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Correlations between fluid composition and deep-seated structural style in the footwall of the Simplon low-angle normal fault, Switzerland

Tim Wawrzyniec, Jane Selverstone and Gary J. Axen
Correlations between fluid composition and deep-seated structural style in the footwall of the Simplon low-angle normal fault, Switzerland
Geology (Boulder) (August 1999) 27 (8): 715-718

Abstract

Structural and fluid-inclusion analyses reveal a correlated change in structural style and fluid composition along strike in footwall mylonites of the Simplon low-angle normal fault of Switzerland. In the south, early postmylonitic structures are semibrittle shears and brittle faults; synkinematic fluid inclusions within the faults contain a carbonic component, whereas those in the shears lack CO (sub 2) . To the north, early postmylonitic structures are extension veins and kinkbands and synkinematic fluid inclusions are aqueous. Entrapment conditions for all fluid inclusions are estimated to be >500 degrees C and >5 kbar. We speculate that different wetting characteristics of carbonic versus aqueous fluids influenced the mechanical behavior of the rocks. Nonwetting carbonic fluids locally increased fluid pressure and induced brittle failure, resulting in development of abundant, closely spaced brittle faults. In areas lacking carbonic fluids, ductile deformation continued to lower pressures and temperatures.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 27
Serial Issue: 8
Title: Correlations between fluid composition and deep-seated structural style in the footwall of the Simplon low-angle normal fault, Switzerland
Affiliation: University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM, United States
Pages: 715-718
Published: 199908
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 1999-055486
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 9959
Illustration Description: illus. incl. geol. sketch map
N46°15'00" - N46°15'00", E08°00'00" - E08°10'00"
Secondary Affiliation: University of California at Los Angeles, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199919
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