Paleoproterozoic tectonic evolution of the Trans-North China Orogen: toward a comprehensive model.Report as inadecuate




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* Corresponding author 1 LCE - Laboratoire Chrono-environnement 2 ISTO - Institut des Sciences de la Terre d-Orléans 3 State Key Laboratory of Lithospheric Evolution 4 Géosciences Montpellier

Abstract : In this contribution we present a reconstruction of the overall lithotectonic architecture, from inner zones to external ones, of the Paleoproterozoic Trans North China Orogen, within the North China Craton. Moreover, forward thermobarometrical modeling on a kyanite-bearing gneiss yields a reliable prograde P-T-t-D path. In addition, 40Ar-39Ar dating on rocks from distinct litho-tectonic units helps us to distinguish several tectono-metamorphic events during the orogenic development. Considering these results, we propose a geodynamic model involving three cratonic blocks, namely the Western, Fuping and Eastern Blocks, separated by two oceans, the Lüliang and Taihang Oceans. The opening of oceanic basins occurred around 2.2-2.3 Ga. After the westward subductions of oceanic lithosphere, the Trans-North-China Orogen was built up through a polyphase tectonic evolution within the period 1900-1800 Ma. The first event D1 corresponded to the emplacement of lower and upper nappes herein called the Orthogneiss-and-Volcanites Unit OVU and the Low-Grade-and-Mafic Unit LGMU, respectively. The syn-metamorphic D1 deformation 1880 ± 10 Ma is characterized by a NW-SE stretching and mineral lineation with a top-to-the SE sense of shear. During ongoing compression of the thickening orogenic crust, a second deformation event D2 1850 ± 10 Ma was responsible for 1 syn-anatectic lateral flow and exhumation of the orogenic root and 2 folding of the middle and upper parts of the orogenic wedge that consequently acquired a fan-type geometry. The late D3 1830 ± 10 Ma and D4 1810 ± 10 Ma events are related to late-orogenic normal and strike-slip shearing, respectively. In our present state of knowledge, the Paleoproterozoic Trans-North China Orogen might be regarded as the assemblage of two continent-continent collisional belts, both of which are characterized by nappe stacking accommodated by top-to-the E-SE ductile shearing. Continental subduction, crustal thickening, partial melting of overthickened crust, exhumation of HP rocks and deposition of syn-orogenic detrital basins are typical features of modern collisional-type orogens.

Keywords : Trans-North China Orogen Paleoproterozoic Collision Pseudosection 40Ar-39Ar dating North China Craton





Author: Pierre Trap - Michel Faure - Wei Lin - Nicole Le Breton - Patrick Monié -

Source: https://hal.archives-ouvertes.fr/



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