Pore space properties in carbonate fault rocks of peninsular Italy. (January 2020)

• Record Type: Journal Article
• Authors: Ferraro, Francesco; Agosta, Fabrizio; Prasad, Manika; Vinciguerra, Sergio; Violay, Marie; Giorgioni, Maurizio
• Is Part Of: Journal of structural geology. Volume 130(2020)
• Publication Date: 2020-01
• Subjects: Cataclasis -- Diagenesis -- Petrophysical properties -- Ultrasonic tests -- Extensional faults -- Fault permeability.; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2019.103913
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: The fault cores of extensional faults in Mesozoic limestones and dolostones are examined by mean of combined microstructural, ultrasonic and petrophysical analyses. Grain-supported fault rocks commonly localize in the outer fault cores, whereas matrix-supported fault rocks in their inner portions. Cemented fault rocks, if present, surround the main slip surfaces. All dolomite-rich fault rocks, include elongated pores that show a preferential orientation only in the inner fault core. On the contrary, the pore network of calcite-rich fault rocks is made up of elongated pores in the outer fault core, and of sub-spherical pores in the inner fault core. Despite their different pore network characteristics, the petrophysical values of both grain-supported and matrix-supported fault rocks are quite similar one another, with effective porosity up to 10–12%, and permeability up to 2–5 mD. Differently, these values drop down to host rock values, porosity ~5% and permeability ~10 −3 mD, in the cemented fault rocks. Experimental data are discussed to establish, for the first time, the relative control exerted by individual cataclastic and diagenetic processes on the present day pore characteristics, and to decipher the fault core permeability structure at depth. Highlights: Multidisciplinary investigation of outcropping carbonate fault rocks. Pore type and pore geometry assessed for single carbonate fault rock textures. Porosity-permeability trends deciphered for single carbonate fault rock textures. Pore structure as function of deformation mechanisms and diagenetic processes. Conceptual model of pore structure evolution proposed for carbonate fault rocks.