scholarly journals High-alumina pyroxenite xenoliths from Quaternary basalts of NW Spitsbergen - evidence of continental crust delamination

2019 ◽  
Vol 485 (5) ◽  
pp. 604-608
Author(s):  
M. Yu. Koreshkova ◽  
Yu. B. Marin ◽  
L. P. Nikitina ◽  
H. Downes ◽  
A. A. Tokusheva ◽  
...  
Keyword(s):  
Continental Crust ◽  
Great Depth ◽  
High Alumina ◽  
High Concentration ◽  
Svalbard Archipelago ◽  
Garnet Phase ◽  
Al Content ◽  
Ultramafic Cumulates ◽  
Free Cao ◽  
Equilibrium Range

The origin of spinel-garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al2O3 and MgO and low Cr. The primary magmatic association Spl-Opx-Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr2O3-free CaO-MgO-Al2O3-SiO2 system. The parameters of the Grt-Opx equilibrium range within 1060-1120 °C and 2.2-2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.

Temperature effect on implementation of mining system improvement for the potash-bearing strata in Starobin deposit

2020 ◽  
pp. 74-79
Author(s):  
V. P. Zubov ◽  
◽  
D. G. Sokol ◽  
Keyword(s):  
Longwall Mining ◽  
Great Depth ◽  
Mining Equipment ◽  
High Concentration ◽  
Mining Operations ◽  
Mining System ◽  
Temperature Conditions ◽  
Air Temperatures ◽  
Power Loading ◽  
Production Capacities

Currently mines of Belaruskali actively expand production capacities in the conditions of great depth of productive strata and high concentration of mining operations. High power loading of mining equipment in combination with complicated geotechnical conditions are the major causes of increased air temperatures in longwalls. In view of the intended social and technological improvement, one of the current tasks of the top priority is normalization of temperature conditions in longwalls pursuant to the effective standards. The data required for the set task solution were obtained during underground investigation of geotechnical situations which have influence on temperature of intake air currents in longwalls. This article presents the research findings on the formation of temperature conditions in longwall mining. At the great mining depths (500–600 m and more), the temperature of intake air currents exceeds the maximal allowable values. It is expedient to change to the specially designed pillarless mining flow charts capable to ensure independent ventilation of longwall and power train, and to enable heat transfer between intake air flow and rocks in mined-out areas.

High-Alumina Pyroxenite Xenoliths from Quaternary Basalt of Spitsbergen Island: Evidence for Continental Crust Delamination

2019 ◽  
Vol 485 (2) ◽  
pp. 413-417
Author(s):  
M. Yu. Koreshkova ◽  
Yu. B. Marin ◽  
L. P. Nikitina ◽  
H. Downes ◽  
A. Tokusheva ◽  
...  
Keyword(s):  
Continental Crust ◽  
High Alumina

scholarly journals Subduction of a rifted passive continental margin: the Pohorje case of Eastern Alps–constraints from geochronology and geochemistry

2020 ◽  
Vol 113 (1) ◽  
Author(s):  
Ruihong Chang ◽  
Franz Neubauer ◽  
Yongjiang Liu ◽  
Johann Genser ◽  
Wei Jin ◽  
...  
Keyword(s):  
Continental Crust ◽  
Rift Zone ◽  
Eastern Alps ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Icp Ms ◽  
Hp Metamorphism ◽  
Two Samples ◽  
Ultramafic Cumulates ◽  
T Values

Abstract This study presents geochronological and geochemical data from newly dated Permian granitic orthogneisses associated with the Eclogite-Gneiss unit (EGU) from the southernmost part of the Austroalpine nappe stack, exposed within the Pohorje Mountains (Slovenia). LA-ICP-MS zircon U–Pb ages of two samples of the augen-gneisses are 255 ± 2.2 Ma and 260 ± 0.81 Ma, which are interpreted as the age of magmatic crystallization of zircon. In contrast, all round zircons from leucogneisses give Cretaceous ages (89.3 ± 0.7 Ma and 90.8 ± 1.2 Ma), considered as the age of UHP/HP metamorphism. The round zircons overgrew older euhedral zircons of Permian and rare older ages tentatively indicating that these rocks are of latest Permian age, too. Zircon εHf(t) values of the four orthogneiss samples are between − 13.7 and − 1.7 with an initial 176Hf/177Hf ratio ranging from 0.282201 to 0.282562; T DM C is Proterozoic. The augen-gneisses show geochemical features, e.g. high (La/Lu)N ratios and strong negative Eu anomalies, of an evolved granitic magma derived from continental crust. The leucogneisses are more heterogeneously composed and are granitic to granodioritic in composition and associated with eclogites and ultramafic cumulates of oceanic affinity. We argue that the Permian granitic orthogneisses might be derived from partial melting of lower crust in a rift zone. We consider, therefore, that segment of the EGU is part of the distal Late Permian rift zone, which finally led to the opening of the Meliata Ocean during Middle Triassic times. If true, the new data also imply that the Permian stretched continental crust was potentially not much wider than ca. 100 km, was subducted and then rapidly exhumed during early Late Cretaceous times.

Quaternary of the Bengal Coast

2018 ◽  
pp. 12-18
Author(s):  
Rupendra Kumar Chattopadhyay
Keyword(s):  
Continental Crust ◽  
East Coast ◽  
Great Depth ◽  
The Other ◽  
Bengal Basin ◽  
Narrow Part ◽  
Delta Formation ◽  
Major Section

The second chapter is about the Quaternary of the east coast in India in general and the Bengal coast in particular. This discussion on the Quaternary is crucial in the context of the evolution of settlements not only along the coastal line but also its immediate hinterland areas. It is well known that the Orissa–Bengal coastline is formed over a deep tectonic trough underlain at a great depth by the older rocks of the continental crust. Here, an attempt has been made to explain the processes responsible for shaping this narrow part of the coastline and how they are different from those along the other part/parts of the east coast. A major section of this chapter is devoted to how the Quaternary processes related to the Bhagirathi–Hooghly/Gangetic delta formation have influenced the development of the present-day serrated coastline of the Bengal Basin.

Synthesis of Garnet/Perovskite-Based Ceramic for the Immobilization of Pu-Residue Wastes

1999 ◽  
Vol 556 ◽  
Author(s):  
B. E. Burakov ◽  
E. B. Anderson ◽  
D. A. Knecht ◽  
M. A. Zamoryanskaya ◽  
E. E. Strykanova ◽  
...  
Keyword(s):  
Perovskite Phase ◽  
Direct Conversion ◽  
Garnet Phase ◽  
Al Content ◽  
Ceramic Samples ◽  
Impurity Elements ◽  
Formula Type ◽  
Perovskite Lattice ◽  
Ga Content ◽  
Perovskite Ceramic

AbstractThe use of garnet/perovskite-based ceramic, with formula type (Y, Gd,..) 3(AI, Ga,..) 5O12 12/(Y, Gd,..)(A1, Ga,..)O3, was tested for immobilizing plutonium residue wastes. Pu residue wastes originate from nuclear weapons production and can contain more than 50% of impurities including such elements as Am, Al, Mg, Ga, Fe, K, La, Na, Mo, Nd, Si, Ta, Ce, Ba, B, W, Zn, Zr, C and Cl. While for some of these residues, direct conversion to typical glass or ceramic forms may be difficult, ceramic forms based on durable actinide host-phases are preferred for Pu, Am and other actinides immobilization. Garnet/perovskite crystalline host-phases are chemically and mechanically durable and desirable for the incorporation of Pu and most of the impurity elements in the Pu residue wastes in the lattices of host-phases in the form of solid solutions. Experiments on the synthesis of garnet/perovskite ceramic samples were carried out using melting in air at temperatures from 1300°C (for samples doped with 10 wt.% Pu residue waste simulant) to 2000°C (for samples doped with 10 wt.% Ce or U). Samples were studied by XRD, SEM and cathodoluminescence techniques. It was found that the garnet phase can incorporate upto 6 wt.% Ce and up to 4.0-5.5 wt.% U, which is correlated with the increase of Ga content and decrease of Al content in the melt. In one of the features of the melt, the perovskite phase formation substitutes for the formation of garnet. The capacity of the perovskite lattice to accommodate Ce and U is higher than the capacity of garnet, reaching about 8 and 7 wt.%, respectively. It was shown that cathodoluminescence can be effectively used to determine the valence state of Ce and U, an important step to optimize the starting precursor preparation. Incase of U4+ in the melt, the charge-compensating elements (Sn2+, Ca2+...) are needed to successfully incorporate U in the garnet lattice.

scholarly journals Synthesis and Mechanical Testing of Calcium Aluminosilicoferrite Crystals with High Alumina Content

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 906 ◽  
Author(s):  
Roland Mežibrický ◽  
Tamás Csanádi ◽  
Gerlinde Habler ◽  
Mária Fröhlichová ◽  
Ján Dusza ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Iron Ore ◽  
Raw Materials ◽  
Alumina Content ◽  
High Alumina ◽  
Al Content ◽  
Cube Corner ◽  
Minor Influence ◽  
High Silica ◽  
Materials Used

Due to the gradual shift to less rich iron ores, the alumina content in the raw materials used for iron-making is progressively increasing, affecting the mineralogy and the properties of iron ore sinters. In this context, the effect of Al content on the mechanical properties of calcium aluminosilicoferrites Ca2(Ca,Mg,Fe)6(Fe,Si,Al)6O20 (SFCA), which is the most important bonding phase in iron ore sinters, is of particular interest. In this study, high-alumina calcium aluminosilicoferrites were synthesized and their mechanical properties were determined by nanoindentation using a cube-corner indenter. For synthesis, different raw materials were taken as proxies for the adhering layer in a sinter granule. Three mixtures were prepared, high-iron, high-silica, and high-alumina and heated in an alumina crucible, which was used to simulate the high-alumina nucleus in a granule. The different raw materials used for synthesis had only minor influence on the compositions of the synthesized ferrites. All ferrites showed similar mechanical behavior during indentation, indicating that neither the chemical nor the mechanical properties were affected by the different compositions of the adhering layer, when the sinter granule is dominated by a high-alumina nucleus. The crystallographic orientation of the tested grains had only minor influence on the results of the nanoindentation experiments.

Amorphous alumino-silicate materials in a Brazilian hydromorphic lateritic soil

Soil Research ◽  
2002 ◽  
Vol 40 (3) ◽  
pp. 465 ◽  
Author(s):  
Angélica F. Drummond C. Varajão ◽  
Robert J. Gilkes ◽  
Robert D. Hart
Keyword(s):  
Lateritic Soil ◽  
Soil Profiles ◽  
High Concentration ◽  
Atom Ratio ◽  
Amorphous Phases ◽  
Al Content ◽  
Transmission Electron ◽  
Bulk Chemical ◽  
Alumino Silicate ◽  
High Al Content

Two ancient lateritic soil profiles from Brazil that are now experiencing hydromorphic conditions were investigated by chemical extractions, X-ray diffraction, differential thermal and thermogravimetric analysis, and analytical transmission electron microscopy (ATEM) to identify if the hydromorphic conditions had affected soil minerals. The soils are composed of gibbsite and kaolinite with less quartz, anatase, goethite, pedogenic chlorite, and amorphous alumino-silicate phases. These last 2 constituents occur in the middle and upper horizons of both soil profiles, together with considerable amounts of organic carbon. Analytical TEM showed that the amorphous phases enveloped corroded gibbsite and kaolinite crystals and may indicate the transformation of these minerals to amorphous phases. The amorphous phases have a similar microfabric to that of allophane and ATEM analyses of the amorphous phases gave an Al/Si atom ratio that was always >2, and commonly about 10. These atom ratios are consistent with the bulk chemical results obtained using pyrophosphate, oxalate, and dithionite extractants, but not with the theoretical ratio for allophane. The Al/Si atom ratio of the amorphous phases was related to the Al content of the mineral enveloped by the amorphous phases, i.e. gibbsite or kaolinite. This association supports the interpretation that the amorphous phases formed from the crystalline minerals. The saturated condition of the profiles, together with the high concentration of organic matter in the upper horizons, favours dissolution of the original gibbsite and kaolinite in the laterite and their transformation to amorphous alumino-silicate phases with a high Al content.

scholarly journals Utilization of CFBC Fly Ash as a Binder to Produce In-Furnace Desulfurization Sorbent

2018 ◽  
Vol 10 (12) ◽  
pp. 4854 ◽  
Author(s):  
Chulseoung Baek ◽  
Junhyung Seo ◽  
Moonkwan Choi ◽  
Jinsang Cho ◽  
Jiwhan Ahn ◽  
...  
Keyword(s):  
Fly Ash ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Limestone Powder ◽  
Fluidized Bed Combustion ◽  
High Concentration ◽  
Cfbc Fly Ash ◽  
Desulfurization Efficiency ◽  
Free Cao

Circulating fluidized bed combustion (CFBC) power generation technology is known to efficiently reduce the emission of air pollutants, such as SO2 and NO2, from coal combustion. however, CFBC coal ash contains high contents of free CaO, making it difficult to recycle. This research has been conducted to find ways to use the self-hardening property of CFBC coal ash, one of its inherent characteristics. As part of these efforts, the present study intended to investigate the properties and desulfurization efficiency of Ca-based desulfurization sorbents using CFBC fly-ash as a binder. Limestone powder was mixed with CFBC fly-ash and Ca(OH)2 to fabricate desulfurization sorbents, and it generated hydrate of cement, including portlandite, ettringite, and calcium silicate, etc. The compressive strength of the desulfurization absorbent prepared by CFBC fly ash and Ca(OH)2 was 72–92% that of the desulfurized absorbent prepared by using general cement as a binder. These absorbents were then compared in terms of desulfurization efficiency using a high-temperature fluidized bed reactor. It was confirmed that the desulfurization absorbents fabricated using CFBC fly-ash as a binder achieved the best performance in terms of absorption time, which reflects the time taken for them to remove over 90% of high-concentration SO2 gas, and the conversion ratio, which refers to the ratio of CaO turning into CaSO4.

scholarly journals Multistage Fractional Crystallization in the Continental Arc Magmatic System: Constraints from the Appinites in Tengchong Block, Southeastern Extension of Tibet

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Shao-Wei Zhao ◽  
Chao Yang ◽  
Shao-Cong Lai ◽  
Xian-Zhi Pei ◽  
Zuo-Chen Li ◽  
...  
Keyword(s):  
Continental Crust ◽  
Fractional Crystallization ◽  
Primary Magma ◽  
Evolution Process ◽  
High Alumina ◽  
Isotopic Compositions ◽  
Continental Arc ◽  
Subduction Setting ◽  
Lower Crustal ◽  
Subducted Sediment

Abstract The petrogenesis and evolution process of continental arc magmatism provide insight into discovering the formation and differentiation of continental crust. Therefore, the geochemical, isotopic, and mineralogical analyses were conducted for coeval continental arc igneous rocks in the Tengchong Block to clarify their evolution process in the continental arc magmatic systems. The Middle Triassic appinites in the Tengchong Block, southeastern extension of Tibet, were generated at the subduction setting with zircon U-Pb age of ca. 243 Ma. The Nb/Yb, Zr/Yb, and Ta/Yb ratios along with depleted zircon Hf isotopic compositions indicate a source with an N-MORB affinity for the appinites. However, relatively enriched whole-rock Sr-Nd isotopic compositions with the characteristic of high Sr/Nd, Ba/Th, Th/La, and Th/Nd ratios suggest the source was metasomatized by ~2% subducted sediment-derived fluid. According to the REE ratios modeling, the primary magma of Nabang appinites was due to 5-10% partial melting of such metasomatized mantle source. The appinites are characterized by variable compositions, such as SiO2 contents of 47.82-61.74 wt.% and MgO of 10.61-2.61 wt.%, which resulted from the polybaric and multistage fractional crystallization of a slightly hydrous primary magma in a thick crust. At lower crustal pressures, clinopyroxene was the main fractionating phase, and at middle crustal pressures, amphibole+magnetite were the dominant fractionating phases; predominant plagioclase fractionation occurred at the magma emplacement level. This process could be an effective mechanism to induce the differentiation of continental crust. The fractionation of clinopyroxene and amphibole, accompanied by suppressing plagioclase at lower-middle crustal pressures, induces the high alumina in the evolved melt and forms high-alumina basaltic to andesitic magma.

The Broad Applications of the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 20-21
Author(s):  
C. T. Nightingale ◽  
S. E. Summers ◽  
T. P. Turnbull
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Surface Topography ◽  
Great Depth ◽  
Resolving Power ◽  
Depth Of Field ◽  
Pictorial Representations ◽  
Scanning Electron

The ease of operation of the scanning electron microscope has insured its wide application in medicine and industry. The micrographs are pictorial representations of surface topography obtained directly from the specimen. The need to replicate is eliminated. The great depth of field and the high resolving power provide far more information than light microscopy.

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