The giant tin polymetallic mineralization in southwest China:Integrated geochemical and isotopic constraints and implications for Cretaceous tectonomagmatic event  

作　　者：Yanbin Liu Lifei Zhang Xuanxue Mo M.Santosh Guochen Dong Hongying Zhou 

机构地区：[1]MOE Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China [2]State Key Laboratory of Geological Processes and Mineral Resources,And School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China [3]Department of Earth Sciences,University of Adelaide,SA,5005,Australia [4]Tianjin Institute of Geology and Mineral Resources,China Geological Survey,Tianjin 300170,China

出　　处：《Geoscience Frontiers》2020年第5期1593-1608,共16页地学前缘（英文版）

基　　金：financially supported by the China Geological Survey Program(Grant Nos.1212011121260,1212011220928);the National Natural Science Foundation of China(Project No.491755206)。

摘　　要：The Gejiu-Bozushan-Laojunshan W-Sn polymetallic metallogenic belt(GBLB)in southeast Yunnan Province is an important part of the southwestern Yangtze Block in South China.Tin polymetallic mineralization in this belt includes the Niusipo,Malage,Songshujiao,Laochang and Kafang ore fields in the Gejiu area which are spatially and temporally associated with the Kafang-Laochang and Songshujiao granite plutons.These granites are characterized by variable A/CNK values(mostly>1.1,except for two samples with 1.09),high contents of SiO2(74.38-76.84 wt.%)and Al2 O3(12.46-14.05 wt.%)and variable CaO/Na2 O ratios(0.2-0.65)as well as high zirconδ18O values(7.74‰-9.86‰),indicative of S-type affinities.These rocks are depleted in Rb,Th,U,Ti,LREE[(La/Yb)N=1.4-20.51],Ba,Nb,Sr,and Ti and display strong negative Eu and Ba anomalies.The rocks possess high Rb/Sr and Rb/Ba ratios,relatively low initial 87Sr/86Sr ratios(0.6917-0.7101),and less radiogenicεNd(t)values(-8.0 to-9.1).The zircon grains from these rocks show negativeεHf(t)values in the range of-3.7 to-9.9 with mean TDM2(Nd)and TDM2(Hf)values of 1.57 Ga and 1.55 Ga.They show initial 207Pb/204Pb ranging from15.69 to 15.71 and 206Pb/204Pb from 18.36 to 18.70.Monazite from Songshujiao granites exhibits higher U and lower Th/U ratios,lowerδ18O values and higherεHf(t)values than those of the zircon grains in the KafangLaochang granites.The geochemical and isotopic features indicate that the Laochang-Kafang granites originated by partial melting of Mesoproterozoic crustal components including biotite-rich metapelite and metagraywacke,whereas the Songshujiao granites were derived from Mesoproterozoic muscovite-rich metapelite crustal source.Most zircon grains from the Songshujiao,Laochang and Kafang granites have high-U concentrations and their SIMS U-Pb ages show age scatter from 81.6 Ma to 88.6 Ma,80.7 Ma to 86.1 Ma and 82.3 Ma to 87.0 Ma,suggesting formation earlier than the monazite and cassiterite.Monazite SIMS U-Pb ages and Th-Pb ages of three same granite samples are co

关 键 词：S-type granite SIMS monazite and zircon geochronology Cassiterite U–Pb age Zircon Hf–O isotope Sr–Nd–Pb isotope Yangtze Block 

分 类 号：P618.2[天文地球—矿床学] P597[天文地球—地质学]