Basinal fluid flow systems and their relationships with mineralization - driving forces, paths and traps

许多矿床是沉积盆地中地质流体循环作用形成的。了解这些流体流动系统的运行机制，包括它们的驱动力、路径以及与不同岩性和/或流体的反应，导致矿床矿物(圈闭)的沉淀，对矿产勘查具有重要意义。我研究的主要目标是加强我们对这些盆地成矿系统的了解，并建立有助于识别成矿有利位置的工具或地质标准。拟议的研究重点是与萨斯喀彻温省北部阿萨巴斯卡盆地有关的铀矿化，该盆地拥有世界上最丰富的铀矿床。自近50年前在阿萨巴斯卡盆地首次发现这种类型的铀矿(称为不整合型铀矿床，因为它们位于盆地与基底之间的不整合附近)以来，人们进行了广泛的研究，建立了综合成矿模式(称为成岩-热液模式)。为了更好地指导找矿，提高成矿成功率，一代又一代的地球科学家不断努力完善成矿模式。在我之前的发现赠款中，我的研究小组发现了证据，表明阿萨巴斯卡盆地的铀矿化可能发生在更浅的深度(5公里)，富铀流体的有限分布，而不是(如常规勘探模式所暗示的)沉淀铀矿所需的还原剂的可用性，是决定是否以及在哪里可能形成铀矿床的关键因素。此外，发现与铀矿化有关的流体流动受重新激活的基底断裂控制，这不仅是因为这些断裂可以作为输导，还因为它们可以控制流体对流单元的位置，并提供流体流动的驱动力，从而解释成矿特征所显示的进出流模式。基于这些发现，我们建议开展新的研究，以进一步圈定铀矿化和盆地卤水(成矿流体的母体)发育的时间，卤水从盆地上部到盆地底部和基底的可能路径，盆地卤水和基底断层(包括浅层和深层)之间的流体动力学关系，以及促进富铀流体通道的物理和化学圈闭及其与(流体或岩石中的)还原剂的反应。研究结果将完善成矿模型，更好地指导勘探。这项研究对加拿大作为世界第二大铀生产国和铀地质研究的领先国家之一具有重要意义。

Many mineral deposits formed from circulation of geologic fluids in sedimentary basins. Understanding the operation mechanisms of these fluid flow systems, including their driving forces, paths and reaction with various lithologies and/or fluids leading to precipitation of ore minerals (traps), is important for mineral exploration. The primary goal of my research is to enhance our understanding of these basinal mineralization systems and to establish tools or geologic criteria that can help identify favorable locations for mineralization. The proposed research focuses on uranium mineralization associated with the Athabasca Basin in northern Saskatchewan, which contains the richest uranium deposits in the world. Since the first discovery of this type of uranium deposits (named unconformity-type because they occur near the unconformity between the basin and its basement) in the Athabasca Basin nearly 50 years ago, extensive studies have been carried out and a comprehensive mineralization model (called the diagenetic-hydrothermal model) has been established. Generations of geoscientists have been continuously making effort to improve the mineralization model in order to better guide exploration and increase the success rate. In my previous Discovery Grant, my research team has found evidence suggesting that the uranium mineralization in the Athabasca Basin may have taken place at much shallower depths ( 5km), and that the limited distribution of uranium-rich fluids, rather than the availability of reducing agents required to precipitate uraninite (as implied in the conventional exploration model), was the key factor determining whether or not and where uranium deposits may form. Furthermore, it was found that fluid flow related to uranium mineralization was controlled by reactivated basement faults, not only because these faults may be used as conduits, but also because they can control the location of fluid convection cells and can episodically provide the driving force for fluid flow that can explain the ingress and egress flow patterns demonstrated by the mineralization features. Based on these findings, we propose to carry out new research to further delineate the timing of uranium mineralization and basinal brine (parent of the ore-forming fluid) development, the possible paths of the brine from the upper part to the basal part of the basin and the basement, the hydrodynamic relationships between the basinal brine and basement faults (both shallow- and deep-seated), and physical and chemical traps that promote channeling of uranium-rich fluids and their reaction with reducing agents (either in fluid or rock). The results will refine the mineralization model to better guide exploration. The research is important for Canada as the second largest uranium producer in the world and one of the leading countries in uranium geology study.