A recently discovered dolomite carbonatite at Pogranichnoe, North Transbaikalia, Russia, dated at 624 +/- 3 Ma, contains xenoliths of calcite-bearing dolomite carbonatite with graphite spherulites. ...Apatite and aegirine are the other rock-forming minerals. Chemically the carbonatites are ferrocarbonatite and ferruginous calciocarbonatite. The graphite forms <1 mm up to 1.5 mm diameter spherulites, with Raman spectra similar to published spectra of microcrystalline, amorphous carbon and disordered graphite, with G and D bands at 1,580-1,600 cm -1 and at around 1,350 cm -1 . Alteration has formed Fe-bearing calcite to Ca-bearing siderite compositions not previously reported in nature around the graphite along cracks and fractures. Mineral and stable isotope geothermometers and melt inclusion measurements for the carbonatite all give temperatures of 700 degrees-900 degrees. It is concluded that the graphite precipitated from the ferrocarbonatite magma. There are three candidates to control the precipitation of graphite (a) a redox reaction with Fe II in the magma, (b) potential presence of organics in the magma (c) seeding of, or dissolution in, the magma of graphite/diamond from the mantle, and further work is required to identify the most important mechanism(s). Graphite in carbonatite is rare, with no substantial published accounts since the 1960s but graphite at other localities seems also to have precipitated from carbonatite magma. The precipitation of reduced carbon from carbonatite provides further evidence that diamond formation in carbonate melts at high mantle pressures is feasible. PUBLICATION ABSTRACT
Genetically engineered microorganisms (GEMs) have shown potential for bioremediation applications in soil, groundwater, and activated sludge environments, exhibiting enhanced degradative capabilities ...encompassing a wide range of chemical contaminants. However, the vast majority of studies pertaining to genetically engineered microbial bioremediation are supported by laboratory-based experimental data. In general, relatively few examples of GEM applications in environmental ecosystems exist. Unfortunately, the only manner in which to fully address the competence of GEMs in bioremediation efforts is through long-term field release studies. It is therefore essential that field studies be performed to acquire the requisite information for determining the overall effectiveness and risks associated with GEM introduction into natural ecosystems.
The paper presents mineralogical features and EPMA results of the Khamambettu carbonatites. The mineralogical data suggest that these rocks have been generated in magmatic and hydrothermal stages. ...Mineral geothermometer for carbonatite give temperatures of 790°–980°C. Fluid inclusion measurements in monazite (hydrothermal stage) give temperatures of 220°–290°C. One of the features of the carbonatites is high content of magnesia that is defined by the presence of dolomite, olivine, spinel, phlogopite, Mg-rich ilmenite. Chloritization, serpentinization, amphibolization, silicification processes and occurrence of barite, monazite-(Ce), strontianite, celestine are related to hydrothermal stage. Hydrothermal minerals at the Khamambettu were formed by recrystallization of primary carbonatite minerals in the presence of Ba, (SO
4
)
2−
, REE and Si carried in solution by the hydrothermal fluid.
The largest nephrite bearing province in Russia is located in the southern folded environs of the Siberian Craton. Deposits related to two formational types are established in this area: ...apoultrabasic (Dzhida and East Sayan areas, Paramskii massif) and apocarbonate.
A U-Pb (SHRIMP-II) geochronological study of rocks from the Sayzhenski, Snezhny and Nizhne-Burulzayski massifs, incorporated into the Vitim alkali province (Sayzhenski Complex) has been made. The ...acquired data indicate that the rocks formed in the interval of 520-486 Ma. The proximity of their age to accretionary-collision processes in the Central Asian fold belt, accompanied by intràplate magmatism, has been noted. Two independent stages in the evolution of Vitim Province magmatism are suggested: Early Paleozoic (520-485 Ma) and Late Paleozoic (350-290 Ma).
We report a compact biosensor using genetically engineered whole-cell bioreporters on a CMOS based integrated circuit, also called the
microluminometer, for accurately sensing low concentrations of a ...wide range of toxic substances in both gas and liquid environments. The bioluminescent bioreporters are bacteria that can be genetically altered to achieve bioluminescence when in contact with a targeted substance. The bioreporters are placed in close proximity to the microluminometer thus obviating the need for complex instrumentation to channel light from the bioreporters to the microluminometer. The microluminometer presented here is a more robust design and consumes lower power when compared to the one presented in Bolton et al.'s work E.K. Bolton, G.S. Sayler, D.E. Nivens, J.M. Rochelle, S. Ripp, M.L. Simpson, Integrated CMOS photodetectors and signal processing for very low-level chemical sensing with the bioluminescent bioreporter integrated circuit, Sens. Actuators B 85 (2002) 179–185. The microluminometer includes integrated photodiodes and signal processor and is realized using a standard 0.35
μm CMOS process. The photodiode array is operated with a reverse bias of a few mV and demonstrates a leakage current of 45–60
fA and a minimum detectable signal (MDS) of 0.15
fA while operating at room temperature. We present results from both liquid based and air based testing with salicylate and naphthalene as the analytes, respectively, and genetically altered bacteria,
Pseudomonas fluorescens 5RL, as the bioreporter.
An estrogen-inducible bacterial lux-based bioluminescent reporter was developed in Saccharomyces cerevisiae for applications in chemical sensing and environmental assessment of estrogen disruptor ...activity. The strain, designated S. cerevisiae BLYES, was constructed by inserting tandem estrogen response elements between divergent yeast promoters GPD and ADH1 on pUTK401 (formerly pUA12B7) that constitutively express luxA and luxB to create pUTK407. Cotransformation of this plasmid with a second plasmid (pUTK404) containing the genes required for aldehyde synthesis (luxCDE) and FMN reduction (frp) yielded a bioluminescent bioreporter responsive to estrogen-disrupting compounds. For validation purposes, results with strain BLYES were compared to the colorimetric-based estrogenic assay that uses the yeast lacZ reporter strain (YES). Strains BLYES and YES were exposed to 17{szligbeta}-estradiol over the concentration range of 1.2 x 10⁻⁸ through 5.6 x 10⁻¹² M. Calculated 50% effective concentration values from the colorimetric and bioluminescence assays (n = 7) were similar at (4.4 ± 1.1) x 10⁻¹⁰ and (2.4 ± 1.0) x 10⁻¹⁰ M, respectively. The lower and upper limits of detection for each assay were also similar and were approximately 4.5 x 10⁻¹¹ to 2.8 x 10⁻⁹ M. Bioluminescence was observed in as little as 1 h and reached its maximum in 6 h. In comparison, the YES assay required a minimum of 3 days for results. Strain BLYES fills the niche for rapid, high-throughput screening of estrogenic compounds and has the ability to be used for remote, near-real-time monitoring of estrogen-disrupting chemicals in the environment.
•The rocks crystallized from 18O- and D-depleted magma.•The rocks are products of fractional crystallization from a single parental magma.•Hydrothermal processes were responsible for the change in ...δ18O values.
The Belaya Zima alkaline–carbonatite complex in the East Sayan Mountains, Russia, is a multiphase concentric intrusion, which comprises diverse alkaline silicate rocks and carbonatites. Melteigites are the earliest products of crystallization and they are followed by ijolites–urtites, nepheline syenites, and finally, calcite, calcite–dolomite and ankerite carbonatites. In this paper, we present new geochronological data (Ar–Ar method), chemical and stable isotope (H, C and O) compositions of the main rock-forming minerals in carbonatites and the silicate rocks of the complex. The Ar–Ar dating of phlogopite from ankerite carbonatites is consistent with the age of syenite emplacement and implies that the silicate rocks and carbonatites are likely to be comagmatic. The evolutionary trends of pyroxene, fluorapatite, amphibole and phlogopite are consistent with fractional crystallization from a single parental magma. Primary Nb mineralization is represented by pyrochlore, whereas columbite-(Fe) is a replacement product of pyrochlore at the post magmatic, hydrothermal stage. At that stage, interaction of calcite carbonatites with hydrothermal fluids resulted in the formation of hydrothermal paragenesis comprising dolomite–ankerite, monazite-(Ce), ancylite-(Ce), minerals of burbankite group and Ca–REE fluorcarbonates. The hydrothermal processes were also responsible for cation leaching from pyrochlore, the replacements of phlogopite by tetraferriphlogopite and early Ca-rich pyroxene by aegirine. The stable isotope data suggest that the rocks crystallized from a 18O-depleted magma. Shifts toward higher δ18O values relative to the primary compositions are commonly observed in minerals from carbonatites, which is attributed to hydrothermal processes.
We studied the isotope composition of oxygen and hydrogen in metamorphosed high aluminous rocks of Southwestern Transbaikalia. These rocks were found in the basins of the Dzhida and Selenga rivers ...(Ichetu iskoe, Levo Chemurtaevskoe, Nomogonskoe, Kho ronkhoiskoe kyanite occurrences and the Kyakhtin skaya group of sillimanite occurrences. All studied areas contain mineral associations of the progressive stage and the products of retrograde metamorphism. Based on the RbSr and UThPb (SHRIMP II, zircon) studies, the age of rock transformations ranges within 289282 and 144129 Ma. The Late Paleozoic stage is related to the accretion collisional events and accompanying granite formation. The Mesozoic stage is synchronized with the closing of the MongolOkhotsk Ocean and subsequent processes of the rift formation, alkaline magmatism, and exposure of the metamorphic cores.
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