Trace element and isotopic characteristics of eclogites and other xenoliths derived from the lower continental crust of southeastern Australia and southwestern Colorado Plateau, USA

Abstract

Studies of ecologite and other high-pressure assemblage xenoliths which form a large component of the lowermost crust of terrains such as southeastern Australia have shown that a considerable variety of trace element and isotopic characteristics are present. The anticipated positive Eu anomalies complementary to the persistent negative anomalies typical of the upper crust are generally absent. Overall rare earth element (REE) abundance patterns vary from strongly light REE-depleted to enriched relative to the heavy REE. 87Sr/86Sr and 143Nd/144Nd data for these xenoliths are also heterogeneous and defy selection of representative isotopic ratios for the lower crust in the absence of knowledge of the volumetric significance of individual samples. Thermobarometric calculations assuming equilibrium give temperatures in the range 575-1065 C and pressures of about 10-16kbar. from Authors Show more