A multi-tracers approach to quantifying Shield brines mixing and migration from deep to shallow aquifer systems

由火成岩和变质岩组成的前寒武纪地盾含水层可能是人类的重要水源，例如加拿大的大部分地区。地盾含水层的地球化学特征是存在于深度（> 1000 m）的盐水，一种总溶解固体（TDS）超过100,000 mg/L的地下水，海水约35,000 mg/L。20世纪80年代，在放射性废物处置库现场调查的推动下，对盾卤水进行了开创性的研究，利用地球化学来表征这些复杂的系统。在加拿大最大的地理区域——加拿大地盾，在浅层深处发现了微咸地下水（TDS为1000-10,000 mg/L）（该项目的目的是开发追踪微咸地下水来源的方法，并模拟盐水混合和迁移到浅层含水层的可能性）。该项目有几个地下矿井，其中一个超过3000米深，目标是魁北克省西北部的阿比提比矿区。短期目标是：1)利用创新的同位素示踪剂作为稳定的氯和溴同位素来识别不同来源的水和混合动力学；2)通过研究Barlow-Ojibway粘土孔隙水的水稳定同位素来定义更新世冰川融水；3)通过分析裂缝流动地球化学和裂缝矿物来研究裂缝和水/岩相互作用对盐度来源和地下水演化的作用。每个目标将通过博士(2)，硕士(1)和学士(3)的项目来解决。他们将在加拿大面临专业人才短缺的领域获得有价值的、最先进的培训。这项研究的结果将为科学界和工业界（采矿、地热、核能）提供新的知识，以减轻诱导迁移和深层盐水与浅层地下水混合的潜在影响。随着矿山越来越深，该行业面临着抽取含盐地下水的重大挑战，以及由于腐蚀性很强的流体而导致设备迅速老化的问题。随着加拿大通过可持续利用自然资源来促进北部地区的发展，全面了解Shield卤水的来源和迁移是强制性的长期愿景，以确保北部和第一民族社区的安全饮用水，并为该行业提供适应其运营的知识，并减轻对浅层地下水资源的潜在影响。

Precambrian Shield aquifers, composed of igneous and metamorphic rocks, may represent a vital source of water for population, such as the large parts of Canada. The geochemistry of Shield aquifers is characterized by the presence at depth (> 1000 m) of brines, a groundwater with more than 100,000 mg/L total dissolved solids (TDS; seawater about 35,000 mg/L). Pioneering studies on Shield brines in the 1980's, driven by radioactive waste repository site investigations, used geochemistry to characterize these complex systems. In the Canadian Shield, the largest physiographic region in Canada, brackish groundwater (1000-10,000 mg/L TDS) was identified at shallow depths ( of this program is to develop approaches to trace the origin of brackish groundwater and to model the potential mixing and migration of brines into shallow aquifers. With several underground mines, including one site more than 3000 m deep, this program targets the Abitibi mining region, northwestern Quebec. The short-term objectives are 1) to identify water of various origin and mixing dynamics using innovative isotopic tracers as stable chlorine and bromine isotopes, 2) to define the Pleistocene glacial meltwater by studying water stable isotopes of Barlow-Ojibway clay pore water, and 3) to investigate the role of fractures and water/rock interaction on sources of salinity and groundwater evolution by analyzing fracture flow geochemistry and fracture minerals. Each objective will be addressed through projects of doctorate (2), master (1), and bachelor students (3). They will gain valuable, state of the art training in a field that faces a shortage of professionals in Canada. The results from this research will provide new knowledge to the scientific community and industry (mining, geothermal, nuclear) to mitigate potential impacts of induced migration and mixing of deep brines with shallow groundwater. As mines are getting deeper, the industry faces major challenges with the pumping of saline groundwater, and with the quick deterioration of equipment due to the very corrosive fluids. With Canada fostering the development of the North through sustainable use of natural resources, such a long-term vision to get a comprehensive understanding of the origin and migration of Shield brines is mandatory to assure safe drinking water to northern and First Nations communities, as well as to provide the industry with knowledge to adapt their operations, and to mitigate potential impacts on shallow groundwater resources.