PETROGEOCHEMISTRY AND ORIGIN OF THE CENOZOIC VOLCANIC ROCKS IN FUXIN-ZHANGWU AREA, WESTERN LIAONING PROVINCE

The Fuxin-Zhangwu area in Western Liaoning Province saw two Cenozoic volcanic cycles, i.e. the Paleogene Paleocene Nalishan cycle and Neogene Miocene Chuandishan cycle. During the 1:250 000 regional geological survey, detailed study and redefinition are carried out on the basis of petrology, petrogeochemistry, volcanic cycle, regional comparison and previous literatures. The volcanic lava of each cycle evolves from basic to intermediate-basic, with characteristics of increasing sodium, silicon and aluminum, but reducing iron and magnesium. The distribution pattern curves of transitional elements of the volcanic rocks are coordinated and consistent as obvious V-shape, which indicates the differentiated product from comagma. The meta-alkaline rocks are enriched in REE; while the normal rocks are poor in REE. The rocks are characterized by enrichment of LREE with well fractionation and depleted in HREE with poor fractionation. The LREE/HREE value is between 8.2 and 18.84, with Sm/Nd between 0.12 and 0.24, Eu/Sm between 0.2 and 0.86, showing that the magma is mainly originated from mantle source.