Geological characteristics and tectonic environment of Middle Permian volcanic rocks in eastern Pingle depression, Jiangxi Province

Middle Permian volcanic rocks were discovered in the Mingshan area of eastern Pingle depression, and the rock type is mainly composed of alkali basalt, sub-alkaline basalts and andesitic basalt, called Mingshan basalt. The volcanic rocks are sandwiched between Mingshan Formation thin siliceous rocks and siliceous shale, with vesicular structure and a large number of amygdales, about 15m in thickness. The volcanic rocks are characterized by poor silicon, rich iron, high aluminum, low magnesium, Mg^# content ranging from 4.08 to 19.48, relative enrichment of high field strength elements Nb, Ta, Zr, Hf, significant enrichment of U, Th and light rare earth elements (LREE), and (La/Yb)_N content ranging from 3.58 to 72.53, with insignificant Eu depletion (δEu=0.42~0.85) and slightly rightly-oblique REE distribution patterns. Researches show that Mingshan basalt was probably formed in an active continental margin rift basin environment with light rare earth ore source bed; nevertheless, there also exists the evidence arguing that the Dongwu Movement caused the submarine volcanic eruption in South China.