The transition from continental to lithospheric breakup recorded in proto-oceanic crust: Insights from the NW South China Sea
| Autor: | Peng Chao, Gianreto Manatschal, Cuimei Zhang, Pauline Chenin, Jianye Ren, Xiong Pang, Jingyun Zheng |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | GSA Bulletin. 135:886-902 |
| ISSN: | 1943-2674 0016-7606 |
| DOI: | 10.1130/b36371.1 |
| Popis: | The formation of a new plate boundary and creation of the first oceanic crust, two of the most important processes of plate tectonics, still remains little understood. While older studies used to assumed a sharp ocean-continent boundary between continent and ocean, recent studies suggest a progressive oceancontinent transition (OCT) between unequivocal continental and oceanic crusts. In the latter view, breakup is not instantaneous but a lasting phase, which raises questions about the nature of the OCT basement and the processes operating between continental and lithospheric breakup. Based on detailed observations of high-quality and yet unpublished reflection seismic data, we describe and interpret the characteristic structures of the NW-South China Sea OCT and their relationship with overlying syn-breakup phase sediments. We show that the OCT displays a transition from fault-dominated rifting to magma-dominated seafloor spreading. On its continent-ward side, the OCT is made of hybrid crust where tectonic thinning of continental crust is compensated by syn-extensional magmatic thickening. Oceanward, the hybrid crust evolves into a fully magmatic but fault-dominated proto-oceanic crust, and finally turns into a mature Penrose-type oceanic crust. Relying on the growth structures observed in the syn-breakup sedimentary sequences and magmatic additions, we propose a kinematic restoration of the breakup phase. We suggest out-of-sequence flip-flop faulting to explain the switch from asymmetrical, fault-dominated-extension, to fully magmatic and largely symmetrical syn-extension accretion recorded in the syn-breakup sedimentary sequences overlying the OCT. |
| Databáze: | OpenAIRE |
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