Release and partitioning of neodymium and its radiogenic isotope during basaltic weathering

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-07-10 DOI:10.1016/j.chemgeo.2025.122957

Anup Kumar Sharma, Tarun Kumar Dalai, Prem Chand Kisku, Jitendra Kumar Pattanaik, Sambuddha Misra, Shivansh Verma, Anil Dutt Shukla

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Abstract

Studies on the chemical weathering of rocks on continents are essential for developing and refining elemental and isotopic compositions as robust tracers of weathering. In this study, we investigate chemical weathering in two basaltic weathering profiles from the Rajmahal Volcanic Province in India, after a thorough evaluation of their preservation state and potential external contamination. This investigation included measurements of major and trace elements concentrations, and 143Nd/144Nd ratios (expressed as εNd) in bulk samples and chemically extracted exchangeable and oxyhydroxide phases. The major element compositions clearly indicate progressive chemical weathering in both profiles. Based on variations in [Sm], [Nd] and εNd as a function of the chemical index of alteration (CIA), we infer that the preferential release of radiogenic neodymium (143Nd) results from differential chemical weathering of minerals such as pyroxene. Using Th as a reference immobile element, we estimate that up to 40 % of Nd is lost from the parent basalts during weathering. The εNd values of the weathering solutions, calculated based on mass balance considerations, are ~5.0 units higher than that of the parent basalts. Our results also unequivocally demonstrate that the degree of radiogenic Nd release is correlated with CIA. Reports of extensive Nd adsorption onto river sediments and their εNd difference between the leachate and residual phases allow us to posit that riverine particulate εNd would be modulated during fluvial transport.

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玄武岩风化过程中钕的释放和分配及其放射性成因同位素

研究大陆岩石的化学风化作用对于发展和完善作为风化作用有力示踪剂的元素和同位素组成是必不可少的。本文对印度Rajmahal火山省的两个玄武岩风化剖面进行了化学风化研究，并对其保存状态和潜在的外部污染进行了全面评估。这项研究包括测量大量样品和化学提取的交换相和氢氧化物相中的主要元素和微量元素浓度，143Nd/144Nd比值（以εNd表示）。在两个剖面中，主要元素组成清楚地显示出渐进的化学风化作用。根据[Sm]、[Nd]和εNd随蚀变指数（CIA）的变化，推测放射成因钕（143Nd）的优先释放是由辉石等矿物的不同化学风化作用引起的。以Th作为参考不动元素，我们估计在风化过程中，高达40 %的Nd从母玄武岩中丢失。经质量平衡计算，风化溶液的εNd值比母玄武岩高~5.0 个单位。我们的结果也明确表明，放射性Nd释放的程度与CIA相关。河流沉积物对Nd的广泛吸附及其在渗滤液相和残留相之间的εNd差异的报道使我们能够假设河流颗粒εNd在河流运输过程中会被调节。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Chemical Geology 地学-地球化学与地球物理

CiteScore

7.20

自引率

10.30%

发文量

374

审稿时长

3.6 months

期刊介绍： Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry. The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry. Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry. The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.