摘要
为确定新疆东天山阿奇山铅锌矿床的形成时间,采用LA-ICP-MS原位U-Pb同位素分析方法对矿体附近的石榴子石进行年代学研究。阿奇山铅锌矿区分布有大量层状石榴子石矽卡岩,与矿体产状一致,经岩相学观察,石榴子石主要为灰绿色(AQ4801)、褐色(AQ4803)。其中灰绿色石榴子石样品无明显蚀变特征。褐色石榴子石碎裂结构发育,裂隙充填金属硫化物。电子探针成分分析结果表明石榴子石为钙铁榴石-钙铝榴石系列(AQ4801 And_(97)Gro_(2)~And_(50)Gro_(48);AQ4803 And_(96)Gro_(2)~And_(28)Gro_(70))。LA-ICP-MS原位U-Pb同位素分析测试结果显示AQ4801与AQ4803具有较高的U含量,分别为1.0×10^(-6)~32.2×10^(-6)、5.4×10^(-6)~61.2×10^(-6),^(206)Pb/^(238)U加权平均年龄为(314.6±3.9)Ma (MSWD=1.15),(323±15) Ma (MSWD=0.6),表明阿奇山铅锌矿床形成于早石炭世末—晚石炭世初(323~314.6 Ma)。
In order to identify the formation time of the Aqishan Pb-Zn deposit in the eastern Tianshan,Xinjiang,LA-ICP-MS in situ U-Pb isotope analysis was conducted to study the geochronology of garnets around the ore body.A large number of layered garnet skarns in the deposit is consistent with the occurrence of ore bodies.According to the petrographic observation,garnets around the orebody can be divided into two types,i.e.,celadon(AQ4801)and brown(AQ4803).No obvious alteration characteristics were observed in the celadon garnet sample,while the cataclastic structure was developed in the brown garnet with metal sulfides filled in the intercrystalline fracture.The results of electron microprobe analysis(EPMA)show these garnets belong to the series of andradite-grossular(AQ4801 And 97 Gro_(2)~And 50 Gro_(48);AQ4803 And 96 Gro_(2)~And_(28) Gro_(70)).LA-ICP-MS in situ U-Pb dating shows that the samples of AQ4801 and AQ4803 have high U contents,i.e.,1.0×10^(-6)~32.2×10^(-6) and 5.4×10^(-6)~61.2×10^(-6),respectively.The weighted mean 206 Pb/238 U ages of sample AQ4801 and AQ4803 are(314.6±3.9)Ma(MSWD=1.15)and(323±15)Ma(MSWD=0.6),respectively,indicating that the Aqishan Pb-Zn deposit was formed between the late stage of Early Carboniferous and the early stage of Late Carboniferous(323~314.6 Ma).
作者
文斌
张元厚
杨万志
杜尚泽
王鹏
刘金伟
陈蕾
WEN Bin;ZHANG Yuan-hou;YANG Wan-zhi;DU Shang-ze;WANG Peng;LIU Jin-wei;CHEN Lei(College of Earth Sciences,Jilin University,Changchun 130061,China;Xinjiang Institute of Geological Survey,Urumqi 830000,China;MLR key laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resource,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《世界地质》
CAS
2021年第1期15-28,共14页
World Geology
基金
新疆地质勘查基金项目(Y14-5-LQ05)。
作者简介
通讯作者:张元厚(1963-),男,副教授,主要从事矿床学研究。E-mail:zyh4023@126.com。
