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Cherts originating from carbonate lacustrine environments have been widely exploited by Upper Palaeolithic hunter‐gatherers in the south of the Pyrenees. Archaeo‐petrographic sourcing studies have identified different potential sources but were unable to distinguish them. This study conducted geochemical characterisation of geological and archaeological lacustrine chert samples using laser‐induced breakdown spectroscopy (LIBS), and applied the supervised classification model partial least squares–discriminant analysis to LIBS spectra. The model was able to discriminate geological sources and provide predictions for the origin of a selection of chert artefacts recovered at the Middle Magdalenian level from Cova del Parco (Lleida, Spain). [ABSTRACT FROM AUTHOR]

The post-tectonic and post-orogenic mafic rocks from the Spanish Central System (SCS) (Iberian Massif) include dyke swarms of shoshonitic (microgabbros) and alkaline (lamprophyres and diabases) geochemical affinity, which register the nature of the metasomatic lithospheric mantle under central Spain. Such magmas sometimes show a direct (or indirect) relationship with the formation of orogenic and intrusion-related gold deposits, which are relatively abundant in the Iberian Massif. The noble and base metal composition of these intrusions shows Primitive Mantle-normalized patterns characterized by positive Au and Co anomalies and fractionated platinum group elements (PGE): from lower Ir-group PGE (IPGE; Ir–Ru) to higher Pd-group PGE (PPGE; Rh–Pt–Pd). The low contents of PGE, together with the base metal contents of pyrite (which is the dominant sulphide phase in the alkaline dykes), is in accordance with low degrees of mantle partial melting and the early segregation of sulphides during magma differentiation. The scarcity of PGE mineral deposits in the Iberian Massif could be explained in part by the apparent lack of PGE enrichment in the Iberian lithospheric mantle. On the contrary, the positive Au anomaly of the SCS mafic dykes represents relatively high Au contents, similar to (and higher than) those of mafic rocks derived from metasomatized subcontinental lithospheric mantle underlying Au-endowed cratons. Several geochemical features point to subduction-related metasomatism of either oceanic or continental nature as the main source of Au enrichment. The Au re-fertilization of the lithospheric mantle under central Spain makes it a potential source in the formation of gold mineralizations. [ABSTRACT FROM AUTHOR]

A series of previously unpublished human remains were found at Cueva de la Cocina (Dos Aguas, Valencia, Spain) in excavations from the 1940s and 1970s. Our analyses indicate a minimum of 5 individuals were present in the archaeological deposit, including both adults and children. AMS radiocarbon dating and osteological analysis document ritual defleshing or skinning during the Late Mesolithic, while δ13C and δ15N stable isotope analysis and comparisons to contemporary Mesolithic human remains from the region suggest that these individuals were part of a broader subsistence and cultural network of Holocene hunter-gatherers. Ancient DNA data indicate these late Mesolithic individuals were descendants of a major spread of a new population after a population turnover at the end of the Late Glacial. This research highlights the importance of long-term curation of archaeological finds and revisiting legacy collections. [ABSTRACT FROM AUTHOR]

More than twenty years after the last mining operations were completed in the Hiendelaencina Mining District, it is necessary to carry out a geochemical characterisation of the tailings stored in two contiguous mine ponds. Both have significant amounts of quartz, siderite, barite and muscovite and show significant contents of As, Ba, Pb, Sb and Zn. The tailings show alkaline pH and low electrical conductivity values, which support the visual observation that rules out acid drainage into the environment. The comparison of the National Topographic Map of 1954 with LiDAR data from 2014 has allowed estimating the volume of abandoned waste. Based on the volume of slurry and its average density, the total tonnage of pollutants has been estimated at 279 ± 9 t stored in Pond North and 466 ± 11 t stored in Pond South. Although these are significant quantities that pose a risk to the environment and nearby populations, they are lower than those present in other Spanish districts, such as the Iberian Pyrite Belt or Cartagena-La Unión. The combined use of LiDAR data, aerial imagery and geochemical methods has proven to be very useful for the estimation of the volume of pollutants stored in mine ponds. [ABSTRACT FROM AUTHOR]

Salt efflorescences from metal sulphides and their waste are important drivers of pollution both in and around mining areas. However, little is known about these supergene minerals, particularly in the mining areas of the Mediterranean. This study aims to characterise saline efflorescences and their leachates from a Mediterranean mining area located in Southeast Spain. The physicochemical characteristics were determined using stereomicroscopy and compositional analysis, with the following techniques: XRD, WDXRF and TG-MS. Additionally, to assess the risk and potential mobility of their analytes, the samples were subjected to the leaching test DIN 38414-S4. The results showed that the salt efflorescences presented a wide range of crystalline habits and colours. Sulphates were by far the largest mineral group, followed by silicates, oxides and sulphides. Their geochemistry was dominated by elements such as S or Fe, although other potentially toxic elements such as Cd, As, Zn, Pb, Ni and Cu were also present. Due to their high metal(loid) concentrations, the salt crusts studied may act as sources of environmental contaminants, demonstrating that their leachates pose a considerable risk to soil and drinking water quality. An analysis of the correlations and provenances of the components of the salt efflorescences revealed the possible presence of some rare supergene minerals of great interest, such as cuprocopiapite and Pb-As-jarosite. [ABSTRACT FROM AUTHOR]

The city of Avilés is one of the most industrialized cities in the north of Spain and, accordingly, its estuary and coastal area have been subjected to great anthropic impacts in the last 100 years. This research attempts to establish a preliminary scenario of the geochemical and environmental status of both coastal and estuarine sediments in this area. For this study, a total of 96 sediment samples were collected, processed and analyzed to quantify the granulometric distribution of the sediments, as well as their concentrations of organic carbon and main metal(oids) that may cause an environmental risk. The results show that the estuarine sediments present important concentrations of Cd, Hg, Pb and Zn that allow them to be clearly differentiated from the coastal sediments; this information, along with the sedimentology, implies that the estuary acts as a sink of pollution and not as source to the coastal area. Inside the estuary, the high levels of contamination produce a significant potential ecological risk due to contaminant transfers to other environmental compartments and to the biota. Although direct discharges of industrial effluents have been gradually eliminated, the current state of the sediment requires the implementation of measures that are more consistent than natural regeneration in order to ensure low risk levels for the ecosystem. [ABSTRACT FROM AUTHOR]

Hypersaline lakes are sensitive and increasingly threatened ecological and depositional environments that are host to a diverse spectrum of industrial services, natural resources, and environmental processes. Furthermore, they are also important repositories of high-resolution palaeoenvironmental information and are potentially key archives in the reconstruction of environmental, climatic conditions and past human impacts in areas where other such repositories may not be available. Many saline lakes are threatened by increased farming and irrigation practices and the effects of global warming. Geochemical XRF analyses of a transect of sediment cores from Laguna Salada de Chiprana, a permanent hypersaline lake in the Iberian Peninsula, provide insights into geochemical processes and palaeoenvironmental changes occurring at the site throughout the last 300–400 years. Key changes identified within the sequence are defined both from a spatial and temporal aspect and characterise the profundal and littoral sub-environments of the lake. Initially, the onset of a phase of widespread agriculture and irrigation in the region occurred in the late 16–17th century to ~1850AD and was associated with relative increases in lake levels. This was followed by decreasing lake levels between 1850 and 1950AD, likely associated with increasing evaporative processes and decreased irrigation returns to the lake, which also allowed for increased organic productivity in the profundal setting. This may have been associated with the transition of the site to a wetland-type setting, where biological processes were able to flourish in the shallower central depocentres of the lake. In sequence, the introduction of farm machinery and changing irrigation patterns occurred around 1950, causing small increases in lake levels, colonization by charophytes as well as increased organic productivity in the littoral setting, likely due to the establishment of suitable environments for biological processes to occur in the shallower margins of the lake when water levels rose. From this period to the present day, slow drawdown of the lake has occurred coupled with increasing management of the site by the regional government, leading to several phenomena. Evaporative processes are high throughout the lake; there are falling but highly variable water levels and there is a segmentation of organic productivity, whereby falling lake levels permit increased organic productivity in the profundal setting but decrease productivity in the littoral setting due to the establishment of harsh evaporitic and erosive conditions in this area. The reconstruction reveals the high sensitivity of Lake Chiprana as an environmental archive and illustrates the need to utilise multiple sediment cores for accurate palaeoenvironmental reconstructions of saline lakes due to the strong variability in depositional and geochemical sub-environments. [ABSTRACT FROM AUTHOR]

The geochemistry of the Ría de Huelva estuary (Spain) has been widely studied owing to its unique conditions due to mixing of acid mine drainage (AMD), river water and seawater, which have been aggravated by the existence of an adjacent phosphate fertilizer plant and its associated phosphogypsum stack. To better understand the complex geochemistry of the overall estuarine system, we make use of (1) measured concentrations of relevant trace elements (rare earth elements (REEs) and metal(loid)s) in the sediments and waters of the estuary and (2) geochemical modeling which combines mixing and adsorption processes. Our study sheds light on the elemental distribution in the sediments and water in the water-mixing area. As seawater neutralizes the acidity of the river water (pH increases to 6.2) colloids of Fe- and Al-oxyhydroxysulphates (schwertmannite and basaluminite, respectively) precipitate as concentrations of aqueous Fe and Al increase. These phases have a high adsorption capacity and play a critical role in the geochemistry of the aquatic system by retaining Cu, Pb, Cr, As, P, REEs and smaller amounts of Zn, Co, Ni and Mn. The geochemical model reproduces the behaviour of the aqueous REEs, requiring high S/L ratios at pH ≥ 3.5 and participation of sediments and colloids in the reactions to match the field data. The evaluation of the effect of the adjacent phosphogypsum stack on the estuarine geochemistry shows that the stack has a notorious impact on the geochemistry of the surrounding estuarine environment owing to the release of high quantities of phosphate. [ABSTRACT FROM AUTHOR]

The Tinto and Odiel rivers (SW Spain) drain from a vast sulfide mining district and join at a 20-km-long estuary that enters the Atlantic Ocean. In this work, the contents of rare earth elements (REE) and fractionation in Neogene–Holocene sediment cores from La Fontanilla cove (Tinto estuary) were studied. The sediments were collected from a depth of 18 m at different distances from the recent river flow and were analyzed for new information on the temporal development of the REE load in the sediment column. Results show that the ∑ REE is higher in the finer sediments and during periods of mining activity from prehistoric to recent times. Marine influence appears to increase the light REE (LREE) relative to the heavy REE (HREE). The REE patterns of these estuarine sediments show convex curvatures in the MREE relative to the LREE and HREE, indicating the presence of acid-mixing processes between the fluvial waters affected by acid mine drainage (AMD) and seawater, as well as the precipitation of poorly crystalline mineral phases. Significant positive Eu anomalies were found in ebb-tide channels and marsh deposits, which can reflect the mineralogical composition and/or a strong localized salinity gradient combined with organic matter degradation. Sedimentological characteristics of the deposits appear to play the main role in accumulation and fractionation of the REE. [ABSTRACT FROM AUTHOR]

Belemnites were a type of cephalopod abundant in the Jurassic and Cretaceous, whose fossils have been extensively used for paleo-oceanographic studies. For this study, we analyzed 69 elements by Inductively Coupled Plasma-Sector Field Mass Spectrometry (ICP-SFMS) in 15 belemnite rostra from the West Rodiles section in the Asturian Basin, Northern Spain. We aim to determine if belemnite rostra carbonate chemistry reflects changes in seawater chemistry during the Late Pliensbachian–Early Toarcian time interval and examine how belemnites can be used to trace known drivers of the Early Toarcian Oceanic Anoxic Event (T-OAE) and associated oceanographic processes. Discarding drastic intra-species effects and assuming a similar influence of growth rates, diet, and other physiological processes for all analyzed belemnite specimens and taking into consideration the sizeable analytical uncertainty, we assess if determined belemnite rostra element chemistry reflects broad and relative changes in paleo-seawater chemistry. Many determined elements are present in only ppb amounts, and their interpretation is uncertain. We found that Mg, Mn, and P increase in the interval chronocorrelative to the T-OAE. This is interpreted to have resulted from an increase in these elements' inventory in seawater due to an increase in continental weathering and fluvial runoff associated with this global event. Iron, K, and Na contents decrease upwards in the section, potentially indicating that these elements became limited and likely hampered oceanic productivity. Our study also found a correspondence between a change in the behaviour of several elements, warming, the T-OAE negative CIE, and a reduction in the diversity and size of both calcareous nannofossils and belemnites in the study area. • We study Early Toarcian seawater chemistry and T-OAE drivers. • 69 elements in 15 Spain belemnites rostra were analyzed. • Mg, Mn, and P rose due to weathering. • Fe, K, and Na declined, impacting ocean productivity and reducing nannofossil size. [ABSTRACT FROM AUTHOR]

The Gréixer Rhyolitic Complex is one of the most important manifestations of the post-Variscan Permo-Carboniferous volcanism of the Catalan Pyrenees. This volcanic complex is represented by a > 800 m thick, > 12 km wide, intra-caldera succession, mostly composed of strongly-welded, lava-like rheomorphic rhyolitic pyroclastic rocks. Previous studies have attributed a Lower Permian age to this caldera complex and interpreted it as having resulted from the gravitational collapse of a central volcanic edifice after a large-volume explosive event, mostly represented by widespread extra-caldera pyroclastic deposits (the Castellar de n'Hug Ignimbritic Member), which was radially emplaced from the caldera structure. However, new stratigraphic, structural, geochemical, and geochronological data reveal that this co-genetic relationship between the inferred intra- and extra-caldera deposits does not exist. On the contrary, each of these two successions of pyroclastic deposits resulted from a different volcanic event, which had occurred within a time span of 15 Ma. Moreover, the geochemical signature of these volcanic rocks shows a different magma source for each case, with a clear crustal origin for the Gréixer Rhyolitic Complex and a mixed mantle-crustal origin for the Castellar de n'Hug Ignimbrite Member. The apparent stratigraphic correlation between both successions is the result of the Alpine tectonics, which put together different late and post-Variscan Permo-Carboniferous rocks that had originated in different areas and at different times. • The Gréixer Rhyolitic Complex is distinctive geological element of the Pyrenees. • It corresponds to a rheomorphic rhyolitic pyroclastic rocks intra-caldera succession. • U-Th dating gave a Stephanian C age (303 Ma years, Gzhelian) for these rhyolitic rocks. • The Gréixer Rhyolitic Complex has a clear crustal signature. [ABSTRACT FROM AUTHOR]

The Reocín mine is located in Cantabrian region, in northern Spain. Its exploitation ended in 2003 due to the exhaustion of its reserves. In November 2004, the controlled flooding of the openpit began. During this process, both the qualities of stored water and piezometric levels have been monitored to control the possible water detraction from the Saja-Besaya hydrographic system. This paper deals with the water chemistry analysis of the pit lake surface, as well as the different conditions of the area. Geological and hydrogeological contexts play an important role in the lake water chemistry. The lake water quality continues improving. The sulphate content and zinc concentrations are already below the permitted pouring limits. Three factors are distinguished: the washing of the mine shafts is completed; the water supply from the aquifer contributes to the dissolution of the salt content and the bedrock, and dolomite, which neutralizes acid waters and improves the water quality during the flooding process with a pH value of 8. Owing to these conditions, the stored water meets the necessary conditions for discharge and provides the opportunities to use it. [ABSTRACT FROM AUTHOR]

Despite the paleontological relevance of the terrestrial Early Pleistocene Venta Micena bonebed (Baza Basin, Spain), it lacks a comprehensive geochemical/sedimentological study. Here, we demonstrate that the 1.5-m-thick Venta Micena limestone formed in a relatively small freshwater wetland/pond located at the periphery of the large saline Baza paleolake. Two microfacies are observed, with high and low contents of invertebrate fossils, and which originated in the centre and margin of the wetland, respectively. X-ray diffraction (XRD) mineralogy and paleohydrological characterization based on ostracod and bulk-rock geochemistry (δ13C and δ18O) indicate that the limestone reflects a general lowstand of the Baza lake, permitting the differentiation of freshwater wetlands that were fed by adjacent sources. Conversely, during highstands, the Baza lake flooded the Venta Micena area and the freshwater fauna was replaced by a saline one. Bulk-rock isotopic data indicate that the lower interval C1 of the limestone (bone-rich in marginal settings) displays general negative values, while the upper interval C2 (bone free) displays less negative values. The bones of predated mammals accumulated in the marginal areas, which were flooded and buried by recurring water-table fluctuations. Lake dynamics played a critical role in bone accumulation, which was previously considered as representing a hyena den. [ABSTRACT FROM AUTHOR]

The Sobrado unit, within the upper part of the Órdenes Complex (NW Spain) represents an allochthonous tectonic slice of exhumed high-grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. In order to constrain those processes, U–Pb geochronology and rare-earth element (REE) analyses of accessory minerals in migmatitic paragneiss (monazite, zircon) and mylonitic amphibolites (titanite) were conducted using laser ablation split stream inductively coupled plasma mass spectrometry (LASS-ICP-MS). The youngest metamorphic zircon age obtained coincides with a Middle Devonian concordia monazite age (∼380 Ma) and is interpreted to represent the minimum age of the Sobrado high-P granulite facies metamorphism that occurred during the early stages of the Variscan orogeny. Metamorphic titanite from the mylonitic amphibolites yield a Late Devonian age (∼365 Ma) and track the progressive exhumation of the Sobrado unit. In zircon, cathodoluminescence images and REE analyses allow two aliquots with different origins in the paragneiss to be distinguished. An Early Ordovician age (∼490 Ma) was obtained for metamorphic zircons, although with a large dispersion, related to the evolution of the rock. This age is considered to mark the onset of granulite facies metamorphism in the Sobrado unit under intermediate-P conditions, and related to intrusive magmatism and coeval burial in a magmatic arc setting. A maximum depositional age for the Sobrado unit is established in the late Cambrian (∼511 Ma). The zircon dataset also record several inherited populations. The youngest cogenetic set of zircons yields crystallization ages of 546 and 526 Ma which are thought to be related to the peri-Gondwanan magmatic arc. The additional presence of inherited zircons older than 1000 Ma is interpreted as suggesting a West African Craton provenance. [ABSTRACT FROM AUTHOR]

To understand abandonment processes and secondary uses of public buildings is a key‐challenge to recognize the scope of the urban transformations in Roman cities during Late Antiquity. In this sense, administrative and religious public spaces such as the fora underwent a great variety of transformations resulting in the genesis of a complex stratigraphy of anthropogenic and natural deposits. Baelo Claudia is a well‐known Roman city located in the Atlantic coast of southern Spain. Recent excavations in the forum have provided new data that elucidate Late Roman urban transformations. In this study, we use archaeological soil micromorphology, physico‐chemical analyses and geochemistry to investigate site formation processes and to document nontraditional forms of occupation not visible in the macroscopic archaeological record. This methodology allowed for the distinction of several anthropogenic activities such as glass recycling, reflooring practices, plundering of ornamental marbles, middening of organic and penning residues, together with the progressive decay of earth‐based constructions. The complex superposition of site formation processes seen at Baelo Claudia underlines the role of micromorphology in the identification of behavioral signatures and its relevance in deciphering urban transformation in Late Antiquity. [ABSTRACT FROM AUTHOR]

Early marine diagenetic dolomite is a rather thermodynamically‐stable carbonate phase and has potential to act as an archive of marine porewater properties. However, the variety of early to late diagenetic dolomite phases that can coexist within a single sample can result in extensive complexity. Here, the archive potential of early marine dolomites exposed to extreme post‐depositional processes is tested using various types of analyses, including: petrography, fluid inclusion data, stable δ13C and δ18O isotopes, 87Sr/86Sr ratios, and U‐Pb age dating of various dolomite phases. In this example, a Triassic carbonate platform was dissected and overprinted (diagenetic temperatures of 50 to 430°C) in a strike‐slip zone in Southern Spain. Eight episodes of dolomitization, a dolostone cataclasite and late stage meteoric/vadose cementation were recognized. The following processes were found to be diagenetically relevant: (i) protolith deposition and fabric‐preservation, and marine dolomitization of precursor aragonite and calcite during the Middle–Late Triassic; (ii) intermediate burial and formation of zebra saddle dolomite and precipitation of various dolomite cements in a Proto‐Atlantic opening stress regime (T ca 250°C) during the Early–Middle Jurassic; (iii) dolomite cement precipitation during early Alpine tectonism, rapid burial to ca 15 km, and high‐grade anchizone overprint during Alpine tectonic evolution in the Early Eocene to Early Miocene; (iv) brecciation of dolostones to cataclasite during the onset of the Carboneras Fault Zone activity during the Middle Miocene; and (v) late‐stage regression and subsequent meteoric overprint. Data shown here document that, under favourable conditions, early diagenetic marine dolomites and their archive data may resist petrographic and geochemical resetting over time intervals of 108 or more years. Evidence for this preservation includes preserved Late Triassic seawater δ13CDIC values and primary fluid inclusion data. Data also indicate that oversimplified statements based on bulk data from other petrographically‐complex dolomite archives must be considered with caution. [ABSTRACT FROM AUTHOR]

Mollusc shell stable isotopes are commonly used to reconstruct past environmental conditions. However, despite being abundant components of natural and anthropogenic fossil accumulations, the geochemical composition of mussel shells (Mytilus spp.) has rarely received attention in palaeoenvironmental studies. This study tests the suitability of oxygen isotopes (δ18Os) of Mytilus galloprovincialis as palaeothermometer. For 1 year, mussels and water samples were collected twice a month from Berria Beach, in Northern Spain. The geochemical data of the shells indicate that water temperatures can be reconstructed with an average offset of 1.2 ± 0.7°C with respect to the measured values. Furthermore, no prolonged shell growth cessations are observed. These results validate M. galloprovincialis as reliable recorders of seasonal water temperature fluctuations, supporting their use in palaeoenvironmental studies. In addition, further shell and water collections were carried out in the upper and lower areas of a nearby estuary. The geochemical analyses of these shells were aimed to test whether oxygen and carbon stable isotopes (δ13Cs) may be used as novel proxies to identify the shell provenance at local scale. The results show that the δ18Os versus δ13Cs correlation direction varies along the coast–upper estuary geographical gradient, suggesting it to be a potential new proxy to distinguish between marine and estuarine mussel specimens. [ABSTRACT FROM AUTHOR]

The traditional pottery industry was an important activity in Catalonia (NE Spain) up to the 20th century. However, nowadays only few workshops persist in small villages were the activity is promoted as a touristic attraction. The preservation and promotion of traditional pottery in Catalonia is part of an ongoing strategy of tourism diversification that is revitalizing the sector. The production of authenticable local pottery handicrafts aims at attracting cultivated and high-purchasing power tourists. The present paper inspects several approaches to set up a scientific protocol based on the chemical composition of both raw materials and pottery. These could be used to develop a seal of quality and provenance to regulate the sector. Six Catalan villages with a renowned tradition of local pottery production have been selected. The chemical composition of their clays and the corresponding fired products has been obtained by Energy dispersive X-ray fluorescence (EDXRF). Using the obtained geochemical dataset, a number of unsupervised and supervised machine learning methods have been applied to test their applicability to define geochemical fingerprints that could allow inter-site discrimination. The unsupervised approach fails to distinguish samples from different provenances. These methods are only roughly able to divide the different provenances in two large groups defined by their different SiO2 and CaCO3 concentrations. In contrast, almost all the tested supervised methods allow inter-site discrimination with accuracy levels above 80%, and accuracies above 85% were obtained using a meta-model combining all the predictive supervised methods. The obtained results can be taken as encouraging and demonstrative of the potential of the supervised approach as a way to define geochemical fingerprints to track or attest the provenance of samples. [ABSTRACT FROM AUTHOR]

Advanced microscopy analyses are capable of revealing particles that are existent in the Alhambra, Spain, a UNESCO World Heritage Site, at minimal levels owing to the detailed directing on ultra-fine (UFPs) and nano-particles (NPs) of importance. This applied technique is one of the most used to natural samples. Between the diverse archaeological places in the planet, Alhambra is one of the most important representations of Hispano-Islamic architecture and art significant Muslim virtuosity in its conclusive European periods, thus helping to offer scientific material about the still little studied Islamic art. In this study, advanced microscopy analyses—has been applied to understand minor portions of UFPs and NPs of pollutants in external walls exposed to weathering. Several materials identified by X-Ray Diffraction can be detected using HR-TEM/FE-SEM and vice versa. The occurrence of anglesite, gypsum, hematite containing PHEs, and several organic compounds associated with modifications due to moisture and pollution was also demonstrated. Image 1 • Advanced system allows particles and geochemical analysis exclusive of sampling. • First wide work regarding the nanoparticles of ornamental structures pollutions. • Multianalytical approach of walls in an UNESCO World Heritage Site of Granada. [ABSTRACT FROM AUTHOR]

Small mammals, especially rodents, constitute valuable proxies for continental Quaternary environments at a regional and local scale. Recent studies have demonstrated the relation between the stable oxygen isotope composition of the biogenic phosphate from rodent teeth (δ18O p), and the oxygen isotope composition of meteoric waters (δ18O mw), which is related to air temperatures at mid and high latitudes. This work explores the δ18O p of rodent tooth enamel (from Murinae and Arvicolinae subfamilies) to investigate the palaeoenvironmental conditions in northeastern Iberia during Marine Isotope Stage 3 (MIS 3; ca. 60-30 ka). Fourteen new δ18O p analyses from modern samples in conjunction with forty-six δ18O p analyses previously published are used to decipher the isotope record of present-day rodent teeth in this region. Two main factors should be considered in Iberian palaeoenvironmental reconstructions: the singular nature of Iberian δ18O mw records and the potential seasonality bias of small-mammal accumulation. Methodological proposals are made with a view to ensuring the correct interpretation of the δ18O p of small mammals in reconstructing past air temperatures. This methodology is applied to the MIS 3 sequence of the Cova dels Xaragalls site (Vimbodí-Poblet, Tarragona, Spain), where fifty-one δ18O analyses were performed on wood mouse (Apodemus sylvaticus) lower incisors. A spring-early summer accumulation of small mammals is suggested for the layers at Cova dels Xaragalls. In agreement with previous environmental studies of the site, variations in the δ18O p values suggest slight fluctuations in the climatic conditions throughout the sequence, which are consistent with the stadial-interstadial alternations that characterized MIS 3. Complementary palaeoenvironmental methods determine cooler conditions than nowadays, but within a globally stable climatic period. • Oxygen isotopes analyses on rodent contributes to continental environment knowledge. • Iberia requires a specific regional equation for past temperatures estimation. • Prey-predator interactions influence oxygen isotope temporal information recorded. • Seasonality bias and Iberian context are considered in the methodological proposal. • Complementary palaeoenvironmental methods yielded matching results at Xaragalls cave. [ABSTRACT FROM AUTHOR]

Abstract In the Mediterranean region, floods are expected to increase as a result of climate change and knowledge of soil erosion hot spots during exceptional rainfalls is required to support mitigation measures. This study quantifies the main sediment sources during an exceptional rainfall event in 2012 (235 mm) at the outlet of two catchments located in NE Spain. To this purpose, suspended sediments were collected during the flood event, complemented with entrapped sediments in mat taken one year after the event. We used fingerprinting methodology and applied the FingerPro unmixing model to estimate the contribution from main sources. The selected tracers clearly distinguished agricultural, rangeland, subsoil and channel banks as the four potential sources in both catchments. In the Vandunchil catchment, the 8 time-integrated suspended sediment samples revealed changes in source contribution during the 2-h sampling sequence. There were relatively high contributions from rangeland, agriculture and subsoil at the beginning of the sampling, representing 30, 40 and 35% of the total source contributions, respectively. Our records captured the delivery of pulses of eroded surface soil transported by runoff with direct connectivity to the stream. The sequence was followed by a sharp increase in channel bank contribution (up to 90%) in comparison to the other sources, reflecting streambank erosion and landslide occurrence, which manifested during the flood. In contrast, in the La Reina catchment, agricultural soils contributed the most (65%) and, together with subsoils (32%), were the main sources. These results reflect the effect of the higher connectivity and slope gradient of these cultivated fields of the La Reina catchment in comparison with those of the Vandunchil catchment. We discuss the possibility of using different properties, such as radionuclides, geochemistry and magnetic measurements, as tracers to distinguish between potential sources during an exceptional event in upland Mediterranean catchments. Our results support the use of fingerprinting techniques to determine variations in source contribution and sediment provenance during flood events, as extreme rainfalls are main drivers of sediment mobilization and key factors in changing landscapes. This is essential in identifying vulnerable hot spots, in which early-stage interventions are needed, and for helping policy makers with management of soil and water resources. Graphical abstract Image 1074 Highlights • Unique opportunity to capture soil response during an exceptional event of 235 mm. • Suspended sediment properties changed during the flood event. • Source contributions varied in response to the rainstorm in a short period. • Switch from soil sources to channel bank provenance was captured during the flood. • Land use and connectivity determined the suspended sediment provenance. [ABSTRACT FROM AUTHOR]

Abstract Aragonite speleothems are increasingly being used as high-resolution climate proxies; however, aragonite is unstable and susceptible to diagenetic transformation into calcite leading to mineralogical, textural and geochemical alterations that have not been fully investigated. To provide some insights to these modifications, this study combines stable isotope geochemistry and U-series dating with petrological observations and EMPA elemental analyses to characterize a stalagmite from Castañar Cave (Cáceres, Spain) that shows primary aragonite diagenetically altered and with reverse ages. The diagenetic processes include recrystallization to calcite, micritization and dissolution. Characterization and interpretation of the chemistry and nature of the waters from which the aragonite precipitated, and of the ones that subsequently formed the calcite, indicates that both polymorphs formed from the same fluids. These fluids hydrochemically evolved from an "aragonite mode" to a "calcite mode" along a diagenetic path within the sample. The results show that during transformation the system stayed close in one of the stages, and open in the other with the same textural result. Reverse ages are found either in the recrystallized areas or in the primary aragonite, caused by two different U-remobilization mechanisms, U-leaching due to flowing waters on the surface, and U-loss during the transformation process. These results highlight the complex behavior of speleothems during diagenesis and the impact on the geochemical information of the primary and secondary phases, and thus the importance of petrological and geochemical characterization of speleothems for paleoclimatic studies. [ABSTRACT FROM AUTHOR]

In the framework of a postdoctoral project to geochemically characterise Pyrenean cherts, a new marine chert outcrop in the Central Pyrenees has been defined. This new discovery, called the Buala outcrop, and its flysch chert type, provide new information about marine chert sources in the Pyrenean chain, leading us to reconsider prehistoric chert procurement in this area. Until now, two geological formations from the Central Pyrenees were considered as potential sources for a type of marine chert usually appearing in the Magdalenian record of several Pyrenean sites: Montgaillard flysch cherts and Montsaunès cherts. With both formations presenting similar characteristics, it was only through the use of geochemical methods that differences were recently established as reported by Sánchez de la Torre et al. (STAR 3:15-37, 2017b). This paper presents the new marine flysch chert outcrop of Buala. The visual, micropalaeontological and geochemical characterisation of this chert has permitted the definition of a new potential source for this marine chert type, which is common in several Palaeolithic sites in the Pyrenees, as Cova del Parco (Alòs de Balaguer, Spain), Forcas I Shelter (Graus, Spain), Montlleó open-air-site (Prats i Sansor, Spain), or Caune de Belvis (Belvis, France) (Sánchez de la Torre 2015). Geochemical characterisation of the three potential sources was carried out using energy-dispersive X-ray fluorescence (ED-XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Results show that Buala flysch cherts are clearly different from the previously known chert types in terms of major, minor, and trace elements. [ABSTRACT FROM AUTHOR]

Castilla-La Mancha (central Spain) is a region characterized by significant agricultural production aimed at high-quality food products such as wine and olive oil. The quality of agricultural products depends directly on the soil quality. Soil geochemistry, including dispersion maps and the recognition of baselines and anomalies of various origins, is the most important tool to assess soil quality. With this objective, 200 soil samples were taken from agricultural areas distributed among the different geological domains present in the region. Analysis of these samples included evaluation of edaphological parameters (reactivity, electrical conductivity, organic matter content) and the geochemistry of major and trace elements by X-ray fluorescence. The dataset obtained was statistically analyzed for major elements and, in the case of trace elements, was normalized with respect to Al and analyzed using the relative cumulative frequency (RCF) distribution method. Furthermore, the geographic distribution of analytical data was characterized and analyzed using the kriging technique, with a correspondence found between major and trace elements in the different geologic domains of the region as well as with the most important mining areas. The results show an influence of the clay fraction present in the soil, which acts as a repository for trace elements. On the basis of the results, of the possible elements related with clay that could be used for normalization, Al was selected as the most suitable, followed by Fe, Mn, and Ti. Reference values estimated using this methodology were lower than those estimated in previous studies. [ABSTRACT FROM AUTHOR]

The lithographic limestone of La Pedrera de Meià (LPM) in south-Central Pyrenees (NE Spain) is considered one of the best preserved lacustrine-coastal successions of the Early Cretaceous in Europe, hosting a taxonomically diverse record of Barremian biota. While this Konservat-Lagerstätte has been extensively surveyed for paleontological purposes, little is known about the paleoenvironmental and depositional conditions prevailing during the formation of this fossil lagerstätte deposit. LPM limestone is made up of a homogeneous, dark gray to pale brown, faintly laminated 50 m-thick succession of micrite-rich intervals. To shed light on the environmental conditions of deposition, 303 rock samples were studied using a multiproxy approach based on different techniques including petrography, SEM-EDX, XRD, ICP-MS, XRF, Rare Earth Element distributions and C and O stable isotope geochemistry. The combination of sedimentological and geochemical data reveals a vertical shift of facies from littoral to profundal environments and then returning to littoral conditions. Profundal facies are made up of filament-rich mudstones originated from in situ precipitation of micrite either through biotically mediated or physico-chemical processes in undisturbed low energy settings, under anoxic conditions, characterized by the presence of transported terrestrial and lacustrine organisms that are exquisitely well-preserved. Littoral areas are characterized by the presence of in situ charophytes, smooth ostracods, and miliolid foraminifera that accumulated in mud-rich facies indicating low/moderate-energy, shallow-water, and relatively oxygenated conditions. Stable isotopic data and elemental geochemistry suggest a hydrologically closed to semi-closed lacustrine system with a restricted water circulation encouraging dysoxic to anoxic conditions in profundal sediments. Paleoproductivity proxies suggest a good correlation between catchment-derived siliciclastic discharge to the lake and primary productivity peaks. Furthermore, a decline in terrigenous input coupled with a reduction of meteoric water entrance to the lake is interpreted based on elemental proxies derived from paleosalinity and paleoredox analysis. Collectively, the strontium/barium (Sr/Ba) ratios, the sparse presence of miliolid foraminifera, and the isotopic signatures indicate an increase in salinity toward the younger intervals of the lake infilling, although their ultimate causes are unclear (i.e., increased evaporation, or a combination of reduced meteoric input and sporadic marine inputs might explain our data). The present work shows the importance of performing detailed multiproxy geochemical-sedimentological studies to better constrain the unique paleoenvironmental and paleohydrological conditions associated with the exceptional preservation of fossil biotas in Konservat-Lagerstätte deposits in analogous depositional settings. [ABSTRACT FROM AUTHOR]

The last hyperthermal event in the Eocene, the Late Lutetian Thermal Maximum or Chron C19r event, took place at ~41.5 Ma, during a long-term global cooling phase which occurred between the warm Early Eocene Climatic Optimum and the icehouse Oligocene Epoch. This paleoclimatic event was first identified in the Equatorial Atlantic Ocean Drilling Program (ODP) Site 1260 as an abrupt peak in bulk Fe content and a short-lived decline in stable isotopes (δ 13 C, δ 18 O) and carbonate content. Additional studies have recently been carried from the Southern Atlantic ODP sites 702 and 1263. However, many issues were not addressed at these deep-sea sites and no land-based record of the event had been studied. Therefore, the beach cliff at Cape Oyambre (N Spain) was analyzed with the aim of identifying the C19r event and investigating its paleoenvironmental impact. Using magnetostratigraphic and biostratigraphic information, the astronomically tuned cyclo-stratigraphic record from Oyambre was accurately correlated with ODP Site 1260. This, combined with stable isotope data, allowed identification of the event in a conspicuous dark marl bed. Given that the associated negative carbon isotope excursion extends for 2/3 of a precession-driven hemicouplet, a 7–11 kyr duration was estimated, which agrees with recent estimates from the Atlantic deep-sea sites. Exceptional insolation conditions were found to have accelerated the hydrological cycle, increasing rainfall and runoff on land and terrestrial sediment input to the sea, which resulted in relatively low carbonate content in the deep-sea sediments. The terrestrial input also caused seawater eutrophication and freshening, leading to low δ 13 C and δ 18 O values, increased abundance of autochthonous and reworked calcareous nannofossil taxa, peaks in the abundance of opportunistic Reticulofenestra <5 μm and opportunistic benthic foraminifera, and a reduction in the abundance of the oligotrophic calcareous nannofossil Zygrhablithus bijugatus . However, neither intensified carbon-gas driven greenhouse effect nor warming over and above natural fluctuations could be demonstrated from the Oyambre data. [ABSTRACT FROM AUTHOR]

When considering complex scenarios involving several attributes, such as in environmental characterization, a clearer picture of reality can be achieved through the dimensional reduction of data. In this context, maps facilitate the visualization of spatial patterns of contaminant distribution and the identification of enriched areas. A set, of 15 Potentially Toxic Elements (PTEs) – (As, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn), was measured in soil, collected in Langreo's municipality (80 km 2 ), Spain. Relative enrichment (RE) is introduced here to refer to the proportion of elements present in a given context. Indeed, a novel approach is provided for research into PTE fate. This method involves studying the variability of PTE proportions throughout the study area, thereby allowing the identification of dissemination trends. Traditional geostatistical approaches commonly use raw data (concentrations) accepting that the elements analyzed make up the entirety of the soil. However, in geochemical studies the analyzed elements are just a fraction of the total soil composition. Therefore, considering compositional data is pivotal. The spatial characterization of PTEs considering raw and compositional data together allowed a broad discussion about, not only the PTEs concentration's distribution but also to reckon possible trends of relative enrichment (RE). Transformations to open closed data are widely used for this purpose. Spatial patterns have an indubitable interest. In this study, the Centered Log-ratio transformation ( clr ) was used, followed by its back-transformation, to build a set of compositional data that, combined with raw data, allowed to establish the sources of the PTEs and trends of spatial dissemination. Based on the obtained findings it was possible to conclude that the Langreo area is deeply affected by its industrial and mining legacy. City center is highly enriched in Pb and Hg and As shows enrichment in a northwesterly direction. [ABSTRACT FROM AUTHOR]

The old mining district of Linares (Southern Spain) was subject to intense Pb mining, minerallurgical and metallurgical activities for centuries, causing significant contamination of nearby soils. In this area the present study analysed the surroundings of the former lead smelter of La Cruz, where, in previous studies, soils with high metal(loid) contents were detected. To determine the intensity, spatial distribution and dispersion mechanisms of different trace elements, a geochemical prospecting campaign was designed in which 44 samples were collected from a 2.2 km 2 surface area around the smelter. Of the 33 elements analysed, nine metal(loid)s (Cu, Pb, Zn, Ag, As, Sb, Bi, Cd and Tl) were found to have a high enrichment factor (EF). These elements show mean concentrations of 672, 6491, 464, 2.8, 75, 20, 2, 13 and 2.9 mg kg −1 , respectively, values which largely exceed the levels of the environmental quality standards for soils established by both regional and European regulations. Multivariate analysis and geostatistical distribution maps enabled the most intensely contaminated areas to be characterised. The results obtained indicate that the main contamination zone is related to the smelter itself, with two different dispersal mechanisms: the first is linked to the gases and dust emissions generated by the metallurgical processes, and transported by the prevailing winds, in Southwest-Northeast direction; the second is associated with the leachate produced in the smelter residues. Additionally, two other secondary foci are formed by tailings ponds and mining residues. The contamination areas are known to affect a residential zone near the old smelter installations and land located Northeast of these areas, where there is an olive grove. The results of this study should therefore serve as a basis for the adoption of corrective measures to minimize the adverse effects on the soil from the old mining-metallurgical activities. [ABSTRACT FROM AUTHOR]

Copper smelters represent a major anthropogenic source of SO 2 and sulphide-related elements into particulate matter, affecting the air quality of the surrounding areas. The implementation of measures to reduce the emission of gaseous contaminants and particles in industrial processes is a major issue, which aims to establish technological progress for cleaner production. In this sense, a long-range study covering the period 2001–2015 has been performed in the SW Spain, where one of the largest Cu-smelters in Europe is located. Trends of PM 10 and PM 2.5 levels and geochemical patterns were studied considering the following periods: prior (2001–2008), during (2009–2013) and after (2014–2015) the implementation of emission abatement technology (wet electrofilters, bag filters and lime injection) by this large industrial facility. The results evidenced relatively high concentrations of sulphide-related elements (annual mean of 6.1, 1.7, 0.7, 2.2, 2.0, 21.0 and 1.0 ng m −3 for As, Se, Cd, Sn, Sb, Pb and Bi, respectively) during 2001–2008. A reduction of 50% was observed for the last period (2.8, 0.5, 0.2, 1.6, 1.1, 6.7 an d 0.3 ng m −3 for the same elements, respectively) in PM 10 . A similar trend was observed for PM 2.5 samples. However, the number of episodes of SO 2 has not changed along the studied period (average 8 days/month), although the SO 2 concentration during the pollution episodes has markedly diminished from maximum peak concentrations of 350 μg m −3 to 170 μg m −3 . A high arsenic concentration is the main geochemical anomaly found in PM, reaching annual mean concentrations up to 10.4 ng m −3 in 2005 above the annual EU target value (6 ng m −3 ) in PM 10 , decreasing down to 2.7 and 2.9 ng m −3 in 2014 and 2015, respectively. However, sporadically high episodic levels are still recorded (e.g. 26.8 ng m −3 in 2014 and 14.9 ng m −3 in 2015). [ABSTRACT FROM AUTHOR]

Purpose: Geochemical and mineralogical studies of soils potentially polluted by trace elements are basic to find the source of pollution, to understand the behavior of the contaminants in the environment, and to propose remediation and reclamation actions. This work reviews the role of the Mineralogy and Geochemistry to assess the hazard of soil contamination by trace elements in mining areas, focusing on three different case studies carried out in the Andalusian community (South Spain), with a Mediterranean temperate climate.Materials and methods: Two significant mining districts were selected for this work: the Linares-La Carolina (Pb-Zn ores) and the Riotinto (Iberian Pyrite Belt, IPB) mining areas. Another case study was the Guadiamar basin, which soil was polluted by the spill produced in 1998 by the breakage of a mine tailing impoundment in Aznalcóllar mines (IPB). Soils, mine waste, and secondary precipitates were studied to approach the source of the pollution and the fate of the contaminants. Chemical composition (major and trace elements), soil parameters, and mineralogy of all materials selected were studied. In addition, the bioavailability of trace elements was determined by different methods.Results and discussion: Pyrite and secondary phases are the main sources of pollution in the Riotinto area. Their stability is a key factor in the release of trace elements. The availability of trace elements in soils was lower in unpolluted leptosols than in contaminated orchards. In Linares-La Carolina, a severe pollution by Pb and a high availability (10-70% extracted with EDTA) were found. In Guadiamar basin, the residual pyrite sludge continues releasing trace elements to soil. Cd and Zn were mobile at pH < 6 and As at pH > 8, and Pb was quite immobile. Cd, Zn, and Pb can be coprecipitated by carbonates while As is mainly adsorbed by clays and iron oxyhydroxides.Conclusions: The geochemical studies of soils polluted by mining activities allow to evaluate the availability of trace elements and their retention in soils. Therefore, geochemical and mineralogical studies are necessary for the assessment of soil pollution and remediation actions. [ABSTRACT FROM AUTHOR]

Surface liquid and solid hydrocarbons are common in Cretaceous carbonate exposures throughout the Basque Cantabrian Basin (N Spain). This study investigates the oil shows that appear in the upper Albian-lower Cenomanian reefal limestones cropping out in the eastern margin of the basin in order to assess potential source rocks and common characteristics with other oil occurrences in the basin. Specifically, the study focuses on (i) the petrography and fluid inclusion thermometry of the host rock and cements, and (ii) geochemistry of the hydrocarbons including biomarkers and isotopes. Geochemistry results indicate that the studied oils, in a way similar to previously reported hydrocarbons from the eastern Basque Cantabrian Basin, were generated from marine carbonate source rocks deposited in a hypersaline environment. However, their isotopic signatures are notably different, and thus discard a common source rock. Moreover, the studied oils are notably different from those reported elsewhere in the basin, both in the western and northern parts. The petrography of the calcite cements and the fluid inclusion thermometry suggests a scenario of condensates to light oils HC migration trapped in burial calcite cements at a minimum temperature of 174 °C. The generation, migration and entrapment of these oils took likely place between Turonian and Campanian time in close association with the elevated heat flow resulting from the rift extension. Following this stage, a second entrapment of heavy to asphaltene-rich oils occurred at 72 °C, likely during the Late Cretaceous to early Cenozoic uplift related to the early stages of inversion of the Basque Cantabrian Basin. The elevated temperature of the oil entrapment suggests the occurrence of abnormal geothermal gradients in the eastern Basque Cantabrian Basin during the middle Late Cretaceous, which is ultimately associated with the opening of the Bay of Biscay. [ABSTRACT FROM AUTHOR]

This article focuses on a former salt lake in the upper Vinalopó Valley in south-eastern Spain. The study spans the Late Pleistocene through to the Late Holocene, although with particular focus on the period between 11 ka cal BP and 3000 ka cal BP (which spans the Mesolithic and part of the Bronze Age). High resolution multi-proxy analysis (including pollen, non pollen palynomorphs, grain size, X-ray fluorescence and X-ray diffraction) was undertaken on the lake sediments. The results show strong sensitivity to both long term and small changes in the evaporation/precipitation ratio, affecting the surrounding vegetation composition, lake-biota and sediment geochemistry. To summarise the key findings the main general trends identified include: 1) Hyper-saline conditions and low lake levels at the end of the Late Glacial 2) Increasing wetness and temperatures which witnessed an expansion of mesophilic woodland taxa, lake infilling and the establishment of a more perennial lake system at the onset of the Holocene 3) An increase in solar insolation after 9 ka cal BP which saw the re-establishment of pine forests 4) A continued trend towards increasing dryness (climatic optimum) at 7 ka cal BP but with continued freshwater input 5) An increase in sclerophyllous open woody vegetation (anthropogenic?), and increasing wetness (climatic?) is represented in the lake record between 5.9 and 3 ka cal BP 6) The Holocene was also punctuated by several aridity pulses, the most prominent corresponding to the 8.2 ka cal BP event. These events, despite a paucity of well dated archaeological sites in the surrounding area, likely altered the carrying capacity of this area both regionally and locally, particularly during the Mesolithic-Neolithic transition, in terms of fresh water supply for human/animal consumption, wild plant food reserves and suitable land for crop growth. [ABSTRACT FROM AUTHOR]

The Santa Lucía Formation represents the major phase in Devonian reef development of the Cantabrian Zone (Cantabrian Mountains, northwest Spain). In the present study the transition from the carbonate platform deposits of the Santa Lucía Formation to the overlying euxinic basinal deposits of the Huergas Formation is described. These transitional strata are connected to the Basal Choteč Event and represent a condensed sedimentation of micritic dark-grey and black limestones with an upward increase of dark shale intercalations with iron mineralisation surfaces and storm-induced brachiopod coquinas. The transitional beds are grouped into a new unit, the Cabornera Bed, which consists of limestone, limestone-shale and shale facies associations, representing a sediment-starved euxinic offshore area just below the storm wave base. Four stages in reef decline can be recognised: a reef stage, an oxygen-depleted, nutrient-rich stage, a siliciclastic-influx stage and a pelagic-siliciclastic stage. Additional geochemical and geophysical investigations are needed to verify the results presented herein. [ABSTRACT FROM AUTHOR]

The Tiermas low temperature geothermal system, hosted in the Paleocene-Eocene carbonates of the Jaca-Pamplona basin, has been studied to evaluate the geochemistry and the temperature of the waters in the deep reservoir. These waters are of chloride-sodium type and emerge with a temperature of about 37 °C. Two hydrogeochemical groups of waters have been distinguished: one with lower sulphate concentration and lower TDS (about 7500 ppm) and the other with higher sulphate content and TDS values (close to 11,000 ppm). There are also slight differences in the reservoir temperature estimated for each group. These temperatures have been determined by combining several geothermometrical techniques: (1) classical chemical geothermometers (SiO 2 -quartz, Na-K, K-Mg and Na-K-Ca), (2) specific geothermometers for carbonate systems (Ca-Mg), (3) isotopic geothermometers and, (4) geothermometrical modelling. The good agreement in the temperature obtained by these techniques, including the cationic geothermometers which are not usually considered suitable for this type of systems, allows establishing a reliable range of temperature of 90 ± 20 °C for the low-sulphate waters and 82 ± 15 °C for the high-sulphate waters. The mineral assemblage in equilibrium in the reservoir is assumed to be the same for both groups of waters (calcite, dolomite, quartz, anhydrite, albite, K-feldspar and other aluminosilicate phases); therefore, the differences found in the reservoir temperature and, mostly, in the geochemical characteristics of each group of waters must be due to the existence of two flow paths, with slightly different temperatures and intensity of water-rock interaction. Anhydrite is at equilibrium in the reservoir suggesting that, although this system is hosted in carbonates, evaporites may also be present. The dissolution of halite (and the consequent increase in the chloride concentration) conditions the chemical characteristics of the waters and the equilibrium situations in the reservoir and waters acquire their chloride-sodium affinity at depth and not during their ascent to the surface. Finally, a favourable tectonic structure for CO 2 storage has been recognised in the Paleocene-Eocene carbonates of this area. Therefore, considering the characteristics of these waters (in equilibrium with calcite, dolomite and anhydrite in the reservoir), the results of this work are useful to understand some of the geochemical processes that might take place during the CO 2 injection: 1) precipitation of carbonates and sulphates in the vicinity of the injection well due to desiccation of the waters and, 2) carbonate dissolution and sulphate precipitation in the long term. [ABSTRACT FROM AUTHOR]

The Malpica-Tuy complex (MTC) in northwestern Spain is a key area for the understanding of geodynamic processes related to the early collision of Gondwana and Laurussia. To better understand this collisional situation in Variscan times, we deciphered mass-flow paths in terms of pressure (P) and temperature (T) for five samples (three eclogites, a glaucophanite and a tonalitic gneiss) occurring in a large eclogite body at the 'La Pioza' site in the central MTC. The following three contrasting P-T paths resulted from the application of P-T pseudosections, calculated with PERPLE_X, and Zr-in-rutile geothermometry. (1) Two eclogites and the gneiss yielded a similar anticlockwise P-T path. In particular, one of these eclogites recorded an extended prograde path from about 8·5 kbar at 575°C to peak pressures of ~24·5 kbar at 630°C. The retrograde path passed through P-T conditions of ~17·5 kbar and 650°C. (2) A clockwise P-T loop was derived for an eclogite starting at ~18 kbar at 580°C to peak pressures of ~23 kbar at 620°C. (3) The clockwise P-T path of the glaucophanite is characterized by a temperature increase from 610 to 680°C at nearly constant pressure around 19 kbar. The peak P of rocks in the eclogite body is much higher than that of the surrounding gneisses (≤13 kbar). Major and trace element geochemical features demonstrate that the protoliths of one eclogite and the glaucophanite were calc-alkaline igneous rocks. The other two eclogites have a tholeiitic affinity. The tonalitic gneiss is characterized by a subalkaline affinity. All the mafic rocks are characterized by a Nb anomaly. The protoliths of the eclogite with calc-alkaline affinity and the gneiss can be assigned to a continental magmatic arc formed in Late Cambrian times according to previous age dating results. The protoliths of the eclogites with tholeiitic affinity were related to basalt/gabbro of thickened oceanic crust (island arc in the Rheic Ocean). The contrasting P-T paths and different nature of the protoliths are explained by different upwardsdirected mass flows and, thus, mixing of various types of rocks in a subduction channel. Our findings also support the hypothesis that the MTC represents subduction-related rocks embedded in high-pressure orthogneisses from the downgoing tip of a continental plate during initial continent-continent collision. [ABSTRACT FROM AUTHOR]

Continental carbonates are currently of high interest for the oil and gas industry, as they have proved to be good reservoir rocks in Brazil and Angola offshore oil fields. In this article, a tufa system in which continental carbonates formed mainly in the Pliocene (Rambla Becerra Tufa System, Guadix Basin, Betic Cordillera, S. Spain), is described in detail, and a model proposed for its formation and evolution through time. Several stages of tufa growth have been identified in the field, intercalated between stages of progradation of alluvial fan sediments. The tufa system connects laterally with the fluvial system developed in the axial valley of the Guadix Basin during the Pliocene and the Pleistocene, indicating that the tufa formation was coetaneous with the periods of lateral expansion of the fluvial system floodplain, that in previous works have been interpreted as more humid stages and potentially warmer. The absence of extraclasts in the tufa sediments points to the low activity of the alluvial fans during the tufa formation and therefore supports the idea that the main tufa growth happened during more humid stages, and the alluvial fans developed further during the more arid periods, which is consistent with other recent findings in the Guadix Basin. The tufa growth is represented by four main stages, the second one bearing the best example to study as a potential reservoir analog, as the main outcrop is a discrete body with a specific geometry and facies distribution. This main outcrop is a mound-shaped tufa build-up formed by prograding sigmoids of clastic tufa, interpreted as the ramp-like buttresses developed after a barrage in a barrage tufa system. From a preliminary isotopic study of the carbonates forming the barrage tufa system and by comparison with other tufas and travertines, the oxygen and carbon stable isotopes point to an intermediate situation between a palustrine tufa and a travertine. This information, when added to the sedimentological data, supports the idea that water feeding the tufa system probably had different sources: a meteoric one, coinciding with the surface runoff and a groundwater one, probably in the form of springs fed by groundwater from the nearby aquifers that still exist in the Mesozoic carbonates that form the External Zones of the Betic Cordillera in the area. [ABSTRACT FROM AUTHOR]

Four outcrops of Lower Cretaceous (Barremian) karst bauxites located in Teruel (NE Spain) were analysed. The deposits show a heterogeneous-chaotic lithostructure consisting of pisolitic bauxite blocks embedded in lateritic red clays filling karst cavities. The research has focused on the geochemical study of major, minor, and trace elements (including some critical to industry) of both the bauxites and clays. The objective was to investigate the bauxite precursor material and to characterize the system’s geochemical evolution. Geochemical analyses were carried out by inductively-coupled plasma optical emission and mass spectroscopy. An absolute weathering index has been calculated to estimate element mobility, assuming Ti as an immobile element and the Upper Continental Crust (UCC) as parent material. Further, selected samples were observed by field emission scanning electron microscopy. The data indicate that both the bauxites and red clays originated by intense chemical weathering from more mafic argillaceous sediments than the UCC. Ongoing weathering caused the bauxitization of the upper parts of the original profile, preventing the lower parts from being bauxitized, thus producing the ferrallitized clays underlying the pisolitic bauxites. Subsequent karst reactivation gave rise to the current lithostructure. Ferrallitization is related to Fe, Sc, and V enrichment. On the other hand, although bauxites are relatively enriched in some elements compared to clays, the more intense chemical weathering associated with bauxitization led to chemical homogenization and widespread element depletion. During the bauxitization, Al, Ti, Zr, Cr, and probably Hf and the critical element Nb behaved as more immobile elements in the system. Bauxitization also enhanced homogenization and depletion of the REE, which is more pronounced for the LREE. HREE trends seem to be partly related to the concentration of Ti oxides in the bauxites, whereas P-bearing phases, more frequent in the clays, control the LREE. Subsequent to bauxitization, partial kaolinization of the bauxite took place related to the circulation of acid solutions that also caused the karst reactivation. These late processes caused some Al depletion in the bauxites and enhanced Fe loss together with V and, to a lesser extent, Ge. [ABSTRACT FROM AUTHOR]

The objective of the present work was to verify and compare the performance of different geochemical indices employed to identify the anthropogenic origin of selected heavy metals and other trace elements in soils. To that end, two background values, the upper continental crust and the metal content in the bed rock, were used and obtained from a forested basin of the western Pyrenees. The enrichment factor (EF), geo-accumulation index (I), and contamination factor (C ) were finally evaluated for their ability to determine anthropogenic contamination: Results indicate that an in-depth knowledge of the bed rock geochemistry and the geological background content is essential to distinguish between the natural variability of soils and any anthropogenic contribution of heavy metals. Although both EF and C show a similar ability to detect soil contamination, the latter is proposed as a more appropriate and sensitive marker given its ability for finding episodically elevated contamination levels. [ABSTRACT FROM AUTHOR]

Maltravieso cave (Estremadura, Spain) was recently the subject of ATR-FTIR spectroscopy of 8 figures (four hand stencils, a red horse figure, a black bull figure, a pair of black lines, and a pair of brown lines). These artistic representations are composed of different colors including red, brown, and black figures. The analyses showed that different naturally occurred material compounds in the cave (such as kaolinite) were used in the creation of the ochre to obtain different hues. Hand stencils are made of earth pigment that is naturally present in the cave which contained hematite, magnetite, and goethite as chromophores material. The red horse figure was made with kaolinite-based ochre. The black bull figure was made with charcoal (identified with Raman spectroscopy). The pigmental composition analyses show that they are composed of the same natural matter found inside the cave. Our results suggest that different paintings in the cave have been produced by different techniques and these techniques are linked to different chronological periods. [ABSTRACT FROM AUTHOR]

Utilitarian greyware ceramics are one of the most abundant artefacts at rural sites in Medieval Catalonia, Spain, and were manufactured by numerous long-lived production centres. The stylistic homogeneity of this class of pottery has traditionally restricted its contribution to the archaeological interpretation of the region. However, recent scientific analyses of excavated kiln sites are offering new perspectives via the establishment of compositional reference groups for greyware ceramics. Using one such dataset, from the large workshop of Cabrera d'Anoia, this paper examines the distribution and consumption of utilitarian grey pottery at 25 Medieval sites across Catalonia. The study reveals a pattern of several regional production centres distributing their goods to small villages within the surrounding countryside and, in some cases, competing for rural markets. This is interpreted in terms of the mechanisms by which greyware pottery was distributed, as well as the socio-political and religious influences on its supply and demand in Medieval Catalonia. [ABSTRACT FROM AUTHOR]

The trace element geochemistry of sepiolite-rich beds from five lithological sections in the Neogene Madrid Basin was analysed. The samples were collected from representative deposits including alluvial fan (Vicálvaro, Cabañas de la Sagra), palustrine (Cerro de los Batallones) and mudflat (Esquivias, Magán) facies. The mineralogical composition of the samples point out the abundant content of sepiolite, commonly higher than 95%, with variable content of quartz, feldspars, calcite, palygorskite and/or Mg-smectite. The sepiolite occurs as laminated, massive and brecciated facies, often with intraclasts of similar sepiolite composition. The geochemical results indicate that all the trace elements analysed are mostly depleted with respect to the UCC standard (Upper Crust Composition), especially REE (< 0.4). The higher depletion was observed in sepiolites from mudflat facies (V and U content are an exception). Cluster analysis of geochemical data corroborates the differences between mudflat sepiolites and those from palustrine and alluvial-related facies. The normalization of REE with chondrite allows clear differentiation between the sepiolites associated with alluvial fan facies from all the remaining samples. On the other hand, the La/Sc ratio against Th/Co ratio indicates provenance from felsic rocks. High content in F (> 4000 μg/g) and low content of Li (20–180 μg/g) is remarkable, allowing to separate samples of sepiolite formed in alluvial fan environments from those of mudflat and palustrine deposits. The geochemical complexity observed in the sepiolites was closely related to the specific mechanisms of formation under different environmental conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mineral-chemical associations were studied in urban soils of Minas de Riotinto. • Natural soils have significantly higher concentrations of Cu, Zn, As, Sb, Ba, and Pb. • Plumbojarosite and beudantite trap effectively As and Pb. • Metal(loid)-rich particles < 10 µm pose exposure risk to humans via inhalation. • Covering the natural soils is recommended to minimize human exposure risk. Polluted soil is an important source of exposure to potentially toxic elements (PTEs) for humans, especially in urban areas. We studied the fate of PTEs in the total (<2 mm) and fine (<50 µm) fractions of urban soils in playgrounds, passing areas, and vacant lots of the historic mining village of Minas de Riotinto in SW Spain. The mineralogical and chemical observations included analysis by scanning electron microscopy, electron backscatter diffraction, X-ray diffraction, chemical analysis of Al, V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, As, Cd, Ba, Tl, and Pb after acid digestion by Inductively Coupled Plasma-Mass Spectrometry and Sb by X-ray fluorescence. The total and fine fractions of natural and mixed (consisting of natural soils and aggregate pavements) urban soils have significantly higher concentrations of sulfide-associated PTEs (Ni, Cu, Zn, As, Sb, and Pb) and Ba in comparison to the aggregate pavements. Most of the natural and mixed urban soils surpass the regulatory levels set by the regional Government for As and Pb to declare a soil as contaminated. This work highlights the mineralogical source of PTEs in the urban soils. Primary geogenic sulfide minerals are prone to oxidation promoting dissolution of PTEs and acid generation in the future. Additionally, for the first time, we have described arsenian plumbojarosite and beudantite in urban soils which are abundant secondary phases under the circumneutral pH conditions, effectively retaining As and Pb. Inhalable small PTE-rich particles (<10 μm) are present in many soils in playgrounds and garden areas potentially posing health risk to residents upon dusting and resuspension in the air. [ABSTRACT FROM AUTHOR]

Loess research has the merit of enabling reconstructions of Pleistocene sedimentation dynamics in many parts of the world. However, there is still very few information regarding the occurrence of loess deposits in the Mediterranean area, even though such records may provide a unique opportunity to investigate landscape evolution for a period for which terrestrial archives are very rare in this region. This paper presents the first results of investigations on a loess sequence in the middle Tajo Valley in central Spain. Findings from detailed granulometrical, mineralogical, geochemical, and grain morphological analyses help to give a first overview on character and composition of these deposits. Very high levels of carbonates (∼60%), but also of gypsum, both to large extents of primary origin, indicate the incorporation of material derived from marls and limestone. Furthermore, we found evidence that allows deduction of possible loess proveniences more precisely. Dolomite contents of up to 20% indicate that the Iberian Range might have been an important source area of loess sediments. The fact that these uplands are located to the east seems to be opposed to the common assumption of prevailing west winds for glacial periods. The studied sequence (Paraiso profile) is one of seven sections that have been investigated as part of a programme to reconstruct Upper Pleistocene landscape dynamics in central Spain. In this context, the detailed characterisation of sediment properties is crucial for discussing loess proveniences and sedimentary environments. [ABSTRACT FROM AUTHOR]

We present a palaeoenvironmental study of the Castelló lagoon (NE Spain), an important archive for understanding long-term interactions between dynamic littoral ecosystems and human management. Combining geochemistry, mineralogy, ostracods, diatoms, pollen, non-pollen palynomorphs, charcoal and archaeo-historical datasets we reconstruct: 1) the transition of the lagoon from a marine to a marginal environment between ~3150 cal BC to the 17th century AD; 2) fluctuations in salinity; and 3) natural and anthropogenic forces contributing to these changes. From the Late Neolithic to the Medieval period the lagoon ecosystem was driven by changing marine influence and the land was mainly exploited for grazing, with little evidence for impact on the natural woodland. Land-use exploitation adapted to natural coastal dynamics, with maximum marine flooding hampering agropastoral activities between ~1550 and ~150 cal BC. In contrast, societies actively controlled the lagoon dynamics and become a major agent of landscape transformation after the Medieval period. The removal of littoral woodlands after the 8th century was followed by the expansion of agrarian and industrial activities. Regional mining and smelting activities polluted the lagoon with heavy metals from the ~11th century onwards. The expansion of the milling industry and of agricultural lands led to the channelization of the river Muga into the lagoon after ~1250 cal AD. This caused its transformation into a freshwater lake, increased nutrient load, and the infilling and drainage of a great part of the lagoon. By tracking the shift towards an anthropogenically-controlled system around ~750 yr ago, this study points out Mediterranean lagoons as ancient and heavily-modified systems, with anthropogenic impacts and controls covering multi-centennial and even millennial timescales. Finally, we contributed to the future construction of reliable seashell-based chronologies in NE Spain by calibrating the Banyuls-sur-Mer ΔR offset with ceramic imports from the Emporiae archaeological site. [ABSTRACT FROM AUTHOR]

This work examines the geochemical behavior of dissolved aluminum in sulfate-rich acidic waters. Our observations were obtained during several years of geochemical and mineralogical research in the San Telmo acidic pit lake and other pit lakes of SW Spain. The work includes scanning and transmission electron microscopy (SEM, TEM) of suspended mineral colloids found in deep lake waters. Energy dispersive spectroscopy (EDS) coupled to scanning and high resolution transmission electron microscopy (STEM, HRTEM) revealed not only the presence and formation of discrete, sub-micron Al solids like alunite, but also the abundance and distribution of Al into Fe(III) phases typical of acid mine drainage, such as schwertmannite and jarosite, at a nanometric resolution. The main conclusion emerging from our work is that the fate and transport of Al at low pH (<4.0) can be largely influenced by adsorption on and/or coprecipitation with both schwertmannite and jarosite. Under the geochemical conditions studied (SO 4 2− = 10 −2 M, Fe(III) ∼ Al = 10 −3 M), alunite formation may occur at pH > 3.3, as suggested by mineralogical observations and geochemical modelling. Below this pH, and contrary to the extended assumption, Al is not truly conservative, and in the presence of ferric iron, both metals may co-precipitate at a substantial extent to form either particles of Al-rich schwertmannite (containing up to ca. 8 at.% Al with [Fe/(Fe + Al)] = 0.77) and/or crystals of H 3 O + - to K + -jarosite (containing up to ca. 10 at.% Al with [Fe/(Fe + Al)] = 0.54). This Al incorporation seems to take place by adsorption on particle surfaces in schwertmannite and by atomic substitution for Fe 3+ in jarosite. Alunite is also unstable at this low pH range with respect to jarosite, which may lead either to isomorphic transformation and/or to chemically zoned crystals with jarositic rims around previously formed alunite cores. As a whole, the compositional spectrum of the analyzed jarosites and alunites describes a discontinuous, coupled (Al 3+ –Fe 3+ , H 3 O + –K + ) solid solution series with an apparent gap at intermediate compositions. However, this gap seems to follow geochemical aspects more than crystallographic factors (i.e., immiscibility). The combination of this macroscopically invisible Al incorporated into Fe(III) solids along with subordinate alunite formation may cause significant Al removal even at very low pH (e.g., 20% decrease in Al concentration in San Telmo at pH < 3.1). Furthermore, this Fe(III)–Al co-precipitation may also affect the fate of toxic trace elements like As and Pb. [ABSTRACT FROM AUTHOR]

The Barranco (creek) León section is located in the NE marginal area of the lacustrine Plio-Pleistocene Baza Basin (Southern Spain). The Barranco León BL-5D mammal and archeological site has delivered abundant lithic tools and a hominin tooth; the age ascribed to this site is comprised between the Olduvai and Jaramillo subchrons, close to 1.4 Ma, based on magnetostratigraphy, biostratigraphy and ERS dating. The studied BL-5 section consists from base to top, of dark sandy mudstones and lutites with interbedded sandy marls. The lower part of the dark sandy mudstones contains a brackish fauna of foraminifera, ostracods, and mollusks. Sandy carbonate mudstones and sandy lutites with freshwater-oligosaline ostracods and mollusks form the upper part of the archeological excavation sequence. Stable isotope (δ 13 C, δ 18 O) and trace element analyses on ostracod and mollusk shells allow depicting the paleoenvironmental conditions recorded in the lacustrine sequence. Moreover, indications on provenance for waters have been obtained from 87 Sr/ 86 Sr ratios from shells and opercula from mollusks. The isotopic composition of the biogenic carbonates shows a strong correlation between δ 13 C and δ 18 O, which is noticeable for some gastropod shells. This correlation is a characteristic feature of closed lake settings. In our case, the more negative isotopic values reflect the input of meteoric waters and the more positive ones the skeletal carbonates formed in more isotopically concentrated waters. Some of the more negative isotopic values correspond to biogenic carbonates from the BL-5D level. They correspond to isotopically diluted waters, although the trace element data and the invertebrate fauna indicate oligosaline to mesosaline waters. Moreover, the presence in BL-5D of shells from Melanopsis tuberculata , a thermophilous gastropod, together with their isotopic signatures suggest the input of oligosaline waters with a thermal influence. The available geochemical data indicate a first stage of varying influence of several water types under changing water level in a closed lake recorded in the base of the studied sequence (brackish fauna level). The overlying beds record a through flowing open lacustrine environment mainly fed by meteoric surface and ground waters with significant inputs of stream waters. [ABSTRACT FROM AUTHOR]

A series of uncharacterised tufa deposits within the lowland volcanic provinces of western Saudi Arabia are investigated here in order to account for their presence and to examine their utility as a palaeoenvironmental archive. The Wadi Dabsa basin, in the Harrat Al Birk, is part of the Saharo-Arabian region, where there is increasing evidence for multiple hominin dispersals during windows of reduced aridity during the last ~400 ka of the Late Quaternary. This first and detailed petrological and geochemical characterisation of these tufa carbonates is particularly important for palaeoenvironmental and climatological reconstruction at a site that contains a major concentration of Early and Middle Stone Age artefacts. We aim to determine the nature of deposition, to answer whether these are cool, freshwater tufa or hydrothermal travertine, and to establish what the tufa settings, stratigraphies and facies reveal about the hydroclimatic regime in this semi-arid environment. A widespread lacustrine-paludal and fluvial tufa system is preserved, as well as topographically-controlled tufa barrages and cascades. Observable sections, exposed by incision, reveal a thickness of tufa deposits of 3 to 6 m in places, which contain two packages of tufa-cemented conglomerate facies. This allows us to provide a conceptual model for the deposition of semi-arid tufa, based on existing type sites in the Naukluft Mountains of Namibia and the Ebro Basin of Spain. The varied topography within this volcanic harrat provides a setting at Wadi Dabsa that combines the low-lying lacustrine-paludal model from Spain with the steeper and higher-energy model from Namibia. The two tufa-cemented bedload units and the evidence for post-depositional erosion of other tufa facies indicates a shifting hydroclimatic regime, with episodes during which the basin contained water and there was steady flow in the fluvial channels, alternating with episodes of high-energy flashy flows. Geochemical analysis using 87Sr/86Sr isotopic ratios (0.7049 to 0.7056 with one sample at 0.7062) and stable carbon isotopes (−12.9 to −6.3‰) reveal that these are cool-water tufas were deposited from meteoric water that has interacted with both metamorphosed limestone in the Asir Escarpment and the mafic metavolcanic bedrock of the Wadi Dabsa Basin, without a geothermal influence. These tufa are low-concentration‑magnesium calcite, with traces of quartz (to a maximum of 3%) and other silicates. Some samples have ≤7.5% palygorskite, which along with petrological evidence for microbial filaments suggests the importance of biomineralisation by cyanobacteria within some of these tufa. Petrological analysis shows the fabrics are dominated by micrite cements with some microspar, and very little post-depositional alteration. Where samples are banded, this reflects variation in calcite crystal size as opposed to any striking variations in mineralogical composition. Oxygen stable isotopic composition (−14.6 to −1.9‰) indicates deposition from an isotopically more depleted rainfall source than the modern day, noting additional corrections for unknown past temperature and any other fractionation effects are needed. Depleted rainfall sources in this region may relate to either a far-travelled Atlantic moisture source or a higher-intensity Indian Ocean monsoon source, or some combination. • The extensive terrestrial carbonates at Wadi Dabsa are ambient, cool, meteoric water-derived, and not hydrothermal. • These tufa precipitated in a fluvio-lacustrine-palustrine system with a mosaic of sub-habitats. • The stratigraphy shows repeated hydroclimatic shifts from ponded conditions, to occasional high-magnitude flash floods. • Tufa δ18O suggests the moisture for past wetter phases was from a more-depleted source than current precipitation. • The now semi-arid, water-free Wadi Dabsa basin would have provided an attractive habitat for prey and ancient humans. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the hydrogeochemical parameters of the Palomares-Carboneras active fault zones (SE Spain) aquifers to establish especially sensitive sampling points that could be indicators of seismic activity in the fault zone. We consider these points as a part of a network, for this fault area and others in the South of Spain. With a seasonal and/or continuous sampling, in the future, that may allow us to provide advices of possible seismic events. The eastern part of the Betic Cordillera is a Mediterranean semi-arid zone, with a special sensitivity to climatic fluctuations and human activity. A remarkable scarcity in water resources is evident in this region, making it difficult to find groundwater sampling points. Subsequently, a network has been designed with 33 water sites, selected for availability and proximity to the active fault zones, where the physical-chemical features and isotope contents of the groundwater have been determined. Taking into account the geological complexity, as well as the different hydrogeological paths recognized in the area, three geochemical families of water have been found. (1) Water with high electrical conductivity (up to 14,000 μS/cm), temperatures above 20 °C, and, in some cases, traces of boron. (2) Water with medium electrical conductivity (2,000-3,500 μS/cm), temperatures above 20 °C, and traces of boron. (3) Water with electrical conductivity below 1,000 μS/cm, temperatures below 20 °C, and absence of boron. High temperature waters with presence of boron were selected as indicators of deep water circulation processes that can be connected to the seismic activity of the Palomares-Carboneras active fault zones. According to this study, a selected sensible warning aquifer sites has been established. [ABSTRACT FROM AUTHOR]

A joint geochemistry and magnetotellurics survey was carried out in the southern volcanic rift zone of Tenerife (Canary Islands, Spain) covering an area ∼100 km 2 for geothermal exploration purposes. Soil CO 2 and H 2 S diffuse effluxes, 222 Rn and 220 Rn activities, soil He, H 2 , N 2 , CO 2 , O 2 and H 2 S concentrations and isotopic composition of CO 2 were measured in 557 selected sampling sites. Magnetotelluric survey (MT) was carried out in the northern part of the study area. A total of 47 MT sites were surveyed and a new 3-D resistivity model was obtained. The observed geochemical anomalies at the soil surface have allowed the detection of areas of deep-seated gas emanations as well as the identification of high vertical permeability volcano-tectonic features in the study area. The resistivity distribution model shows a prominent low-resistivity structure interpreted as a clay alteration cap of variable thickness that might play a role on the mechanism of upward motion of deep-seated gases from the volcano-geothermal system. This is supported by positive correlation between thickness of clay alteration cap and helium emission. [ABSTRACT FROM AUTHOR]

The deep seated xenolith association exhumed in the Pliocenic volcano of Tallante (Betic Cordillera, Spain) includes protogranular mantle peridotites, felsic (metasedimentary) crustal rocks, as well as cumulus igneous rocks such as norites and amphibole (± phlogopite)-clinopyroxenites. The whole xenolith suite equilibrated at the same pressure (0.7–0.9 GPa) representing the local crust–mantle boundary (MOHO) characterized by extreme lithological heterogeneity. This heterogeneity resulted from orogenic processes that induced the juxtaposition of crustal rocks (variably depleted in fusible components) within mantle domains including metasomes, as it is commonly observed in orogenic mantle massifs of the Mediterranean area. In this contribution, we report new mineral compositions of igneous parageneses recorded in these xenoliths, and we present Sr–Nd isotope data on both igneous and metasedimentary xenoliths that integrate those from the literature. Sr–Nd isotopes coherently indicate a restitic character of the metasedimentary xenoliths, which according to model ages were affected by partial melting in Paleozoic times. Sr–Nd isotopic errorchrons on the igneous xenoliths, on the other hand, qualitatively indicate Tertiary ages, which are corroborated by U–Pb zircon datings of one norite xenolith and two composite xenoliths having zircon-bearing norite veinlets. The new data are discussed proposing that MOHO lithologies of Tallante could provide significant source compositions for the genesis of the Neogene volcanics of the Betic area, which included calcalkaline lavas as well as more potassic products such as lamproites. [ABSTRACT FROM AUTHOR]