{"title":"加拿大东北部 Saglek-Hebron 复合地层岩石中的三重氧和氢同位素对海水与大洋地壳相互作用的制约:中度低δ18O 始新世海洋的含义","authors":"A. Kutyrev , I.N. Bindeman , J. O'Neil , H. Rizo","doi":"10.1016/j.chemgeo.2024.122378","DOIUrl":null,"url":null,"abstract":"<div><p>Estimations of Earth's earliest surface conditions assume a strong connection between the temperature and oxygen isotopic composition of oceans, balanced by surface weathering and submarine hydrothermal alteration. The oldest preserved supracrustal rocks provide rare opportunities to study and constrain the earliest surface conditions prevailing on the Earth. Here, we present a study of triple oxygen and hydrogen isotopes of hydrothermally altered Eoarchean metamorphosed basalts, ultramafic rocks, and detrital and chemical sediments, from the Saglek-Hebron Complex in northern Labrador, Canada. For the metavolcanic rocks, δ’<sup>18</sup>O values range from 4.83 ‰ to 8.56 ‰, while Δ’<sup>17</sup>O values vary from −0.076 ‰ to −0.023 ‰, both higher and lower than the mantle. Accounting for the effects of metamorphism on oxygen and hydrogen isotopic compositions, we demonstrate that triple oxygen isotopic values are preserved from the hydrothermal suboceanic stage, while none of the hydrogen isotope compositions (δD from −77.9 ‰ to −10.7 ‰) are interpreted as primary. Several metabasalt samples from the Saglek-Hebron Complex yielded Δ’<sup>17</sup>Ο values lower than modern mantle values, which cannot be explained by direct interaction with modern seawater and indicate complex upstream interactions. Our numerical models and Monte Carlo simulation considers one- and two-stage mechanisms of water-rock interaction, including the δ’<sup>18</sup>Ο and Δ’<sup>17</sup>Ο isotopic shift effects due to interaction between basalts and chemical sediment-derived fluids. The modelling favors Eoarchean seawater characterized by low δ’<sup>18</sup>Ο < −8 ‰ at Δ’<sup>17</sup>Ο up to 0.01 ‰. This model also works for higher Δ’<sup>17</sup>Ο at lower δ’<sup>18</sup>Ο. Our results also suggest that without proper modelling of multi-stage water-rock interaction, involving isotopic shifts and input of sediment-derived fluids, exposed sections of altered oceanic crust present only remote evidence of the original seawater. Due to the modeled isotopic shifts and fluid mixing, we favor “weak” coupling of seawater-oceanic crust interaction globally. This potentially reduces the relative importance of submarine hydrothermal alteration in explaining the oxygen isotopic record in submarine basalts across the geologic history.</p></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"670 ","pages":"Article 122378"},"PeriodicalIF":3.6000,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0009254124004583/pdfft?md5=f4eb698201950b75266e931f8a896d97&pid=1-s2.0-S0009254124004583-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Seawater-oceanic crust interaction constrained by triple oxygen and hydrogen isotopes in rocks from the Saglek-Hebron complex, NE Canada: Implications for moderately low-δ18O Eoarchean Ocean\",\"authors\":\"A. Kutyrev , I.N. Bindeman , J. O'Neil , H. Rizo\",\"doi\":\"10.1016/j.chemgeo.2024.122378\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Estimations of Earth's earliest surface conditions assume a strong connection between the temperature and oxygen isotopic composition of oceans, balanced by surface weathering and submarine hydrothermal alteration. The oldest preserved supracrustal rocks provide rare opportunities to study and constrain the earliest surface conditions prevailing on the Earth. Here, we present a study of triple oxygen and hydrogen isotopes of hydrothermally altered Eoarchean metamorphosed basalts, ultramafic rocks, and detrital and chemical sediments, from the Saglek-Hebron Complex in northern Labrador, Canada. For the metavolcanic rocks, δ’<sup>18</sup>O values range from 4.83 ‰ to 8.56 ‰, while Δ’<sup>17</sup>O values vary from −0.076 ‰ to −0.023 ‰, both higher and lower than the mantle. Accounting for the effects of metamorphism on oxygen and hydrogen isotopic compositions, we demonstrate that triple oxygen isotopic values are preserved from the hydrothermal suboceanic stage, while none of the hydrogen isotope compositions (δD from −77.9 ‰ to −10.7 ‰) are interpreted as primary. Several metabasalt samples from the Saglek-Hebron Complex yielded Δ’<sup>17</sup>Ο values lower than modern mantle values, which cannot be explained by direct interaction with modern seawater and indicate complex upstream interactions. Our numerical models and Monte Carlo simulation considers one- and two-stage mechanisms of water-rock interaction, including the δ’<sup>18</sup>Ο and Δ’<sup>17</sup>Ο isotopic shift effects due to interaction between basalts and chemical sediment-derived fluids. The modelling favors Eoarchean seawater characterized by low δ’<sup>18</sup>Ο < −8 ‰ at Δ’<sup>17</sup>Ο up to 0.01 ‰. This model also works for higher Δ’<sup>17</sup>Ο at lower δ’<sup>18</sup>Ο. Our results also suggest that without proper modelling of multi-stage water-rock interaction, involving isotopic shifts and input of sediment-derived fluids, exposed sections of altered oceanic crust present only remote evidence of the original seawater. Due to the modeled isotopic shifts and fluid mixing, we favor “weak” coupling of seawater-oceanic crust interaction globally. This potentially reduces the relative importance of submarine hydrothermal alteration in explaining the oxygen isotopic record in submarine basalts across the geologic history.</p></div>\",\"PeriodicalId\":9847,\"journal\":{\"name\":\"Chemical Geology\",\"volume\":\"670 \",\"pages\":\"Article 122378\"},\"PeriodicalIF\":3.6000,\"publicationDate\":\"2024-09-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0009254124004583/pdfft?md5=f4eb698201950b75266e931f8a896d97&pid=1-s2.0-S0009254124004583-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Chemical Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0009254124004583\",\"RegionNum\":2,\"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":"Chemical Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0009254124004583","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Seawater-oceanic crust interaction constrained by triple oxygen and hydrogen isotopes in rocks from the Saglek-Hebron complex, NE Canada: Implications for moderately low-δ18O Eoarchean Ocean
Estimations of Earth's earliest surface conditions assume a strong connection between the temperature and oxygen isotopic composition of oceans, balanced by surface weathering and submarine hydrothermal alteration. The oldest preserved supracrustal rocks provide rare opportunities to study and constrain the earliest surface conditions prevailing on the Earth. Here, we present a study of triple oxygen and hydrogen isotopes of hydrothermally altered Eoarchean metamorphosed basalts, ultramafic rocks, and detrital and chemical sediments, from the Saglek-Hebron Complex in northern Labrador, Canada. For the metavolcanic rocks, δ’18O values range from 4.83 ‰ to 8.56 ‰, while Δ’17O values vary from −0.076 ‰ to −0.023 ‰, both higher and lower than the mantle. Accounting for the effects of metamorphism on oxygen and hydrogen isotopic compositions, we demonstrate that triple oxygen isotopic values are preserved from the hydrothermal suboceanic stage, while none of the hydrogen isotope compositions (δD from −77.9 ‰ to −10.7 ‰) are interpreted as primary. Several metabasalt samples from the Saglek-Hebron Complex yielded Δ’17Ο values lower than modern mantle values, which cannot be explained by direct interaction with modern seawater and indicate complex upstream interactions. Our numerical models and Monte Carlo simulation considers one- and two-stage mechanisms of water-rock interaction, including the δ’18Ο and Δ’17Ο isotopic shift effects due to interaction between basalts and chemical sediment-derived fluids. The modelling favors Eoarchean seawater characterized by low δ’18Ο < −8 ‰ at Δ’17Ο up to 0.01 ‰. This model also works for higher Δ’17Ο at lower δ’18Ο. Our results also suggest that without proper modelling of multi-stage water-rock interaction, involving isotopic shifts and input of sediment-derived fluids, exposed sections of altered oceanic crust present only remote evidence of the original seawater. Due to the modeled isotopic shifts and fluid mixing, we favor “weak” coupling of seawater-oceanic crust interaction globally. This potentially reduces the relative importance of submarine hydrothermal alteration in explaining the oxygen isotopic record in submarine basalts across the geologic history.
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.