GEOCHEMISTRY AND GENESIS OF THE METAMORPHIC ROCKS OF LIAOHE GROUP IN HUANGQI AREA, LIAONING PROVINCE

Huangqi area is tectonically located in the southeastern end of Yingkou-Kuandian anteclise of Jiao-Liao platform uprise in the east of Sino-Korean paraplatform. The study area belongs to the east of Early Precambrian tectonic division of Eastern Liaoning, where Mesozoic magmatic complex and Paleoproterozoic magmatite and strata occur and Paleoproterozoic Liaohe Group is widely developed. Metamorphic rocks are mainly schist, granulite, leucoleptite, arkose quartzite, calcsilicate rock and marble. The petrochemical characteristics of the metamorphic rocks are as follows: 1)The average content of SiO₂ in silicate rocks is 47.32%-78.6%, generally K₂O>Na₂; 2)Carbonate rocks are generally rich in Ca and Mg, with CaO>MgO. The metamorphic rocks in Liaohe Group take very similar trace element content, high content of F and Rb and relatively high Clarke values of concentration. The REE average ΣREE of the metamorphic rocks is 205.9×10^-6, with average LREE/HREE of 12.8 and δEu of 0.56. The REE distribution pattern is gently gradient to the right, with better differentiation of LREE than that of HREE, enrichment in LREEs and negative Eu and slightly negative Ce anomalies. Combining with the characteristics of protolith formation of Liaohe Group regionally, it is concluded that the study area was a geosyncline tectonic setting in Paleoproterozoic Era, reflecting that Liaohe Group strata formed a complete volcanicsedimentary formation series on the whole.