- 1Université Clermont Auvergne, OPGC, Laboratoire Magmas et Volcans, Aubière, France (marine.boulanger@uca.fr)
- 2Géosciences Environnement Toulouse (GET), CNRS UMR 5563 (CNRS/UPS/IRD/CNES), Université de Toulouse, Observatoire Midi‐Pyrénées, Toulouse, France
- 3Department of Earth and Environmental Sciences, University of Pavia, 27100 Pavia, Italy
- 4Department of Earth, Environmental and Life Sciences, University of Genova, 16132 Genova, Italy
- 5Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France
- 6Institut Universitaire de France (IUF), France
- 7Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France
The plutonic lithologies at mid-ocean ridges provide a unique opportunity to investigate processes occurring in igneous reservoirs during oceanic accretion. Mineral modes, textures, microstructures, and in situ geochemistry are valuable tools used to reconstruct the complex differentiation processes within these mush-dominated environments [1]. A wealth of evidence at the crystal scale points to the involvement of melt-mush reactions at various stages of reservoir formation. Yet, melt-mush reactions take place by definition at a local scale, and their significance for melt differentiation at a larger scale is not straightforward. In this contribution, I will present the results of a series of studies that describe the impact of melt-mush reactions in cumulate gabbroic sections from different locations along slow-spreading ridges. The ubiquitous presence of melt-mush reactions at the scale of the entire magmatic units or reservoirs advocates for their significant impact on differentiation. This observation together with microstructural evidence led to the development of an alternative model of cumulate formation for open mush systems that undergo both repetitive melt recharges and melt-mush reactions, a process we call the melt flush [2]. Comparison between different crustal sections reveals the local variability in the reaction regimes (variable assimilation to crystallization ratios), despite the similarity in the reactions impacting the crustal sections. Variable regimes are likely caused by different melt fractions present in the mush during the reactions. Relying on these observations and previous studies, we conclude that the reaction regime is most likely controlled by the melt flux during the formation of the magmatic systems [3]. Such model paves the way for the characterization of past reservoir dynamics, provided a better quantification of “instantaneous” melt-mush reactions is available.
[1] Lissenberg, MacLeod & Bennett, Phil.Trans.R. Soc, 2019. http://dx.doi.org/10.1098/rsta.2018.0014
[2] Boulanger & France, JPet, 2023. https://doi.org/10.1093/petrology/egad005
[3] Boulanger et al., G3, 2024. https://doi.org/10.1029/2023GC011409
How to cite: Boulanger, M., Bakouche, M., Ferrando, C., France, L., Godard, M., Ildefonse, B., Laubier, M., and Médard, E.: Deciphering the plutonic record at mid-ocean ridges: from crystal-scale processes to crustal-scale accretion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16754, https://doi.org/10.5194/egusphere-egu25-16754, 2025.
