关键词: 东南极, 泛非期, 普里兹造山带, 格林维尔期, 雷纳造山带, 超大陆演化

Abstract:

Fourteen geological surveys in East Antarctica from 1998 to 2017 were organized by the Chinese National Antarctic Research Expedition. The semicircular survey region has a radius of about 400 km from the Chinese Zhongshan Station in the Larsemann Hills. Main bedrock exposures in this area include the Grove Mountains, eastern Amery Ice Shelf-southwestern Prydz Bay, northern Prince Charles Mountains, Mount Brown, Rauer Group, and Vestfold Hills. Based on large- and medium-scale geological mapping and comprehensive multidisciplinary studies, the following has been achieved. (1) The Grove Subglacial Highlands has proven to be metamorphic terrain that experienced only a single Pan-African (~570–500 Ma) tectonometamorphic cycle. High-pressure mafic and pelitic granulites have been discovered from glacial moraines, and the Pan-African orogenic process has been accurately depicted. New data suggest that the Prydz Belt is a collisional zone, supporting a tectonic model that the Gondwana supercontinent was assembled from several continental blocks during Pan-African times. (2) A long-lived Mesoproterozoic continental arc exceeding >2 000 km occurs between the Indian and East Antarctic cratons. Arc magmatism lasted from ~1 500 Ma to ~ 1 000 Ma. It is proposed that the tectonic evolution of the Rayner orogen may involve an arc-continent collision followed by continent-continent collision during the Grenvillian (~1 000– 900 Ma) time. (3) Early kyanite relics have been identified from ultrahigh-temperature metapelites in the Rauer Group, and a precise clockwise P-T path of the ultrahigh-temperature metamorphism has been deduced. (4) Grenvillian (~960–940 Ma) heterogeneous granulitization with P-T conditions of 820–870?C and 0.84–0.97 GPa has been recognized in mafic dyke swarms from the southwestern Vestfold Block, suggesting that this block may have involved the Rayner orogeny during collision between the Indian and East Antarctic cratons. (5) U-Pb zircon ages of ~3.5–3.3 Ga have been obtained from weakly metamorphosed glacial boulders and loose sands from moraines around the southeastern margin of Vestfold Hills, on which basis it has been inferred that a possible Paleoarchean continental block exists beneath the ice sheet to the southeast of Vestfold Hills. It is suggested that future geological field investigations in the Indian Ocean sector of Antarctica should extend to the southern Prince Charles Mountains, the Napier Complex, and the Denman Glacier. Research should focus on the response of the Antarctic continent to the assembly and breakup of supercontinents in the geological history of the Earth. It can be carried out in the following aspects: (1) recognition of the Archean continental nuclei and their global correlations, (2) record of the Grenvillian orogeny and assembly of the Rodinia supercontinent, (3) record of the Pan-African orogeny and assembly of the Gondwana Supercontinent, and (4) breakup and dispersion of the supercontinent during the Phanerozoic. Such research will advance China’s research on Antarctic geology to ap-propriate international standards.

Key words: East Antarctica, Pan-African, Prydz Belt, Grenvillian, Rayner orogen, supercontinent evolution