Search

Soil serves as a repository of human history, preserving artifacts within its horizons. However, the presence of chemically reactive remnants, such as ancient slags, can significantly impact the surrounding soil environment. This paper addresses this scarcely explored issue by focusing on soil contamination arising from pre-Roman slag deposits at the Monte Romero archaeological site in southwest Spain, dating back to the Tartessian period (c. 7th century BC). Through the high-resolution microscopy examination of slag wastes and the trace element analysis of soil samples by ICP-OES, this study evaluated current contamination status using a multi-index approach. The results revealed markedly high levels of Pb (>5000 mg kg−1), Cu (up to 2730 mg kg−1), and As (up to 445 mg kg−1) in the soil compared to a control sample. The identification of secondary complex compounds like Cu arsenates and Pb arsenates/antimonates within slag cavities suggests post-depositional weathering processes, leading to the dispersion of potentially toxic elements into the surrounding soil. Assessments through indices of contamination and potential ecological risk highlighted severe contamination, particularly concerning Ag, Pb, Sb, Cu, and As. This study underscores the importance of addressing potential environmental hazards associated with archaeological sites hosting remnants of metal production. [ABSTRACT FROM AUTHOR]

The Iberian Pyrite Belt (IPB) represents one of the largest districts of volcanogenic massive sulfide (VMS) deposits in the world, and is a critical source of base metals (Cu, Pb, and Zn) for Europe. Confirmed resources exceed 1700 Mt of massive sulfides with grades of around 1.2% Cu, 1% Pb, and 3% Zn as well as more than 300 Mt of stockwork-type copper mineralization. Significant resources of Sn, precious metals (Au and Ag), and critical metals (Co, Bi, Sb, In, and Se) have also been evaluated. The genesis of these deposits is related to a complex geological evolution during the late Devonian and Mississippian periods. The geological record of such evolution is represented by three main lithological units: Phyllite–Quartzite Group, the volcano–sedimentary Complex (VSC), and the so-called Culm Group. The sulfide deposits are located in the VSC, associated with felsic volcanic rocks or sedimentary rocks such as black shales. The massive sulfide deposits occur as tabular bodies and replacement masses associated with both volcanic and sedimentary rocks. Their mineralogical composition is relatively simple, dominated by pyrite, chalcopyrite, sphalerite, and galena. Their origin is related to three evolutionary stages at increasing temperatures, and a subsequent stage associated with the Variscan deformation. The present paper summarizes the latest developments in the IPB and revises research areas requiring further investigation. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) generated from coal and sulfide mining has attracted much interest due to the high concentrations of rare earth elements (REE) observed. However, the origin of REE in AMD and particularly the mechanism of enrichment in medium REE remain uncertain. The combined study of Sr and Nd isotopes can be used to trace the processes that control the mobility and fractionation of REE in aquatic systems such as AMD. This work reports for the first time worldwide isotopic data of Sr and Nd in AMDs from sulfide mining (Iberian Pyrite Belt, SW Spain) and compare with those in host rocks. Additionally, leaching experiments have been carried out to simulate the water–rock interactions found in these acidic systems. The results obtained strongly suggest that the origin of REE in AMDs from metal mining may be related to the preferential dissolution of shales and felsic rocks. The suitability of Sr and Nd isotopic signatures to trace the REE source in AMD-affected systems has been proven, it provides a new environmental and geochemical prospecting tool which could be useful in different geological water–rock interaction systems. [ABSTRACT FROM AUTHOR]

The Iberian Pyrite Belt (IPB) is a metallogenic province in SW Spain and Portugal hosting the largest concentration of massive sulfide deposits worldwide. Exploration campaigns in both the Spanish and Portuguese sectors of the IPB have increased recently due to the rise in metal prices. Within this framework, distinguishing geochemical features associated with natural phenomena and isolating geogenic anomalies from anthropogenic ones can pose a challenge. This contribution uses the residual soil geochemical database of the IPB (Spain) to examine numerous variables, encompassing major, minor and trace elements. Some of these variables commonly exhibit high correlations owing to consistent geochemical behaviour. However, the influence of anthropogenic factors tends to elevate data variability, occasionally masking the natural relationships that govern their distributions. We apply different treatments of data to develop factor analysis using log-transformed data, and centred log-ratio (clr) transformed data to compare and improve the geochemical interpretation of this important zone. Factor analysis has been developed with these results to compare with previously published research on factor analysis in raw data. Factor score interpolated maps were also generated using both lognormal and clr-transformed data to visualize better the distribution and the different geochemical associations in the IPB. This study shows the importance of the different data treatments and the improvement of the clr-transformed multivariate analysis to reduce the dilution or overestimation of the results of some elements that cause erroneous interpretations of the data. [ABSTRACT FROM AUTHOR]

This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca. 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 °C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at ca. 356.8 ± 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca. 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (ca. 770 °C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts. [ABSTRACT FROM AUTHOR]

The removal of water from mines was one of the key issues that former miners had to deal with. Roman colonists brought new technology to the Iberian Peninsula that addressed this problem. However, they did not invent this technology because it had already been applied to the growth of other endeavours in the Hellenistic society throughout the Eastern Mediterranean. In the mine, the Archimedes screw, waterwheels, bucket pulleys, and Ctesibius pumps were the primary drainage systems. In this essay, the primary characteristics, and modes of operation of machines are examined. Without leaving out the most significant finds made in the southwest of the Iberian Peninsula, one of the regions with the longest history of mining exploitation. To serve as a foundation for future research in this field, this work compares the primary mining mechanisms in ancient Huelva on a qualitative and quantitative level by the implementation of a TOPSIS methodology, a multi-criteria decision analysis method. [ABSTRACT FROM AUTHOR]

Soil serves as a repository of human history, preserving artifacts within its horizons. However, the presence of chemically reactive remnants, such as ancient slags, can significantly impact the surrounding soil environment. This paper addresses this scarcely explored issue by focusing on soil contamination arising from pre-Roman slag deposits at the Monte Romero archaeological site in southwest Spain, dating back to the Tartessian period (c. 7th century BC). Through the high-resolution microscopy examination of slag wastes and the trace element analysis of soil samples by ICP-OES, this study evaluated current contamination status using a multi-index approach. The results revealed markedly high levels of Pb (>5000 mg kg−1), Cu (up to 2730 mg kg−1), and As (up to 445 mg kg−1) in the soil compared to a control sample. The identification of secondary complex compounds like Cu arsenates and Pb arsenates/antimonates within slag cavities suggests post-depositional weathering processes, leading to the dispersion of potentially toxic elements into the surrounding soil. Assessments through indices of contamination and potential ecological risk highlighted severe contamination, particularly concerning Ag, Pb, Sb, Cu, and As. This study underscores the importance of addressing potential environmental hazards associated with archaeological sites hosting remnants of metal production.

• Devonian-Carboniferous sedimentation and paleoenvironments along the Iberian Pyrite Belt are analysed. • Several stratigraphic hiatuses are identified and confirmed in the Neves-Corvo region. • Palynostratigraphy is an important tool to define the age of the black shales hosting the mineralization. • IPB bioevents related to the major extinction event and environment changes are documented in the Devonian-Carboniferous Boundary. • Improvement of the stratigraphy of the IPB and geological knowledge. Based on drill hole sampling and sedimentary rock dating by palynology, the present research focuses on the palynostratigraphic events established in the key geological section of Guedelhinha–Lançadoiras–Algaré located in the Portuguese Neves–Corvo mine region, Iberian Pyrite Belt. The age data allow detailing the lithostratigraphic sequence and further understanding the complex structural setting, representing an important contribution to the geological knowledge of this sector located to the immediate WNW of the Neves–Corvo VMS deposit. The combination of the studied events allows the reconstruction of the Devonian-Carboniferous sedimentation and paleoenvironments along the Iberian Pyrite Belt. Several stratigraphic hiatuses identified in the Neves–Corvo region by the palynological record are confirmed, mainly occurring from the mid Frasnian to mid Famennian, from the early and mid Strunian, and from the early to late Tournaisian, which were mainly coincident with the worldwide extinction events, in particular during Frasnian–Famennian and Late Devonian times. Extensional tectonics and related gravitational faults, local uplift mechanisms and intense volcanic activity could also explain the lack of palynological data and sedimentary hiatus. In this research, the importance of the late Strunian times in the Iberian Pyrite Belt (Miospore Biozone LN of the Neves Formation) is highlighted, confirming the contemporaneity of felsic volcanism, hydrothermalism, sulphide mineralization precipitation and black shale anoxic sedimentation. [ABSTRACT FROM AUTHOR]

Microbial diversity that thrives in the deep subsurface remains largely unknown. In this work, we present the characterization of Citrobacter sp. T1.2D-1, isolated from a 63.6 m-deep core sample extracted from the deep subsurface of the Iberian Pyrite Belt (IPB). A genomic analysis was performed to identify genes that could be ecologically significant in the IPB. We identified all the genes that encoded the formate–hydrogen lyase and hydrogenase-2 complexes, related to hydrogen production, as well as those involved in glycerol fermentation. This is particularly relevant as some of the substrates and byproducts of this process are of industrial interest. Additionally, we conducted a phylogenomic study, which led us to conclude that our isolate was classified within the Citrobacter telavivensis species. Experimentally, we verified the strain's ability to produce hydrogen from glucose and glycerol and, thus, of performing dark fermentation. Moreover, we assessed the activity of the nitrate and tetrathionate reductase complexes and the isolate's ability to tolerate high concentrations of heavy metals, especially Zn. These results suggest that C. telavivensis T1.2D-1 can play a role in the carbon, hydrogen, iron, nitrogen, and sulfur cycles that occur in the deep subsurface of the IPB, making it a candidate worthy of further study for possible biotechnological applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A probable genetic link of volcanic and intrusive rocks in the IPB genesis in space and time. • Volcanism has migrated in time, from west to east at the province scale showing an inter-axis and intra-axis time–space dependency. • The one-direction volcanism (SW/W-NE/E) can be explained by a plate motion over a deep heat source. • The NW/W-SE/E volcanic activity along each axis seems to be tectonically controlled. The volcanism in the Iberian Pyrite Belt migrated from the present day west/southwest to the east/northeast during Devonian/Carboniferous times. Evidence is here discussed based in U-Pb zircon ages of felsic volcanic and plutonic rocks, bounded by enclosed sediments and their biostratigraphic ages, together with hosted massive sulphides deposits and associated plutonic counterparts. Volcano-Sedimentary Complex rocks define several volcanic axes, or lineaments, with the general NW-SE to WNW-ESE belt trending orientation. The usage of all the available data from high-resolution stratigraphy, geology and geophysics lead to establishment of eleven main volcanic axes, nine with zircon U-Pb radiometric ages (166 samples). In this research, we reinforce a previous inter-axes volcanic evolutionary trend, but we also suggest an intra-axis evolutionary trend of the IPB igneous activity with time. This means the basin igneous activity also evolved along most of the volcanic and plutonic lineaments, from west/northwest to east/southeast. Successive weighted average ages for each axis (SW to NE) and opposite end-point sample ages for each axis (NW/W to SE/E) are presented. Similar trends are found with felsic volcanic rocks, subvolcanic and plutonic rocks and even massive sulphide ages correspond to the regional trend corroborating the proposed geological framework. Siliciclastic sediments and lower VSC sequences (sediments, felsic volcanic rocks and massive sulphides) show a comparable age trending evolution although upper VSC sediments seem to be contemporaneous across the province. Older ages, from zircon U-Pb and from associated reworked palynomorph in the sediments, show a long-lasting age distribution along most Devonian times, suggesting the IPB evolved since Lochkovian times (Lower Devonian). Therefore, we propose the IPB inter-axes evolution could be related with a NE-direction plate motion (present-day location) over a heat source, while intra-axes are probably due to the collisional/compressive tectonic interaction of South Portuguese – Ossa-Morena zones tectonic setting. [ABSTRACT FROM AUTHOR]

The Iberian Pyrite Belt (IPB), in the southwestern Iberian Peninsula, is a large metallogenic province exploited since ancient times. As a result of historical and current mining activity, a vast volume of metallic mineral waste, mainly derived from the processing of pyrite, is still in situ and polluting the environment. A specific mine waste residuum locally known in the area as "morrongos", which was produced during pyrite roasting mainly in the 19th century, is evaluated here in order to unravel untapped resources of high-tech metals commonly used in high-tech devices. Applying a combination of whole-rock geochemical (ICP-AES, ICPMS, FA-AAS) and single-grain mineralogical techniques (EPMA, LA-ICP-MS, FESEM, and FIB-HRTEM) on the "morrongos", we unhide the still-present remarkable concentrations of Au, Ag, Pb, Zn, and Cu in them. The mineralogical expressions for these economic metals include oxides (hematite, magnetite, and hercynite), arsenates, sulfates of the jarosite group, native metals, and, to a lesser extent, relictic sulfides. This first-ever estimation of these economic metals in this type of residue allows their revalorization, highlighting them as suitable sources for the exploitation and recovery of metals necessary for the clean energy transition. [ABSTRACT FROM AUTHOR]

Vitamin B12 is an enzymatic cofactor that is essential for both eukaryotes and prokaryotes. The development of life in extreme environments depends on cofactors such as vitamin B12 as well. The genomes of twelve microorganisms isolated from the deep subsurface of the Iberian Pyrite Belt have been analyzed in search of enzymatic activities that require vitamin B12 or are involved in its synthesis and import. Results have revealed that vitamin B12 is needed by these microorganisms for several essential enzymes such as ribonucleotide reductase, methionine synthase and epoxyqueosine reductase. Isolate Desulfosporosinus sp. DEEP is the only analyzed genome that holds a set core of proteins that could lead to the production of vitamin B12. The rest are dependent on obtaining it from the subsurface oligotrophic environment in which they grow. Sought proteins involved in the import of vitamin B12 are not widespread in the sample. The dependence found in the genomes of these microorganisms is supported by the production of vitamin B12 by microorganisms such as Desulfosporosinus sp. DEEP, showing that the operation of deep subsurface biogeochemical cycles is dependent on cofactors such as vitamin B12. [ABSTRACT FROM AUTHOR]

Mineralogical analysis and laboratory-based leaching tests coupled with speciation modeling were undertaken to quantify the potential for short-term acid generation and the release of trace elements from soils heavily contaminated with mine waste at Rio Tinto. Three different waste materials were considered as case studies: roasted pyrite, copper slags, and leached sulfide ores. The results showed elevated values of net acid generation (up to 663 mmol H+/kg), the major pools being potential sulfidic acidity and acidity retained in jarosite. Remarkable contents of As and toxic heavy metals were found especially in the slag-contaminated soil. Copper, Zn, and Pb were the most abundant metals in the acid leach solutions resulting from mine soil-water interaction, with peak values of 55.6 mg L−1, 2.77 mg L−1, and 2.62 mg L−1, respectively. Despite the high total contents of trace elements occurring in soil, the mobile fraction was limited to maximum release values of 12.60% for Cd and 10.27% for Cu, according to the test leaching. Speciation calculations indicated that free metal ions (M2+) and sulfate species (MSO40) accounted for most of the dissolved load. Acid soil drainage is a secondary source of acid and heavy metals in the mine site and, therefore, an effective land reclamation program should ensure that acidity and metal mobility are reduced to environmentally sustainable levels. [ABSTRACT FROM AUTHOR]

Abandoned mining railways are a prominent legacy environmental issue facing many metalliferous regions with a long mining history. However, there is a general lack of information on potentially hazardous trace elements occurring in soils alongside railroad lines as a result of hazmat cargo spills. This paper explores for the first time the effects of pyrite ore transportation on soil pollution along the old railways of Tharsis and Rio Tinto, two historical mining districts of world-class importance in the Iberian Pyrite Belt. The railroad-side topsoil was found to be extremely acidic in reaction and contains abundant pyrite, spilled on the tracks during transit, and its oxidation products (jarosite, iron oxyhydroxides, and efflorescent sulfate minerals). Compared to local background concentrations, highly elevated levels of Pb, Zn, Cu, As, Hg, Sb, Bi, Cd, Ag, and Tl were detected in both railroad lines, indicating serious anthropogenic contamination. Exposure to soil contaminants, notably Pb, As, and Tl, could pose hazards to human health and the environment. Accordingly, a specific-site risk assessment is needed before the mining railway lines are converted into recreational trails. [ABSTRACT FROM AUTHOR]

Microbial diversity that thrives in the deep subsurface remains largely unknown. In this work, we present the characterization of Citrobacter sp. T1.2D-1, isolated from a 63.6 m-deep core sample extracted from the deep subsurface of the Iberian Pyrite Belt (IPB). A genomic analysis was performed to identify genes that could be ecologically significant in the IPB. We identified all the genes that encoded the formate–hydrogen lyase and hydrogenase-2 complexes, related to hydrogen production, as well as those involved in glycerol fermentation. This is particularly relevant as some of the substrates and byproducts of this process are of industrial interest. Additionally, we conducted a phylogenomic study, which led us to conclude that our isolate was classified within the Citrobacter telavivensis species. Experimentally, we verified the strain’s ability to produce hydrogen from glucose and glycerol and, thus, of performing dark fermentation. Moreover, we assessed the activity of the nitrate and tetrathionate reductase complexes and the isolate’s ability to tolerate high concentrations of heavy metals, especially Zn. These results suggest that C. telavivensis T1.2D-1 can play a role in the carbon, hydrogen, iron, nitrogen, and sulfur cycles that occur in the deep subsurface of the IPB, making it a candidate worthy of further study for possible biotechnological applications.

Located in the Iberian pyrite belt, the Neves–Corvo mine is a world-class massive sulfide deposit and the largest operating mine in Portugal with underground mining down to 1000 m depth focused on massive and stockwork Cu, Zn, Pb rich ores. Gravimetric data have had a leading role in the discovery of the seven known deposits, together with time-domain electromagnetic (TEM) ground data. In this work, we present the results of a 3D constrained gravity inversion carried out with legacy ground gravity data. The 3D gravity inversions were carried out using an updated density database containing approximately 142,000 measurements. A recently constructed 3D geological model based on reprocessed 2D seismic reflection, 3D seismic, TEM and updated geology from detailed surface mapping and drill-hole data, was used to constrain the inversions. The results show multiple high-density anomalies that may indicate the presence of mineralization at depth. These anomalies were therefore cross-checked with holes previously drilled. Approximately 97% of more than 1000 available surface drill-holes located on or at a distance of less than 200 m from the high-density anomalies intersected mineralization. However, gravity anomalies have been drilled in the past and particularly dense black shales or rhyolitic/gabbroic rocks have been intersected. To increase the success of future drilling, gravimetric anomalies have been correlated spatially with high-conductivity TEM zones and strong-amplitude seismic reflections, because igneous rocks usually present weak-to-moderate conductivity and a massive column of black shales presents a seismic signature quite different from that of mineralization. We concluded that some of these locations represent high-quality targets to consider following up with drilling and further exploration. [ABSTRACT FROM AUTHOR]

This work focuses on the physical-chemical characterization of a mining effluent affected by acid mine drainage (AMD) from its source to the confluence in the Odiel river, one of the most polluted rivers by AMD worldwide, in order to understand the reactions involved in the modifications in the chemical characteristics of water and precipitates resulting from water–rock–atmosphere interaction in an environment highly affected by mining activity without corrective measures. The channel starts in an open pit lake through one of the Concepción Mine main galleries, located in the Iberian Pyrite Belt, about 10 km northwest of Rio Tinto mining complex (southwest Spain). This gallery intercepts one of the largest and oldest underground mining work locations called "gallery Carmen", allowing the exit of AMD affected waters. This channel is the first AMD polluting source in the Odiel basin. Thus, at the end of the rainy season, we conducted water sampling along this channel, from its source to its mouth, to further analyse its characterization and interpret the cause–effect relationships through the application of Fuzzy Logic and classical statistics tools. The interdependent relationship between the measured physicochemical parameters are set in order to propose a model, capable of describing the evolution of contaminants in response to the processes and reactions taking place within the affected channel and the Odiel river. The present work concluded the existence of natural attenuation processes for the mining channel, despite the entrances of other drainages in the AMD channel with different hydrochemical characteristics imposing modifications on it. This indicates that these media have a high vulnerability to external stimuli. [ABSTRACT FROM AUTHOR]

The recently discovered massive and stockwork sulphide mineralization of Semblana-Rosa Magra and Monte Branco, situated ESE of the Neves–Corvo volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt (IPB) is presented. Geological setting and tectonic model is discussed based on proxies such as palynostratigraphy and U–Pb zircon geochronology. The mineralization is found within the IPB Volcano-Sedimentary Complex (VSC) Lower sequence, which includes felsic volcanic rocks (rhyolites) with U–Pb ages in zircons of 359.6 ± 1.6 Ma, and black shales of the Neves Formation of late Strunian age. Massive sulphides are enveloped by these shales, implying that felsic volcanism, mineralization and shale sedimentation are essentially coeval. This circumstance is considered highly prospective, as it represents an important exploration vector to target VMS mineralization across the IPB, in areas where the Lower VSC sequence is present. The Upper VSC sequence, with siliciclastic and volcanogenic sedimentary rocks of middle–late Visean age, shows no massive mineralization but a late Tournaisian (350.9 ± 2.3 Ma) volcanism with disseminated sulphides was also identified. Nevertheless, stratigraphic palynological gaps were found within the Strunian and in the Tournaisian sediments, between the Lower and Upper VSC sequences, reflecting probable erosion and uplift mechanisms linked with extensional tectonics. The Semblana and Monte Branco deposits and the Rosa Magra stockwork are enclosed by tectonic sheets that dismembered the VSC sequence in a fold-and-thrust tectonic complex, characteristic of the NE Neves–Corvo region. The methodologies used allow a geological comparison between Neves–Corvo and other IPB mine regions such as Lousal–Caveira, Herrerias, Tharsis and Aznalcollar. [ABSTRACT FROM AUTHOR]

This paper explores the possibility of using the lixiviates generated by sulphide mining in the Iberian Pyrite Belt (IPB) as a source of economic interest elements, estimating the available metal reserves and discussing the economic gains that would result from the recovery of this potential source of critical raw materials and other economic interest elements. For this purpose, 33 mining lixiviates have been evaluated. Results show annual contributions of more than 7000 t/year of Mg, 4700 t/year of Al, 3700 t/year of Mn, 34 t/year of Co, 2.3 t/year of Sb, around 24 t/year of rare earth elements (REE), etc. Considering the market metal prices for 2019, the reserves contained in the evaluated lixiviates have a potential value of around 95 million USD; however, this value is largely underestimated. Making an estimate on the total area of abandoned solid waste in the IPB, this value would be increased to an annual total of more than 400 million dollars. [ABSTRACT FROM AUTHOR]

Massive sulfide deposits of the Iberian Pyrite Belt (IPB) document the progression of ore-forming processes in the SW Iberian Variscides, throughout uppermost Devonian to Early Carboniferous. Sulfide ores are usually hosted in volcanic-dominated or shale-dominated successions belonging to the Volcano-Sedimentary Complex (VSC; Late Famennian to Late Visean). Yet, several important orebodies at Neves-Corvo are sitting within upper sections (Famennian) of the early deposited Phyllite–Quartzite Group (PQG). Four key sectors of the Portuguese segment of IPB were revisited and 262 samples collected to characterize the geochemical features of metapelites from PQG and VSC sequences in barren and fertile settings. The selected sectors include active (Neves-Corvo and Aljustrel) and old (Lousal) mines, besides promising brownfield (Gavião) and greenfield (Sesmarias) prospects, and other lithostratigraphic sections without known mineralization. The composition of PQG and VSC metapelites is similar and mainly controlled by a mixture of clayey-derived and quartz sandy-derived components largely resulting from different sources of granitic to granodiorite/quartz diorite composition. A third component of local volcaniclastic origin could be significant in many samples of upper VSC sections. Mineral transformations during diagenesis and/or hydrothermal alteration/mineralization partially overprinted the primary composition. During sedimentation/diagenesis, prevalent redox conditions were mostly confined to oxic environments, at places transiting to sub-oxic. Subsequent multistage interaction with reducing hydrothermal fluids (to which the sulfide mineralization is related) generated heterogeneous anoxic signs. Consistent increases in Fe2O3/TiO2, (Cu + Zn + Pb)/Sc and (As + Sb)/Sc ratios to values above 10 represent a valuable footprint toward ore horizons. [ABSTRACT FROM AUTHOR]

Mining activities have turned many areas of the Iberian Pyrite Belt (IPB) into extreme environments with high concentrations of metal(loid)s. These harsh conditions can inhibit or reduce the colonization and/or development of most vegetation. However, some species or populations have developed ecophysiological responses to tolerate stress factors and contaminated soils. The main objectives of this study are: (i) to assess the differences in germination, growth, development and physiological behaviour against oxidative stress caused by metal(loid)s in Lavandula pedunculata (Mill.) Cav. from two different origins (a contaminated area in São Domingos mine, SE of Portugal and an uncontaminated area from Serra do Caldeirão, S of Portugal) under controlled conditions; and (ii) to assess whether it is possible to use this species for the rehabilitation of mine areas of the IPB. After germination, seedlings from São Domingos (LC) and Caldeirão (L) were planted in pots with a contaminated soil developed on gossan (CS) and in pots with an uncontaminated soil (US) under controlled conditions. Multielemental concentrations were determined in soils (total and available fractions) and plants (shoots and roots). Germination rate, shoot height, dry biomass and leaf area were determined, and pigments, glutathione, ascorbate and H2O2 contents were measured in plant shoots. Total concentrations of As, Cr, Cu, Pb and Sb in CS, and As in US exceed the intervention and maximum limits for ecosystem protection and human health. The main results showed that L. pedunculata, regardless of the seed origin, activated defence mechanisms against oxidative stress caused by high concentrations of metal(loid)s. Plants grown from seeds of both origins increased the production of AsA to preserve its reduction levels and kept the contents of GSH stable to maintain the cell’s redox state. Plants grown from seeds collected in non-contaminated areas showed a high capacity for adaptation to extreme conditions. This species showed a greater growth capacity when seeds from a contaminated area were sown in uncontaminated soils. Thus, L. pedunculata, mainly grown from seeds from contaminated areas, may be used in phytostabilization programmes in areas with soils with high contents of metal(loid)s.

We examined the geochemistry and bacterial and archaeal community structure in the acidic (pH < 2.4) pit lake at Peña de Hierro, near the headwaters of the Río Tinto. The lake has strong vertical gradients in light, O2, pH, conductivity, and dissolved ions. Bacterial and archaeal communities between 0 and 32 m displayed low species richness and evenness. Relatives of iron cycling taxa accounted for 60-90% of the operational taxonomic units (OTUs) throughout the water column. Relatives of heterotrophic, facultative Fe(III)-reducing species made up more than a third of the bacterial and archaeal community in the photic zone. Taxa related to Fe(II) oxidizers Ferrithrix thermotolerans and Acidithix ferrooxidans were also abundant in the photic zone. Below the photic zone, relatives of the lithoautotrophic Fe(II) oxidizers Leptospirillum ferrooxidans and Ferrovum myxofaciens bloomed at different depths within or just below the oxycline. Thermoplasmatales predominated in the deep, microoxic zone of the lake. The microbial population structure of the lake appears to be influenced by the production of oxygen and organic matter by phototrophs in a narrow zone at the lake surface and by strong geochemical gradients present in the water column that create distinct niches for separate Fe(II) oxidizers. [ABSTRACT FROM AUTHOR]

Water is one of the receptors media more affected by the environmental impacts, especially caused by mining sulfides exploitation. Acid mine drainage (AMD) is the main problem associated with these mining operations, producing extremely high impacts, and in many cases irreversible, still remaining nowadays. Diatoms, are the taxonomic algal group most used in environmental studies, to assess the water quality of rivers. From a monitoring perspective, the diagnosis of AMD contamination through the use of diatoms has proved to be an effective ecological tool to assess the impact and select the preventive and corrective measures more adequate to treat these impacted sites. In the present work, the existing relationships between biological and physicochemical indicators of acid mine drainage processes (AMD) in all the reservoirs affected by AMD in the Iberian Pyrite Belt (IPB) were studied through the use of fuzzy logic and data mining techniques that in contrast to the classic statistical treatments. The fuzzy rules show the relationship between biological and physical-chemical indicators, demonstrating the presence of a perfect correlation in all cases; thus, the numbers of species and pH have the same behavior, and inverse to that presented by the percentage of Pinnularia and the metallic charge and sulfates. These techniques improve the work considerably and make easier the knowledge of the involved processes, allowing a better discrimination of the diatoms responses to the stimuli caused by the hydrochemical changes imposed by the processes affecting water quality. [ABSTRACT FROM AUTHOR]

With an increasing demand for raw materials, predictive models that support successful mineral exploration targeting are of great importance. We evaluated different machine learning techniques with an emphasis on boosting algorithms and implemented them in an ArcGIS toolbox. Performance was tested on an exploration dataset from the Iberian Pyrite Belt (IPB) with respect to accuracy, performance, stability, and robustness. Boosting algorithms are ensemble methods used in supervised learning for regression and classification. They combine weak classifiers, i.e., classifiers that perform slightly better than random guessing to obtain robust classifiers. Each time a weak learner is added; the learning set is reweighted to give more importance to misclassified samples. Our test area, the IPB, is one of the oldest mining districts in the world and hosts giant volcanic-hosted massive sulfide (VMS) deposits. The spatial density of ore deposits, as well as the size and tonnage, makes the area unique, and due to the high data availability and number of known deposits, well-suited for testing machine learning algorithms. We combined several geophysical datasets, as well as layers derived from geological maps as predictors of the presence or absence of VMS deposits. Boosting algorithms such as BrownBoost and Adaboost were tested and compared to Logistic Regression (LR), Random Forests (RF) and Support Vector machines (SVM) in several experiments. We found performance results relatively similar, especially to BrownBoost, which slightly outperformed LR and SVM with respective accuracies of 0.96 compared to 0.89 and 0.93. Data augmentation by perturbing deposit location led to a 7% improvement in results. Variations in the split ratio of training and test data led to a reduction in the accuracy of the prediction result with relative stability occurring at a critical point at around 26 training samples out of 130 total samples. When lower numbers of training data were introduced accuracy dropped significantly. In comparison with other machine learning methods, Adaboost is user-friendly due to relatively short training and prediction times, the low likelihood of overfitting and the reduced number of hyperparameters for optimization. Boosting algorithms gave high predictive accuracies, making them a potential data-driven alternative for regional scale and/or brownfields mineral exploration. [ABSTRACT FROM AUTHOR]

Copyright of Comunicaçõe Geológicas is the property of Laboratorio Nacional de Energia e Geologia, I.P. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Comunicaçõe Geológicas is the property of Laboratorio Nacional de Energia e Geologia, I.P. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Comunicaçõe Geológicas is the property of Laboratorio Nacional de Energia e Geologia, I.P. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Comunicaçõe Geológicas is the property of Laboratorio Nacional de Energia e Geologia, I.P. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Comunicaçõe Geológicas is the property of Laboratorio Nacional de Energia e Geologia, I.P. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)