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首页> 外文学位 >Rhenium-osmium geochronology of low-level sulfide minerals from hydrothermal ore deposits---Applications, limitations, and implications.
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Rhenium-osmium geochronology of low-level sulfide minerals from hydrothermal ore deposits---Applications, limitations, and implications.

机译：热液矿床中低含量硫化物的hen- geo年代学-应用，局限和意义。

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摘要

Rhenium-osmium geochronology of common sulfide minerals is a technique that offers a theoretical means of directly dating many hydrothermal ore deposits in Earth's crust. In practice, however, the successful application of this technique has historically been impeded by major analytical challenges. This PhD thesis utilizes recent analytical developments that, for the first time, permit precise and accurate isotopic measurements of the low concentrations of rhenium and osmium typical of most crustal sulfide minerals. The objective of this study is to further develop this technique for mainstream application, and to assess the strengths and limitations of the technique with different sulfide minerals. To accomplish this, measurement of rhenium-osmium isotopic compositions have been performed for common sulfide minerals, including arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite, and gersdorffite, from multiple gold and base metal deposits in worldclass ore districts globally, and through geologic time. By comparison of determined rhenium-osmium results to existing geochronologic constraints for the deposits, and considering the thermal histories of the host terranes, a more comprehensive understanding of the utility of this technique has been achieved. The results of this study indicate that, using proper sampling, analytical, and data reduction protocols, both arsenopyrite and pyrite are very reliable chronometers of ore-forming hydrothermal events. Demonstrably accurate and relatively precise (better than 1.5%) rhenium-osmium mineralization ages have been determined for important orogenic gold deposits using arsenopyrite (Homestake, South Dakota; Muruntau, Uzbekistan) and for orogenic gold (Con, Northwest Territories) and volcanogenic massive sulfide (Trout Lake and Sherritt Gordon, Manitoba) deposits using pyrite. For these minerals, apparent minimum closure temperatures of 400°C for arsenopyrite and possibly as high as 675°C for pyrite can be inferred. Both the rhenium-osmium mineralization ages and initial Os isotopic compositions of these sulfides can be used to provide crucial petrogenetic information regarding ore genesis. In contrast, spurious rhenium-osmium results from coexisting pyrrhotite and sphalerite demonstrate that these minerals are readily disturbed during low temperature, post-crystallization thermal events, and are poor choices for rhenium-osmium geochronology. Results for chalcopyrite from the Konuto Lake volcanogenic massive sulfide deposit, Saskatchewan, are less conclusive, but suggest that chalcopyrite rhenium-osmium isotopic compositions may be reset at metamorphic temperatures of less than mu∼500°C.
机译：普通硫化矿物的-geo年代学是一种技术，提供了直接对地壳中许多热液矿床进行测年的理论方法。然而，实际上，该技术的成功应用历来受到重大分析挑战的阻碍。本博士学位论文利用了最近的分析开发成果，这首次使大多数地壳硫化物矿物典型的低浓度of和的同位素测量成为可能。这项研究的目的是进一步开发该技术以用于主流应用，并评估该技术在不同硫化物矿物中的优势和局限性。为此，已经对全球范围内世界一流矿区的多种金矿和贱金属矿床中常见的硫化物矿物（包括毒砂，黄铁矿，黄铁矿，黄铜矿，闪锌矿和闪锌矿）的of--同位素组成进行了测量。 。通过将确定的rh- results结果与该矿床的现有地质年代学限制条件进行比较，并考虑宿主地层的热历史，已经对该技术的实用性有了更全面的了解。这项研究的结果表明，使用适当的采样，分析和数据减少方案，毒砂和黄铁矿都是形成矿石热液事件的非常可靠的计时器。已确定了重要的造山金矿床中使用毒砂（南达科他州霍姆斯特克；乌兹别克斯坦的穆勒陶）和造山金矿（康州，西北地区）和火山成块的硫化物的accurate- mineral矿化年龄具有明显的准确性和相对精确的（优于1.5％）。 （鳟鱼湖和马尼托巴省的Sherritt Gordon）使用黄铁矿进行沉积。对于这些矿物，可以推断出毒砂的最低最低封闭温度为400°C，黄铁矿的最高封闭温度可能高达675°C。这些硫化物的-mineral矿化年龄和初始Os同位素组成均可用于提供有关矿石成因的重要岩石成因信息。相反，共存的黄铁矿和闪锌矿的伪rh--结果表明，这些矿物在低温，结晶后的热事件中容易受到干扰，对于and- geo年代学来说是较差的选择。从库努托湖火山成矿的大规模硫化物矿床萨斯喀彻温省获得的黄铜矿的结论尚不那么确定，但表明黄铜矿的-iso同位素组成可能会在低于500℃的变质温度下重置。

著录项

  • 作者

    Morelli, Ryan Michael.;

  • 作者单位

    University of Alberta (Canada).;

  • 授予单位 University of Alberta (Canada).;
  • 学科 Geology.;Geochemistry.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 208 p.
  • 总页数 208
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;地质学;
  • 关键词

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