1. Polarity and Timing of the Deformation Along the Jinsha Suture Zone (Yushu Area, Northeastern Tibet).
- Author
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Goussin, Fanny, Guillot, Stéphane, Ruffet, Gilles, Poujol, Marc, Oliot, Émilien, Replumaz, Anne, Cordier, Carole, Dupont‐Nivet, Guillaume, and Roperch, Pierrick
- Abstract
The Tibetan Plateau was formed by intense Cenozoic shortening (up to 1,100 km) of a composite "proto‐Tibet," itself the product of a long Paleozoic and Mesozoic history of accretion of Gondwana‐derived continental fragments and volcanic arcs against the Asian continental margin. The difficult access and the scarcity of outcrops have long limited the possibilities of studying these Mesozoic suture zones in the heart of the Plateau. In this work, we present new U‐Pb and 40Ar/39Ar ages from the highly deformed units of the Yushu mélange, along the Jinsha Suture in the northeastern Qiangtang terrane. Early Triassic (c. 253 Ma) to Middle Jurassic ages (c. 165 Ma) complement the existing data set and help to refine the chronology of the Paleo‐Tethyan oceanic subductions which have structured the northeastern part of the Qiangtang terrane. The Yushu mélange records at least three successive tectono‐magmatic events. The opening of a back‐arc basin during the northward Paleo‐Tethyan subduction along the Longmu Co‐Shuanghu Suture during Early to Middle Triassic; then its closure during the southward subduction of the Songpan‐Ganze Ocean along the Jinsha Suture in Late Triassic. Finally, a shortening phase related to the continental collision of the Songpan‐Ganze and Qiangtang blocks from Late Triassic to Early‐Middle Jurassic. No evidence for any high‐ or mid‐temperature Cenozoic reactivation of the Jinsha suture in our study area is recorded. Plain Language Summary: The north‐eastern part of the Tibetan Plateau, called the Qiangtang terrane, has a long‐lasting geological history: not only it records the collision of the Indian continent with Asia, but also a much older history: during Mesozoic times (∼250–165 Ma), this area was made of continental islands separated by oceanic realms called "Paleo‐Tethyan" basins. The oceans disappeared by subduction, and the continents were accreted together to form the southern Asian margin. This part of the geological history of the Tibetan Plateau is not so well‐known, because of the scarcity of outcrops. In this work, we date rock samples with two methods (using argon and uranium isotopes) which give complementary results and allow a greater degree of precision concerning the timing of the deformation of the rocks. Our results contribute to refine the chronology of the tectonic events which have structured the northeastern part of the Tibetan Plateau, long before the India‐Asia collision. Key Points: The Jinsha Suture in the Yushu area (NE Tibet) recorded three main tectono‐metamorphic eventsDeformed samples yield Early Triassic to Middle Jurassic ages, related to the closure of the Songpan‐Ganze basin of the Paleo‐TethysThe Jinsha suture was not reactivated at >200°C during Cenozoic post‐collisional regional shortening [ABSTRACT FROM AUTHOR]
- Published
- 2023
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