Geological Geochemical And Chronological Characteristics Of Ikes In Motianling Granite

Motianling granite is one of the oldest granite which have uranium deposit inSouth China.The granite is distributed of different sizes of dikes,which containsfine-grained granite,greisen,albitite,mafic rocks and so on..The relationship betweendyke and Motianling granite are sudden or gradual change.In this paper,the authormakes research on geological and geochemical characteristics and the zircon U-Pbages,and explores the geological significance of the dikes,which mke use of themethods of Petrology,Geochemistry and Isotope geochronology,on the basis ofprevious result.The fine-grained granite and greisen are formed by a kind of advanced residualmagma which contains of gases.It is resemble of the feature of constant elementbetween dikes,but,the difference in large is Na between them.The feature of constantelements between fine-grained and Motianling granite is similar.The contents ofCa,Mg,Mn,Ti in fine-grained granite is low to the Motianling granite.And thefine-grained granite Strongly losses of the Mn and enriches of Ca,comparing ofChinese and globe granites.The mafic rock in the study area have the higher ofTi,K,P,Fe,and have the lower of Mg,Ca,Na.The trace element characteristics of dikesare similar,and shows poor of Ba,Sr,and rich of U,K,Pb,P.REE characteristics of thedikes show a right-wing―pigeontype‖curve.It is highly similar of the REE patterns ofdifferent vein rock.The greisen is higher than the fine-grained,fine-grained granite ishigher than the mafic rock in the REE contents.The negative Eu anomalycharacteristics is very obvious on REE distribution curve,which indicating that thediagenetic magma may have been experienced a high degree of fractionalcrystallization.The ratio of the dikes are between1.73and6.8,which shows the lightrare earth element enriched. Fine-grained granite is S-type granite in the genesis,or some of the characteristicsof the A-type granites,which belong to orogenic or rift granite in the tectonicenvironment.The results of LA-MC-ICP-MS zircon U-Pb dating of the dikes shows that theM016greisen is age of786±14Ma,The M021-2greisen is the age of741.8±1.9Ma,theM040fine-grained granite is the age of782.5±2.5Ma,the M062-3fine-grained graniteis the age of828±50Ma,the M063-1albitite is age of797±39Ma,the M068mafic rockis the age of826±44Ma.The age of the dykes are concentrated in about800Ma.Theage is the same between dykes and Motianling granite.The Th/U is over0.1which themajority is between0.3and1.2,U content has a significantly positive correlation withTh,which shows that the zircon are the characteristics of the composition of magmaticzircon. Besides the900-1600Ma age datas show that the inherited zircon is on thezircon samples,in the dikes.