Al-mg Dating of Ca-al-rich Inclusions in Acfer 094 Chondrite
نویسنده
چکیده
Introduction: Acfer 094 is one of the most primitive chondrites, which appears to have escaped thermal metamorphism above 300°C [1] and can potentially provide important clues to primary, undisturbed by parent body processes, abundances of short-lived ra-dionuclides in its components. Krot et al. [2] have recently described mineralogy and petrography of the Al-rich chondrules and refractory inclusions in Acfer 094. Here we report Al-Mg systematics of Ca-Al-rich inclusions (CAIs) in Acfer 094 determined by secondary ion mass spectrometry. Experimental: 14 CAIs in two polished sections of Acfer 094 were investigated, including 1 corundum-rich, 7 grossite-rich, 3 melilite-rich, 3 anorthite-rich [one of them is an amoeboid olivine aggregate (AOA)]. An O-primary beam ~10 µm in diameter was used for sputtering. In some spots repeated measurements were made. Also, if Mg-rich and Al-poor minerals were present in the CAIs studied, their Mg isotopic compositions were measured to determine the y-intercept on the isochron diagram. Secondary ions of
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