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首页> 外文学位 >Geochemistry of volcanogenic massive sulfide and high-grade gold granite-hosted ore deposits, southern Alaska, and, development and application of laser microprobe techniques for analysis of sulfur, carbon and oxygen isotope ratios.
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Geochemistry of volcanogenic massive sulfide and high-grade gold granite-hosted ore deposits, southern Alaska, and, development and application of laser microprobe techniques for analysis of sulfur, carbon and oxygen isotope ratios.

机译：阿拉斯加南部火山成块状硫化物和高级金花岗岩砂岩矿床的地球化学，以及用于分析硫，碳和氧同位素比的激光微探针技术的开发和应用。

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摘要

The Prince William Sound district, located in southcentral Alaska, contains innumerable seafloor volcanogenic massive sulfide deposits hosted within volcanic and sedimentary rock sequences of the Late Cretaceous Valdez Group and the Paleocene to Eocene Orca Group accretionary complexes of southern Alaska. Detailed petrologic, whole-rock, stable isotope and fluid inclusion studies indicate that these massive sulfide bodies formed in mid-ocean ridge hydrothermal environments, and are not later epigenetic features related to accretion of the Orca and Valdez Groups to southern Alaska. Geochemical variations, particularly variations in stable isotope and fluid inclusion minimum trapping temperatures, distinguish volcanic rock-hosted deposits (low {dollar}deltasp{lcub}34{rcub}{dollar}S and {dollar}deltasp{lcub}18{rcub}{dollar}O values) from sediment-hosted deposits (elevated {dollar}deltasp{lcub}34{rcub}{dollar}S and {dollar}deltasp{lcub}18{rcub}{dollar}O values).; The Estelle pluton, located in the central Alaska Range, contains high-grade Au mineralization related to late-magmatic stage boiling of high-salinity fluids. Detailed petrographic and fluid inclusion studies reveal very high-salinity fluids spatially associated with concentrically banded, spherical to ellipsoidal mineralized structures. The origin of these structures is problematic, as they resemble "bubbles" related to hyper-solidus processes (such as immiscibility), yet occur in linear zones that crosscut the host pluton, suggesting subsolidus structural control. Our data are consistent with formation of a late magmatic stage hydrothermal fluid that underwent phase separation, producing an Au-bearing high-salinity phase and a lower-salinity unmineralized phase.; The development of the laser microprobe is critical to the study of micro-scale stable isotope variations commonly encountered in ore forming environments. The University of Wisconsin laser microprobe provides high spatial resolution (to 70 {dollar}mu{dollar}m) with analytical precision of {dollar}pm{dollar}0.14 {dollar}perthous{dollar} for measurement of {dollar}deltasp{lcub}34{rcub}{dollar}S in pyrite, pyrrhotite, galena, chalcopyrite and sphalerite. Accuracy is good; corrections of {dollar}-{dollar}0.1 to +1.4 {dollar}perthous{dollar} are required to correct for mineral specific fractionation related to the process of laser ablation. Analysis of {dollar}deltasp{lcub}18{rcub}{dollar}O and {dollar}deltasp{lcub}13{rcub}{dollar}C in calcite and dolomite shows promise. Precision is not as good as for sulfides, and mineral specific fractionations are not yet determined, but appear to be necessary.
机译：位于阿拉斯加中南部的威廉王子湾地区包含无数的海底火山成因块状硫化物矿床，这些矿床存在于晚白垩纪瓦尔迪兹组和古新世至始新世的逆戟鲸群在阿拉斯加南部的增生复合物中。详细的岩石学，全岩石，稳定同位素和流体包裹体研究表明，这些块状硫化物体形成于大洋中脊热液环境中，并且与Orca和Valdez群在阿拉斯加南部的增生无关。地球化学变化，特别是稳定同位素和流体包裹体最低俘获温度的变化，区分了火山岩型沉积物（低{dollar} deltasp {lcub} 34 {rcub} {dollar} S和{dollar} deltasp {lcub} 18 {rcub}来自沉积物的沉积物（高的{dollar} deltasp {lcub} 34 {rcub} {dollar} S和{dollar} deltasp {lcub} 18 {rcub} {dollar} O值的{dollar} O值）。位于阿拉斯加山脉中部的Estelle岩体含有与高盐度流体的岩浆后期沸腾有关的高级金矿化作用。详细的岩石学和流体包裹体研究显示，高盐度流体在空间上与同心带状，球形到椭圆形的矿化结构有关。这些结构的起源是有问题的，因为它们类似于与超固相过程（如不混溶性）有关的“气泡”，但发生在横切宿主胶体的线性区域中，表明亚固相结构控制。我们的数据与岩浆晚期热液的形成相一致，后者经历了相分离，产生了一个含金的高盐度相和一个较低盐度的非矿化相。激光微探针的发展对于研究成矿环境中常见的微观尺度稳定同位素变化至关重要。威斯康星大学的激光微探针提供了高的空间分辨率（高达70 {μm}μm{μm} m），分析精度为{μm}μm{$μm} l {4}美元，用于测量{μm}的三角洲{lcub} } 34 {rcub} {dollar} S在黄铁矿，黄铁矿，方铅矿，黄铜矿和闪锌矿中。准确性好；需要校正{dollar}-{dollar} 0.1至+1.4 {dollar} perthous {dollar}，以校正与激光烧蚀过程有关的矿物比分馏。对方解石和白云石中的{dol} deltasp {lcub} 18 {rcub} {dollar} O和{dollar} deltasp {lcub} 13 {rcub} {dollar} C的分析显示了前景。精度不如硫化物好，并且尚未确定矿物比分馏，但似乎是必需的。

著录项

  • 作者

    Crowe, Douglas Edward.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Geochemistry.; Geology.
  • 学位 Ph.D.
  • 年度 1990
  • 页码 238 p.
  • 总页数 238
  • 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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