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

基底流体流动系统及其与矿化的关系——驱动力、路径和圈闭

• 批准号: RGPIN-2018-06458
• 负责人: Chi, Guoxiang
• 金额: $ 2.62万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=647513
• 关键词: Basinal; fluid; flow; systems; their

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.

许多矿床是由沉积盆地中的地质流体循环而形成的。了解这些流体流动系统的运行机制，包括它们的驱动力、路径以及与各种岩性和/或流体的反应，从而导致矿物沉淀（圈闭），对于矿产勘探是重要的。我的研究的主要目标是提高我们对这些盆地矿化系统的理解，并建立工具或地质标准，可以帮助确定有利的矿化位置。拟议的研究重点是与萨斯喀彻温省北方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。自50年前在阿萨巴斯卡盆地首次发现这种类型的铀矿床（因其产于盆地与基底之间的不整合面附近而命名为不整合面型）以来，人们进行了广泛的研究，并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工作，提高找矿成功率，一代又一代地学工作者一直在努力改进成矿模式。在我之前的发现补助金中，我的研究团队发现的证据表明，阿萨巴斯卡盆地的铀矿化可能发生在更浅的深度（5公里），而且富铀流体的有限分布，而不是沉淀晶质铀矿所需的还原剂的可用性（如传统勘探模式所暗示的那样），是决定铀矿床是否以及在何处形成的关键因素。此外，还发现与铀成矿有关的流体流动受复活的基底断裂的控制，这不仅是因为这些断裂可以用作管道，而且还因为它们可以控制流体对流单元的位置，并可以为流体流动提供动力，从而可以解释矿化特征所表现出的流入和流出模式。在此基础上，我们建议开展新的研究，进一步圈定铀矿化和盆地卤水的时代（成矿流体母源）的发育、盆地上部卤水向盆地底部和基底的可能运移路径、盆地卤水与基底断裂的水动力关系（浅埋和深埋）以及促进富铀流体窜流及其与还原剂（流体或岩石中）反应的物理和化学陷阱。研究成果将完善成矿模式，更好地指导找矿工作。加拿大是世界上第二大铀生产国，也是铀地质研究的主要国家之一。