| Sanxiangu area is located in the central region of the Nanling,and there are 3smallgraniticintrusions:Sanxiangu,Muyelong?orGaolongshan?and Qincailong?Zhongyeshan?,which are the most exposed plutons in this area,for about1.8km2,3km2,0.5km2,respectively.The sanxiangu granite can be divided into two phases:early?fine?medium-grained biotite monzogranite,a massive structure with a rock-like appearance and a larger exposed area;fine-grained biotite granite has a small distribution area in the late stage,in the form of branches distributed in the former.The research on the assessment of metallogenic potential of Sanxiangu rock body is not enough yet.We compared Sanxiangu area plutons with the Xianghualing Sn?W?-forming pluton and the Yaogangxian W-forming pluton by geochemical methods.We study the items in detail,which include rock-forming age,geological structure setting,major elements,trace elements,rare earth elements and radiogenic heat of Sanxiangu plutons,Xianghualing pluton and Yaogangxian pluton to make evaluation of ore-bearing potential of Sanxiangu plutons.The result of LA-ICP-MS U-Pb dating of Sanxiangu plutons shows that the concordia age of the most concordant 14 points of the sample 13D23 is 152.7±0.6Ma?95%confidence level,MSWD=1.5?and the concordia age of the most concordant 14points of the sample 13D26 is 158±0.8Ma?95%confidence level,MSWD=0.6?.According to geochemical data of Sanxiangu plutons,the average contents of SiO2?Al2O3?K2O and Na2O are 75.1%,12.71%,5.34%,2.91%respectively.And the average content of K2O/Na2O is 1.83.TiO2,MgO and CaO are low,with the average values of 0.17%,0.18%and 0.97%respectively.The average value of P2O5,Na2O+K2O,A/NK,A/CNK are 0.056%,8.25%,1.2,1.03.The mean value of AR,DI,MF are 2.5,91.53,0.90 respectively.Based on the geochemical characteristics of the Sanxiangu area plutons,we can classify the Sanxiangu plutons into high potassium calc alkaline peraluminous granite.For trace elements compositions,such as Rb,Th,U,K,Nb,Nd,Zr,Hf,Sm,Y,Yb,Lu have obvious enrichment characteristics.Under the general enrichment background,it occurred to the relatively loss of Ba,Sr and Ti.The?REE is between 298.0×10-66 and369.3×10-6,with mean value of 328.3×10-6.The average value of LREE/HREE is5.88,the average value of LaN/YbN is 5.88,which is characterized by heavy fractionation of rare earth elements and relative enrichment of light rare earth elements,negative Eu anomaly,ranging from 0.09 to 0.3.The chondrite-noemalized pattern of rare-earth elements is characterized by seagull form with Eu's strong loss.The?Nd?t?values of the rock mass are-8.6 to-6.5?average-7.3?for the early granite and-6.9 to-6.6?average-6.75?for the late granite.The Nd model ages of the Sanxiangu plutons are T2DMDM of early granite ranging from 1469 to 1632 Ma,average 1530 Ma and T2DM of late granite ranging from 1470 to 1488 Ma,average 1479 Ma,respectively.The character indicates that the granite in Sanxiangu area is from the remelting of the middle Proterozoic group strata,and low Nd model age indicates that the mantle materials are involved in the diagenetic process.The QA of Sanxiangu plutons is between 62.32×10-6Jg-1·a-11 to 90.57×10-6Jg-1·a-1,with average value of 76.9×10-6Jg-1·a-1.The calculation results showed that the QA of Sanxiangu plutons is higher,as well as Xianghualing pluton and Yaogangxian pluton.The contents of W,Sn,Pb and Zn are higher in granite,and the wall rock alteration of the contact zone of rock mass and surrounding rock is stronger and Tungsten tin mineralization point is widely distributed.According to the comprehensive analysis of the rock-forming age,lithogrochemistry and the geological structure position of granite in Sanxiangu area,it is considered to Sanxiangu plutons have a good metallogenic ability of tungsten tin polymetallic mineralization. |
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