CONTINUATION OF THE MOZAMBIQUE BELT INTO EAST-ANTARCTICA - GRENVILLE-AGE METAMORPHISM AND POLYPHASE PAN-AFRICAN HIGH-GRADE EVENTS IN CENTRAL DRONNING MAUD LAND

The about 500 km long coastal stretch of central Dronning Maud Land (D ML), East Antarctica, is critical for understanding both Gondwana and Rodinia assembly. In common Gondwana reconstructions central DML lies at the potential southern extension of the Mozambique Belt. We report the first extensive geochronological study of magmatic and metamorphic rocks from the area. These new U-Pb SHRIMP zircon and Sm-Nd-data of r ocks sampled during the German international GeoMaud 1995/96 expeditio n indicate that the oldest rocks in central DML are Mesoproterozoic in age. The crystallization ages of metavolcanic rocks were determined a t c. 1130 Ma. Syn-tectonic granite sheets and plutons give ages of c. 1080 Ma, contemporaneous with metamorphic zircon growth at granulite f acies conditions. An anorthosite intrusion and a charnockite are dated at c. 600 Ma. Subsequent metamorphism is recorded for at least two di fferent episodes at c. 570-550 Ma and between 530 to 515 Ma. The latte r metamorphic event reached granulite facies and is associated with th e syn-tectonic intrusion of a granodiorite body at Conradgebirge. Init ial is an element of(Nd,t)-values of the U-Pb dated rocks with crystal lization ages around 1.1 Ga range from c. +7 to -4. These values sugge st that their magmatic precursors represent variable mixtures of a pri mitive mantle-derived and continental crust component generated within a mature island are. Initial Nd isotope data of Cambrian meta-igneous rocks are indistinguishable from the Grenville-age rocks, probably re presenting partial melts of the Grenville-age basement. The occurrence of Pan-African syn-tectonic granitoids is unique in DML. The structur e and shape of this body indicates that the main structural ENE-WSW tr end of the region is Pan-African in age and not older, as previously a ssumed. Some major late ductile sinistral shear zones occuring in the study area fit well in the overall sinistral transpressional setting o f the Mozambique Belt. Thus, central DML very probably represents the southern continuation of the Mozambique Belt into East Antarctica.