Upper Mesozoic tectonic evolution of the Meso-Tethys Ocean: Geochronological and geochemical constraints from central Tibetan Plateau ophiolites and magmatic arc rocks
Zhen Wang , Yuruo Shi , Michele Lustrino , Federico Rossetti , Mohsen Nasrabady , J.Lawford Anderson , Qiong Ci , Qing Qian , Nyima Taring
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引用次数: 0
Abstract
Ophiolites and magmatic arc rocks can provide key constraints on tectonic and geodynamic reconstructions of collisional zones, involving continental assembly and fragmentation through time. With the aim to better define the regional geodynamic evolution of central Tibetan Plateau, in this contribution we report new whole-rock chemical and zircon SHRIMP U-Pb age data from ophiolites and associated magmatic arc rocks of the Meso-Tethys oceanic realm. Lower Cretaceous oceanic crust is indicated by MORB-like pillow basalts (132.9 ± 1.4 Ma) from the Dongqiao ophiolite and sheeted dikes (116.8 ± 1.4 Ma) from the Yunzhug ophiolite. Their geochemical fingerprints are compatible with a DMM-like source, slightly modified by slab-derived metasomatic components, demonstrating a back-arc paleo-tectonic setting of formation. Magmatic arc rocks from the northern and central Lhasa sub-terranes and southern Qiangtang terrane include I-type granitoids from the Asa (155.5 ± 1.0 Ma), Jiarebu Tso (136.1 ± 1.3 Ma), and Dongqiao (107.5 ± 0.9 Ma) areas. These rocks are all compatible with an origin in subduction to post-collisional settings, involving both lower crustal and mantle-derived components. The adakite-like andesites of Wuru Tso (114.1 ± 1.2 Ma) and the andesites of Tangra Yumco (116.1 ± 1.4 Ma) both indicate derivation from subduction-related sources. Specifically, the Wuru Tso andesites originated from the partial melting of an oceanic slab contaminated by enriched mantle, without continental crust contribution, whereas the Tangra Yumco andesites were derived from a subduction-modified mantle source. When framed in the regional scenario, the new temporal and geochemical constraints presented in this study suggest a new Mesozoic geodynamic evolution for the Meso-Tethyan Ocean that includes: (a) co-existence of two retreating subduction systems with opposite polarities (northward and southward) at ∼ 155 Ma; (b) back-arc extension in the upper-plate domains during ∼ 136–132 Ma; (c) slab break-off at ∼ 117–114 Ma; and (d) collision and post-collisional tectonics in the Lhasa-Qiangtang starting at ∼ 107 Ma.
期刊介绍:
Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.