Chloride-rich Solutions Research Articles

Chloride-binding capacity of cement-GGBFS-nanosilica composites under seawater chloride-rich environment

The effects of granulated blast furnace slag (GGBFS) and nano-silica (NS) on the chloride-binding capacity of cement paste after 6-month exposure to seawater chloride-rich solutions were investigated in this paper. The pH, chloride-binding ratio (CBR), leaching behavior, and phase transformation were investigated by various experimental and analysis methods. Thermodynamic modeling was also used to study the phase assemblages for the Portland cement-GGBFS-NS composites exposed to the NaCl and MgCl2 solutions. It was found that for all cementitious composites, more chlorides were bounded in samples exposed to the salt solutions with sodium ions than that with magnesium ions. Proper additions of GGBFS and NS can enhance the chloride-binding capacity of cementitious composites. The results confirm that the addition of GGBFS can improve the chemical chloride-binding capacity because of the increased amount of chloroaluminate. The increased amount of hydrated gels in the cementitious composites with GGBFS also improved the physical chloride-binding capacity. The addition of NS increased the physical chloride-binding capacity due to the more formation of C-S-H/C-A-S-H gels, while the excessive addition of NS left less aluminum phase available for the formation of chloroaluminate, thus further decreased the chemical chloride-binding capacity. Magnesium ions in solutions increased the amount of chloride in the diffuse layer of C-S-H gels and hydrotalcite. The related results provide novel insight into the influences of GGBFS and NS on the chloride-binding capacity of cementitious composites under chloride-rich environments.

Nitrite corrosion inhibition in chloride-rich electrolytes correlated to the electrical properties of surface films on carbon steel

The electronic properties and the composition of surface films grown in pore simulating solutions are studied using various electrochemical and surface techniques and then correlated to the inhibiting efficiency of nitrite ions in chloride-rich alkaline solutions. In nitrite-free and chloride-rich solutions, the external layer of the surface film is porous, defective and rich in Fe(III). Instead, when nitrite and chloride ions are simultaneously present, the Fe(II) content increases and the film becomes thicker, ordered and more protective. In the absence of nitrite ions, chloride ions induce high donor densities that correlate to a high susceptibility to localized corrosion. In contrast, the donor density decreases noticeably when nitrites and chlorides are both present and also increases with ageing time, reaching values comparable to those calculated for uncontaminated solutions.

Hyperchloremia in Intensive Care Unit Mortality: An Underestimated Fact.

ObjectiveThe goal of the study was to determine the percentage of hyperchloremia in patients who died in medical intensive care unit (ICU) and thus emphasizing the need of avoiding chloride-rich solutions due to their deleterious effects.Study designWe conducted a retrospective study of data from 206 patients who expired in medical ICU in one year from January 2017 to December 2017 in the department of critical care medicine at Shifa International Hospital, Islamabad.Material and methodsThe study included 206 patients: 93 (43.1%) men and 123 (56.9%) women, over the age of 18 years who expired in medical ICU in one year from January 2017 to December 2017. Patients included for the study were all those who expired with any diagnosis but those who remained admitted in ICU for at least 72 hours and received intravenous fluids. The serum chloride levels of the patients at the time of admission and at 72 hours of stay in ICU were collected. The patients who were having serum chloride levels of 107 milliequivalent per deciliter (meq/dl) or more were labeled as having hyperchloremia. The data were analyzed using IBM SPSS Statistics for Windows, Version 23.0 (IBM Crop., Armonk, NY, USA). The mean and standard deviations were calculated for continuous variables while frequency and percentages were calculated for qualitative variables.ResultsAmong 206 patients who expired in our ICU, 109 (50.5%) patients had hyperchloremia at 72 hours of admission in ICU while 107 (49.5%) patients did not had hyperchloremia. Hyperchloremia was more frequent in patients with sepsis or septic shock.ConclusionHigher percentage (50.5%) of hyperchloremia at 72 hours of admission among patients (who expired in our medical ICU) indicates excessive use of chloride-rich intravenous fluids. This finding may have significant impact on mortality along with other contributing factors that lead to death of the patients. Keeping in view the findings of the study, chloride-rich solutions should be used carefully to counter the effects of hyperchloremia in patients requiring large volume fluid resuscitation in ICU. Fluids with lower content of chloride such as lactated ringer may be equally good in large volume fluid resuscitation with advantage of avoiding hyperchloremia.

Influence of slag composition on the stability of steel in alkali-activated cementitious materials

Among the minor elements found in metallurgical slags, sulfur and manganese can potentially influence the corrosion process of steel embedded in alkali-activated slag cements, as both are redox-sensitive. Particularly, it is possible that these could significantly influence the corrosion process of the steel. Two types of alkali-activated slag mortars were prepared in this study: 100% blast furnace slag and a modified slag blend (90% blast furnace slag + 10% silicomanganese slag), both activated with sodium silicate. These mortars were designed with the aim of determining the influence of varying the redox potential on the stability of steel passivation under exposure to alkaline and alkaline chloride-rich solutions. Both types of mortars presented highly negative corrosion potentials and high current density values in the presence of chloride. The steel bars extracted from mortar samples after exposure do not show evident pits or corrosion product layers, indicating that the presence of sulfides reduces the redox potential of the pore solution of slag mortars, but enables the steel to remain in an apparently passive state. The presence of a high amount of MnO in the slag does not significantly affect the corrosion process of steel under the conditions tested. Mass transport through the mortar to the metal is impeded with increasing exposure time; this is associated with refinement of the pore network as the slag continued to react while the samples were immersed.

Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements.

Characterization of injury in isolated rat proximal tubules during cold incubation and rewarming.

Organ shortage leads to an increased utilization of marginal organs which are particularly sensitive to storage-associated damage. Cold incubation and rewarming-induced injury is iron-dependent in many cell types. In addition, a chloride-dependent component of injury has been described. This work examines the injury induced by cold incubation and rewarming in isolated rat renal proximal tubules. The tissue storage solution TiProtec® and a chloride-poor modification, each with and without iron chelators, were used for cold incubation. Incubation was performed 4°C for up to 168 h, followed by rewarming in an extracellular buffer (3 h at 37°C). After 48, 120 and 168 h of cold incubation LDH release was lower in solutions containing iron chelators. After rewarming, injury increased especially after cold incubation in chelator-free solutions. Without addition of iron chelators LDH release showed a tendency to be higher in chloride-poor solutions. Following rewarming after 48 h of cold incubation lipid peroxidation was significantly decreased and metabolic activity was tendentially better in tubules incubated with iron chelators. Morphological alterations included mitochondrial swelling and fragmentation being partially reversible during rewarming. ATP content was better preserved in chloride-rich solutions. During rewarming, there was a further decline of ATP content in the so far best conditions and minor alterations under the other conditions, while oxygen consumption was not significantly different compared to non-stored control tubules. Results show an iron-dependent component of preservation injury during cold incubation and rewarming in rat proximal renal tubules and reveal a benefit of chloride for the maintenance of tubular energy state during cold incubation.

Hyperchloremia is associated with 30-day mortality in major trauma patients: a retrospective observational study.

BackgroundChloride is important for maintaining acid-base balance, muscular activity, osmosis and immunomodulation. In patients with major trauma, chloride levels increase after fluid therapy; this is associated with poor clinical outcomes. The purpose of this study was to determine whether hyperchloremia was associated with increased mortality in patients who had sustained major trauma.MethodsThis study enrolled 266 major trauma patients by retrospective chart review, from January 2011 to December 2015. Patients were older than 16 years; were admitted to an intensive care unit; survived more than 48 h; and had sustained major trauma, defined as an injury severity score ≥ 16. Hyperchloremia was defined as a chloride level > 110mEq/L. Delta chloride (Δchloride) was defined as the difference between the serum chloride level measured 48-h post-admission and the initial level. Clinical and laboratory variables were compared between survivors (n = 235) and non-survivors (n = 31). A multivariate logistic regression analysis was performed to assess the association between hyperchloremia 48-h post-admission (hyperchloremia-48) and 30-day mortality.ResultsThe overall 30-day mortality was 11.7 % (n = 31). Hyperchloremia-48 occurred in 65 patients (24.4 %) and the incidence was significantly different between survivors and non-survivors (19.6 vs. 61.3 %, respectively, p < 0.001). Multivariate logistic analysis identified hyperchloremia-48 and Δchloride as independent predictive factors for 30-day mortality in major trauma patients.DiscussionInfusion of chloride-rich solutions, such as normal saline, is itself associated with hyperchloremia, which has been associated with poor patient outcomes. Patients receiving normal saline were more likely to suffer major postoperative complications, acute kidney injury, and infections. Moreover, large changes in serum chloride levels correlated with greater in-hospital mortality. ConclusionHyperchloremia 48-h post-admission and Δchloride was associated with 30-day mortality in major trauma patients. These indices may be useful prognostic markers.

Impact of chloride and strong ion difference on ICU and hospital mortality in a mixed intensive care population.

Background Abnormal chloride levels are commonly observed in critically ill patients, but their clinical relevance remains a matter of debate. We examined the association between abnormal chloremia and ICU and hospital mortality. To further refine findings and integrate them into the ongoing discussion on the detrimental effects of chloride-rich solutions, the impact of strong ion difference (SID) on the same end points was assessed.Methods Retrospective cohort study in an academic tertiary intensive care unit on 8830 adult patients who stayed at least 24 h in the ICU was carried out. Patients admitted after elective cardiac surgery were treated as a separate subgroup (n = 2350). Analyses were performed using multivariable logistic regression. All statistical models were extensively adjusted for confounders, including comorbidity, admission diagnosis, other electrolytes and acid–base parameters.ResultsSevere hyperchloremia (>110 mmol/L), but not low (SID) was significantly associated with increased mortality in the ICU (odds ratio vs. normochloremia 1.81; 95 % CI 1.32–2.50; p < 0.001) and the hospital (odds ratio 1.49; 95 % CI 1.14–1.96; p = 0.003). Hyperchloremia and low (SID) were encountered in the majority of patients admitted after cardiac surgery (in 86.9 and 47.2 %, respectively), but were not negatively associated with mortality.ConclusionsIn the ICU, hyperchloremia at admission was associated with negative outcome. On the other hand, decreased strong ion difference did not have an impact on mortality, precluding a simple extrapolation of these findings to the ongoing discussion on the detrimental effects of chloride-rich solutions. This notion is fueled by the finding that hyperchloremia after cardiac surgery, frequently encountered and probably fluid-induced, did not seem to be deleterious.Electronic supplementary materialThe online version of this article (doi:10.1186/s13613-016-0193-x) contains supplementary material, which is available to authorized users.

Update on perioperative acute kidney injury.

In this review, we discuss the latest updates on perioperative acute kidney injury (AKI) and the specific considerations that are relevant to different surgeries and patient populations. AKI diagnosis is constantly evolving. New biomarkers detect AKI early and shed a light on the possible cause of AKI. Hypotension, even for a short duration, is associated with perioperative AKI. The debate on the deleterious effects of chloride-rich solutions is still far from conclusion. Remote ischemic preconditioning is showing promising results in the possible prevention of perioperative AKI. No definite data show a beneficiary effect of statins, fenoldepam, or sodium bicarbonate in preventing AKI. Perioperative AKI is prevalent and associated with significant morbidity and mortality. Considering the lack of effective preventive or therapeutic interventions, this review focuses on perioperative AKI: measures for early diagnosis, defining risks and possible mechanisms, and summarizing current knowledge for intraoperative fluid and hemodynamic management to reduce risk of AKI.

Are all fluids bad for the kidney?

To describe the harmful effects of intravenous fluids on kidney structure and function and summarize recent comparisons between different fluids and their effect on kidney outcome. Administration of intravenous fluids may contribute to the development and sustention of acute kidney injury. In excess, fluids cause kidney interstitial edema and venous congestion, which prevents renal blood flow and glomerular filtration rate. In contrast to balanced crystalloids, chloride-rich solutions impair renal blood flow via autoregulatory mechanisms. Synthetic colloids, such as hydroxyethyl starches, gelatins, and dextrans are potentially nephrotoxic because they can cause osmotic nephrosis, which, in susceptible patients, might precede permanent kidney damage. Albumin solutions appear well tolerated to use in septic patients, although their renal efficacy over balanced crystalloids is not established. In contrast, administration of albumin solutions to patients with decompensated liver failure effectively prevents and ameliorates hepatorenal syndrome. Being nephrotoxic, synthetic colloids should be avoided in patients with reduced renal reserve, such as in critically ill patients and in patients with preexisting renal dysfunction. Suggested adverse effects with chloride-rich solutions need confirmation from ongoing trials. Albumin solutions are well tolerated in patients with sepsis and/or liver failure and improve outcomes in the latter.

Palladium complexation in chloride- and bisulfide-rich fluids: Insights from ab initio molecular dynamics simulations and X-ray absorption spectroscopy

Palladium (Pd) is the most mobile element of the platinum group elements (PGE) in hydrothermal fluids. The characterization of the nature and stability of Pd(II) complexes in geofluids is essential in understanding the formation of hydrothermal PGE deposits and the remobilization of PGE during hydrothermal and metamorphic overprints of magmatic deposits. However, the aqueous speciation of this metal in a range of geologically relevant conditions remains controversial. A number of experimental studies of Pd solubility and speciation in hydrothermal fluids suggest that chloride and bisulfide are the major ligands responsible for carrying Pd as Pd(II)–Cl and Pd(II)–HS complexes, but different experimental studies predicted different predominant chloride and bisulfide complexes and their relative strengths. Hence, we conducted ab initio molecular dynamics (MD) simulations to predict the speciation of Pd–Cl and Pd–HS complexes at 300°C. The simulations predicted that all complexes share fourfold square-planar structures, which is consistent with X-ray absorption spectroscopy measurements of Pd(II) in chloride-rich solutions. The stability constants for the stepwise formation of Pd(II)–Cl and Pd(II)–HS complexes were determined using thermodynamic integration. The predicted formation constants of Pd(II)–Cl complexes show excellent agreement (within ∼1 order of magnitude for PdCl+, within 0.3 for PdCl2(aq) and PdCl3−, within 0.1 for PdCl42−) with the recent experimental study of Tagirov et al. (2013). However, our results suggest that the Pd(HS)42− complex predominates in HS−-rich hydrothermal fluids, whereas interpretation of previous experimental studies neglected this species. Modeling of Pd solubility in chloride- and sulfur-rich hydrothermal fluids demonstrated that Pd is mainly carried as the Pd(HS)42− hydrosulfide complex at neutral-alkaline and reduced (pyrite/pyrrhotite stable) conditions, and as the PdCl42− chloride complex at acidic and oxidized conditions. At 300°C, significant Pd mobility at ppb level as Pd bisulfide complexes is predicted under fluid-buffered conditions (e.g., pH ∼7 to 8, near HS−/H2S(aq) pH buffer), but only limited Pd solubility is predicted under rock-buffered conditions (e.g., pH ∼4 to 5, quartz–feldspar–muscovite buffer).

HIGHER BALANCED SOLUTION USE IS ASSOCIATED WITH LESS SEVERE KIDNEY INJURY AND MORTALITY: A MIMIC 2 ANALYSIS

Balanced solutions may be associated with lower morbidity in critical illness in comparison with chloride-rich solutions, including acute kidney injury (AKI). Lactated ringer (LR) is one of most widely used balanced solutions. Nevertheless, it is unclear if fluid mix during the first days of ICU admission influences the development of AKI after controlling for other relevant confounders such as fluid balance, illness severity and comorbidities.

Physicochemical Evaluation of Acid–Base Disorders After Liver Transplantation and the Contribution From Administered Fluids

ObjectivesTo analyze the mechanism of acid–base disorders in liver transplant recipients and to examine the relationship between these disorders and the fluids administered during surgery. MethodsThis prospective study in a university-affiliated hospital intensive care unit (ICU) included 52 patients admitted to the ICU from December 2009 to January 2011. We examined the contributions of inorganic ion differences, lactate, unmeasured anions, phosphate, and albumin to metabolic acidosis. In addition to laboratory variables, we collected demographic and clinical data. ResultsMetabolic acidosis (standard base excess ≤ −2.0 mmol/L) was identified in 37 (71.2%) patients during the immediate postoperative period. The inorganic ion difference was the main determinant of acidosis, accounting for −6.17 mEq/L of acidifying effect. The acidemia was attenuated mainly by the alkalinizing effect of albumin reduction, which contributed +6.03 mEq/L. There was an inverse proportional relationship between the quantity of saline solution used during surgery and the inorganic ion difference during the immediate postoperative period. ConclusionsHyperchloremia is the primary contributor to metabolic acidosis in liver transplant recipients. Possibly the use of chloride-rich solutions increases the incidence of this disorder.

Characterization of U(VI)-phases in corroded cement products by micro(μ)-spectroscopic methods

Cementation is an industrial scale conditioning method applied to fix and solidify liquid low and intermediate level radioactive wastes (LLW/ILW) prior to underground disposal in geological formations.To assist prognosis of the long-term safety of cemented waste, alteration of uranium doped cement productswas studied in chloride-rich solutions relevant for final LLW/ILW disposal in rock salt. After long-time exposure of the full-scale LLW/ILW simulates to concentrated NaCl and MgCl2 brines, solid samples were retrieved for chemical and mineralogical analysis with an emphasis on uranium speciation in the corroded cement matrix.Bulk and recent spatially resolved micro(μ) U L3-XAFS measurements point to the occurrence of a diuranate type U(VI) phase forming throughout the corroded cement monoliths. U-enriched hot spots with dimensions up to several tens of μm turn out to be generally X-ray amorphous.

Balanced versus chloride-rich solutions for fluid resuscitation in brain-injured patients: a randomised double-blind pilot study

IntroductionWe sought to investigate whether the use of balanced solutions reduces the incidence of hyperchloraemic acidosis without increasing the risk for intracranial hypertension in patients with severe brain injury.MethodsWe conducted a single-centre, two-arm, randomised, double-blind, pilot controlled trial in Nantes, France. Patients with severe traumatic brain injury (Glasgow Coma Scale score ≤8) or subarachnoid haemorrhage (World Federation of Neurosurgical Society grade III or higher) who were mechanically ventilated were randomised within the first 12 hours after brain injury to receive either isotonic balanced solutions (crystalloid and hydroxyethyl starch; balanced group) or isotonic sodium chloride solutions (crystalloid and hydroxyethyl starch; saline group) for 48 hours. The primary endpoint was the occurrence of hyperchloraemic metabolic acidosis within 48 hours.ResultsForty-two patients were included, of whom one patient in each group was excluded (one consent withdrawn and one use of forbidden therapy). Nineteen patients (95%) in the saline group and thirteen (65%) in the balanced group presented with hyperchloraemic acidosis within the first 48 hours (hazard ratio = 0.28, 95% confidence interval [CI] = 0.11 to 0.70; P = 0.006). In the saline group, pH (P = .004) and strong ion deficit (P = 0.047) were lower and chloraemia was higher (P = 0.002) than in the balanced group. Intracranial pressure was not different between the study groups (mean difference 4 mmHg [-1;8]; P = 0.088). Seven patients (35%) in the saline group and eight (40%) in the balanced group developed intracranial hypertension (P = 0.744). Three patients (14%) in the saline group and five (25%) in the balanced group died (P = 0.387).ConclusionsThis study provides evidence that balanced solutions reduce the incidence of hyperchloraemic acidosis in brain-injured patients compared to saline solutions. Even if the study was not powered sufficiently for this endpoint, intracranial pressure did not appear different between groups.Trial registrationEudraCT 2008-004153-15 and NCT00847977The work in this trial was performed at Nantes University Hospital in Nantes, France.

Long-term cement corrosion in chloride-rich solutions relevant to radioactive waste disposal in rock salt – Leaching experiments and thermodynamic simulations

Low- and intermediate-level radioactive wastes are frequently solidified in a cement matrix. In a potential repository for nuclear wastes, the cementitious matrix is altered upon contact with solution and the resulting secondary phases may provide for significant retention of the radionuclides incorporated in the wastes. In order to assess the secondary phases formed upon corrosion in chloride-rich solutions, which are relevant for nuclear waste disposal in rock salt, leaching experiments were performed. Conventional laboratory batch experiments using powdered hardened cement paste in MgCl2-rich solutions were left to equilibrate for up to three years and full-scale cemented waste products were exposed to NaCl-rich and MgCl2-rich solutions for more than twenty years, respectively. Solid phase analyses revealed that corrosion of hardened cement in MgCl2-rich solutions advanced faster than in NaCl-rich solutions due to the extensive exchange of Mg from solution against Ca from the cementitious solid. Thermodynamic equilibrium simulations compared well to results at the final stages of the respective experiments indicating that close to equilibrium conditions were reached. At high cement product to brine ratios (>0.65gmL−1), the solution composition in the laboratory-scale experiments was close to that of the full-scale experiments (cement to brine ratio of 2.5gmL−1) in the MgCl2 systems. The present study demonstrates the applicability of thermodynamic methods used in this approach to adequately describe full-scale long-term experiments with cemented waste simulates.

Lean duplex stainless steels—The role of molybdenum in pitting corrosion of concrete reinforcement studied with industrial and laboratory castings

The influence of Mo addition on pitting corrosion resistance of lean duplex stainless steels is not clearly understood in alkaline chloride conditions even if this element is widely recognized to increase corrosion resistance in acidic and neutral environments. This work aims to study the effect of Mo on pitting corrosion of lean duplex stainless steels in synthetic concrete pore solutions simulating degraded concrete. Results are discussed with respect to the influence of Mo on pitting potential for two industrial alloys in chloride rich and carbonated solution simulating concrete pore environments. To establish the real effect of Mo addition on lean duplex corrosion and passivation properties, two specific laboratory lean duplex alloys, for which the only difference is strictly the Mo content, are also studied. Mo presented a strong positive influence on the pitting corrosion resistance of industrial and laboratory lean duplex stainless steels in all studied chloride-rich solutions, but its effect is as less pronounced as the pH increases. In presence of Mo, pitting initiates and propagates preferentially in the austenitic phase at high temperature.

Improvement of the Cold Storage of Isolated Human Hepatocytes

Increasing amounts of human hepatocytes are needed for clinical applications and different fields of research, such as cell transplantation, bioartificial liver support, and pharmacological testing. This demand calls for adequate storage options for isolated human liver cells. As cryopreservation results in severe cryoinjury, short-term storage is currently performed at 2-8°C in preservation solutions developed for the storage of solid organs. However, besides slowing down cell metabolism, cold also induces cell injury, which is, in many cell types, iron dependent and not counteracted by current storage solutions. In this study, we aimed to characterize storage injury to human hepatocytes and develop a customized solution for cold storage of these cells. Human hepatocytes were isolated from material obtained from partial liver resections, seeded in monolayer cultures, and, after a preculture period, stored in the cold in classical and new solutions followed by rewarming in cell culture medium. Human hepatocytes displayed cold-induced injury, resulting in >80% cell death (LDH release) after 1 week of cold storage in University of Wisconsin solution or cell culture medium and 3 h of rewarming. Cold-induced injury could be significantly reduced by the addition of the iron chelators deferoxamine and LK 614. Experiments with modified solutions based on the new organ preservation solution Custodiol-N showed that ion-rich variants were better than ion-poor variants, chloride-rich solutions better than chloride-poor solutions, potassium as main cation superior to sodium, and pH 7.0 superior to pH 7.4. LDH release after 2 weeks of cold storage in the thus optimized solution was below 20%, greatly improving cold storage of human hepatocytes. The results were confirmed by the assessment of hepatocellular mitochondrial membrane potential and functional parameters (resazurin reduction, glucagon-stimulated glucose liberation) and thus suggest the use of a customized hepatocyte storage solution for the cold storage of these cells.

Wettability alteration of kaolinite exposed to crude oil in salt solutions

Adsorption and deposition of polar components of crude oils onto kaolinite in the presence of aqueous solutions of sodium and calcium chlorides is probed by spectroscopy, microscopy and drop contact angle. The fine kaolinite particles are thinly coated onto glass to remain immobile during the aging in salt solution and oil, and subsequent solvent rinsing. These thin coats facilitate quantification of the extent of deposition versus salt composition, while also allowing high-resolution microscopy of its spatial distribution. The asphaltene-based deposits take the form of nanoparticle aggregates decorating kaolinite faces and edges. At low salinity and low-neutral pH, water surrounding kaolinite is expelled by oil deposition and pore penetration to strongly alter wettability of the aggregate from hydrophilic to oleophilic, and trends are in qualitative agreement with expectations from DLVO theory. Higher ionic strength suppresses oil deposition, either by limiting it to kaolinite edges in the case of sodium chloride-rich solutions or protecting both faces and edges at high calcium chloride contents. Only the latter suffices for the kaolinite aggregate to substantially retain its hydrophilicity.

Geochemical/isotopic evolution of Pb–Zn deposits in the Central and Eastern Taurides, Turkey

The Central and Eastern Taurides contain numerous carbonate-hosted Pb–Zn deposits, mainly in Devonian and Permian dolomitized reefal–stramatolitic limestones, and in massive Jurassic limestones. We present and compare new fluid inclusion and isotopic data from these ore deposits, and propose for the first time a Mississippi Valley-type (MVT) mode of origin for them. Fluid inclusion studies reveal that the ore fluids were highly saline (13–26% NaCl equiv.), chloride-rich (CaCl2) brines, and have average homogenization temperatures of 112°C, 174.5°C, and 211°C for the Celal Dağ, Delikkaya, and Ayraklı deposits, respectively. Furthermore, the δ34S values of carbonate-hosted Pb–Zn deposits in the Central and Eastern Taurides vary between –5.4‰ and +13.70‰. This indicates a possible source of sulphur from both organic compounds and crustal materials. In contrast, stable sulphur isotope data (average δ34S –0.15‰) for the Çadırkaya deposit, which is related to a late Eocene–Oligocene (?) granodioritic intrusion, indicates a magmatic source. The lead isotope ratios of galena for all investigated deposits are heterogeneous. In particular, with the exception of the Suçatı district, all deposits in the Eastern (Delikkaya, Ayraklı, Denizovası, Çadırkaya) and Central (Katranbaşı, Küçüksu) Taurides have high radiogenic lead isotope values (206Pb/204Pb between 19.058 and 18.622; 207Pb/204Pb between 16.058 and 15.568; and 208Pb/204Pb between 39.869 and 38.748), typical of the upper continental crust and orogenic belts. Fluid inclusion, stable sulphur, and radiogenic lead isotope studies indicate that carbonate-hosted metal deposits in the Eastern (except for the Çadırkaya deposit) and the Central Taurides are similar to MVT Pb–Zn deposits described elsewhere. The primary MVT deposits are associated with the Late Cretaceous–Palaeocene closure of the Tethyan Ocean, and formed during the transition from an extensional to a compressional regime. Palaeogene nappes that typically limit the exposure of ore bodies indicate a pre-Palaeocene age of ore formation. Host rock lithology, ore mineralogy, fluid inclusion, and sulphur + lead isotope data indicate that the metals were most probably leached from a crustal source such as clastic rocks or a crystalline massif, and transported by chloride-rich hydrothermal solutions to the site of deposition. Localization of the ore deposits on autochthonous basement highs indicates long-term basinal fluid migration, characteristic of MVT depositional processes. The primary MVT ores were oxidized in the Miocene, resulting in deposition of Zn-carbonate and Pb-sulphate–carbonate during karstification. The ores underwent multiple cycles of oxidation and, in places, were re-deposited to form clastic deposits. Modified deposits resemble the ‘wall-rock replacement’ and the ‘residual and karst fill’ of non-sulphide zinc deposits and are predominantly composed of smithsonite.