Collaborative Research: Primitive Magmatism and Crustal Genesis in an Island Arc

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The main goals of this funded project are to test ideas about the origin of continental crust and the basic controls on the volcanic arc output of subduction zones. The western Aleutians contain high Mg# andesites that are very close in chemistry to the average continental crust. This award will support a field program of dredging in the Aleutian arc which is a good natural laboratory because it has never been rifted and shows a gradient of convergence angle from east to west, with strongly oblique convergence in the west. Further, there is a gradient in sediment "flux" along the arc, with the western Aleutians representing a global low-sediment content endmember. The program is aimed at obtaining more volcanic rock samples from the western Aleutian arc in five distinct dredge areas. A 30-35 day multibeam, single channel seismic and sampling cruise (35-40 dredges total) will be undertaken, with bathymetric and SCS surveys prior to sampling. The budget includes costs for a minimal port-cruise program of analyses and 40Ar/39Ar dating of igneous rocks.