{"title":"Early stages impact of volcanism on sedimentary diagenesis: The case of the newly born volcano, Fani Maoré","authors":"Marine Manoux , Christophe Rabouille , Jean-Pascal Dumoulin , Bruno Bombled , Gaël Monvoisin , Sandrine Cheron , Audrey Boissier , Yoan Germain , Lucie Pastor , Olivier Rouxel , Cécile Cathalot","doi":"10.1016/j.chemgeo.2025.122674","DOIUrl":null,"url":null,"abstract":"<div><div>Submarine volcanic eruptions impact ocean and sediment geochemistry by generating hydrothermal plumes, fluid expulsion, lava flows, and tephra deposition. The amount and impact of such inputs on the sediment composition and biogeochemistry, on short temporal scales, is yet to be quantified. To this end, the multidisciplinary GEOFLAMME cruise was conducted in May 2021 on board the R/V Pourquoi Pas? to study the Fani Maoré edifice, a newly born volcano located on the eastern submarine flank of Mayotte (Comoros archipelago, Indian Ocean). The strategy was to sample sediment cores along two eastward transects from this volcano towards the open ocean. This study aims for a comprehensive overview of the diagenetic alterations occurring within sediments in response to this volcanic event. Solid phase characterization using X-ray fluorescence and diffraction, particulate organic carbon (POC) content, carbon isotopic signature (δ<sup>13</sup>C-POC; ∆<sup>14</sup>C-POC) and pore water analysis (dissolved inorganic carbon-DIC; Alkalinity; NO<sup>3−</sup> + NO<sup>2−</sup>; SO<sub>4</sub><sup>2−</sup>; dFe; dMn) reveals low organic matter mineralization and low volcanic material alteration throughout the area. However, close to the volcano and lava flows, DIC, alkalinity and Mg<sup>2+</sup> in the sediment show a strong increase at depth while Ca<sup>2+</sup> and Sr<sup>2+</sup> show a strong depletion. We attribute these concentration gradients to the diffusion of a magmatic CO<sub>2</sub>-rich fluid with a geochemical signature reflecting strong fluid-rock interactions as evidenced by carbon isotopic signature of DIC (δ<sup>13</sup>C-DIC; ∆<sup>14</sup>C-DIC) and <sup>87</sup>Sr/<sup>86</sup>Sr ratio followed by carbonate precipitation at depth in the sedimentary pile. This study demonstrated that the interaction between magmatic CO<sub>2</sub> degassing and volcanic rocks leads to natural carbonation at depth, as evidence by vertical profiles that differ from those that can be described in more established volcanic systems. These findings enhance our understanding of the sediment biogeochemistry in a volcanic eruptive context, and offers perspective for a better use and development of new volcanic proxies in marine sediments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122674"},"PeriodicalIF":3.6000,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Chemical Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0009254125000646","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}
引用次数: 0
Abstract
Submarine volcanic eruptions impact ocean and sediment geochemistry by generating hydrothermal plumes, fluid expulsion, lava flows, and tephra deposition. The amount and impact of such inputs on the sediment composition and biogeochemistry, on short temporal scales, is yet to be quantified. To this end, the multidisciplinary GEOFLAMME cruise was conducted in May 2021 on board the R/V Pourquoi Pas? to study the Fani Maoré edifice, a newly born volcano located on the eastern submarine flank of Mayotte (Comoros archipelago, Indian Ocean). The strategy was to sample sediment cores along two eastward transects from this volcano towards the open ocean. This study aims for a comprehensive overview of the diagenetic alterations occurring within sediments in response to this volcanic event. Solid phase characterization using X-ray fluorescence and diffraction, particulate organic carbon (POC) content, carbon isotopic signature (δ13C-POC; ∆14C-POC) and pore water analysis (dissolved inorganic carbon-DIC; Alkalinity; NO3− + NO2−; SO42−; dFe; dMn) reveals low organic matter mineralization and low volcanic material alteration throughout the area. However, close to the volcano and lava flows, DIC, alkalinity and Mg2+ in the sediment show a strong increase at depth while Ca2+ and Sr2+ show a strong depletion. We attribute these concentration gradients to the diffusion of a magmatic CO2-rich fluid with a geochemical signature reflecting strong fluid-rock interactions as evidenced by carbon isotopic signature of DIC (δ13C-DIC; ∆14C-DIC) and 87Sr/86Sr ratio followed by carbonate precipitation at depth in the sedimentary pile. This study demonstrated that the interaction between magmatic CO2 degassing and volcanic rocks leads to natural carbonation at depth, as evidence by vertical profiles that differ from those that can be described in more established volcanic systems. These findings enhance our understanding of the sediment biogeochemistry in a volcanic eruptive context, and offers perspective for a better use and development of new volcanic proxies in marine sediments.
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.