Abstract:

Mafic granulites and amphibolites that underwent granulite facies metamorphism are outcropping in the Grove Mountains (GMs), East Antarctica. The mafic granulites underwent a near isothermal decompression (ITD) P T history from 0.93GPa and 800℃ (M1) to 0.64GPa and 805℃ (M2). This clockwise P T path can be explained in a model involving extensional collapse and exhumation of thickened crust, which was common with that of Larsemann Hill, East Antarctica. The compositions of major elements from the rocks are consistent with those of basalt and have evolutional current of tholeiite. Based on more geochemical signatures, two types of basalt are recognized, namely, ocean island basalt (OIB) and mid ocean ridge basalt (MORB). Type 1 rocks have similar geochemical characteristics, with high in Ti (TiO 2 =2.68%), REE (=202μg/g), LREE \[(La/Yb) N =4.8\], Ti/Y (=343) and Zr/Ti (=3.1), which are similar to those of OIB, and are considerable to be products of magma from enriched mantle sources (EM). Type 2 rocks are characterized by low Ti (TiO 2 = 1.1-1.31% ), REE (47-93μg/g), LREE/HREE (2.27-2.54), (La/Yb) N (=1.30-1.62) and lower P (P 2 O 5 =0.1-0.2%) than those of OIB, which are similar to those of MORB. The presence of such rock assemblages suggests the existence of an ocean basin in this region during Pan Africa ages.