The Multiple Sulfur Isotopic Composition of Iron Meteorites: Implications for Nebular Evolution

Abstract

Multiple sulfur isotopic measurements of troilite from 61 different iron meteorites were undertaken in order to test for sulfur isotopic homogeneity within (and between) 8 different iron meteorite groups. It was found that different members within a given group of iron meteorites have homogeneous &#916;<super>33</super>S compositions, but that these &#916;<super>33</super>S compositions differ between groups. This thesis shows that iron meteorites from the groups IC, IIAB, IIIAB, IIIF, and IVA have small yet resolvable enrichments or depletions in &#916;<super>33</super>S relative to Canyon Diablo Troilite (CDT) and troilite from other non-magmatic (IAB and IIE) iron meteorites. The observed anomalous sulfur isotopic compositions in magmatic iron meteorites are most consistent with Lyman-&#945; photolysis of H₂S, pointing towards inheritance of an unexpected photolytically-derived sulfur component in magmatic iron meteorite groups which is absent in non-magmatic iron meteorites, chondrites, and the Earth-Moon System.