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Fault zone architecture and deformation processes within evaporitic rocks in the
upper crust.

De Paola, N.; Collettini, C.; Faulkner, D.R.; Trippetta, F.

Authors

C. Collettini

D.R. Faulkner

F. Trippetta



Abstract

Recently, in the Northern Apennines, geophysical data have identified the Triassic Evaporites (TE, anhydrites and dolomites) as the source region of the major extensional earthquakes of the area (M~6). In order to characterize fault zone architecture and deformation processes within the TE, we have studied exhumed evaporite-bearing normal faults within the upper crust. The structure of large displacement (>100m) normal faults is given by: a) a zoned fault core with a wider portion of fault-parallel foliated Ca-sulphates (ductile deformation), overprinted by an inner fault core (IFC) of localized brittle deformation; b) wide (dolostones) to absent (Ca-sulphates) damage zones of fault fracture patterns. Fault rock assemblage within the IFC is characterized by fault breccia, gouge and cataclasites of different grain size. Most of the deformation within the IFC is localized along thin and fault parallel principal slip surfaces (PSS) made of dolomite rich finegrained cataclasite. SEM analyses show an evolution from Ca- to St- to gypsum-rich mineralization, due to episodic fluid flow events channelled along the fault zones during different stages of fault exhumation. The development of the observed fault geometry can be explained by a mechanical fault evolution model where initial faulting occurs along broad and ductile shear zones within the anhydrites and causes fracturing within the dolostones. Progressive deformation within the fault core leads to the development of fault parallel dolomite rich cataclastic layers. Their reactivation coupled with transient fluid overpressures can produce embrittlement and localization of brittle deformation within the IFC.

Citation

De Paola, N., Collettini, C., Faulkner, D., & Trippetta, F. (2008). upper crust. Tectonics, 27(4), https://doi.org/10.1029/2007tc002230

Journal Article Type Article
Publication Date 2008
Journal Tectonics
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 27
Issue 4
DOI https://doi.org/10.1029/2007tc002230