Gypsum is a widely used industrial mineral with many applications, most notably in construction. In the extraction of gypsum as a raw material, compositional homogeneity is the main factor affecting the efficiency of the process. A good understanding of the deposit being exploited is paramount for effective planning of the quarrying activity. Currently, this characterization is achieved through drilling, which only provides limited, 1dimensional information. Electrical Resistivity Imaging (ERI) was employed to assess compositional variations and spatial distribution of gypsum units at the Gelsa quarry, located in Zaragoza, NE Spain. The study aimed to characterize different gypsum varieties, including alabastrine macronodular and layered gypsum, based on their resistivity signatures. ERI data were supplemented with targeted micro-Vertical Electrical Soundings (microVES) to obtain bulk resistivity values of the gypsum units with higher definition, which were used as reference points for interpreting the 2D resistivity sections. The findings revealed that while the resistivity of macronodular gypsum conformed to expected values, layered gypsum exhibited lower-than-expected resistivity despite a high gypsum content. This discrepancy was attributed to the complex lithofacies and secondary microcrystalline gypsum present in the layered units. The results were applied to optimize quarry extraction practices, enabling more homogeneous raw material production. Additionally, an exploratory ERI survey identified areas suitable for future quarry development and ruled out locations with insufficient gypsum resources. The integration of ERI with traditional methods enables more targeted and efficient resource management in gypsum quarries.

La arenisca de Roda se corresponde con un delta del Eoceno inferior situado en el margen norte de la cuenca de Graus-Tremp en el antepaís surpirenaico. Se estudia la distribución de los diferentes productos diagenéticos en una secuencia regresivo-transgresiva de escala decamétrica. La parte inferior del cuerpo arenoso contiene nódulos formados por la precipitación de calcita con alto contenido en magnesio (HMC) durante una etapa temprana, que están ausentes en la parte superior de la secuencia. En la parte superior, existe una zona continua cementada por calcita con bajo contenido en magnesio (LMC). El δ18O del cemento de calcita temprano se ha relacionado con el aporte de agua meteórica durante períodos regresivos. Las unidades carbonáticas transgresivas están dominadas por HMC, principalmente en los bioclastos. Aquí, los procesos diagenéticos tempranos son el control fundamental sobre las principales propiedades petrofísicas de las areniscas, en lugar de la arquitectura deposicional primaria. Además, se ha demostrado que la presencia o ausencia de este cemento temprano es básica en el control de procesos diagenéticos posteriores. Todos ellos afectan en gran medida a la calidad del reservorio.

Different and abundant suspended particles, from 10 to 50 μm, have been detected in the waters of an aquifer, observing various periods of fluctuation in the concentration of these particles that in some wells acquire a reddish colour. The morphology and mineralogy of the particles have been characterized by scanning electron microscopy equipped with X-ray detector and by X-ray diffraction. The isotopic composition of the carbonate fraction of the particles and the rocks surrounding the aquifer has been obtained by mass spectrometry. On the other hand, the isotopic composition (δ18O–δ2H and δ18O, δ34S of the sulphate in solution and δ13C DIC), electrical conductivity, Eh, and major ions have been determined in water samples from extraction wells. They are bicarbonate waters, with minor amounts of sulphates, chlorides, and dissolved nitrates. The solid particles are predominantly of authigenic origin (mainly magnesian calcite overgrown by fibrous aragonite cement), structures with diverse morphologies that have in common a high Fe content (spheroidal, filamentous, tubular or pellicular biofilms) and detrital grains (quartz, clays, and other aluminosilicates). The carbonate in solution is controlled by processes of bacterial sulphate reduction and oxidation of organic matter (induced by the accidental leakage of water with glucose subproducts into the aquifer, local anoxia, presence of sulphates and sulphate-reducing bacteria). The increase in water temperature in wells containing suspended particles, bad odours, negative isotopic compositions of carbonate in solution and positive isotopic composition of sulphate, and the decrease in pH detected during periods of precipitation of these particles are related to these processes. The Fe that caused the formation of red precipitates must come from the dissolution of the Fe conduits from a well. The pumping and the incorporation of Cl2O into the water (used to eliminate-oxidize organic matter) caused oxygenation and shift the balance of Fe towards the precipitation of oxides. The organic structures associated with the iron-rich precipitates are indicative of the activity of iron bacteria that caused the mobilization or precipitation of iron according to the redox potential and pH of the water.

Upper Jurassic and Lower Cretaceous limestones and dolostones serve as hydrocarbon reservoirs in the offshore area of NE Spain. Since similar dolomitized rocks crop out in the adjacent onshore Maestrat Basin in the SE Iberian Range, understanding the dolomitization and other diagenetic processes is key to assessing reservoir properties. The Maestrat Basin dolostones crop out as elongated, asymmetric bodies, ranging from tens of centimetres to kilometres in length and up to 150m thick, with a wedge-shaped geometry closely associated with fractures. These dolostones are calcium-rich with low concentrations of Mn, Sr, and Na, but variable Fe, indicating that the replacement of the host limestone was followed by dolomite cement precipitation. Fluid inclusion data suggest that dolomitization took place at temperatures ranging between 70 and 120 degrees C. Such temperatures, together with the high( 87)Sr/Sr-86 ratio and fluid salinity (16 to 23% wt. NaCl equivalent), reveal that the dolomitization process took place in burial conditions, from fluids that were infiltrated and likely interacted with Triassic, Liassic, and basement rocks. Although the exact age of dolomitization is not fully constrained, it is thought to coincide with fault-related dolomitization events of the same type previously described in the Maestrat Basin, likely during the latest Early Cretaceous and/or during the Late Cretaceous, in relation to the post-rift basin stage. Geochemical differences between the depocenters and structural highs may reflect the controls of the Maestrat Basin basin architecture on the composition and distribution of fluids.

The present work aims to reconstruct the paleoenvironments using a multidisciplinary approach including sedimentology, petrography, and geochemistry. These studies were undertaken on the late Paleocene–early Eocene succession of the Sra Ouertane area, Northwestern Tunisia. These deposits are mainly composed of phosphorites interbedded with limestones and marls. Phosphatised coprolites and indeterminate pellets contain a poorly preserved radiolarian assemblage, which can only be differentiated to the genus level. The presence of Calocyclas, Phormocyrtis, Lychnocanium, and Theocorysspp indicates a late Paleocene–early Eocene age. Geochemical study of major (Fe, Si, P, Ti, K) and trace (Zn, Y, Zr, Sr) elements reveals that the phosphorites at the base and top of the studied section, are characterized by high Sr concentration in addition to high P. In contrast, Zr, Ti, Si, and K are more abundant in samples from the middle part of the section. This enrichment of Zr, Ti, and K was favored by an efficient weathering of neighboring hinterlands during humid episodes, which favored the detrital inputs. This humid period was contemporaneous with the warmest global climate event.

Networks of halite veins have been analysed along galleries of the potash Cabanasses mine (Súria anticline, SE Pyrenees). The presence of a shape preferred orientation cross-cut by halite veins suggests that the rocks hosting the veins underwent ductile deformation before fracture formation and healing. The petrographical characteristics of veins and host rocks, as well as the analysis of their bromine content, reveal that the vein-forming fluids likely resulted from pressure-solution and dynamic recrystallisation of the Lower Halite Unit rocks. Fluids at high pressure migrated upwards and were arrested at the Halite-Sylvinite Unit causing fracture formation below the Potash Unit, which acted as a seal and did not experience brittle deformation.

Microfibers (MF) are unfortunately present in natural systems, and characterization of such pollution must be considered as a global health question. We have studied the content in MF in a high salinity spring in the Pyrenees (NE Iberian Peninsula). The salty composition of the water is sourced from fluids circulating in aquifers with Triassic evaporitic units. The water samples are from the spring and from evaporation ponds where the brine is conducted and where it has been historically evaporated to produce Table Salt. Brines have been carefully sampled and filtered following all the necessary requirements to avoid any potential MF additional contamination. We have done a manual counting of the number of fibers and their colors. Unexpectedly, all the analyzed brines have significant contents in MF (nor other anthropic particles are present), which do not correspond to particles of sediment dragged, but to anthropic contamination. The brine from the spring has an average concentration of 50 MF/L, and in evaporation ponds, it increases to 120 MF/L. The colors of the most common MF are black, blue, and white-transparent. Red and green can also be relevant. The origin of these fibers in non-marine brines is totally anthropic and may have originated from: (i) the contamination of the upper aquifer itself that has incorporated these particles into its circuit and (ii) the aerial fall of particles, which is more evident in the evaporation stages. Results suggest that the presence of MF is ubiquitous and are even found in unexpected geological environments and apparently disconnected from anthropic pollution, such as high mountain salt springs. Such fibers are finally incorporated to commercial Table Salts produced in the local non-marine saltworks.

Salt springs in the Pyrenees (NE Iberian Peninsula) are common due to diapirism and dissolution of Triassic evaporite-bearing deposits. Various salty sources from Eastern Pyrenees have been analysed in order to elucidate their accurate chemical and isotopic composition. The study includes trace analyses by means of ICP-OES and ICP-MS, and, sulphate (S–O) and water molecule (H–O) isotope analyses by mass spectrometry. Outcropping Na–Cl rich brines contain B, Li (from 0.17 to 2.43 ppm), Rb, Zn and Mn as main trace elements. The origin of the salty composition is due to fluids circulating through evaporite Keuper facies (Triassic; halite-sulphates, calcium carbonates and clays), as clearly revealed by brine S–O isotope signature. Sulphate molecule has not suffered sulphate reduction, thus evidencing simple rock dissolution. Noticeable lithium content in seawater brines is well known due to the conservative behaviour of such element, which increases during evaporation. Studied salty springs are non-marine in origin, and not clearly related to hydrothermalism or volcanic fluids, which will enrich brines in lithium. The negative H–O and C isotope signatures of water also support this evidence. Thus, Li origin is mainly due to dissolution of Keuper evaporites, both considering Li contained in salt rocks and/or in fluid inclusions. Study of such brines will contribute to a better understanding of Li circulation and storage in non-marine salty springs.

The ongoing energetic transition needs critical raw materials such as lithium or other metals and renewable energies, such as low to mid-enthalpy geothermal energy. Geothermal systems, mostly located near plate boundaries, undergo strong structural controls essentially through crustal faults, also known to drain fluids. Furthermore, dissolved metals in geothermal fluids can be exploited as a byproduct in geothermal plants. In the present, study we define spatial variations in metal content and the structural control along the Vallès Fault, as a field analogue of a passive margin domain. The Vallès Fault is a crustal fault that juxtaposes the Miocene detrital basin infill to a syn- and late-Hercynian granitic basement. With a crustal thermal anomaly, a geothermal gradient > 35 °C/km, several geothermal systems of low enthalpy (< 130 °C at 1 km depth) are closely associated to the Fault. These geothermal systems are revealed by several springs with temperatures ranging from 20 to 75 °C. The present work combines hydrogeochemical, structural and petrological approaches to characterize the architecture and the relative chronology of the fracture networks of the sites of hot springs; and the metal content of thermal waters to reconstruct the spatial evolution of the metal content of the geothermal fluids. From the structural and petrological point of view, three main results are highlighted: (1) the footwall of the Vallès Fault is characterized by a network of polyphase fractures affecting the granite basement and constituting an important network of permeability by fracturing; (2) a thick fault zone with cataclastic to ultracataclastic fault rocks constitutes, a priori, a barrier for fluids circulation; and (3) an arkosic Miocene basin infill, affected by secondary faults, constitutes a very good reservoir. The metal content of hot waters is low but significant to establish differences according to their structural position. Tectonic structures and surrounding lithologies seem to be decisive in water compositions.

Abstract The Central High Atlas of Morocco is a double verging major diapiric province encompassing SW-NE trending salt-related ridges and Lower to Middle Jurassic deposits over synclines (minibasins) in between them. Typically, Pliensbachian and Bajocian platform carbonates flanking diapirs exhibit partial dolomitization in the vicinity of the diapir wall. The interpretation of the diagenetic products and diagenetic evolution of these dolomitized carbonates may be complex due to different fracture patterns, brecciation, fluid pathways, heterogeneities, localized uplift associated with diapiric activity, among others. The present work focuses on the dolomitization affecting Late Aalenian-Bajocian platform carbonates flanking the Tazoult salt wall, localized in the center of the Central High Atlas. Analytical work includes standard microscopy, cathodoluminescence and 𝛅13C–𝛅18O isotopic analyses. A paragenetic sequence is discussed to reconstruct the diagenetic evolution of the flanking platform carbonates. The results highlight the major influence of diapirism and igneous intrusions on the fluid circulation. Moreover, the present work complements a previous work related to the Liassic successions flanking the Tazoult salt wall.

Salt springs in Cambrils del Pirineu (Pyrenees, NE Iberian Peninsula) are related to diapirism of Triassic (Keuper) evaporite-bearing deposits. Such brines, which are close to NaCl saturation, have been used at least since s. XVIII to produce non-marine table salts. The present research aims to study the hydrogeological system in a high salinity spring water from mountain source in the southern Pyrenees using geochemical study of water and its association with local geology. The research includes total conductivity, major anion and element analyses by means of HPLC and ICP-OES and water flow measurements for one-year period. Sampled waters include a salty spring and nine closer freshwater springs. Conductivity of the salt water is close to 44 mS/cm, chloride is about 17

Exposures of lamproitic volcanic rocks have been used to constrain the age of the evaporitic basin-fill in the Fortuna Basin of southern Spain. K/Ar dates initially suggested a Messinian age assignment for these deposits; however, subsequent 40Ar/39Ar dates indicated a Tortonian age, implying the early onset of evaporite formation in the eastern Betic Cordillera, in an event termed the “Tortonian Salinity Crisis”. In this paper, we critically review the published chronology of the key igneous outcrops and provide new 40Ar/39Ar ages, which show that the Cabezos Negros lamproites lie close to the Tortonian-Messinian boundary (c. 7.25 ​Ma). We also provide new paleomagnetic measurements from each of the three lamproitic outcrops (Cabezos Negros, Derramadores, and El Tale), which demonstrate normal magnetic polarity coincident with episodes of volcanic and subvolcanic activity. The presence of peperites and pillow structures indicate that volcanism at Cabezos Negros was coeval with deposition of the lower part of Rambla Salada Gypsum Member. Therefore, the normal polarity identified in this unit should be equivalent to the normal polarity on the Cabezos Negros lamproites. These results indicate that the initial marine restriction and evaporitic deposition of Fortuna Basin occurred more than a million years before the Messinian Salinity Crisis.

LEARNING LANDSLIDE HAZARDS AT THE UNIVERSITY LEVEL BY COMBINING REAL CASE STUDIES, COLLABORATIVE WORK, AND INNOVATIVE TOOLS

Chlorinated solvents occur as dense nonaqueous phase liquid (DNAPL) or as solutes when dissolved in water. They are present in many pollution sites in urban and industrial areas. They are toxic, carcinogenic, and highly recalcitrant in aquifers and aquitards. In the latter case, they migrate by molecular diffusion into the matrix. When aquitards are fractured, chlorinated solvents also penetrate as a free phase through the fractures. The main objective of this study was to analyze the biogeochemical processes occurring inside the matrix surrounding fractures and in the joint-points zones. The broader implications of this objective derive from the fact that, incomplete natural degradation of contaminants in aquitards generates accumulation of daughter products. This causes steep concentration gradients and back-diffusion fluxes between aquitards and high hydraulic conductivity layers. This offers opportunities to develop remediation strategies based, for example, on the coupling of biotic and reactive abiotic processes. The main results showed: 1) Degradation occurred especially in the matrix adjacent to the orthogonal network of fractures and textural heterogeneities, where texture contrasts favored microbial development because these zones constituted ecotones. 2) A dechlorinating bacterium not belonging to the Dehalococcoides genus, namely Propionibacterium acnes, survived under the high concentrations of dissolved perchloroethene (PCE) in contact with the PCE-DNAPL and was able to degrade it to trichloroethene (TCE). Dehalococcoides genus was able to conduct PCE reductive dechlorination at least up to cis-1,2-dichloroethene (cDCE), which shows again the potential of the medium to degrade chloroethenes in aquitards. 3) Degradation of PCE in the matrix resulted from the coupling of reactive abiotic and biotic processes-in the first case, promoted by Fe2+ sorbed to iron oxides, and in the latter case, related to dechlorinating microorganisms. The dechlorination resulting from these coupling processes is slow and limited by the need for an adequate supply of electron donors.

T. Bover-Arnal 1, E. Playà1, T. Calvet1, X. Delclòs1, M. Garcia-Valles1, M. Guinau1, M. Ríos1, N. Roca1, P. Alfonso2, A. Calafat1 1Universitat de Barcelona (SPAIN) 2Universitat Politècnica de Catalunya (SPAIN)

E. Playà1, T. Bover-Arnal 1, A. Calafat1, T. Calvet1, X. Delclòs1, M. Garcia-Valles1, M. Guinau1, M. Ríos1, N. Roca1, P. Alfonso2 1Universitat de Barcelona (SPAIN) 2Universitat Politècnica de Catalunya (SPAIN)