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首页> 外文期刊>Contributions to Mineralogy and Petrology >Diversity of primary CL textures in quartz from porphyry environments: implication for origin of quartz eyes
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Diversity of primary CL textures in quartz from porphyry environments: implication for origin of quartz eyes

机译：斑岩环境中石英的主要CL纹理的多样性：对石英眼起源的暗示

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摘要

Porphyry-style mineralization is related to the intrusion and crystallization of small stocks, which can be of different compositions (from intermediate to felsic) and can intrude into different host rocks (from magmatic to sedimentary). We used cathodoluminescence and electron probe microanalysis to study the internal textures of more than 300 quartz eyes from six porphyry deposits, Panguna (Papua New Guinea), Far Southeast porphyry (Philippines), Batu Hijau (Indonesia), Antapaccay (Peru), Rio Blanco (Chile) and Climax (USA). Significant diversity of the internal textures in quartz eyes was revealed, sometimes even within a single sample. Quartz grains with Ti-rich cores surrounded by Ti-poor mantles were found next to the grains showing the opposite Ti distribution or only slight Ti fluctuations.We propose that diversity of the internal patterns in quartz eyes can actually reflect in situ crystallization history, and that prolonged crystallization after magma emplacement under conditions of continuous cooling can account for the observed features of internal textures. Formation of quartz eyes begins at high temperatures with crystallization of high titanium Quartz 1, which as the melt becomes more and more evolved and cooler, is overgrown by low Ti Quartz 2. Subsequent fluid exsolution brings about dramatic change in the melt composition: OH − , alkalis and other Cl-complexed elements partition into the fluid phase, whereas Ti stays in the melt, contributing to a rapid increase in Ti activity. Separation of the fluid and its further cooling causes disequilibrium in the system, and the Quartz 2 becomes partially resorbed. Exsolution of the fluid gradually builds up the pressure until it exceeds the yield strength of the host rocks and they then fracture. This pressure release most likely triggers crystallization of Quartz 3, which is higher in Ti than Quartz 2 because Ti activity in the melt is higher and pressure of crystallization is lower. As a result of the reaction between the exsolved fluid and quartz a new phase, a so called ‘heavy fluid’ forms. From this phase Quartz 4 crystallizes. This phase has extremely high metal-carrying capacity, and may give a rise to mineralizing fluids. Finally, on the brink of the subsolidus stage, groundmass quartz crystallizes. Prolonged crystallization under conditions of continuous cooling accounts better for the diversity of CL textures than crystallization in different parts of a deep magma chamber. It is also in a better agreement with the existing model for formation of porphyry-style deposits.
机译：斑岩型矿化与小储量的侵入和结晶有关，小储量的成分可能不同（从中间到长英质），并且可以侵入到不同的宿主岩中（从岩浆到沉积）。我们使用阴极发光和电子探针显微分析研究了六种斑岩矿床中300多个石英眼的内部纹理，这些斑岩矿床分别为：Panguna（巴布亚新几内亚），远东南斑岩（菲律宾），Batu Hijau（印度尼西亚），Antapaccay（秘鲁），Rio Blanco （智利）和Climax（美国）。揭示了石英眼内部纹理的显着多样性，有时甚至在一个样本中也是如此。在具有相反的Ti分布或仅有微小的Ti波动的晶粒旁边发现了具有富含Ti核的石英晶粒，而这些晶粒显示出相反的Ti分布或仅有微小的Ti波动。认为在连续冷却条件下岩浆侵入后结晶时间延长可以解释内部纹理的观察特征。石英眼的形成始于高温下的高钛石英1的结晶，随着熔体的发展和冷却，钛钛2的含量过低。随后的流体析出导致熔体成分发生巨大变化：OH- ，碱和其他与Cl络合的元素分配到液相中，而Ti留在熔体中，有助于Ti活性的快速增加。流体的分离及其进一步的冷却导致系统中的不平衡，并且Quartz 2被部分吸收。流体的溶解逐渐建立压力，直到压力超过基岩的屈服强度，然后它们破裂。这种压力释放最有可能触发Quartz 3的结晶，由于其在熔体中的Ti活性较高且结晶压力较低，因此Ti的结晶度要比Quartz 2高。由于溶解的液体和石英之间发生了反应，形成了一个新相，即所谓的“重质流体”。从这个阶段开始，石英4结晶。该相具有极高的载金属能力，并且可能引起矿化液的增加。最后，在次固相阶段的边缘，地质石英结晶。与在深部岩浆室不同部位的结晶相比，在连续冷却条件下延长的结晶更好地解释了CL的多样性。它也与斑岩型矿床形成的现有模型更好地吻合。

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  • 来源
    《Contributions to Mineralogy and Petrology》 |2013年第4期|1253-1268|共16页
  • 作者

    O. V. Vasyukova; V. S. Kamenetsky; K. Goemann; P. Davidson;

  • 作者单位

    ARC Centre of Excellence in Ore Deposits and School of Earth Sciences University of Tasmania">(1);

    Earth and Planetary Sciences McGill University">(3);

    ARC Centre of Excellence in Ore Deposits and School of Earth Sciences University of Tasmania">(1);

    Central Science Laboratory University of Tasmania">(2);

    ARC Centre of Excellence in Ore Deposits and School of Earth Sciences University of Tasmania">(1);

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    Cathodoluminescence; Quartz eyes; Porphyry deposits;

    机译：阴极发光;石英眼;斑岩矿床;

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