Collaborative Research: An Investigation into Relative Noble Gas Fractionation during Mantle Melting: Constraints fom the Southeast Indian Ridge

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Award is for measuring He, Ne, and Ar noble gases and CO2 content on step-crushed basaltic quench glasses from the Southeast Indian Ridge (SEIR) to examine how noble gases fractionate in the mantle, knowledge essential to understanding mantle melt extraction and volatile transport. This work will also examine heterogeneity in mantle 40 Ar/36Ar, possibly arising from subduction of atmospheric Ar, and will also investigate the so-called He-paradox, wherey melt samples whose parental material originated from deep within the earth (characterized by high 3 He/4He and associated with mantle plumes) have low He aundances, as well as the He flux seemingly having little to do with heat flux from the mantle (as represented by magma production). Samples from the Southeast Indian Ridge have been chosen for the study as they show smooth variation in composition away from the Amsterdamm-St. Paul mantle plume that coincides with changes in ridge axial depth. These samples therefore represent a unique sample set to examine the influence on sub-oceanic mantle noble gas systematics by a deep mantle plume acting on the mantle processes underneath a spreading ridge.