Petrogenesis And Tectonic Setting Of Intermediate-acidic Dykes In Suolun, Inner Mongolia

This thesis is based on the intermediate-acidic dykes of Suolun area in the central Great Xing’an Range as the research object.Petrology,zircon u-pb chronology,geochemistry,and Lu-Hf isotopes were used to study the age,genesis,and tectonic setting of medium-acidic dyke rocks,and arrived the following results:The intermediate-acid dykes in suolun area is mainly porphyritic and massive structures,the intermediate dykes are quartz diorite porphyrite and diorite porphyrite,the acid dykes are mainly granitic porphyry and granitic diorite porphyry;The results of ziron U-Pb dating of the two quartz diorite porphyrites are 118.23±0.8Ma、126.2±1.4Ma,the results of ziron U-Pb dating of the granite porphyry are 119.9±1.6 Ma,ircon U-Pb dating results show that they formed at early cretaceous;Geochemical data of intermediate-acid dykes in suolun area shows the characteristics of high silicon,rich alkali,weakly peraluminous-peraluminous,belongs to high potassium calc-alkaline series.Graphic analysis of rare earth elements and trace elements shows that light rare earth elements and some large ion lipophilic elements are relatively enriched while high field strength elements are relatively deficient;Lu-Hf isotopic composition indicate that quartz diorite porphyrite have positive values ofε_Hf（t）+9.8,and young Hf two-s tage model ages766³17Ma,granite porphyry have positive values ofε_Hf（t）+8.7,and young Hf two-stage model ages and 695⁴89Ma,which suggested that the petrogenesis and source material of intermediate-acid dykes are partial melting of crustal material;The intermediate-acid dykes in suolun area formed in extensional tectonic setting and should be the product of orogenic events after the Mongol-Okhotsk Ocean closure.