Fluid evolution at the Variscan front in the vicinity of the Aachen thrust

Détails

ID Serval
serval:BIB_A771F1BB7B09
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Fluid evolution at the Variscan front in the vicinity of the Aachen thrust
Périodique
International Journal of Earth Sciences
Auteur(s)
Sindern S., Meyer F.M., Loegering M.J., Kolb J., Vennemann T.W., Schwarzbauer J.
ISSN-L
1437-3254
Statut éditorial
Publié
Date de publication
2012
Peer-reviewed
Oui
Volume
101
Pages
87-108
Langue
anglais
Résumé
Quartz-carbonate-chlorite veins were studied in borehole samples of the
RWTH-1 well in Aachen. Veins formed in Devonian rocks in the footwall of
the Aachen thrust during Variscan deformation and associated fluid flow.
Primary fluid inclusions indicate subsolvus unmixing of a homogenous
H(2)O-CO(2)-CH(4)-(N(2))-Na-(K)-Cl fluid into a H(2)O-Na-(K)-Cl solution
and a vapour-rich CO(2)-(H(2)O, CH(4), N(2)) fluid. The aqueous
end-member composition resembles that of metamorphic fluids of the
Variscan front zone with salinities ranging from 4 to 7% NaCl equiv.
and maximum homogenisation temperatures of close to 400A degrees C.
Pressure estimates indicate a burial depth between 4,500 and 8,000 m at
geothermal gradients between 50 and 75A degrees C/26 MPa, but pressure
decrease to sublithostatic conditions is also indicated, probably as a
consequence of fracture opening during episodic seismic activity. A
second fluid system, mainly preserved in pseudo-secondary and secondary
fluid inclusions, is characterised by fluid temperatures between 200 and
250A degrees C and salinities of < 5% NaCl equiv. Bulk stable isotope
analyses of fluids released from vein quartz, calcite, and dolomite by
decrepitation yielded delta D(H2O) values from -89 to -113 aEuro
degrees, delta(13)C(CH4) from -26.9 to -28.9aEuro degrees (VPDB) and
delta(13)C(CO2) from -12.8 to -23.3aEuro degrees (VPDB). The low delta D
and delta(13)C range of the fluids is considered to be due to
interaction with cracked hydrocarbons. The second fluid influx caused
partial isotope exchange and disequilibrium. It is envisaged that an
initial short lived flux of hot metamorphic fluids expelled from the
epizonal metamorphic domains of the Stavelot-Venn massif. The
metamorphic fluid was focused along major thrust faults of the Variscan
front zone such as the Aachen thrust. A second fluid influx was
introduced from formation waters in the footwall of the Aachen thrust as
a consequence of progressive deformation. Mixing of the cooler and lower
salinity formation water with the hot metamorphic fluid during episodic
fluid trapping resulted in an evolving range of physicochemical fluid
inclusion characteristics.
Création de la notice
29/09/2012 16:22
Dernière modification de la notice
20/08/2019 15:12
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