...
  • 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 >The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study
【24h】

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study

机译：硼在花岗石-辉镁岩体系及相关热液中的行为：熔体和流体包裹体研究

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

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt percent H_2O and 1.8 wt percent B_2O. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 deg C, 100 MPa, 20 wt percent H_2O and 4.1 wt percent B_2O_3. Cooling and concomitant fractional crystallisation from 700 to 500 deg C induced development of two conjugate melts, an H_2O-poor (A-melt) and an H_2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H_2O-rich melt. Temperature-dependent distribution coefficients D_(boron)~(B-melt)/A-melt are 1.3 at 650 deg C, 1.5 at 600 deg C, and 1.8 at 500 deg C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt percent was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 deg C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 deg C, along with varying densities and highly variable B_2O_3 contents ranging from 0.20 to 2.94 wt percent. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine-and tin7-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H_2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H_2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.
机译：熔体和流体包裹体的详细分析与含硼矿物的电子探针调查相结合，揭示了硼在高度演化的高铝质花岗岩-透辉石复合物中以及相关的高温和中温成矿热液中的演化（Ehrenfriedersdorf，德国，厄尔士（Erzgebirge）。花岗岩中的熔体夹杂物代表形成胚晶石的熔体，其中含有约10 wt％的H_2O和1.8 wt％的B_2O。这些熔体还富含F，P和其他不相容元素，例如Be，Sn，Rb和Cs。持续的分化和挥发性富集使系统变成了固溶体，其中形成了两个伟晶石的熔体共存。临界点在约712℃，100MPa，20重量％的H_2O和4.1重量％的B_2O_3。冷却和伴随的从700到500摄氏度的分步结晶引发了两个共轭熔体的发展，一个是低H_2O（A熔体），另一个是富H_2O的熔体（B熔体）。硼是两种熔体中的主要元素，并且优先分配到富含H_2O的熔体中。温度相关的分布系数D_（硼）〜（B熔体）/ A熔体在650摄氏度时为1.3，在600摄氏度时为1.5，在500摄氏度时为1.8。在整个塑化阶段都富含硼的高盐盐水。含量高达8.5 wt％的硼硅白云母是此阶段的另一个硼吸收剂。在约490℃的固相线温度下达到了以熔体为主的混凝阶段的终点。热液阶段的流体包裹体显示，捕集温度为480至370℃，密度不同，B_2O_3含量变化很大，范围为0.20至0.50。 2.94重量％。不断发展的沸腾系统表明封闭系统和开放系统之间存在复杂的相互作用。压力从岩石静压切换到静水压，然后又返回，从而产生热液对流单元，在其中引入了流水并与岩浆流体混合。富含硼的溶液起源于岩浆流体，而贫硼的流体主要来自陨石。这突出了硼区分不同来源流体的潜力。锡在演化过程中不断富集，因为锡和硼通过形成含硼，氟和锡7-氟的配合物而交联，并最终在从封闭系统行为向开放系统行为的转变过程中沉积在石英-锡石脉中。 。硼不仅追踪Ehrenfriedersdorf配合物的复杂演化过程，而且与H_2O，F和P一起对形成伟晶石的熔体的物理和化学性质，特别是在2熔体固溶体的形成上具有重要的控制作用。低压。我们讨论有关H_2O溶解度的实验结果和含有可变浓度挥发物的辉锰矿-水系统的临界行为。

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