Tectonic division of the Southwestern terrane at the western Sør Rondane Mountains, Dronning Maud Land, East Antarctica, from a viewpoint of zircon U-Pb ages

Abstract

The Sør Rondane Mountains (SRM) in East Antarctica, lie within the late Neoproterozoic-early Paleozoic collision zone between East and West Gondwana. Many studies have been carried out in the eastern SRM, whereas fundamental questions on the western SRM remain unanswered, for example, tectonic division and detailed metamorphic age. This paper describes zircon U-Pb ages from gneisses in the western SRM, and the tectonic division of this area is discussed.

The rocks of the study area are divided into units 1 to 3 based on their lithology and structural position. Units 1 and 2, which are divided by the Kanino-tume shear zone (KSZ), are mainly composed of greenschist/amphibolite-facies gneisses and amphibolite/granulite-facies gneisses, respectively. Unit 3 is mostly occupied by the Proterozoic GTTG. It is, in this study, revealed that the metamorphic ages of units 1 and 2 are, respectively, ∼ 600-550 and ∼ 670-600 Ma. The distribution of the KSZ has been inferred by mapping, but the present results on the distribution of metamorphic ages confirm this. The KSZ of the low-angle shear zone may be a critical tectonic boundary dividing the two gneiss units of ∼ 600-550 and ∼ 670-600 Ma within the East African-Antarctic orogen.