The Study Of Magma Mixing Of Haji Granite In West Junggar, Xinjiang

The post-collision granites zone along the Dalabute fault, of which the Haji rocks is the mostimportant one, is the most concentrated zone of the West Junggar granites, where develops quite quantity ofthe Late Paleozoic granites. However, the study of granite on the West Junggar southwest Tangbale mayileis relatively weak. This thesis focuses on the Haji granites in the West Junggar, researching systematicallyfrom the field outcrop surveying, rock observing under the tectonic setting, mather magmas traits, formingmechanisms and the contribution to crust vertical accretion. The results are as follows.1. The Haji granite is composed of host rocks and mafic microgranular enclaves. The host rocksincludes（quartz）diorite granodiorite, porphyritic monzogranite and biotite monzogranite, gushinglyintruding each other. The mafic microgranular enclaves mainly consist of quartzdiorite and dioriteporphyrite, very common in all of the type of host rocks, clear boundary or transitional boundary with hostrocks.2. The Haji rocks develop abundant and typical petrographical evidence of magma mixing.3. The petrochemistry study shows, the host rocks here rich in silicon, alkali and dificit in calciumbelong to A-style granite. According to SiO₂－K₂O, the host rocks here belong to high potassium calciumalkaline rock. It distributes between the peraluminous and subalkaline in the A/NK-A/CNK chart.Therefore, the host rocks here belong to subalkaline-peraluminous A-style granite, rich in potassiumcalcium alkaline.4. The microelement research indicates, the host rocks and the microgranular mafic inclusions are bothrich in Langevin Ion lithophile element,K,Rb,Th,high field-strength element,Zr,Ce,and siderophile elementCo,Ni,Cr,Sc are also relatively rich. They are both deficit in Ba,Sr,Ta,Nb,Hf,Y. The total rare earthelement is similar, that is, rich in light rare earth and low degree of fractionation of heavy rareearth element. Their microelement web figures re similar and the chondritic standardization curve of rareearth element is right sea-gull type.5. It was indicated by the study that the age of the host rock, mafic microgranular enclave and are289±20Ma and291.1±2.80Ma respectively, which is consistent within the range of the error, belonging tothe Early Permian. This illustrates that they are the production of the same event, which give the mostconvincible evidence of the magma mixing.6. According to the geological characters of the nearby regions, the petrographic features of themagma mixing and the geochemistrical and isotopical geochemistrical characters, the researcher concludedthat Haji granite belongs to the Post-collision Granite, which was related with the under-plating of thedepleted magma, standing for a important events of growth of the continental crust in WestJunggar.