Hydrogeochemical variability of the acidic springs in the Rio Tinto headwaters

This research was funded by MICINN grant PID2019-1048126GB-I00.Peña de Hierro, located in southwest Spain, encompasses the springs and headwaters for the Rio Tinto River that emerge above normal faults and has been mined for its rich sulfide ore since 2500 BC. The springs are typically characterized by an orange coloration, typical pH of ~2.33, and contain elevated concentrations of heavy metals that are produced by acid rock drainage (ARD). ARD is a natural phenomenon that results from chemolithoautotrophs metabolizing the sulfide ore. Mining has amplified the magnitude of the acidity and concentrations of heavy metals evidenced within sedimentary cores from the Huelva estuary. Acidity, redox state, hydrochemistry and isotopic analyses were examined for the purpose of characterizing the subsurface flows and determining the interconnectivity of the groundwaters. Previous studies have documented the geochemistry of the springs, dating a select few, yet many springs remain uncharacterized. Acidity presented spatial variability throughout the field area, caused by extensive sulfide interactions which generated and modified the pH. Redox exhibited a large range of values due to oxygen diffusivity though the fracture network. The surrounding geology is highly heterogeneous because of intensive deformation during the Variscan and Tertiary periods, and this heterogeneity is shown in the varied aqueous chemistry. Fractionation patterns observed in δ2H and δ18O values predominantly reflected enrichment by intensive evaporation and depletion in δ18O as a result of the proposed sulfatic-water model for Rio Tinto’s hydrogeology. The analysis illustrates minimal hydrologic interconnectivity, evidenced by the extensive physical and chemical contrasts within such a small proximity.Publisher PDFPeer reviewe

Astrobiological field campaign to a volcanosedimentary mars analogue methane producing subsurface protected ecosystem: Imuruk Lake (Alaska)

Viking missions reported adverse conditions for life in Mars surface. High hydrogen signal obtained by Mars orbiters has increased the interest in subsurface prospection as putative protected Mars environment with life potential. Permafrost has attracted considerable interest from an astrobiological point of view due to the recently reported results from the Mars exploration rovers. Considerable studies have been developed on extreme ecosystems and permafrost in particular, to evaluate the possibility of life on Mars and to test specific automated life detection instruments for space missions. The biodiversity of permafrost located on the Bering Land Bridge National Preserve has been studied as an example of subsurface protected niche of astrobiological interest. Different conventional (enrichment and isolation) and molecular ecology techniques (cloning, fluorescence >in situ> probe hybridization, FISH) have been used for isolation and bacterial identification.The expedition to Imuruk Lake was supported by Centro de Astrobiologia-INTA (Spain). The laboratory experimental procedures were supported by Grant AYA 2010–2013 “Desarrollo de Tecnología para la identificación de vida de forma automática” from the Spanish Government.Peer Reviewe

Microbial mediated formation of Fe-carbonate minerals under extreme acidic conditions

Discovery of Fe-carbonate precipitation in Rio Tinto, a shallow river with very acidic waters, situated in Huelva, South-western Spain, adds a new dimension to our understanding of carbonate formation. Sediment samples from this low-pH system indicate that carbonates are formed in physico-chemical conditions ranging from acid to neutral pH. Evidence for microbial mediation is observed in secondary electron images (Fig. 1), which reveal rod-shaped bacteria embedded in the surface of siderite nanocrystals. The formation of carbonates in Rio Tinto is related to the microbial reduction of ferric iron coupled to the oxidation of organic compounds. Herein, we demonstrate for the first time, that Acidiphilium sp. PM, an iron-reducing bacterium isolated from Rio Tinto, mediates the precipitation of siderite (FeCO3) under acidic conditions and at a low temperature (30°C). We describe nucleation of siderite on nanoglobules in intimate association with the bacteria cell surface. This study has major implications for understanding carbonate formation on the ancient Earth or extraterrestrial planets.European research project ERC-250350/IPBSL. A.S.-N.acknowledges support from the P11-RNM-7067 (Junta de Andaluc a-C.E.I.C.-S.G.U.I.T.) projectPeer Reviewe

Orbital evidence for clay and acidic sulfate assemblages on Mars based on mineralogical analogs from Rio Tinto, Spain

Outcrops of hydrated minerals are widespread across the surface of Mars, with clay minerals and sulfates being commonly identified phases. Orbitally-based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy, although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes. Reflectance spectra for previously identified deposits in Ius and Melas Chasma within the Valles Marineris, Mars, exhibit an enigmatic feature with two distinct absorptions between 2.2 and 2.3 µm. This spectral ‘doublet’ feature is proposed to result from a mixture of hydrated minerals, although the identity of the minerals has remained ambiguous. Here we demonstrate that similar spectral doublet features are observed in airborne, field, and laboratory reflectance spectra of rock and sediment samples from Rio Tinto, Spain. Combined visible-near infrared reflectance spectra and X-ray diffraction measurements of these samples reveal that the doublet feature arises from a mixture of Al-phyllosilicate (illite or muscovite) and jarosite. Analyses of orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) shows that the martian spectral equivalents are also consistent with mixtures of Al-phyllosilicates and jarosite, where the Al-phyllosilicate may also include kaolinite and/or halloysite. A case study for a region within Ius Chasma demonstrates that the relative proportions of the Al-phyllosilicate(s) and jarosite vary within one stratigraphic unit as well as between stratigraphic units. The former observation suggests that the jarosite may be a diagenetic (authigenic) product and thus indicative of local pH and redox conditions, whereas the latter observation may be consistent with variations in sediment flux and/or fluid chemistry during sediment deposition.Organismic and Evolutionary Biolog

Protection of Possessors in Classical Roman Law -From the Viewpoint of Buyer Protection- (2)

We studied the formation of Mg-rich carbonate in culture experiments using different aerobic bacterial strains and aqueous Mg/Ca ratios (2 to 11.5) at Earth surface conditions. These bacteria promoted the formation of microenvironments that facilitate the precipitation of mineral phases (dolomite, huntite, high Mg-calcite and hydromagnesite) that were undersaturated in the bulk solution or kinetically inhibited. Dolomite, huntite, high Mg-calcite, hydromagnesite and struvite precipitated in different proportions and at different times, depending on the composition of the medium. The Mg content of dolomite and calcite decreased with an increasing Ca concentration in the medium. The stable carbon isotope composition of the Mg-rich carbonate precipitates reflected the isotope composition of the organic compounds present in the media, suggesting that microbial metabolism strongly influenced the carbon isotope composition of biomediated carbonates. We observed that Ca-enriched carbonate precipitates have relatively low carbon isotope composition. These results provide insights into the mechanism(s) of carbonate formation in natural systems, and they are of fundamental importance for understanding modern environments in which carbonate minerals form as a window into the geologic past

Geobiology of a lower Cambrian carbonate platform, Pedroche Formation, Ossa Morena Zone, Spain

The Cambrian Pedroche Formation comprises a mixed siliciclastic-carbonate succession recording subtidal deposition on a marine platform. Carbonate carbon isotope chemostratigraphy confirms previous biostratigraphic assignment of the Pedroche Formation to the Atdabanian regional stage of Siberia, correlative to Cambrian Series 2. At the outcrop scale, thrombolitic facies comprise ~. 60% of carbonate-normalized stratigraphy and coated-grains another ~. 10%. Petrographic point counts reveal that skeletons contribute at most 20% to thrombolitic inter-reef and reef-flank lithologies; on average, archaeocyath clasts make up 68% of skeletal materials. In contrast, petrographic point counts show that skeletons comprise a negligible volume of biohermal and biostromal thrombolite, associated nodular carbonate facies, and ooid, oncoid and peloid grainstone facies. As such, archaeocyathan reefal bioconstructions represent a specific and limited locus of skeletal carbonate production and deposition. Consistent with data from coeval, globally dispersed lower Cambrian successions, our analysis of the Pedroche Formation supports the view that lower Cambrian carbonates have more in common with earlier, Neoproterozoic deposits than with younger carbonates dominated by skeletal production and accumulation. © 2013 Elsevier B.V.Jessica R. Creveling, David Fernández-Remolar, Marta Rodríguez-Martínez, Silvia Menéndez, Kristin D. Bergmann, Benjamin C. Gill, John Abelson, Ricardo Amils, Bethany L. Ehlmann, Diego C. García-Bellido, John P. Grotzinger, Christian Hallmann, Kathryn M. Stack, Andrew H. Knol

Los microfósiles problemáticos del Cámbrico Inferior de la Sierra de Córdoba: datos preliminares

El ataque químico de materiales procedentes de la Sierra de Córdoba y pertenecientes al Cámbrico Inferior, ha dado lugar a la obtención de microfósiles problemáticos de macroorganismos consistentes, fundamentalmente, en tubos de naturaleza fosfática y moldes internos fosfatizados. En este trabajo se resumen los datos preliminares del estudio taxonómico, bioestratigráfico y paleobiogeográfico de los microfósiles obtenidos. [ABSTRACT] The chemical disolution of Lower Cambrian limestones from Sierra de Córdoba have allowed to obtain small shelly fossils consisting in phospbatic tubes and phosphatized inner moulds of selerites. This work deals with preliminary dates of the taxonomic, biostratigraphic and paleobiogeographic study of the microfossils found

Problematic fossils from Lower Cambrian of Sierra de Córdoba: preliminary dates

[ES] El ataque químico de materiales procedentes de la Sierra de Córdoba y pertenecientes al Cámbrico Inferior, ha dado lugar a la obtención de microfósiles problemáticos de macroorganismos consistentes, fundamentalmente, en tubos de naturaleza fosfática y moldes internos fosfati¿ados. En este trabajo se resumen los datos preliminares del estudio taxonómico, bioestratigráfico y paleobiogeográfico de los microfósiles obtenidos.[EN] The chemical disolution of Lower Cambrian limestones from Sierra de Córdoba have allowed to obtain small shelly fossils consisting in phospbatic tubes and phosphatized inner moulds of selerites. This work deals with preliminary dates of dic taxonomie, hiostratigraphic and paleobiogeographic study of the microfossils found.Este trabajo se ha realizado en el marco del proyecto PB9O-0593-C02-02.Peer reviewe