Understanding Fluid Flow during Tectonic Reactivation: An Example from the Flamborough Head Chalk Outcrop (UK)

Autor: Philippe Muchez, F. Champenois, Michaël Verbiest, E. Lasseur, Rudy Swennen, C. Chaduteau, Cécile Allanic, M. Bonifacie, Sander Wouters, R. Honlet, Ophelie Faÿ-Gomord
Přispěvatelé: Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), TOTAL SA, as part of the 'Fractured Tight Chalk' project, including the Ph.D. of Oph´elie Fa¨y-Gomord. Thanks are due to Nadine Mattiellifrom Universit´e Libre de Bruxelles (ULB) for the strontium isotope analyses.The authors also kindly thank Herman Nijs (KU Leuven) for the preparation of the thin sections and wafers, as well as Elvira Vassilieva (KU Leuven) for hercontribution to the ICP-OES analyses., Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Geofluids
Geofluids, Wiley, 2018, 2018, pp.9352143. ⟨10.1155/2018/9352143⟩
Geofluids, Vol 2018 (2018)
ISSN: 1468-8115
1468-8123
DOI: 10.1155/2018/9352143⟩
Popis: © 2018 O. Fäy-Gomord et al. Flamborough Head chalks are located at the extremities of E-W and N-S trending fault systems along the Yorkshire coast (UK). Rock deformation is expressed in Selwicks Bay where a normal fault is exposed along with a high density of calcite veins.The fault mineralization is tested using geochemistry. Crosscutting relationships are used to differentiate between three vein generations: a network of parallel veins that are oriented perpendicular to stratigraphy (Group I), hydraulic breccia with typical jigsaw puzzle structure (Group II), and a third generation of calcite veins crosscutting the two previous generations (Group III). Geochemical analyses revealed that all three generations possess the same chemical signature and must reflect successive pulses from the same mineralizing fluid source. Strontium isotope analyses showed that the veins have elevated 87Sr/86Sr ratios, that is, up to 7.110, while ratios of the chalk matrix equal 7.707.The latter value is in agreement with the signature of Late Cretaceous seawater. Consequently, the source of the fluid is external, reflecting an open system.The radiogenic Sr-isotope ratios, combinedwith lowiron concentration, suggest that fluids migrated through sandy deposits. Fluid inclusion salinities range from 0 to 12 eq. wt%NaCl equiv. with a dominance of very low salinity inclusions, reflecting a meteoric signal. This leads to a model where meteoric fluids stored in an underlying confined sandstone aquifer were remobilized. The wide range of salinities could result from mixing of the meteoric fluid with some more saline fluids present in the rock sequence or from the dissolution of salts in the subsurface. In addition to the understanding of the local paragenetic evolution of the veining in Flamborough Head chalks, this study offers an insight into the way how fluid flows and mineralizes along fault zones. ispartof: GEOFLUIDS vol:2018 status: published
Databáze: OpenAIRE
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