Geochemical Perspectives Letters最新文献

英文中文

Barium isotope evidence for a magmatic fluid-dominated petrogenesis of LCT-type pegmatites 以岩浆流体为主的岩浆岩成岩作用的钡同位素证据

IF 4.9 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochemical Perspectives Letters

Pub Date : 2024-06-28 DOI: 10.7185/geochemlet.2426

G. Deng, D. Jiang, G. Li, Z. Xu, F. Huang

Understanding the petrogenesis of granitic pegmatites associated with Li mineralisation is fundamental in constraining rare metal enrichment mechanisms. However, there is still significant controversy surrounding the central issue of the nature of pegmatite-forming liquids. Here, we report Ba isotope data for a 3000 m borehole in the Jiajika pegmatite field that hosts the largest hard rock-type Li deposit in Asia. The pegmatites exhibit markedly lower δ^138/134Ba than the wall rocks and the average upper continental crust, which cannot be attributed to low degree anatexis of metasedimentary or crystal fractionation of highly evolved granitic magmas. Instead, modelling suggests that their low δ^138/134Ba most likely results from substantial involvement (10–40 %) of isotopically light hydrothermal fluids exsolved from the underlying magmatic reservoirs. In the context of transcrustal magmatic system, these magmatic fluid components may be a key medium in extracting, concentrating, and transporting Li to provide a material source for mineralisation in granitic pegmatites.

了解与锂矿化有关的花岗伟晶岩的岩石成因，对于制约稀有金属富集机制至关重要。然而，围绕伟晶岩成岩液性质这一核心问题仍存在重大争议。在此，我们报告了亚洲最大的硬岩型锂矿床--嘉积嘉伟晶岩矿区一个 3000 米钻孔的钡同位素数据。伟晶岩的δ138/134Ba明显低于壁岩和平均上部大陆地壳，这不能归因于变质岩的低度无性化或高度演化的花岗岩岩浆的晶体分馏。相反，模拟结果表明，它们的低δ138/134Ba 很可能是由于大量（10-40%）同位素轻的热液从底层岩浆储层中流出造成的。在跨地壳岩浆系统中，这些岩浆流体成分可能是萃取、浓缩和运输锂的关键介质，为花岗伟晶岩的成矿提供了物质来源。

引用次数: 0

Subduction of sedimentary carbonate in the Mariana trench 马里亚纳海沟沉积碳酸盐的俯冲作用

IF 4.9 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochemical Perspectives Letters

Pub Date : 2024-06-26 DOI: 10.7185/geochemlet.2425

S. Liu, X. Su, S. Wan, L. Zhang, S. Chen, W. Xu, H. Xu, D. Wang, D. Li, X. Peng

Calcium carbonate is a major component of shallow marine sediments but is rarely preserved in deep sea environments below the calcite compensation depth (CCD). In this study, we present evidence of sedimentary carbonate on the subducting Pacific plate of the Mariana Trench at a water depth ranging from 6675 to 10,813 m, far surpassing the local CCD of 4800 m. These deposits consist of well-preserved calcareous nannofossils, planktonic foraminifera, and siliceous radiolarians. Fossil assemblages and isotope stratigraphy analyses constrain the age of carbonate sediments to 17.6–13.5 Ma. We propose that the calcareous sediments originated from rapid deposition and burial on the seafloor above the CCD during the Miocene. Subsequently, they were transported into the hadal zone with the subduction of the Pacific Plate and exposed due to the excavation of extensive subducting-related normal faults within the subducting plate. This study implies that sedimentary carbonate may be a key component of subducting carbon at the hadal subduction zones, which has important implications for evaluating global carbon input fluxes at these zones.

碳酸钙是浅海沉积物的主要成分，但在方解石补偿深度（CCD）以下的深海环境中却很少保存。在这项研究中，我们展示了马里亚纳海沟太平洋俯冲板块上沉积碳酸盐的证据，其水深从 6675 米到 10813 米不等，远远超过了当地 4800 米的方解石补偿深度（CCD）。化石组合和同位素地层分析将碳酸盐沉积物的年龄推定为 17.6-13.5 Ma。我们认为，钙质沉积物起源于中新世期间CCD上方海底的快速沉积和掩埋。随后，随着太平洋板块的俯冲，它们被搬运到哈达尔区，并由于俯冲板块内部与俯冲相关的大面积正断层的挖掘而暴露出来。这项研究表明，沉积碳酸盐可能是哈达俯冲带俯冲碳的关键组成部分，这对评估这些地带的全球碳输入通量具有重要意义。

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引用次数: 0

Corrigendum to “Sulfur solubility in a deep magma ocean and implications for the deep sulfur cycle” by Steenstra et al., 2022. 对 Steenstra 等人所著 "深岩浆海洋中的硫溶解度及其对深层硫循环的影响 "的更正，2022 年。

IF 4.9 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochemical Perspectives Letters

Pub Date : 2024-06-25 DOI: 10.7185/geochemlet.2219cor

E.S. Steenstra, O.T. Lord, S. Vitale, E.S. Bullock, S. Klemme, M. Walter

Abstract not available

无摘要

引用次数: 0

A baseline for the Sn isotopic composition of the upper continental crust 大陆上地壳锡同位素组成基线

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-30 DOI: 10.7185/geochemlet.2422

E. Kubik, F. Moynier, J.-X. She, R.L. Rudnick

We report high precision Sn isotopic compositions, expressed as δ^122/118Sn relative to the NIST3161a standard, for the fine grained matrix of 24 glacial diamictite composites. The diamictites were deposited from the Mesoarchean to the Palaeozoic and sampled from four continents (Africa, Asia, North and South America). They are relatively homogeneous in δ^122/118Sn, ranging from 0.15 to 0.32 ‰ with an average δ^122/118Sn value of 0.22 ± 0.14 ‰ (2 s.d., n = 24). The Sn isotopic composition of the diamictites is not influenced by chemical weathering, depositional age, geographic setting, atmospheric oxygen content or magmatic differentiation processes in the source region. As such, the average provides a robust estimate of the Sn isotopic composition of the bulk upper continental crust (UCC). This baseline is within the range of, but isotopically lighter than, the current depleted mantle estimate (0.37 ± 0.09 ‰; 2 s.d., n = 12) and bulk silicate Earth (0.38 ± 0.11 ‰; 2 s.d., n = 9). It also overlaps with the very few available measurements made on andesites, granites, a granodiorite and a rhyolite.

我们报告了24种冰川二长岩复合材料细粒基质的高精度锡同位素组成，相对于NIST3161a标准，用δ122/118Sn表示。这些二长岩沉积于中生代至古生代，取样于四大洲（非洲、亚洲、北美洲和南美洲）。它们的δ122/118Sn相对均匀，范围在 0.15 至 0.32 ‰ 之间，平均δ122/118Sn 值为 0.22 ± 0.14 ‰（2 s.d.，n = 24）。二长岩的锡同位素组成不受源区化学风化、沉积年龄、地理环境、大气含氧量或岩浆分异过程的影响。因此，该平均值为大块上大陆地壳（UCC）的锡同位素组成提供了可靠的估计值。该基线在当前贫化地幔估计值（0.37 ± 0.09 ‰；2 s.d.，n = 12）和大块硅酸盐地球（0.38 ± 0.11 ‰；2 s.d.，n = 9）的范围内，但同位素含量比后者轻。它还与对安山岩、花岗岩、花岗闪长岩和流纹岩进行的极少数测量结果重叠。

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引用次数: 0

Neoarchean marine chemical sediments as archives of Hadean silicate differentiation 新元古代海洋化学沉积物作为哈代硅酸盐分化的档案

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-30 DOI: 10.7185/geochemlet.2421

A.N. Wainwright, V. Debaille, J.E. Hoffmann, S. Viehmann, M. Bau

Planetary differentiation had a profound influence on the geochemical signature of the Earth’s silicate reservoirs. Some of the early created complementary reservoirs dissipated with time (e.g., Bennett et al., 2007

Bennett, V.C., Brandon, A.D., Nutman, A.P. (2007) Coupled ¹⁴²Nd-¹⁴³Nd Isotopic Evidence for Hadean Mantle Dynamics. Science 318, 1907–1910. https://doi.org/10.1126/science.1145928

) and only remnants can be observed. Here, we apply the short lived isotopic system ¹⁴⁶Sm-¹⁴²Nd to an alternative archive—marine chemical sediments—and show that alternating Fe- and Si-rich bands from the 2.7 billion-year-old Temagami banded iron formation (BIF), Canada, display significantly different ¹⁴²Nd isotopic compositions. The Fe-rich bands yield a depleted signature (expressed as deviation from the standard in μ notation) with an average μ¹⁴²Nd of +7.02 ± 0.71, while the Si-rich bands display modern mantle-like signatures (average μ¹⁴²Nd −2.83 ± 2.32) likely being the results of mixing between different sources. These complementary signatures reflect the dominant, locally derived source of Nd in the seawater at the time of deposition. Our results promote that layering in BIFs is a syn-depositional feature, and that BIFs are unique geochemical archives capable of recording silicate reservoirs that formed during the Hadean but were still extant during the Neoarchean.

行星分异对地球硅酸盐储层的地球化学特征有着深远的影响。一些早期形成的补充储层随着时间的推移而消散（例如，Bennett 等人，2007Bennett, V.C., Brandon, A.D., Nutman, A.P. (2007) Coupled 142Nd-143Nd Isotopic Evidence for Hadean Mantle Dynamics.Science 318, 1907-1910. https://doi.org/10.1126/science.1145928），只能观测到残余物。在这里，我们将短寿命同位素系统 146Sm-142Nd 应用于另一种档案--海洋化学沉积物--结果表明，加拿大具有 27 亿年历史的 Temagami 带状铁构造（BIF）中富含铁和硅的交替条带显示出明显不同的 142Nd 同位素组成。富铁带显示出贫化特征（用 μ 符号表示与标准的偏差），平均 μ142Nd 为 +7.02 ± 0.71；而富硅带则显示出类似现代地幔的特征（平均 μ142Nd -2.83 ± 2.32），这可能是不同来源之间混合的结果。这些互补特征反映了沉积时海水中钕的主要本地来源。我们的研究结果表明，BIF中的分层是一种同步沉积特征，BIF是一种独特的地球化学档案，能够记录在Hadean时期形成但在Neoarchean时期仍然存在的硅酸盐储层。

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引用次数: 0

Lanthanum anomalies provide constraints on macrofaunal predation at methane seeps 镧异常为甲烷渗漏区大型底栖生物捕食提供了制约因素

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-28 DOI: 10.7185/geochemlet.2420

X. Wang, Z. Jia, J. Peckmann, S. Kiel, J.-A. Barrat, G. Bayon, J. Li, L. Yin, T. Wei, Q. Liang, D. Feng

The feeding habits and predation behaviour of organisms can exert significant control on the dynamics of local food webs. Yet, little is known about the effects of predation on the material and trophic transfer dynamics in chemosynthesis-based ecosystems. Here, we investigated the rare earth element (REE) composition of soft tissues and hardparts for thiotrophy-dependent vesicomyid clams (Archivesica marissinica), aerobic methanotrophy-dependent bathymodiolin mussels (Gigantidas haimaensis), in addition to turrid gastropods (Phymorhynchus buccinoides) and parasitic scale worms (Branchipolynoe pettiboneae) from the Haima seeps of the South China Sea; the latter two species are predators feeding on mussels. Our goal was to determine if the specific, microbially-derived, light REE enrichment characteristics of seep mussels can be transferred to the biomass of their predators. The vesicomyid clams were found to exhibit light REE patterns similar to that of seawater. In contrast, the bathymodiolin mussels, turrid gastropods, and scale worms revealed pronounced lanthanum (La) enrichment, agreeing with substantial transfer of La within the local food web. The observed enrichment of La in seep dwelling predators represents an independent method for monitoring the dynamics within seep ecosystems and potentially for assessing faunal interactions in ancient chemosynthesis-based ecosystems.

生物的摄食习惯和捕食行为可对当地食物网的动态产生重要的控制作用。然而，人们对捕食对以化学合成为基础的生态系统中的物质和营养传递动态的影响知之甚少。在这里，我们研究了中国南海海马渗漏区依赖硫营养的vesicomyid蛤（Archivesica marissinica）、依赖好氧甲烷营养的bathymodiolin贻贝（Gigantidas haimaensis）、腹足类（Phymorhynchus buccinoides）和寄生鳞片蠕虫（Branchipolynoe pettiboneae）的软组织和硬部分的稀土元素（REE）组成；后两个物种是以贻贝为食的捕食者。我们的目标是确定渗漏贻贝特定的、微生物衍生的轻型 REE 富集特征是否可以转移到其捕食者的生物量上。研究发现，膀胱贻贝表现出与海水类似的光 REE 模式。与此相反，水底贻贝、腹足类和鳞片蠕虫则显示出明显的镧（La）富集现象，这与镧在当地食物网中的大量转移是一致的。在渗漏栖息的捕食者体内观察到的 La 富集现象是监测渗漏生态系统内部动态的一种独立方法，有可能用于评估以古化学合成为基础的生态系统中动物的相互作用。

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引用次数: 0

Correlative microspectroscopy of biogenic fabrics in Proterozoic silicified stromatolites 新生代硅化叠层石中生物结构的相关微谱分析

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-13 DOI: 10.7185/geochemlet.2419

K. Hickman-Lewis, B. Cavalazzi, W. Montgomery

Questions surrounding the biogenicity of ancient stromatolites have perplexed geobiologists for decades. Abiotic processes can produce superficially stromatolite-like structures; moreover, stromatolites frequently fail to preserve organic materials and cellular traces of their microbial architects. Using spatially correlated optical and electron microscopy coupled with Raman and FTIR microspectroscopy, we show that silicified stromatolites from the Tonian Skillogalee Dolomite (Flinders Ranges, South Australia) contain exceptionally well preserved microbial mat fragments and microbially induced sedimentary structures. These organic-rich layers exhibit mat-like laminations with low degrees of inheritance and reflect interactions between microbial communities and their environments, i.e. growth, sediment trapping and binding, and reactions to early diagenesis, and are inconsistent with abiotic formation. Although accounting for a minor proportion of the volume of the stromatolites, these kerogenous relics are demonstrably syngenetic and comprise aromatic and aliphatic organic materials, likely preserved due to early and rapid silicification. Constraining the origins of such lamination-scale features can elucidate relationships between morphogenesis and diagenesis and may assist in the resolution of controversies surrounding stromatolite biogenicity in deep time.

几十年来，有关古叠层石生物成因的问题一直困扰着地球生物学家。非生物过程可以产生表面上类似叠层石的结构；此外，叠层石经常无法保存其微生物建筑师的有机材料和细胞痕迹。我们利用空间相关的光学和电子显微镜以及拉曼和傅立叶变换红外显微光谱技术，发现托尼时期斯基洛加里白云岩（南澳大利亚弗林德斯山脉）的硅化叠层石含有保存完好的微生物垫碎片和微生物诱导的沉积结构。这些富含有机质的地层呈现出继承度较低的垫状层理，反映了微生物群落与其环境之间的相互作用，即生长、沉积物捕集和结合以及对早期成岩作用的反应，与非生物形成的情况不符。这些角质遗迹虽然只占叠层石体积的一小部分，但显然是合成的，由芳香族和脂肪族有机物组成，很可能是由于早期快速硅化而保存下来的。对这种层状规模特征的起源进行制约，可以阐明形态发生和成岩作用之间的关系，并有助于解决围绕深部时间叠层石生物成因的争议。

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引用次数: 0

Variable δ11B signatures reflect dynamic evolution of the Mariana serpentinite forearc 不同的δ11B特征反映了马里亚纳蛇绿岩前弧的动态演化

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-03 DOI: 10.7185/geochemlet.2416

E. Cannaò, B. Debret

This study aims to uncover the evolving dynamics of element mobility in serpentinised ultramafic clasts within the Asùt Tesoru mud volcano in the Mariana forearc. By employing in situ analysis of trace elements and boron isotopes (δ¹¹B), our findings document a progressive ¹¹B depletion from lizardite- to antigorite-bearing serpentinites, accompanied by a reduction in the incompatible element inventory in some samples. This pattern aligns with either a chemical evolution linked to phase transitions along the slab interface of shallow forearc serpentinites dragged down to depth, or interaction with shallow vs. deep slab fluids. Our results support a scenario of complex fluid and mechanical mixing along the plate interface in the Mariana subduction system, with major implications for the B recycling in convergent margins.

本研究旨在揭示马里亚纳前弧区 Asùt Tesoru 泥质火山内蛇纹岩化超基性岩碎屑中元素流动的演变动态。通过对痕量元素和硼同位素（δ11B）的现场分析，我们的研究结果记录了从含蜥蜴石到含锑硼的蛇纹岩中 11B 的逐步消耗，同时在一些样品中不相容元素的库存也有所减少。这种模式与沿浅前弧蛇纹岩板块界面相变的化学演变相吻合，或者与浅板块流体和深板块流体的相互作用相吻合。我们的研究结果支持马里亚纳俯冲系统板块界面复杂的流体和机械混合情况，对汇聚边缘的 B 循环具有重要影响。

引用次数: 0

A two stage impact melting process in an impact glass strewn field from the Atacama Desert 阿塔卡马沙漠撞击玻璃散落区的两阶段撞击熔化过程

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-05-03 DOI: 10.7185/geochemlet.2418

P. Rochette, G. Di Vincenzo, J. Gattacceca, J.A. Barrat, B. Devouard, L. Folco, A. Musolino, Y. Quesnel

A new type of silica-rich glass has been discovered associated with the known impact glass strewn field of the Atacama Desert. Based on petrography, chemical composition and indistinguishable ⁴⁰Ar/³⁹Ar formation ages at circa 6.6 Ma, we infer that these two glasses were produced by the same impact event, which gave rise to two successive compositionally different melt batches in close succession. The first one is a silica-rich melt derived from a mixture of quartz sand and weathered magmatic rocks. It is reduced and devoid of extraterrestrial contamination. The second one, much more abundant and which corresponds to the normal glass, is oxidised, highly contaminated by the iron type impactor and derived from an underlying unweathered dacitic rock. This scheme sheds a new light on the first second of the interaction between the Earth surface and a large metallic asteroid.

我们发现了一种新型富含二氧化硅的玻璃，与已知的阿塔卡马沙漠撞击玻璃散落区有关。根据岩相学、化学成分和难以区分的 40Ar/39Ar 形成年龄（约 6.6 Ma），我们推断这两种玻璃是由同一撞击事件产生的，该撞击事件又相继产生了两批成分不同的熔体。第一批是富含二氧化硅的熔体，来自石英砂和风化岩浆岩的混合物。这批熔体已被还原，没有地外污染。第二种熔融物的数量要多得多，与正常玻璃相对应，它被氧化，受到铁型撞击物的高度污染，来自下层未风化的达西特岩。这一方案为地球表面与大型金属小行星之间的第一秒互动提供了新的线索。

引用次数: 0

Direct precipitation of siderite in ferruginous environments 铁矿环境中菱铁矿的直接沉淀

IF 4.9 1区地球科学 Q1 Earth and Planetary Sciences

Geochemical Perspectives Letters

Pub Date : 2024-04-30 DOI: 10.7185/geochemlet.2414

A. Grengs, G. Ledesma, Y. Xiong, S. Katsev, S.W. Poulton, E.D. Swanner, C. Wittkop

Siderite (FeCO₃) is often assumed to precipitate from dissimilatory reduction of Fe-(oxyhydr)oxides, but geochemical and mineralogical analyses from ferruginous (anoxic, Fe-rich) Canyon Lake, USA, suggest Fe-carbonate represents a direct early precipitate unrelated to substantial oxide burial. X-ray absorption near edge structure (XANES) spectroscopy of sediment trap materials and an anoxic sediment core indicated a mixture of Fe(II) and Fe(III) in water column particulates and ferruginous surface sediments, while all Mn phases were reduced. About 60 cm below the sediment–water interface, Fe-Mn carbonates were detected by X-ray diffraction and XANES, while Fe extended X-ray absorption fine structure (EXAFS) spectra were best fit with combinations of a biogenic Fe-oxyhydroxide (“Bio Fe”), greigite, and siderite. Sediment Fe speciation indicates a large pool of reduced Fe with a minor component of oxides. Although we found no evidence of significant carbonate phases above or below the 60 cm horizon, equilibrium modelling indicates siderite supersaturation throughout surface sediment porewater, with pH as the primary control on supersaturation. We conclude that delivery of wildfire ash to sediments increased pH, initiating siderite precipitation from ferruginous porewater.

菱铁矿（FeCO3）通常被认为是由铁（氧氢）氧化物的异纤还原沉淀而成，但对美国峡谷湖（缺氧、富含铁）进行的地球化学和矿物学分析表明，碳酸铁是一种与大量氧化物埋藏无关的早期直接沉淀物。对沉积物捕集材料和缺氧沉积物岩芯进行的 X 射线吸收近缘结构（XANES）光谱分析表明，水柱颗粒和铁锈质表层沉积物中含有铁（II）和铁（III）的混合物，而所有锰相均被还原。在沉积物-水界面下约 60 厘米处，通过 X 射线衍射和 XANES 检测到了铁锰碳酸盐，而铁的扩展 X 射线吸收精细结构（EXAFS）光谱与生物成因的铁氧氢氧化物（"生物铁"）、绿泥石和菱铁矿的组合最为匹配。沉积物中铁的种类表明，沉积物中含有大量还原铁和少量氧化物。虽然我们在 60 厘米地层上下没有发现明显的碳酸盐相，但平衡建模表明菱铁矿在整个表层沉积物孔隙水中处于过饱和状态，pH 值是过饱和的主要控制因素。我们的结论是，野火灰烬向沉积物的输送增加了 pH 值，启动了铁锈色孔隙水的菱铁矿沉淀。

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