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

Type Article
Date 2021-04
Language English
Author(s) Motte Geoffrey1, 2, Hoareau Guilhem1, Callot Jean-Paul1, Revillon Sidonie3, Piccoli Francesca4, Calassou Sylvain2, Gaucher Eric C.2
Affiliation(s) 1 : Univ Pau & Pays Adour, UMR5150, LFCR, TOTAL,UPPA E2S, F-64000 Pau, France.
2 : CSTJF, TOTAL, F-64018 Pau, France.
3 : Inst Univ Europeen Mer, SEDISOR, F-29280 Plouzane, France.
4 : Univ Bern, Inst Geol Sci, CH-3012 Bern, Switzerland.
Source Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2021-04 , Vol. 126 , P. 104932 (28p.)
DOI 10.1016/j.marpetgeo.2021.104932
WOS© Times Cited 19
Keyword(s) Carbonate diagenesis, Dolomite, Breccias, Hydrothermalism, U-Pb dating, Hyperextension, Salt tectonics, Jurassic

The Meillon (Callovo-Oxfordian) and Mano (Tithonian) Formations are dolomitized carbonate reservoirs that actively produce oil and gas (Aquitaine Basin, France). In this study, the dolomitization conditions of their counterparts exhumed in the northwestern Pyrenees are detailed using a combination of field observations, petrography, fluid inclusion microthermometry, elemental and isotopic geochemistry, and carbonate U-Pb geochronology. Dolomitization occurred in several stages spanning from the Neocomian (pre-rift) to the Albian (syn-rift, associated with mantle exhumation and active salt tectonics). Both formations were first massively dolomitized in near-surface to shallow burial conditions during the Berriasian-Valanginian, likely triggered by the influx of marine-derived waters. Between the Barremian and the Albian, the Early Cretaceous rifting caused the upward influx of hot fluids associated with the partial to complete recrystallization of the initial dolomites. During the Albian, subsequent dolomites precipitated in both formations as high-temperature (T > 160 degrees C) vein and pore-filling cement. Distinct fluid inclusion chlorinities and rare earth element patterns between the Meillon and Mano Formations point to fluid compartmentalization during this stage. Whereas dolomite cements indicate the involvement of evaporite-derived brines in the Meillon Formation, precipitation was likely related to clay derived water in the Mano Formation. Lastly, a final episode of dolomite cementation occurred only in the vicinity of faults and volcanic intrusions during the Albian when the highest temperatures were recorded in both formations (T > 250 degrees C). These saddle dolomites precipitated from hydrothermal water with a mixture of mantle, crustal-, and evaporite-derived waters channeled by faults and active diapirs. Subsequent quartz and calcite cement precipitation reveals a temperature decrease in a post-rift to inversion setting (post-Cenomanian) and indicates fluid compartmentalization between both formations. This study highlights the major control exerted by rifting, combined with the presence of diapiric salt, on dolomitization, making carbonate platforms of modern salt-rich passive margins potential targets for exploration.

Full Text
File Pages Size Access
28 42 MB Access on demand
15 MB Access on demand
Author's final draft 87 3 MB Open access
Top of the page