So far, the widely distributed Neoproterozoic magmatism in the South China Craton (SCC) has been reported by many studies. However, the Paleo- to Mesoproterozoic magmatism has been rarely studied, resulting in a paucity of understanding on Paleo- to Mesoproterozoic magmatism and tectonic evolution of the SCC. In addition, whether or not the SCC was a component of the Paleo- to Mesoproterozoic supercontinent Columbia is a puzzle that geologists have been trying to solve, which requires plenty of Mesoproterozoic rocks to be studied in detail.

FAN Hongpeng, ZHU Weiguang and ZHONG Hong from the State Key of Laboratory of Ore Deposit Geochemistry (SKLODG) at Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) have carried out the research on the Zhuqing mafic intrusions in the Tong’an area, Huili Country, Sichuan Province and reported the results of the first detailed geochronological and geochemical analyses on such newly discovered Mesoproterozoic gabbros in western Yangtze Block, South China.

By Secondary ion mass spectroscopy (SIMS) Zircon and baddeleyite U–Pb geochronology methods, the researchers dated Zhuqing mafic intrusions to be ~1.5 Ga, suggesting that the Zhuqing intrusions was the products of Mesoproterozoic magmatism in the SCC. Geochemical characteristics of all the studied rocks witnessed not only variable degrees of alteration but also high-Ti and alkaline in composition of the intrusions. The results also showed that the Zhuqing gabbros were fractionally crystallized from a parental magma generated by melting of a slightly enriched asthenospheric mantle source in a continental rift environment with no obvious crustal contamination. The researchers found that ~ 1.5 Ga Zhuqing intrusions were likely to be a part of global magmatic events related to activity of mantle plumes during the break-up of the Paleo- to Mesoproterozoic supercontinent Columbia,and the SCC was likely a component of the supercontinent.

The researchers also pointed out that the precise position and role of the Yangtze Block in the assembly and break-up of the supercontinent required further investigation.

The above research is jointly supported by 973 Program (2009CB421003), the Chinese Academy of Sciences (KZCX-YW-136-1), the NSFC (Grants 41273049, 41073043, and 40903022), and a Special Research Fund of the SKLODG, IGCAS.

More details of the research have been published in Lithos (Fan, H.P., Zhu, W.G., Li, Z.X., Zhong, H., Bai, Z.J., He, D.F., Chen, C.J., Cao, C.Y., 2013. Ca. 1.5 Ga mafic magmatism in South China during the break-up of the supercontinent Nuna/Columbia: The Zhuqing Fe–Ti–V oxide ore-bearing mafic intrusions in western Yangtze Block. Lithos 168-169, 85-98).

(By FAN Hongpeng)