Mg Stable Isotopic characteristics of the SW Japan Arc and Rear Arc volcanics

Abstract

Subducted sediment derived components alter the chemical composition of the mantle and can influence magmatism in overlaying volcanoes. Stable Mg isotopic analysis is a newly developed tool which is frequently used to detect the type and chemical characteristics of the subducted sediments. Mg isotopes fractionate during silicate weathering and carbonate precipitation and marine carbonate sediments show some of the lowest Mg isotopic ratios on Earth. Although Mg isotopic analysis of Cenozoic volcanic rocks from northeast China have indicated involvement of carbonate sediments in the mantle below East Asia, no such data is available for the volcanoes in Japan showing similar chemical signatures. In this work we attempt to decipher the Mg isotopic signatures from the mantle below the southwest Japan arc.