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861.
In order to evaluate analytically the ITZ volume fraction (fITZ) in concrete, a three phase model is proposed for the random concrete microstructure using the Voronoï tessellation. Within this model, the ITZ local thickness is a statistical variable depending on the local paste thickness available between each couple of neighbouring aggregates. The fITZ is found to not exceed 7% for typical concretes. Then, the concrete Young's modulus is predicted analytically using a four‐phase generalized self consistent model but in which the proposed fITZ is considered. It is found that the concrete Young's modulus increases when increasing aggregates volume fraction, aggregates maximum size and the proportion of coarse aggregates and when decreasing the ITZ thickness and Young's modulus. Finally, the validity of the proposed model is discussed based on a comparison between its predictions and three sets of experimental results related to normal and high strength concretes taken from literature. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
862.
E. N. Slyuta V. S. Petrov O. I. Yakovlev S. A. Voropaev I. S. Monakhov T. V. Prokof’eva 《Geochemistry International》2017,55(1):27-37
In this paper, we report experimental data on the implantation of hydrogen ions of different energies into crystalline quartz samples. It was shown that irradiation with protons with an energy of 20 keV produces an amorphous film on the surface of a quartz sample, and irradiation with 90-keV protons results in the formation of a layer with interstitial defects and an increase in the unit-cell parameter of quartz with preservation of the crystal structure of the disturbed layer. The examination of the samples by thermodesorption mass spectrometry showed that high-energy irradiation resulted also in loosening of the surface layer and considerable expansion of high-potential adsorption sites, which was the reason for the observed peak desorption of gases. The existence of desorption peaks allowed us to calculate the activation energy of surface desorption of gas components. It was also found that an increase in irradiation energy tends to enhance the total degassing of samples. 相似文献
863.
S. I. Demidova M. A. Nazarov K. M. Ryazantsev M. O. Anosova T. Ntaflos F. Brandstätter 《Petrology》2017,25(2):139-149
Dhofar 025 is a lunar highland breccia consisting mainly of anorthositic, with less common noritic, gabbronoritic, and troctolitic material. Rare fragments of low-Ti basalts are present as well, but no KREEP (component enriched in incompatible elements) was found in the meteorite. The cathodoluminescence study of this meteorite showed that its impact–melt matrix contains unusual cathodoluminescent (CL) objects of feldspathic composition, which frequently contain microlites of Fe-Mg spinel (pleonaste). They were presumably formed by impact mixing and melting of olivine and plagioclase with subsequent rapid quenching of the impact melts. Such mixing could happen either during assimilation of anorthosites by picritic/troctolitic magmas or during impact melting of troctolites. The enrichment of CL objects of Dhofar 025 in incompatible trace elements suggests that the mafic component of the impact mixture may be related to the high-magnesium suite rocks, which are frequently enriched in KREEP component. The depletion of CL objects in alkalis indicates their possible relation with residual glasses formed by evaporation. However, the presence of FeO in most objects points to the insignificant extent of evaporation. Thus, evaporation cannot explain the enrichment of the CL objects in Al2O3 and other refractory components, although this process definitely took place in their formation. Their similarity to the lunar pink spinel anorthosites, whose existence was predicted from orbital data, serves as an argument in support of the possible formation of the latters by impact mixing. 相似文献
864.
Reactions and partial melting of peraluminous rocks in the presence of H2O-CO2–salt fluids under parameters of granulite-facies metamorphism were modeled in experiments on interaction between orthopyroxene–cordierite–biotite–plagioclase–quartz metapelite with H2O, H2O-CO2, H2O-CO2-NaCl, and H2O-CO2-KCl fluids at 600 MPa and 850°C. Rock melting in the presence of H2O and equimolar H2O-CO2 fluids generates peraluminous (A/CNK1 > 1.1) melts whose composition corresponds to magnesian calcic or calc–alkaline S-type granitoids. The melts are associated with peritectic phases: magnesian spinel and orthopyroxene containing up to 9 wt % Al2O3. In the presence of H2O-CO2-NaCl fluid, cordierite and orthopyroxene are replaced by the association of K-Na biotite, Na-bearing gedrite, spinel, and albite. The Na2O concentrations in the biotite and gedrite are functions of the NaCl concentrations in the starting fluid. Fluids of the composition H2O-CO2-KCl induce cordierite replacement by biotite with corundum and spinel and by these phases in association with potassium feldspar at X KCl = 0.02 in the fluid. When replaced by these phases, cordierite is excluded from the melting reactions, and the overall melting of the metapelite is controlled by peritectic reactions of biotite and orthopyroxene with plagioclase and quartz. These reactions produce such minerals atypical of metapelites as Ca-Na amphibole and clinopyroxene. The compositions of melts derived in the presence of salt-bearing fluids are shifted toward the region with A/CNK < 1.1, as is typical of so-called peraluminous granites of type I. An increase in the concentrations of salts in the fluids leads to depletion of the melts in Al2O3 and CaO and enrichment in alkalis. These relations suggest that the protoliths of I-type peraluminous granites might have been metapelites that were melted when interacting with H2O-CO2-salt fluids. The compositions of the melts can evolve from those with A/CNK > 1.1 (typical of S-type granites) toward those with A/CNK = 1.0–1.1 in response to an increase in the concentrations of alkali salts in the fluids within a few mole percent. Our experiments demonstrate that the origin of new mineral assemblages in metapelite in equilibrium with H2O-CO2-salt fluids is controlled by the activities of alkaline components, while the H2O and CO2 activities play subordinate roles. This conclusion is consistent with the results obtained by simulating metapelite mineral assemblages by Gibbs free energy minimization (using the PERPE_X software), as shown in log(\({a_{{H_2}O}}\))–log(\({a_{N{a_2}O}}\)) and log(\({a_{{H_2}O}}\))–log(\({a_{{K_2}O}}\)) diagrams. 相似文献
865.
A. V. Stepanova V. S. Stepanov A. N. Larionov P. Ya. Azimov S. V. Egorova Yu. O. Larionova 《Petrology》2017,25(6):566-591
The Vorochistoozersky, Nizhnepopovsky, and Severo-Pezhostrovsky gabbro-anorthosite massifs have been studied in the central part of the Belomorian Province, Fennoscandian Shield. The similarity of geological setting and rock composition of these massifs suggests their affiliation to a single complex. The age of the gabbro-anorthosites was determined by U-Pb (SHRIMP II) zircon dating of gabbro-pegmatites from the Vorochistoozersky massif at 2505 ± 8 Ma. The studied massifs were overprinted by the high-pressure amphibolite facies metamorphism. Relicts of magmatic layering and primary magmatic assemblages preserved in the largest bodies. The massifs consist mainly of leucocratic gabbros but also contain rocks of the layered series varying in composition from olivinite to anorthosite. The presence of troctolites in the layered series indicates the stability of the olivine–plagioclase liquidus assemblage and, respectively, shallow depths of melt crystallization. Despite the composition differences between gabbro-anorthosites of the Belomorian and peridotite–gabbronorite intrusions Kola provinces, these simultaneously formed massifs presumably mark a single great igneous event. It also includes the gabbronorite dikes in the Vodlozero terrane of the Karelian province, the Mistassini swarm in the Superior province, and the Kaminak swarm in the Hearne Craton, Canadian Shield. The large igneous province of age ~2500 Ma reflects the oldest stage of within-plate magmatism after a consolidation of the Neoarchean crust of the Kenorland Supercontinent (Superia supercraton). 相似文献
866.
O. V. Postnikova A. V. Postnikov E. S. Konoval’tseva V. G. Toporkov S. I. Savchenko 《Lithology and Mineral Resources》2011,46(5):447-456
Basic regularities of secondary processes in reservoir rocks of the Yarakta Horizon are described with rocks in the Yarakta
field as example. To achieve the formulated goal, we elucidated rock types in the studied section, its structure and distribution
of reservoir rocks, as well as types of secondary alterations and their influence on filtration-capacity properties. The studies
revealed that reservoir rocks of the Yarakta Horizon were formed on an alluvial-deltaic plain on the southeastern slope of
the Nepa-Botuoba anteclise. The pore space of reservoir rocks is determined by conditions of their formation and peculiarities
of secondary alterations. Maximal filtration-capacity values are characteristic of gritstones, as well as coarse-grained and
inequigranular sandstones developed in the lower and middle parts of the Yarakta Horizon. The intergranular space of reservoir
rocks in the lower part of the reservoir is substantially “healed” by secondary processes (regeneration, dolomitization, sulfatization,
and salinization), probably, due to the gravitational seepage of stratal fluids, mineralization of which increased with time. 相似文献
867.
O. A. Korchagin 《Stratigraphy and Geological Correlation》2011,19(5):526-544
The first data on the taxonomic composition and stratigraphic range of the late Campanian planktonic foraminifers encountered
in the middle and upper parts of the Moni Formation, southern Cyprus, are reported. Finds of planktonic foraminifers are associated
with the bentonitic clay that composes the matrix of the Moni Formation. The planktonic foraminiferal assemblages revealed
are very similar to those from the Kannaviou Formation, western Cyprus, but they are more diverse and yield several key species
missing in the Kannaviou sediments. The planktonic foraminiferal assemblages discussed are referred to the Globotruncana aegyptiaca Zone and to the lowermost Gansserina gansseri Zone of the upper upper Campanian of the standard scale. The intraregional correlation of the Moni sections, depth of erosion
of the upper part of the formation, and its relationship with the Kannaviou Formation have been refined. When subdividing
the upper Campanian sediments based on planktonic foraminifers it is suggested that additional datum planes are used, such
as the FADs of Globotruncanella citae and Trinitella scotti. For tracing the Campanian-Maastrichtian boundary (GSSP), attention should be paid to the LADs of Globotruncana bulloides and Contusotruncana fornicata and the potential use of Globotruncanita (Elevatotruncana) eolita sp. nov. should be assessed. It is shown that subfamily Archaeoglobigerininae Salaj, 1987, emend. O. Korchagin is the older
synonym of subfamily Archaeoglobigerininae Georgescu, 2005. Two poorly known and three new planktonic foraminiferal species
are described. 相似文献
868.
869.
V. V. Balagansky N. L. Alexejev H. Huhma P. Ya. Azimov L. K. Levsky L. O. Pin’kova 《Stratigraphy and Geological Correlation》2011,19(4):369-384
This paper presents the results of a study of the Paleoproterozoic basal garnet-kyanite-staurolite-two-mica paraschists from
the Kukasozero structure of the Karelides of Northern Karelia, Baltic Shield, underlying Neoarchean acid metavolcanic rocks,
and schists with quartz, phengite, kyanite, staurolite, garnet, and tschermakite located in the Paleoproterozoic rocks and
considered to be metasomatic in origin. It was established that the sedimentary protolith of the Paleoproterozoic paraschists
contains detritus of Neoarchean igneous rocks as follows from detrital 2737 ± 11 Ma zircons with oscillatory magmatic zoning.
Metavolcanic 2757 ± 13 Ma rocks, close in age and composition, are known directly in the framework of the Kukasozero structure
and are considered to be the most likely source of the sedimentary schist protolith. The coincidence of the Nd-model ages
of paraschists (t
DM is 2.73–2.76 Ga) with the age of detrital zircons indicates no contribution of older rocks to the protolith composition.
The age of magmatic crystallization of metavolcanic rocks directly underlying the Paleoproterozoic paraschists is 2681 ± 18
Ma and coincides with the age of porphyry granites in the western framework of the structure (2680.3 ± 3.6 Ma). No detrital
zircons of similar age were found in basal paraschists, but the restricted amount of dated zircons does not allow us to draw
a final conclusion about the absence of detritus of the underlying metavolcanic rocks in the paraschist protolith. It was
confirmed that phengite-bearing schists are the products of acid metasomatism of the Paleoproterozoic amphibolites and amphibole
schists (metavolcanic rocks). The metasomatic features were revealed in garnet-kyanite-staurolite-two-mica paraschists, so
the strict identification of their sedimentary protolith is impossible. The paraschists do not represent metamorphosed weathering
crust, because acid metasomatism gives a false impression of the greater maturity of the primary sedimentary rocks. 相似文献
870.