投稿时间：2014-05-31
修订日期：2015-07-02
网络发布日期：2015-09-02
中文摘要:沽源-红山子铀成矿带河北沽源张麻井铀-钼矿床赋存在张家口组第三段流纹岩与流纹斑岩、石英斑岩的接触带附近,主要受隐爆角砾岩控制。研究表明,张麻井铀-钼矿床赋矿流纹岩、流纹斑岩和石英斑岩的锆石具有清晰的环带结构,Th/U比值高,属典型的岩浆成因锆石。SHRIMP锆石U-Pb测年结果显示,流纹岩12颗锆石的206Pb/238U 年龄变化范围为136~144 Ma,加权平均年龄为(138.6±1.4) Ma(MSWD=2.4);流纹斑岩11颗锆石的206Pb/238U年龄变化范围为136~145 Ma,加权平均年龄为(140.2±1.6) Ma(MSWD=2.2);石英斑岩11颗锆石的206Pb/238U年龄变化范围为132~147 Ma,加权平均年龄为(136.2±2.9) Ma(MSWD=1.8)。由此可见,流纹岩、流纹斑岩和石英斑岩的同位素年龄在误差范围内一致,指示火山喷发和斑岩就位发生在早白垩世早期,与滨西太平洋成矿域以火山岩为赋矿主岩的热液型铀矿的围岩形成时代一致,沽源-红山子铀成矿带早白垩世早期次火山岩与同期火山岩的接触带附近是寻找铀矿的有利空间。
Abstract:The Zhangmajing U-Mo deposit located near the third member of Zhangjiakou Formation where the rhyolite is in contact with rhyolite porphyry and quartz porphyry, mainly controlled by the cryptoexplosive breccias in the Guyuan-Hongshanzi uranium metallogenic belt in Guyuan, Hebei Province. The zircons in the rhyolite, rhyolite porphyry and quartz porphyry from the country rock of the Zhangmajing U-Mo deposit have clear zonal structure and high Th/U ratio, suggesting typical magmatic zircons. The results of the SHRIMP zircon U-Pb dating indicate that the 206Pb/238U ages of analytical points of twelve zircons from rhyolite vary in the range of 136~144 Ma with the weighted average of (138.6±1.4) Ma and MSWD of 1.4, those of analytical points of eleven zircons from rhyolite porphyry vary in the range of 136~145 Ma with the weighted average of (140.2±1.6) Ma and MSWD of 2.2, and those of analytical points of eleven zircons from quartz porphyry vary in the range of 132~147 Ma with the weighted average of (136.2±2.9) Ma and MSWD of 1.8. Therefore, within the error range the age range of the rhyolite is in accordance with that of rhyolite porphyry and quartz porphyry, implying that the volcanic eruption and porphyry generation took place in early Early Cretaceous, in accord with the wall rocks of hydrothermal-type uranium deposits of the west Pacific metallogenic domain in age, with volcanic rocks as the ore-bearing host rocks. It is thus held that the area near the contact zone between early Early Cretaceous subvolcanic rock and synchronous volcanic rock is the favorable place in search for uranium deposits in the Guyuan-Hongshanzi uranium metallogenic belt.
keywords:geochemistry rhyolite rhyolite porphyry quartz porphyry SHRIMP zircon U-Pb age geological significance Zhangmajing U-Mo deposit
文章编号：
中图分类号：P618.65;P619.14
文献标志码：
基金项目:本文得到国家自然科学基金项目《沽源-红山子铀成矿带流纹岩-粗面岩组合的成因及其与铀成矿的关系》(批准号: 41372071)和中国核工业总公司项目《中国中-新生代铀成矿作用研究》(批准号:中核地计[2008]74号)联合资助
引用文本：
巫建华,丁辉,牛子良,吴仁贵,祝民强,郭国林,刘帅,余达淦.2015.河北沽源张麻井铀-钼矿床围岩SHRIMP锆石U-Pb定年及其地质意义[J].矿床地质,34(4):757~768WU JianHua,DING Hui,NIU ZiLiang,WU RenGui,ZHU MinQiang,GUO GuoLin,LIU Shuai,YU DaGan.2015.SHRIMP zircon U-Pb dating of country rock in Zhangmajing U-Mo deposit in Guyuan, Hebei Province, and its geological significance[J].Mineral Deposits34(4):757~768
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