PETROGEOCHEMISTRY AND ORIGIN OF THE EARLY TRIASSIC JIANSHANZI VOLCANIC ROCK IN NORTHERN LIAONING PROVINCE

The Early Triassic Jianshanzi volcanic rock in northern Liaoning, which was established by the Project of 1:250 000 Regional Geological Survey, is limitedly exposed, without regional extension. On the basis of the regional geological survey, this article studies the petrology, geochemistry and genesis of the volcanic rock. The result shows that the volcanic rock evolves from basic through intermediate to acidic, with characteristics of high-K, Si and Al and lowFe, Mg and Ca. The distribution patterns of transition elements of this volcanic rock are generally consistent, suggesting a comagmatic origin. The meta-alkaline rocks are REE-rich; while the normal rocks are poor with REE. The rocks are characterized by enriched LREE with well fraction and depleted HREE with poor fraction, with LREE/HREE values ranging from 7.75 to 18.45, Sm/Nd values of 0.14-0.21, and Eu/Sm values of 0.24-0.37, indicating that the magma of the Jianshanzi volcanic rock is originated from mantle source.