{"title":"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","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 δ<sup>18</sup>O, δ<sup>44/40</sup>Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ<sup>18</sup>O values of olivine (δ<sup>18</sup>O<sub>ol</sub> = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ<sup>18</sup>O values (δ<sup>18</sup>O<sub>cpx</sub> = +5.31 ± 0.10‰; δ<sup>18</sup>O<sub>grt</sub> = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ<sup>44/40</sup>Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ<sup>44/40</sup>Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ<sup>18</sup>O and high δ<sup>44/40</sup>Ca values. In general, Δ<sup>18</sup>O<sub>cpx-ol</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> (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 δ<sup>18</sup>O<sub>grt</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> and garnet major and trace element composition (Na<sub>2</sub>O, H<sub>2</sub>O, La/Yb<sub>N</sub>). 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 δ<sup>18</sup>O, δD, and high δ<sup>44/40</sup>Ca 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":"{\"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 δ<sup>18</sup>O, δ<sup>44/40</sup>Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ<sup>18</sup>O values of olivine (δ<sup>18</sup>O<sub>ol</sub> = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ<sup>18</sup>O values (δ<sup>18</sup>O<sub>cpx</sub> = +5.31 ± 0.10‰; δ<sup>18</sup>O<sub>grt</sub> = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ<sup>44/40</sup>Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ<sup>44/40</sup>Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ<sup>18</sup>O and high δ<sup>44/40</sup>Ca values. In general, Δ<sup>18</sup>O<sub>cpx-ol</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> (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 δ<sup>18</sup>O<sub>grt</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> and garnet major and trace element composition (Na<sub>2</sub>O, H<sub>2</sub>O, La/Yb<sub>N</sub>). 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 δ<sup>18</sup>O, δD, and high δ<sup>44/40</sup>Ca 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}","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}
Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes
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.
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.
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