近日，法国索邦大学Georges Calas团队研究了烧绿石纳米矿物学分析质疑铌在热带风化过程中的不动性。相关论文发表在2025年11月19日出版的《地质学》杂志上。

尽管越来越多的证据（尤其在强风化土层中）表明铌等低溶解度元素在表生风化过程中具有迁移性，但其迁移机制始终未明。在临界带中，这些高场强元素（HFSEs）的低迁移性通常归因于其宿主矿物的抗风化能力，该特性使其成为量化蚀变过程中元素迁移的地球化学示踪剂。烧绿石作为典型的抗风化矿物，承载了绝大多数高场强元素。

研究组通过纳米尺度分析技术，对经历数百万年强烈风化的典型红土剖面中烧绿石表面蚀变层进行观测。剖面中多孔状烧绿石边部呈现独特的化学成分特征，其钍含量显著增高。在铅富集与钍富集烧绿石交界处发现的纳米级锐利化学界面和结构界面，为界面耦合的溶解-再沉淀过程提供了有力证据。这表明在热带风化过程中，烧绿石的铌氧八面体骨架具有可蚀变性，而富钍烧绿石则保持相对稳定。对另外两个红土层的富铈烧绿石进行纳米分析，证实该迁移机制在整个矿床具有普适性。

在锰质脉体中发现的次生纳米铈铀矿内含铌元素，直接证实了风化过程中铌的迁移现象。这些对次生组合物的纳米矿物学研究，首次在矿床尺度提供了铌在风化过程中迁移的直接证据，强调有必要重新评估高场强元素在地球表层的生物地球化学循环——特别是在采矿规模持续扩大的背景下。该研究为纳米尺度探究抗风化矿物蚀变机制开辟了新路径，通过揭示前所未有的地质过程，为元素迁移-固定模型构建提供了新范式。

附：英文原文

Title: Pyrochlore nanomineralogy questions the immobility of niobium during tropical weathering

Author: Quentin Bollaert, Mathieu Chassé, Nicolas Menguy, Corentin Le Guillou, Artur Bastos Neto, David Troadec, Laurence Galoisy, Georges Calas

Issue&Volume: 2025-11-19

Abstract: The origin of the mobility of low-solubility elements such as niobium during supergene weathering remains elusive, despite growing evidence, especially in strongly weathered regolith. In the critical zone, the low mobility of these high field strength elements (HFSEs) is assigned to the resistance of their mineral hosts. This property led to their use as geochemical invariants to quantify mass transfer during alteration. Pyrochlore is a quintessential weathering-resistant mineral accommodating most HFSEs. Here, we investigate the surface alteration layers of pyrochlore using a nanoscale approach within a well-characterized regolith subject to intense weathering over millions of years. In the profile, porous pyrochlore rims exhibit distinct chemistry with higher Th contents. Sharp chemical and textural nanometer-scale interfaces between Pb-rich and Th-rich pyrochlore provide compelling evidence for interface-coupled dissolution-reprecipitation. This demonstrates the alterability of the Nb octahedral framework in pyrochlore and the relative stability of its Th-rich counterpart during tropical weathering. Nanoscale analyses of Ce-rich pyrochlores in two additional lateritic horizons confirm the generality of this mechanism across the deposit. The presence of Nb in secondary nano-cerianite found in manganiferous veins establishes its transport during weathering. These nanomineralogical studies of secondary assemblages provide the first direct evidence of Nb mobility during weathering at the deposit scale, underscoring the need to reappraise HFSE geochemical cycles at Earth’s surface, especially in light of growing mining volumes. This paves the way for further investigations into the alteration of weathering-resistant minerals at the nanoscale, providing new models of mobilization and sequestration through previously undocumented processes.

DOI: 10.1130/G53465.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G53465.1/697025/Pyrochlore-nanomineralogy-questions-the-immobilityredirectedFrom=fulltext