Geological Survey of Canada, 601 Booth Street, Ottawa, ON K1A 0E8, Canada; Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Sci Total Environ. 2022 Mar 1;810:151215. doi: 10.1016/j.scitotenv.2021.151215. Epub 2021 Nov 5.
Locating mineral deposits in areas of thick or transported overburden is notoriously difficult. Post-mineral cover is prevalent in many parts of the globe and has led to prospective geological sequences being missed by traditional methods of exploration. Hydrogeochemistry is particularly applicable for the exploration of Iron Oxide Copper Gold (IOCG) deposits because, when compared to larger porphyry or sediment-hosted systems, IOCG deposits tend to be smaller and high-grade with a limited lateral footprint to intersect with grid-drilling; groundwater interactions and ion dispersion tend to produce a much larger anomaly target than regolith geochemistry alone and require fewer samples. As a case study, we examine the hydrogeochemistry of the Kitumba IOCG deposit, located in the Mumbwa district of west-central Zambia. We present physicochemical data (Eh, pH, TDS, conductivity), major and trace element concentrations, and isotopic compositions (δMo, Sr/Sr, and δCu) from groundwaters interacting with the Kitumba deposit and surrounding prospects. A hydrogeochemical footprint of As, Mo, Fe, Mn, and Zn is dispersed from the deposit. Groundwater Sr/Sr values (0.708832 to 0.731807) reflect the mixing in varying proportions of waters that have interacted with distinct lithological endmembers in the Mumbwa area, corresponding to a complicated tectonic and metamorphic history. We report fractionation of 1.34 to 1.60‰ (∆Cu) between proximal groundwater and primary chalcopyrite, which we postulate may be related to the oxidative dissolution of primary sulfide minerals. The δMo values of groundwaters proximal to known ore bodies are isotopically distinct (-1.08 ± 0.18‰ 2SE to 0.64 ± 0.08‰ 2 SE) from background aquifers (2.08 ± 0.12‰ 2SE). The trace element and isotopic hydrogeochemical patterns described in this study document water-rock and water-deposit interactions and demonstrate the potential of non-traditional stable isotopes to be employed in district-scale reduction of exploration ground and vectoring towards undisturbed ore deposits similar to Kitumba.
在厚覆盖层或运移覆盖层的区域中定位矿床是众所周知的难题。在全球许多地区都存在后成矿覆盖物，这导致传统勘探方法错过了潜在的地质序列。水文地球化学特别适用于铁氧化物铜金（IOCG）矿床的勘探，因为与较大的斑岩或沉积岩系相比，IOCG 矿床通常规模较小，品位较高，与网格钻探相交的横向足迹有限；地下水相互作用和离子分散作用往往产生比风化壳地球化学更大的异常目标，所需的样本也更少。作为一个案例研究，我们研究了位于赞比亚中西部芒布瓦地区的基图姆巴 IOCG 矿床的水文地球化学。我们展示了与基图姆巴矿床和周围远景相互作用的地下水的物理化学数据（Eh、pH、TDS、电导率）、主要和微量元素浓度以及同位素组成（δMo、Sr/Sr 和 δCu）。来自矿床的 As、Mo、Fe、Mn 和 Zn 的水文地球化学足迹呈分散状。地下水 Sr/Sr 值（0.708832 至 0.731807）反映了与芒布瓦地区不同岩性端元以不同比例混合的水，反映了复杂的构造和变质历史。我们报告了近地表水和原生黄铜矿之间 1.34 至 1.60‰（∆Cu）的分馏，我们推测这可能与原生硫化物矿物的氧化溶解有关。与已知矿体相邻的地下水的 δMo 值在同位素上与背景含水层明显不同（-1.08±0.18‰ 2SE 至 0.64±0.08‰ 2SE）。本研究中描述的微量元素和同位素水文地球化学模式记录了水-岩和水-矿床相互作用，并证明了非传统稳定同位素在矿区尺度勘探减少和定向到类似于基图姆巴的未扰动矿床方面的潜力。
