Sulfur isotope and abundance systematics of angrite meteorites

Angrites are a small group of ancient igneous rocks (4.558 to 4.564 Ga) that have been used to provide critical data and information for understanding accretion, melting, and differentiation of the earliest evolved protoplanets. Sulfur isotopic compositions (δ³⁴S, Δ³³S and Δ³⁶S) and abundance data are presented for six angrite meteorites, including a fine grained quenched, (possibly volcanic) specimen (NWA 1296), a medium-grained hypabyssal specimen (SAH 99555), and coarse grained plutonic examples (Angra Dos Reis, NWA 4801, NWA 4590, and NWA 6705) to gain insights into magmatic processes on the angrite parent body (APB) and solar nebular chemistry prior to its formation.

The sub per-mil variation of δ³⁴S (-0.72‰ to 0.38‰) relative to Canyon Diablo Troilite (CDT), together with the highly variable abundance data (477 to 4105 ppm S), is interpreted to reflect variable redox state and sulfur partitioning among silicate melt, sulfide, and fluid phase within the APB. The clustered Δ³³S (with an average of 0.010 ± 0.003‰, 2 SE) and Δ³⁶S (with an average of -0.21 ± 0.19‰, 2 SE) values of this group of samples are interpreted to reflect degree of mixing and distribution pattern of processed sulfur (precursor materials of APB) in the protoplanetary disk.