Generation of Late Cretaceous Ji’an basalts through asthenosphere-slab interaction in South China
| Autor: | Yangming Wu, Feng Guo, Melesse Alemayehu, Guoqing Wang, Xiaobing Zhang, Bo Zhang, Xuan-Ce Wang |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | GSA Bulletin. 132:1316-1332 |
| ISSN: | 1943-2674 0016-7606 |
| DOI: | 10.1130/b35196.1 |
| Popis: | Recycled crustal components have been widely identified in the source of continental basalts with geochemical features similar to oceanic island basalts (OIBs). However, the mechanism of how these recycled materials are involved remains highly debatable. Here we conduct comprehensive geochemical analyses (including whole-rock, olivine, and melt inclusion) and numerical modeling on Late Cretaceous Ji’an basalts from South China interior, aiming to investigate the possible role of recycled crustal components in basalt petrogenesis driven by the subducted paleo-Pacific oceanic plate. The Ji’an basalts show geochemical characteristics akin to OIBs and have depleted asthenospheric mantle-like Sr-Nd-Pb-Hf isotopic compositions with moderately radiogenic Os. Their olivine-hosted melt inclusions have low H2O and highly negative δD values and olivine phenocrysts are mainly characterized by depletion of 18O with δ18O values lowering to 3.9‰. These features are consistent with positive Sr and Eu anomalies in some whole-rock samples. The combined geochemical data suggest that the primary magmas were derived from an asthenospheric mantle enriched by melts from an altered gabbroic oceanic crust, which had experienced intensive dehydration. Further numerical modeling shows that melting of the dehydrated oceanic crust can occur along the torn flank of the subducting lithosphere, in the case that the slab is strongly thinned and fractured. The low δ18O preserved in olivine and the estimated slab age ( |
| Databáze: | OpenAIRE |
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