GEOLOGY AND GEOCHEMISTRY OF THE SHUIQUANGOU WEAKLY-ALKALINE COMPLEX OF NORTHERN HEBEI AND ITS TECTONIC ENVIRONMENT

The Shuiquangou pluton in the Chongli Chicheng area, northern Hebei, is a potassic to high potassic complex consisting of calc alkaline, weakly alkaline and alkaline rocks, characterized by enrichment in alkaline, subaluminium, low Ca and Ti. REE, trace element and isotope geochemistry indicates that the complex originated near the boundary between the upper mantle and lower crust. Most data are plotted in the field of the volcanic arc on various geochemical tectonic discrimination diagrams. Study on the emplacement mechanism for the complex implies that it was generated under the tensional tectonic environment. On the basis of the isotope ages, it is considered that the complex was formed in the period of stress relaxation after the collision between the Siberian and Sino Korean plates.