Rhenium enrichment in the northwest Pacific arc

Abstract

Rhenium (Re) is one of the least abundant elements in the silicate Earth. However, independent rhenium sulfide was reported in the Usu and Kudryavy volcanos, namely rheniite (ReS2, 74.5 wt% of Re). This raises questions about the sources of the Kurile–Kamchatka volcanic island arc magmas and geochemical cycling of Re. The oxidation-reduction cycle on the Earth’s surface is the major process that concentrates Re in reduced sediments. The northwest part of the Pacific plate mainly consists of Jurassic to Cretaceous oceanic crust, with abundant organic-rich sediments. During plate subduction, Re is remobilized early due to the devolatilization of organic-rich sediments and then the decomposition of sulfide (e.g., pyrite), and is subsequently added to the mantle wedge at shallow depths, which is usually not sampled by arc magmas unless there is a major change in the subduction regime. Ridge subduction in the northwest Pacific was initially characterized by low angle subduction. When slab rollback started, rhenium-enriched components were involved in arc magmas, and further concentrated in volcanic vents because of the volatility of Re, forming rheniite.