Abstract:Guandimiao rare earth deposit is located in the surrounding area of Xishan rare earth deposit. It belongs to Luxi(western Shandong province) rare earth metallogenic belt in eastern margin of the North China Craton. In order to reveal magma origin and evolution mechanism in the area, petrological, geochemical and chronological characteristics of Guandimiao alkaline complex have been studied, and the origin of Mesozoic magma, evolution and formation of tectonic environment have been discussed. The main rock types of Guandimiao complex include amphibolite, syenite and quartz syenite. The geochemical characteristics indicate that the complex has a calc alkaline alkaline evolution trend. It is rich in large ion lithophile elements, such as K, Rb and Ba; and poor in high field strength elements, such as Nb, Ta, Ti. There is a strong fractionation between light rare eart and heavy rare earth. As showed by LA ICP MS zircon U Pb dating, the age of syenite is (128.1±0.6) Ma, and the age of diopside quartz syenite in Xishan area is (130.1±1.4) Ma. They both belongs to the intrusion of Yanshan period. The ε Nd (t) value of he complex is 8.6~7.91, which is consistent with the ε Nd (t) values of 8.7~8.1 in Xishan area. As showed by the discrimination diagram of Rb(Yb+Ta) and lg［CaO/(Na2O+K2O)］ SiO2 structures, the complex was formed in a volcanic arc environment. As showed by comprehensive research, Guandimiao complex has geochemical characteristics of island arc magmatic rocks. The magma may originate from enriched mantle, and are mixed with a small amount of crustal material from the North China Craton. The diagenetic and ore-forming events in the area are the products of Mesozoic magmatic tectonic thermal mineralization events in western Shandong province under the background of subduction of the Pacific Plate towards the North China Craton.
