Oriented calcite concretions in Upper Miocene carbonate rocks of Menorca, Spain : evidence for fluid flow through a heterogeneous porous system



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.

Full Text:


DOI: https://doi.org/10.1344/105.000001419


  • There are currently no refbacks.

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike License.

            Facultat de Ciències de la Terra                  Institut de Ciències de la Terra                     Institut de Diagnosi Ambiental                    Universitat Autònoma de Barcelona           
                Universitat de Barcelona                            "Jaume Almera" (CSIC)                              i Estudis de l'Aigua (CSIC) 
Geologica Acta (ISSN-1695-6133)
Biblioteca de Ciències de la Terra (UB-CSIC) | Facultat de Ciències de la Terra, Martí i Franquès s/n 08028 Barcelona | Spain
Phone: +34 93 403 19 89 | E-mail: geologica-acta@ictja.csic.es
RCUB revistesub@ub.edu Avís Legal RCUB Universitat de Barcelona