Oxygen Isotope Studies of Crustal Recycling at Convergent Margins

点击翻译按钮获取中文摘要

9805101StolperSubduction of oceanic crust is a major factor controlling arc magmatism, crustal growth and the recycling of volatiles and other elements into the mantle. Subducted components in the sub-arc mantle have principally been studied using variations in the abundance and isotopic composition of minor and trace elements that are highly concentrated into fluids and silicate melts. Oxygen isotope variations should provide complementary constraints due to the isotopic contrast between crustal and mantle oxygen and to the simple relationship between variations in oxygen isotope ratio and the relative abundances of crustal components in the sources of mantle derived lavas. Previous laser fluorination and ion microprobe oxygen isotope data suggest that mantle melting in subduction zone environments is a sensitive function of the abundance of a 'slab' derived hydrous fluid, providing an unusual and concrete link between geochemical tracers of subducted materials and the petrogenesis of arc-related lavas. Building on these results this study includes investigations of: [1] the oxygen isotope variability in arc-related lavas from highly depleted sources and from arcs with trace element evidence for a large 'slab melt' component, [2] the existence of highly depleted, high delta 18O mantle peridotites suggested to exist by our data for arc lavas, and [3] siliceous melts in mantle xenoliths from the Kamchatka arc and elsewhere. This research has the potential to yield significant new insights into the role of crustal recycling in the genesis of arc-related lavas.