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Sill stacking in subseafloor unconsolidated sediments and control on sustained hydrothermal systems: evidence from IODP drilling in the Guaymas Basin, Gulf of California
  • +19
  • Christophe Yann Galerne,
  • Alban Cheviet,
  • Wolf-Achim Kahl,
  • Christin Wiggers,
  • Wolfgang Bach,
  • Florian Neumann,
  • Martine Buatier,
  • Tobias W Höfig,
  • Daniel Lizarralde,
  • Andreas Teske,
  • Manet Peña Salinas,
  • Jens Karstens,
  • Christoph Böttner,
  • Christian Berndt,
  • Ivano W Aiello,
  • Kathleen Marsaglia,
  • Swanne Gontharet,
  • Henning Kuhnert,
  • Joann M. Stock,
  • Raquel Negrete-Aranda,
  • Junli Zhang,
  • Achim J. Kopf
Christophe Yann Galerne
University of Bremen

Corresponding Author:[email protected]

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Alban Cheviet
Université de Franche-Comté
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Wolf-Achim Kahl
University of Bremen
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Christin Wiggers
University of Bremen
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Wolfgang Bach
University of Bremen
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Florian Neumann
GFZ, German Research Centre for Geosciences
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Martine Buatier
UFR Sciences, Universite de Franche Comte
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Tobias W Höfig
International Ocean Discovery Program
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Daniel Lizarralde
Woods Hole Oceanographic Institution
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Andreas Teske
University of North Carolina at Chapel Hill
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Manet Peña Salinas
UABC
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Jens Karstens
GEOMAR Helmholtz Centre for Ocean Research Kiel
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Christoph Böttner
Christian-Albrechts-Universitat zu Kiel
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Christian Berndt
GEOMAR Helmholtz Centre for Ocean Research Kiel
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Ivano W Aiello
Moss Landing Marine Laboratories
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Kathleen Marsaglia
California State University, Northridge
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Swanne Gontharet
Sorbonne Université
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Henning Kuhnert
MARUM - Center for Marine Environmental Sciences, University of Bremen
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Joann M. Stock
California Institute of Technology
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Raquel Negrete-Aranda
Centro de Investigacion Cientifica y de Educacion Superior de Ensenada
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Junli Zhang
University of Bremen
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Achim J. Kopf
University of Bremen
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Abstract

Magma emplacement in the top unconsolidated sediments of rift basins is poorly constrained in terms of mechanics and associated hydrothermal activity. Our study compares two shallow sills from the Guaymas Basin (Gulf of California) using core data and analyses from IODP Expedition 385, and high-resolution 2D seismic data. We show that magma stalling in the top uncemented sediment layer is controlled by the transition from siliceous claystone to uncemented silica-rich sediment, promoting flat sill formation. Space is created through a combination of viscous indentation, magma-sediment mingling and fluidization processes. In low magma input regions, sills form above the opal-A/CT diagenetic barrier, while high magma input leads to upward stacking of sills, forming funnel-shaped intrusions near the seafloor. Our petrophysical, petrographic, and textural analyses show that magma-sediment mingling creates significant porosity (up to 20%) through thermal cracking of the assimilated sediment. Stable isotope data of carbonate precipitates indicate formation temperatures of 70−90°C, consistent with the current background geothermal gradient at 250−325 m depth. The unconsolidated, water-rich host sediments produce little thermogenic gas through contact metamorphism, but deep diagenetically formed gas bypasses the low-permeability top sediments via hydrothermal fluids flowing through the magma plumbing system. This hydrothermal system provides a steady supply of hydrocarbons at temperatures amendable for microbial life, acting as a major microbial incubator. Similar hydrothermal systems are expected to be abundant in magma-rich young rift basins and play a key role in sustaining subseafloor ecosystems.
29 Aug 2024Submitted to ESS Open Archive
29 Aug 2024Published in ESS Open Archive