Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes

IF 4.5 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochimica et Cosmochimica Acta Pub Date : 2024-10-03 DOI:10.1016/j.gca.2024.09.036

S.E. Brooker , J.D. Barnes , J.C. Lassiter , A. Satkoski , D.G. Pearson

{"title":"Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes","authors":"S.E. Brooker , J.D. Barnes , J.C. Lassiter , A. Satkoski , D.G. Pearson","doi":"10.1016/j.gca.2024.09.036","DOIUrl":null,"url":null,"abstract":"<div><div>Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ18O, δ44/40Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ18O values of olivine (δ18Ool = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ18O values (δ18Ocpx = +5.31 ± 0.10‰; δ18Ogrt = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ44/40Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ44/40Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ18O and high δ44/40Ca values. In general, Δ18Ocpx-ol and Δ18Ogrt-ol (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ18Ogrt and Δ18Ogrt-ol and garnet major and trace element composition (Na2O, H2O, La/YbN). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ18O, δD, and high δ44/40Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"385 ","pages":"Pages 16-33"},"PeriodicalIF":4.5000,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geochimica et Cosmochimica Acta","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0016703724005179","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}

引用次数: 0

Abstract

Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ¹⁸O, δ^44/40Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ¹⁸O values of olivine (δ¹⁸O_ol = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ¹⁸O values (δ¹⁸O_cpx = +5.31 ± 0.10‰; δ¹⁸O_grt = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ^44/40Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ^44/40Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ¹⁸O and high δ^44/40Ca values. In general, Δ¹⁸O_cpx-ol and Δ¹⁸O_grt-ol (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ¹⁸O_grt and Δ¹⁸O_grt-ol and garnet major and trace element composition (Na₂O, H₂O, La/Yb_N). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ¹⁸O, δD, and high δ^44/40Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.

查看原文本刊更多论文

利用钙、氧和氢同位素追踪大陆下岩石圈地幔与俯冲有关的变质作用

地幔异质岩有效地记录了影响大陆岩石圈演化的变质过程，如与俯冲成分的相互作用或通过小度熔融的改变。主要元素/微量元素地球化学与稳定同位素和放射性同位素组成之间的相关性有助于确定这种变质作用的来源和时间。我们报告了来自斯莱弗克拉通（加拿大西北地区）的12块金伯利岩寄生地幔异质岩的δ18O、δ44/40Ca和δD新值，这些异质岩显示了不同程度的变质作用。橄榄石的 δ18O 值（δ18Ool = +5.33 ± 0.13‰；1σ；n = 12）与地幔的平均值相重叠。椭圆辉石和石榴石的δ18O值（δ18Ocpx = +5.31 ± 0.10‰；δ18Ogrt = +5.37 ± 0.23‰；1σ）低于大多数地幔橄榄岩的平均值，并且与椭圆辉石的δ44/40Ca（avg.=+1.00±0.10‰；1σ）和石榴石δ44/40Ca（平均值=+1.18±0.19‰；1σ），分别从典型的地幔值扩展到低δ18O和高δ44/40Ca值。一般来说，Δ18Ocpx-醇和Δ18Ogrt-醇（分别从-0.19‰到+0.19‰和从-0.56‰到+0.35‰）低于地幔温度下的预期平衡值。δ18Ogrt和Δ18Ogrt-ol与石榴石的主要元素和微量元素组成（Na2O、H2O、La/YbN）之间存在强烈的负相关。此外，含辉绿岩的钾长石边缘的δD值（平均 = -126 ± 13‰；1σ）低于典型的地幔值。全岩 Sm-Nd 模型年龄和氧同位素扩散模型表明，变质作用发生在中生代，即金伯利岩夹带前不久，这与来自斯拉夫克拉通的金刚石形成流体的迹象一致。地幔橄榄岩异长岩的低δ18O、δD和高δ44/40Ca综合特征以及年龄约束表明，变质流体/熔体的来源是与北美西部中生代俯冲有关的再循环大洋地壳成分。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

Geochimica et Cosmochimica Acta 地学-地球化学与地球物理

CiteScore

9.60

自引率

14.00%

发文量

437

审稿时长

6 months

期刊介绍： Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.