Late Paleozoic intrusive rocks from the southeastern Lhasa terrane, Tibetan Plateau, and their Late Mesozoic metamorphism and tectonic implications

• Published in: Lithos Vol. 198-199; pp. 249 - 262
• Main Authors: Dong, Xin, Zhang, Zeming, Liu, Feng, He, Zhenyu, Lin, Yanhao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2014
• Subjects: Late Mesozoic; Late Paleozoic; Lhasa terrane; Magmatism and metamorphism; Orogeny; China, People's Rep., Xizang, Tibetan Plateau; China, People's Rep., Xizang; Magmatism and metamorphism; Lhasa terrane; Late Paleozoic; Orogeny; Late Mesozoic
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2014.04.001

The Lhasa terrane in southern Tibet experienced Late Paleozoic and Mesozoic–Cenozoic composite orogenesis. This work reports a study on the petrology, geochemistry, zircon U–Pb chronology and Hf isotopes of Late Paleozoic and Late Mesozoic intrusive rocks from the southeastern Lhasa terrane. The Late Paleozoic intrusive rocks crystallized in the Late Devonian–Early Carboniferous of 371 to 355Ma, representing a bimodal igneous association formed in the back-arc extensional setting. The mafic end-member originated from the enriched mantle and experienced contamination of crustal materials, characterized by a slight enrichment of LREE, positive anomalies of U, K and Pb and negative anomalies of Th, Nb, Ta and Ti. The felsic end-member was derived from the partial melting of the ancient continental crust, characterized by metaluminous, positive anomalies of Th, Zr and Hf, negative anomalies of Ba, Sr, Nb, Ta and Ti and negative εHf(t) values of zircon with TDM2 ages from 1.90 to 1.40Ga. The Late Cretaceous (ca. 107Ma) mafic intrusions, along with the Late Paleozoic intrusive rocks, underwent nearly syn-intrusion amphibolite-facies metamorphism under P–T conditions of 0.56 to 0.69GPa and 692 to 735°C during the Andean-type orogeny correlated with the subduction of the Neo-Tethyan oceanic slab beneath the Lhasa terrane. This study provides a new insight into the pre-Cenozoic tectonic evolution of the Lhasa terrane. •Late Paleozoic intrusions in the southern Lhasa subterrane formed at 371 to 355Ma.•Late Paleozoic intrusions represent a bimodal igneous association on back-arc setting.•Mafic and felsic end-members are derived from different parental magmas.•The meta-magmatic rocks underwent amphibolite-facies metamorphism at 105 to 102Ma.•Magmatic accretion caused the MP metamorphism during the subduction of Neo-Tethyan.