银在含氨基酸热液中的物理化学行为

考虑到银主要富集在中低温热液阶段，同时考虑到成矿溶液中氨基酸的存在及其不同类型，对含银矿物样品在中性、碱性和酸性氨基酸热液中的物理化学行为分别进行了实验研究。结果表明，含有酸性氨基酸（谷氨酸）的热水溶液，比仅含ＮａＣｌ的热卤水、含碱性氨基酸（赖氨酸）和中性氨基酸（氨基乙酸和氨基丙酸）的热水溶液，更有利于银的活化和迁移。实验同时表明，银与各氨基酸形成的易溶配位化合物的稳定性受到温度的强烈影响。在２５℃左右，是银－氨基酸配位化合物稳定存在的最适宜温度条件；在１００℃以上，随温度的逐渐升高，银在含氨基酸热液中的溶出量明显减少。表明银－氨基酸的配位化合物强烈地分解，而使银得以更多地沉积。银在含氨基酸热液中的这种物理化学行为，和铅在含有酸性氨基酸（谷氨酸）、铜在含有碱性氨基酸（赖氨酸）热液中的活化、迁移与沉积作用不无相似之处     

金在花岗质熔体中溶解度的初步实验研究

以合成花岗岩、水、不同浓度的盐酸溶液、氢氟酸溶液作为反应初始物,在850℃,100 MPa,接近于NNO的条件下开展了金在不同花岗质熔体中溶解度的实验研究,实验固液相产物中的金含量使用石墨炉原子吸收法测定。实验结果显示,金在花岗质熔体中的溶解度变化范围为1.87～156.62μg/g,流体相中金的溶解度为0.31～6.92μg/g;金在熔体相中的溶解度较其在共存液相中的高。花岗质熔体相中金的溶解度明显受熔体化学组成的影响,过碱性富钠花岗质熔体中金的溶解度明显高些;金在花岗质熔体中的溶解度随着熔体中Na2O/K2O摩尔比增大而增大;在氟氯共存岩浆体系中,氟含量变化对金在熔体相中的溶解度影响不明显,而液相中氯含量增大有利于提高金在流体相中的含量。     

Impact of Montmorillonite and Calcite on Release and Adsorption of Cyanobacterial Fatty Acids at Ambient Temperature

Minerals might act as important sorbents of sedimentary organic matter and reduce biodegradation, which favors the formation of hydrocarbon source rocks in the earth's history. Since most organic matter is degraded during the sinking process, at ambient temperature, it is important to investigate the adsorption capacity of different minerals during this process, to assess the organic loss from primary productivity to sedimentary organic matter. In this study, montmorillonite and calcite have been selected to study the impact of different minerals on the release, adsorption, and deposition of cyanobacterial (Synechococcus elonpata) fatty acids (FAs) at ambient temperature. Gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) have been utilized to detect the variation in fatty acids. Primary results suggest that minerals have a different impact on dissolved organic matter. Montmorillonite can specifically enhance the release of fatty acids from cyanobacterial cells by lowering the pH values of the solution. The adsorption of the dissolved organic matter by montmorillonite will also be enhanced under a lower pH value. Conjunction of fatty acids with montmorillonite to form a complex will favor the sinking and preservation of these organics. Selective adsorption is observed among fatty acids with different carbon numbers. In contrast, calcite does not show any impact on the release and adsorption of organic matter even though it is reportedly capable of acting as a catalyst during the transformation of organic matter at high temperature. The primary data bridge a link between primary productivity and sedimentary organic matter, suggesting the relative importance of claystones in the formation of hydrocarbon source rocks in the earth's history.     

Factors affecting the association of fatty acids with mineral particles in sea water

Certain factors influencing the incorporation, transport and release of fatty acids by clay minerals, calcite and marine sediments have been investigated.Salinity was found to be an important factor. The adsorption of heptadecanoic acid by bentonite clay at 4%. was nearly triple that at 0%.. However, from 4%. to 35%., only a minor adsorption increase occurred. This behavior is believed to be related to flocculation of the clay at the lower salinity range. The pH over the range of 6.0–8.5 has a small influence on fatty acid-clay association, depressing it somewhat as the basicity increases.When the temperature of the fatty acid solution was increased from 0°C to 50°C, a decrease in adsorption on to clay was found. This effect may be due to increased water solubility of the acid at higher temperatures, since solubility is very important in controlling the degree of fatty acid-mineral interaction. Furthermore, apparent solubilization of fatty acids by indigenous dissolved organic matter in sea water reduces adsorption on to clay minerals.Based upon the heat of adsorption of ?14.6 kcal/mole, fatty acids are physically bound to clay minerals by weak van der Waals forces and hydrogen bonds.Bentonite and kaolinite were found to be the most adsorptive minerals investigated, followed in order by illite, montmorillonite and calcite. Sediments from Narragansett Bay were found to lie between illite and montmorillonite in adsorptive capacity after indigenous sediment organic matter had been removed. Sediment organic matter reduced fatty acid uptake by a factor of 1.6.     

不同有机酸对矿物溶解的动力学实验研究

用石英、微斜长石和方解石混合颗粒模拟碎屑组分分别与不同有机酸水溶液进行溶蚀实验,以比较储集层内不同矿物在含低分子量有机酸地层水中溶解的速率,并试图探讨矿物溶蚀的微观机理。结果表明：①所有矿物颗粒都发生了不同程度的溶解,表现为颗粒失重,溶液中SiO2和金属阳离子含量增加,pH值上升。②优先溶解的是方解石,其次是硅酸盐矿物。③温度增加,硅酸盐矿物在水中的溶解度明显增加,而方解石的溶解度基本不变。④由于不同有机酸与二氧化硅和金属阳离子生成的络合物稳定性不同,因此,在不同有机酸水溶液中,矿物的溶蚀速率有较大差别。多官能团有机酸的水溶液中,不同矿物有更大的溶解;但在含有丰富Ca2＋的草酸水溶液中,由于矿物颗粒表面难溶草酸钙的沉淀,方解石的溶解变得更加困难。⑤多官能团有机酸与SiO2形成的多环螯合物由于完全取代了硅氧四面体的氧原子,在水中具有高度稳定性,可能有助于(铝)硅酸盐的溶蚀和硅元素的迁移     

Verwitterungsversuche mit organischen Säuren an einigen schwerlöslichen Fe-Pb-Zn und Cu Erzmineralen,angewendet auf die Genese des Kupferschiefers

The 1–2 mm fraction of FeS₂, Fe₃O₄, PbS, PbSO₄, ZnS, ZnCO₃, Cu₂S and Cu₂(OH)₂CO₃ was dissolved in water, dilute HCl and 0.01 m organic acids (tannin, salicylic acid and citric acid) at 1 atm and 20° C. Duplicate samples of one gram each were placed in 50 ml of solvent with shaking once each day for one month at pH's of 2, 4 and 6. The pH of all the solutions was maintained by periodic addition of either HCl or NaOH. Comparing the results at pH 6, a value observed under surface conditions, the organic acids had a higher metal ion concentration because of their complexing ability. Results at pH 6 in ppm of the metal ions are shown below: For example the Fe concentration dissolved from pyrite in water was 0.02 ppm but 2.3–4.3 in the organic acids. From malachite 0.2 ppm Cu were dissolved by water but 25–1550 ppm by the organic acids. In general Cu minerals seem to be more soluble in organic acids than the Pb, Zn and Fe minerals. The different solution power of the organic acids within the experiments seems not to be caused by the crystallography of the minerals tested. Further there apparently is no preferential complexing of an organic acid with respect to a distinct anion or cation of the minerals. The experiments therefore show, that it is difficult to predict exactly which organic acid is most effective in dissolving minerals. However the experiments should apply to natural weathering conditions of ore minerals and may aid in understanding metal ion transport. For example the origin of the high Cu concentration in the sedimentary “Kupferschiefer” are more easily explained by weathering and transport of Cu in the form of organo-metallic complexes than by reaction with only water. The Cu content in organic acids is much higher than in water and the Cu concentration in the solutions now is not so strongly controlled by the solubility of Cu-cabonates and phosphates.     

Deposition rates of polysilicic acid with up to 10 M calcium ions

Cementitious materials used for radioactive waste repository construction complicate the performance assessment of radioactive waste systems because the use of cement may greatly alter the pH (8–13) of groundwater and release constituents such as calcium ions. Under such conditions, it is important to clarify also the dynamic behavior of silica (silicic acid), in order to evaluate the alteration in the chemical and physical properties of the fractured layer or the host rock surrounding the repository. Since silica undergoes polymerization, precipitation or dissolution depending on the pH and/or temperature, the behavior of silica would be greatly complicated in the presence of other ions. This study is focused on the deposition rates of polysilicic acid and soluble silicic acid with up to 10⁻³ M Ca ions. In the experiment, Na₂SiO₃ solution (250 mL, pH > 10, 298 K) was poured into a polyethylene vessel containing amorphous silica powder (0.5 g), and a buffer solution, HNO₃, and CaNO₃ as Ca ions were sequentially added into the vessel. The pH of the solution was set to 8. The silica, initially in a soluble form at pH > 10 (1.4 × 10⁻² M), became supersaturated and either deposited on the solid surface or changed into the polymeric form. Then the concentrations of both poly- and soluble silicic acid were monitored over a 40-day period. The decrease of polysilicic acid became slow with an increase in the concentration of Ca ions in the range of up to 10⁻³ M. In general, the addition of electrolytes to a supersaturated solution accelerates the aggregation and precipitation of polymeric species. However, the experimental result showed that polysilicic acid in the presence of Ca ions is apparently stable in solution, compared with that under a Ca-free condition. On the other hand, the concentration of soluble silicic acid in the presence of Ca ions immediately became metastable, that is, slightly higher than the solubility of soluble silicic acid. Its dynamic behavior was similar to that in the Ca-free condition.     

有机质与金相互作用的实验研究

用实验方法研究了含原油水溶液、油田卤水、腐植酸、脂肪酸、氨基酸及无水体系中原油对金的络合及迁移作用。结果表明,原油、腐植酸对金有很强的络合能力,水溶液中含少量的原油即可大大提高水溶液对岩石中金的淋滤活化能力。沉积地层成岩过程中产生的低熟有机质可能是促进沉积改造型金矿床矿源层中金活化迁移的重要因素。     

Amino acid racemization in amber-entombed insects: implications for DNA preservation

DNA depurination and amino acid racemization take place at similar rates in aqueous solution at neutral pH. This relationship suggests that amino acid racemization may be useful in accessing the extent of DNA chain breakage in ancient biological remains. To test this suggestion, we have investigated the amino acids in insects entombed in fossilized tree resins ranging in age from <100 years to 130 million years. The amino acids present in 40 to 130 million year old amber-entombed insects resemble those in a modern fly and are probably the most ancient, unaltered amino acids found so far on Earth. In comparison to other geochemical environments on the surface of the Earth, the amino acid racemization rate in amber insect inclusions is retarded by a factor of >10(4). These results suggest that in amber insect inclusions DNA depurination rates would also likely be retarded in comparison to aqueous solution measurements, and thus DNA fragments containing many hundreds of base pairs should be preserved. This conclusion is consistent with the reported successful retrieval of DNA sequences from amber-entombed organisms.     

Geochemical modeling of cyanide in tailing dam gold processing plant

This research is aimed at investigating possible neutralization of cyanide in tailing dam of Muteh gold processing plant in Isfahan, Iran at various conditions such as pH and temperature using USEPA Visual MINTEQ geochemical model simulation. The model is based on geochemical equilibrium which uses the simultaneous solution of the non-linear mass action expressions and linear mass balance relationships to formulate and solve the multiple-component chemical equilibrium problems. In this study the concentration of aqueous species in tailing dam as an aqueous, solid and gaseous were used as input in the model. Temperature and pH variation were simulated. The results of the model indicated that cyanide may be complexes in 10 < pH < 5. In other pH values complexation is not important. The results also indicated that cyanide reduction mechanism in acidic pH and temperature above 30°C is due to cyanide acid formation which is vaporized.     

低温常压条件下NaCl-H_2O体系对铜活化迁移的影响因素Ⅱ:pH值和盐度

文章采用动态模拟实验研究了卤水NaCl-H2O体系不同盐度、酸碱度对砂岩中铜元素的活化迁移作用。结果表明,在常压室温环境下,卤水盐度越高,越有利于含铜砂岩中铜的活化迁移,不同盐度卤水对铜的活化强度表现为w(NaCl)为25%的溶液w(NaCl)为20%的溶液w(NaCl)为10%的溶液w(NaCl)为5%的溶液。酸碱度条件模拟实验,揭示了强酸(pH=0.71)或者强碱(pH=10.28)环境有利于铜的活化迁移,尤其是在强酸(pH=0.71)条件下,可极大增强铜的溶解性,这对于解释蒸发岩盆地含铜卤水的成矿过程具有重要的理论和实际意义。     

油田卤水中短链有机酸的来源,分布及其地球化学意义

在几乎所有的油田卤水(地层水)中都含有高浓度的短链有机酸,通常乙酸根是其中最丰富的有机阴离子。大量的模拟实验表明干酪根是有机酸最主要的来源。短链有机酸有着重要的地球化学意义,(1)可以作为石油勘探的近似指示物,(2)它们可能是天然气中某些主要成分的母体,(3)它们是地层水中最主要的弱酸阴离子,因此控制了地层水的pH值的缓冲能力,(4)作为还原剂,它们控制了地层水的Eh值和多价元素的浓度,(5)实验表明,它们还能够与储集岩中的铝、钙、硅等无机离子形成可溶络合物,使长石类矿物的溶解作用增强,从而导致砂岩储层中次生孔隙加大。     

Effect of low-molecular-weight organic acids on the distribution of mobilized Al between soil solution and solid phase

Low-molecular-weight (LMW) organic acids occur widely in soils. Results in pure mineral systems and podzols suggest that LMW organic acids can promote the dissolution of Al from kaolinite, Al oxides and soils, but limited information is available concerning the role of these organic acids on Al mobilization in variable charge soils as yet. This paper deals with the effect of LMW organic acids on Al mobilization and mobilized Al distributed between the solution phase and exchangeable sites in two acidic variable charge soils. The results indicated that LMW organic acids accelerated Al mobilization through proton- and ligand- promoted reactions. The ability of different organic acids to mobilize Al followed the order: citric acid > oxalic acid > malonic acid > malic acid > tartaric acid > salicylic acid > lactic acid > maleic acid. This order was in general agreement with the magnitude of the stability constants of Al–organic acid complexes. The ratio of soluble Al to exchangeable Al also increased as the stability constants increased. These results showed that the organic acids with strong Al-complexation capacity were most effective in Al mobilization, whereas the weak organic acids promoted the retention of mobilized Al by the soil exchangeable sites. Increase in both organic acid concentration and solution pH promoted Al mobilization and also increased the ratio of soluble Al to exchangeable Al due to the increase in the concentration of the effective organic ligands, especially in the strong organic acid systems. These findings may have their practical significance for establishing more effective amelioration procedures for variable charge soils with increased acidity and higher mobility of Al.     

Stability, solubility and maximum metal binding capacity in metal–humic complexes involving humic substances extracted from peat and organic compost

The aim of this work is to investigate the influence of pH and the metal:humic substances (HS) ratio on HS complexing capacity and the stability and solubility of metal–HS complexes in solution. We selected four HS with different physicochemical properties and studied their interaction with Cu(II), Zn(II) and Fe(II) at different pH and metal:HS ratios. The selected HS were a humic acid and a whole humic extract (containing the humic and fulvic acids) extracted from black peat, and a fulvic acid and a whole humic extract extracted from a compost of grape solid wastes.Our results showed that HS complexing capacity significantly varied as a function of pH, thus indicating the influence of both functional group ionisation and molecular conformation on this property. As was expected, total acidity affected the complexing capacity of the selected HS.The results related to stability and complexing capacity indicated the possible presence of two binding patterns, one at acid-neutral pH probably involving carboxylates, and another at alkaline pH probably involving carboxylates and phenolic groups. The relationship between these binding patterns and the strength of the binding process varied according to the complexed metal.Complex solubility was greatly affected by the ratio between the concentration of free ionised functional groups and the molecular weight in the HS studied.     

安徽铜陵狮子山矿田铜、金共生与分离的热力学研究

狮子山矿田是安徽铜陵矿集区内最具代表性的大型铜金多金属矿田.矿田内铜、金矿床或矿体既各自独立产出,义相互共生或伴生,铜矿化和金矿化在时间上和空间上存在既共生又分离的现象.本文选择矿田内代表性铜矿床和金矿床开展系统的流体包裹体地球化学研究,并进行成矿流体中铜、金溶解度的热力学理论计算和1分析,探索铜、金共生与分离的机制和...     

Formation of gold deposits: a metamorphic devolatilization model

A metamorphic devolatilization model can explain the enrichment, segregation, timing, distribution and character of many goldfields such as those found in Archean greenstone belts, slate‐belts and other gold‐only provinces. In this genetic model, hydrated and carbonated greenschist facies rocks, particularly metabasic rocks, are devolatilized primarily across the greenschist–amphibolite facies boundary in an orogenic setting. Devolatilization operates on the scale of individual mineral grains, extracting not just H₂O and CO₂ but also S and, in turn, Au. Elevated gold in solution is achieved by complexing with reduced S, and by H₂CO₃ weak acid buffering near the optimal fluid pH for gold solubility (the buffering is more important than being at the point of maximum gold solubility). Low salinity ensures low base metal concentrations in the auriferous metamorphic fluid. Migration of this fluid upwards is via shear zones and/or into hydraulic fracture zones in rocks of low tensile strength. The geometry of the shear zones dictates the kilometre‐scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold. Deposition of gold from solution necessitates breakdown of the gold–thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon‐bearing host rocks and/or by sulphidation of wallrocks to generate iron‐bearing sulphide and precipitated gold. As such, black slate, carbon seams, banded iron formation, tholeiitic basalt, magnetite‐bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields. Gold deposition is accompanied by carbonation, sulphidation and muscovite/biotite alteration where the host rock is of suitable bulk composition. The correlation of major gold deposits with rock type, even when the gold is primarily in veins, argues for rock‐dominated depositional systems, not fluid‐dominated ones. As a consequence, a general role in gold deposition for fluid mixing, temperature decrease and/or fluid pressure decrease and boiling is unlikely, although such effects may be involved locally. Several geological features that are recorded at gold‐only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process. Overprinting by higher‐grade metamorphism and deformation, and/or (palaeo)‐weathering may provide many of the most‐obvious features of goldfields including their mineralogy, geochemistry, geometry, small‐scale timing features, geophysical response and even mesoscopic gold distribution.     

Leaching of an oxide gold ore with chloride/hypochlorite solutions

An oxide gold ore was subjected to chloride/hypochlorite leaching at room temperature. The effects of three factors, including Ca(OCl)₂ vs. NaOCl, OCl⁻ concentration, and HCl concentration on gold leaching performance were investigated. Due to formation of CaOCl⁺ complex in solution and hence less reactivity, calcium hypochlorite produces a sluggish gold leaching kinetics, taking twice the time (46 h) to achieve maximum gold recovery of 58% compared to sodium hypochlorite. 10 g/L of total initial hypochlorite species in solution produces reasonable gold recoveries. The amount of added HCl and hence the initial pH was found to have a major effect on gold leaching kinetics and maximum gold recovery. A high level of 9 g/L of added HCl causes HClO to be very reactive, producing very fast kinetics, reaching 67% gold extraction in 4 h. It also causes a faster consumption of hypochlorous acid, through catalytic decomposition (by NiO and CuO) and disproportionation. Hypochlorous acid reactions with sulfide and ferrous content of ore proceed very slowly in the pH range of 4–11. Gold–chloro complexes are strongly adsorbed on quartz component of ore. To minimize this undesirable adsorption of gold–chloro species, the aging time must be limited to a few hours only.     

Geochemical dispersion of heavy metals via organic complexing: A laboratory study of copper,lead, zinc,and nickel behaviour at a simulated sediment-water boundary

Data are presented in this study from laboratory model experiments describing the behaviour of Cu, Pb, Zn and Ni at a simulated sediment-water boundary. The interactions involved are sorption by kaolin and by bentonite, organic complexing in solution by fulvic acid and by humic acid, carbonate reactions, hydrolysis, and desorption of the cations from a clay-bound phase and from their metal hydroxides by the organic acids. The organic acids increase the solubility of Cu, Zn and Ni in the presence of clay. The Pb solubility is variable and can even decrease, particularly at acidic pH, with organic complexing likely due to colloidal coagulation. Both Zn and Ni are influenced by hydrolysis at basic pH. When carbonate was added to the metal-organic acid-clay mixtures, a further decrease in solubility was observed for Ni and, to a lesser extent, for Zn. The organic acids prove capable of remobilizing Cu, Pb, Zn and Ni from the solid phases examined. However, there is a general kinetic hindrance to the desorption particularly at basic pH. Copper desorption appears to be the most kinetically hindered. Conclusions pertinent to the geochemical dispersion of these metals are drawn.     

Thermodynamic study of the association and separation of copper and gold in the Shizishan ore field, Tongling, Anhui Province, China

The Shizishan ore field is the largest gold–copper ore field in the Tongling ore district of Anhui Province, China. Copper and gold deposits in the district are present as one-commodity deposits or as deposits with both commodities. Copper and gold mineralization are either cogenetic or are temporally and spatially distinct. We present the results of systematic geochemical analysis of fluid inclusions from typical Au–Cu deposits in the Shizishan ore field; these data are used to determine the solubility of Cu and Au in the ore-forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization. Our results indicate that copper in the ore-forming fluids was transported as CuCl₂⁻ and CuCl⁰ complexes and that the solubility of copper was controlled by variations in Cl⁻ concentration. In addition, the precipitation of copper was controlled by changes in temperature, pH, fO₂, and fO₂. In comparison, gold in the ore-forming fluids was transported as Au(HS)₂⁻ and Au₂S(HS)₂²⁻ complexes, and the solubility of gold was controlled by variations in total sulfur concentration; the precipitation of gold was controlled by temperature, pH, fO₂, and fO₂. These differences between the two elements meant that copper and gold in the ore-forming fluids responded in different ways to changes in physicochemical conditions. Copper precipitated under relatively acidic conditions at high temperatures, while gold precipitated under weakly alkaline conditions at relatively low temperatures; this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the Shizishan ore field.     

The distribution and nature of amino acids and other nitrogen-containing compounds in Lake Ontario surface sediments

Five surface sediment samples (0–3 cm), two suspended sediment samples and a zooplankton sample from Lake Ontario were analysed for nitrogen-containing compounds. Amino acids, amino sugars, ethanolamine and urea were separated and characterized by ion-exchange chromatography. Free amino acids and soluble combined amino acids and amino sugars accounted for less than 0–25 per cent of the total nitrogen in the sediments. Insoluble combined amino acids and amino sugars were the most abundant nitrogen fraction in the sediments, making up from 49 to 55 per cent of the total nitrogen. Evidence is presented that asparagine, glutamine and citrulline are present in the interstitial waters and may make up part of the sediment organic nitrogen that was not characterized.The free amino acids released by the proteolytic enzyme, pronase, from the interstitial waters and sediment humic and fulvic acid extracts were determined. Pronase released 65 per cent of the soluble combined amino acids and 34 per cent of the fulvic acid amino acids as free amino acids. Enzyme activity was inhibited in the presence of the humic acid extract. The results indicate that the combined amino acids in the interstitial waters and fulvic acid extracts are intermediates between the primary aquatic detritus and the sediment humic acids. The enzyme experiments and infra-red data indicate that part of the sediment amino acids are combined through peptide linkages.