首页|Late Devonian transition from advancing to retreating subduction in the SW Central Asian Orogenic Belt: Insights from multiple deformation and magmatic events in the southern Yili Block, NW China
Late Devonian transition from advancing to retreating subduction in the SW Central Asian Orogenic Belt: Insights from multiple deformation and magmatic events in the southern Yili Block, NW China
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NSTL
Elsevier
In order to better constrain the Late Paleozoic tectonic evolution of the SW Central Asian Orogenic Belt, we conducted field structural investigations, zircon U-Pb dating, whole-rock geochemical and Sr-Nd iso-topic studies on the meta-sedimentary rocks and intruding granites and mafic dykes in the Dahalajunshan area, southern Yili Block of NW China. Our results allow us to recognize five tectonic/mag-matic events. Field-scale and microscopic structures of the low-grade meta-sedimentary rocks showed a regional top-to-the-SE thrusting (Event 1). Undeformed granites that contain dioritic enclaves (Event 2) crosscut the regional foliations and thus post-date Event 1 after ca. 379-369 Ma. Mafic dykes intruded all these rocks after-328 Ma (Event 4-1), posterior to brittle-ductile thrusting (N-S contraction) (Event 3) and prior to normal faulting (N-S extension) (Event 4-2). All the magmatic rocks formed in a subduction-related setting. The granites and dioritic enclaves derived from a mixing of crustal-and mantle-derived sources variously modified by slab-derived hydrous melts. The primary magma of the diabase dykes derived from a mantle source modified by the slab fluids with 5% crustal contamination. Variation from regional compression (ductile and brittle-ductile thrusting) to extension (normal faulting) and increasing mantle input in arc-related magmatism reveals a transition from Early Paleozoic advancing subduction (events 1 to 3) to Late Paleozoic retreating subduction (events 4-1 and 4-2) of the Junggar oceanic plate beneath the Yili Block.(c) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
NSTL
Elsevier
