Sulfur and lead isotope geochemistry of the Liushutang lead-zinc deposit in Hu'nan Province and its significance
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摘要:
对湖南省留书塘铅锌矿床不同阶段矿石硫化物进行的S、Pb同位素研究表明,17件矿石样品硫化物的S同位素组成变化范围较宽(δ34S=-12.8‰~4.6‰),具有地层有机硫(约-13‰)与岩浆硫(约5‰)混合特征。从早阶段到晚阶段,硫化物呈现出δ34S值逐渐升高、极差逐渐增大的演化趋势。最晚形成的重晶石矿石硫由地层硫酸盐提供。13件硫化物样品的Pb同位素组成比较稳定,206Pb/204Pb、207Pb/204Pb、208Pb/204Pb值变化范围分别为18.627~18.942、15.670~15.804和38.366~38.912,平均值分别为18.747、15.705和38.614。与区内新元古界—寒武系基底、邻区湘南与铅锌矿相关的岩浆岩钾长石Pb同位素进行的对比表明,矿石铅主要来源于矿区深部岩浆岩,少部分可能来自于基底寒武纪地层。结合宏观地质特征分析,留书塘矿床可能是与岩浆岩有关的热液充填交代矿床,其成矿物质具有多来源特征。
Abstract:The discovery of the Liushutang lead-zinc deposit is one of the major breakthroughs of prospecting in the Nanling metal-logenic belt in recent years.The lead-zinc lodes are strictly controlled by the shattered fracture zones along the western margin of Hengyang basin.Field observation shows that the related mineralization can be divided into three stages of quartz-pyrite, quartzsphalerite-galena and barite.In this paper, systematic research on S, Pb isotopes based on different stages of ores were conducted to explain the origin of ore-forming materials and ore genesis.The result shows that sulfur isotopes of 17 sulfide samples vary in a wide range (δ34S value being-12.8‰~4.6‰) with a dynamic evolution of gradual increasing of δ34S values from early to late.This can be probably explained by a mixing process of organic sulfur (~-13‰) and magmatic sulfur (~5‰).Sulfur of latest barite ore (δ34S is 14.7‰~24.4‰) might have been provided by the strata sulfate.206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb ratios of 13 sulfide ore samples vary in the range of 18.627~18.942, 15.670~15.804 and 38.366~38.912, with the average value being 18.747, 15.705 and 38.614, respec-tively.These values are very similar to values of Pb isotopes of magmatic feldspar in southern Hu'nan and also have weak linear rela-tion with Pb isotopes of regional Cambrian strata, suggesting that ore materials might have mainly originated from magmatic pluton in the depth, and subordinately from the Cambrian strata.Based on the above results and geological evidence, the authors put forward a model of magma-related hydrothermal mineralization with multiple sources of ore-forming materials, which may be suitable for explaining the ore genesis of the Liushutang deposit.
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Keywords:
- lead-zinc deposit /
- mineral paragenesis /
- S isotope /
- Pb isotope /
- Liushutang /
- Hu'nan Province
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致谢: 中国地质调查局武汉地质调查中心李华芹研究员、中国地质大学(武汉)凌文黎教授对本文修改提出了许多宝贵意见,武汉地质调查中心蔡应雄工程师在成文过程中提供了较多帮助,在此表示诚挚的感谢。
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图 1 衡阳盆地及周边地区地质矿产简图(据参考文献[19]修改)
1—不整合地质界线;2—整合地质界线;3—断裂;4—基底断裂或深大断裂;5—花岗质侵入体;6—铅锌矿;7—铜矿;8—铜铅锌矿。Pt3—新元古界;Z-S—震旦系-志留系;D-T2—泥盆系-中三叠统;K-N—白垩系-新近系。a—株洲-双牌深大断裂带;b—邵阳-郴州基底断裂带;c—醴陵-宁远深大断裂;d—常德-安仁基底断裂带
Figure 1. Geological map of Hengyang basin and adjacent areas showing distribution of mineral resources
图 2 湖南省留书塘铅锌矿床矿区地质略图(据参考文献②修改)
1—整合/不整合地质界线;2—断裂破碎带及编号;3—重晶石矿体;4—勘探线及见矿铅锌钻孔;5—见矿重晶石/未见矿钻孔。Q—第四系;K1s—白垩系神皇山组;C1m—石炭系孟公坳组;D3x—泥盆系锡矿山组;D2q—棋梓桥组;D2t—跳马涧组
Figure 2. Simplified geological map of the Liushutang lead-zinc deposit
图 6 留书塘矿床矿石矿物206Pb/204Pb-207Pb/204Pb(a)和206Pb/204Pb-208Pb/204Pb(b)图解(底图据参考文献[25])
A—地幔铅演化曲线;B—造山带铅演化曲线;C—上地壳铅演化曲线;D—下地壳铅演化曲线。1—矿石铅;2—奥陶系;3—寒武系;4—新元古界基底[23-24];5—湘南地区与铅锌矿相关的花岗岩钾长石[22]
Figure 6. 206Pb/204Pb-207Pb/204Pb (a) and 206Pb/204Pb-208Pb/204Pb (b) diagrams for sulfides from the Liushutang deposit
表 1 留书塘铅锌矿床主要原生矿物生成顺序
Table 1 The mineral paragenesis in the Liushutang Pb-Zn deposit
成岩成矿期成矿阶段 热液期 石英-黄铁矿阶段 石英-闪锌矿-方铅矿阶段 重晶石阶段 石英 黄铁矿 黄铜矿 矿物名称 磁黄铁矿 闪锌矿 方铅矿 斑铜矿 辉银矿 重晶石 方解石 注:线条粗、细分别代表形成矿物的多、少;线条的长、短代表延续时间的长、短 表 2 留书塘矿床代表性矿石矿物S同位素组成
Table 2 S isotopic compositions of typical sulfides from the Liushutang deposit
样品号 采样位置 成矿阶段 测试矿物 δ34SCDT/% 12D128-1 四中段 2-2 闪锌矿 -7.5 12D128-2 四中段 2-1 闪锌矿 -8.1 四中段 黄铁矿 -10.8 12D128-3 四中段 2-2 闪锌矿 -4.5 12D128-4 四中段 2-1 闪锌矿 -5.0 12D128-5 四中段 2-1 闪锌矿 -10.0 12D129-1 五中段 3 重晶石 19.4 12D129-4 五中段 2-2 闪锌矿 4.6 12D130-2 六中段 1 黄铁矿 -12.8 12D130-3 六中段 1 黄铁矿 -12.0 12D130-4 六中段 2-1 闪锌矿 -3.8 12D130-5 六中段 3 重晶石 14.7 12D131-1 十三中段 2-1 方铅矿 -7.6 12D131-2 十三中段 2-1 闪锌矿 -5.4 12D131-3 十三中段 2-2 闪锌矿 4.1 方铅矿 -2.5 12D131-4 十三中段 2-1 闪锌矿 -7.1 方铅矿 -10.2 12D131-5 十三中段 1 黄铜矿 -9.3 12D131-6 十三中段 1 黄铁矿 -10.7 12D131-7 十三中段 1 黄铜矿 -9.9 12D131-8 十三中段 3 重晶石 24.4 注:1代表石英-黄铁矿阶段;2-1代表石英-闪锌矿-方铅矿阶段稍早形成的细粒铅锌矿石;2-2代表同阶段稍晚形成的粗粒矿石;3代表重晶石阶段 表 3 留书塘矿床代表性矿石矿物Pb同位素组成
Table 3 Pb isotopic compositions of typical sulfides from the Liushutang deposit
样品号 成矿阶段/地层/岩体 测试矿物/岩性 206Pb/204Pb 2σ 207Pb/204Pb 2σ 208Pb/204Pb 2σ 资料来源 12D128-2 2-1 闪锌矿 18.627 0.003 15.685 0.003 38.655 0.007 12D128-3 2-2 闪锌矿 18.719 0.002 15.677 0.002 38.519 0.004 12D128-5 2-1 闪锌矿 18.727 0.002 15.720 0.001 38.706 0.004 12D129-1 3 重晶石 18.629 0.002 15.681 0.002 38.630 0.005 12D129-4 2-2 闪锌矿 18.825 0.002 15.670 0.001 38.414 0.004 12D130-2 1 黄铁矿 18.709 0.002 15.703 0.001 38.650 0.004 12D130-3 1 黄铁矿 18.628 0.002 15.682 0.001 38.646 0.004 本文 12D130-5 3 重晶石 18.743 0.022 15.743 0.016 38.747 0.046 12D131-3 2-2 方铅矿 18.705 0.002 15.693 0.002 38.564 0.005 12D131-4 2-1 方铅矿 18.893 0.001 15.680 0.002 38.366 0.002 12D131-5 1 黄铜矿 18.942 0.002 15.711 0.002 38.484 0.006 12D131-6 1 黄铁矿 18.858 0.002 15.804 0.002 38.912 0.005 12D131-8 3 重晶石 18.708 0.002 15.716 0.002 38.683 0.005 14D04 奥陶系 板岩 19.031 0.004 15.708 0.004 40.639 0.008 本文 14D05 粉砂岩 18.911 0.002 15.781 0.002 39.670 0.006 14D08 粉砂岩 18.898 0.003 15.659 0.003 38.478 0.007 14D09 寒武系 板岩 21.106 0.003 15.895 0.002 38.959 0.005 本文 14D10 粉砂岩 19.347 0.004 15.697 0.004 38.778 0.010 14D11 粉砂质板岩 18.651 0.003 15.695 0.001 39.487 0.005 14D12 板岩 18.721 0.003 15.695 0.003 39.609 0.006 14D13 奥陶系 板岩 19.156 0.003 15.724 0.002 40.026 0.005 本文 14D15 板岩 18.811 0.003 15.702 0.002 39.392 0.005 14D16 板岩 18.907 0.004 15.690 0.003 40.059 0.008 309-12 钾长石 18.519 15.589 38.454 273-53 黄沙坪 钾长石 18.622 15.600 38.572 [17] 273-23 钾长石 18.657 15.675 38.438 273-19 钾长石 19.305 15.905 38.807 D137-1 铜山岭 钾长石 18.704 15.721 38.943 [17] D139-1 钾长石 18.805 15.726 38.987 水83-7 水口山 钾长石 18.400 15.630 38.484 [17] 水83-12 钾长石 18.534 15.682 38.583 注:成矿阶段1、2-1、2-2、3含义同表 2 -
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