Platinum Group Element Geochemistry of High-MgO Lavas

Florida State University, Tallahassee FL

Investigators

Abstract

To better understand the mantle geochemistry of the platinum group elements (PGEs), and the information returned by 186,187Os isotopic studies, we propose to determine the PGE abundances of a global suite of high-MgO lavas of Archean to Phanerozoic age, including komatiites and picrites. The results reported from our lab are based on a precise isotope dilution ICP-MS technique which has been successfully applied for the determination of PGEs in such rocks. We also propose to analyze separated mineral phases and extract, by physical and/or chemical techniques, the carrier phase(s) of the PGEs from these rocks. Proposed localities include high-MgO lavas from the following: Kamennoozero, Vetreny, Onega and Lapland (Baltic Shield); Belingwe (S. Africa); Emeishan (China); Song Da (NW Vietnam); Gorgona (Caribbean); and Iceland. All samples are available in collections held by us or will be generously provided by collaborators from other geochemical studies, particularly previous Os isotopic studies. Our intellectual goals for the proposed study are 1) to establish the rules of PGE behaviour during the high degrees of partial melting, and subsequent fractional crystallization, experienced by komatiites and picrites; 2) to obtain mantle source PGE compositions with which to test the hypotheses of crustal recycling and core-mantle interaction, and to establish, where possible, the mechanism of core-mantle interaction. The proposal supports the salaries of a graduate student and a research scientist, and the research forms the basis of a PhD thesis for the graduate student.