EVOLUTION OF GONDWANA - THE ANTARCTIC PERSPECTIVE WITH SHRIMP GEOCHRONOLOGY

点击翻译按钮获取中文摘要

The Dronning Maud Land, which is the Indian sector of the East Antarctica is referred as the southern extension of the Pan-African Mozambique mobile belt, and is one of the best fields to elucidate the evolution of the Gondwana continental crust. The aim of this study is to reconstruct the tectonic model of the Gondwana using the meamorphic P-T paths combined with precise age data by SHRIMP. The major results are:1) The Napier Complex consists of crustal fragments formed during 3.8-2.6 Ga, and the last orogeny was terminated in 2.52-2.46 Ga with the ultra-high temperature metamorphism.2) Re-examination of the metamorphic and protolith ages of the Lutzow Holm Complex elucidated that the pre-Gondwana history is totally different from those in the Sor Rondane Mountans. Moreover, in the Sor Rondane Mts., two stages of the Pan-African events are recognized. These facts give the constraints far the tectonic history of the Gondwana3) In the central Droning Maud Land, it is suggested that the inland mountain area and the Schirmacher Hill belong different tectonic units by comparison of modes of metamorphism, plutorism and preliminary SHRIMP ages.4) The SHRIMP age dating for the late Grenvillian A-type granite bodies sporadically occurring in the Natal Belt of South Africa revealed the time-space transition of the igneous activity.5) Studies on the continental crust of many areas from the world were performed as collaboration work using SHRIMP It Itsaq Complex in SW Greenland, the Harris Complex in NW Scotland, western Himalaya, the Kontum massif in Vietnam and Hidaka Belt and Kofu basin in Japan.6) As a part of the study of the development and maintenance of the SHRIMP II at the National Institute of Polar Research, standardization of the U-Pb and Mn-Cr methods, and measurement of REE were performed. In addition zircon standard samples from Duluth Complex was prepared. New zircon standards were evaluated with the conventional U-Pb-Th isotope measurement.