Leaching Of Rocks Research Articles

Bioavailable 87Sr/86Sr in different environmental samples — Effects of anthropogenic contamination and implications for isoscapes in past migration studies

87Sr/86Sr reference maps (isoscapes) are a key tool for investigating past human and animal migrations. However, there is little understanding of which biosphere samples are best proxies for local bioavailable Sr when dealing with movements of past populations. In this study, biological and geological samples (ground vegetation, tree leaves, rock leachates, water, soil extracts, as well as modern and archeological animal teeth and snail shells) were collected in the vicinity of two early medieval cemeteries (“Thuringians”, 5–6th century AD) in central Germany, in order to characterize 87Sr/86Sr of the local biosphere. Animal tooth enamel is not appropriate in this specific context to provide a reliable 87Sr/86Sr baseline for investigating past human migration. Archeological faunal teeth data (pig, sheep/goat, and cattle) indicates a different feeding area compared to that of the human population and modern deer teeth 87Sr/86Sr suggest the influence of chemical fertilizers. Soil leachates do not yield consistent 87Sr/86Sr, and 87Sr/86Sr of snail shells are biased towards values for soil carbonates. In contrast, water and vegetation samples seem to provide the most accurate estimates of bioavailable 87Sr/86Sr to generate Sr isoscapes in the study area. Long-term environmental archives of bioavailable 87Sr/86Sr such as freshwater bivalve shells and tree cores were examined in order to track potential historic anthropogenic contamination of the water and the vegetation. The data obtained from the archeological bivalve shells show that the modern rivers yield 87Sr/86Sr ratios which are similar to those of the past. However, the tree cores registered decreasing 87Sr/86Sr values over time towards present day likely mirroring anthropogenic activities such as forest liming, coal mining and/or soil acidification. The comparison of 87Sr/86Sr of the Thuringian skeletons excavated in the same area also shows that the vegetation samples are very likely anthropogenically influenced to some extent, affecting especially 87Sr/86Sr of the shallow rooted plants.

Ultrafresh salty kimberlite of the Udachnaya–East pipe (Yakutia, Russia): A petrological oddity or fortuitous discovery?

An ultrabasic/ultramafic composition of kimberlite magmas is difficult to reconcile with existing models of the kimberlite mantle source and melting conditions, inferred magma temperatures and rheological properties, and the style of magma ascent and emplacement. The inconsistencies in current thinking indicate serious flaws in understanding kimberlite magma compositions. Much of the uncertainty over true kimberlite compositions may stem from almost ubiquitous hydration and leaching of kimberlite rocks. This study presents petrographic and geochemical data for kimberlite samples largely unaffected by postmagmatic modification, from the Devonian Udachnaya–East pipe in Siberia. These samples are unusually enriched in chlorine and sodium, yet they are essentially anhydrous. These features are consistent with the phase composition of the groundmass which is dominated by minerals such as Na-Ca carbonates, Na–K chlorides and sulphates which appear to be – in our samples – co-magmatic with common silicates and oxides, but are unknown in other kimberlites, or rarely found within magmatic assemblages. We suggest that a kimberlite parent melt of essentially non-silicate composition, with high concentrations of alkalis, CO2 and Cl may be a viable alternative to the currently favoured water-rich, high-Mg model primary melt. Entrainment of mantle silicates into such a melt en route to the surface, followed by gravitational accumulation of mantle olivine and liquidus oxides (perovskite, Cr-spinel) at the bottom of vertically extensive magma bodies after emplacement, would explain the observed properties of kimberlite magma/rock, notably enrichment in olivine and trace elements in the hypabyssal kimberlite facies. A carbonate melt composition would retain attributes of the standard model such as trace element enrichment via low degrees of partial melting, it would explain low temperatures of crystallisation and the exceptional rheological properties that enable kimberlite primary melts to segregate from the lithospheric source and buoyantly ascend at high speed, while mixing and reacting with country rocks.

Formation and fate of gold thiosulfate under the leaching of sulfide rocks (experimental study)

Formation and fate of gold thiosulfate under the leaching of sulfide rocks (experimental study)

Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars

[1] The presence of outcrops and soil (regolith) rich in opaline silica (∼65–92 wt % SiO2) in association with volcanic materials adjacent to the “Home Plate” feature in Gusev crater is evidence for hydrothermal conditions. The Spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity, abundance, and fate of water in the first hydrothermal system to be explored in situ on Mars. We apply spectral, chemical, morphological, textural, and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks, by precipitation from silica-rich solutions, or by some combination. The apparent lack of S enrichment and the relatively low oxidation state of the Home Plate silica-rich materials appear inconsistent with the originally proposed Hawaiian analog for fumarolic acid sulfate leaching. The stratiform distribution of the silica-rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation. There is no evidence for crystalline quartz phases among the silica occurrences, an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase.

Hydrologic and geologic factors controlling groundwater geochemistry in the Turonian aquifer (southern Tunisia)

Water in the fissured limestone and dolomite of the Turonian aquifer of Tunisia has been investigated using geochemical (major ions) and isotopic (δ18O, δ2H, 14C) data. To carry out a characterization of aquifer behaviour, 48 representative samples were collected at the end of the humid season. The evolution of chemical composition of groundwater from recharge areas to discharge areas is characterized by increasing sodium, chloride and sulphate contents as a result of leaching of evaporite rock. In the study, three distinct chemical trends in groundwater were identified. The major reactions responsible for the chemical evolution of groundwater in the investigated area fall into three categories: (1) calcite precipitation, (2) gypsum and halite dissolution, and (3) ion exchange. The stable isotope composition of water samples indicates large-scale interaction between the Continental Intercalaire and the Turonian aquifer and the presence of a young local component which probably enters the system via faults and/or fractures.

Silica deposits in the Nili Patera caldera on the Syrtis Major volcanic complex on Mars

The martian surface features abundant volcanoes and evidence for past liquid water. Extant or relict martian volcanic hydrothermal systems have therefore been sought in the pursuit of evidence for habitable environments. The Mars Exploration Rover, Spirit, detected deposits highly enriched in silica with accessory minerals, suggesting formation by hydrothermal leaching of basaltic rocks by low-pH solutions. However, extensive erosion has obscured the context of the formation environment of these deposits. Silica deposits have also been identified remotely, but also with limited contextual clues to their formation; aqueous alteration products of basalt and volcanic ash are the most likely sources. Here we report the detection from orbit of hydrated silica deposits on the flanks of a volcanic cone in the martian Syrtis Major caldera complex. Near-infrared observations show dozens of localized hydrated silica deposits. As a result of the morphology of these deposits and their location in and around the cone summit, we suggest that the deposits were produced by a volcanically driven hydrothermal system. The cone and associated lava flows post-date Early Hesperian volcano formation. We conclude that, if a relict hydrothermal system was associated with the silica deposits, it may preserve one of the most recent habitable microenvironments on Mars.

Extreme alteration by hyperacidic brines at Kawah Ijen volcano, East Java, Indonesia: I. Textural and mineralogical imprint

Kawah Ijen volcano, located on the eastern tip of Java and renowned for its large hyperacidic crater lake, poses significant volcanic and environmental hazards to its immediate surroundings. Crater lake brines seep through the flanks of the volcano to form the Banyu Pahit river, which is used in irrigation downstream, resulting in extensive pollution, sharply reduced crop yields and health problems. The impact on the environment comes mainly from the high element load, which is derived from leaching of rocks by the acid fluids and transported downstream. Our detailed study of water–rock interaction in different parts of the Kawah Ijen system indicates that there are three settings for this alteration; the crater lake and Banyu Pahit riverbed, the hydrothermal system below the lake, and the solfatara of the active rhyolite dome. In all three settings, the silicates are leached and altered to amorphous silica in the order olivine + glass > An-rich plagioclase > ortho-pyroxene > clino-pyroxene > Ab-rich plagioclase. In contrast, the alteration of titanomagnetite is characterised by dissolution in the surficial setting, replacement by pyrite and Ti-oxide in the hydrothermal system and pyritisation + Ti-mobility in the fumarole conduits. Alteration progresses along crystallographically controlled planes in all phases, and shows strong compositional control in plagioclase and titanomagnetite. No secondary minerals develop, except for minor barite, cristobalite, pyrite and jarosite. This indicates that, despite its high element load, the waters are undersaturated with respect to most secondary minerals typically produced during alteration of these magmatic rocks by acid chloride-sulphate brines, and that water–rock interaction at Kawah Ijen is not a sink of elements, but rather contributes to the element load transported downstream.

Sources and composition of fluids associated with fluorite deposits of Asturias (N Spain)

AbstractThe fluorite deposits of Asturias (northern Iberian Peninsula) are hosted by rocks of Permo‐Triassic and Palaeozoic age. Fluid inclusions in ore and gangue minerals show homogenization temperatures from 80 to 170°C and the presence of two types of fluids: an H2O–NaCl low‐salinity fluid (<8 eq. wt% NaCl) and an H2O–NaCl–CaCl2 fluid (7–13 wt% NaCl and 11–14 wt% CaCl2). The low salinity and the Cl/Br and Na/Br ratios (Cl/Brmolar 100–700 and Na/Brmolar 20–700) are consistent with an evaporated sea water origin of this fluid. The other end‐member of the mixture was highly saline brine with high Cl/Br and Na/Br ratios (Cl/Brmolar 700–13 000 and Na/Brmolar 700–11 000) generated after dissolution of Triassic age evaporites. LA‐ICP‐MS analyses of fluid inclusions in fluorite reveal higher Zn, Pb and Ba contents in the high‐salinity fluids (160–500, 90–170, 320–480 p.p.m. respectively) than in the low‐salinity fluid (75–230, 25–150 and 100–300 p.p.m. respectively). The metal content of the fluids appears to decrease from E to W, from Berbes to La Collada and to Villabona. The source of F is probably related to leaching of volcanic rocks of Permian age. Brines circulated along faults into the Palaeozoic basement. Evaporated sea water was present in permeable rocks and faults along or above the unconformity between the Permo‐Triassic sediments and the Palaeozoic basement. Mineralization formed when the deep brines mixed with the surficial fluids in carbonates, breccias and fractures resulting in the formation of veins and stratabound bodies of fluorite, barite, calcite, dolomite and quartz and minor amounts of sulphides. Fluid movement and mineralization occurred between Late Triassic and Late Jurassic times, probably associated with rifting events related to the opening of the Atlantic Ocean. This model is also consistent with the geodynamic setting of other fluorite‐rich districts in Europe.

Auriferous Precambrian conglomerates of Witwatersrand

Geological and mineralogical specificity of the world’s largest Witwatersrand gold deposit was defined by geodynamic processes in the Late Archean. The primary crust composed of felsic rocks (“gray gneisses”) was intruded 2.9–3.1 Ga ago by mafic melts that gave rise to greenstone belts. This was followed by the appearance of long-lived granulite mobile zones that promoted the formation of hydrosphere and atmosphere accompanied by an intense acidic leaching (weathering) of rocks in the greenstone belts. Numerous conglomerate interbeds were formed in the Witwatersrand Basin section due to vigorous eolian processes and floodwater washouts that produced a fan channel system mainly filled with quartz pebbles. At present, most researchers support a modified paleoplacer model of the origin of gold mineralization in Witwatersrand, suggesting a hydrothermal-metamorphic redistribution of the primary placer gold. According to various hydrothermal models, gold was introduced into sedimentary rocks in a water medium from outer deep sources or during the filtration of postsedimentary hydrothermal fluids. The present communication suggests that a significant portion of gold contained in reefs could be delivered to the sedimentation basin by the auriferous hydrothermal quartz of pebble or sand dimension that was metamorphosed at approximately 350–400°C. Metamorphism of gold was accompanied by its purification, transfer to matrix, and hydrothermal intrastratal redistribution.

Genetic Aspects of the Manto‐type Copper Deposits Based on Geochemical Studies of North Chilean Deposits

AbstractRecent studies on mineralogy, geochronology, fluid inclusion and stable isotope (Pb, Os, S, C, O, Sr) characteristics were reviewed to determine constraints for genetic models of the Chilean manto‐type copper deposits. The Chilean manto‐type deposits are divided into the two geologic categories of the northern areas (Arica–Iquique, Tocopilla–Taltal) and the central areas (Copiapó, La Serena, Santiago). The former is distributed in the coastal range composed of Jurassic andesite‐dominated volcano‐sedimentary piles and younger plutonic intrusions, and yields chalcocite (‐digenite) and bornite as the principal hypogene copper sulfides. The latter is hosted mostly in Lower Cretaceous volcano‐sedimentary sequences, and has chalcopyrite‐rich mineral associations. The fluid inclusion data indicate that the primary copper mineralization was commonly generated in the temperature range 150–360°C under low‐pressure conditions near the boiling curve, mediated with relatively saline brines. Generally, homogeneous Pb and S isotope compositions for primary copper minerals imply direct magma source or leaching of igneous rocks. Pb and Os isotope data published for some deposits, however, suggest that ore‐forming metals were derived mainly from the volcano‐sedimentary host rocks. The noticeably negative isotope ratios of primary sulfide sulfur and hydrothermal calcite carbon of some central area deposits indicate influx of sedimentary rock components, and the high 87Sr/86Sr initial ratios of hydrothermal calcite from the Tocopilla–Taltal area deposits imply contribution of the contemporaneous seawater or marine carbonates. These isotopic constraints imply a formation mechanism in which the Chilean manto‐type copper deposits formed epigenetically in the process of hydrothermal interaction of non‐magmatic surface‐derived brine with the volcano‐sedimentary host rocks, which is inferred to have been induced by a deep‐seated plutonic complex as the possible heat source.

REE Mineralization of Weathered Crust and Clay Sediment on Granitic Rocks in the Sanyo Belt, SW Japan and the Southern Jiangxi Province, China

AbstractRare earth element (REE) geochemistry and mineralogy have been studied in the weathered crusts derived from the Early Yanshanian (Jurassic) biotite granites of Dabu and Dingnan, as well as in the Indosinian (Permian) muscovite–biotite granite of Aigao in southern Jiangxi province, China, and the weathered crusts and clay sediments on biotite granites in the Sanyo belt, SW Japan, that is, Okayama, Tanakami, and Naegi areas. In all of the weathered crusts, biotite and plagioclase commonly tend to decrease toward the upper part of the profile, whereas kaolinite and residual quartz and K‐feldspar increase. The weathered crusts of the Dingnan granites and some Naegi granites, which are characterized by the enrichment in light REE (LREE) in C horizons, have higher total REE (ΣREE) content than the parent REE‐enriched granites. Weathering of LREE‐bearing apatite and fluorocarbonates in the Dingnan granites and allanite and apatite in some Naegi granites may account for the leaching of LREE at the B horizons. The leached LREE must result in subsequent enrichment of LREE in the C horizons. The enrichment is probably associated with mainly adsorption onto kaolinite and partly formation of possible secondary LREE‐bearing minerals. In Japan it was found that REE mineralization occurs not in the weathered granitic crusts but in reworked clay sediments, especially kaolinite‐rich layers, derived mainly from the weathering materials of REE‐enriched granitic rocks. The clay sediments are more enriched in LREE, which likely adsorbed onto kaolinite. Concentration of heavy REE within almost all the weathered crusts and clay sediments, however, may reflect mainly residual REE‐bearing minerals such as zircon, which originated in the parent granitic rocks. The findings of the present study support the three processes for fractionation of the REE during weathering: (i) selective leaching of rocks containing both stable and unstable REE‐bearing minerals; (ii) adsorption onto clay minerals; and (iii) presence of possible secondary LREE‐bearing minerals.

Origin and evolution of two contrasting thermal groundwaters (CO 2-rich and alkaline) in the Jungwon area, South Korea: Hydrochemical and isotopic evidence

In the Jungwon area, South Korea, two contrasting types of deep thermal groundwater (around 20–33 °C) occur together in granite. Compared to shallow groundwater and surface water, thermal groundwaters have significantly lower δ 18O and δD values (> 1‰ lower in δ 18O) and negligible tritium content (mostly < 2 TU), suggesting a relatively high age of these waters (at least pre-thermonuclear period) and relatively long subsurface circulation. However, the hydrochemical evolution yielded two distinct water types. CO 2-rich water ( P CO 2 = 0.1 to 2 atm) is characterized by lower pH (5.7–6.4) and higher TDS content (up to 3300 mg/L), whereas alkaline water ( P CO 2 = 10 − 4.1 –10 − 4.6 atm) has higher pH (9.1–9.5) and lower TDS (< 254 mg/L). Carbon isotope data indicate that the CO 2-rich water is influenced by a local supply of deep CO 2 (potentially, magmatic), which enhanced dissolution of silicate minerals in surrounding rocks and resulted in elevated concentrations of Ca 2+, Na +, Mg 2+, K +, HCO 3 − and silica under lower pH conditions. In contrast, the evolution of the alkaline water was characterized by a lesser degree of water–rock (granite) interaction under the negligible inflow of CO 2. The application of chemical thermometers indicates that the alkaline water represents partially equilibrated waters coming from a geothermal reservoir with a temperature of about 40 °C, while the immature characteristics of the CO 2-rich water resulted from the input of CO 2 in Na–HCO 3 waters and subsequent rock leaching.

Formation of oil and gas fields

Cycles of the geosynclinal-orogenic-platformal development of the continental crust are separated by natural phases of crustal destruction. They are determined by pulses of degassing of the Earth’s core marked by decelerated inversions of the magnetic field. Such pulses occur under the influence of fluid flows that ascend from the core and loss hydrogen. Consequently, the fluids acquire acidic properties and become aggressive to rocks of the continental crust (H2 + 2CO = H2 O + 0.5CO2 + 1.5C). Oceanization of the continental crust represents the main result of its destruction accompanied by the formation of seas and sedimentary basins largely on the underwater margins of continents. Development of geodynamic compression setting of the Earth’s crust due to its evolution creates conditions that impede the loss of hydrogen from ascending fluid flows. Consequently, they acquire the ability to generate hydrocarbons (4H2 + 2CO = 2H2O + CH4 + C) and produce oil and gas pools. This setting is marked by intrusions of alkaline rocks with characteristic water-hydrocarbon inclusions in minerals and by the development of fold-thrust and reversed fault dislocations in depressions. The dislocations controlled not only the fluid-related leaching of rocks, but also the distribution of oil and gas pools within both sedimentary basins and their basement.

Mineralogical sources of the buffer capacity in a granite catchment determined by strontium isotopes

Abstract The role of different minerals in base cation release and thus the increase of buffering capacity of groundwater against acid deposition is controversially discussed in the literature. The 87Sr/86Sr ratios and base cation concentration were investigated in whole rock leachates, mineral separates, precipitation, soil solution, groundwater and stream water samples in the Lehstenbach catchment (Germany) to identify the weathering sequence of the granite bedrock. Three different approaches were followed in parallel. It was assumed that the contribution of different minerals to base cation supply of the groundwater with increasing weathering intensity would be observed by investigating (1) unweathered rock leachates, deep groundwater and shallow groundwater, (2) groundwater samples from new groundwater wells, reflecting the initial weathering of the drilled bedrock, and groundwater from wells that were drilled in 1988, (3) stream water during baseflow, dominated by deep groundwater, and stream water during high flow, being predominantly shallow groundwater. Whereas the first approach yielded consistent patterns, there was some evidence that groundwater from the new wells initially reflected contamination by the filter gravel rather than cation release in an initial stage of weathering. Time series samples of stream water and groundwater solute concentrations and isotope ratios turned out to reflect varying fractions of soil water and precipitation water at baseflow and high flow conditions rather than varying contributions of different minerals that prevail at different stages of granite weathering. The early phase of weathering was clearly dominated by base cation release from biotite weathering and to a lesser extent by apatite dissolution. Feldspars contributed to base cation release as well, but could not be regarded as endmembers of the mixing diagram. There was no clear evidence for a contribution from calcite. Correspondingly, base cation input by atmospheric deposition and liming had only minor effects on groundwater buffer capacity.

Natrolitite, an unusual rock — Occurrence and petrographic and geochemical characteristics (Eastern Turkey)

AbstractVery unusual rocks consisting of natrolite (&gt;95 vol.%) ± pargasite (&lt;5 vol.%) and rarealbite (&lt;1 vol. %) have been discovered in the Kop mountain range, eastern Turkey. We propose to call these rocks ‘natrolitite’ and ‘pargasite natrolitite’. They were produced by Na Si metasomatism of dikes and stocks of diorite through replacement of the intermediate primary igneous plagioclase to produce natrolite. The metasomatic alteration produced concentric elliptical zones characterized by distinct mineral assemblages centered on intrusions of diorite. The Central Zone 1 consists of variably albitized diorite with preserved magmatic textures (albite ± andesine ± pargasite ± quartz). Transition Zone 2 comprises natrolite-bearing diorite (natrolite ± albite ± andesine ± pargasite ± calcite ± quartz). Marginal Zone 3 is a rock made up almost entirely of natrolite (natrolite ± pargasite ± albite ± calcite ± chlorite). Outer Zone 4 occurs along the boundary between the natrolitite and the surrounding serpentinite and consists of listvenite, a rock which comprises magnesite, quartz, calcite, mica, talc, and hematite, indicating a role for CO2 in the metasomatic reactions, consistent with the presence of calcite in the alteration zones. Zone 5 consists essentially of brecciated serpentinite with numerous hydrothermal quartz veins and calcite veins. Whole-rock compositions document an increase in Na2O, Al2O3, and H2O from the core (central zone) to themargin while CaO, MgO, and SiO2 decrease. Plagioclase abundance and composition also varies outwards from the central core rocks where it occurs as a primary magmatic phase (∼95 vol.% An41−38) to the alteration zones (&lt;5 vol.% An32−37) due to partial to complete replacement of plagioclase by natrolite with or without rare albite. The natrolites exhibit little variation in Si/Al ratios, ranging between 1.45 and 1.61, and are similar in composition to those reported in the literature. Accompanying pargasitic amphibole also becomes progressively more sodic in composition from the core rocks to the marginal zone rocks. Our analysis indicates that albitization preceded the formation of natrolite and that the formation of natrolite, instead of other more typical alteration minerals (e.g. analcime and paragonite), reflects Na metasomatism at lower chemical potentials for Al2O3 and SiO2. Potential sources of Na could be hypersaline brines or leaching of country rocks, such as trondhjemites. The fluids were driven in hydrothermal convection cells set up by theintrusion of thediorites.

Geochemical characterization of surface waters and groundwater resources in the Managua area (Nicaragua, Central America)

Abstract This paper reports new geochemical data on dissolved major and minor constituents in surface waters and ground waters collected in the Managua region ( Nicaragua ), and provides a preliminary characterization of the hydrogeochemical processes governing the natural water evolution in this area. The peculiar geological features of the study site, an active tectonic region (Nicaragua Depression) characterized by active volcanism and thermalism, combined with significant anthropogenic pressure, contribute to a complex evolution of water chemistry, which results from the simultaneous action of several geochemical processes such as evaporation, rock leaching, mixing with saline brines of natural or anthropogenic origin. The effect of active thermalism on both surface waters (e.g., saline volcanic lakes) and groundwaters, as a result of mixing with variable proportions of hyper-saline geothermal Na–Cl brines (e.g., Momotombo geothermal plant), accounts for the high salinities and high concentrations of many environmentally-relevant trace elements (As, B, Fe and Mn) in the waters. At the same time the active extensional tectonics of the Managua area favour the interaction with acidic, reduced thermal fluids, followed by extensive leaching of the host rock and the groundwater release of toxic metals (e.g., Ni, Cu). The significant pollution in the area, deriving principally from urban and industrial waste-water, probably also contributes to the aquatic cycling of many trace elements, which attain concentrations above the WHO recommended limits for the elements Ni (∼40 μg/l) and Cu (∼10 μg/l) limiting the potential utilisation of Lake Xolotlan for nearby Managua.

Low-sulfidation type Au–Ag mineralization at Bergama, Izmir, Turkey

Bergama, the center of Bergama County, is located in western Turkey and includes the villages of Ovacik, Narlica and Saganci. The Ovacik epithermal gold–silver deposit is located in the Western Anatolian Volcanic and Extensional Province, adjacent to the ENE-trending Bergama graben, some 100 km north of the city of Izmir. Gold of economic grades at the Ovacik deposit (reserves 4.19 Mt at 7.6 g/t) occurs in epithermal quartz veins which display low-temperature epithermal textures, including crustiform banding, quartz pseudomorphs after bladed calcite, and multiphase hydrothermal breccias. Alteration minerals at both Ovacik and Narlica are dominated by smectite, mixed-layer illite/smectite, chalcedonic quartz and adularia, whereas major kaolinite and minor mixed-layer smectite/illite (> 13.4 Å) occur at Saganci. The total sulfide content at Ovacik is low (< 2%) and is dominated by pyrite with traces of electrum, chalcopyrite, arsenopyrite, acanthite, tetrahedrite, pyrargyrite, stibnite, galena, chalcocite, bornite, covellite and sphalerite, occurring mainly within breccia clasts. Pyrite and marcasite appear to be the most common opaque minerals at Narlica and form dark sulfide-rich bands along with traces of electrum, native silver and chalcopyrite; pyrite is the only sulfide identified at Saganci. 40Ar/ 39Ar dating of adularia from gold-bearing quartz veins indicates an age of mineralization of about 18.2 ± 0.2 Ma. Fluid inclusion studies at Ovacik reveal that main-stage quartz contains predominantly liquid-rich inclusions with homogenization temperatures ( T h) ranging from 150 to 305 °C, with the majority of T h varying between 165 to 205 °C: ice-melting temperatures ( T m) ranging from − 0.4 to − 1.2 °C (salinity < 2 wt.% NaCl equiv.) are dominant. Higher T h (220 to 248 °C) at the Narlica deposit may be attributed to the deeper level of exposure. Geochemical variations in altered wall rocks at Ovacik and Narlica are generally characterized by two-fold enrichments in K, Rb, Cs and 25 to 93% depletions in Sr, Ca, Mg, Na and even higher depletions (96 to 99% decrease) in the quartz–adularia vein zone. Lanthanum, Ce, Pr, Hf, Zr, Sm, Eu, Gd, Tb and Ho also exhibit up to 50% depletions in the wall rock and even more so (up to 90% depletion for La and Nd) in the vein structure. Wall rock enrichment in Au, Ag, As, Hg and Sc is by factors of 60, 150, 88, 8 and 3, respectively. The ranges of REE in both the altered volcanic rocks and quartz–adularia veins are wide and may reflect either significant mobilization of REE during alteration and mineralization or their dilution by the metasomatic processes from fresh volcanic rocks through montmorillonite–illite–adularia-altered wallrock to quartz–adularia veins. High Rb/Sr ratios in adularia–illite-altered areas are closely related to the presence of K-rich alteration minerals. Low Rb/Sr ratios and corresponding low K values at Saganci are due to acid leaching of volcanic rocks. Positive correlation coefficients between Au and Ag, Pb, Zn, Cd, Cu and Sb in epithermal quartz veins, all of which are > 0.51, are significant. Silver and Sb are remarkably enriched at higher levels of the deposit. No correlation occurs between Au and As or Ag and As. The Ovacik quartz in Au–Ag-bearing veins has δ 18O values ranging from + 9.5 to + 15.7‰, whereas δD values of fluid inclusions in quartz range from − 89 to − 125‰. However, the Narlica quartz in Au–Ag bearing veins returned δ 18O values ranging from + 5.9‰ to + 8.3, whereas the δD values of fluid inclusion in quartz range from − 82 to − 99‰. δ 18O results indicate that ore-forming hydrothermal fluids at Ovacik and Narlica had δ 18O H2O values ranging from − 2.9 to + 3.5‰ (average: − 0.24‰) and from − 2.96 to − 0.6 (average − 1.6), respectively. They are thus 18O-enriched in comparison with present-day meteoric and hydrothermal meteoric waters (− 5.4‰). δ 18O, δ 18O H2O and δD values suggest that mineralizing solutions were a mixture of meteoric and magmatic waters. The δ 34S Σsulfide data at Ovacik and Narlica range from − 2.1 to 5.3‰ (average: + 1.7) and from − 4.6 to + 2.7‰ (average: − 0.36), respectively. These δ 34S Σsulfide values are consistent with a magmatic source for S.

Enhanced flow injection leaching of rocks by focused microwave heating with in-line monitoring of released elements by inductively coupled plasma mass spectrometry

A focused microwave digestion system was used to heat a mini-column of sample of crushed rock (hematite) during its successive leaching by repeated 250-μL injections of water, HNO 3 1%, 10% and 30% (v/v). The mini-column was connected to the nebulizer of an inductively coupled plasma mass spectrometry instrument, which allowed a continuous monitoring of the progressive release of elements by a given leaching reagent. Quantitation of the accessible fraction of Mg, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Sb and Pb was done by calibration using 250-μL injections of standard solutions prepared in the leaching reagent matrices. Total digestion of the sample residue was also done to verify mass balance. With the exception of Mg, V and Co, where the same total amount was released with or without microwave heating, an increased release resulted from focused microwave heating, by up to an order of magnitude. Furthermore, mass balance was verified for more elements using microwave heating, presumably because of a lower relative proportion of spectroscopic interference as a result of an increased release of analytes. Using microwave energy in general resulted in the dissolution of additional phases, as evidenced by significantly different 208Pb/ 206Pb ratios as well as the increased release of elements with milder reagents. In fact, in the case of Pb, leaching with 30% HNO 3 was no longer necessary as all the Pb was released in the first three leaching reagents. Microwave heating could therefore be used advantageously in on-line leaching for exploration geochemistry and environmental monitoring.

Evaluation of leachate emissions from crushed rock and municipal solid waste incineration bottom ash used in road construction

Three years of leachate emissions from municipal solid waste incineration bottom ash and crushed rock in a full-scale test road were evaluated. The impact of time, construction design, and climate on the emissions was studied, and the predicted release from standard leaching tests was compared with the measured release from the road. The main pollutants and their respective concentrations in leachate from the roadside slope were Al (12.8–85.3 mg l −1), Cr (2–125 μg l −1), and Cu (0.15–1.9 mg l −1) in ash leachate and Zn (1–780 μg l −1) in crushed rock leachate. From the ash, the initial Cl − release was high (∼20 g l −1). After three years, the amount of Cu and Cl − was in the same range in both leachates, while that of Al and Cr still was more than one order of magnitude higher in ash leachate. Generally, the release was faster from material in the uncovered slopes than below the pavement. Whether the road was asphalted or not, however, had minor impacts on the leachate quality. During rain events, diluted leachates with respect to, e.g., salts were observed. The leaching tests failed to simulate field leaching from the crushed rock, whereas better agreement was observed for the ash. Comparisons of constituent release from bottom ash and conventional materials solely based on such tests should be avoided.

Chemical and isotopic signatures of Na/HCO3/CO2‐rich geofluids, North Portugal

AbstractGeochemical and isotopic studies have been undertaken to assess the origin of CO2‐rich waters issuing in the northern part of Portugal. These solutions are hot (76°C) to cold (17°C) Na–HCO3 mineral waters. The δ2H and δ18O signatures of the mineral waters reflect the influence of altitude on meteoric recharge. The lack of an 18O‐shift indicates there has been no high temperature water–rock interaction at depth, corroborating the results of several chemical geothermometers (reservoir temperature of about 120°C). The low 14C activity (up to 9.9 pmC) measured in some of the cold CO2‐rich mineral waters (total dissolved inorganic carbon) is incompatible with the presence of 3H (from 1.7 to 4.1 TU) in those waters, which indicates relatively short subsurface circulation times. The δ13C values of CO2 gas and dissolved inorganic carbon range between −6‰ and −1‰ versus Vienna‐Peedee Belemnite, indicating that the total carbon in the recharge waters is being diluted by larger quantities of CO2 (14C‐free) introduced from deep‐seated (upper mantle) sources, masking the 14C‐dating values. The differences in the 87Sr/86Sr ratios of the studied thermal and mineral waters seem to be caused by water–rock interaction with different granitic rocks. Chlorine isotope signatures (−0.4‰ &lt; δ37Cl &lt; +0.4‰ versus standard mean ocean chloride) indicate that Cl in these waters could be derived from mixing of a small amount of igneous Cl from leaching of granitic rocks.