The antimony isotope composition of Earth's mantle and crust

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-07-10 DOI:10.1016/j.chemgeo.2025.122959

A.B. Kaufmann , S. Weyer , S. Viehmann , F. Marxer , I. Horn , R.L. Rudnick , A. Vymazalová , S. Kiefer , J. Majzlan , M. Lazarov

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引用次数: 0

Abstract

A new ion-exchange chromatography method was developed for the separation of Sb from different matrices to determine the δ¹²³Sb values of the bulk silicate Earth (BSE) and upper continental crust (UCC) relative to NIST SRM 3102a (δ¹²³Sb = [((¹²³Sb/¹²¹Sb)_sample/(¹²³Sb/¹²¹Sb)_{NIST SRM 3102}) - 1] × 1000). Using this method, we analyzed a wide variety of ultramafic to felsic igneous rocks, metamorphic, and sedimentary rocks. Ultramafic and mafic rocks, most closely representing the composition of the depleted upper mantle, display small variations in δ¹²³Sb from −0.11 to 0.11 ‰, yielding a rather homogenous Sb isotopic composition of 0.00 ± 0.04 ‰ (average, 2SE, n = 16). The average δ¹²³Sb value of intermediate and felsic igneous rocks (n = 10) and magmatic sulfides (n = 2) is nearly indistinguishable from that of the depleted upper mantle, indicating insignificant Sb isotope fractionation during formation of the continental crust. The depleted upper mantle may, thus, be considered to represent the BSE. By contrast, greater variability in δ¹²³Sb (−0.28 to 0.52 ‰) is observed for Mesoarchean to Paleozoic glacial diamictite composites, potentially recording the compositional evolution of the UCC. Mesoarchean diamictites tend to have slightly heavier Sb isotopic composition (average δ¹²³Sb = 0.31 ± 0.38 ‰, 2SD, n = 4), though they are within uncertainty of the average values of Paleoproterozoic (0.07 ± 0.46 ‰, 2SD, n = 7), Neoproterozoic (0.01 ± 0.29 ‰, 2SD, n = 9) and Phanerozoic (average 0.00 ± 0.14 ‰, 2SD, n = 3) diamictites. The reason for the large variability of δ¹²³Sb of the Precambrian UCC, as indicated by the diamictites, is uncertain, but may reflect weathering effects, an isotopically heterogeneous early UCC, changing behavior of Sb during crustal differentiation, or a sampling bias (e.g., all of the Archean diamictites are from the Kaapvaal craton). Combining data obtained for the diamictites with those of felsic and intermediate magmatic samples yields a δ¹²³Sb value of 0.07 ± 0.07 ‰ (2SE, n = 33), which provides an estimate for the average UCC. These results provide a framework for investigating the formation of Sb ore deposits, and deep- or near-surface bio-geochemical Sb cycling.

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地幔和地壳的锑同位素组成

建立了从不同基质中分离Sb的离子交换色谱法，测定了硅酸盐土（BSE）和上大陆地壳（UCC）相对于NIST SRM 3102a的δ123Sb值（δ123Sb = [（123Sb/121Sb）样品/(123Sb/121Sb)NIST SRM 3102） - 1] × 1000)。利用这种方法，我们分析了各种超镁铁质至长英质火成岩、变质岩和沉积岩。超镁铁质和基性岩的δ123Sb在- 0.11 ~ 0.11‰范围内变化较小，δ123Sb同位素组成相当均匀，为0.00 ± 0.04‰（平均2SE， n = 16）。中长英质火成岩（n = 10）和岩浆硫化物（n = 2）的平均δ123Sb值与衰竭上地幔的δ123Sb值几乎没有区别，说明大陆地壳形成过程中Sb同位素分块作用不明显。因此，枯竭的上地幔可以被认为代表疯牛病。而中太古宙至古生代冰川辉长岩的δ123Sb变化较大（- 0.28 ~ 0.52‰），可能记录了UCC的组成演化过程。Mesoarchean杂岩往往略重某人同位素组成(平均123某人 δ= 0.31  ± 0.38‰,2 sd, n = 4),尽管他们在古元古代的平均价值的不确定性(0.07 ± 0.46‰,2 sd, n = 7),新元(0.01 ± 0.29‰,2 sd, n = 9)和显生宙(平均0.00 ± 0.14‰,2 sd, n = 3)杂岩。前寒武纪UCC δ123Sb变化大的原因（如二晶岩）是不确定的，但可能反映了风化作用、早期UCC同位素不均匀、地壳分化过程中Sb的变化行为或采样偏差（如所有太古宙二晶岩都来自Kaapvaal克拉通）。结合长英岩和中岩浆样品的δ123Sb值为0.07 ± 0.07‰（2SE, n = 33），给出了平均UCC的估计值。这些结果为研究Sb矿床的形成和深部或近地表生物地球化学Sb循环提供了框架。

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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.