Combining paleofluid chemistry and rock characterization to constrain genetic processes in tungsten deposits.

矿床是主要的化探异常。含金属相的析出可以在空间和时间上局部化。然而，导致金属沉淀的地球化学过程可能会在几公里和数千至数百万年的范围内留下痕迹。这些系统的系统的空间和时间变异性提供了哪些是起作用的主要地球化学作用，哪些是潜在的良好矿化指示物以及指向流体和热源的载体的指示。这项研究计划的主要目标是将成矿流体的化学成分与赋矿岩石的化学和矿物学成分结合起来，以限制矿床形成中的一些主要控制因素。*在未来五年，我将专注于研究钨矿床。钨是一种关键金属，加拿大是全球五大生产国之一，西北地区历史上是主要的出口国。钨在地质上的赋存条件是相当常见的(厚厚的变质沉积包体伴随着减少的岩浆作用)。然而，钨矿床是高度本地化的。特别是，西北地区和伊利诺伊州交界处的钨矿带是北美西部唯一的主要钨生产省。因此，该计划将集中于(1)确定钨的丰度是在热液阶段还是在早期阶段(在流体-熔体分配或熔融源处)受到控制，以及对全球分布的影响；(2)以钨矿床为例，确定在深部条件下形成的热液系统的水文；(3)确定哪些元素表征了钨成矿流体，以及它们可能在多大程度上导致异常。*本项目中用于流体化学表征的方法将包括岩石学、流体包裹体测温和激光烧蚀电感耦合等离子体质谱。这些技术将提供有关富钨和贫钨体系中流体的捕集、挥发和阳离子含量的PT条件如何变化以及它们如何随时间和空间变化的信息。结合二次电子显微镜和离子微探针，将提供关于流体来源的变化如何影响共生作用和流体化学随时间演变的配对信息。将通过便携式技术(X射线荧光)、通过常规XRF和消化方法进行的全岩分析、X射线衍射和扫描电子显微镜，进一步表征寄主岩石中的流体-岩石相互作用。流体化学与手样和矿石标度的矿物学和化学相结合，将提供哪些元素可能在局部缓冲，哪些元素可能导致与这些矿床类型相关的远端异常的信息。

Ore deposits are major geochemical anomalies. Precipitation of metal-bearing phases can be spatially and temporally localized. However, the geochemical processes that lead to metal precipitation can leave signatures over ranges of several kilometers and over thousands to millions of years. The systematic spatial and temporal variability in these systems provides indication of which are the main geochemical processes at work and what are potential good indicators of mineralization and vectors toward fluid and heat sources. The main objective of this research program is to combine the chemistry of ore fluids with the chemical and mineralogical composition of host rocks to constrain some of the major controls in ore deposit formation. ***In the next five years I will focus on studying tungsten deposits. Tungsten is a critical metal, with Canada being one of the five major producers worldwide and NWT being a major exporter historically. The conditions under which tungsten occur geologically are fairly common (thick metasedimentary packages with associated reduced magmatism). However tungsten deposits are highly localized. In particular the Tungsten belt in the border between NWT and YK constitutes the only major tungsten-producing province in western North America. Therefore this program will focus on (1) determining whether tungsten fertility is controlled at the hydrothermal stage or at an earlier stage (at fluid-melt partitioning or melt source) and the implications for global distribution, (2) determining the hydrology of hydrothermal systems formed at deep conditions using tungsten deposits as an example and (3) define which elements characterize tungsten mineralizing fluids and at which scale they are likely to cause anomalies.***The approaches used in this project towards chemical characterization of fluids will include petrography, fluid inclusion thermometry and laser ablation inductively coupled plasma mass spectrometry. These techniques will provide information on how the PT conditions of entrapment, volatile and cation content of the fluid vary in tungsten-rich vs tungsten-poor systems and how they change with time and space. Combination with secondary electron microscopy and ion microprobe will provide paired information on how changes in the source of fluids may influence the evolution of paragenesis and fluid chemistry over time. Further characterization of fluid-rock interaction in the host rocks will be achieved through portable techniques (X-ray fluorescence), whole rock analyses through conventional XRF and digestion methods, XRD and SEM. Combination of fluid chemistry with hand sample and ore scale mineralogy and chemistry will provide information on which elements are likely to be buffered locally and which ones are likely to cause distal anomalies associated with these deposit types.