It is general considered that deep mantle upwelling (mantle plume) play an important role for breakup of Supercontinents. However, multistage rifting and associated magmatic activities are general occurred preceding extensive mantle plume magmatism. Therefore, the knowledge of origin of the preceding magmatic rocks is a key for understanding mantle plume formation and mechanism of supercontinent breakup.

The South China Block is important for investigating the link between mantle plume and breakup of Rodinia supercontinent because it preserved the key records related to assemble and breakup supercontinent Rodinia. Huangshan and Meiling volcanic rocks, two sets of preceding Neoproterozoic bimodal volcanic rocks, exposed along southeastern margin of the Yangtze block. These two bimodal rock unites provide a rare chance to test the potential link between mantle plume and the breakup of supercontinent Rodinia. We presented comprehensive zircon U-Pb geochronology, petrological and geochemical data for the two volcanic rock units. The ~860 Ma Huangshan basalts are arc-like intraplate ones, showing enrichment of water with pre-eruption magma water content of about 3.6%.

In contrast, the ~840 Ma Meiling basalts display typical OB-type incompatible trace element distribution patterns with an anhydrous signature. These indicate that before the arrival of ca. 825 Ma mantle plume beneath the South China Block, the mantle has been metasomatized by water/fluids, which significantly reduced the mantle solidus and resulted in partial melting, as well as associated crustal extension and rifting events. We proposed that these water/fluids are likely from the dehydration of a stagnated slab in the mantle transition zone. This study indicates that mantle avalanche and dehydration of stagnant slabs in the mantle transition zone probably triggered the deep mantle upwelling and subsequently breakup the supercontinent Rodinia.

This study was conducted by candidate Doctor Lyu Pu-Liang under the supervision of Professor Li Wu-Xian from Guangzhou Institute of Geochemistry, Chinese Academy of Sciences and Associate Professor Wang Xuan-Ce from Curtin University, Australia.

Lyu, P. L., Li, W. X., Wang, X. C., Pang, C. J., Cheng, J. X., Li, X. H. (2017). Initial breakup of supercontinent Rodinia as recorded by ca 860─840 Ma bimodal volcanism along the southeastern margin of the Yangtze Block, South China. Precambrian Research, 296, 148-167.

http://www.sciencedirect.com/science/article/pii/S0301926817300153