Isotopic and Trace Element Studies of the Lithospheric Mantle, Petrogenetic Processes and Magma Transport, & the Early Stages of Continental Crust Formation

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This a proposal to continue and expad our isotopic and trace element studies of a variety of mantle and mantle-derived rocks as tracers of the composition and evolution of the lithosphere and upper mantle, and of petrogenetic processes such as melting and magma transport. Our work is centered around isotopic studies of Sr, Nd and Pb on the one hand and U, Th series isotopes on the other, and the associated trace element concentrations which are measured in concert with the isotope ratio determinations. In addition, we discuss plans to add a number of important large ionic radius and high field strength elements to our capabilities using ICP-MS. Our investigations are varied and have both regional and more uniersal goals. In the most general sense, the work proposed is inteded to further our knowledge of the composition and evolution of the lithosphere anduppermost mantle in both continental and oceanic settings, and to help nderstand factors such as the timing of magma transport and the mechanisms of chemical fractionation during magmagenesis. Using isotopes as tracers we will also attempt to follow the earliest stages of continental crust formation in an accreting island arc terrane. Specific material we will investigate in pursuit of these goals incluse lavas from the Sylhet and Deccan Traps of India; mantle xenoliths from alkali basalts in Incia, China, Western North America and oceanic islands in the South Pacifice; a sequence of plutonic rocks from Luzon in the Philippines; island arc lavas from the Aleutians, ridge basalts from the Pacific and the Mariana Trough back arc basin.