Microcracks in ultrabasic rocks under uniaxial compressive stress     

Ioannis Rigopoulos  Basilios Tsikouras  Panagiotis Pomonis  Konstantin Hatzipanagiotou 《Engineering Geology》2011,117(1-2):104-113

The initiation and propagation of microcracks under stress are highly dependent upon the mineralogical and textural characteristics of the various lithotypes. Detailed observation and quantification of microcracks before and after uniaxial compression test were conducted. A fresh olivine-rich harzburgite and a serpentinized dunite were analyzed, collected from the Pindos and Vourinos ophiolites (northern Greece) respectively, in order to compare their microcrack patterns. Quantitative analysis indicated that during uniaxial compression the intragranular microcracks, which are the dominating crack-type, are gradually transformed or organized into transgranular cracks. Some of the newly formed transgranular cracks may also be a result of the growth of existing grain-boundary cracks. The new intragranular microcracks in the olivine-rich harzburgite are oriented predominantly parallel to the compressive stress direction, while those in the serpentinized dunite show a scattered orientation presumably due to the mesh texture of this rock-type. The new transgranular cracks of both peridotites tend to be subparallel to the compressive stress direction, however, many of them show a random orientation due to the fact that they have been formed as a result of the propagation of grain-boundary cracks. The occurrence of the soft serpentine along fracture surfaces of olivine, when it is in assemblage with orthopyroxene, tends to absorb the applied stress hampering the development of microcracks in olivine. On the other hand in serpentinized peridotites, the microcracks are enhanced in olivine because it is surrounded by large amounts of the much softer and flexible serpentine. Microcracks are usually formed along the cleavage planes of orthopyroxene porphyroclasts, indicating that such crystallographic preferred orientations act as planes of weakness, controlling the direction of the crack paths. Cr-spinel grains likely comprise locations of initiation of microcracks due to their very hard nature and different mechanical behaviour relative to the surrounding silicate phases. Knowledge of the mineralogical and textural characteristics may assist in the prediction of potential development of failure surfaces of an ultrabasic rock in-service.  相似文献   

GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes     

Dmitrii A. Kulik  Thomas Wagner  Svitlana V. Dmytrieva  Georg Kosakowski  Ferdinand F. Hingerl  Konstantin V. Chudnenko  Urs R. Berner 《Computational Geosciences》2013,17(1):1-24

Reactive mass transport (RMT) simulation is a powerful numerical tool to advance our understanding of complex geochemical processes and their feedbacks in relevant subsurface systems. Thermodynamic equilibrium defines the baseline for solubility, chemical kinetics, and RMT in general. Efficient RMT simulations can be based on the operator-splitting approach, where the solver of chemical equilibria is called by the mass transport part for each control volume whose composition, temperature, or pressure has changed. Modeling of complex natural systems requires consideration of multiphase–multicomponent geochemical models that include nonideal solutions (aqueous electrolytes, fluids, gases, solid solutions, and melts). Direct Gibbs energy minimization (GEM) methods have numerous advantages for the realistic geochemical modeling of such fluid–rock systems. Substantial improvements and extensions to the revised GEM interior point method algorithm based on Karpov’s convex programming approach are described, as implemented in the GEMS3K C/C+?+ code, which is also the numerical kernel of GEM-Selektor v.3 package (http://gems.web.psi.ch). GEMS3K is presented in the context of the essential criteria of chemical plausibility, robustness of results, mass balance accuracy, numerical stability, speed, and portability to high-performance computing systems. The stand-alone GEMS3K code can treat very complex chemical systems with many nonideal solution phases accurately. It is fast, delivering chemically plausible and accurate results with the same or better mass balance precision as that of conventional speciation codes. GEMS3K is already used in several coupled RMT codes (e.g., OpenGeoSys-GEMS) capable of high-performance computing.  相似文献   

Natural Metrics in the Spaces of Elliptic Orbits   总被引：1，自引：1，他引：0  

Konstantin V. Kholshevnikov  Nikolay N. Vassiliev 《Celestial Mechanics and Dynamical Astronomy》2004,89(2):119-125

Different natural metrizations by Hölder type on the five dimensional space of Keplerian elliptic orbits are introduced. Certain applications of topological and metrical properties of the space of Keplerian elliptic orbits to several problems of Celestial Mechanics are discussed.  相似文献   

Metric spaces of Keplerian orbits     

Konstantin V. Kholshevnikov 《Celestial Mechanics and Dynamical Astronomy》2008,100(3):169-179

Several metric spaces of Keplerian orbits and a set of their most important subspaces, as well as a factor space (not distinguishing orbits with the same longitudes of nodes and pericentres) are constructed. Topological and metric properties of them are established. Simple formulae to calculate the distance are deduced. Applications to a number of problems of Celestial Mechanics are discussed.  相似文献   

New Taxa of Chrysomelidae (Insecta:Coleoptera)from Rovno Amber,Late Eocene   总被引：1，自引：1，他引：0  

Konstantin NADEIN  Evgeny PERKOVSKY 《《地质学报》英文版》2010,84(4):772-782

<正>Leaf beetles Chrysomelidae of Rovno amber,from the Late Eocene,are recorded and described. Chrysomelidae of Rovno amber are represented by three subfamilies:Galerucinae(Alticini),Chrysomelinae,and Eumolpinae.Two new genera and three new species of Alticini:Manobiomorpha Nadein,gen.nov.(type species Manobiomorpha eocenica Nadein,sp.nov.),Psyllototus Nadein,gen.nov.(type species Psyllototus progenitor Nadein,sp.nov.),and Crepidodera decolorata Nadein et Perkovsky,sp.nov.are described.A new chrysomeline genus and species Paleophaedon minutus Nadein gen.nov.et sp.nov.is described.Probable trophic association of Crepidodera decolorata sp.nov.,the taxonomic positions of Manobiomorpha gen.nov.and Psyllototus gen.nov., and the composition of leaf beetle faunas of Middle and Late Eocene of Europe are discussed.  相似文献   

GIA-induced secular variations in the Earth's long wavelength gravity field: Influence of 3-D viscosity variations     

Konstantin Latychev  Jerry X. Mitrovica  Jeroen Tromp  Robert Moucha 《Earth and Planetary Science Letters》2005,240(2):322-327

Predictions of present day secular variations in the Earth's long wavelength geopotential driven by glacial isostatic adjustment (GIA) have previously been analyzed to infer the radial profile of mantle viscosity and to constrain ongoing cryospheric mass balance. These predictions have been based on spherically symmetric Earth models. We explore the impact of lateral variations in mantle viscosity using a new finite-volume formulation for computing the response of 3-D Maxwell viscoelastic Earth models. The geometry of the viscosity field is constrained from seismic-to-mographic images of mantle structure, while the amplitude of the lateral viscosity variations is tuned by a free parameter in the modeling. We focus on the zonal J˙_? harmonics for degrees ? = 2,…,8 and demonstrate that large-scale lateral viscosity variations of two to three orders of magnitude have a modest, 5-10%, impact on predictions of J˙₂. In contrast, predictions of higher degree harmonics show a much greater sensitivity to lateral variation in viscosity structure. We conclude that future analyses of secular trends (for degree ? > 2) estimated from ongoing (GRACE, CHAMP) satellite missions must incorporate GIA predictions based on 3-D viscoelastic Earth models.  相似文献   

2 International Workshop on Water Dynamics     

Sujoy Ghosh  Asami Sano  Akira Shimojuku  Takaaki Kawazoe  Konstantin Litasov 《Gondwana Research》2005,8(2):291-292

  相似文献   

地球磁场的新模型(英文)   总被引：3，自引：1，他引：2  

Konstantin F.Tyapkin 《地学前缘》1999,6(3):75-84

根据地球内核存在有相对于外核的旋转,这里提出一个地球磁场的新模型。在这种场合下,地球磁场的本源就是电流,这种电流是由在地核团相与液相边界上的一对带电层的相对运动产生出来的（Bullen地球模型中的F层）。所提出的模型,是当前最为常见的水磁发电机模型的另一种可供选择的模型。它在能量方面已得到确证。借助该模型,有可能去解释在地表观察到的关于磁场的所有主要特性。该模型的本质,就在于它是维持地球现今磁场与构造运动的统一机制。这种统一性并不是偶然的,可以将其视为所研究现象本质的理论的最大可能性证据。  相似文献   

Reply to “Water table variations in Atacama Desert alluvial fans”*     

Konstantin W. Scheihing 《水文科学杂志》2020,65(9):1614-1624

ABSTRACT

Viguier et al. propose an alternative conceptual model to the one presented by Scheihing to explain observed groundwater table variations at the foothills of the Andean piedmont in the Pampa del Tamarugal. It is demonstrated that the conceptual model of Viguier et al. is deficient. New findings underline that the confined aquifer of the Pampa del Tamarugal exhibits a hydraulic continuity over regional scales as proposed by Scheihing. Accordingly, short hydraulic response times of several months to distant recharge events can be confirmed. It is suggested that the investigated confined aquifer exhibits transient easterly boundary conditions, with easterly boundaries located in the Andean piedmont. These boundaries underly a periodic forcing due to occasional recharge. Several arguments are presented that support that alluvial fan channel recharge is in the investigated cases likely not a significant recharge mechanism (not to be confused with fan apex recharge).  相似文献   

The new retail trade and services and their emerging location pattern in St. Petersburg   总被引：1，自引：0，他引：1  

Konstantin E. Axenov  Evgeniy Bondarchuk  Isolde Brade 《GeoJournal》1997,42(4):403-417

The system of factors affecting the spatial distribution of the retail trade and service establishments has changed dramatically since socialist times. The administrative regulation lost its almost complete dominance and turned into one of the market forces. In contrast, the impact of the urban environment under very free market conditions substantially increased. We show the main directions of this influence. Two generalized indicators that we use describe macro trends in the development of the spatial system of retail trade and services. One of them, which we call the urban morphology, is of a concentric effect, another – transportation pattern – adds the sectoral component to the retail trade and services geography. Five systems of spatial attractions differently affect the distribution of different branches.  相似文献