Clays and Clay Minerals, Vol. 55, No. 2, 200–212, 2007.
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Authors
Sindern, Sven
Stanjek, Helge
Hilgers, Christoph
Etoundi, Yvonne
Issue Date
2007
Type
Article
Language
Keywords
Periodicals , Geology , Aachen , Chlorite , CIS , Crystallinity , Fluid Flow , Hydrothermal , Illite , Integral Breadth , Variscan Orogeny , Wurm Syncline
Alternative Title
Short-term Hydrothermal Effects On The ‘crystallinities’ Of Illite And Chlorite In The Footwall Of The Aachen-faille Du Midi Thrust Fault - First Results Of The Rwth-1 Drilling Project
Abstract
Investigation of material from three core sections of the RWTH-1 drill-hole in the Wurm syncline of Aachen, Germany, shows mineralogical and structural evidence of intensive hydrothermal activity in the footwall of the Aachen thrust. Mineral and microstructural data indicate minimum temperatures of 200-250ºC. CISillite 001 values of 0.45-0.61 (Dº2y) and insignificant amounts of smectite indicate a late diagenetic grade for illite pointing to temperatures <200ºC. Chlorite, mainly formed in veins and cleavage planes, has CISchlorite 002 values between0.35 and 0.26 (Dº2y) which only in part point to anchizonal grade. In contrast to these illite and chlorite data, maximum temperatures up to 370ºC can be expected based on comparison with recently published fluid inclusion and mineral thermometric data. Illite is neither significantly affected by the hydrothermal event nor by deformation, and mirrors the burial history of the Wurm syncline. Chlorite grew syntectonically as is shown by bent and predominantly stretched sheets which do not, however, have deformed structures. Syntectonic hydrothermal growth by incipient nucleation along crystal edges limited domains ize and thus also the CISchlorite 002 values. The hydrothermal event did not last long enough to allow further crystal growth. The retarded CISillite and CISchlorite grades canbe best explained by limited duration(probably <5000 y) of the hydrothermal event which for a short time reached epithermal temperatures. The hydrothermal fluid flow was caused by dewatering of sedimentary rocks during thrusting and tectonic thickening within the Variscan orogen and it was focused along the Aachen thrust which represents the frontal Variscan thrust.
Description
Clays and Clay Minerals, Vol. 55, No. 2, 200–212, 2007. Short-term Hydrothermal Effects On The ‘crystallinities’ Of Illite And Chlorite In The Footwall Of The Aachen-faille Du Midi Thrust Fault - First Results Of The Rwth-1 Drilling Project. Sven Sindern; Helge Stanjek; Christoph Hilgers; Yvonne Etoundi. DOI: 10.1346/CCMN.2007.0550209. Copyright © 2007, The Clay Minerals Society.
Citation
Clays and Clay Minerals, Vol. 55, No. 2, 200–212, 2007.
Publisher
The Clay Minerals Society
License
Copyright © 2006-2018, The Clay Minerals Society