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Durham University

Department of Earth Sciences

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Publication details for Professor Yaoling Niu

Song, S.G., Niu, Yaoling, Wei, C.J., Ji, J.Q. & Su, L. (2010). Metamorphism, anatexis, zircon ages and tectonic evolution of the Gongshan block in the northern Indochina continent – An eastern extension of the Lhasa Block. Lithos 120(3-4): 327-346.

Author(s) from Durham

Abstract

The Gongshan block near the Eastern Himalayan Syntaxis is a fault-bounded block at the northern tip of the
triangle-shaped Indochina continent (NIC). Exposed in this block are late Paleozoic (Carboniferous to
Permian) strata and a north–south belt of intermediate to felsic batholiths (i.e., Gaoligongshan magmatic
belt). The contact between the Gaoligongshan batholiths and Carboniferous/Permian strata is characterized
by a series of high-grade metamorphic gneisses with leucosome granite veins (i.e., the so-called “Gaoligong
Group”). U-Pb SHRIMP and LA-ICP-MS dating of zircons indicate that these gneisses are actually
metamorphosed Paleogene sediments containing inherited Archean to Cretaceous detrital zircons (from
2690 to 64 Ma) and have undergone medium- to high-pressure granulite-facies metamorphism at ~22 Ma.
Leucosome and S-type granite of 22–53 Ma by anatexis are ubiquitous within high-grade metamorphic rocks
in the southern part of the Gongshan block. An Early Paleozoic gneissic granite and granitoid intrusions of
Jurassic, Cretaceous and Oligocene-Miocene ages are also recognized in NIC blocks. These ages suggest that
the NIC differs distinctly from the Indian continent, the Greater and Lesser Himalaya zones, and the Yangtze
Craton, but resembles the Lhasa Block in terms of Paleozoic to Mesozoic magmatism and detrital zircon ages.
This offers an entirely new perspective on the tectonic evolution of the Gongshan block in particular and of
the history of the Lhasa Block in the context of the India-Asia continental collision in general. Furthermore,
the high-grade metamorphism in the NIC indicates a strong crustal thickening (vs. strike-slip shearing) event
during much of the Eocene to the Oligocene (~53–22 Ma) that has brought the Paleogene sediments to
depths of greater than 25 km. Continuous northward convergence/compression of the Indian Plate at the
Eastern Himalayan Syntaxis may have led to the clockwise rotation, southeastward extrusion and extension
of the southeastern part of the Indochina continent.