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

矿床是地球化学的主要异常。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以在几千到几百万年的时间里留下几公里范围内的特征。这些系统的系统时空变异性表明哪些是起作用的主要地球化学过程，哪些是成矿的潜在良好指标，哪些是流体和热源的矢量。本研究计划的主要目的是将矿石流体的化学成分与寄主岩石的化学和矿物组成结合起来，以约束矿床形成中的一些主要控制因素。***未来五年我将重点研究钨矿床。钨是一种重要的金属，加拿大是世界五大生产国之一，西北地区历史上是主要出口国。钨在地质上的赋存条件是相当普遍的（厚的变质沉积岩包体伴有减少的岩浆活动）。然而，钨矿是高度局部化的。特别是NWT和YK交界的钨矿带构成了北美西部唯一的主要产钨省。因此，本项目将侧重于(1)确定钨的富集度是在热液阶段还是在更早阶段（在流体-熔体分配或熔体源）受到控制，以及对全球分布的影响；(2)以钨矿为例，确定在深部条件下形成的热液系统的水文特征；(3)确定哪些元素表征钨矿化流体，以及它们在多大规模上可能导致异常。***本项目中用于流体化学表征的方法包括岩石学、流体包裹体测温和激光烧蚀电感耦合等离子体质谱法。这些技术将提供富钨与贫钨体系中PT包埋条件、挥发性和阳离子含量的变化情况，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探针将提供关于流体来源变化如何随时间影响共生和流体化学演变的配对信息。通过便携式技术（x射线荧光）、通过传统的XRF和溶出方法、XRD和SEM对整个岩石进行分析，可以进一步表征宿主岩石中的流体-岩石相互作用。流体化学与手工样品、矿物学和化学的结合将提供有关哪些元素可能在局部被缓冲，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.