The Significance of Slope 1 Variation in Early Solar System Solids

Greenwood, R C ; Franchi, I A ; Alexander, C M O'D ; Zolensky, M E ; Buchanan, P C

关键词: SLOPES;    CARBONACEOUS CHONDRITES;    ALLENDE METEORITE;    OXYGEN ISOTOPES;    SOLAR SYSTEM EVOLUTION;    COSMOCHEMISTRY;    METEORITIC COMPOSITION;    SECONDARY ION MASS SPECTROMETRY;   

RP-ID  :  JSC-E-DAA-TN56757

学科分类：天体物理学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

As originally demonstrated by Clayton and co-workers, primitive meteorites and their components commonly display mass-independent oxygen isotopic variation. As a tool to understand this behaviour, a number of reference lines have been defined, with slopes of approximately 1. The Carbonaceous Chondrite Anhydrous Mineral (CCAM) line, derived predominantly from analyses of components in the Allende (CV3) meteorite, is the most widely used reference and has a slope of 0.94 plus or minus 0.01 (2 sigma). However, the fundamental significance of the CCAM line has been questioned. Based on the results of a UV laser ablation study of an Allende CAI (calcium-aluminum–rich inclusion), it was suggested that a line of exactly slope 1 (Y&R line - Young and Russell line) was of more fundamental significance. SIMS (Secondary Ion Mass Spectrometry) analysis of chondrules from primitive CRs and related chondrites define a third, distinct slope 1 line, known as the Primitive Chondrule Minerals (PCM) line. Here we discuss the results of bulk oxygen isotope analysis of CO, CV and CR chondrites and various separated components, with the aim of better understanding the origin of slope 1 behaviour in early Solar System materials.