowth surrounding glass inclusions in Allende’s olivines was formed during slow cooling of the host olivine and likely the surrounding chondrule. This provides new constraints on the cooling rates of type I chondrules.

Voir en ligne : https://doi.org/10.1016/j.gca.2018....




publié mercredi 2 mai 2018