The Petrology And Geochemistry Characteristics, Petrogenesis As Well As Geological Significance Of Annual Granite Pluton In The Han Caohu Area, East Tianshan Mountains Of Xinjiang

This paper involves the study about annual granite pluton in the Han Caohu area aroundEast HuangShan ultrabasic rock mass with large-scale.Through the way of studying Petrology,Isotope Chronology and Geochemistry in system, combining the basic-ultrabasic invasionwith the same age, stratigraphic sedimentary sequence and regional structure Characteristics,discusses the Petrogenesis of annual granite pluton in the Han Caohu area,East Tianshan,analyses tectonic environment of HuangShan-Jing Erquan, builds a model of magmatic eventand dynamics of Permian in the area.The annual granite pluton lies in the Han Caohu fornix,includes monzonitic granite,granodiorite, tonalite, syenogranite and quartz diorite from centre to edge.Based on invadingrelationship,the sequence of invading is tonalite,granodiorite, monzonitic granite,syenogranite and quartz diorite.The writer dated the zircons of tonalite with U-Pbisotope,getting diagenetic age of275±2.9Ma(MSWD=4.8),combining with former datas,the diagenetic age of annual granite pluton is about244-275Ma,the major era of Permian.Thestudy of Geochemistry Characteristics shows:all the rock masses are high-K caic-alkaline andcaic-alkaline granite,source region of diagenesis with high pressure,and are full of large ionlithophile element,lacking of high field-strength element Nb,Ta,Ti.On the curve of REEchondrite standardized shows the type of flat and right deviation with fulling of LREE,lacking of HREE.It proves source region and diagenesis environment of different rock massesare similar.But the discontinuation of LREE/HREE,the changes between major element andmicro element and the differences of different ages of rock masses proves the rock masses arenot the result of fractional crystallization from one magmatic event,and there is no fractionalcrystallization between different rock masses.The cause of rock masses is the result ofasthenosphere mantle tholeiitic magma underplates crust-mantle boundary and partly meltsunder the condition of the earth’s crust vertical hyperplasia.In addition,lacking of Mg,Mg#andNi of rock masses proves the rock masses probably are never affected by mantle wedge whichis metasomatosed by subduction plate.The mantle sources are different between annualgranite pluton and basic-ultrabasic rocks.Through this paper’s research,it indicates the lithospheric extension after the collision inHuangShan-Jing Erquan area in Permian.It leads the upwelling of asthenosphere,and thedelamination of lithosphere.The upwelling asthenosphere mantle for one thing warmssubducting mantle fluid metasomatism which produces tholeiitic magma,and the tholeiitic magma rises,forms Huangshan Dong rock mass after fractional crystallization.On the otherhand,the upwelling asthenosphere mantle underplates crust-mantle boundary,and it laeds theearth’s crust vertical hyperplasia which induces partly melting and produces high-Kcaic-alkaline magma.These magmas continuously intrude by stages.Cause of the degrees ofpartly melt and the differeces of rebirth mantle source composition forms annual granitepluton in the Han Caohu area.