Geochronology and Geochemistry of the Granite Xenolith within the Lamprophyre at the Zhenyuan Gold Deposit(Yunnan Province, SW China)  

作　　者：ZHANG Huichao ZHANG Hongrui HOU Zengqian CHAI Peng ZHOU Kai 

机构地区：[1]Institute of Marine Geology,College of Oceanography,Hohai University,Nanjing 210098,China [2]Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [3]No.208 Team of Geological Survey,China National Nuclear Corporation,Baotou,Inner Mongolia 014000,China

出　　处：《Acta Geologica Sinica(English Edition)》2022年第2期477-489,共13页地质学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 91962105, 41802113);the Fundamental Research Funds for the Central Universities (Grant No.2019B08214);a grant from Jiangsu Provincial “Double Innovation Doctors” Program (Grant No.(2020) 30462)。

摘　　要：The xenoliths in host rocks of hydrothermal gold deposits can generally provide much geochemical information of the deep rocks, which may have an implication for the sources of ore-forming materials. Geochronology and geochemical characteristics are reported for a granite xenolith, which is enclosed by the lamprophyre in the Zhenyuan gold deposit(Yunnan Province, SW China). This granite xenolith mainly consists of K-feldspar, quartz, and plagioclase with trace amounts of magnetite, titanite, apatite, zircon, and sulfides. Zircons from the granite xenolith yield a weighted average U-Pb age of 281.1 ± 1.3 Ma(MSWD = 2.1), which could represent the crystallization age of this granite xenolith. The Ti-in-zircon geothermometer and the Mn concentration in apatite calculate that this granite xenolith formed at 685 ± 43℃ with the logf_(O2) values ranging from NNO + 3.7 to NNO + 6.4. The zircons in the granite xenolith have a restricted range of positive ε_(Hf)(t) values ranging from +9.4 to +10.8, and the corresponding Hf TDM2 model ages range from 588 to 678 Ma. The zircon U-Pb age and the Hf isotopic compositions indicate this granite xenolith within the lamprophyre is mainly derived from partial melting of juvenile crustal rocks before the completed closure of the Ailaoshan Ocean. The pyrites in the granite xenolith have higher Bi concentrations, and lower As, Sb, and Tl concentrations than the gold-bearing pyrites of the ores in the Zhenyuan gold deposit. The low Au concentrations of the pyrites together with the ore-forming age of the Zhenyuan gold deposit(Oligocene) indicate the granite xenolith may have limited contribution to the gold mineralization of the Zhenyuan gold deposit.

关 键 词：granite xenolith LAMPROPHYRE pyrite trace element concentrations Zhenyuan gold deposit 

分 类 号：P618.51[天文地球—矿床学] P588.121[天文地球—地质学] P597.3