VARIATIONS IN LIGHT LITHOPHILE ELEMENTS (Li, B, Be) AND LITHIUM ISOTOPES IN MARTIAN PYROXENES AND OLIVINES: ROLES OF DEGASSING AND DIFFUSION

Introduction: The zoning patterns of light lithophile elements (LLEs: Li, Be, B) in pyroxenes of some Martian meteorites have been used to suggest that the parent basalts were water-saturated, which exsolved and lost an aqueous phase through degassing and eruption, causing depletion in LLEs in the pyroxene rims [1]. In contrast, other investigators have suggested a diffusion controlled fractionation in Li isotopes and LLE distribution pattern in Martian minerals [e.g., 2]. Therefore, the main aims of our project were to determine the LLEs and Li isotopic composition in pyroxenes and olivines from newly discovered Martian meteorites and then model and assess the roles of various processes involved in Martian magmatic history. Samples: We selected two Martian meteorites (LAR 06319 and MIL 03346) for our initial ionmicroprobe investigations. LAR 06319 is a phenocrystrich basalt belonging to the olivine-phyric shergottite group of Martian meteorites [3]. Olivine is the main phenocryst phase followed by low-Ca pyroxene (Fig. 1). The groundmass is feldspathic in composition and occurs as diaplectic glass (a result of impact which