| 阳山金矿床锶铅同位素组成特征与成矿物质来源 |
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| 引用本文： | 张莉,杨荣生,毛世东,鲁颖淮,秦艳,刘红杰.阳山金矿床锶铅同位素组成特征与成矿物质来源[J].岩石学报,2009,25(11):2811-2822. |
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| 作者姓名： | 张莉 杨荣生 毛世东 鲁颖淮 秦艳 刘红杰 |
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| 作者单位： | 1. 中国科学院广州地球化学研究所成矿动力学重点实验室,广州,510640
2. 北京大学造山带与地壳演化实验室,北京,100871 |
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| 基金项目： | 国家973计划2006CB403500项目;NSFC项目，国家危机矿山项目20089934号以及武警黄金部队科研项目的资助 |
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| 摘 要： | 甘肃阳山金矿位于西秦岭造山带的陕甘川"金三角"地区,是我国最大的卡林型-类卡林型金矿床.本文研究了该矿床赋矿地层、岩浆岩、矿石以及碧口地体碧口群岩石的锶和铅同位素组成特征,获得成矿时的矿石硫化物、赋矿地层三河口群、中生代花岗斑岩、前寒武纪碧口群的锶同位素初始比值I_(Sr)范围分别是0.70798～0.71697,0.71382～0.72005,0.70918～0.71168,0.70344～0.71009.这些结果表明,初始成矿流体Isr值应低于赋矿地层、中生代花岗岩,可能主要由碧口地体变质脱水形成.成矿流体在上升过程中与高ISr值的赋矿地层三河口群发生水岩作用,流体I_(Sr)值增高;高I_(Sr)值的成矿流体与赋矿花岗斑岩脉再次发生水岩作用时,导致部分硫化物I_(Sr)值高于花岗斑岩I_(Sr)值.矿石硫化物~(206)Pb/~(204) Pb、~(207) Pb/~(204) Pb和~(204) Pb/~(204)Pb比值分别为17.552～18.759、15.576～15.928和37.894～39.293,变化范围大于赋矿地层三河口群和花岗斑岩,而与碧口群基本一致,反映了硫化物铅同位素组成主要继承了碧口群的特征,同样指示部分成矿物质来自碧口群.总之,碧口群是不可缺少的成矿流体和物质的来源之一,含碧口群的碧口地体在中生代沿勉略缝合带向北陆内俯冲到阳山矿田之下,在阳山矿田之下发生变质脱水作用,流体上升为成矿系统提供流体、成矿元素和热量.
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| 关 键 词： | 类卡林型金矿床 成矿物质来源 Sr-Pb同位素组成 勉略缝合带 秦岭造山带 阳山金矿 |
Sr and Pb isotopic feature and ore-forming material source of the Yangshan gold deposit |
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| ZHANG Li,YANG RongSheng,MAO ShiDong,LU YingHuai,QI Yan,LIU HongJie.Sr and Pb isotopic feature and ore-forming material source of the Yangshan gold deposit[J].Acta Petrologica Sinica,2009,25(11):2811-2822. |
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| Authors: | ZHANG Li YANG RongSheng MAO ShiDong LU YingHuai QI Yan LIU HongJie |
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| Abstract: | The Yangshan gold deposit,located in the western Qinling Orogen,is the largest Carlin-likc or Carlin gold deposit in China.Given that the ores resulted from interaction between host-rocks and ore-fluids,this paper reports Sr and Pb isotopic composition of ore-hosting strata,magmatites and ores as well as the Bikou Group of the Bikou terrane to constrain sources of ore-forming material and fluid.ISr ratios of sulfides,ore-hosting Sanhekou Group,Mesozoic granite porphyry and the Bikou Group are 0.70798～0.71697,0.71382～0.72005,0.70918～0.71168 and 0.70344～0.71009,respectively.This indicates that the initial ore-fluids should have lsr ratios lower than those of sulfides,ore-hosting Sanhekou Group and Mesozoic granite porphyry,and must be originated from metamorphic devolatilization of the Bikou Group.The ore-fluid increased its I_(Sr)values during its upward migration due to the interaction with high-I_(Sr)ore-hosting strata.This causes higher I_(Sr)values of most sulfides than those of the Mesozoic granite porphyry.Sulfides yield wider variation ranges of ~(205)Pb/~(204)pb,~(207)pb/~(204)Pb and ~(208)Pb/~(204)Pb ratios(17.552～18.759,15.576～15.928 and 37.894～39.293,respectively)than those of both the ore-hosting strata and granite porphyry,but similar to those of the Bikou Group.This suggests that the Pb-isotope signatures of sulfides are mainly inherited from the Bikou Group and the ore-forming elements were partly originated from the Bikou Group.Hence,it is reasonable to suggest the Bikou Group as an indispensable source to provide ore-forming elements and fluids for the Yangshan giant gold system.In Mesozoic,the Bikou Group was northwardly underthrust along the Mian-Lue suture,metamorphosed and devolatilized beneath the Yangshan ore-field and,thereby the ore-fluid were generated and migrated upwards,providing ore-metals,fluids and heat for the Yangshan gold-mineralizing system. |
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| Keywords: | Carlin-like type gold deposit Ore-foming material source Sr-Pb isotopic composition Mian-Lue geosuture Qialing collisional orogen Yangshan gold deposit |
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