| Banla mountain granodiorite is located in xiwuqi area of Inner Mongolia,and its tectonic position is located in the great xingan range magmatic belt of the offshore Pacific tectonic domain.Based on the detailed study half mountain granodiorite,on the basis of field geological characteristics of half mountain granodiorite of petrology,geochemistry and zircon U-Pb isotope and so on has carried on the comprehensive system research,summarizes the half mountain granodiorite characteristics of petrological and geochemical characteristics,discusses the half the reasons for the formation of granodiorite and tectonic environment.Banla mountain granodiorite intrudes into the southern zone of the southern zone of diyanmiao ophiolite.The lithology is mainly medium-fine granodiorite,the main mineral components are plagioclase(40%?45%),quartz(20%?25%)and potassium feldspar(20%?25%),and the dark minerals are amphibole(10%±)and biotite(5%).According to the dating results of la-icp-ms zircon u-pb,the isotopic age of banlashan granodiorite is 132.16±0.75Ma,belonging to the early cretaceous.According to the analysis of main elements and rare earth trace elements,Si O2=66.82%?67.29%,Al2O3=15.73%?15.99%,Fe2O3=3.88%?5.14%,Na2O=3.86%?4.50%,K2O=3.23%?3.92%,Mg O=0.64%?1.13%,Ca O=1.31%?2.12%,Na2O+K2O=7.10%?8.15%,Na2O/K2O=2.03?2.20,A/CNK=0.97?0.99,indicatin g that banlashan granodiorite is an aluminite with high alkalinity.The character istics of light rare-earth are relatively enriched right-leaning curve,while the di fferentiation of heavy rare-earth is not obvious.The rare-earth distribution curv e shows that light rare-earth is slightly enriched,while heavy rare-earth curve i s relatively straight.According to the geochemical characteristics of banlaishan granodiorite and the regional research progress,the early cretaceous banlaishan granodiorite may be the product of orogenic extensional background after the closure of the mongolian-okhotsk ocean. |
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