• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Contributions to Mineralogy and Petrology >Redox processes in subducting oceanic crust recorded by sulfide-bearing high-pressure rocks and veins (SW Tianshan, China)
【24h】

Redox processes in subducting oceanic crust recorded by sulfide-bearing high-pressure rocks and veins (SW Tianshan, China)

机译：含硫化物的高压岩石和脉动记录的俯冲洋壳的氧化还原过程（中国西南天山）

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The oxidized nature of the sub-arc mantle and hence arc magmas is generally interpreted as a result of the migration of subduction-related oxidizing fluids or melts from the descending slab into the mantle wedge. This is of particular importance seeing that the oxidization state of sub-arc magmas seems to play a key role in the formations of arc-related ore deposits. However, direct constraints on the redox state of subducted oceanic crust are sparse. Here, we provide a detailed petrological investigation on sulfide-and oxide-bearing eclogites, blueschists, micaschists, eclogite-facies and retrograde veins from the Akeyazi high-pressure (HP) terrane (NW China) in order to gain insight into the redox processes recorded in a subducting oceanic slab. Sulfides in these rocks are mainly pyrite and minor pyrrhotite, chalcopyrite, bornite, molybdenite, sphalerite and chalcocite, including exsolution textures of bornite-chalcopyrite intergrowth. Magnetite, ilmenite and pyrite occur as inclusions in garnet, whereas sulfides are dominant in the matrix. Large pyrite grains in the matrix contain inclusions of garnet, omphacite and other HP index minerals. However, magnetite replacing pyrite textures are commonly observed in the retrograded samples. The eclogite-facies and retrograde veins display two fluid events, which are characterized by an early sulfide-bearing and a later magnetite-bearing mineral assemblage, respectively. Textural and petrological evidences show that the sulfides were mainly formed during HP metamorphism. Mineral assemblage transitions reveal that the relative oxygen fugacity of subducted oceanic crust decreases slightly with increasing depths. However, according to oxygen mass balance calculations, based on the oxygen molar quantities (nO(2)), the redox conditions remain constant during HP metamorphism. At shallow levels (<60 km) in the subduction channel, interaction with oxidized fluid seems to have caused an increase of the oxygen fugacity and the oxidation state of exhuming HP rocks. This study suggests that oxygen components are not released in significant amounts during HP metamorphism of subducted oceanic crust and, thus, cannot be responsible for oxidizing the mantle wedge and increasing the oxidation state of sub-arc mantle melts.
机译：一般认为，与俯冲有关的氧化流体或熔体从下降的板块迁移到地幔楔中，是造成了弧下地幔的氧化性质，进而也解释了弧岩浆。鉴于弧下岩浆的氧化态似乎在与弧有关的矿床的形成中起着关键作用，这一点尤其重要。但是，对俯冲洋壳的氧化还原状态的直接约束很少。在这里，我们对来自Akeyazi高压（HP）地层（中国西北）的含硫化物和氧化物的榴辉岩，蓝辉岩，云母，榴辉岩相和逆行脉进行了详细的岩石学研究，以便深入了解氧化还原过程记录在俯冲的海洋平板中。这些岩石中的硫化物主要是黄铁矿和次要的黄铁矿，黄铜矿，斑铜矿，辉钼矿，闪锌矿和黄铜矿，包括斑岩-黄铜矿共生的析出质地。磁铁矿，钛铁矿和黄铁矿以石榴石的夹杂物形式存在，而硫化物在基体中占主导地位。基体中的大型黄铁矿晶粒包含石榴石，绿辉石和其他HP指数矿物。然而，在回生的样品中通常观察到磁铁矿替代黄铁矿的质地。榴辉岩相和逆行脉显示出两种流体事件，其特征分别是早期含硫化物和晚期含磁铁矿矿物组合。纹理和岩石学证据表明，硫化物主要在HP变质过程中形成。矿物组合转变表明，俯冲洋壳的相对氧逸度随深度的增加而略有下降。但是，根据氧气质量平衡计算，基于氧气摩尔量（nO（2）），HP变质过程中氧化还原条件保持恒定。在俯冲通道中的浅水位（<60 km），与氧化流体的相互作用似乎引起了氧逸度的增加和发掘高压岩石的氧化态。这项研究表明，在俯冲洋壳的HP变质过程中，氧组分不会大量释放，因此，不能负责氧化地幔楔和增加亚弧地幔熔体的氧化态。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号