Vendian Hydrogeochemistry of the Siberian Platform

2021 ◽  
Vol 62 (08) ◽  
pp. 887-903
Author(s):  
D.A. Novikov ◽  
A.V. Chernykh ◽  
L.N. Konstantinova ◽  
F.F. Dultsev ◽  
I.I. Yurchik
Keyword(s):  
Siberian Platform ◽  
Hydrothermal Activity ◽  
Late Permian ◽  
Temperature Changes ◽  
Ph Values ◽  
Reducing Conditions ◽  
Group I ◽  
Bottom To Top ◽  
Enclosing Rocks ◽  
Total Salinity

Abstract —The Vendian deposits of the Siberian Platform are represented by four regional horizons (from bottom to top): Nepa, Vilyuchan, Tira, and Danilovka. The TDS of brines in the Nepa and Vilyuchan horizons varies from 170.3 to 470.1 g/L, and the TDS in the overlying Tira and Danilovka horizons, from 84.6 to 583.1 g/L. Brines of Cl Na, Cl Na–Ca, Cl Ca–Na, Cl Ca, and Cl Ca–Mg types have been identified. The pH values of the brines vary from 3.0 to 7.0; acidic and weakly acidic brines (pH = 3.0–5.5) prevail. The redox potential Eh varies from –440 mV (highly reducing conditions) to +130 mV (oxidizing conditions), averaging –176 mV. Areal regional hydrogeochemical zoning is controlled by the outer (on the periphery of the Siberian Platform, where infiltration of meteoric waters took place) and inner feeding areas. The outer feeding areas bear infiltrogenic brines of different ages (group I), mostly of Cl Na composition. They are characterized by TDS ≤ 280 g/L, rNa/rCl ≤ 1.55, Cl/Br ≤ 2512, and average Ca/Cl = 0.3. The average values of the integrated brine metamorphization index S (according to S.L. Shvartsev) range from 50 to 200. In the intraplatform feeding areas, there are several phases of brines that underwent gravitational sinking into the Vendian horizons in the periods when Cambrian salt-bearing basins existed on the platform. These brines were metamorphosed during filtration along the fracture and fault zones. The intrusion of traps in the late Permian–early Triassic was accompanied by hydrothermal activity. The waters of the enclosing Cambrian dolomite horizons were heated to 800–1000 °C; their subsequent interaction with carbonate rocks and evaporites (in particular, chlorides) resulted in extrastrong saturated brines. These brines were also subjected to gravitational sinking into the Vendian reservoirs, which was the main cause of the inverse vertical hydrogeochemical zoning in the hydrogeologic subsalt formation. The brine metamorphism processes and temperature changes in the rock horizons during the intrusion of traps and their subsequent cooling led to a significant alteration of the enclosing rocks under interaction with brines and to salinization of the reservoirs, an increase in the total salinity of the brines, and catagenetic changes in their composition. The brines closest to the maximum saturation with halite were found in reservoir zones with the highest salinization and near faults and boundaries of intrusive bodies. During the pre-Vilyuchan, pre-Nepa, pre-Tira, and pre-Danilovka sedimentation breaks, infiltrogenic waters penetrated into the Vendian sediments. Geochemically, the sedimentogenic, infiltrogenic, and metamorphic strong brines (group II) have a predominantly Cl Ca or Cl Ca–Mg composition with TDS > 350 g/L. They are characterized by low rNa/rCl ratios (on average, 0.3), Cl/Br ≤ 100, high Ca/Cl values (on average, 0.4), and S > 250.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

scholarly journals High-resolution stratigraphy of the Changhsingian (Late Permian) successions of NW Iran and the Transcaucasus based on lithological features, conodonts and ammonoids

Fossil Record ◽  
2014 ◽  
Vol 17 (1) ◽  
pp. 41-57 ◽  
Author(s):  
A. Ghaderi ◽  
L. Leda ◽  
M. Schobben ◽  
D. Korn ◽  
A. R. Ashouri
Keyword(s):  
Late Permian ◽  
Triassic Boundary ◽  
Nw Iran ◽  
The Earth ◽  
Extinction Event ◽  
History Of ◽  
Mass Extinction Event ◽  
Bottom To Top ◽  
Permian Triassic Boundary ◽  
North Western

Abstract. The Permian–Triassic boundary sections in north-western Iran belong to the most complete successions, in which the largest mass extinction event in the history of the Earth can be studied. We investigated the Changhsingian stage in six sections in the area of Julfa (Aras Valley) for their lithology, conodonts and ammonoids. Revision of the biostratigraphy led to the separation of 10 conodont zones (from bottom to top Clarkina orientalis–C. subcarinata interval zone, C. subcarinata, C. changxingensis, C. bachmanni, C. nodosa, C. yini, C. abadehensis, C. hauschkei, Hindeodus praeparvus–H. changxingensis and Merrilina ultima–Stepanovites ?mostleri zones) and 8 ammonoid zones (from bottom to top Iranites transcaucasius–Phisonites triangulus, Dzhulfites nodosus, Shevyrevites shevyrevi, Paratirolites trapezoidalis, P. waageni, Stoyanowites dieneri, Abichites stoyanowi and Arasella minuta zones). The new ammonoid genera Stoyanowites and Arasella are described.

scholarly journals Trace Element and Isotope Systematics in Vent Fluids and Sulphides From Maka Volcano, North Eastern Lau Spreading Centre: Insights Into Three-Component Fluid Mixing

2021 ◽  
Vol 9 ◽  
Author(s):  
Lukas Klose ◽  
Manuel Keith ◽  
Daniel Hafermaas ◽  
Charlotte Kleint ◽  
Wolfgang Bach ◽  
...  
Keyword(s):  
Trace Element ◽  
Hydrothermal Activity ◽  
Fluid Composition ◽  
Black Smoker ◽  
Ph Values ◽  
The North ◽  
North Eastern ◽  
Trace Element Signature ◽  
Back Arc ◽  
Ree Patterns

Back-arc spreading centres and related volcanic structures are known for their intense hydrothermal activity. The axial volcanic edifice of Maka at the North Eastern Lau Spreading Centre is such an example, where fluids of distinct composition are emitted at the Maka hydrothermal field (HF) and at Maka South in 1,525–1,543 m water depth. At Maka HF black smoker-type fluids are actively discharged at temperatures of 329°C and are characterized by low pH values (2.79–3.03) and a depletion in Mg (5.5 mmol/kg) and SO4 (0.5 mmol/L) relative to seawater. High metal (e.g., Fe up to ∼6 mmol/kg) and rare Earth element (REE) contents in the fluids, are indicative for a rock-buffered hydrothermal system at low water/rock ratios (2–3). At Maka South, venting of white smoke with temperatures up to 301°C occurs at chimneys and flanges. Measured pH values range from 4.53 to 5.42 and Mg (31.0 mmol/kg), SO4 (8.2 mmol/L), Cl (309 mmol/kg), Br (0.50 mmol/kg) and Na (230 mmol/kg) are depleted compared to seawater, whereas metals like Li and Mn are typically enriched together with H2S. We propose a three-component mixing model with respect to the fluid composition at Maka South including seawater, a boiling-induced low-Cl vapour and a black smoker-type fluid similar to that of Maka HF, which is also preserved by the trace element signature of hydrothermal pyrite. At Maka South, high As/Co (>10–100) and Sb/Pb (>0.1) in pyrite are suggested to be related to a boiling-induced element fractionation between vapour (As, Sb) and liquid (Co, Pb). By contrast, lower As/Co (<100) and a tendency to higher Co/Ni values in pyrite from Maka HF likely reflect the black smoker-type fluid. The Se/Ge ratio in pyrite provides evidence for fluid-seawater mixing, where lower values (<10) are the result of a seawater contribution at the seafloor or during fluid upflow. Sulphur and Pb isotopes in hydrothermal sulphides indicate a common metal (loid) source at the two vent sites by host rock leaching in the reaction zone, as also reflected by the REE patterns in the vent fluids.

scholarly journals Pengaruh Suhu Terhadap Penyerapan Air Dan Kelarutan Resin Komposit

2017 ◽  
Vol 6 (2) ◽  
pp. 59
Author(s):  
Kholidina Imanda Harahap ◽  
Rusfian Rusfian ◽  
Affan Ali Al-Harits
Keyword(s):  
Water Sorption ◽  
Composite Resin ◽  
Testing Procedure ◽  
Effect Of Temperature ◽  
Temperature Changes ◽  
Group Iii ◽  
Group I ◽  
Group Ii ◽  
Dental Restorative ◽  
One Way Anova

The existence of composite resin as dental restorative materials in the mouth will always be exposed to temperature changes from food or drink. The purpose of this study was to evaluate the effect of temperature on water absorption and solubility of the composite resin. Thirty samples made from nanofiller composite resin with a diameter of 15 mm and a thickness of 1 mm. The samples were divided into three test groups (n=10) that is immersed at 50 (I), 37 (II) and 5 °C (III). The testing procedure of water sorption and solubility of the composite resin made according to the ISO 4049: 2000 specifications. Data will be analyzed by one-way ANOVA and Least Significance Data test (p=0,05). The results showed there is significant differences of the water sorption (p=0,045)  and solubility (p=0,018). The highest water sorption is group I (0,0057±0,007µg/mm3) than group II (0,0028±0,0013 µg/mm) and group III (0,0005±0,0006 µg/mm). While the heighest solubility values   are in group I (0,003 ± 0,0027 µg/ mm), than group II (0,002 ± 0,0013 µg/mm) and group III (0,001 ± 0,00 µg/mm). It can be concluded that temperature could increase water sorption and solubility of composite resin.

First Evidence of Active Sulphate Reduction in a Lignite Mine Dump Site at Low pH Values – the Plessa Site

2007 ◽  
Vol 20-21 ◽  
pp. 201-204 ◽  
Author(s):  
Annett Storch ◽  
Katja Tröger ◽  
Nils Hoth ◽  
Kay Knöller
Keyword(s):  
Sulphate Reduction ◽  
Mining District ◽  
Dump Site ◽  
Ph Values ◽  
Reducing Conditions ◽  
Lignite Mine ◽  
Bacterial Sulphate Reduction ◽  
Show Evidence ◽  
Main Carbon Source ◽  
Reducing Bacteria

It has been postulated that bacterial sulphate reduction is related to pH-values above 5.5 (e.g. [1]). First investigations for the 80-year old dump Plessa in the Lower Lusatian mining district (East Germany) show evidence for active sulphate reduction. Mining dump waters from the Plessa site have pH values of 2.4 to 4.9 and pe values between 2 and 6. Measured sulphide concentrations range from 50 to 1200 -g/L. The influence of bacterial sulphate reduction on the development of sulphate concentrations in the dump waters is supported by increasing δ34S and δ18O values with decreasing sulphate concentrations. These findings document that sulphate reduction under natural conditions is not exclusively related to neutral pH values and strongly reducing conditions. Furthermore the tertiary organic matter contained in the dump sediments is the main carbon source for sulphate reducing bacteria.

scholarly journals Clinical and laboratory evaluation of premature goat kids with and without antenatal corticotherapy

2022 ◽  
Vol 52 (7) ◽  
Author(s):  
Gabriel Isola Braga ◽  
Jefferson Filgueira Alcindo ◽  
Luis Gustavo Narciso ◽  
Fernanda Bovino ◽  
Thomas Alexander Trein ◽  
...  
Keyword(s):  
Laboratory Evaluation ◽  
Adaptation Period ◽  
Cesarean Sections ◽  
Radiological Findings ◽  
Group Iii ◽  
Ph Values ◽  
Dexamethasone Group ◽  
Group I ◽  
Group Ii ◽  
Gas Measurements

ABSTRACT: This article evaluated the vital parameters, blood gas measurements, cortisol values and radiological findings of goat kids born at term and prematurely during the first 48 hours of life. For this purpose, 24 kids from 24 goats were used and assigned to groups as follows: Group I, eight kids born through cesarean sections performed at 149 days of gestation; Group II, eight kids born through cesarean sections performed at 143 days of gestation; Group III, eight kids born through cesarean sections performed at 143 days of gestation, whose mothers received 20 mg of dexamethasone. Group I had lower heart rate values than the other groups at 60 minutes after birth. In terms of temperature, there was no difference between the groups. The pH values were reduced shortly after birth, rising at 24 and 48 hours in all animals studied. In terms of the cortisol levels, the values increased significantly at birth (M0), with the highest values obtained in animals in group II. These values decreased at 48 hours after birth in the evaluated goats. The animals belonging to group I showed better radiographic aspects, and throughout the 48 hours of evaluation, all newborns exhibited adequate respiratory adaptation. It can be concluded that antenatal dexamethasone administered at 143 days of gestation did not influence neonatal viability, metabolic or radiographic parameters. The metabolic changes found are consistent with the extrauterine adaptation period that animals in this stage of life.

scholarly journals Effect of Acidic Environment on the Push-out Bond Strength of Biodentine™

2012 ◽  
Vol 3 (4) ◽  
pp. 313-315 ◽  
Author(s):  
Gaurav Poplai ◽  
Sameer Jadhav
Keyword(s):  
Bond Strength ◽  
Testing Machine ◽  
Test Group ◽  
Low Ph ◽  
P Value ◽  
Acidic Environment ◽  
Solution Ph ◽  
Ph Values ◽  
Group I ◽  
Push Out

ABSTRACT Introduction An apical sealing material may be exposed to an inflamed environment with low pH levels. The change in physical and chemical properties of mineral trioxide aggregate has been well-documented in the presence of low pH. However, on literature search there is no documentation of the effect of low pH on Biodentine™. Aim To compare the effects of various levels of acidic pH on the push-out bond strength of Biodentine™. Materials and methods Forty root dentin slices from single rooted human teeth were sectioned horizontally. The canal lumens were instrumented to obtain a standardized diameter of 1.3 mm and filled with Biodentine™. The specimens were then randomly divided into four groups (n = 10) and wrapped in pieces of gauze soaked in phosphate buffer saline solution (pH = 7.4) and butyric acid buffered at pH values of 4.4, 5.4 and 6.4 respectively. They were incubated at 37°C for 4 days. Push-out test were then carried out using universal testing machine. The data was analyzed using one-way analysis of variance (ANOVA) technique with Tukey's correction for multiple group comparisons. Results Data was subjected to one-way ANOVA using Tukey's post hoc test. Group I (control, pH = 7.4) showed greatest bond strength of 19.5 ± 0.9 MPa. The least push-out bond strength of 11.7 ± 0.5 MPa was observed in Group IV where the specimens were soaked at pH 4.4. A p-value less than 0.05 were considered to be statistically significant. Conclusion The force needed to displace Biodentine was significantly lower in samples stored at lower pH values. How to cite this article Poplai G, Jadhav S, Hegde V. Effect of Acidic Environment on the Push-out Bond Strength of Biodentine™. World J Dent 2012;3(4):313-315.

Features of ore formation of gold deposits of Glukharinsky District (Prikolyma Terrain)

2019 ◽  
Vol 484 (1) ◽  
pp. 66-70
Author(s):  
A. A. Biryukov ◽  
A. V. Volkov ◽  
K. Yu. Murashov ◽  
A. A. Sidorov
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Gold Deposits ◽  
Ore Formation ◽  
Reducing Conditions ◽  
Isotope Studies ◽  
Enclosing Rocks ◽  
Ore Deposition

This study discusses new data on the isotopy of δ34S, δ18O, microelements, and rare earth elements (REE) in the Au deposits of the Glukarinsky ore cluster. The identified geochemical features are indicative of the reducing conditions of ore deposition, participation of magmatogenic fluid in ore formation, and the enclosing rocks being the possible sources of ore material. Isotope studies indicate that the ore-forming fluid has a mixed, metamorphogenic–magmatogenic composition. The obtained results make it possible to qualify the examined objects as Au deposits associated with granitoid intrusives.

scholarly journals Leaching Tc-99 from SRP Glass in Simulated Tuff and Salt Groundwaters

1987 ◽  
Vol 112 ◽  
Author(s):  
N. E. Bibler ◽  
A. R. Jurgensen
Keyword(s):  
Major Elements ◽  
Free Solution ◽  
Glass Forming ◽  
Ph Values ◽  
Mass Losses ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Carrier Free ◽  
J 13 ◽  
Very High

AbstractResults of leach tests with Tc-99 doped SRP borosilicate waste glass are presented. The glass was prepared by melting a mixture of SRP 165 powdered frit doped with a carrier free solution of Tc-99 at 1150°C. Dissolution of portions of the resulting glass indicated that the Tc-99 was distributed homogeneously throughout the glass. Static leach tests up to 90 days were performed at 90°C in J-13 tuff groundwater or WIPP brine A at a SA/V of 100m−1. Normalized mass losses were calculated for Tc-99 as well as all the major elements in the glass. Results indicated that under ambient oxidizing conditions Tc-99 leached no faster than the glass-forming elements of the glass. In J-13 water, Tc-99 leached congruently with B. In WIPP brine A, it leached congruently with Si. Leach rates for Li were higher in both groundwaters, probably due to a contribution from an ion exchange mechanism. Leach tests were performed under reducing conditions in J-13 water by adding Zn/Hg amalgam to the leachate. In these tests the pH increased significantly, probably because of the reaction of the amalgam with the water. In a 21-day test, the pH Increased to 13 and leach rates for the glass were very high. Even though there was significant dissolutiop of the glass, the normalized mass loss based on Tc-99 was only 0.02g/m2. This result and the fact that reducing conditions at normal pH values do not significantly affect the dissolution of the glass, indicate that the low concentrations for Tc-99 obtained under reducing conditions are due to its solubility and not due to an increased durability of the glass.

The Corrosion of Spent UO2 Fuel in Synthetic Groundwater

1985 ◽  
Vol 50 ◽  
Author(s):  
R. S. Forsyth ◽  
L.O. Werme
Keyword(s):  
Leaching Rate ◽  
Experimental Conditions ◽  
Ph Values ◽  
Reducing Conditions ◽  
Radiolytic Decomposition ◽  
Congruent Dissolution ◽  
Synthetic Groundwater ◽  
Alpha Radiolysis ◽  
High Burnup ◽  
Decomposition Of Water

AbstractLeaching of high burnup BWR fuel for up to 3 years showed that both U and Pu attain saturation rapidly at pH 8.1, giving values of 1–2 mg/l and 1 μg/l respectively. The leaching rate for Sr-90 decreased from about 10−5/d to 10−7/d but was always higher than the rates for U, Pu, Cm, Ce, Eu and Ru. Congruent dissolution was only attained at pH values of about 4.The hypothesis that alpha radiolytic decomposition of water is a driving force for UO2 corrosion even under reducing conditions has been examined in leaching tests on low burnup (low alpha dose-rate) fuel. No significant effect of alpha radiolysis under the experimental conditions was detected.

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