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

前寒武纪地盾含水层由火成岩和变质岩组成，可能是人口的重要水源，例如加拿大的大部分地区。盾牌含水层的地球化学特征是深度（> 1000 m）处存在盐水，这是一种总溶解固体含量超过100，000 mg/L（TDS;海水约35，000 mg/L）的地下水。20世纪80年代，在放射性废物处置库现场调查的推动下，对屏蔽盐水进行了开创性的研究，使用地球化学来表征这些复杂的系统。在加拿大最大的自然地理区域加拿大地盾，在浅层（1000- 10，000 mg/L TDS）发现了微咸地下水（1，000 - 10，000 mg/L TDS），该项目的主要目的是开发方法来追踪微咸地下水的起源，并模拟盐水可能混合和迁移到浅层含水层。该项目针对魁北克西北部的Abitibi矿区，有几个地下矿山，其中一个矿山深度超过3000米。短期目标是：1）使用创新的同位素示踪剂（如稳定的氯和溴同位素）确定各种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确定更新世冰川融水，3）研究裂缝和水的作用;通过裂隙流地球化学和裂隙矿物分析，探讨了岩石相互作用对盐分来源和地下水演化的影响。每个目标将通过博士（2），硕士（1）和本科生（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宝贵的最先进的培训。这项研究的结果将为科学界和工业（采矿、地热、核能）提供新的知识，以减轻深层盐水与浅层地下水的人工迁移和混合的潜在影响。随着矿井越来越深，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液体而导致的设备快速老化。随着加拿大通过可持续利用自然资源促进北方的发展，全面了解地盾卤水的起源和迁移的长期愿景是强制性的，以确保北方和原住民社区的安全饮用水，并为该行业提供知识，以调整其业务，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.