87Sr/86Sr of Ca-sulfates and water in Atacama Desert as tracer for Ca sources and hydrological distribution processes

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-07-12 DOI:10.1016/j.chemgeo.2025.122956

Katharina Deußen, Carsten Münker, Michael Staubwasser

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引用次数: 0

Abstract

The Atacama Desert, known as the driest region on Earth, has accumulated substantial salt deposits owing to hyperarid conditions prevailing since the Miocene. These salt deposits mainly include Ca-sulfates and halite, but are also known for their large nitrate deposits. This study focuses on the sources of Ca-sulfates, which occurs in a great mineralogical and compositional diversity. Previous research argued that main sources contributing sulfate to the Atacama salt budget include secondary atmospheric sulfate and biologically recycled sulfate. Secondary atmospheric sulfate originates mostly from marine and atmospheric sources. Additionally, sources delivering Ca into the Atacama Desert include weathered material from the Andes, which is transported by rivers and groundwater flow into the Central depression and to a somewhat lesser extent also marine aerosols. However, there are still open issues, in particular with respect to the elemental mass balances of Ca and sulfur that are different because of contrasting relative abundances in seawater derived components and weathering products. This study uses 87Sr/86Sr isotope compositions of both lacustrine as well as pedogenic Ca sulfates and water samples to further investigate sources and transport pathways of Ca within the Atacama Desert. Two case studies from the driest portion of the Atacama Desert, namely the Tiliviche basin (−19.5°S) and the Quillagua-Llamara-Basin (−21.5°S), are investigated in detail. The sulfate samples and their detrital impurities were dissolved utilizing a newly developed method for selective digestion of Ca-sulfates, using anion exchange resin. This method allows for rapid dissolution of Ca-sulfate samples without affecting inherent siliciclastic material. The water samples analyzed exhibit a moderately radiogenic range in 87Sr/86Sr of ~0.7063 to ~0.7075. Fossil salar Ca-sulfates display less variation, ranging from ~0.7065 to ~0.7072, whereas pedogenic samples diverge toward higher values, spanning a range from ~0.7067 to ~0.7081. Siliciclastic particles, incorporated within the Ca-sulfates, span a wider 87Sr/86Sr range from ~0.7058 to ~0.7095.

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Atacama沙漠中Ca-sulfate和water的87Sr/86Sr作为Ca来源和水文分布过程的示踪剂

阿塔卡马沙漠被称为地球上最干燥的地区，由于中新世以来普遍存在的极度干旱条件，已经积累了大量的盐矿。这些盐沉积物主要包括硫酸钙和盐岩，但也以其大量的硝酸盐沉积物而闻名。本文研究的重点是硫酸钙的来源，其矿物学和成分具有很大的多样性。先前的研究认为，向阿塔卡马盐预算贡献硫酸盐的主要来源包括二次大气硫酸盐和生物回收硫酸盐。次生大气硫酸盐主要来源于海洋和大气。此外，向阿塔卡马沙漠输送钙的来源包括安第斯山脉的风化物质，这些物质通过河流和地下水流入中央洼地，在较小程度上也包括海洋气溶胶。然而，仍然存在一些悬而未决的问题，特别是关于钙和硫的元素质量平衡，由于海水衍生成分和风化产物中相对丰度的对比而不同。本研究利用湖相和成土钙硫酸盐和水样的87Sr/86Sr同位素组成，进一步研究了阿塔卡马沙漠中钙的来源和运输途径。本文对阿塔卡马沙漠最干旱部分的两个案例进行了详细研究，即Tiliviche盆地（- 19.5°S）和quillagua - llamara盆地（- 21.5°S）。硫酸盐样品及其碎屑杂质采用一种新开发的方法，用阴离子交换树脂选择性消化硫酸钙。该方法允许快速溶解硫酸钙样品，而不影响固有的硅塑性材料。所分析的水样在87Sr/86Sr范围为~0.7063 ~ ~0.7075的中等放射性成因范围。化石盐盐ca -sulfate变化较小，范围在~0.7065 ~ ~0.7072之间，而成土样品的ca -sulfate变化较大，范围在~0.7067 ~ ~0.7081之间。与ca -sulfate结合在一起的硅塑性颗粒，其87Sr/86Sr范围从~0.7058到~0.7095。

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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.