Publication Name
Earth-Science Reviews
Abstract
Widespread igneous rocks were emplaced in the eastern South China Bolck (SCB) from the Jurassic to the Cretaceous period. These rocks include granitoids and rhyolites, and minor mafic and rare intermediate igneous rocks, of unclear geodynamic origins. We compiled 780 published igneous rock ages to age-code a 1:500, 000 digital geological map, which was then used to analyze the spatio-temporal evolution of the associated magmatism. Regional igneous rocks can be divided into four major emplacement episodes: 190–175 Ma, 165–155 Ma, 145–125 Ma, and 105–95 Ma, with the first two episodes dominated by intrusive rocks emplaced in the Jurassic in inland South China (~550–1200 km away from the trench), and the latter two episodes mostly eruptive rocks emplaced in the Cretaceous along coastal areas (~400–800 km away from the trench). To investigate the association of these events with the history of subduction, we calculated the slab flux along eastern China using two published global plate tectonic reconstructions. We found that the slab flux (per kilometer) between ~145 Ma and 120 Ma along eastern China was up to 0.018 km /yr, which is much larger than the global average for the last 200 Myr (0.005 km /yr); this period of large slab flux largely coincides with Early Cretaceous magmatism in the region. Combined with the geochemical characteristics of these rocks, we propose that Cretaceous magmatism in South China was related to underplating caused by dehydration of the subducting Izanagi slab. In contrast, the slab flux was much lower (0.003–0.007 km /yr) during the period of Jurassic magmatism. We used the two considered plate reconstructions to drive three mantle flow models, which predict that upper mantle upwellings occurred beneath the SCB in the Jurassic, triggered by subducting slabs. A hydrous mantle transition zone, which could have developed due to long-term subduction around the SCB, is likely to have facilitated these mantle upwellings and caused partial mantle melting. We propose that these mantle upwellings and associated hydrous melting, could have caused the melting of continental crust and induced Jurassic intraplate magmatism in the SCB. 2 2 2
Volume
217
Article Number
103605
Funding Number
LP170100863, IH130200012
Funding Sponsor
Australian Research Council