Xingchao Zhang , Limei Tang , Jianghui Du , Brian A. Haley , James McManus , Xia Hu , Fang Huang
{"title":"现代海水的 Rb 同位素组成及其对深海沉积物的影响","authors":"Xingchao Zhang , Limei Tang , Jianghui Du , Brian A. Haley , James McManus , Xia Hu , Fang Huang","doi":"10.1016/j.epsl.2024.118858","DOIUrl":null,"url":null,"abstract":"<div><p>The rubidium (Rb) isotope system has the potential for tracing water–silicate interactions and providing information on the global Rb cycling. However, the Rb isotope compositions of modern seawater and its major inputs and outputs remain poorly understood. Here we measured Rb isotope compositions of seawaters, pelagic clay sediments and porewaters from the western and central equatorial Pacific Ocean. Our results show that the δ<sup>87</sup>Rb of modern seawater is homogeneous (0.13 ± 0.04‰; 2SD, <em>n</em> = 13) and higher than both the local sediments (-0.17‰ to 0.03‰) and the bulk lithosphere (Δ<sup>87</sup>Rb<sub>seawater-UCC</sub> = 0.27‰). The Rb in pelagic clay sediments is primarily associated with silicates (> 90%) and partially with exchangeable fractions (∼ 4%). The exchangeable fractions display relatively lower δ<sup>87</sup>Rb (-0.07 ± 0.05‰; 2SD, <em>n</em> = 6). Meanwhile, the correlation between K/Rb and δ<sup>87</sup>Rb of bulk sediments, along with investigations on the clay sized particles (δ<sup>87</sup>Rb = -0.06‰), represents that lithogenic silicates have relatively low K/Rb and δ<sup>87</sup>Rb close to the UCC while formation of authigenic phillipsite or clays can result in higher bulk K/Rb (up to 930) and δ<sup>87</sup>Rb (up to 0.03‰). The δ<sup>87</sup>Rb of both authigenic silicates and absorbed fractions in deep–sea sediments are lower than seawater, which can partially contribute to the removal of isotopically light Rb from seawater. The δ<sup>87</sup>Rb of the measured marine porewaters are approximately homogeneous (0.08‰ to 0.14‰) and similar to seawater. The result consistent with previous K isotope investigation in this region with limited impact of authigenic silicates. Using a mass balance estimation in a steady state with isotope data, the flux of sediment removal for Rb in the ocean is about 2.2 – 12.0 × 10<sup>7</sup> kg/year.</p></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The Rb isotope composition of modern seawater and outputs to deep-sea sediments\",\"authors\":\"Xingchao Zhang , Limei Tang , Jianghui Du , Brian A. Haley , James McManus , Xia Hu , Fang Huang\",\"doi\":\"10.1016/j.epsl.2024.118858\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The rubidium (Rb) isotope system has the potential for tracing water–silicate interactions and providing information on the global Rb cycling. However, the Rb isotope compositions of modern seawater and its major inputs and outputs remain poorly understood. Here we measured Rb isotope compositions of seawaters, pelagic clay sediments and porewaters from the western and central equatorial Pacific Ocean. Our results show that the δ<sup>87</sup>Rb of modern seawater is homogeneous (0.13 ± 0.04‰; 2SD, <em>n</em> = 13) and higher than both the local sediments (-0.17‰ to 0.03‰) and the bulk lithosphere (Δ<sup>87</sup>Rb<sub>seawater-UCC</sub> = 0.27‰). The Rb in pelagic clay sediments is primarily associated with silicates (> 90%) and partially with exchangeable fractions (∼ 4%). The exchangeable fractions display relatively lower δ<sup>87</sup>Rb (-0.07 ± 0.05‰; 2SD, <em>n</em> = 6). Meanwhile, the correlation between K/Rb and δ<sup>87</sup>Rb of bulk sediments, along with investigations on the clay sized particles (δ<sup>87</sup>Rb = -0.06‰), represents that lithogenic silicates have relatively low K/Rb and δ<sup>87</sup>Rb close to the UCC while formation of authigenic phillipsite or clays can result in higher bulk K/Rb (up to 930) and δ<sup>87</sup>Rb (up to 0.03‰). The δ<sup>87</sup>Rb of both authigenic silicates and absorbed fractions in deep–sea sediments are lower than seawater, which can partially contribute to the removal of isotopically light Rb from seawater. The δ<sup>87</sup>Rb of the measured marine porewaters are approximately homogeneous (0.08‰ to 0.14‰) and similar to seawater. The result consistent with previous K isotope investigation in this region with limited impact of authigenic silicates. Using a mass balance estimation in a steady state with isotope data, the flux of sediment removal for Rb in the ocean is about 2.2 – 12.0 × 10<sup>7</sup> kg/year.</p></div>\",\"PeriodicalId\":11481,\"journal\":{\"name\":\"Earth and Planetary Science Letters\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":4.8000,\"publicationDate\":\"2024-07-02\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Earth and Planetary Science Letters\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0012821X24002917\",\"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":"Earth and Planetary Science Letters","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012821X24002917","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}
The Rb isotope composition of modern seawater and outputs to deep-sea sediments
The rubidium (Rb) isotope system has the potential for tracing water–silicate interactions and providing information on the global Rb cycling. However, the Rb isotope compositions of modern seawater and its major inputs and outputs remain poorly understood. Here we measured Rb isotope compositions of seawaters, pelagic clay sediments and porewaters from the western and central equatorial Pacific Ocean. Our results show that the δ87Rb of modern seawater is homogeneous (0.13 ± 0.04‰; 2SD, n = 13) and higher than both the local sediments (-0.17‰ to 0.03‰) and the bulk lithosphere (Δ87Rbseawater-UCC = 0.27‰). The Rb in pelagic clay sediments is primarily associated with silicates (> 90%) and partially with exchangeable fractions (∼ 4%). The exchangeable fractions display relatively lower δ87Rb (-0.07 ± 0.05‰; 2SD, n = 6). Meanwhile, the correlation between K/Rb and δ87Rb of bulk sediments, along with investigations on the clay sized particles (δ87Rb = -0.06‰), represents that lithogenic silicates have relatively low K/Rb and δ87Rb close to the UCC while formation of authigenic phillipsite or clays can result in higher bulk K/Rb (up to 930) and δ87Rb (up to 0.03‰). The δ87Rb of both authigenic silicates and absorbed fractions in deep–sea sediments are lower than seawater, which can partially contribute to the removal of isotopically light Rb from seawater. The δ87Rb of the measured marine porewaters are approximately homogeneous (0.08‰ to 0.14‰) and similar to seawater. The result consistent with previous K isotope investigation in this region with limited impact of authigenic silicates. Using a mass balance estimation in a steady state with isotope data, the flux of sediment removal for Rb in the ocean is about 2.2 – 12.0 × 107 kg/year.
期刊介绍:
Earth and Planetary Science Letters (EPSL) is a leading journal for researchers across the entire Earth and planetary sciences community. It publishes concise, exciting, high-impact articles ("Letters") of broad interest. Its focus is on physical and chemical processes, the evolution and general properties of the Earth and planets - from their deep interiors to their atmospheres. EPSL also includes a Frontiers section, featuring invited high-profile synthesis articles by leading experts on timely topics to bring cutting-edge research to the wider community.