X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - Gasteiz, Como mineral autigénico predominante, el cemento de calcita tiene un efecto muy significativo en la potencial calidad como reservorio del anticlinal de Puig-Reig, que constituye un excelente análogo para el estudio de la distribución de cementos en diferentes facies sedimentarias gracias a la cantidad y calidad de los afloramientos. Tras un exhaustivo estudio estratigráfico y de recogida muestras, se han realizado análisis petrográficos con microscopio óptico y de cátodo-luminiscencia de facies y sus cementos. Se han identificado dos generaciones principales de cementación calcítica que se desarrollaron durante y después del crecimiento del anticlinal, aunque la mayor parte del cemento cristalizó de manera simultánea a su formación. La distribución del cemento está controlada por la posición estructural dentro del pliegue y por las facies y litofacies de la roca encajante. Los depósitos de canales fluviales en la cresta del anticlinal, de grano especialmente grueso, tienden a desarrollar más cementación. Es necesario profundizar en el estudio de las características de la cementación de calcita para producir mejores estimaciones sobre la calidad de los reservorios y para guiar las actividades de exploración relacionada con los hidrocarburos o el almacenamiento geológico de CO2 en estructuras subterráneas similares., As the most prevalent authigenic mineral, calcite cement exerts a significant effect on reservoir quality of the Puig-reig anticline, which is an excellent outcrop analogue to study calcite cement distribution due to good and continuous exposure. After stratigraphic logging and rock sampling, two major generations of calcite cementation have been identified using petrographic observations under optical and cathodoluminescence microscopes. They formed during and after anticline growth, respectively. Most calcite cement formed simultaneously with the anticline. Calcite cement distribution is controlled by the structural position of sediments in the fold and also by host sedimentary facies and lithofacies. Fluvial channel deposits of the anticline crest, especially relatively coarse deposits, tend to host more calcite cement. A more detailed study on calcite cementation is required to predict high-quality reservoirs and further guide petroleum exploration or carbon storage in similar subsurface structures., Funding was provided by the Grup Consolidat de Recerca “Geologia Sedimentària” (2017SGR-824) and the DGICYT Spanish Project PGC2018-093903-B-C22. XS acknowledges funding by the China Scholarship Council for a PhD scholarship (201806450043). EGR acknowledges funding provided by the Spanish Ministry of Science, Innovation and Universities (“Ramón y Cajal” fellowship RYC2018-026335-I). JA is funded by MICINN (Juan de la Cierva fellowship - IJC2018-036074-I)

X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - Gasteiz, Calcite veins precipitated in the Estamariu thrust during two tectonic events have been investigated in order to
decipher the relationships between deformation and fluid migration in Paleozoic basement rocks. Structural observations
constrain the timing of vein formation and fluid migration, whilst geochemical analyses (¿13C, ¿18O, 87Sr/86Sr and elemental
composition) of the related calcite cements indicate the fluid origin, pathways and extent of fluid-rock interaction. The first
tectonic event, related to the Alpine reactivation of the Estamariu Variscan thrust, is characterized by the upward migration
of fluids derived from the crystalline basement, giving rise to the precipitation of calcite cements Cc1 and Cc2. The second
tectonic event, developed during the Neogene extension, was responsible of the reactivation of the Estamariu thrust and the
development of normal faults and shear fractures in which calcite cements Cc3, Cc4 and Cc5 precipitated. Cc3 and Cc4 precipitated
from meteoric fluids that interacted at depth with basement rocks before upflowing through fault zones and related
structures. Cc5 precipitated from meteoric fluids percolating from the surface through small fractures., This research was funded by the Spanish Projects CGL2015-66335-C2-1-R and PGC2018-093903-B-C22, and by the Grup Consolidat de Recerca “Geologia Sedimentària” (2017-SGR- 824). The PhD research of DM-L is supported by the FPI2016 (BES-2016-077214) Spanish program from MINECO.

Structural analyses of vein and faults related with the growth of the South Pyrenean fold and thrust belt are coupled with the U-Pb ages of fracture-filling calcites compiled in Cruset et al. (2020) and Muñoz-López et al. (2022). Fractures include conjugated vein systems and reverse, strike-slip and normal faults cemented by calcite. The results reveal the orientation of tectonic stresses during the Pyrenean compression and their spatial and temporal evolution since the Late Cretaceous.

Late Cretaceous to late Palaeocene U-Pb dates between 70.6 and 55.3 Ma registered compressional deformation in the inverted Mesozoic salt-related extensional basins corresponding to the Bóixols and Upper Pedraforca thrust sheets. Calculated paleostresses show a predominant N-S direction of tectonic transport, with more pronounced NW-SE directions in the western termination of the Bóixols and in the northern sector of the Upper Pedraforca.

Fracture data and U-Pb ages between 47.9 and 42.3 Ma measured in the Lower Pedraforca thrust sheet reveal N-S and NW-SE directions of tectonic transport during the middle Eocene, similar to those in the Bóixols and Upper Pedraforca thrust units. Contrarily, younger late Eocene to Oligocene U-Pb ages between 36.2 and 28.4 Ma measured in the lowermost Cadí thrust sheet reveal an homogeneous N-S trend during the emplacement of this unit.

Fractures cutting the Bóixols and Upper Pedraforca thrust sheets, and filled with cements yielding U-Pb ages from 48.8 to 25.68 Ma, show the same directions of tectonic transport than those measured for the Late Cretaceous-Paleocene. These Eocene and Oligocene ages also register the post-emplacement deformation of upper tectonic units on top of the Lower Pedraforca, Cadí, Montsec and Serres Marginals lower thrust sheets., This research was funded by the project ALORBE (PIE-CSIC-202030E310), DGICYT Spanish Projects PID2021-122467NB-C22 and PGC2018-093903-B-C22 Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación/Fondo Europeo de Desarrollo Regional, Unión Europea. David Cruset acknowledges the Spanish Ministry of Science and Innovation for the "Juan de la Cierva Formación¿ contract FJC2020-043488-I AEI/10.13039/501100011033.