Metal isotopes as chemical weathering tracers

全球气温上升导致冰川融化和永久冻土融化增加，导致硅酸盐、硫化物和碳酸盐风化加剧。在以物理侵蚀为主的冰川地区，硫化物风化程度升高会产生能够溶解碳酸盐的酸性，部分抵消了硅酸盐风化对二氧化碳的消耗。了解影响二氧化碳释放或减少的风化通量的平衡，对于理解未来的全球变暖至关重要。因此，迫切需要开发可靠的化学风化示踪剂，这将需要全面了解同位素分馏过程。长期目标是利用金属同位素促进对金属循环的理解，金属循环对自然资源的勘探、污染物的去向和迁移、资源开发(如采矿、页岩气开采和地质碳储存)对地表水和地下水的数量和质量的影响具有重要影响。五年(2020-2025年)的具体目标是开发7Li/6Li和71Ga/69Ga作为化学风化替代物的应用，特别是在87Sr/86Sr支持下区分硅酸盐、硫化物和碳酸盐风化过程。这一目标可以通过三个极具创新性的目标来实现：1)评估干旱环境中次生矿物形成和有机聚集在控制Li浓度和同位素组成方面的作用；2)通过实验室实验和地球化学模拟，确定大陆风化过程中Ga同位素分馏的大小和机制；然后，实验结果将用于解释格陵兰扎肯伯格河流域的Ga同位素行为；3)通过表征沉淀物和温泉水中的Ga同位素与各种基岩地形平衡的特征，评价富硫酸盐和酸性环境中的Ga同位素地球化学；然后将检验铁胶体在日本玉马川温泉补给的河流输送过程中对Ga同位素分馏的吸附作用。放射性成因的锶同位素主要用作支持对控制Li和Ga同位素地球化学的地球化学过程的理解的工具。这一研究计划将促进对Ga同位素分馏过程的理解，从而为利用Ga同位素作为地球化学示踪剂，特别是在追踪硅酸盐与硫化物的风化过程中提供基础，这对于理解未来的全球变暖是必要的。了解干旱环境中的锂循环将促进对锂的重要经济来源的了解。此外，加拿大缺乏高素质的人才(HQP)。根据该计划培训的HQP将获得强大的地球化学知识和技术技能，以应对与自然资源开发和气候变化有关的环境问题的科学挑战。

The rising global temperature is leading to increasing glacial melting and permafrost thawing, resulting in enhanced silicate, sulfide, and carbonate weathering. Elevated sulfide weathering in glaciated regions dominated by high physical erosion generates acidity that can dissolve carbonate, partially counteracting CO2 consumption by silicate weathering. Understanding the balance of the weathering fluxes, which affect the release or drawdown of CO2, is critical for understanding future global warming. Thus, there is a pressing need to develop reliable chemical weathering tracers which will require a comprehensive understanding of isotope fractionation processes. The long-term goal is to use metal isotopes to advance the understanding of metal cycles, which have important implications on the exploration of natural resources, fate and transport of contaminants, impacts of resource development such as mining, shale gas extraction, and geological carbon storage on the quantity and quality of surface water and groundwater. The specific goal for a five-year period (2020-2025) is to develop the applications of 7Li/6Li and 71Ga/69Ga as chemical weathering proxies, particularly in distinguishing silicate, sulfide, and carbonate weathering processes with the support of 87Sr/86Sr. This goal can be achieved through three highly innovative objectives: 1) Assess the role of secondary mineral formation and organic accumulation in controlling Li concentration and isotope composition in arid environments; 2) Determine the magnitudes and mechanisms of Ga isotope fractionation during continental weathering processes, through laboratory experiments and geochemical modelling; then experimental results will be used to interpret Ga isotope behavior in the Zackenberg River Catchment of Greenland; 3) Evaluate the Ga isotope geochemistry in sulfate rich and acidic environments by characterizing Ga isotopes in precipitates and hot spring waters in equilibrium with a variety of bedrock terrains; then the role of adsorption by iron colloids on Ga isotope fractionation during transport in rivers fed by Tamagawa hot springs (Japan) will be tested. Radiogenic Sr isotopes are mainly used as a tool to support the understanding of geochemical processes controlling Li and Ga isotope geochemistry. This research program will advance understanding of Ga isotope fractionation processes, thus, providing a foundation to use Ga isotopes as a geochemical tracer, particularly in tracing silicate vs. sulfide weathering processes, which is necessary for understanding future global warming. Understanding of Li cycles in arid environments will advance knowledge of economically significant sources of Li. Moreover, there is a shortage of highly qualified personnel (HQP) in Canada. HQP trained under this program will gain strong knowledge and technical skills in geochemistry to tackle scientific challenges regarding environmental issues related to natural resource development and climate change.