U-Th-Pb monazite and Sm-Nd dating of high-grade rocks from the Grove Mountains, East Antarctica: further evidence for a Pan-African-aged monometamorphic terrane

Abstract

The Grove Mountains, 400 km south of the Chinese Zhongshan Station, are an inland continuation of the Pan-African-aged (i.e., Late Neoproterozoic/Cambrian) Prydz Belt, East Antarctica. In this paper we carried out a combined U–Th–Pb monazite and Sm–Nd mineral–whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U–Th–Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523  4 Ma for the cores and 508  6 Ma for the rims. Sm–Nd mineral–whole-rock isotopic analyses yield isochron ages of 536  3 Ma for a coarse-grained felsic orthogneiss and 507  30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged (i.e., Late Mesoproterozoic/Early Neoproterozoic) metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt. Citation: Liu X C, Ling X X, Jahn B-M. U-Th-Pb monazite and Sm-Nd dating of high-grade rocks from the Grove Mountains, East Antarctica: further evidence for a Pan-African-aged monometamorphic terrane. Adv Polar Sci, 2018, 28 (2): 108-117, doi:10.13679/j.advps.2018.2.00108