| 青藏高原南部拉萨地体的变质作用与动力学 |
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| 关键词:Tibetan Plateau Lhasa terrane metamorphism orogeny plate convergence |
| 基金项目:国家自然科学基金项目(编号: 41230205; 40972055; 41202035);中国地质调查局工作项目(编号: 1212011121269);中国地质科学院地质研究所基本科研业务费项目(编号: J1203) |
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| Metamorphism and Dynamics of the Lhasa Terrane, South Tibet |
| The Lhasa terrane in southern Tibet has long been accepted as the last crustal block accreted with Eurasia prior to its collision with the northward drifting of Indian continent in the Cenozoic. Thus, the Lhasa terrane is the key to studying the origin and evolution of the Tibetan Plateau. The Lhasa terrane experienced multistage metamorphism, which included the Neoproterozoic and Late Paleozoic HP metamorphism in the oceanic subduction realm, the Early Paleozoic and Early Mesozoic MP metamorphism in the continent-continent collisional zone, the Late Cretaceous HT/MP metamorphism in the mid-oceanic ridge subduction zone, and two stages of Cenozoic MP metamorphism in the thickened crust above the continental subduction zone. These metamorphic events and the associated magmatism suggest that the Lhasa terrane experienced a complex tectonic evolution from the Neoproterozoic to Cenozoic. (1) The crystalline basement of the North Lhasa terrane includes Neoproterozoic oceanic crustal rocks, representing probably the remnants of the Mozambique Ocean derived from the break-up of the Rodinia supercontinent. (2) The oceanic crustal basement of North Lhasa witnessed a Late Cryogenian (~650 Ma) HP metamorphism and an Early Paleozoic (~485 Ma) MP metamorphism in the subduction realm associated with the closure of the Mozambique Ocean and the final amalgamation of eastern and western Gondwana, suggesting that the North Lhasa terrane might have been partly derived from the northern segment of the East African Orogen. (3) The Lhasa and Qiangtang terranes witnessed Middle Paleozoic (~360 Ma) magmatism, suggesting an Andean-type orogeny that was derived from the subduction of the Paleo-Tethys Ocean. (4) The closure of Paleo-Tethys Ocean between the North and South Lhasa terranes and subsequent terrane collision resulted in the formation of Late Permian (~260 Ma) HP metamorphic belt and Triassic (220 Ma) MP metamorphic belt. (5) The South Lhasa terrane experienced Late Cretaceous (~90 Ma) Andean-type orogeny, characterized by the regional HT/MP metamorphism and coeval intrusion of the voluminous Gangdise batholith during the northward subduction of the Neo-Tethyan Ocean. (6) During the Early Cenozoic (55~45 Ma), the continent-continent collisional orogeny resulted in the thickening of the crust of the South Lhasa terrane and the generation of MP amphibolite-facies metamorphism and syn-collisional magmatism. (7) Following the continuous continent convergence, the South Lhasa terrane also experienced MP metamorphism during Late Eocene (40~ 30 Ma). The tectonic imprints from the Lhasa terrane provide excellent examples for understanding geodynamics of metamorphic processes along convergent plate boundaries. |
| DONG Xin,ZHANG Ze-ming,XIANG Hua,HE Zhen-yu.2013.Metamorphism and Dynamics of the Lhasa Terrane, South Tibet[J].Acta Geoscientica Sinica,34(3):257-262. |
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