柿竹园多金属矿床成矿作用40Ar/39Ar年代学研究  

^(40)Ar/^(39)Ar dating of mineralization of Shizhuyuan polymetallic deposit

作　　者：王敏[1] 白秀娟[2] 云建兵[3] 赵令浩[4] 李岩林[5] 王周元[5] 蒲志平[1] 邱华宁[1] 

机构地区：[1]中国科学院广州地球化学研究所同位素地球化学国家重点实验室,广东广州510640 [2]中国地质大学(武汉)构造与油气资源教育部重点实验,湖北武汉430074 [3]大庆油田有限责任公司勘探事业部,黑龙江大庆163453 [4]国家地质实验测试中心,北京100037 [5]湖南柿竹园有色金属有限责任公司,湖南郴州423037

出　　处：《地球化学》2016年第1期41-51,共11页Geochimica

基　　金：国家重点基础研究发展计划项目(2012CB416706);国家自然科学基金创新群体项目(41421062);中国科学院“135规划”(GIGCAS-135-Y234151001)

摘　　要：石英是热液矿床的常见矿物,分布广泛。石英流体包裹体^(40)Ar/^(39)Ar定年技术为解决矿床年龄测定难题开辟了新的途径,但以前的研究工作缺少共生钾矿物年龄对比验证。本文选择柿竹园多金属矿床共生白云母和石英进行^(40)Ar/^(39)Ar测年分析对比研究。白云母激光阶段加热坪年龄为(153.7±0.9)Ma,代表了成矿年龄。采用真空击碎技术提取石英流体包裹体进行^(40)Ar/^(39)Ar年龄测定,获得了逐渐下降型年龄谱,在反等时线图上数据点构成高度线性相关的等时线,年龄为(152.3±5.7)Ma,代表了原生包裹体的年龄。石英原生流体包裹体等时线年龄与共生白云母年龄一致,表明石英流体包裹体^(40)Ar/^(39)Ar技术是行之有效的矿床定年方法。此外,K-Cl-40Ar图解可以区分石英中的原生、次生包裹体,并获得次生包裹体年龄为~100 Ma,与矿区钾长石脉年龄一致,指示了一次后期热液活动的时间。Quartz is a common mineral in hydrothermal deposits. 40Ar/39Ar dating technique for fluid inclusions in quartz by crushing in vacuo provides a new approach to dating mineralization of hydrothermal deposits. However, rare K-rich minerals are available for 40Ar/39Ar dating to confirm the validity of this new technique in previous studies. In this study the authors selected paragenetic quartz and muscovite in a piece of ore collected from the Shizhuyuan polymetallic deposit for 40Ar/39Ar dating. For the muscovite sample laser stepwise heating results in a very flat age spectrum with a plateau age of （153.7±0.9） Ma （1）. For the quartz sample crushing in vacuo yields an age spectrum marked with abnormal old apparent ages, which declines step-by-step for the first ten steps （steps 1 - 10）, and is followed by a plateau for the last ten steps （steps 11-20）. The data points for steps 11-20 constrain a well-defined isochron corresponding to an age of （152.3±5.7） Ma with an initial 40Ar/39Ar value of 291.7, which can be interpreted as the contributions from the primary fluid inclusions without excess 4~Ar inside. The isochron age for the primary fluid inclusions in quartz is well concordant with that of paragenetic muscovite, indicating that the quartz 40Ar/39Ar stepwise crushing technique is an effective method for obtaining ages of primary fluidinclusions in hydrothermal deposits. In addition, the primary and secondary fluid inclusions could be distinguished into two groups by plots based on correlations among the ratios of K, C1 and Ar. The ages of secondary fluid inclusions are obtained from these plots （-100 Ma）, which are concordant with the 40Ar/39Ar plateau age of the K-feldsoar vein. suestin a cost-hvdrothermal activity in formation of the ore deoosit.

关 键 词：40AR/39AR 流体包裹体 真空击碎技术 柿竹园 

分 类 号：P597[天文地球—地球化学]