Petrologic Characteristics And Chronology Of The Ailingou Pluton In Jiefangyingzi Neimenggu

Granite is the signature of the continents,Containing great informationabout the inside of earth. Study related to granite can help us know more about theregional tectonic history, give us a deep insight about the formation and evolution ofthe continent, and speculate the tectonic setting.The study area is located on the north margin of the NCC,adjacented to theaccretion zone of the North China Craton (or NCC), with the Xilamulun suture zoneas its north edge to Xiboliya plate, the Chifeng-Kaiyuan fault zone as its south edge toNCC. It has got great controversy about the formation of Xilamulun suture zone andthe collision era between Xiboliya plate and NCC. Widely spreaded in theAilingou-Yongshenghao Jiefang country, the scale of Ailingou granite is great. So thestuding about their petrologic, geochemical characteristics and chronology, formationrelate to the suture zone may help us great significance to know about the regionaltectonic history more accurately.This thesis sum up the filed，Having doing much field research,getting a clearview about its country rock and field characteristics,geochemistry and isotopematerial, and systemically analyze the petrologic, geochemical and isotopecharacteristics of Ailingou granite. It can be concluded that:1.The mineral composition of Ailingou-yongshenghao granite are alkali feldspar,plagioclase, hornblende and biotite. The major rock types are monzogrnite,porphyritic granodiorite and course-fine granodiorite;2. In Ailingou-yongshenghao granite belongs to high-K calc-alkaline, ismetaluminous. Overall, its geochemical characteristic is similar with I-type granite.3.Combining its field characteristics with the result of U-Pb analysis in zircon(227.0±1.6Ma), the formation time of Ailingou-yongshenghao granite is about latestage of early Triassic;4.Ailingou-yongshenghao granite have relatively high REE abundance, and arecharacterized by relative enrichment in LREE, and depletion in HREE, and obviousnegative Eu anomaly (Eu/Eu*=0.16-0.21). Chondrite-normalized REE distribution pattern shows steep dip to the right. Trace-elements and REE distribution patterns andratios imply that the primary magma of Ailingou-yongshenghao granite should beremelting of overthickened continental crust. According to the former study, theXilamulun suture zone has formed, so the intrusion of magma has no directrelationship to it. Instead, it is formed in orogeny setting, which is caused by thedownthrust of Xiboliya plate to the NCC.5.In the late stage of early Triassic, Ailingou-yongshenghao granite formed in orogenysetting. Connecting with the regional tectonic history, it can be demonstrated that thecollision between Xiboliya plate and NCC happened in Triassic, and ended about lateTriassic-early Jurassic.