The Discussion Of Characteristics And Tectonic Settings Of Mesozoic Granitoids In Haoraoshan Area,zhalantun,Inner Mongolia

Daxing'anling as one of the key areas in Xingmeng orogenic belt has always been concerned by geologists.Research area is located in northern section of Daxing'anling.Based on the study of granite in research area,we summarized its features of petrology and geochemistry and discussed its petrogenesis and tectonic significance.The results show that,the granites in Haoraoshan area is broadly divided into two categories,One kind is quartz monzonites with alkali-rich,calcium-rich,aluminum-rich characteristics,are transited from metaluminous to peraluminous,and have low content of Si,K,high Sr and LILE content.However,the strongly depletion of Nb,P,Ti is a typical character of I-type granite,proved they formed in the compressional tectonic environment;The other is Granitoids,the granites have high SiO2 rare earth elements(REE),high fieldstrength elements(HFSE),and large ion lithophile elements(LILE)contents.The REE patterns are characterized by enrichment of LREEs relative to HREEs and distinct negative Eu anomalies in chondrite-normalized REE diagram,which is characterized by right oblique and"V"-shaped feature.With a typical character of S-type granite representing an extensional tectonic environment.The monzonite-diorites in Haoraoshan area may have formed in the active continental margin tectonic backgrounds and the compressional conditions belonging to the product of the late stage of continental plate collision.The monzonitic granite which is the S-type,formed in the extensional environment.The magmatism of Haoraoshan region unitary transited from the I-type to the S-type showed that the late Mesozoic tectonic of the study area occurred in the background of Pacific plate subduction underneath the East Asian continent,and also probably affected by the late stretch evolution of Mongol-Okhotsk orogeny.