Fluid–rock interactions along detachment faults during continental rifting and mantle exhumation: the case of the Urdach lherzolite body (North Pyrenees) - Archive ouverte HAL Access content directly
Journal Articles Journal of the Geological Society Year : 2021

Fluid–rock interactions along detachment faults during continental rifting and mantle exhumation: the case of the Urdach lherzolite body (North Pyrenees)

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Marie-Christine Boiron
Yves Lagabrielle
Michel Cathelineau
Benoit Quesnel
  • Function : Author

Abstract

The North Pyrenean Zone corresponds to the palaeopassive margin of the North Iberia plate, at the foot of which subcontinental mantle was exhumed during Albian times. Rare bodies of exhumed mantle rocks associated with strongly sheared lenses of continental crust are scattered among the North Pyrenean Zone metasediments. Significant fluid flow occurred along a major décollement at the basement–Trias interface in the Urdach massif (Chaînons Béarnais). Fluids with a broad range of salinity (10–38 wt.% NaCl equiv.), indicative of mixing between brines and more dilute waters, produced strong silicification of breccias. The brines circulated at c. 240–280°C under lithostatic pressures at c. 6 ± 1 km depth. The fluids became increasingly saline towards the final stages. The syndeposition of Cenomano-Turonian flysch layers then progressively isolated the lower aquifers close to the décollement where Triassic brines were predominant. The release and migration of significant volumes of brines during stretching and squeezing of the Triassic evaporites played a crucial part in the mineralogical and rheological transformations that occurred during the Pyrenean Cretaceous rifting event.
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Dates and versions

insu-03123590 , version 1 (14-10-2021)

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Jehiel Nteme Mukonzo, Marie-Christine Boiron, Yves Lagabrielle, Michel Cathelineau, Benoit Quesnel. Fluid–rock interactions along detachment faults during continental rifting and mantle exhumation: the case of the Urdach lherzolite body (North Pyrenees). Journal of the Geological Society, 2021, 178 (2), pp.jgs2020-116. ⟨10.1144/jgs2020-116⟩. ⟨insu-03123590⟩
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