Sulfur isotope ratios of Leg 126 igneous rocks

Abstract

Sulfur isotope ratios have been determined in 19 selected igneous rocks from Leg 126. The overall variation in sulfur isotope composition of the rocks is caused by varying degrees of seawater alteration. Most of the samples are altered by seawater and only five of them are considered to have maintained their magmatic sulfur isotope composition. These samples are all from the backarc sites and have δ34S values varying from +0.2‰ to +1.6‰, of which the high δ34S values suggest that the earliest magmas in the rift are more arc-like in their sulfur isotope composition than the later magmas. The δ34S values from the forearc sites are similar to or heavier than the sulfur isotope composition of the present arc. -Author