Composition and structural control of crustal domains in the central Andes

Abstract

Present-day ratios of Pb isotopes (324 published samples, 435 new) and Nd-Sr isotopes (150 published, 180 new) on Proterozoic to Holocene igneous, metamorphic, and sedimentary rocks define (at high spatial resolution) distinct isotopic domains of the crust in the central Andes. These domains correlate with the internal compositional structure of the crust as revealed by a three-dimensional density model. Pb-Nd isotopic boundaries thus correspond to variations in crustal compositional structure and reflect Proterozoic mafic-dominated and Paleozoic felsic-dominated crustal lithologies. Age and composition (mafic versus felsic) of these domains have controlled the rheology of the Andean crust, have influenced crustal deformation patterns, and correlate with the central Andean plateau segmentation.