Oriented calcite concretions in Upper Miocene carbonate rocks of Menorca, Spain : evidence for fluid flow through a heterogeneous porous system
Pomar Goma, Lluís (Universitat de les Illes Balears. Departament de Ciències de la Terra)
Westphal, H. (Universität Erlangen. Institut für Paläontologie)
Obrador i Tudurí, Antoni (Universitat Autònoma de Barcelona. Departament de Geologia)

Data:	2004
Resum:	Elongate calcite concretions in Upper Miocene dolomitic, shallow-marine grainstones and packstones of Menorca document fluid flow through heterogeneous systems. These post-dolomitization concretions are thought to have grown with elongation axes parallel to groundwater flow direction, and to reflect the hydraulic gradient and the anisotropy of the hydraulic conductivity. Differences in shape, size and orientation of concretions, as well as the spatial and crosscutting relationships reflect two phases of calcite-cementing fluids. This is in contrast to most examples in the literature that distinguish just one phase of precipitating fluids. The first phase of cementing fluids flowed horizontally, most likely in the phreatic zone, across hydraulic high-conductivity layers that resulted from sediment-packing heterogeneities and preferential dissolution during dolomitization. These first-phase fluids were most likely injected into the host rock through fracture zones and probably originated in deeper settings. The second phase of cementing fluids was downward directed and possibly of meteoric origin. First-generation concretions, acting as permeability barriers, partly controlled the fluid pathways, precipitation patterns, and concretion type and loci.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Calcite concretions ; Carbonates ; Fluid flow ; Diagenesis ; Balearic Islands ; Miocene
Publicat a:	Geologica acta, Vol. 2, Núm. 4 (2004) , p. 271-284, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/82208
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/105.000001419
DOI: 10.1344/105.000001419

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