Geochemistry and LA-ICP-MS zircon U-Pb chronology and genetic mechanism of the Early Jurassic coarse to medium grained biotite monzogranite:a case study of the Chaoman Forest Farm area in the Northern Great Xing'an Range
The study focuses on the coarse to medium grained biotite monzogranitein Chaoman Forest Farm on the northern edge of the Erguna Block in North Great Xing'an Range.Adopting geological sur-veys,rock geochemistry,and LA-ICP-MS zircon U-Pb geochronology research methods is to analyze the petrological,major element,trace element,and chronological characteristics of the coarse to medium grained biotite monzogranite and to discuss its genesis mechanism and tectonic environment.The results show that the coarse to medium grained biotite monzogranite in the Chaoman Forest Farm area has I-type granite characteristics and belongs to weakly peraluminous and high potassium-cala-alkaline gran-ite,the w(SiO2)of monzogranite is 68.92％-72.44％,w(Na2O)is 4.65％-4.85％,w(K2O)is 3.33％-4.41％,andw(Al2O3)is 15.25％-16.75％,rittman index(a)is 0.95-2.84.Total rare earth content is(101.24-152.40)×10-6.There are significant fractionation of light and heavy rare earths,enrichment of light rare earths,loss of heavy rare earths,enriched in elements such as Rb,Th,Ce,Zr and relative-ly depleted in elements such as Ta,Nb,P,and Ti.The magma of the coarse to medium grained biotite monzogranite originates from the partial melting of newly accreted lower crustal materialand was formed in the Early Jurassic(192.1±1.6)Ma.The tectonic environment of the Early Jurassic coarse to medi-um grained biotite monzogranite in the study area is an active continental margin volcanic arc environ-ment related to the south ward subduction collision of the Mongolian-Okhotsk Ocean.This result pro-vides evidence for the study of the tectonic background and chronology of the coarse to medium grained biotite monzogranite in the Chaoman Forest Farm area of the northern section of the Great Xing'an Range.
LA-ICP-MS zircon U-Pb chronologygeochemistrycoarse to medium grained biotite monzograniteEarly JurassicChaoman Forest FarmNorth Great Xing'an Range
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