Spinels in D'Orbginy angrite

HWANG S.L.; CHU, H-T; VARELA, M.E; BRANDSTAETTER F,; IIZUKA Y.; SHEN P; YUI T.F.

Houston

Conferencia; Lunar and Planetary Science Conference; 2017

One of the uncommon features inD?Orbigny, in addition to the olivinites and the Mgrich olivine megacrysts, is the presence of large (~ 300-400 µm) spinel crystals [e.g., 1, 2, 3], similar to thatdescribed in Asuka 881371 [4]. The lack of equilibrium between spinel and a melt with the chemical composition of D?Orbigny, in addition to its texture indicating that spinels reacts-out in early stages of crystallization, led several authors [e.g., 1] to consider thisphase as xenocrystic.Here, we report detailed studies (EMPA, SEM, TEMand energy-dispersive X-ray (EDX)) on the differentspinel types hosted by olivinites as well as by olivine,anorthite and augite in the groundmass of the angriteD?Orbigny. The results suggest that the compositionaltrend: Cr-Spinel-Al-Spinel-Hercynite drawn by thedifferent types of spinels, may be the consequence oftwo physicochemical processes.