豫西熊耳山五丈山岩体锆石U-Pb定年及其地质意义
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摘要
五丈山岩体与熊耳山地区的金钼成矿关系密切,精确限定五丈山岩体的年龄对探讨其成矿背景有重要意义。6件锆石样品均取自五丈山钾长或二长花岗岩,每件样品的20个测点中均有14~17个测定值位于或接近~(207)Pb/~(235) U-~(206)Pb/~(238)U一致线。6件样品的U-Pb年龄值十分接近,分别为177.3 Ma±1.4 Ma,177.4 Ma±1.7 Ma,177.3 Ma±1.6Ma,177.4Ma±1.9Ma,177.5Ma±1.5Ma和177.2Ma±1.7Ma,样品测试精度高;Th/U值介于0.221~1.108之间,平均为0.588。确定五丈山岩体的侵位年龄为177.2Ma~177.5 Ma,对解释燕山早期的矿床成因、扩大找矿范围有重要意义。
Gold and Molybdenum mineralization in Xiong′ershan area is closely related to Wuzhangshan rock mass.Therefore,precisely defined the age of Wuzhangshan rock mass is important in the understanding of metallogenic background in the area.Six samples with magmatic zircons are collected from moyite and adamellite of Wuzahngshan rock mass.It shows that there are 14~17 measured values of each sample with 20 measuring points at or near the ~(207)Pb/~(235) U-~(206)Pb/~(238) U consistent line.The U-Pb dating ages of the 6samples are very close,they are 177.3Ma±1.4 Ma,177.4 Ma±1.7 Ma,177.3 Ma±1.6 Ma,177.4 Ma±1.9 Ma,177.5 Ma±1.5 Ma and 177.2 Ma±1.7 Ma respectively,with high test precision.Th/U ratio ranges from 0.221to1.108 with average value of 0.588.The study reveals that the emplacement age of Wuzhangshan rock mass is 177.2Ma~177.5Ma,and the age determination is of great significance in the explanation of the ore deposit origin in Early Yanshan Periods and is helpful in the future gold prospecting.
Gold and Molybdenum mineralization in Xiong′ershan area is closely related to Wuzhangshan rock mass.Therefore,precisely defined the age of Wuzhangshan rock mass is important in the understanding of metallogenic background in the area.Six samples with magmatic zircons are collected from moyite and adamellite of Wuzahngshan rock mass.It shows that there are 14~17 measured values of each sample with 20 measuring points at or near the ~(207)Pb/~(235) U-~(206)Pb/~(238) U consistent line.The U-Pb dating ages of the 6samples are very close,they are 177.3Ma±1.4 Ma,177.4 Ma±1.7 Ma,177.3 Ma±1.6 Ma,177.4 Ma±1.9 Ma,177.5 Ma±1.5 Ma and 177.2 Ma±1.7 Ma respectively,with high test precision.Th/U ratio ranges from 0.221to1.108 with average value of 0.588.The study reveals that the emplacement age of Wuzhangshan rock mass is 177.2Ma~177.5Ma,and the age determination is of great significance in the explanation of the ore deposit origin in Early Yanshan Periods and is helpful in the future gold prospecting.
引文
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[3]李永峰.豫西熊耳山地区中生代花岗岩类时空演化与钼(金)成矿作用[D].北京:中国地质大学,2005.
[4]Han Y G.Evolution of the Mesozoic Granites in the Xiong′ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications[J].Acta Geologica Sinica(English Edition),2007,(02):253-265.
[5]赖相濡.熊耳山-外方山地区中生代花岗质岩石对金成矿作用的约束[D].北京:中国地质大学,2015.
[6]Liu Y,Hu Z,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chemical Geology,2008,(257):34-43.
[7]Andersen T.Correction of common lead in U-Pb analyses that do not report 204Pb[J].Chemical Geology,2002,(192):59-79.
[8]Ludwig K R.Isoplot-A plotting and regression program for radiogenic-isotope data[J].U.S Geological Survey Open-File Report,1991,(39):91-445.
[9]王建其,朱赖民,郭波,等.华北陆块南缘华山、老牛山及合峪花岗岩体Sr-Nd,Pb同位素组成特征及其地质意义[J].矿物岩石,2015,(01):63-72.
[10]Vavra G,Schmid D.Internal morphology,habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons geochronology of the Ivrea Zone(Southern Alps)[J].Contrib Mineral Petrol,1999,(134):380-404.
[11]岳紫龙,杜杨松,曹毅,等.铜陵桂花冲花岗闪长斑岩地球化学特征、锆石U-Pb年龄及其地质意义[J].矿物岩石,2015,(01):82-90.
[12]陈文,万渝生,李华芹,等.同位素地质年龄测定技术及应用[J].地质学报,2011,(11):1 917-1 947.
[13]王卫星,邓军,龚庆杰,等.豫西熊耳山五丈山、花山、合峪花岗岩体与金成矿关系[J].黄金,2010,(04):12-17.
[14]邵克忠,栾文楼.Bi-硫盐、Bi-碲化物-祁雨沟爆发-坍塌角砾岩型金矿床成因及找矿标志[J].河北地质学院学报,1989,(03):299-305.
[15]毛景文,谢桂青,张作衡,等.中国北方中生代大规模成矿作用的期次及其地球动力学背景[J].岩石学报,2005,(01):171-190.
[16]孟芳,毛景文,叶会寿,等.豫西老君山花岗岩体SHRIMP锆石U-Pb年龄及其地球化学特征[J].中国地质,2012,(06):1 501-1 524.
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