Biotransformation of amide using Bacillus sp.: isolation strategy, strain characteristics and enzyme immobilization

Amidase hydrolases/acyltransferases are of considerable industrial interest due to potential applications in the production of useful hydroxamic acids. The test strain, capable of acetamide degradation, was isolated by an enrichment technique with acetamide as sole source of nitrogen. Based on morphology, physiological tests and biochemical tests, this isolate was identified as Bacillus sp. and on the basis of 16S Ribosomal ribonucleic acid sequence, a phylogenetic tree was drawn and was identified as Bacillus megaterium. Resting cells containing active acyltransferase enzyme were prepared and immobilized in the gel beads of sodium alginate, agar, polyacrylamide and polyvinyl alcohol?Calginate. The beads were tested for acyltransferase using Iron (III) chloride reagents at 55°C and were found to be affected by substrate concentration, type of buffer, buffer pH and reaction temperature. These factors were optimized using sodium alginate immobilized beads. This study proved useful in understanding the technique of immobilization of acyltransferase enzyme, its operational stability and its importance in the synthesis of hydroxamic acid.     

A novel halo-alkalo-tolerant bacterium, <Emphasis Type="Italic">Marinobacter alkaliphilus</Emphasis> ABN-IAUF-1, isolated from Persian Gulf suitable for alkaline lipase production

Alkaline lipases are one of the most important industrial enzymes that have several uses in detergents, food, pharmaceutical, cosmetics, textile, leather and biomedical industries. For screening the lipase-producing bacteria, olive agar A, B, C and Rhodamine B agar were used. The best environmental conditions and their interactions for alkaline lipase production were obtained using Taguchi statistical test. Enzyme purification was carried out by ammonium sulfate precipitation, dialysis and SDS-PAGE, respectively. The best alkaline lipase-producing strain, WS3, isolated from Persian Gulf, was named Marinobacter alkaliphilus ABN-IAUF-1 (GenBank accession number: KP403723). The maximum enzyme activity of 37.00 (μ/ml) was measured in the presence of coconut oil as the carbon source in oil broth medium after 48-h incubation at the pH 8.00 and 30 °C. The most effective factors in enzyme production were nitrogen and carbon sources with 32 and 25% of influence, respectively. Precipitation and dialysis increased the enzyme purity 1.90–2.33 times. The total enzyme activity of 925.00 ± 20.00 U in the oil broth, 96.00 ± 7.00 U after precipitation with ammonium sulfate and 60.00 ± 5.00 U after dialysis was measured. The molecular weight of alkaline lipase was measured as 55 kDa. In conclusion, this is the first report of production of alkaline lipase by a halo-alkalophilic bacterium, Marinobacter alkaliphilus ABN-IAUF-1, that was obtained from Persian Gulf, Iran. The application of enzymes produced by extremophiles such as Marinobacter alkaliphilus could be an asset in the modern environmental microbiology as well as food and industrial biotechnology.     

Carbon isotope effects associated with mixed-acid fermentation of saccharides by Clostridium papyrosolvens

In anoxic environments, microbial fermentation is the first metabolic process in the path of organic matter degradation. Since little is known about carbon isotope fractionation during microbial fermentation, we studied mixed-acid fermentation of different saccharides (glucose, cellobiose, and cellulose) in Clostridium papyrosolvens. The bacterium was grown anaerobically in batch under different growth conditions, both in pure culture and in co-culture with Methanobacterium bryantii utilizing H₂/CO₂ or Methanospirillum hungatei utilizing both H₂/CO₂ and formate. Fermentation products were acetate, lactate, ethanol, formate, H₂, and CO₂ (and CH₄ in methanogenic co-culture), with acetate becoming dominant at low H₂ partial pressures. After complete conversion of the saccharides, acetate was ¹³C-enriched (α_sacc/ac = 0.991-0.997), whereas lactate (α_sacc/lac = 1.001-1.006), ethanol (α_sacc/etoh = 1.007-1.013), and formate (α_sacc/form = 1.007-1.011) were ¹³C-depleted. The total inorganic carbon produced was only slightly enriched in ¹³C, but was more enriched, when formate was produced in large amounts, as ¹²CO₂ was preferentially converted with H₂ to formate. During biomass formation, ¹²C was slightly preferred (α_sacc/biom ≈ 1.002). The observations in batch culture were confirmed in glucose-limited chemostat culture at growth rates of 0.02-0.15 h⁻¹ at both low and high hydrogen partial pressures. Our experiments showed that the carbon flow at metabolic branch points in the fermentation path governed carbon isotope fractionation to the accumulated products. During production of pyruvate, C isotopes were not fractionated when using cellulose, but were fractionated to different extents depending on growth conditions when using cellobiose or glucose. At the first catabolic branch point (pyruvate), the produced lactate was depleted in ¹³C, whereas the alternative product acetyl-CoA was ¹³C enriched. At the second branch point (acetyl-CoA), the ethanol formed was 15.6-18.6‰ depleted in ¹³C compared to the alternative product acetate. At low hydrogen partial pressures, as normally observed under environmental conditions, fermentation of saccharides should mainly result in the production of acetate that is only slightly enriched in ¹³C (<3‰).     

Specific methanogenic activity of halophilic and mixed cultures in saline wastewater

Wastewater containing high concentrations of salt, are difficult to treat using biological treatment processes, especially anaerobic processes. Limited information is available on methanogenic activity in saline environments. The objective of this research was to investigate the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic and methanogenic bacteria, at various levels of salinity, in terms of lag period and specific methanogenic activity (SMA) at two temperatures. For the halophilic bacteria at 35 °C, the initial SMA ranged from 0.46 to 0.90 g acetate/g VSSd, but decreased at higher salt concentrations. The maximum SMA varied from 1.2 to 2.08 g acetate/g VSSd. High sodium chloride concentrations had a significant adverse effect on digester sludge. At 25 °C, at salt concentrations of 30 g/l and above, the digester sludge could not acclimate even in 50 days. Little difference was observed in the maximum SMA of mixed culture and halophilic bacteria at high salt concentrations of40–50 g/l.     

Co-metabolic decolorization of a textile reactive dye by <Emphasis Type="Italic">Aspergillus fumigatus</Emphasis>

In the present study, a widely used reactive dye, Color Index (C.I.) Reactive Blue 268 was utilized for mycoremediation by Aspergillus fumigatus isolated from textile effluent. Complete decolorization of the test dye (0.1 g L^?1) was recorded within 6 days of static incubation at 27 °C in Czapek Dox broth (CDB). However, the isolate was unable to utilize the dye as a sole source of energy in Czapek Dox agar and CDB in absence of sucrose and obligate requirement of a labile carbon source, i.e., sucrose needed for induction of decolorization. Biosorption seems to play the pivotal role in decolorization as evident by coloring of the fungal biomass as that of dye color. The optimal conditions for the highest decolorization were found at 30 °C and pH 6.0 with 6-day-old inoculums supplemented with sucrose (10 g L^?1) and ammonium chloride (2 g L^?1) as a carbon and nitrogen source, respectively. The response of the isolate to increasing dye concentrations was found to be growth inhibitory. Surprisingly, about 65 % of dye decolorization was recorded with heat-inactivated biomass powder within 6 days of static incubation supporting the fact of fungal biosorption. Results of this study have established the candidature of the isolate for biotechnological removal of dyes from disreputable dying effluents.     

Physical–chemical treatment process optimization for high polluting dairy effluents prior fermentation

Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the most polluting due to their organic load content expressed in the chemical oxygen demand (156–240 g·L^?1). Joining the plant wastewater, such effluents contribute to the increase of the polluting load of the wastewater treatment plant input which disturbs the treatment performance. This work proposes an upstream segregation of those dairy effluents for combined physical–chemical and biological treatment. An experimental design was proposed to investigate initial pH, applied temperature and exposure time factor effects on the thermal coagulation process. The fermentation of the resulted supernatants using Lactobacillus lactis ssp. lactis was performed. The optimized thermal coagulation pretreatment was obtained at (pH; T(°C); t(min)): 6, 60 °C and 5 min, with both (B) and (D) effluents. Resulted clarified whey sugar, protein and fat contents were assessed. The physical–chemical treatment resulted in considerable organic matter removal: 45% for (B) samples and 31% for (D) samples of proteins content and almost the total fat content. However, there is no considerable effect on the sugar content reduction, which remains responsible for the major fraction of the whey residual chemical oxygen demand (COD). Clarified whey fermentation using Lactococcus lactis ssp. lactis strain induced important sugar consumption rates. Therefore, important sugar consumption rates were recorded and the COD removal efficiency was improved. The recorded global COD removal efficiency was of about 93%. The proposed combined physical–chemical and biological processes for dairy effluents pretreatment allowed not only to reduce the effluents polluting load, but also to valorize wheys by producing valuable components.     

Gold transport during magmatic degassing: Model experiments

Interaction of metallic gold with (Na, K)Cl salt melts was investigated by the weight-loss method at 700–1000°C using silica glass ampoules. Interaction was not detected in hermetic evacuated ampoules over the whole temperature interval and even after the addition of 5 wt % Na₂SO₄ as a possible oxidizer to the salt. Gold solubility increased sharply in open ampoules, but this was accompanied by the evaporation of salt melt and, possibly, AuCl_x. The limiting gold solubility in the salt melt at 860°C was estimated as 1 wt % or 10000 ppm. The model of gold transport in a gas phase during magmatic degassing invokes shallow gold extraction by salt melt, melt evaporation, and removal of precipitated metallic particles by the gas phase.     

Enhanced electricity generation from whey wastewater using combinational cathodic electron acceptor in a two-chamber microbial fuel cell

While energy consumption is increasing worldwide due to population growth, the fossil fuels are unstable and exhaustible resources for establishing sustainable life. Using biodegradable compounds present in the wastewater produced in industrial process as a renewable source is an enchanting approach followed by scientists for maintaining a sustainable energy production to vanquish this problem for ulterior generations. In this research, bioelectricity generation with whey degradation was investigated in a two-chamber microbial fuel cell with humic acid as anodic electron mediator and a cathode compartment including combinational electron acceptor. Escherichia coli was able to use the carbohydrate originated from whey to generate bioelectricity. The open-circuit potential in absence of mediator was 751.5?mV at room temperature. The voltage was stable for more than 24?h. Humic acid was used as a suitable mediator. In addition, some mixed chemicals were employed as catholyte. Based on polarization curve, the power and current values in the presence of a mixed solution of potassium iodide (KI), ferric chloride [FeCl₃ (??)] and manganese chloride tetrahydride (MnCl₂·4H₂O) with doubling of oxidant (oxygen) concentration using agitation with magnet stirrer in cathode compartment without any buffer solution were boosted to 562.9???W and 1906.1???A, respectively, and demonstrated the best result for power generation.     

Methane-derived high-Mg calcite submarine cement in Holocene nodules from the Fraser Delta, British Columbia, Canada

Carbonate nodules and slabs in late Holocene shelly terrigenous deposits of the modern Fraser River delta (～49°N) are formed close to the seafloor by precipitation from saline pore waters of mainly fibrous to bladed crystals of high-Mg (～ 10–20 mol% MgCO₃) calcite cement as coalescing isopachous crusts on grains. Previous reports that the cement is low-Mg calcite are not supported by this study. Highly negative δ¹³C values of ? 7 to ? 59‰ for the cements indicate that the bulk of their carbonate carbon was derived from the microbiological degradation of organic matter in the deltaic deposits during shallow burial. In particular, the production of biogenic methane (CH₄) by anaerobic bacterial fermentation, its upward migration, chemical or biological oxidation to CO₂ and neutralization in the near-surface sediment, and diffusion to microenvironments relatively enriched in organic components, are a possible set of conditions influencing the process and sites of carbonate cementation. Methane-derived Mg-calcite appears also to be the major submarine cement in several other modern occurrences of lithified shallow-water terrigenous sands and muds at non-tropical latitudes.     

褐煤生物产气规律及其液相体系中阳离子变化特征

为研究褐煤生物产气规律及其液相体系中常见阳离子变化特征,以内蒙古胜利褐煤为产气底物,寺河矿区煤层气井排采水中微生物作为发酵菌群,利用5 L厌氧发酵罐进行模拟生物产气实验,采用离子色谱仪对发酵液中的NH₄+、K+、Ca2+、Mg2+和Na+5种阳离子浓度进行动态监测。结果表明:煤模拟生物产气周期为33 d,分为缓慢增长期、快速增长期和平缓期3个阶段,33 d单位质量煤净产甲烷量最高达23 μmol/g;产气体系中NH₄+（741.5 mg/L）和K+（994.5 mg/L）离子质量浓度变化最为明显,Ca2+（26 mg/L）、Mg2+（10.7 mg/L）和Na+（72 mg/L）次之,表明发酵液中5种阳离子均参与了褐煤生物产气过程,且被不同程度地释放和利用;褐煤生物产气量与阳离子浓度有一定相关性,单位质量煤产气量与NH₄+和K+浓度呈正相关,与Ca2+、Mg2+浓度呈负相关。此外,NH₄+和K+以及Ca2+和Mg2+之间浓度呈显著正相关。由实验结果可知:褐煤生物产气液相体系中4+、K+、Ca2+、Mg2+和Na+5种阳离子会随着煤中有机组分的厌氧降解而缓慢释放、再吸附,同时可被微生物利用参与细胞内的生物化学反应。      

Bioemulsification activity assessment of an indigenous strain of halotolerant Planococcus and partial characterization of produced biosurfactants

Halotolerant bacteria are regarded as effective oil-scavengers in the polluted saltern and seawater. In this regard, a halotolerant Planococcus was isolated from oil-contaminated area of Dezful north springs, Iran, due to its capacity in biosurfactant (BS) production. To facilitate hydrocarbons degradation, in the current study, the efficiency of BS production as function of growth rate of the halotolerant Planococcus was investigated in the vicinity of heavy crude oil by emulsification index (E24). Subsequently, the BS characterization was made by thin-layer chromatography (TLC), gas chromatography (GC) and infrared spectra analysis, and the stability was determined by E24 value measurement over a certain pH (5–9), temperature (20–100 °C) and salt concentration (0–10 % w/v) ranges. The BS production was found to be growth-associated. Detection of a unique band on TLC and GC chromatogram showed the extensive refining capacity of the BS purification, using the medium supernatant under acetone alkaline precipitation followed by oil dissolution from the sediment by carbon tetrachloride. Accordingly, it was clarified that the BS ultimately accumulated outside the cells. The glycolipid quality of the BS was further determined by the routine chemical characterization on TLC and by IR spectra analysis. Moreover, there was no protein detected by lowery total protein assay. Finally, the optimal temperature, pH and NaCl concentration to reach highest E24 values (85.7, 77.0, and 79.0 %) were found at respective 40 °C, pH = 9 and 0 % w/v. Our results revealed the practically potential of strain Dezful Isolate for BS large-scale production as environmentally friendly oil-eliminating agents.     

Effect of Fe2+ amendment on photodegradation kinetics of imidacloprid in moist soil

The present study deals with the effect of Fe²⁺ on degradation kinetics of imidacloprid in moist soil under UV system. The moist soil samples were spiked with imidacloprid and irradiated in specially designed UV-photoreactor. The analysis of imidacloprid was carried out by using HPLC–DAD system. UV irradiation caused about ten fold increase in photodegradation rate of the pesticide. Amendment of soil with Fe²⁺ at concentrations of 30 mg/kg led to a further increase in the rate of photodegradation, i.e., a 98 % degradation of imidacloprid was observed in the presence of iron after 32 days of irradiation. Moreover, the half-life of imidacloprid in Fe²⁺ -amended soil was observed to be reduced to 7 days that in the absence of Fe²⁺ was recorded to be 21 days. Iron was also observed to affect the half-life of imidacloprid in dark. When compared with unsterilized Fe²⁺-amended batch treatments, the t _1/2 in sterilized Fe²⁺-amended batch treatments increased from 58 to 96 days. Imidacloprid-urea was detected by HPLC as the only stable photodegradation byproduct of imidacloprid in the soil.     

Hydrothermal Formation of Lath-Shaped Trioctahedral Smectite with High Crystallinity

Lath-shaped and highly crystalline trioctahedral smectites were synthesized under hydrothermal conditions. The quenched glasses with stoichiometrically dehydrated Na-smectite compositions were treated at （a） 500℃ and 100 MPa for 1 and 11 days; and （b） 300℃ and 100 MPa for 7 days. The crystallinity and particle size of products were dependent on the chemical composition of the starting glass, synthetic temperature and duration of hydrothermal treatment. The high structural ordering and large dimensions of the products were confirmed from the sharpness of XRD peaks; and hydration behavior under controlled relative humidity. Transmission electron microscopy was also performed for the characterization of the particle size of product. Particle sizes vary from ca. 10 nm to a few pm by changing the chemical compositions of the starting materials. The product with the highest structural ordering and largest dimension was obtained from Nao.33（Mg1.83Al0.67）Si4O11 glass treated at 500℃ and 100 MPa for 1 day. The obtained results also confirmed the metastability and compositional dependency in the formation of highly crystalline trioctahedral smectite at hydrothermal conditions.     

Fractionation of stable carbon isotopes during anaerobic production and degradation of propionate in defined microbial cultures

In many anoxic environments propionate is, after acetate, the second most important fermentation product, being degraded further to finally result in CH₄ production. In principle, isotope discrimination can be used to assess the path of organic matter degradation to acetate, CO₂ and CH₄. However, nothing is known about the isotope fractionation in primary and secondary fermentation steps involving propionate, although it is an important precursor of acetate. We therefore studied the degradation of propionate with a syntrophic coculture of Syntrophobacter fumaroxidans and Methanobacterium formicicum. The isotope enrichment factor for propionate degradation to acetate, CO₂ and CH₄ was almost negligible (ε_prop 0.9‰). The fermentative production of propionate was studied in cultures with Opitutus terrae growing on pectin, xylan and starch. These polysaccharides were fermented to acetate, succinate, propionate, H₂ and CO₂. While the δ¹³C value of the initially produced propionate was similar to that of the organic substrates (ca. −28 to −25‰), the δ¹³C value of the other fermentation products was higher. The δ¹³C values of all products generally decreased during the course of fermentation. Finally, a small depletion in ¹³C (ca. 6‰) with respect to the organic substrate was observed for propionate, while the other fermentation products where slightly enriched. Overall, stable carbon isotope discrimination was small during both fermentative production and consumption of propionate in the anaerobic microbial cultures, so that propionate turnover probably only marginally affects isotope fractionation during anaerobic degradation of organic matter.     

Subsolidus and melting relationships for calcite,magnesite and the join CaCO3-MgCO3 36 kb

Subsolidus and melting relations for the CaCO₃-MgCO₃ join at 30 kb have been determined using piston-cylinder apparatus. Data are also presented for the melting curve of CaCO₃ to 30 kb, the decomposition and melting curves of MgCO₃ to 36 kb, and the calcite-aragonite transition at 800°C, 950°C and 1100°C. At 30kb, the melting loop for the CaCO₃-MgCO₃ join extends from 1610°C (CaCO₃) to 1585°C (MgCO₃) through a liquidus minimum at 1290°C (near 42 mole% MgCO₃). The dolomite-magnesite solvus barely intersects the 30 kb melting loop to produce a peritectic reaction at 1385°C. Integration of the new experimental data with other published data permits construction of a complete P-T projection and a sequence of isobars for the CaCO₃-MgCO₃ join for pressures between 5 and 30 kb. The phase relations for this join provide part of the essential framework of the model peridotite system CaO-MgO-SiO₈-CO₂-H₂O, which has particular application to the origin of carbonatitic and kimberlitic magmas. In light of the accumulating evidence for CO₂ in various forms within the upper mantle and of its effect on magmatic processes, analysis of the melting relations in this system is of considerable importance.     

Multiphase carbonate-salt immiscibility in carbonatite melts: data on melt inclusions from the Krestovskiy massif minerals (Polar Siberia)

Minerals of olivine–melilite and olivine–monticellite rocks from the Krestovskiy massif contain primary silicate-salt, carbonate-salt, and salt melt inclusions. Silicate-salt inclusions are present in perovskite I and melilite. Thermometric experiments conducted on these inclusions at 1,230–1,250°C showed silicate–carbonate liquid immiscibility. Globules of composite carbonate-salt melt rich in alkalies, P, S, and Cl separated in silicate melt. Carbonate salt globules in some inclusions from perovskite II at 1,190–1,200°C separated into immiscible liquid phases of simpler composition. Carbonate-salt and salt inclusions occur in monticellite, melilite, and garnet and homogenize at close temperatures (980–780°C). They contain alkalies, Ca, P, SO₃, Cl, and CO₂. According to the ratio of these components and predominance of one of them, melt inclusions are divided into 6 types: I—hyperalkaline (CaO/(Na₂O+K₂O)≤1) carbonate melts; II—moderately alkaline (CaO/(Na₂O+K₂O)>1) carbonate melts; III—sulfate-alkaline melts; IV—phosphate-alkaline melts; V—alkali-chloridic melts, and VI—calc-carbonate melts. Joint occurrence of all the above types and their syngenetic character were established. Some inclusions demonstrated carbonate-salt immiscibility phenomena at 840–800°C. A conclusion in made that the origin of carbonate melts during the formation of intrusion rocks is related to silicate–carbonate immiscibility in parental alkali-ultrabasic magma. The separated carbonate melt had a complex alkaline composition. Under unstable conditions the melt began to decompose into simpler immiscible fractions. Different types of carbonate-salt and salt inclusions seem to reflect the composition of these spatially isolated immiscible fractions. Liquid carbonate-salt immiscibility took place in a wide temperature range from 1,200–1,190°C to 800°C. The occurrence of this kind of processes under macroconditions might, most likely, cause the appearance of different types of immiscible carbonate-salt melts and lead to the formation of different types of carbonatites: alkali-phosphatic, alkali-sulfatic, alkali-chloridic, and, most widespread, calcitic ones.     

Influence of dissolved oxygen concentration and aeration time on nitrite accumulation in partial nitrification process

This study investigated the influence of dissolved oxygen concentration and aeration time on nitrification and nitrite accumulation in an attempt to optimize the recently developed biological-partial-nitritation process for the treatment of strong nitrogen wastewaters. Investigation of dissolved oxygen concentration on ammonium and nitrite oxidation was carried out in a batch reactor. The dissolved oxygen concentration of 0.5 mg O₂/L inhibited both ammonium as well as nitrite oxidation, while increase of dissolved oxygen concentration to ～1 mg O₂/L increased the ammonium oxidation rate and was comparable to that at higher dissolved oxygen concentrations. Experiments were carried out in a sequencing batch reactor for more than 100 days to investigate the influence of aeration time on nitrite accumulation. The dissolved oxygen concentration was controlled at ～1.0 mg O₂/L (in the range of 0.8–1.5 mg/L) during the aeration stage, and volatile suspended solid was maintained at 2.0 g/L while temperature and pH were 30±1°C and 8.3±0.1, respectively. In a typical cycle, complete nitrification occurred at aeration time longer than 6 h. When the aeration time was reduced to 4 h., ～80 % of partial nitritation was achieved. With a further reduction in aeration time to 3 h., nearly 1:1 nitrite/ammonium ratio was yielded. This result revealed that for the reactor design, aeration time determined by feasibility experiments must be considered based on the nitrogen strength in wastewater and biomass concentration in the reactor with dissolved oxygen concentration of ～1.0 mg O₂/L for satisfactory partial nitrification with subsequent processes such as anaerobic ammonium oxidation.     

Segregation roasting of nickel,copper and cobalt from deep-sea manganese nodules

The recovery of nickel, copper and cobalt from ocean manganese nodules by a segregation roasting technique was investigated under a wide range of conditions with several nodule samples all of which gave similar results. The best conditions for the segregation of the metals were achieved with CaCl₂ as the chloride source at a batch retention time of approximately two hours; the highest recoveries were obtained at approximately 850°C for copper and at 1,050°C for nickel and cobalt. At 850°C, copper recovery was 75%, but nickel and cobalt recoveries were only about 25%. At 1,050°C, the nickel and cobalt recoveries were increased to about 60%, but the copper recovery dropped to only 35%. Electron-probe microanalysis showed the segregated metal to be an alloy, indicating that gaseous reactions play an important role in the reduction of chlorides to metal during the process.     

Subsolidus and melting relations for the join CaCO3-MgCO3 at 10 kbar

Mixtures of pure dry CaCO₃ and MgCO₃ were reacted at 10 kbar in a piston-cylinder apparatus. Solidus and liquidus boundaries were delineated by interpretation of quenched textures. X-ray determined compositions of quenched carbonates are not a reliable guide to the phase relations. The binary melting loop for CaCO₃-MgCO₃ extends from CaCO₃ at 1460°C through a liquidus minimum near 30 wt% MgCO₃ and 1075°C, and it is terminated at the incongruent melting reaction for dolomite solid solution at 1125° C (liquid with 32 wt% MgCO₃) Magnesite solid solution dissociates at 1090°C to produce dolomite + periclase + CO₂, truncating the dolomite-magnesite solvus. The 10 kb liquidus minimum at 1075°C and 30 wt% MgCO₃ occurs at lower temperature and higher $\text{Ca}\text{Mg}$ ratio than the 27 kbar liquidus minimum at 1290°C and 38 wt% MgCO₃. This relationship suggests that the first liquid produced by melting of a carbonate-bearing peridotite has increasing $\text{Mg}\text{Ca}$ ratio with increasing pressure. These phase relations provide part of the framework required to trace paths of crystallization of kimberlite and carbonatite magmas.     

Carbonatite melts and genesis of apatite mineralization in the Guli pluton (northern East Siberia)

Inclusions of mineral-forming environments in apatite-containing ijolites and magnetite–phlogopite–apatite ores in carbonatites were studied to elucidate the genesis of apatite mineralization in the Guli alkaline ultramafic carbonatite massif. Primary inclusions of carbonate–salt and carbonate melts have been discovered and studied. The carbonate–salt melt inclusions are of alkaline high-Ca composition and are enriched in P, Sr, SO₃, and F (wt.%): CaO—30–40, Na₂O—5–12, K₂O—2–4, P₂O₅—1–3, SO₃—1.5–3, and SrO—1–3. They also contain minor MgO, FeO, BaO, and SiO₂ (tenths and hundredths of percent). The homogenization temperature of these inclusions is 850–970 °C. The carbonate inclusions contain predominant CaO (54–67 wt.%) and minor MgO, FeO, SrO, Na₂O, and P₂O₅ (tenths of percent). Their homogenization temperature is 840–860 °C. Similar primary carbonate–salt and carbonate inclusions were found in garnet, and secondary ones were detected in silicate minerals (clinopyroxene and nepheline) of ijolites. Clinopyroxenes of ijolites also contain primary inclusions of alkaline ultramafic high-Ca melts similar in composition to melilitite-melanephelinites highly enriched in P, SO₃, and CO₂ (wt.%): SiO₂—41–46, Al₂O₃—8–16, FeO—2–8, MgO—3–6, CaO—12–20, Na₂O—2–9, K₂O—1–6, P₂O₅—0.4–2.1, SO₃—0.2–2.3, and Cl—0.02–0.35. According to the obtained data, apatite of the magnetite–phlogopite–apatite ores and ijolites of the Guli pluton crystallized from phosphorus-rich alkaline carbonate–salt melts at 850–970 °C. The generation of these melts was, most likely, due to the silicate–salt immiscibility in melilitite-melanephelinite melts highly enriched in salts, which occurred either at the final stages of clinopyroxene crystallization or during the formation of melilite. The presence of alkalies, S, F, and CO₂ in spatially separated carbonate–salt melts contributed to the concentration and preservation of phosphorus in them at low temperatures, which led to the formation of apatite mineralization in ijolites and ore deposit in carbonatites.© 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.