Adsorption of anionic dye on magnesium hydroxide-coated pyrolytic bio-char and reuse by microwave irradiation

Magnesium hydroxide-coated pyrolytic bio-char composite was prepared by chemical precipitation, and the adsorption behavior of anionic dye (directly frozen yellow) onto magnesium hydroxide-coated pyrolytic bio-char was investigated in the batch mode. The Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and X-ray fluorescence spectroscopy of adsorbents were characterized. Adsorption studies were performed at different pH, salt concentration, contacting time and dye concentration. The pH value of the solution influenced the adsorption capacity significantly, and adsorption is favored of pH 6–8. Salt coexisted in solution increased slightly directly frozen yellow adsorption capacity. The isotherm data were analyzed by Langmuir and Freundlich isotherm model, and Langmuir model was better to predict the equilibrium data. Thermodynamic calculations showed that the adsorption was a spontaneous and endothermic process. Exhausted magnesium hydroxide-coated pyrolytic bio-char was treated by microwave irradiation, and yield of regeneration was 98 % in the case of microwave irradiated time 5 min at 320 W. The magnesium hydroxide-coated pyrolytic bio-char can be reused.     

Origin and evolution of the Steamboat Springs siliceous sinter deposit, Nevada, U.S.A.

Siliceous hot spring deposits from Steamboat Springs, Nevada, U.S.A., record a complex interplay of multiple, changing, primary environmental conditions, fluid overprinting and diagenesis. Consequently these deposits reflect dynamic geologic and geothermal processes. Two surface sinters were examined—the high terrace, and the distal apron-slope, as well as 13.11 m (43 ft) of core material from drill hole SNLG 87-29. The high terrace sinter consists of vitreous and massive-mottled silica horizons, while the distal deposit and core comprise dominantly porous, indurated fragmental sinters. Collectively, the three sinter deposits archive a complete sequence of silica phase diagenetic minerals from opal-A to quartz. X-ray powder diffraction analyses and infrared spectroscopy of the sinters indicate that the distal apron-slope consists of opal-A and opal-A/CT mineralogy; the core yielded opal-A/CT and opal-CT with minor opal-A; and the high terrace constitutes opal-C, moganite, and quartz. Mineralogical maturation of the deposit produced alternating nano–micro–nano-sized silica particle changes. Based on filament diameters of microbial fossils preserved within the sinter, discharging thermal outflows fluctuated between low-temperatures (< 35 °C, coarse filaments) and mid-temperatures ( 35–60 °C, fine filaments). Despite transformation to quartz, primary coarse and fine filaments were preserved in the high terrace sinter. AMS ¹⁴C dating of pollen from three horizons within core SNLG 87-29, from depths of 8.13 to 8.21 m (26′8″ to 26′11″), 10.13 to 10.21 m (33′3″ to 33′6″), and 14.81 to 14.88 m (48′7″ to 48′10″), yielded dates of 8684 ± 64 years, 11,493 ± 70 years and 6283 ±60 years, respectively. In the upper section of the core, the stratigraphically out-of-sequence age likely reflects physical mixing of younger sinter with quartzose sinter fragments derived from the high terrace. Within single horizons, mineralogical and morphological components of the sinter matrix were spatially patchy. Overall, the deposit was modified by sub-surface flow of alkali-chloride thermal fluids depositing a second generation of silica, and periodically, by acidic steam condensate formed during periods when the water table was low. Local faulting produced considerable fracturing of the sinter. Hence, the Steamboat Springs sinter experienced a complex history of primary and secondary hydrothermal, geologic and diagenetic events, and their inter-relationships and effects are locked within the physical, chemical and biological signatures of the deposit.     

Geochemistry and Crustal Evolution of Volcano-sedimentary Successions and Orthogneisses in the São Gabriel Block, Southernmost Brazil — Relics of Neoproterozoic Magmatic Arcs

Precambrian metaplutonic rocks of the São Gabriel block in southernmost Brazil comprise juvenile Neoproterozoic calc-alkaline gneisses (Cambaí Complex). The connection with associated (ultra-)mafic metavolcanic and metasedimentary rocks (Palma Group) is not well established. The whole complex was deformed during the Brasiliano orogenic cycle. Both metasedimentary and metavolcanic rocks as well as metaplutonic rocks of the Cambaí Complex have been sampled for geochemical analyses in order to get constraints on the tectonic setting of these rocks and to establish a tectonic model for the São Gabriel block and its role during the assembly of West-Gondwana. The major element compositions of the igneous rocks (Palma Group and Cambaí Complex) indicate a subalkaline character; most orthogneisses have a calc-alkaline chemistry; many metavolcanic rocks of the Palma Group show signatures of low-K tholeiitic volcanic arc basalts. Trace element data, especially Ti, Zr, Y, Nb, of most igneous samples from both the lower Palma Group and the Cambaí Complex indicate origin at plate margins, i.e., in a subduction zone environment. This is corroborated by relative enrichment in LREE, low contents of Nb and other high field strength elements and enrichment in LILE like Rb, Ba, and Th. The data indicate the possible existence of two suites, an oceanic island arc and a continental arc or active continental margin. However, some ultramafic samples of the lower Palma Group in the western São Gabriel block indicate the existence of another volcanic suite with intra-plate character which possibly represents relics of oceanic island basalts (OIB). Trace element data indicate contributions from andesitic to mixed felsic and basic arc sources for the metasedimentary rocks. The patterns of chondrite- and N-MORB-normalized spider diagrams resemble the patterns of the igneous rocks, i.e., LILE and LREE enrichment and HFS depletion. The geochemical signatures of most igneous and metasedimentary samples and their low (⁸⁷Sr/⁸⁶Sr)_t ratios suggest only minor contribution of old continental crust.A geotectonic model for the São Gabriel block comprises east-ward subduction and following accretion of an intra-oceanic island arc to the eastern border of the Rio de la Plata Craton at ca. 880 Ma, and westward subduction beneath the newly formed active continental margin between ca. 750 and 700 Ma. The São Gabriel block represents relics of an early Brasiliano oceanic basin between the Rio de la Plata and Kalahari Cratons. This ocean to the east of the Rio de la Plata Craton might be traced to the north and could possibly be linked with Neoproterozoic juvenile oceanic crust in the western Brasília belt (Goiás magmatic arc).     

Kinetic study of the kaolinite-mullite reaction sequence. Part I: Kaolinite dehydroxylation

The decomposition reaction of kaolinite has been investigated as a function of the defectivity of the starting material and the temperature of reaction. Time resolved energy-dispersive powder diffraction patterns have been measured using synchrotron radiation, both under a constant heating rate (heating rates from 10 to 100° C/min) and in isothermal conditions (in the temperature range 500 to 700° C). The apparent activation energy of the dehydroxylation process is different for kaolinites exhibiting a different degree of stacking fault density. The results of the analysis of the kinetic data indicate that the starting reaction mechanism is controlled by diffusion in the kaolinite particle. The diffusion process is dependent on the defective nature of both kaolinite and metakaolinite. At high temperatures, and at higher heating rates, the reaction mechanism changes and the resistance in the boundary layer outside the crystallites becomes the rate-limiting factor, and nucleation begins within the reacting particle. During the final stage of the dehydroxylation process the reaction is limited by heat or mass transfer, and this might be interpreted by the limited diffusion between the unreacted kaolinite domains and the metakaolinite matrix.     

Structural and petrological evidence for the continuation of the Isfahan fault system across the Urumieh-Dokhtar zone of central Iran

The Isfahan fault system, a north-trending, dextral strike-slip fault across the Sanandaj-Sirjan zone, represents the boundary between the northwestern and the southeastern parts of the Sanandaj-Sirjan zone and it terminates in the north at the southern boundary of the Urumieh-Dokhtar zone. This paper focuses on the continuation of the Isfahan fault system across the Urumieh-Dokhtar zone north of Isfahan city. The Urumieh-Dokhtar magmatic assemblage belt is located along the active margin of the Iranian plate and the Arabian plate. The Karkas fault strikes nearly north-south, has a length of about 40 km, a normal component of movement, and it truncates the Urumieh-Dokhtar zone. Due to the location of this fault and the mechanism similar to the Isfahan fault system, the Karkas fault can be considered a continuation of the Isfahan fault system that has been displaced dextrally by the southwestern bordering faults of the Urumieh-Dokhtar zone. The unique juxtaposition association of the Silurian volcanic rocks in the Urumieh-Dokhtar zone, near the Karkas fault, provides an important evidence regarding the major role of this fault in the geological evolution of the region. The Silurian volcanic rocks outcrop in two districts of the study area and generally are composed of basalts. The alkaline basalt composition is determined from mineralogy and immobile elements geochemistry. The geotectonic setting diagrams classified the Silurian volcanic rocks as the within plate basalts. Thus, an intracontinental rifting under extensional tectonic regime can be inferred as the setting that controlled formation of these volcanic rocks. They were created by an alkaline to transitional magmas generated due to low partial melting at depth. The alkaline basalts were most likely derived from an asthenosphere-dominated mantle source due to extension and partial melting. The north trending extensional faults affected thinned overlying continental lithosphere in the Paleozoic era, facilitating magma penetration and eruption.     

Scandium,chromium, iron,cobalt and nickel in some basic and ultrabasic rocks from west Norway

Sixteen eclogites and ultrabasic rock samples from west Norway have been analyzed for Sc, Cr, Fe, Co and Ni by instrumental neutron-activation analysis.In gneiss-eclogites, Sc and Co give values from about 30 to 60 ppm and Cr and Ni from 180 to 700 ppm. An eclogite surrounded by a peridotite body shows nearly the same content of Sc and Co as do the gneiss-eclogites, but up to 20 times more Cr. Ni is only slightly more enriched in this particular eclogite than in the others.The ultrabasites have only a few ppm Sc, Co concentrates around 100 ppm while the Cr and Ni values are mainly found between 2 and 3,000 ppm.Fe shows an average value of nearly 10%.     

Improved Petrological Modal Analyses from X-ray Powder Diffraction Data by use of the Rietveld Method I. Selected Igneous, Volcanic, and Metamorphic Rocks

Mineral modes have been determined for specimens of eight rocktypes from CuK X-ray powder diffraction data using the Rietveldmethod. The samples include two granites, a granodiorite, adamellite,gabbro, basalt, trachyte, and two granulite-facies metamorphicrocks. Up to eight individual mineral components have been measuredin each sample (no glassy phases were observed), with a detectionlimit of {small tilde}1 wt.%, depending on the mineral assemblage.Marked variations in grain size (i.e., granite vs. trachyte)provide no difficulties for the X-ray method. The X-ray resultscompare very favourably with (1) optical modes determined forthe medium–coarse-grained samples by point counting, (2)normative calculations obtained using locally enhanced catanormand mesonorm software, and (3) corresponding Rietveld modesdetermined, for two samples, from neutron powder data. Wheredifferences occur, these are discussed in relation to the limitationsof each of the methods. The improved accuracy of the X-ray method is due primarily tothe incorporation of the full diffraction profile in the Rietveldanalysis calculations, and the elimination of preferred orientationby collecting the data from samples packed in glass capillaries(i.e., Debye–Scherrer mode). The good agreement of theX-ray and neutron modes shows that the usual problems encounteredwith microabsorption, extinction, and sampling are of littleconcern in these rocks. The results highlight one of the majoradvantages provided by Rietveld modal analysis over the moretraditional ‘reference intensity’ X-ray methods,namely, that the crystal chemistry (and thus the calibrationconstants) of the individual phases can be adjusted dynamicallyduring each individual analysis. This not only provides moreaccurate phase abundances, but also gives important supplementaryinformation about the mineralogy of the major components.     

中亚与亚洲中部晚白垩世的陆生脊椎动物组合对比

通过对前人建议的26个生物地层标志化石存在与否的简约分析,中亚与亚洲中部晚白垩世的陆生脊椎动物组合的相对层位得到了更清楚的揭示。此区最古老的组合是乌兹别克斯坦克孜勒库姆沙漠的Khodzhakul组合(早塞诺曼期),其次为蒙古戈壁沙漠东部BaynShire组的下部和上部的组合(塞诺曼期至桑顿期)。中国内蒙古二连达布苏动物群与中亚的土伦期—桑顿期动物群属于同一类群,因为它们均具龟鳖类Khunnuchelys,前者时代可能为桑顿期。三个中亚的组合(Bissekty、Yalovach和Bostobe组合)中有两个地方性的鳄形类(Kansajsuchus和Tadzhikosuchus)和一个出现于戈壁沙漠的鳄形类(Shamosuchus)化石。戈壁沙漠的坎潘期至马斯特里赫特期组合与北美同期动物群为同一类群。Djadokhta组与BarunGoyot组的坎潘期脊椎动物组合具有高度的地方性,并反应了半干旱的古环境。产自Nemegt组的组合生存于比较潮湿的环境。在组成上,这一组合与其他河流相沉积环境(Bissekty、二连达布苏以及北美Judithian期和Lancian期的组合)相似。具顶饰的鸭嘴龙Saurolophus的存在,支持了Nemegt组合为马斯特里赫特期时代。戈壁沙漠的这三个组合(Djadokhta、Barun Goyot和Nemegt组合)被归为一类,因为它们共同拥有地方性的龟类Mongolemys和兽脚亚目的小驰龙类。亚洲中部和北美的坎潘期至马斯特里赫特期组合与亚洲更加古老的组合不同在于存有暴龙科、肿头龙亚目和鸭嘴龙科。在中亚,由于地区性的海侵,这一时间段内的陆生脊椎动物组合多不清楚。     

Petrology of Lamproites from Smoky Butte, Montana

Hyalo-armalcolite-phlogopite lamproites and sanidine-phlogopitelamproites occurring at Smoky Butte, Montana are rocks formedfrom rapidly quenched, high temperature, uncontaminated lamproiticmagma. Petrographic variations are attributable to differentcooling histories of several batches of compositionally identicalmagma. Compared with other occurrences of lamproite, the rocksare unusually rich in TiO₂ and are characterized by the presenceof abundant armalcolite and the most TiO₂-rich phlogopites yetfound in this paragenesis. Compositional data are given fortitanian phlogopite, olivine, diopside, titanian potassian richterite,armalcolite, sanidine, analcite, and glass. The mafic mineralsare Al-deficient and exhibit very little compositional variation.Original leucite has been pseudomorphed by sanidine or analcite.The latter mineral was probably formed at the same time thatthe glass lost K, and gained Na, during alteration by groundwater.All of the lamproites are strongly enriched in Ta, Hf, and thelight REE (La /Yb = 162–280), and have high MgO and Crcontents. Mineralogical, geochemical, and previously publishedisotopic data are combined in developing a petrogenetic modelwhich suggests that these lamproites were derived from an ancient(2.5 Ga) doubly metasomatized harzburgitic source, and thatthey represent relatively primitive lamproites which were intrudedat near-liquidus temperatures.     

Experimental Melting of Cordierite Gneiss and the Petrogenesis of Syntranscurrent Peraluminous Granites in Southern Brazil

To understand the petrogenesis of peraluminous granites syntectonicto the Dorsal de Canguçu Transcurrent Shear Zone in theSul-rio-grandense Shield, Brazil, melting experiments were performedon one of the potential protoliths, a cordierite-bearing semi-peliticmetasedimentary gneiss (PE-1). Experiments were conducted atpressures of 5, 10 and 15 kbar, at temperatures of 700–900°C,and under fluid-absent and 5% H₂O-present conditions. The experimentsshow that fluid-absent melting begins at near-solidus conditions,around 700°C, promoted by participation of retrogressivephengitic muscovite in the reaction Mus + Kf ± Qz = melt± Fe–Ti oxide ± Als, producing a very smallamount of melt (<9%) with widely ranging composition. Allhypersolidus experiments (>800°C) produced S-type graniticmelts promoted by participation of biotite or cordierite inthe reactions Bio + Pl + Crd + Qz = Px + Fe–Ti oxide +melt at 5 kbar, and Bio + Pl + Crd ± Qz = Grt + Als ±Kf + melt at 10 and 15 kbar, both producing a high amount ofmelt (10–63% by volume). The melt compositions obtainedat 900°C and 15 kbar under fluid-absent conditions, promotedby biotite or cordierite breakdown, are similar to the syntectonicgranites. However, it is unlikely that the granites were formedat this pressure (corresponding to a depth of melting of