The Deep Sulfur Cycle in Subduction Zones and Arc Magmas

William Marsh Rice University, Houston TX

Investigators

Abstract

Sulfur is a ubiquitous element on Earth. Because it exhibits a wide range of valence states, sulfur can behave as an electron acceptor or donor and thus is a potent driver of redox reactions, dictating the mobility of metals and serving as an energy source for life. Understanding sulfur geochemistry in the deep Earth is thus critical to understanding the origin of ore deposits, the evolution of oxygen in the atmosphere and marine environment, the pathways of biogeochemical processes, and climate change. As a small step towards better understanding the deep sulfur cycle, these researchers will characterize the sulfur content and isotopic composition of a volcanic arc, from the mantle through the crust. How sulfur cycles between the endogenic (crust, mantle, and core) and exogenic (ocean, atmosphere, and biosphere) Earth systems is of particular interest regarding the role of sulfur in various redox-driven processes on Earth. The locus of sulfur flux between these Earth systems occurs in volcanic arcs, where mantle melting in the subduction wedge induces shallow melting and ultimate storage or eruption of magma within or through the crust. The goal of this project is three-fold: 1) quantify how much sulfur and what type (sulfate vs. sulfide) is transported via the slab to depths of magma generation in subduction zones, 2) construct the ?stratigraphy? of sulfur from the mantle through the crust in volcanic arcs, and 3) define the average sulfur concentration of juvenile and mature continental crust. From this information the sulfur content and isotopic architecture of an arc from the mantle through the crust can be constructed, with implications for sulfur cycling between the endogenic and exogenic Earth systems.