Fine-grained Matrix Research Articles

Hot deformation behavior of Cu–Ni–Si alloy at elevated temperature

Hot compression tests of Cu–Ni–Si alloy with high Ni and Si contents were carried out on Gleeble-3800 thermal simulator in the deformation temperature of 750 °C ∼ 950 °C, strain rate of 0.01 ∼ 10 s−1 and deformation amount of 70%. Subsequently, constitutive equation based on Arrhenius-type constitutive model considering strain effect was established, and the average absolute relative error and correlation coefficient R were 7.34% and 0.991. Then, hot Processing map was obtained by combining the power dissipation and instability maps, and the suitable processing conditions could be predicted. Based on the results of these experimental and theoretical investigations on the hot deformation behavior of Cu–Ni–Si alloys, Multi-direction compression (MDC) was carried out at 860 °C and corresponding strain of single pass and accumulated 24 passes 0.4 and 9.6 respectively. The resulted microstructure consisted of fine matrix grains with a diameter of 3.02 μm and well dispersed Ni31Si12 particles 0.62 μm, suggesting that the results of thermal simulator and corresponding calculation were credible for guiding the thermo-mechanical processing parameters of Cu–Ni–Si alloys.

Occurrence of albitite from Capo Malfatano, SW Sardinia: first report, characterization from mineralogy and whole-rock geochemistry

Within the sedimentary-volcanoclastic succession known as Bithia Unit (SW Sardinia) a decameter-wide albitite lens has been found and is here characterized from a geological, petrographic and geochemical point of view. Albitite is a yellowish, fine-grained body elongated and foliated according to the main schistosity of the hosting rocks (N20-25° - 40° NW). The rock is made up by plagioclase porphyroclasts in a fine-grained matrix of plagioclase (up to 80%) and quartz; both porphyroclasts and small grains in matrix are almost pure albite (Ab 98 ). Accessory phases are ilmenite, rutile, monazite, apatite and zircon. Bulk-rock chemical analyses show that the relative proportions of SiO 2 , Al 2 O 3 and Na 2 O strongly resemble those of pure albite. Major, trace and rare earth element (REE) contents strongly suggest geochemical affinity with the nearby Ordovician metavolcanics and orthogneiss from Capo Malfatano area described in literature. Furthermore, REE, Rb/Sr, Y/Ho and Zr/Hf ratios seem to exclude the involvement of a significant Na-rich fluid metasomatism.

Organic geochemical characteristics and depositional setting of Paleogene oil shale, mudstone and sandstone from onshore Penyu Basin, Chenor, Pahang, Malaysia

The eastern Chenor Pahang area of the Penyu Basin contains an untapped potential, in part due to poor knowledge of its organic facies characteristics The sedimentary succession of eastern Chenor Pahang area is dominated by fine to coarse grained sandstone occurring in association with oil shale and mudstone in a predominantly fining upward sequence. Detailed geochemical and petrographic characterization was carried out on oil shale and mudstone samples to evaluate the origin and type of organic matter (OM), as well as the paleoenvironmental conditions and organic richness of the Paleogene sedimentary succession. The facies are only enriched in total organic carbon (TOC), potential hydrocarbon yield (S2) and extractible organic matter (EOM) the types of organic matter are important index reflecting the potential of the source rock(s). Based on elemental ratios, the analyzed samples are shown to contain Types I and II kerogens. This finding is supported by the high hydrogen index (HI) of >300 mg HC/g TOC and the presence of abundant liptinitic materials. Biomarker signatures [n-alkanes >n-C25, high C29/C30 17α (H) hopane ratios (0.8–3.3) and high C29 steranes (49–78%)]. Low total sulfur and V/(V + Ni) ratio] suggest a predominantly terrestrial source input with some contribution from aquatic microorganisms as indicated by the common occurrence of amorphous organic matter. Combining this results with n-alkane patterns, kerogen types and organic petrography, predominance of C29 sterane probably indicates a contribution of aquatic organisms such as green and brown algae (consistent with Botrycoccus braunii race A and Pediastrum contribution) and some influence of higher plants OM. Integration of biomarker studies with bulk geochemical and petrographic analysis suggests that the analyzed samples were deposited under suboxic conditions in a fresh water lacustrine environment. This finding is corroborated by the ratios of pristane/phytane, V/Ni and Sr/Br. High bioproductivity and a stratified fresh water column with suboxic bottom water condition enhanced OM preservation in the analyzed mudstone and shale facies. The high OM content in these samples maybe related to the fine-grained matrix of the mud rocks and the paleoclimate in the area.

Mineral textures of olivine minette and their significance for crystallization history of parental magma; an example from the Moldanubian Zone (the Bohemian Massif)

One of the best-preserved dykes of olivine minette among the lamprophyre dyke swarm in the Moldanubian Zone of the Bohemian Massif (Czech Republic) was investigated. The minette, exposed at Horni Kožli Village (near Prachatice town), has porphyric texture with phenocrysts of olivine, clinopyroxene, orthopyroxene and biotite in a fine-grained matrix consisting of K-feldspar, biotite, clinopyroxene and minor plagioclase and quartz. Accessory minerals are apatite, Cr-rich spinel and iron sulphides. Olivine is mostly replaced by talc and rimmed by two zones (coronas) – a talc-rich inner zone and a biotite-rich outer zone. Rarely, larger grains of quartz with a corona of clinopyroxene are present. The clinopyroxene grows mostly perpendicular to the quartz rim and radially penetrates the quartz crystal. Three stages of mineral crystallization were distinguished. The first stage with apatite, olivine, biotite, spinel, orthopyroxene and part of the clinopyroxene occurred in the mantle position. During the second stage, felsic phases (K-feldspar, plagioclase, quartz) in the matrix were crystallized. The enrichment of the residual melt by silica and Na occurred as the result of both fractionation and contamination during magma ascent through the granulite facies crust during post-collision orogeny in the Bohemian Massif. Minerals related to the third stage were formed during filling of the vesicles (quartz with reaction rims of clinopyroxene) and subsequent alteration (talc after olivine). The origin of quartz with clinopyroxene reaction rims (‘quartz ocelli’) is explained by filling of cavities formed by the escape of volatiles.

Role of myrmekite and associated deformation fabrics in controlling development of granitic mylonites in the Pofadder Shear Zone of southern Namibia

Myrmekites developed within metagranites of the Pofadder Shear Zone (PSZ) in southern Namibia were investigated to understand how alkali feldspar deforms under fluid-poor mid-crustal conditions. Myrmekites showed two different morphologies: (1) ‘Wormy’ myrmekite with a fine-grained vermicular structure that occurred closest to the alkali feldspar host; and (2) ‘recrystallised’ myrmekite composed of regularly sized quartz grains that formed 120° boundaries with the plagioclase and occurred along the exterior of alkali feldspar and in contact with the mylonitic matrix. These textures were interpreted to represent two generations of myrmekite growth. Recrystallised myrmekite masses were dismembered and incorporated into the fine-grained matrix. This suggests that myrmekite formation during PSZ deformation contributed to the grain size reduction of alkali feldspar and aided in the generation of the fine-grained polymineralic matrix which accommodated most of the strain. Syn-kinematic reactions, such as myrmekite and muscovite production, were internally balanced and T–MH2O pseudosections indicated that progressive deformation could have occurred under closed conditions. The biotite–muscovite–plagioclase–alkali feldspar–quartz equilibrium assemblage was stable with decreasing fluid contents until fluid-saturated or slightly fluid-undersaturated conditions were reached around 2 mol% H2O. The variability of the quartz rod spacing and the wide range of results from two-feldspar thermometry and phengite barometry on associated muscovite growth indicates that peak metamorphic conditions were around 500 °C, 0.5 GPa and that myrmekite growth continued as the shear zone was exhumed. The myrmekite-forming reaction is a deformation-induced interface-coupled dissolution–precipitation reaction with relict magmatic plagioclase supplying the needed cationic inputs. These results indicate that deformation within granitic units of the PSZ was aided by the formation and deformation of myrmekite and could have taken place under closed relatively fluid-poor conditions.

Nanoscale infrared imaging analysis of carbonaceous chondrites to understand organic-mineral interactions during aqueous alteration

Organic matter in carbonaceous chondrites is distributed in fine-grained matrix. To understand pre- and postaccretion history of organic matter and its association with surrounding minerals, microscopic techniques are mandatory. Infrared (IR) spectroscopy is a useful technique, but the spatial resolution of IR is limited to a few micrometers, due to the diffraction limit. In this study, we applied the high spatial resolution IR imaging method to CM2 carbonaceous chondrites Murchison and Bells, which is based on an atomic force microscopy (AFM) with its tip detecting thermal expansion of a sample resulting from absorption of infrared radiation. We confirmed that this technique permits ∼30 nm spatial resolution organic analysis for the meteorite samples. The IR imaging results are consistent with the previously reported association of organic matter and phyllosilicates, but our results are at much higher spatial resolution. This observation of heterogeneous distributions of the functional groups of organic matter revealed its association with minerals at ∼30 nm spatial resolution in meteorite samples by IR spectroscopy.

Superior strength and ductility of 1045 steel with heterogeneous composite structure

The effects of low temperature annealing on the microstructure and mechanical properties of cold rolled 1045 steel were investigated. It was found that the isothermal annealing at 673 K could transform cementite in the rolled steel from lamella to nano-crystalline state. Against the conventional theory, the low temperature annealing treatment could simultaneously enhance the tensile strength and ductility of the cold rolled steel. The underlying mechanisms of enhancing mechanical properties were analyzed, with a focus on the heterogeneous composite structure of a soft fine-grained matrix embedded with hard nano-scale cementite particles.

Emission Properties of Metal Porous Cathodes Modified by Nanocarbon

The results of studying the emissive ability, structure, and elemental composition of the surface of an impregnated cathode with a fine-grained tungsten matrix with addition of polyhedral multilayer carbon nanostructures of the fulleroid type (0.2−0.7 wt %), impregnated with barium-calcium aluminate with addition of sulfoadduct of carbon nanoclusters (0.1−0.2 wt %), are presented. The tests in diode prototypes showed that these cathodes provide a current density of 20 A/cm2.

Aqueous alteration of porous microchondrules in Semarkona: Implications for hydration, oxidation and elemental exchange processes

Porous, igneous glassy microchondrules are relatively common in Semarkona and other unequilibrated ordinary chondrites (UOC), occurring embedded within the fine-grained matrices and the chondrule rims. We have investigated the effects of aqueous alteration on two porous microchondrules and associated amorphous silicate materials in the fine-grained matrix of the Semarkona (LL3.00) ordinary chondrite. The iron valency was measured by synchrotron-based scanning transmission X-ray microscopy (STXM) and detailed compositional and mineralogical data were obtained by transmission electron microscopy (TEM). Our STXM data show that the iron in both microchondrules and the amorphous matrix materials is highly oxidized, with elevated ferric iron contents (up to Fe3+/∑Fe ratio 81%). The oxidation process appears to be the result of the interaction of aqueous fluids produced by melting of water ice that accreted into the LL chondrite parent body. The lack of secondary phases such as phyllosilicates or FeO-rich olivines in the microchondrules and the surrounding fine-grained matrix indicates that aqueous alteration was extremely limited. The distribution of major and minor elements indicates limited elemental exchange between the porous microchondrules and the adjacent fine-grained matrix, suggesting that the chemical composition of the two porous microchondrules was not extensively modified during the aqueous alteration. Therefore, these results strongly support the recent conclusions that porous and nonporous microchondrules have different precursor compositions, since their bulk compositions are different and have not been extensively modified by secondary processes.

Spectral and chemical effects of simulated space weathering of the Murchison CM2 carbonaceous chondrite

We performed pulsed-laser irradiation of a chip of the CM2 Murchison carbonaceous chondrite meteorite to simulate micrometeorite impacts on carbonaceous asteroids. Optical reflectance spectroscopy and transmission electron microscopy were performed to characterize the unirradiated and irradiated samples and vapor and melt deposits collected on a glass slide ∼7 mm from the surface of the sample. The spectrum of the deposit on the glass slide shows a red slope between 0.35–2.5 µm, while the irradiated surface of the meteorite shows only slight darkening over the same spectral range. We identified predominant melt products and vesiculated textures in the glass slide deposit, in the fine-grained matrix of the meteorite, and in individual mineral phases of the meteorite chip. Extracted focused ion beam (FIB) sections from the matrix material, an olivine grain, a pentlandite grain, and from the glass slide deposit were analyzed by scanning transmission electron microscopy (STEM). Microstructural and chemical analyses based on the STEM observations show widespread melting and the formation of Fe-bearing nanoparticles (including prevalent Fe–Ni–sulfides) across the surface of the meteorite. The section extracted from the glass slide revealed nanoparticles embedded in a chemically and microstructurally complex deposit, which likely formed as a result of both melting and vaporization processes. These analyses reveal a significantly more compositionally diverse population of nanoparticles compared to what is observed in lunar or ordinary chondritic space weathered samples. We discuss the implications these results have for the space weathering of carbonaceous asteroids and their importance for understanding the surface processes on primitive bodies.

Puzzling micro-relief (mounds) of a soft-bottomed, semi-enclosed shallow marine environment

A dataset comprising geomorphological information (side-scan sonar, bathymetry, samples, drop camera, scuba diving, and a limited number of subbottom profiles) revealed a large number of low-relief buildups occupying almost half of the Gulf of Gera, a shallow land-locked environment. They probably represent mud mounds constructed of biogenic fragments and benthic assemblages consisting mainly of mollusks in a fine-grained matrix, and they are confined to the central part of the gulf. According to their morphometric characteristics and surface distribution, the mounds were separated into three subtypes with the highest (up to 2.5 m), larger coalescing features occurring close to the gulf entrance, whereas the smaller and more circular features appear in an elongated zone at the center of the gulf. This configuration coincides with the gulf’s circulation pattern that disperses and transports nutrients and fine-grained material. The high-resolution subbottom profiles, acquired in a restricted zone of the southeastern gulf, have shown the presence of paleo-mound surfaces in the Holocene highstand surface layer and fluids in the underlying sediments. Similar formations have been rarely reported in the literature, and those other reports are from different environmental settings. Consistent with the literature, they are probably developed due to the interplay of physical and biological processes. However, only an interdisciplinary study could shed light on the specific processes that drive their formation and their unique distribution pattern in the specific environment of the Gulf of Gera.

Pore-throat characteristics of tight sandstone reservoirs composed of gravity flow sediments: Yingcheng Formation, Longfengshan sag, China

The Lower Cretaceous Yingcheng Formation in the Longfengshan sag (Songliao Basin, China) represents a typical tight sandstone reservoir that hosts large accumulations of hydrocarbons. The lacustrine sandstones mainly reflect gravity flow deposits making up various lithofacies displaying varying degrees of heterogeneity. This study reports on the links among gravity flow type, diagenetic overprinting and pore-throat characteristics that control reservoir quality. Core observations, especially grain size variations and related sedimentary structures are used to differentiate types of gravity flows. Microscopic observations, cathodoluminescence, scanning electron microscopy, pressure-controlled mercury injection tests and rate-controlled mercury injection tests are used to determine the mineralogy, sedimentary composition and pore-throat characteristics of the tight sandstones.In the study area, the gravity flows are divided into muddy debris flows, sandy debris flows, high-density turbidity flows, low-density turbidity flows and mud density flows. The petrophysical properties of these different gravity flow sediments reflect a range of permeability and porosity characteristics. Because of their mud-dominated textures and related weak compressive strength, mud density flows and muddy debris flows become ineffective as reservoirs during burial. In contrast, for approximately similar burial depths, turbidites and sandy debris flows show better reservoir quality. However, reservoir units with high porosities still possess considerable heterogeneity; this is especially true of some sandy debris flows that possess large amounts of secondary pores but which are not charged with hydrocarbons. In particular, in some poorly sorted sandy debris flows that are characterized by high contents of fine-grained matrix, some of the pore throats are blocked by matrix material. Moreover, the dissolution of feldspars and volcanic debris led to the formation of authigenic clays and quartz, which preferentially developed in pore throats with small radii. This process significantly reduced permeability.Overall, the permeabilities of the sandy debris flows are generally lower than those of the turbidites. Due to their relatively large-radius pore throats, turbidites can be categorized as potential effective hydrocarbon reservoirs in the study area. This research provides significant insights into the characteristics of pore throats within tight reservoirs consisting of gravity flow sediments in lacustrine basinal settings.

Lithic artifacts and bone tools from the Lower Palaeolithic site Marathousa 1, Megalopolis, Greece: Preliminary results

The technological systems and subsistence strategies of Middle Pleistocene hominins in South-East Europe are insufficiently understood due to the scarcity of well-preserved, excavated assemblages. In this paper, we present first results from the study of the lithic and bone artifacts unearthed at the Lower Palaeolithic site Marathousa 1 (MAR-1), Megalopolis, Greece. The context of the site represents a depositional environment close to a lakeshore, where rapid burial in a very fine-grained matrix ensured extraordinary conditions for preservation. Lithic artifacts occur in spatial and stratigraphic association with remains of the elephant Palaeoloxodon antiquus as well as other mammals. Bones, including those of elephants, show clear anthropogenic flaking scars, cut-marks and fracture patterns indicating deliberate breakage and modification by early humans. The MAR-1 lithic assemblage is composed of small-sized debitage, retouched tools, a few small and exhausted cores, as well as a large number of debris and retouch products, such as chips and resharpening flakes. Currently, there are no indications of Acheulean bifacial debitage, large cutting tools are missing, and a key aspect of the material refers to its 'microlithic' character. The scarcity of cores and primary flakes indicates a fragmented reduction sequence and complex discard patterns that require further investigation. On the basis of the on-going analysis of lithic material from three field seasons, we discuss aspects of assemblage composition and the role of raw material types, the main technological and typological traits of the industry, as well as the potential contribution of the MAR-1 assemblage in broader discussions about Middle Pleistocene lithic techno-complexes and subsistence strategies in Eurasia. Finally, we briefly present a small sample of bone artifacts, which suggest that hominin exploitation of the animal carcasses was not restricted to marrow extraction and bone processing for nutritional needs, but included also the knapping of bones, potentially with the aim of using the knapped products as tools. The MAR-1 archaeological record compares well with other important Eurasian sites yielding ‘small tool assemblages’, such as Ficoncella, La Polledrara, Bilzingsleben, Schöningen and Vértesszőlős, some of which, like MAR-1, have provided evidence of elephant or other mega-fauna exploitation.

Flow stress and deformation behavior of fine-grained Mg matrix influenced by bimodal size SiCp

Abstract

Strengthening of Al-Fe3Al composites by the generation of harmonic structures

Strengthening of alloys can be efficiently attained by the creation of harmonic structures: bimodal microstructures generated by controlled milling of the particulate precursors, which consist of coarse-grained cores embedded in a continuous fine-grained matrix. Here, we extend the concept of harmonic structures to metal matrix composites and analyze the effectiveness of such bimodal microstructures for strengthening composites consisting of a pure Al matrix reinforced with Fe3Al particles. Preferential microstructural refinement limited to the surface of the particles, where the Fe3Al phase is progressively fragmented, occurs during ball milling of the Al-Fe3Al composite powder mixtures. The refined surface becomes the continuous fine-grained matrix that encloses macro-regions with coarser reinforcing particles in the harmonic composites synthesized during subsequent powder consolidation. The generation of the bimodal microstructure has a significant influence on the strength of the harmonic composites, which exceeds that of the conventional material by a factor of 2 while retaining considerable plastic deformation. Finally, modeling of the mechanical properties indicates that the strength of the harmonic composites can be accurately described by taking into account both the volume fraction of reinforcement and the characteristic microstructural features describing the harmonic structure.

Pathways of phase transformation in β-phase-stabilized σ/γ-TiAl alloys subjected to two-step heat treatments

In order to increase the maximum service temperature of intermetallic TiAl materials novel alloy and microstructure concepts are required. Thus, this study focuses on so-called σ/γ-TiAl materials alloyed with β-stabilizing elements Cr and Mo. These alloys in principle show improved mechanical capabilities, but their microstructure control necessitates judicious design of composition and heat treatment parameters. In this work the effects of the alloying elements Cr and Mo are elucidated. The presence of these elements retards the formation of γ- and σ-phases due to diffusional redistribution required, thereby, allowing for the formation of a fine-grained matrix with an embedded particle structure.

Technology features of decellularization of human liver fragments as tissue-specific fine-grained matrix for cell-engineering liver construction

One of the problems when you create a bioengineered liver, as an alternative to transplantation of the donor liver in the treatment of end-stage liver failure, is the matrix, able to temporarily perform the functions of the natural extracellular matrix (ECM) and provide the necessary conditions to maintain the viability of the liver cells. The main disadvantage of resorbable biopolymer matrices is the absence of tissue specifi c properties and the impossibility of reproducing the unique structure of the ECM of the liver.Aim:to develop technology for decellularization of liver tissue fragments, saving the structural properties of native ECM of the liver.Materials and methods.The decellularization of mechanically grinded human liver fragments was carried out in three changes of buffer solution (pH = 7.4) containing 0.1% sodium dodecyl sulfate and increasing the concentration of Triton X100 (1%, 2% and 3%, respectively). During technology development were investigated the effects of duration, conditions (static, dynamic, rotary system, magnetic stirrer) washing and methods of liver tissue grinding on the completeness of removal of cellular elements and detritus preserving the the liver ECM structure. Slices of decellularized liver tissue samples were stained by hematoxylin and eosin, and Masson method for the detection of connective-tissue elements.Results.Histological analysis methods showed that the best from the point of view of effi ciency of decellularization and the safety of the structure of own human liver ECM, is a mode of washing of liver fragments for three days at room temperature in static conditions, accompanied by stirring by a magnetic stirrer for 2–3 times a day for one hour. Longer time or a large multiplicity of mixing mode is accompanied by increased risk of liver tissue damage. On the basis of the experimental results obtained the algorithm of preliminary study of donor human liver designed to optimize the process of obtaining decellularization fragments of liver tissue was elaborated.Conclusion.It was elaborated the algorithm and technology of obtaining of decellularized liver tissue fragments from the human donor liver which saved the structural properties of native ECM of the liver and complete removal of cellular elements and detritus.

Microscopic characterization and formation mechanisms of deep-water sandy-debris-flow and turbidity-current sandstones in a lacustrine basin: a case study in the Yanchang Formation of the Ordos Basin, China

Deep-water deposition is a current issue in sedimentological research. Sandy-debris-flow sandstones and turbidity-current sandstones are the main types of sandstone that are the focus of considerable disputes in this research. Previous studies mainly focused on description of the macroscopic sedimentary structure and theoretical derivation of the formation mechanisms. The microscopic petrological characteristics, reservoir properties, and formation mechanisms of deep-water sandy-debris-flow and turbidity-current sandstones have been studied in the Yanchang Formation of the Ordos Basin, China, by means of field outcrop surveys, thin-section identification, geochemical element analysis, and porosity and permeability measurements under overburden pressure. The content of detrital grains in the sandy-debris-flow sandstones is high, whereas the contents of mica sheets and matrix are low. The fine-grained matrix is distributed unevenly within the pores. A considerable number of residual intergranular pores are preserved in the middle of single sand bodies, resulting in relatively better reservoir properties. The total number of detrital grains in the turbidite sandstone is low, while it contains abundant mica sheets and matrix. The mica sheets and fine-grained matrix are distributed evenly within the pores, resulting in serious damage to pores and poor reservoir properties. The sandy-debris-flow sandstones in the center of the lake basin form a high-quality reservoir; thus, this area is suitable for oil and gas exploration.

A dorozsmai márvány (Tiszai-főegység) kőzettani újravizsgálata: deformáció és fluidum hatása a mikroszerkezet fejlődésére

A márványok petrográfiai vizsgálata napjainkig alárendelt szerepet kapott a hazai földtani szakirodalomban. A márványt felépítő ásványfázisok, valamint azok szemcsemérete és a szemcsehatár jellegének meghatározása (kőzetszövet), illetve a deformációs bélyegek feltárása és értelmezése révén azonban átfogó képet kaphatunk a kőzet metamorf fejlődéséről és deformációtörténetéről, ami független bizonyítékokkal szolgálhat a befoglaló metamorf kőzettest korrelációjához.
 A Békés–Codrui-egységen belül elhelyezkedő, Dorozsma környéki kristályos aljzatban egy maximum néhányszor tíz méter vastagságú, markáns töréses deformációt szenvedett márványzóna található. Tanulmányunkban az e zónát mintázó Dorozsma‒4, ‒7 és ‒54 fúrások által feltárt márványból készült archív vékonycsiszolatok petrográfiai vizsgálatát végeztük el.
 A mikroszkópos vizsgálatok alapján a dorozsmai márvány döntően karbonát + kvarc + Mg-klorit ± talk összetételű, finomszemcsés, heteroblasztos szövetű márványból épül fel. A szemcsehatárok jellemzően szutúráltak, illetve beöblösödők, a deformációs ikerlemezek közül dominánsan a II. és a IV. típus van jelen. A mintákban általánosan jellemzők a kisméretű, kvarccal és karbonáttal kitöltött oldódásos üregek, amelyeket mikrokristályos karbonátból álló szegély övez. Erősen átalakult, mikrokristályos kőzetváltozat szintén megfigyelhető, valamint nagyméretű, szigmoid-alakú karbonátklasztok és rezorbeált, polikristályos, alszemcsés szerkezetű kvarcklasztok is megjelennek a mikrokristályos alapanyagban. Helyenként a nagyméretű karbonátszemcsék deformációs ikerlemezeit apró, kisméretű, zárványmentes karbonátszemcsék helyettesítik, amelyek a nagyméretű szemcsék között is megtalálhatók Mg-klorittal együtt.
 Az archív vékonycsiszolatok petrográfiai vizsgálata alapján kijelenthető, hogy a vizsgált márványt többfázisú deformáció érte. A D1 esemény a szöveti bélyegek alapján nagyobb, 250 ºC-ot meghaladó hőmérsékleten mehetett végbe, amelyet később felülbélyegzett egy kis hőmérsékletű deformációs esemény (D2), amelyhez fluidumhatás társult. E fluidum gyengítő hatása okozhatta a vékonycsiszolati léptékben felismerhető képlékény alakváltozást, valamint a kis hőmérsékletű dinamikus rekrisztallizációra utaló szöveti bélyegeket.

Bimodal Structures of Solids Obtained under Megaplastic Strain

The evolution of the defect structure of aluminum alloys of different compositions under megaplastic strain at a high quasi-hydrostatic pressure has been studied. The theoretical analysis and numerical calculation of the evolution of the defect structure of solids (metals) under this impact have been performed within the three-defect model of nonequilibrium evolution thermodynamics. The calculation of defect kinetics shows that the presence of coarse grains submerged into a matrix of fine grains at specified parameters and coefficients leads to the additional generation of dislocations and, as a consequence, to the greater dislocation strengthening of a material.