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Geoffrey MOTTE

Dolomitization characterization of a carbonate platform in hyper-extended and inverted salt-rich margin context:
Case study from the Western Pyrenean Jurassic carbonate platform

Supervisors:
Jean-Paul Callot and Guilhem Hoareau – Université de Pau et des Pays de l’Adour (UPPA), France
Éric C. Gaucher – Total, CSTJF, Pau

Major Results

The multi-phased dolomitization of the northwestern Pyrenean carbonate platform is mainly controlled by rifting, combined with the presence of diapiric salt.

Abstract

The Western Pyrenean Jurassic carbonate platform, cropping out on the northerwestern Pyrenees foreland, is a remarkable laboratory for the characterization of dolomitization. With a geodynamic evolution at the interface between margin and chain, as well as the presence of the whole carbonate system at the outcrop, the study of this zone allows to apprehend the crucial parameters of the dolomitization and thus to determine which geodynamic and sedimentary contexts are suitable. The combination of field observations, petrographic, elemental, isotopic and microthermometric analyses on fluid inclusions coupled with carbonate U-Pb dating allowed to determine the dolomitization conditions of different localities of this carbonate system cropping out in the Chaînons béarnais and the Basque Country.

The dolomitization of the West Pyrenean platform was primarily controlled by the sedimentary and climatic depositional environment allowing the influx of seawater generating early massive dolomitization. Cretaceous rifting inducing thermal anomalies, combined with the presence of a significant salt layer and salt tectonics represent the second control, inducing massive recrystallization and dolomitic cementations throughout the basin. The stratigraphic architecture of the carbonate system also conditions the distribution of the dolomite with the presence of traces of cement in the distal environment as opposed to the abundance of dolomite observed in the more internal environment. Thus, the distribution of dolomite on carbonate platform on salt-rich hyperthinned passive margin depends essentially on the correlation between the sedimentology of the carbonate system and the paleogeography of the margin.

Simplified geological map of the northwestern Pyrenean zone (modified from Boissonnas et al., 1974; Castéras et al., 1971, 1970 and Le Pochat et al, 1978) with positioning of the dolomitization areas (1, 2, 3 and 4) in the sedimentological context of the carbonate platform and the structural domains of the Cretaceous rift; 2) Schematic models of fluid circulations repositioned on the structural reconstructions of the Chaînons béarnais at the Aptian-Albian and Albian-Santonian time intervals modified according to Labaume and Teixell (2020). The « dolomitizing » diagenetic domains are repositioned along the Cretaceous rifting. The cross-section are located on the map with the white dashed lines.

Rift and salt-related multi-phased dolomitization: example from the northwestern Pyrenees.

Motte, G., Hoareau, G., Callot, J.-P., Révillon, S., Piccoli, F., Calassou, S., Gaucher, E.C., Rift and salt-related multi-phased dolomitization: example from the northwestern Pyrenees, Marine and Petroleum Geology, Volume 126-2021,

keywords: Carbonate diagenesis, Dolomite, Breccias, Hydrothermalism, U–Pb dating, Hyperextension, Salt tectonics, Jurassic

DOI: https://doi.org/10.1016/j.marpetgeo.2021.104932

Direct U-Pb dating of carbonates from micron scale fsLA-ICPMS images using robust regression.

Hoareau, G. Claverie, F., Pecheyran, C., Paroissin, C. Grignard, P-A., Motte, G., Chailan, O., Girard, J-P. Direct U-Pb dating of carbonates from micron scale fsLA-ICPMS images using robust regression. Geochronology, 3, 67–87, 2021

keywords: U-Pb dating, Carbonates

DOI: https://doi.org/10.5194/gchron-3-67-2021

Micro-scale chemical and physical patterns in an interface of hydrothermal dolomitization reveals the governing transport mechanisms in nature: case of the Layens anticline, Pyrenees, France.

Centrella, S., Beaudoin, N.E., Derluyn, H., Motte, G., Lanari, P., Piccoli, F., Pecheyran, C., Callot, J.-P., (2020). Micro-scale chemical and physical patterns in an interface of hydrothermal dolomitization reveals the governing transport mechanisms in nature: case of the Layens anticline, Pyrenees, France. Sedimentology

keywords: Dolomitization, fluid–rock interaction, porosity, replacement, trace element

DOI: https://doi.org/10.1111/sed.12808

Hydrothermal fluid circulations in the western Pyrenees: new data on stable isotopes, in-situ gas analysis and fluid inclusions.

Barré, G., Elias Bahnan, A., Motte, G., Ducoux, M., Hoareau, G., Laurent, D., Gaucher, E.C. (2019) Hydrothermal fluid circulations in the western Pyrenees: new data on stable isotopes, in-situ gas analysis and fluid inclusions. E3S Web. Conf. 98, 4.

keywords: Hydrothermal circulation, Western Pyrenees, H2S

DOI: https://doi:10.1051/e3sconf/20199801001