A Study On Petrogenesis Of The Instrusive Rocks Of Maxindaban Area Of The East Kunlun Region During Indosinian

The granitic pluton of Maxingdaban region is a part of the East Kunlun Qimantag magmatic belt,which is geologically significant to the study of Qimantage region and tectonic evolution of the East Kunlun,and closely related to regional multimetallic deposit.But there are not enough data about mineralogy,chronology,geochemistry and genesis of the pluton of this region.This paper makes detailed geological surveys,petrology and mineralogy studies of Maxingdaban pluton mainly,including Yazigou pluton and the Kendekeke magmatic rocks,on the basis of which,by means of LA-ICPMS zircon U-Pb Chronology,zircon Hf isotopic composition,the rock major measured elements,rare earth element and Sm-Nd isotope,the following recognitions can be concluded:The main rock type of the Maxingdaban granitic pluton is most of monzogranite and followed by.granodiorite.The paper major reseaech is the monzogranite.Whole-rock analysis shows Si02 68.61%?69.37%,P2O5 0.11%?0.12%,K20 3.95%?4.08%,low of FeO*/MgO 4,02?4.21,Aluminum Saturation Index A/CNK(0.96?0.99)<1,which must be high-K calc-alkaline series and metaluminous granite,it represents the features of I-type granite.According to the REE partition diagram and spider diagram,the granite shows a marked chemical as continental arc granite,exhibiting enrichment in LILEs Rb and Th,but depletion in HFSEs Sr?P?Ti?Nb and Ta.Mineral electron microprobe results show that amphibole is Ferro-edenit,biotite is siderophyllite,plagioclase is oligoclase,alkali feldspar is orthoclase.The genetic of various minerals shows the source of granite most from crust,mixs with some mantle material.?Na(t)(-2.5?-3.2)and 143Nd/144Nd(0.512326?0.512340)imply the granite shares the feature of crust-mantle mixed ?-type granite.Based on LA-ICPMS zircon U-Pb dating,the emplacement of the Maxingdaban granitic pluton occurred at 218 ± 2Ma.zircon?Hf(t)is-4.43?-0.62,176Hf/177Hf ratio is low(0.282517?0.282623),which may indicate that mantle source(large positive ?Hf(t))and ancient crust(large negative ?Hf(t))had mixed.The accordance of tDM2(1.20?1.25Ga)of Nd and tDM2(1.08?1.28Ga)of Hf leads to the conclusion the crust-mantle differentiation take place at Mesoproterozoic in Qimantag area and indicates the source of the granite maybe partly from the pre-Mesoproterozoic materials.The main rock type of the Yazigou granitic pluton is monzogranite.In the mineral composition,there is no amphibole,the biotites are haughtonites,plagioclases are mainly andesines and some oligoclases,all the alkali-feldspars are orthoclase.It indicates that Yazigou and Maxingdaban granitic pluton are similar in mineralogical characters:SiO2=65.21%?67.3%,K20=4.54%?5.26%,FeO*/MgO=3.10-3.3,Eu negative anomaly(SEu=0.69?0.79),(La/Yb)N= 4.21?7.30.enriched in LREE and LILE(U,Th),relatively depleted in HREE and HFSE(Nb,Sr,P,Ti),apparent differentiation between LREE and HREE.The REE partition diagram and spider diagram shows the similarity of magma source of Yazigou and Maxingdaban pluton.The magmatic rocks of Kendekeke are gabbro diorite and monzogranite with MME.The REE partition diagram,spider diagram and formation age is similar with the Maxingdaban pluton,indicate that they are from comagmatic region.It also shows that the dynamic background is mixing of crust-mantle magma and underplating mantle magma,which is similar to the regional tectonic background.The accordance of chronology,geochemical characteristics about the Maxingdaban granite and the Qimantag Triassicepoch lava.It is suggested that the Maxingdaban granitic pluton emplaced at the same time with the Qimantag late Triassic volcanic rock,when the Paleo-Tethys Ocean was closed,the context of the continent-continent collision.The Kendekeke Iron cobalt Multi-metal deposit and Maxingdaban granitic pluton is similar in the space,age and geochemical characteristics.It can be indicated that the substance source of the deposit is related to the ore-bearing fluids in the magma of Maxingdaban granite.