Fluid sources in basement-hosted unconformity–uranium ore systems: tourmaline chemistry and boron isotopes from the Patterson Lake corridor deposits, Canada

IF 1 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Geochemistry-Exploration Environment Analysis Pub Date : 2021-12-01 DOI:10.1144/geochem2021-037

E. Potter, C. J. Kelly, W. Davis, G. Chi, S-Y. Jiang, M. Rabiei, B. McEwan

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引用次数: 2

Abstract

The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact. Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555 Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways

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基底不整合-铀矿石系统中的流体来源：加拿大帕特森湖走廊矿床的电气石化学和硼同位素

帕特森湖走廊是位于阿萨巴斯卡盆地西南边缘的一个新的铀区。已知资源扩展近1 高度蚀变变质岩中含石墨和硫化物剪切带的不整合面以下km处。尽管不整合面下的寄主岩石不同，深度更大，但蚀变组合（绿泥石、伊利石、高岭石、电气石和赤铁矿）、矿石品位和质地是不整合面相关矿床的典型特征。这种蚀变包括至少三代富含镁的电气石（镁质亚铁矿石）。镁铁铁矿的硼同位素组成随时代而变化：最早的一代，仅在Triple R矿床（Tur 1）的浅层样品中观察到，含有最重的同位素特征（δ11B ≈ 19–26‰），而随后的几代（Tur 2和Tur 3）产生了更轻、更均匀的同位素特征（δ11B ≈ 17.5–19.9‰）。这些结果与来自同位素重硼源（如蒸发海水）的低温、富含NaCl和CaCl2的盐水的沉淀一致，该盐水与基岩中的电气石和硅酸盐和/或来自深度的流体（具有低δ11B值）相互作用。共生晚期镁质亚铁矿石中较低的δ11B值反映了随着时间的推移，基底衍生硼的贡献更大，而较小的成分变化反映了局部金属源（如Cr、V、Ti）和随时间变化的流体化学（Na和Ca减少，Mg增加）。随着时间的推移，镁铁铁矿的δ11B和化学变化增强了与这些系统中基岩的强烈相互作用，同时支持了不整合接触下方的盆地卤水侵入。补充材料：包括参考材料在内的完整分析数据集可在https://doi.org/10.6084/m9.figshare.c.5727555主题收藏：本文是铀流体通道收藏的一部分，可在以下网站获取：https://www.lyellcollection.org/cc/uranium-fluid-pathways

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来源期刊

Geochemistry-Exploration Environment Analysis 地学-地球化学与地球物理

CiteScore

3.60

自引率

16.70%

发文量

审稿时长

1 months

期刊介绍： Geochemistry: Exploration, Environment, Analysis (GEEA) is a co-owned journal of the Geological Society of London and the Association of Applied Geochemists (AAG). GEEA focuses on mineral exploration using geochemistry; related fields also covered include geoanalysis, the development of methods and techniques used to analyse geochemical materials such as rocks, soils, sediments, waters and vegetation, and environmental issues associated with mining and source apportionment. GEEA is well-known for its thematic sets on hot topics and regularly publishes papers from the biennial International Applied Geochemistry Symposium (IAGS). Papers that seek to integrate geological, geochemical and geophysical methods of exploration are particularly welcome, as are those that concern geochemical mapping and those that comprise case histories. Given the many links between exploration and environmental geochemistry, the journal encourages the exchange of concepts and data; in particular, to differentiate various sources of elements. GEEA publishes research articles; discussion papers; book reviews; editorial content and thematic sets.