The identification of acidic large igneous provinces in the Pinghe River in the early Paleozoic era has progressed

Recently, Dan Wei, associate researcher of Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Associate Researcher Tang Gongjian, Associate Researcher Zhang Xiuzheng and researcher Wang Qiang, and foreign collaborators, with the joint funding of the National Natural Science Foundation of China and the second scientific expedition to the Qinghai-Tibet Plateau, have made new progress in the identification and research of acidic igneous rocks in Pinghe in the early Paleozoic Era. The relevant research papers were published in GSA Bulletin, and the internationally renowned large igneous province research website was also promoted.

Reconstruction of the Ping River acid large igneous province northeast of Gondwana. Photo courtesy of the research team

Like the basic igneous province, the acid igneous province has important research significance in revealing the continental scale dynamic background, continental cracking mechanism, and climate and environment degradation. However, acid igneous provinces are often located on ancient or present-day subduction continental margins, and how to distinguish acid large igneous provinces from subduction-related granite provinces is a challenging exercise. There are a large number of early Paleozoic granites in the Qinghai-Tibet Plateau and adjacent areas, but their dynamic background is fiercely controversial, and existing models include subduction orogeny, post-arc stretching and lithospheric deposition.

Through the comprehensive study of the geological evolution of the early Paleozoic era of the Qinghai-Tibet Plateau-Sanjiang-Southeast Asia, the researchers found that the magmatic rocks in the above areas were mainly formed in 510–460 Ma, mainly composed of S-type granite and a small number of mafic rocks. New paleogeographic reconstruction reveals that it has a distribution area of 2.5 million km2, far from the subduction zone and formed in the intraplate environment. Thus, this period of Cambrian-Ordovician magmatic action fits the definition of an acid large igneous province. According to the largest retained rock mass is the Pinghe rock mass located in Yunnan Province in southeast Tibet, this acid igneous province was named Pinghe acid igneous rock province.

The Pinghe acid igneous province is probably the largest acid igneous province in the world, with characteristics mainly composed of S-type granite, which is significantly different from the typical acid large igneous province composed mainly of type I or A granite/volcanic rocks. The Pinghe acid large igneous province was formed in the northeastern part of the Gondwana continent and was accompanied by the opening of the 510–500 Ma basin. Together with the adjacent 510 Ma Kalkarindji Basal Large Igneous Province of Australia, it had an important impact on climate change in the Cambrian.

This study will have important research significance in enriching the connotation of acid igneous provinces, the role of constrained acid large igneous provinces in continental cracking, and the correlation with climate and environmental changes. (Source: China Science News Zhu Hanbin)

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