The Borralha area (Iberian Massif, Portugal) reflects a long-lived and multiphase magmatism (ca. ... more The Borralha area (Iberian Massif, Portugal) reflects a long-lived and multiphase magmatism (ca. 316 to 300 Ma), characterized by three types of granite emplacement during two different extensional events (E1 and E2) and one compressional event (C3) within the Variscan orogeny. The W (Cu) mineralization styles correspond to veinlets and quartz veins (i.e., São António and Santa Helena), and disseminations in the Santa Helena breccia pipe. Molybdenite coexists with an Fe-bearing wolframite-quartz assemblage in the Venise breccia pipe and quartz veins (i.e., São José and São Paulo). The geochemistry and geochronology of wolframite and molybdenite samples were studied by electron probe microanalysis (EPMA), in-situ U-Pb laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and Re-Os thermal ionization mass spectrometry (TIMS). The wolframite yields a U-Pb age (sample WBV1) of 315.2 ± 4.7 Ma (2σ), representing the first recognized episode of W deposition in the Iberian Massif. Wolframite samples (WBV1, WB1, and WB4) have a ferberite composition with a hübnerite/ferberite ratio of < 29. High amounts of Nb (up to 3703 ppm) with low Ta (up to 123 ppm) and REEs (up to 11.4 ppm) and conversely, low amounts of Nb (up to 471 ppm) with high Ta (up to 190 ppm) and REEs (up to 53.7 ppm) were measured in wolframite samples. The REEs normalized patterns of the wolframite samples record a mixed signature. Large and positive Eu/Eu* and Er/Er* anomalies were identified (sample WBV1), whereas negative Ce/Ce* and Nd/ Nd* anomalies were observed in samples WB1 and WB4. Molybdenite Re-Os dating yields absolute ages ranging from 305.1 to 303.8 ± 2.2 Ma (2σ), which are coeval with the emplacement of E2 biotite granite (Penedos; I-type; <305 Ma). Low amounts of Re (<1 ppm), W, Co, Ni, As, Cu, Bi, Fe, Mn V and Se (<0.005 wt%) were detected in the molybdenite structure. Constraints between the timing of Wand Mo-deposition and a protracted cooling history of the host rocks are confirmed by 40 Ar/ 39 Ar white mica dating. The 40 Ar/ 39 Ar ages obtained for secondary white micas collected from Mo veins (Venise breccia pipe; 277 ± 3 and 287 ± 4 Ma 2σ) and W (Cu) dissemination (Santa Helena breccia pipe; 287 ± 2 and 279.0 ± 6 Ma 2σ) record the isotopic resetting by later hydrothermal overprints and cooling /exhumation history after E2 Gerês biotitic granite emplacement. The Wore deposition did occurred during the final E1 extensional tectonic stage (315 Ma) and E2 extensional tectonic stage for Mo-ore deposition, where a temporal offset was needed for the adjustment of tectonic conditions after the C3 compressional and E2 extensional stage started.
Sorbents Materials for Controlling Environmental Pollution. , 2021
Currently, approximately 80% of the world’s energy consumption is still supplied by fossil fuels,... more Currently, approximately 80% of the world’s energy consumption is still supplied by fossil fuels, and it was predicted that the energy consumption will increase by 35% until 2035 (BP, 2016). Recently, new data have revealed a more harmful scenario, as global primary energy grew by 2.9% in 2018, the fastest growth observed since 2010. This implied a growth of carbon emissions by 2.0%, the fastest expansion for many years, with emissions increasing by approximately 0.6Gt (BP, 2019). At current rates, it is expected that the demand for nonrenewable sources will exceed its natural production in 60 years (BP, 2019). Nevertheless, before fossil fuels become too costly or problematic to access, the world will face an unsustainable situation due to the high carbon levels in the atmosphere: “the longer carbon emissions continue to rise, the harder and more costly will be the eventual adjustment to net-zero carbon emissions” (BP, 2019). The carbon dioxide, resulted essentially from the burning of fossil fuels, absorbs solar energy and keep heat trapped on Earth’s surface (greenhouse effect), thus contributing to significant climate changes (Casper, 2010; Muthu, 2019). Therefore there is a clear need for a new generating capacity around the world to replace old fossil fuel units and to meet the increased demand for electricity in many countries. Despite the continuing rapid growth in renewable energy in recent years, it only provides a one-third of the required increase in power generation and will take a substantial period of time to become established (Kantenbacher and Shirley, 2018). Therefore nuclear energy is the only energy source that may suppress,at the same time, the world’s growing energy needs and the carbon emissions (Joyce, 2018a; Valayer et al., 2019).
Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identif... more Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO2, where the homogenization temperature (Th) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH4 (Stage II; (average Th = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average Th = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ 18 OFluid values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆quartz-scheelite fractionation occurred at about 350-400 °C. The ∆chlorite-water fractionation factor calculated is about +0.05‰ for 330 °C, dropping to −0.68‰ and −1.26‰ at 380 °C and 450 °C, respectively. Estimated crystallizing temperatures based on semiempirical chlorite geothermometers range from 373 °C to 458 °C and 435 °C to 519 °C. A narrower temperature range of 375 °C to 410 °C was estimated for Fe,Mn-chlorite crystallization.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The activity concentrations of natural (228 Ra, 226 Ra, 210 Pb, 40 K) and anthropogenic (137 Cs) ... more The activity concentrations of natural (228 Ra, 226 Ra, 210 Pb, 40 K) and anthropogenic (137 Cs) radionuclides were measured by gamma spectrometry on sediments collected from aquatic systems. The mineralogy of clay fractions identified by X-ray diffraction (XRD) is composed by an illitic material (detrital mica, illite/smectite, and illite/ smectite/vermiculite mixed-layers) ± kaolinite and illite. The Mg 2+-saturated clay fractions show three distinct illitic populations within the illitic material: detrital mica, illite/vermiculite mixed-layers, and illite/smectite. Transmission electron microscopy (TEM) images show illitic material aggregates with a flaky-and lath-shapes, pseudohexagonal platy kaolinite and lath-shape illite. The 228 Ra activity concentration values range from 30.1 to 403 Bq Kg − 1 , the 226 Ra from 24.6 to 290 Bq Kg − 1 and from 44 to 368 Bq Kg − 1 for 210 Pb. The Ra fluxes suggest a unique source where the mixing process and radioactive decay equilibrated the losses of short-(228 Ra) and long-lived (226 Ra) isotopes. The 210 Pb/ 226 Ra ratio shows an average value of 2.165, indicating that the radioactive secular equilibrium (~1) was reached. A decrease of the natural radionuclide (228 Ra, 226 Ra, 210 Pb) activity concentrations was observed in estuaries and near shore coastal sediments from north to south of Atlantic Portuguese coast. Higher 210 Pb and 226 Ra activity concentrations were obtained in samples composed by illitic material + kaolinite and organic matter. The illite/ smectite mixed-layers and kaolinite are suitable sorbents for Ra and 210 Pb isotopes. Higher 40 K values (473-1001 Bq Kg − 1) were measured on feldspar, mica and clay sediments provided from granite weathering (north region). The 137 Cs activity values range from 1.25 to 10.1 ± 1.9 Bq Kg − 1 for samples collected from the northern and central part of estuarine areas. A higher 137 Cs activity (31.2 ± 3.5 Bq Kg − 1) was measured in the southern part of the Atlantic coast, corresponding to a sediment with a higher amount of illite.
The alteration of spodumene to cookeite has been identified in a Li-bearing aplite-pegmatite from... more The alteration of spodumene to cookeite has been identified in a Li-bearing aplite-pegmatite from northern Portugal. Optical microscopy and scanning and transmission electron microscopy (SEM/ TEM) were used to characterize the alteration products in both cookeite + quartz and cookeite + kaolinite Ô mica assemblages. Mutual relationships between the minerals were assessed using back-scattered electron imaging. The first assemblage occurs along the cleavage planes of spodumene, whereas the second forms as the result of spodumene breakdown. Fine mica grains surrounded the cookeite aggregates in the second assemblage only. Precipitations of cookeite and quartz in open pore spaces and parallel packets of cookeite and kaolinite were identified by TEM. Selected area electron diffraction carried out on cookeite identified a layer-stacking sequence from highly disordered to one-layer order-disorder with a lesser participation of two-layer polytypes. The thickness of one-layer cookeite packets averaged~85À100 nm. Disordered cookeite has a mean thickness of 450 nm. The chemistry of cookeite was analyzed by both electron and ion-microprobe techniques. The structural formula of cookeite from the first assemblage corresponds to: Al 2.0 (Si 3.23 Al 0.766)O 10 (OH) 2 (Al 1.80 Li 1.166 Mg 0.004 Fe 0.09)(OH) 6. Two distinct compositional varieties were found: one corresponding to ideal cookeite, whereas the second belongs to the cookeite-donbassite join. The thermodynamic stability field for the observed minerals was calculated using the SUPCRT 1 programme. Two distinct stages of cookeite crystallization are discussed. The lower pressure and temperature stability of the reaction of spodumene to cookeite + quartz were estimated at~2.4 kbar and 240ºC. The cookeite + kaolinite Ô mica assemblage is still in equilibrium with quartz at~2.2 kbar and 220ºC. The lower limit for the stability of cookeite was found at 205ºC and 2 kbar.
The freshwater mussel Anodonta cygnea is commonly used as a model organism for biomineralization ... more The freshwater mussel Anodonta cygnea is commonly used as a model organism for biomineralization studies, its peculiar morphofunctional properties also make it an excellent environmental biomonitor. The first detailed on the calcareous concretions from gill and mantle tissue, as well as fluids of the freshwater bivalve A. cygnea, supported by histological, scanning, spectrometry, and spectroscopy analyses. Through these analyses, the morphology, structure , and chemical characterization of these biomineral con-cretions were accomplished. The concretions represent a high percentage of the dry weight of these organisms. In gill tissue, it can reach up to 50% of dry weight prior to reproductive maturity. Analysis of elemental composition of the tissue concretions showed the presence of calcium and phosphate , as main components, associated with other residual elements like iron, manganese, magnesium, and zinc. Con-cretions are arranged in concentric alternated layers of organic and inorganic matrix. The shape and size of the con-cretions vary substantially, from very small, less than 1 lm diameter with very regular round structure, found mainly in the mantle tissue, to more than 50 lm length with irregular globular clusters, found predominantly in the gills. The microstructural organization is of a hydroxyapatite poly-morphism in the mantle, in contrast to the gills, which exhibit irregular structure and carbonated hydroxyapatite polymorphism. These differences are supported by higher contents of dinitrogen pentoxide, magnesium, and iron in the mantle concretions, but higher contents of manganese and zinc in the gills. Furthermore, the results indicate that the mineral concretion formation in A. cygnea is a hemo-cytes reaction to particle or toxic invasions. A second relevant role, concerns the close involvement of these microspherules on the adult and larval shell calcification. J. Morphol. 000:000-000,
Environmental Science and Pollution research, 2016
The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncu... more The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncus sp.) and land (Cistus ladanifer L., Erica andevalensis C.-R., Nerium oleander L., Isatis tinctoria L., Rosmarinus officinalis L., Cynodon dactylon L. and Hordeum murinum L.) plants from Portugal (Aljustrel, Lousal and São Domingos) and Morocco (Tighza and Zeida) mining areas to uptake, translocate and tolerate heavy metals (Cu, Zn and Pb) was evaluated. The soils (rhizosphere) of the first mining area are characterized by high acidity conditions (pH 2-5), whereas from the second area, by alkaline conditions (pH 7.0-8.5). Physicochemical parameters and mineralogy of the rhizosphere were determined from both areas. Chemical analysis of plants and the rhizosphere was carried out by inductively coupled plasma emission spectrometry. The sequential chemical extraction procedure was applied for rhizosphere samples collected from both mining areas. In the acid conditions, the aquatic plants show a high capacity for Zn bioaccumulation and translocation and less for Pb, reflecting the following metal mobility sequence: Zn>Cu>Pb. Kaolinite detected in the roots by infrared spectroscopy (IR) contributed to metal fixation (i.e. Cu), reducing its translocation to the aerial parts. Lead identified in the roots of land plants (e.g. E. andevalensis) was probably adsorbed by C-H functional groups identified by IR, being easily translocated to the aerial parts. It was found that aquatic plants are more efficient for phytostabilization than bioaccumulation. Lead is more bioavailable in the rhizosphere from Morocco mining areas due to scarcity of minerals with high adsorption ability, being absorbed and translocated by both aquatic and land plants.
The 56o Vicente de Pereira kaolinite deposit, located at the northwestem border of the Ossa Moren... more The 56o Vicente de Pereira kaolinite deposit, located at the northwestem border of the Ossa Morena zone, in Portugal, is the site of important hydrothermal alteration, developed at the expense of migmatitic rocks and related to a system of Hercynian polyphase deformation and shear zones. Two stages of hydrothermal alteration are evident: 1) greisen-type alteration is represented [y qu:artz+ muscovite containing F and Cl, and by quartz + l6umalins; 2) post-greisen aheration and advanced argillic alteration led to the fonnation of well-ordered or poorly ordered kaolinite. The quarfz + muscovite assemblage was investigated by XRD and electron-microprobe analyses. The mica shows intermediate characteristics between muscovite and lepidolite. It has a relatively low content of Si (3.10-3.20 apfu), a high proportion of uAl, a very low Fe content, and an absence of Mg. Quartztourmaline-rich greisen occurs in veinlets that cross-cut nigmatites showing advanced argillic alteration. Two generations of lourmaline having different morphologies and different Fe conEnts can be identified. Well-ordered kaolinite formed at the expense ofmuscovite exhibits a'"booklet" morphology, as revealed by SEM and TEM observations. The hydration ofwell-ordered kaolinite led to halloysite-7A. Results of O and H isotopic analyses attest to the formation of kaolinils ft'66 metemorphic porefluid.
The b 2 μm clay fractions of three smectite samples (BA1, PS2 and PS3) were submitted to UO 2 2+ ... more The b 2 μm clay fractions of three smectite samples (BA1, PS2 and PS3) were submitted to UO 2 2+ sorption experiments at pH 4 (1 × 10 −4 ) and pH 6 (2.0 × 10 −1 ) in a continuous stirred flow-through reactor. The aim was to evaluate the influence of heterogeneous structure of smectite during the adsorption and desorption processes, where the breakthrough curves (BTCs) were used to model the mass balance. Kinetic models were applied to describe the adsorptiondesorption kinetics for a liquid-solid system. Sample PS2 (K-Illite/beidellite/Na,Ca-montmorillonite) adsorbed at pH 4 more 34% and 138% of UO 2 2+ than samples BA1 (beidellite/Ca,Na-montmorillonite) and PS3 (K-illite/Na,Ca-montmorillonite) where the dominant mechanism was the ion-exchange (outer-sphere complexation). The UO 2 2+ amount adsorbed at pH 6 decreased significantly, indicating changes in the sorption mechanism. The desorption experiments at pH 4 suggested a complete reversibility of the UO 2 2+ previously adsorbed, whereas lower reversibility of the UO 2 2+ previously adsorbed and a stronger complexation occurred at pH 6. The kinetics was highly influenced by the structural properties of heterogeneous smectite and the surface complexation mechanism involved. Samples submitted to sorption experiments at pH 4 and 6 were analysed by X-ray photoelectron spectrometry (XPS). Two binding energies were identified at 380.8 ± 0.3 eV and 382.4 ± 0.3 eV, before and after desorption processes at pH 4. The proportion of the higher binding energy component decreased after desorption process, suggesting that the UO 2 2+ weakly adsorbed was previously desorbed. The results obtained at pH 6 show two different binding energies at 380.3 ± 0.3 eV and 381.8 ± 0.3 eV, whose proportions remained unchanged before and after desorption process, indicating the higher retention of UO 2 2+ on smectite.
Ammonium-illite (NH 4 -I) is one of the alteration products present in a breccia structure in the... more Ammonium-illite (NH 4 -I) is one of the alteration products present in a breccia structure in the fossil hydrothermal system from Harghita Bãi (East Carpathians), Romania. A series from smectite (S) via ordered interstratified structures to NH 4 -I (40 to 5%S) was characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), and chemical analyses. Calculation of one-dimensional X-ray patterns was simulated with the NEWMOD code. Transition from two-to one-water smectite interlayer was identified by XRD. Selected samples were saturated with K + -, Mg 2+ -, and Li + -cations to differentiate low-to high-charge smectite or beidelite layers. X-ray patterns of random powders of K + -saturated samples, heated at 300 °C show a transition from 1Md to cisand trans-vacant 1M polytype. The cell parameters of the cis-vacant and trans-vacant 1M polytype were calculated by oblique texture electron diffraction. The vibration frequencies at 1430 cm -1 of the N-H bond were identified in the samples analyzed. Scanning and transmission electron microscopy images show morphological changes from flaky to lath-like shapes. The mean shape ratio of lath crystals ranges from 6 to 5.42 nm and the mean area from 7.8 to 24 × 10 4 nm 2 . The mean thickness of the NH 4 -I layers ranges from 4.62 to 7.89 nm. The calculated structural formula of end-member NH 4 -I (5%S) is: [(NH 4 + ) 0.66 K + 0.10 Na + 0.01 Sr 2+ 0.02 ] 0.81 (Al 3+ 1.85 Fe 3+ 0.01 Mg 2+ 0.15 ) 2.01 (Si 4+ 3.30 Al 3+ 0.70 ) 4.00 O 10 (OH) 2 . The fixed NH 4 + content quantified ranges from 0.39 to 0.66 atoms per half unit cell [O 10 (OH) 2 ]. Tetrahedral and octahedral substitutions took place as the %S decreases. The NH 4 -I-S series formed via direct precipitation from solution at different temperatures.
AB ST R ACT : Ammonium illite and ammonium illite-smectite mixed layers, together with potassium ... more AB ST R ACT : Ammonium illite and ammonium illite-smectite mixed layers, together with potassium illite, smectite and minute amounts of kaolinite were identified in hydrothermally altered andesite rocks from the Harghita Bãi area of the Eastern Carpathians, Romania. K-Ar dating and oxygen isotope tracing, as well as rare-earth elemental analyses were made to provide new information on the timing and crystal-chemical processes characterizing the crystallization and further evolution of these illite-type mineral phases. The combined results suggest the occurrence of hydrothermal activity in two distinct episodes with nucleation of two generations of illite-type particles of different chemistry and morphology. About 9.5 Ma ago, potassium illite crystallized in alteration halos of the porphyry Cu system, probably at a temperature of~270ºC from fluids having a d 18 O of~2.9% (V-SMOW). Associated smectite seems to have precipitated slightly later in external alteration halos at a similar temperature, but from fluids depleted in alkalis and with a different d 18 O. Alternately, ammonium-rich illite-smectite mixed layers formed very recently, less than~1 million years ago at a temperature of~90ºC from fluids of probable meteoric origin that altered the previously crystallized potassium illite, resulting in the crystallization of a new generation of ammonium illite-smectite mixed layers. Evidence of this dissolution-precipitation process is provided by a significant increase in the d 18 O of the mixed-layer structures and by a significant change in their REE contents and distribution patterns. Occurrence of potassium in the ammonium-rich mixed layers probably relates to the progressive alteration of the first-generation potassium illite and a discrete concomitant take up of released K by the new NH 4-rich interlayers of the ammonium mixed layered sequence.
The Pb-Zn-(Cu-Ag) hydrothermal veins from Central and Northern Portugal occur in two distinct dis... more The Pb-Zn-(Cu-Ag) hydrothermal veins from Central and Northern Portugal occur in two distinct districts: Aveiro (Moinho da Pena, Carvalhal, Palhal and Telhadela) and Bragança (Ferronho, Vale da Madre, Estevais and Olgas). The ore veins are composed by sulfides (galena, sphalerite, chalcopyrite, pyrite), several quartz generations in both districts and dolomite as a gangue mineral in the Aveiro district (Palhal and Telhadela). A mineralogical, fluid inclusion and (S, C, O, Pb) isotopic study was carried out on ore mineralization with the aim to explain its genesis and metallogenic evolution. Aqueous fluids of H 2 O-CaCl 2 or H 2 O-NaCl-CaCl 2 in composition were identified in both districts. The T h /T mi evolution starts with fluids of medium temperature (> 250°C) and low to moderate salinity (1 eq. wt% NaCl in the Aveiro district and 0.5 eq. wt% in the Bragança district), evolving to lower temperatures (250-100°C) and higher salinity for the Aveiro district (20 eq. wt% NaCl) and lower salinity (~4 eq. wt% NaCl) for the Bragança district. Fluids of high salinity (~20 eq. wt% NaCl) were trapped during the final stage at temperatures below to 100°C. A mixing magmatic and meteoric fluid explained the wide negative values range of δ 34 S measured for the samples from the Aveiro district. High positive δ 34 S values measured on samples collected from the Bragança district confirm a seawater source. The C and O stable isotope measured on dolomite and calcite show a 13 C-depleted source for both carbonates, pointing to a carbon sources related to the organic matter oxidation. The Pb isotope data confirm an uranogenic and a thoriogenic source. The Pb-Zn ore deposits from the Aveiro and Bragança districts are related to episodes of fluid circulation in the upper crust during late to post-Variscan period. The lack of spatial and temporal relationship with magmatic episodes and the presence of basinal and superficial origin fluids support this idea.
Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4
+-fixation in... more Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4 +-fixation in illitic clays is relevant for the N-input budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic- altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12% smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.
A genetic linkage between W, (Cu, Mo)-mineralization and chlorite minerals, and the discriminatio... more A genetic linkage between W, (Cu, Mo)-mineralization and chlorite minerals, and the discrimination of different mineralization events in the magmatic-hydrothermal system of Borralha, northern Portugal, is discussed on the basis of textural relationships, crystal chemistry and stable isotopic data obtained from chlorite. Chlorite minerals were identified in assemblages with quartz, feldspars, tungstates and sulfides. X-ray diffraction studies of selected chlorite minerals shows a trioctahedral structural type. Electron probe micro-analyses identified four different compositions and associations: (1) Fe,Mn-chlorite with scheelite I; (2) Fe-chlorite with wolframite + scheelite II ± sulfide; (3) Fe,Mg-chlorite with molybdenite + bismuthinite; and (4) Mg,Fe-chlorite with chalcopyrite. The composition of Fe-chlorite (Al 3.01 Fe 3+ 0.25 Fe 2+ 7.95 Mn 0.26 Mg 0.19) 11.66 (Si 5.44 Al 2.56) 8 O 20 (OH) 8 corresponds to daphnite and Fe,Mn-chlorite (Al 2.69 Fe 3+ 0.02 Fe 2+ 7.54 Mn 1.08 Mg 0.62) 11.89 (Si 5.31 Al 2.68) 4 O 20 (OH) 8 to a mixed composition between daphnite and amesite. The Fe,Mg-chlorite (Al 2.89 Fe 3+ 0.24 Fe 2+ 6.42 Mn 0.21 Mg 2.08) 11.84 (Si 5.31 Al 2.79) 8 F 0.31 O 20 (OH) 8 corresponds to ripidolite and Mg,Fe-chlorite (Al 2.63 Fe 3+ 0.37 Fe 2+ 1.72 Mn 0.01 Mg 6.40 Ca 0.26) 11.39 (Si 6.02 Al 1.98) 8 O 20 (OH) 8 to pych-nochlorite. Chlorite geothermometry estimates a temperature for Fe,Mn-chlorite (scheelite I) from 400°C to 500°C, for Fe-chlorite (Mn-rich wolframite + scheelite II ± sulfide) from 250 to 350°C, for Fe,Mg-chlorite (Mo-mineralization) from 200°C to 250°C and for Mg,Fe-chlorite at ∼150°C. Oxygen isotopes (V-SMOW) yielded values of +3.8 (1σ) (Fe-chlorite), +6.91 (1σ) (Fe,Mn-chlorite) and +1.5 (1σ) (Fe,Mg-chlorite). The calculated δ 18 O F of Fe-and Fe,Mg-chlorite is ∼+3.75 (1σ) and +1.45 (1σ) for the mineralizing fluid, whereas for Fe,Mn-chlorite it is +8.17 (1σ). The δ 18 O data obtained from quartz in Wand Mo-mineralization yielded values of +12.6 and +11.4 (1σ), whereas for adularia δ 18 O is about +10 (1σ). These estimates allow us to conclude that the Fe,Mn-chlorite crystallized from a magmatic-hydrothermal fluid, whereas the Fe-and Fe,Mg-chlorite quartz and adularia resulted from a mixed contribution between meteoric and magmatic-hydrothermal fluid.
A B S T R A C T Coarse (2.0–0.2 μm) and fine (< 0.2 μm) clay fractions of NH 4-illite-smectite (I... more A B S T R A C T Coarse (2.0–0.2 μm) and fine (< 0.2 μm) clay fractions of NH 4-illite-smectite (IS) mixed-layered and K-illite/ (NH 4 , K)-illite (I) mixed phases that vary in age and trace element composition were collected from the fossil hydrothermal system of Harghita Bãi, East Carpathians. Boron and Li isotope ratios were measured by secondary ion mass spectrometry (SIMS), and N by isotope ratio mass spectrometry (IRMS) with the aim to characterize the isotope geochemistry and source of light elements fixed in authigenic NH 4-illitic clays. Boron in NH 4-IS clays ranges from 513 to 1457 ppm and reached ~1000 ppm in the K-I/(NH 4 , K)-I. The δ 11 B (‰) measured in NH 4-IS ranges from −12.6 to − 22.4 (± 0.3‰) and in K-I/(NH 4 , K)-I is consistently −5.5 to − 5.1 (± 0.3‰). Boron isotopes systematically become lighter in the NH 4-IS series as temperature increased from 90 to 270 °C. Low Li content (1 to 8 ppm) was found in illitic clay fractions. The δ 7 Li (‰) shows negative values ranging from − 8.6 to −12.3 (± 0.8‰) for the coarser (2.0–0.2 μm) NH 4-IS clays and from +4.3 to + 14.1 (± 1‰) for the finer (< 0.2 μm) fraction of NH 4-IS and K-I/(NH 4 , K)-I clays. The N (%) measured in the NH 4-IS clays ranges from 0.70 to 1.50 (± 0.2%), whereas in the K-I/(NH 4 , K)-I is about 0.70 (± 0.2%). The δ 15 N (‰) ranges from +4.8 to +7.4 (± 0.6) for most NH 4-IS and NH 4 , K-I clays, with one outlier for NH 4-IS of +14.6 (± 0.6). The δ 11 B of K-I/(NH 4 , K)-I clays reflect a magmatic source, whereas the NH 4-IS series is consistent with the influx of isotopically light-B waters derived from hydrothermal leaching of continental evaporites and/or organic rich sediments. The δ 7 Li signature measured on K-I/(NH 4 , K)-I clays also support a magmatic fluid, enriched in heavy Li, followed by precipitation of coarser NH 4-IS from more recent sedimentary contributions of isotopically light Li. This interpretation is also supported by the δ 15 N, which reflect an influx of waters from an organic sediment origin. The δ 15 N of + 14.6‰ (± 0.6) measured on NH 4-IS could be attributed to the presence of meteoric waters mixed with hydrothermal fluids. The isotopic data obtained trace the mobility of magmatic and organic – sedimentary components in the upper continental crust.
he Hercynian late-orogenic granites from the Gerês massif, northern Portugal, underwent intense h... more he Hercynian late-orogenic granites from the Gerês massif, northern Portugal, underwent intense hydrothermal activity along tectonic structures striking N-S and NE-SW. The first hydrothermal stage is characterized by the albitization of feldspars (primary K-feldspar and plagioclase) followed by the dis- solution of magmatic quartz, the chloritization of biotite, and the muscovitization of magmatic biotite and feldspars and occasionally of authigenic albite. Whole-rock geochemistry shows a decrease of SiO2, K2O and Rb and an increase of Na2 O, Al2 O3 and Sr amounts during the albitization. The second hydrothermal stage is characterized by a mineral assemblage consisting of secondary quartz, albite, chlorite, hematite, apatite, muscovite, epidote, sphene and carbonates, which infilled the cavities produced by the early quartz leaching. Mass balance calculations demonstrate a noticeable element mobilization during the granite alteration.
Environmental Science and Pollution Research, 2017
Acid mine waters (AMW) collected during high-and low-flow water conditions from the Lousal, Aljus... more Acid mine waters (AMW) collected during high-and low-flow water conditions from the Lousal, Aljustrel, and São Domingos mining areas (Iberian Pyrite Belt) were physicochemically analyzed. Speciation calculation using PHREEQC code confirms the predominance of Me n+ and Me–SO 4 species in AMW samples. Higher concentration of sulfate species (Me–SO 4) than free ion species (Me n+ , i.e., Al, Fe, and Pb) were found, whereas opposite behavior is verified for Mg, Cu, and Zn. A high mobility of Zn than Cu and Pb was identified. The sulfate species distribution shows that Fe 3+ –SO 4 2− , SO 4 2− , HSO 4 − , Al–SO 4 , MgSO 4 0 , and CaSO 4 0 are the dominant species, in agreement with the simple and mixed metal sulfates and oxy-hydroxysulphates precipitated from AMW. The saturation indices (SI) of melanterite and epsomite show a positive correlation with Cu and Zn concentrations in AMW, which are frequently retained in simple metal sulfates. Lead is well correlated with jarosite and alunite (at least in very acid conditions) than with simple metal sulfates. The Pb for K substitution in jarosite occurs as increasing Pb concentration in solution. Lead mobility is also controlled by anglesite precipitation (a fairly insoluble sulfate), where a positive correlation was ascertained when the SI approaches equilibrium. The zeta potential of AMW decreased as pH increased due to colloidal particles aggregation, where water species change from SO 4 2− to OH − species during acid to alkaline conditions, respectively. The AMW samples were supersaturated in schwertmannite and goethite, confirmed by the Me n+ –SO 4 , Me n+ –Fe–O–OH, or Me n+ –S–O–Fe–O complexes identified by attenuated total reflectance infrared spec-troscopy (ATR-IR). The ATR-IR spectrum of an AMW sample with pH 3.5 (sample L1) shows well-defined vibration plans attributed to SO 4 tetrahedron bonded with Fe-(oxy)hydroxides and the Me n+ sorbed by either SO 4 or Fe-(oxy)hydroxides. For samples with lower pH values (pH ~ 2.5—samples SD1 and SD4), the vibration plans attributed to Me n+ sorption are not evidenced, indicating its release in solution. The sorption of heavy metals on the first precipitated simple metal sulfates was ascertained by scanning electron microscopy coupled with X-ray spectrometry (SEM-EDX), where X-ray maps of Cu and Zn confirm a distribution of both metals in the melanterite structure.
Random and ordered mixed-layer smectite-ammonium illite (NH 4 -I/S) were identified by XRD analys... more Random and ordered mixed-layer smectite-ammonium illite (NH 4 -I/S) were identified by XRD analysis in the fossil hydrothermal system of Harghita Bãi (Eastern Carpathians, Romania). Morphologies of NH 4 -I/S were studied by SEM and TEM. SEM image of random NH 4 -I/S displays a cellular or cornflake texture. Ordered NH 4 -I/S (R=1) exhibits a scalloped morphology with curled edges. Ribbon crystals of illite rise from the surfaces of plate aggregates. Two generations of NH 4 -I are distinguished: one developed from a smectite precursor and another from a kaolinite precursor. Hairy illite and illite pseudomorphs after book-like aggregates of kaolinite are present. TEM images show the evolution of morphology from flake to lath habit during the smectite to illite conversion. Particles with veil characteristics and flake particles are observed in random mixed-layered NH 4 -I/S. Diffuse lath shaped illite developed on the previous morphology in the expandability range 7020 %S is observed. Euhedral lath shaped illite is present in NH 4 -I/S, below 10 %S. The reaction of smectite-to-illite is continuous, leading to lath shaped illite.
Journal of Radioanalytical and Nuclear Chemistry, 2015
Your article is protected by copyright and all rights are held exclusively by Akadémiai Kiadó, Bu... more Your article is protected by copyright and all rights are held exclusively by Akadémiai Kiadó, Budapest, Hungary. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
The Borralha area (Iberian Massif, Portugal) reflects a long-lived and multiphase magmatism (ca. ... more The Borralha area (Iberian Massif, Portugal) reflects a long-lived and multiphase magmatism (ca. 316 to 300 Ma), characterized by three types of granite emplacement during two different extensional events (E1 and E2) and one compressional event (C3) within the Variscan orogeny. The W (Cu) mineralization styles correspond to veinlets and quartz veins (i.e., São António and Santa Helena), and disseminations in the Santa Helena breccia pipe. Molybdenite coexists with an Fe-bearing wolframite-quartz assemblage in the Venise breccia pipe and quartz veins (i.e., São José and São Paulo). The geochemistry and geochronology of wolframite and molybdenite samples were studied by electron probe microanalysis (EPMA), in-situ U-Pb laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and Re-Os thermal ionization mass spectrometry (TIMS). The wolframite yields a U-Pb age (sample WBV1) of 315.2 ± 4.7 Ma (2σ), representing the first recognized episode of W deposition in the Iberian Massif. Wolframite samples (WBV1, WB1, and WB4) have a ferberite composition with a hübnerite/ferberite ratio of < 29. High amounts of Nb (up to 3703 ppm) with low Ta (up to 123 ppm) and REEs (up to 11.4 ppm) and conversely, low amounts of Nb (up to 471 ppm) with high Ta (up to 190 ppm) and REEs (up to 53.7 ppm) were measured in wolframite samples. The REEs normalized patterns of the wolframite samples record a mixed signature. Large and positive Eu/Eu* and Er/Er* anomalies were identified (sample WBV1), whereas negative Ce/Ce* and Nd/ Nd* anomalies were observed in samples WB1 and WB4. Molybdenite Re-Os dating yields absolute ages ranging from 305.1 to 303.8 ± 2.2 Ma (2σ), which are coeval with the emplacement of E2 biotite granite (Penedos; I-type; <305 Ma). Low amounts of Re (<1 ppm), W, Co, Ni, As, Cu, Bi, Fe, Mn V and Se (<0.005 wt%) were detected in the molybdenite structure. Constraints between the timing of Wand Mo-deposition and a protracted cooling history of the host rocks are confirmed by 40 Ar/ 39 Ar white mica dating. The 40 Ar/ 39 Ar ages obtained for secondary white micas collected from Mo veins (Venise breccia pipe; 277 ± 3 and 287 ± 4 Ma 2σ) and W (Cu) dissemination (Santa Helena breccia pipe; 287 ± 2 and 279.0 ± 6 Ma 2σ) record the isotopic resetting by later hydrothermal overprints and cooling /exhumation history after E2 Gerês biotitic granite emplacement. The Wore deposition did occurred during the final E1 extensional tectonic stage (315 Ma) and E2 extensional tectonic stage for Mo-ore deposition, where a temporal offset was needed for the adjustment of tectonic conditions after the C3 compressional and E2 extensional stage started.
Sorbents Materials for Controlling Environmental Pollution. , 2021
Currently, approximately 80% of the world’s energy consumption is still supplied by fossil fuels,... more Currently, approximately 80% of the world’s energy consumption is still supplied by fossil fuels, and it was predicted that the energy consumption will increase by 35% until 2035 (BP, 2016). Recently, new data have revealed a more harmful scenario, as global primary energy grew by 2.9% in 2018, the fastest growth observed since 2010. This implied a growth of carbon emissions by 2.0%, the fastest expansion for many years, with emissions increasing by approximately 0.6Gt (BP, 2019). At current rates, it is expected that the demand for nonrenewable sources will exceed its natural production in 60 years (BP, 2019). Nevertheless, before fossil fuels become too costly or problematic to access, the world will face an unsustainable situation due to the high carbon levels in the atmosphere: “the longer carbon emissions continue to rise, the harder and more costly will be the eventual adjustment to net-zero carbon emissions” (BP, 2019). The carbon dioxide, resulted essentially from the burning of fossil fuels, absorbs solar energy and keep heat trapped on Earth’s surface (greenhouse effect), thus contributing to significant climate changes (Casper, 2010; Muthu, 2019). Therefore there is a clear need for a new generating capacity around the world to replace old fossil fuel units and to meet the increased demand for electricity in many countries. Despite the continuing rapid growth in renewable energy in recent years, it only provides a one-third of the required increase in power generation and will take a substantial period of time to become established (Kantenbacher and Shirley, 2018). Therefore nuclear energy is the only energy source that may suppress,at the same time, the world’s growing energy needs and the carbon emissions (Joyce, 2018a; Valayer et al., 2019).
Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identif... more Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO2, where the homogenization temperature (Th) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH4 (Stage II; (average Th = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average Th = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ 18 OFluid values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆quartz-scheelite fractionation occurred at about 350-400 °C. The ∆chlorite-water fractionation factor calculated is about +0.05‰ for 330 °C, dropping to −0.68‰ and −1.26‰ at 380 °C and 450 °C, respectively. Estimated crystallizing temperatures based on semiempirical chlorite geothermometers range from 373 °C to 458 °C and 435 °C to 519 °C. A narrower temperature range of 375 °C to 410 °C was estimated for Fe,Mn-chlorite crystallization.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The activity concentrations of natural (228 Ra, 226 Ra, 210 Pb, 40 K) and anthropogenic (137 Cs) ... more The activity concentrations of natural (228 Ra, 226 Ra, 210 Pb, 40 K) and anthropogenic (137 Cs) radionuclides were measured by gamma spectrometry on sediments collected from aquatic systems. The mineralogy of clay fractions identified by X-ray diffraction (XRD) is composed by an illitic material (detrital mica, illite/smectite, and illite/ smectite/vermiculite mixed-layers) ± kaolinite and illite. The Mg 2+-saturated clay fractions show three distinct illitic populations within the illitic material: detrital mica, illite/vermiculite mixed-layers, and illite/smectite. Transmission electron microscopy (TEM) images show illitic material aggregates with a flaky-and lath-shapes, pseudohexagonal platy kaolinite and lath-shape illite. The 228 Ra activity concentration values range from 30.1 to 403 Bq Kg − 1 , the 226 Ra from 24.6 to 290 Bq Kg − 1 and from 44 to 368 Bq Kg − 1 for 210 Pb. The Ra fluxes suggest a unique source where the mixing process and radioactive decay equilibrated the losses of short-(228 Ra) and long-lived (226 Ra) isotopes. The 210 Pb/ 226 Ra ratio shows an average value of 2.165, indicating that the radioactive secular equilibrium (~1) was reached. A decrease of the natural radionuclide (228 Ra, 226 Ra, 210 Pb) activity concentrations was observed in estuaries and near shore coastal sediments from north to south of Atlantic Portuguese coast. Higher 210 Pb and 226 Ra activity concentrations were obtained in samples composed by illitic material + kaolinite and organic matter. The illite/ smectite mixed-layers and kaolinite are suitable sorbents for Ra and 210 Pb isotopes. Higher 40 K values (473-1001 Bq Kg − 1) were measured on feldspar, mica and clay sediments provided from granite weathering (north region). The 137 Cs activity values range from 1.25 to 10.1 ± 1.9 Bq Kg − 1 for samples collected from the northern and central part of estuarine areas. A higher 137 Cs activity (31.2 ± 3.5 Bq Kg − 1) was measured in the southern part of the Atlantic coast, corresponding to a sediment with a higher amount of illite.
The alteration of spodumene to cookeite has been identified in a Li-bearing aplite-pegmatite from... more The alteration of spodumene to cookeite has been identified in a Li-bearing aplite-pegmatite from northern Portugal. Optical microscopy and scanning and transmission electron microscopy (SEM/ TEM) were used to characterize the alteration products in both cookeite + quartz and cookeite + kaolinite Ô mica assemblages. Mutual relationships between the minerals were assessed using back-scattered electron imaging. The first assemblage occurs along the cleavage planes of spodumene, whereas the second forms as the result of spodumene breakdown. Fine mica grains surrounded the cookeite aggregates in the second assemblage only. Precipitations of cookeite and quartz in open pore spaces and parallel packets of cookeite and kaolinite were identified by TEM. Selected area electron diffraction carried out on cookeite identified a layer-stacking sequence from highly disordered to one-layer order-disorder with a lesser participation of two-layer polytypes. The thickness of one-layer cookeite packets averaged~85À100 nm. Disordered cookeite has a mean thickness of 450 nm. The chemistry of cookeite was analyzed by both electron and ion-microprobe techniques. The structural formula of cookeite from the first assemblage corresponds to: Al 2.0 (Si 3.23 Al 0.766)O 10 (OH) 2 (Al 1.80 Li 1.166 Mg 0.004 Fe 0.09)(OH) 6. Two distinct compositional varieties were found: one corresponding to ideal cookeite, whereas the second belongs to the cookeite-donbassite join. The thermodynamic stability field for the observed minerals was calculated using the SUPCRT 1 programme. Two distinct stages of cookeite crystallization are discussed. The lower pressure and temperature stability of the reaction of spodumene to cookeite + quartz were estimated at~2.4 kbar and 240ºC. The cookeite + kaolinite Ô mica assemblage is still in equilibrium with quartz at~2.2 kbar and 220ºC. The lower limit for the stability of cookeite was found at 205ºC and 2 kbar.
The freshwater mussel Anodonta cygnea is commonly used as a model organism for biomineralization ... more The freshwater mussel Anodonta cygnea is commonly used as a model organism for biomineralization studies, its peculiar morphofunctional properties also make it an excellent environmental biomonitor. The first detailed on the calcareous concretions from gill and mantle tissue, as well as fluids of the freshwater bivalve A. cygnea, supported by histological, scanning, spectrometry, and spectroscopy analyses. Through these analyses, the morphology, structure , and chemical characterization of these biomineral con-cretions were accomplished. The concretions represent a high percentage of the dry weight of these organisms. In gill tissue, it can reach up to 50% of dry weight prior to reproductive maturity. Analysis of elemental composition of the tissue concretions showed the presence of calcium and phosphate , as main components, associated with other residual elements like iron, manganese, magnesium, and zinc. Con-cretions are arranged in concentric alternated layers of organic and inorganic matrix. The shape and size of the con-cretions vary substantially, from very small, less than 1 lm diameter with very regular round structure, found mainly in the mantle tissue, to more than 50 lm length with irregular globular clusters, found predominantly in the gills. The microstructural organization is of a hydroxyapatite poly-morphism in the mantle, in contrast to the gills, which exhibit irregular structure and carbonated hydroxyapatite polymorphism. These differences are supported by higher contents of dinitrogen pentoxide, magnesium, and iron in the mantle concretions, but higher contents of manganese and zinc in the gills. Furthermore, the results indicate that the mineral concretion formation in A. cygnea is a hemo-cytes reaction to particle or toxic invasions. A second relevant role, concerns the close involvement of these microspherules on the adult and larval shell calcification. J. Morphol. 000:000-000,
Environmental Science and Pollution research, 2016
The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncu... more The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncus sp.) and land (Cistus ladanifer L., Erica andevalensis C.-R., Nerium oleander L., Isatis tinctoria L., Rosmarinus officinalis L., Cynodon dactylon L. and Hordeum murinum L.) plants from Portugal (Aljustrel, Lousal and São Domingos) and Morocco (Tighza and Zeida) mining areas to uptake, translocate and tolerate heavy metals (Cu, Zn and Pb) was evaluated. The soils (rhizosphere) of the first mining area are characterized by high acidity conditions (pH 2-5), whereas from the second area, by alkaline conditions (pH 7.0-8.5). Physicochemical parameters and mineralogy of the rhizosphere were determined from both areas. Chemical analysis of plants and the rhizosphere was carried out by inductively coupled plasma emission spectrometry. The sequential chemical extraction procedure was applied for rhizosphere samples collected from both mining areas. In the acid conditions, the aquatic plants show a high capacity for Zn bioaccumulation and translocation and less for Pb, reflecting the following metal mobility sequence: Zn>Cu>Pb. Kaolinite detected in the roots by infrared spectroscopy (IR) contributed to metal fixation (i.e. Cu), reducing its translocation to the aerial parts. Lead identified in the roots of land plants (e.g. E. andevalensis) was probably adsorbed by C-H functional groups identified by IR, being easily translocated to the aerial parts. It was found that aquatic plants are more efficient for phytostabilization than bioaccumulation. Lead is more bioavailable in the rhizosphere from Morocco mining areas due to scarcity of minerals with high adsorption ability, being absorbed and translocated by both aquatic and land plants.
The 56o Vicente de Pereira kaolinite deposit, located at the northwestem border of the Ossa Moren... more The 56o Vicente de Pereira kaolinite deposit, located at the northwestem border of the Ossa Morena zone, in Portugal, is the site of important hydrothermal alteration, developed at the expense of migmatitic rocks and related to a system of Hercynian polyphase deformation and shear zones. Two stages of hydrothermal alteration are evident: 1) greisen-type alteration is represented [y qu:artz+ muscovite containing F and Cl, and by quartz + l6umalins; 2) post-greisen aheration and advanced argillic alteration led to the fonnation of well-ordered or poorly ordered kaolinite. The quarfz + muscovite assemblage was investigated by XRD and electron-microprobe analyses. The mica shows intermediate characteristics between muscovite and lepidolite. It has a relatively low content of Si (3.10-3.20 apfu), a high proportion of uAl, a very low Fe content, and an absence of Mg. Quartztourmaline-rich greisen occurs in veinlets that cross-cut nigmatites showing advanced argillic alteration. Two generations of lourmaline having different morphologies and different Fe conEnts can be identified. Well-ordered kaolinite formed at the expense ofmuscovite exhibits a'"booklet" morphology, as revealed by SEM and TEM observations. The hydration ofwell-ordered kaolinite led to halloysite-7A. Results of O and H isotopic analyses attest to the formation of kaolinils ft'66 metemorphic porefluid.
The b 2 μm clay fractions of three smectite samples (BA1, PS2 and PS3) were submitted to UO 2 2+ ... more The b 2 μm clay fractions of three smectite samples (BA1, PS2 and PS3) were submitted to UO 2 2+ sorption experiments at pH 4 (1 × 10 −4 ) and pH 6 (2.0 × 10 −1 ) in a continuous stirred flow-through reactor. The aim was to evaluate the influence of heterogeneous structure of smectite during the adsorption and desorption processes, where the breakthrough curves (BTCs) were used to model the mass balance. Kinetic models were applied to describe the adsorptiondesorption kinetics for a liquid-solid system. Sample PS2 (K-Illite/beidellite/Na,Ca-montmorillonite) adsorbed at pH 4 more 34% and 138% of UO 2 2+ than samples BA1 (beidellite/Ca,Na-montmorillonite) and PS3 (K-illite/Na,Ca-montmorillonite) where the dominant mechanism was the ion-exchange (outer-sphere complexation). The UO 2 2+ amount adsorbed at pH 6 decreased significantly, indicating changes in the sorption mechanism. The desorption experiments at pH 4 suggested a complete reversibility of the UO 2 2+ previously adsorbed, whereas lower reversibility of the UO 2 2+ previously adsorbed and a stronger complexation occurred at pH 6. The kinetics was highly influenced by the structural properties of heterogeneous smectite and the surface complexation mechanism involved. Samples submitted to sorption experiments at pH 4 and 6 were analysed by X-ray photoelectron spectrometry (XPS). Two binding energies were identified at 380.8 ± 0.3 eV and 382.4 ± 0.3 eV, before and after desorption processes at pH 4. The proportion of the higher binding energy component decreased after desorption process, suggesting that the UO 2 2+ weakly adsorbed was previously desorbed. The results obtained at pH 6 show two different binding energies at 380.3 ± 0.3 eV and 381.8 ± 0.3 eV, whose proportions remained unchanged before and after desorption process, indicating the higher retention of UO 2 2+ on smectite.
Ammonium-illite (NH 4 -I) is one of the alteration products present in a breccia structure in the... more Ammonium-illite (NH 4 -I) is one of the alteration products present in a breccia structure in the fossil hydrothermal system from Harghita Bãi (East Carpathians), Romania. A series from smectite (S) via ordered interstratified structures to NH 4 -I (40 to 5%S) was characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), and chemical analyses. Calculation of one-dimensional X-ray patterns was simulated with the NEWMOD code. Transition from two-to one-water smectite interlayer was identified by XRD. Selected samples were saturated with K + -, Mg 2+ -, and Li + -cations to differentiate low-to high-charge smectite or beidelite layers. X-ray patterns of random powders of K + -saturated samples, heated at 300 °C show a transition from 1Md to cisand trans-vacant 1M polytype. The cell parameters of the cis-vacant and trans-vacant 1M polytype were calculated by oblique texture electron diffraction. The vibration frequencies at 1430 cm -1 of the N-H bond were identified in the samples analyzed. Scanning and transmission electron microscopy images show morphological changes from flaky to lath-like shapes. The mean shape ratio of lath crystals ranges from 6 to 5.42 nm and the mean area from 7.8 to 24 × 10 4 nm 2 . The mean thickness of the NH 4 -I layers ranges from 4.62 to 7.89 nm. The calculated structural formula of end-member NH 4 -I (5%S) is: [(NH 4 + ) 0.66 K + 0.10 Na + 0.01 Sr 2+ 0.02 ] 0.81 (Al 3+ 1.85 Fe 3+ 0.01 Mg 2+ 0.15 ) 2.01 (Si 4+ 3.30 Al 3+ 0.70 ) 4.00 O 10 (OH) 2 . The fixed NH 4 + content quantified ranges from 0.39 to 0.66 atoms per half unit cell [O 10 (OH) 2 ]. Tetrahedral and octahedral substitutions took place as the %S decreases. The NH 4 -I-S series formed via direct precipitation from solution at different temperatures.
AB ST R ACT : Ammonium illite and ammonium illite-smectite mixed layers, together with potassium ... more AB ST R ACT : Ammonium illite and ammonium illite-smectite mixed layers, together with potassium illite, smectite and minute amounts of kaolinite were identified in hydrothermally altered andesite rocks from the Harghita Bãi area of the Eastern Carpathians, Romania. K-Ar dating and oxygen isotope tracing, as well as rare-earth elemental analyses were made to provide new information on the timing and crystal-chemical processes characterizing the crystallization and further evolution of these illite-type mineral phases. The combined results suggest the occurrence of hydrothermal activity in two distinct episodes with nucleation of two generations of illite-type particles of different chemistry and morphology. About 9.5 Ma ago, potassium illite crystallized in alteration halos of the porphyry Cu system, probably at a temperature of~270ºC from fluids having a d 18 O of~2.9% (V-SMOW). Associated smectite seems to have precipitated slightly later in external alteration halos at a similar temperature, but from fluids depleted in alkalis and with a different d 18 O. Alternately, ammonium-rich illite-smectite mixed layers formed very recently, less than~1 million years ago at a temperature of~90ºC from fluids of probable meteoric origin that altered the previously crystallized potassium illite, resulting in the crystallization of a new generation of ammonium illite-smectite mixed layers. Evidence of this dissolution-precipitation process is provided by a significant increase in the d 18 O of the mixed-layer structures and by a significant change in their REE contents and distribution patterns. Occurrence of potassium in the ammonium-rich mixed layers probably relates to the progressive alteration of the first-generation potassium illite and a discrete concomitant take up of released K by the new NH 4-rich interlayers of the ammonium mixed layered sequence.
The Pb-Zn-(Cu-Ag) hydrothermal veins from Central and Northern Portugal occur in two distinct dis... more The Pb-Zn-(Cu-Ag) hydrothermal veins from Central and Northern Portugal occur in two distinct districts: Aveiro (Moinho da Pena, Carvalhal, Palhal and Telhadela) and Bragança (Ferronho, Vale da Madre, Estevais and Olgas). The ore veins are composed by sulfides (galena, sphalerite, chalcopyrite, pyrite), several quartz generations in both districts and dolomite as a gangue mineral in the Aveiro district (Palhal and Telhadela). A mineralogical, fluid inclusion and (S, C, O, Pb) isotopic study was carried out on ore mineralization with the aim to explain its genesis and metallogenic evolution. Aqueous fluids of H 2 O-CaCl 2 or H 2 O-NaCl-CaCl 2 in composition were identified in both districts. The T h /T mi evolution starts with fluids of medium temperature (> 250°C) and low to moderate salinity (1 eq. wt% NaCl in the Aveiro district and 0.5 eq. wt% in the Bragança district), evolving to lower temperatures (250-100°C) and higher salinity for the Aveiro district (20 eq. wt% NaCl) and lower salinity (~4 eq. wt% NaCl) for the Bragança district. Fluids of high salinity (~20 eq. wt% NaCl) were trapped during the final stage at temperatures below to 100°C. A mixing magmatic and meteoric fluid explained the wide negative values range of δ 34 S measured for the samples from the Aveiro district. High positive δ 34 S values measured on samples collected from the Bragança district confirm a seawater source. The C and O stable isotope measured on dolomite and calcite show a 13 C-depleted source for both carbonates, pointing to a carbon sources related to the organic matter oxidation. The Pb isotope data confirm an uranogenic and a thoriogenic source. The Pb-Zn ore deposits from the Aveiro and Bragança districts are related to episodes of fluid circulation in the upper crust during late to post-Variscan period. The lack of spatial and temporal relationship with magmatic episodes and the presence of basinal and superficial origin fluids support this idea.
Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4
+-fixation in... more Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4 +-fixation in illitic clays is relevant for the N-input budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic- altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12% smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.
A genetic linkage between W, (Cu, Mo)-mineralization and chlorite minerals, and the discriminatio... more A genetic linkage between W, (Cu, Mo)-mineralization and chlorite minerals, and the discrimination of different mineralization events in the magmatic-hydrothermal system of Borralha, northern Portugal, is discussed on the basis of textural relationships, crystal chemistry and stable isotopic data obtained from chlorite. Chlorite minerals were identified in assemblages with quartz, feldspars, tungstates and sulfides. X-ray diffraction studies of selected chlorite minerals shows a trioctahedral structural type. Electron probe micro-analyses identified four different compositions and associations: (1) Fe,Mn-chlorite with scheelite I; (2) Fe-chlorite with wolframite + scheelite II ± sulfide; (3) Fe,Mg-chlorite with molybdenite + bismuthinite; and (4) Mg,Fe-chlorite with chalcopyrite. The composition of Fe-chlorite (Al 3.01 Fe 3+ 0.25 Fe 2+ 7.95 Mn 0.26 Mg 0.19) 11.66 (Si 5.44 Al 2.56) 8 O 20 (OH) 8 corresponds to daphnite and Fe,Mn-chlorite (Al 2.69 Fe 3+ 0.02 Fe 2+ 7.54 Mn 1.08 Mg 0.62) 11.89 (Si 5.31 Al 2.68) 4 O 20 (OH) 8 to a mixed composition between daphnite and amesite. The Fe,Mg-chlorite (Al 2.89 Fe 3+ 0.24 Fe 2+ 6.42 Mn 0.21 Mg 2.08) 11.84 (Si 5.31 Al 2.79) 8 F 0.31 O 20 (OH) 8 corresponds to ripidolite and Mg,Fe-chlorite (Al 2.63 Fe 3+ 0.37 Fe 2+ 1.72 Mn 0.01 Mg 6.40 Ca 0.26) 11.39 (Si 6.02 Al 1.98) 8 O 20 (OH) 8 to pych-nochlorite. Chlorite geothermometry estimates a temperature for Fe,Mn-chlorite (scheelite I) from 400°C to 500°C, for Fe-chlorite (Mn-rich wolframite + scheelite II ± sulfide) from 250 to 350°C, for Fe,Mg-chlorite (Mo-mineralization) from 200°C to 250°C and for Mg,Fe-chlorite at ∼150°C. Oxygen isotopes (V-SMOW) yielded values of +3.8 (1σ) (Fe-chlorite), +6.91 (1σ) (Fe,Mn-chlorite) and +1.5 (1σ) (Fe,Mg-chlorite). The calculated δ 18 O F of Fe-and Fe,Mg-chlorite is ∼+3.75 (1σ) and +1.45 (1σ) for the mineralizing fluid, whereas for Fe,Mn-chlorite it is +8.17 (1σ). The δ 18 O data obtained from quartz in Wand Mo-mineralization yielded values of +12.6 and +11.4 (1σ), whereas for adularia δ 18 O is about +10 (1σ). These estimates allow us to conclude that the Fe,Mn-chlorite crystallized from a magmatic-hydrothermal fluid, whereas the Fe-and Fe,Mg-chlorite quartz and adularia resulted from a mixed contribution between meteoric and magmatic-hydrothermal fluid.
A B S T R A C T Coarse (2.0–0.2 μm) and fine (< 0.2 μm) clay fractions of NH 4-illite-smectite (I... more A B S T R A C T Coarse (2.0–0.2 μm) and fine (< 0.2 μm) clay fractions of NH 4-illite-smectite (IS) mixed-layered and K-illite/ (NH 4 , K)-illite (I) mixed phases that vary in age and trace element composition were collected from the fossil hydrothermal system of Harghita Bãi, East Carpathians. Boron and Li isotope ratios were measured by secondary ion mass spectrometry (SIMS), and N by isotope ratio mass spectrometry (IRMS) with the aim to characterize the isotope geochemistry and source of light elements fixed in authigenic NH 4-illitic clays. Boron in NH 4-IS clays ranges from 513 to 1457 ppm and reached ~1000 ppm in the K-I/(NH 4 , K)-I. The δ 11 B (‰) measured in NH 4-IS ranges from −12.6 to − 22.4 (± 0.3‰) and in K-I/(NH 4 , K)-I is consistently −5.5 to − 5.1 (± 0.3‰). Boron isotopes systematically become lighter in the NH 4-IS series as temperature increased from 90 to 270 °C. Low Li content (1 to 8 ppm) was found in illitic clay fractions. The δ 7 Li (‰) shows negative values ranging from − 8.6 to −12.3 (± 0.8‰) for the coarser (2.0–0.2 μm) NH 4-IS clays and from +4.3 to + 14.1 (± 1‰) for the finer (< 0.2 μm) fraction of NH 4-IS and K-I/(NH 4 , K)-I clays. The N (%) measured in the NH 4-IS clays ranges from 0.70 to 1.50 (± 0.2%), whereas in the K-I/(NH 4 , K)-I is about 0.70 (± 0.2%). The δ 15 N (‰) ranges from +4.8 to +7.4 (± 0.6) for most NH 4-IS and NH 4 , K-I clays, with one outlier for NH 4-IS of +14.6 (± 0.6). The δ 11 B of K-I/(NH 4 , K)-I clays reflect a magmatic source, whereas the NH 4-IS series is consistent with the influx of isotopically light-B waters derived from hydrothermal leaching of continental evaporites and/or organic rich sediments. The δ 7 Li signature measured on K-I/(NH 4 , K)-I clays also support a magmatic fluid, enriched in heavy Li, followed by precipitation of coarser NH 4-IS from more recent sedimentary contributions of isotopically light Li. This interpretation is also supported by the δ 15 N, which reflect an influx of waters from an organic sediment origin. The δ 15 N of + 14.6‰ (± 0.6) measured on NH 4-IS could be attributed to the presence of meteoric waters mixed with hydrothermal fluids. The isotopic data obtained trace the mobility of magmatic and organic – sedimentary components in the upper continental crust.
he Hercynian late-orogenic granites from the Gerês massif, northern Portugal, underwent intense h... more he Hercynian late-orogenic granites from the Gerês massif, northern Portugal, underwent intense hydrothermal activity along tectonic structures striking N-S and NE-SW. The first hydrothermal stage is characterized by the albitization of feldspars (primary K-feldspar and plagioclase) followed by the dis- solution of magmatic quartz, the chloritization of biotite, and the muscovitization of magmatic biotite and feldspars and occasionally of authigenic albite. Whole-rock geochemistry shows a decrease of SiO2, K2O and Rb and an increase of Na2 O, Al2 O3 and Sr amounts during the albitization. The second hydrothermal stage is characterized by a mineral assemblage consisting of secondary quartz, albite, chlorite, hematite, apatite, muscovite, epidote, sphene and carbonates, which infilled the cavities produced by the early quartz leaching. Mass balance calculations demonstrate a noticeable element mobilization during the granite alteration.
Environmental Science and Pollution Research, 2017
Acid mine waters (AMW) collected during high-and low-flow water conditions from the Lousal, Aljus... more Acid mine waters (AMW) collected during high-and low-flow water conditions from the Lousal, Aljustrel, and São Domingos mining areas (Iberian Pyrite Belt) were physicochemically analyzed. Speciation calculation using PHREEQC code confirms the predominance of Me n+ and Me–SO 4 species in AMW samples. Higher concentration of sulfate species (Me–SO 4) than free ion species (Me n+ , i.e., Al, Fe, and Pb) were found, whereas opposite behavior is verified for Mg, Cu, and Zn. A high mobility of Zn than Cu and Pb was identified. The sulfate species distribution shows that Fe 3+ –SO 4 2− , SO 4 2− , HSO 4 − , Al–SO 4 , MgSO 4 0 , and CaSO 4 0 are the dominant species, in agreement with the simple and mixed metal sulfates and oxy-hydroxysulphates precipitated from AMW. The saturation indices (SI) of melanterite and epsomite show a positive correlation with Cu and Zn concentrations in AMW, which are frequently retained in simple metal sulfates. Lead is well correlated with jarosite and alunite (at least in very acid conditions) than with simple metal sulfates. The Pb for K substitution in jarosite occurs as increasing Pb concentration in solution. Lead mobility is also controlled by anglesite precipitation (a fairly insoluble sulfate), where a positive correlation was ascertained when the SI approaches equilibrium. The zeta potential of AMW decreased as pH increased due to colloidal particles aggregation, where water species change from SO 4 2− to OH − species during acid to alkaline conditions, respectively. The AMW samples were supersaturated in schwertmannite and goethite, confirmed by the Me n+ –SO 4 , Me n+ –Fe–O–OH, or Me n+ –S–O–Fe–O complexes identified by attenuated total reflectance infrared spec-troscopy (ATR-IR). The ATR-IR spectrum of an AMW sample with pH 3.5 (sample L1) shows well-defined vibration plans attributed to SO 4 tetrahedron bonded with Fe-(oxy)hydroxides and the Me n+ sorbed by either SO 4 or Fe-(oxy)hydroxides. For samples with lower pH values (pH ~ 2.5—samples SD1 and SD4), the vibration plans attributed to Me n+ sorption are not evidenced, indicating its release in solution. The sorption of heavy metals on the first precipitated simple metal sulfates was ascertained by scanning electron microscopy coupled with X-ray spectrometry (SEM-EDX), where X-ray maps of Cu and Zn confirm a distribution of both metals in the melanterite structure.
Random and ordered mixed-layer smectite-ammonium illite (NH 4 -I/S) were identified by XRD analys... more Random and ordered mixed-layer smectite-ammonium illite (NH 4 -I/S) were identified by XRD analysis in the fossil hydrothermal system of Harghita Bãi (Eastern Carpathians, Romania). Morphologies of NH 4 -I/S were studied by SEM and TEM. SEM image of random NH 4 -I/S displays a cellular or cornflake texture. Ordered NH 4 -I/S (R=1) exhibits a scalloped morphology with curled edges. Ribbon crystals of illite rise from the surfaces of plate aggregates. Two generations of NH 4 -I are distinguished: one developed from a smectite precursor and another from a kaolinite precursor. Hairy illite and illite pseudomorphs after book-like aggregates of kaolinite are present. TEM images show the evolution of morphology from flake to lath habit during the smectite to illite conversion. Particles with veil characteristics and flake particles are observed in random mixed-layered NH 4 -I/S. Diffuse lath shaped illite developed on the previous morphology in the expandability range 7020 %S is observed. Euhedral lath shaped illite is present in NH 4 -I/S, below 10 %S. The reaction of smectite-to-illite is continuous, leading to lath shaped illite.
Journal of Radioanalytical and Nuclear Chemistry, 2015
Your article is protected by copyright and all rights are held exclusively by Akadémiai Kiadó, Bu... more Your article is protected by copyright and all rights are held exclusively by Akadémiai Kiadó, Budapest, Hungary. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identif... more Scheelitization of Mn-bearing wolframite, scheelite, quartz, and Fe,Mn-chlorite veins was identified in the W, (Cu,Mo) ore deposits of Borralha, by optical microscopy, electron-microprobe analysis, and stable isotope geochemistry. Fluid inclusions derived scheelite crystallization temperature was compared with the oxygen isotope temperature estimated. Scheelite was formed mainly during stage I from a low salinity aqueous-carbonic fluid dominated by CO2, where the homogenization temperature (Th) decreased from 380 °C to 200 °C (average of 284 °C). As temperature decreased further, the aqueous-carbonic fluid became dominated by CH4 (Stage II; (average Th = 262 °C)). The final stage III corresponds to lower temperature mineralizing aqueous fluid (average Th = 218 °C). In addition, salinity gradually decreased from 4.8 wt.% to 1.12 wt.%. The δ18OFluid values calculated for quartz-water and wolframite-water fractionation fall within the calculated magmatic water range. The ∆quartz-scheel...
Sorbents Materials for Controlling Environmental Pollution, 2021
Abstract This chapter introduces the role of engineered clay barriers in multibarrier systems in ... more Abstract This chapter introduces the role of engineered clay barriers in multibarrier systems in the control of radioactive contamination from nuclear waste, which is an imperative challenge nowadays. Currently the electricity demand is increasing rapidly, whereas the CO2 concentration in the atmosphere is reaching a critical level. In this regard, nuclear energy has aroused particular interest, once it is the only energy source that may suppress, at the same time, the world’s growing energy needs and the carbon emissions. Nevertheless, one major concern related to nuclear power is the generation of radioactive wastes, which are disposed in specific landfills and require specialized management. The nature of these hazardous wastes, the main sources of radioactive contamination, the adsorption mechanisms involved in the interaction contaminant/clay mineral, and the role of clay barrier systems in the containment process are discussed in this chapter.
Organic carbon and nitrogen fixed in illite (I) clays were identified in a hydrothermal breccia s... more Organic carbon and nitrogen fixed in illite (I) clays were identified in a hydrothermal breccia structure from the Harghita Bãi area of the Neogene volcanism of the East Carpathians. The potassium-illite (K-I) alteration related to an early magmatic-hydrothermal event (9.5 ± 0.5 Ma) was later replaced by ammonium-illite (NH4-I) (6.2 ± 0.6 Ma) owing to circulation of an organic-rich fluid. Several textural evolutions of breccia structures were recognized, such as ‘shingle’, ‘jigsaw’, ‘crackle’ and hydraulic in situ fractures. The high-field-strength element behaviours of the K-I and NH4-I argillic altered andesite are close to chondritic ratios, indicating no contribution of hydrothermal fluid, especially on NH4-I andesite alteration and the CHArge-and-RAdius-Controlled (CHARAC) behaviour within silicate melts. The rare earth element normalized patterns show two distinct trends, one with a Eu* anomaly (K-I) and the other with a Nd* anomaly (NH4-I), indicating a boundary exchange with...
Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4+-fixation in ... more Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4+-fixation in illitic clays is relevant for the N-input budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic-altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1M d and 1M polytypes were identified by selected area electron diffraction patterns. Crystal chemistry ...
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Articles by Iuliu BOBOS
effect), thus contributing to significant climate changes (Casper, 2010;
Muthu, 2019). Therefore there is a clear need for a new generating capacity around the world to replace old fossil fuel units and to meet the increased demand for electricity in many countries. Despite the continuing rapid growth in renewable energy in recent years, it only provides a one-third of the required increase in power generation and will take a substantial period of time to become established (Kantenbacher and Shirley, 2018). Therefore nuclear energy is the only energy source that may suppress,at the same time, the world’s growing energy needs and the carbon emissions (Joyce, 2018a; Valayer et al., 2019).
+-fixation in illitic clays is relevant for the N-input
budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic-
altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared
spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite
rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between
packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast
across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by
selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer
cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12%
smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant
lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight
and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets
with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals
within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.
Mass balance calculations demonstrate a noticeable element mobilization during the granite alteration.
The average REE of the Gerês granite is nearly constant at 154 ppm, but ranges from 91 to 163 ppm in the altered rocks. A relative LREE depletion and a slight HREE enrichment associated with a negative
Eu anomaly characterize the feldspathization process of Gerês granite. The average REE of the Carris granite is at 159 ppm but in the altered epidote + chlorite + hematite assemblage it reaches about 201 ppm with a slight HREE increase.
Two different fluids were involved in the hydrothermal alteration. A first aqueous fluid (Lw1), with a low to intermediate salinity (<10 wt.% eq. NaCl) circulated along the main structures (N-S, NE-SW and NW-SE), characterized by entrapment temperature lower than 350 ◦ C and maximum pressure of 115 MPa followed by a later colder and more saline fluid (Lw2) under a temperature of 220◦C and a pressure of about 27 MPa.
Oxygen isotope data obtained on magmatic quartz indicate 18 Oquartz of + 9.3 and + 11.0‰, pointing to an interaction of magmatic fluids with others of meteoric origin. For the secondary quartz, 18Owater of +0.5 and +0.7‰ were calculated for a temperature of 250 ◦ C, suggesting a meteoric fluid with a possible seawater signature.
The K-Ar data of K-feldspar from the altered rocks confirm an age of 273.6 ± 11.7 Ma, attributed to the first alteration process. Younger K-Ar ages between 155.8 ± 6.7 Ma and 124 ± 5.3 Ma were also obtained in the feldspathized rocks, confirming the late hydrothermal activity.
Albitization and quartz dissolution of granitic rocks from the Gerês massif occurred at depths shallower than 5 km, induced by the circulation of fluids along brittle structures, during the orogenic uplift and extensional tectonics which affected the Iberian Massif in the Early Permian. A second major event is attributed to late hydrothermal circulations of aqueous brines until a depth of about 3 km, presumably derived from interaction with sub-surface evaporites throughout Late Jurassic to Early Cretaceous. These late hydrothermal events probably reflect the rifting episodes and the rising of geothermal gradient, associated with the opening of the Atlantic Ocean and Gulf of Biscay, respectively.
© 2016 Elsevier GmbH. All rights reserved.
effect), thus contributing to significant climate changes (Casper, 2010;
Muthu, 2019). Therefore there is a clear need for a new generating capacity around the world to replace old fossil fuel units and to meet the increased demand for electricity in many countries. Despite the continuing rapid growth in renewable energy in recent years, it only provides a one-third of the required increase in power generation and will take a substantial period of time to become established (Kantenbacher and Shirley, 2018). Therefore nuclear energy is the only energy source that may suppress,at the same time, the world’s growing energy needs and the carbon emissions (Joyce, 2018a; Valayer et al., 2019).
+-fixation in illitic clays is relevant for the N-input
budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic-
altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared
spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite
rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between
packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast
across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by
selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer
cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12%
smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant
lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight
and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets
with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals
within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.
Mass balance calculations demonstrate a noticeable element mobilization during the granite alteration.
The average REE of the Gerês granite is nearly constant at 154 ppm, but ranges from 91 to 163 ppm in the altered rocks. A relative LREE depletion and a slight HREE enrichment associated with a negative
Eu anomaly characterize the feldspathization process of Gerês granite. The average REE of the Carris granite is at 159 ppm but in the altered epidote + chlorite + hematite assemblage it reaches about 201 ppm with a slight HREE increase.
Two different fluids were involved in the hydrothermal alteration. A first aqueous fluid (Lw1), with a low to intermediate salinity (<10 wt.% eq. NaCl) circulated along the main structures (N-S, NE-SW and NW-SE), characterized by entrapment temperature lower than 350 ◦ C and maximum pressure of 115 MPa followed by a later colder and more saline fluid (Lw2) under a temperature of 220◦C and a pressure of about 27 MPa.
Oxygen isotope data obtained on magmatic quartz indicate 18 Oquartz of + 9.3 and + 11.0‰, pointing to an interaction of magmatic fluids with others of meteoric origin. For the secondary quartz, 18Owater of +0.5 and +0.7‰ were calculated for a temperature of 250 ◦ C, suggesting a meteoric fluid with a possible seawater signature.
The K-Ar data of K-feldspar from the altered rocks confirm an age of 273.6 ± 11.7 Ma, attributed to the first alteration process. Younger K-Ar ages between 155.8 ± 6.7 Ma and 124 ± 5.3 Ma were also obtained in the feldspathized rocks, confirming the late hydrothermal activity.
Albitization and quartz dissolution of granitic rocks from the Gerês massif occurred at depths shallower than 5 km, induced by the circulation of fluids along brittle structures, during the orogenic uplift and extensional tectonics which affected the Iberian Massif in the Early Permian. A second major event is attributed to late hydrothermal circulations of aqueous brines until a depth of about 3 km, presumably derived from interaction with sub-surface evaporites throughout Late Jurassic to Early Cretaceous. These late hydrothermal events probably reflect the rifting episodes and the rising of geothermal gradient, associated with the opening of the Atlantic Ocean and Gulf of Biscay, respectively.
© 2016 Elsevier GmbH. All rights reserved.