The Central Asian Orogenic Belt (CAOB), characterized by its significant Phanerozoic accretion, develops tremendous post-Carboniferous granites in its southern part and their origins are still unclear, hindering our understanding on the CAOB late-staged evolution, especially its crust growth history. Herein, we presented zircon U-Pb-Hf-O and whole-rock geochemical and Sr—Nd isotopic data for the granitic rocks of early Permian (minor late Carboniferous) from the Khan-Bogd area in southern Mongolia. These early Permian granitic rocks formed at ∼280–290 Ma, together with the coeval previously-studied A-type granites there, are mainly high temperatures (∼800–960 °C) granitic rocks and have contributions of deep substances such as relicts of oceanic slab, lithospheric or asthenospheric mantles, as suggested by their zircon Hf[sbnd]O, and whole-rock Sr[sbnd]Nd isotopes. Similar cases occurred commonly in other areas of southern CAOB and we infer that this is related to a significant shift of the early Permian non-subduction-related magmatism from the earlier arc magmatism. Combined with the accompanying significant contraction of the Paleo- Asian Ocean (PAO), we concur the occurrence of the closure of multiple secondary oceans of the PAO and later accompanying slab-breakoff occurred commonly after the Carboniferous in the southern CAOB. Thus, we propose that the relicts of oceanic slabs, as an important magma origin of these post-Carboniferous granites, were reasonably caused by the commonly-occurred slab breakoff and therefore, it is of great importance for the vertical accretion of the post-Carboniferous evolution of the CAOB, rather than mantle plume and other models.
Bibliographical noteFunding Information:
The details of the analytical methods, supplementary figures and tables and related references can be seen in the Supporting information (supplementary materials). This research was financially supported NSFC Project ( 42102260 , 41730213 , 41890831 , 42072267 , and 41972229 ), Hong Kong RGC GRF ( 17307918 ), and HKU Internal Grants for Member of Chinese Academy of Sciences ( 102009906 ) and for Distinguished Research Achievement Award ( 102010100 ), the Fundamental Research Funds for the Central Universities , CHD ( 300102272204 ), and Natural Science Foundation of Shaanxi , China ( 2020JQ-353 ).
© 2023 Elsevier B.V.
- Closures of multiple secondary oceans
- Mongolia Collage System
- Relicts of oceanic slabs
- Slab breakoff
- Southern Central Asian Orogenic Belt