Gotowa bibliografia na temat „Polymineralic rocks”

AbstractConventional experiments designed to investigate the mechanical properties of polycrystalline geological materials are generally restricted to measurements of whole-rock properties. However, when comparing the measurements with theoretical models, it is frequently essential to understand how the deformation is accommodated at the grain-scale. This is particularly true for polymineralic rocks because in this case most theories express the whole-rock properties as some function of the properties of their constituent minerals, and hence the contribution which each phase makes to those properties must be measured if the theories are to be fully assessed. The penetrating nature of neutrons offers a method of addressing this problem. By performing deformation experiments in the neutron beam-line and collecting neutron diffraction patterns at different applied loads, the lattice parameters of all the mineral phases present may be determined as a function of load. The elastic strain experienced by each phase is then easily determined. Moreover, the strain in different lattice directions is also obtained. From this information a wide range of problems relevant for the characterization of the elastic and plastic deformation behaviour of polymineralic geological materials can be explored. An experimental technique for carrying out such experiments is described, and its validity is demonstrated by showing that the results obtained from deforming an elastically isotropic olivine + magnesiowüstite sample agree, to within very tight bounds, with the behaviour predicted by theory for elastically isotropic composites.

AbstractThe NASA 2020 Mars mission is a Curiosity-type rover whose objective is to improve the knowledge of the geological and climatic evolution of Mars and to collect rock samples for return to Earth. The new rover has a payload of seven instruments including the SuperCam instrument which consists of four tools including a Raman spectrometer. This Raman device will be non-destructive and will analyse the surface remotely in order to determine the mineralogy of rocks and, by extent, to detect and quantify major elements such as sulfur. Sulfur has been detected as sulfate (Ca,Mg,Fe-sulfates) in sedimentary rocks. This element is difficult to quantify using the laser ablation tool of the ChemCam instrument on-board the Curiosity rover.We propose a Raman calibration to constrain the sulfur abundance in polymineralic mixtures. We acquired Raman signatures on binary and ternary mechanical mixtures containing Ca and Mg sulfates, mixed with natural silicate minerals supposed to be relevant to basaltic-sedimentary rocks at the surface of Mars: olivine, clinopyroxene, orthopyroxene and plagioclase. Using the Voigt function to process the Raman spectra from samples extracted from our mixtures allows us to calculate the initial proportions of our preparations of Ca and Mg sulfates. From these simulations, calibration equations have been provided allowing us to determine sulfate proportions (CaSO4 and MgSO4) in a mixture with basaltic minerals. With the presented calibration, S can be quantified at a lower limit of 0.7 wt.% in Martian soil.

Polymineralic inclusions in loparite-(Ce) in alkaline rocks from the Lovozero massif (Russia) were investigated using electron microprobe analysis, Raman spectroscopy, and X-ray diffraction. A total of 21 mineral species and two groups of minerals (pyrochlore- and labuntsovite-group minerals) were found in these inclusions. Minerals in loparite-hosted inclusions can be divided into two groups: (1) minerals found typically in rocks bearing loparite-(Ce) grains (groundmass minerals) such as aegirine, magnesio-arfvedsonite, potassic feldspar, albite, fluorapatite, etc.; and (2) minerals that were not found in the rock outside of the loparite-(Ce) grains. The latter include lorenzenite, labuntsovite-group minerals, minerals of the neptunite–manganoneptunite series, vinogradovite, catapleiite, fluorite, britholite-(Ce), barylite, genthelvite, and barite, found in the studied samples exclusively inside loparite-(Ce) crystals. The minerals of the second group are typical hydrothermal minerals. We assume that the skeletal crystals of loparite-(Ce), when growing, captured both co-crystallizing minerals and small drops of the mineral-forming solution. Such drops subsequently crystallized within the loparite-(Ce), resulting in the formation of a hydrothermal mineral association.

Sapphirine-bearing rocks are described in the Aulus Basin (Ariège, France) in a contact zone between the Lherz peridotitic body and Mesozoic metasediments which underwent the Pyrenean Cretaceous high-temperature, low-pressure metamorphic event (Monchoux, 1970, 1972a, 1972b). Sapphirine crystals occur in layered clastic deposits characterized by an uncommon suite of Al-Mg-rich minerals. A detailed petrographic study of sixteen samples representative of the diversity of the Lherz sapphirine-bearing rocks is presented. These rocks include breccias and microbreccias with various compositions. Some samples are composed of polymineralic clasts and isolated minerals that derive from regionally well-known protoliths such as ultramafic rocks, meta-ophites, “micaceous hornfels”, and very scarce Paleozoic basement rocks. Nevertheless, a large portion of the sapphirine-bearing clastic suite is composed of mono- and polymineralic debris that derive from unknown protolith(s). We define a "sapphirine-bearing mineral suite” (SBMS) composed of monomineralic debris including: sapphirine + enstatite + aluminous spinel + Mg-amphiboles + Ca-amphiboles + kornerupine + accessory minerals (apatite, diopside, rutile, serpentine, smectite, tourmaline, vermiculite and a white mica). We highlight the dominance of metamorphic Keuper clastic materials in the studied rocks and the presence of inclusions of anhydrite and F-, Cl-, Sr-rich apatite in minerals of the Al-Mg-rich suite. The brecciated texture and the presence of unequivocal sedimentary features suggest that the sapphirine-bearing rocks were mechanically disaggregated and then experienced winnowing in underwater conditions with poor mixing between the different sources. We measured U-Pb rutile age data in order to provide constraints on the age of (one of) the protolith(s) of those clastic deposits. The obtained age (98.6 + 1.2 Ma) is interpreted as the age of metamorphism of this protolith of the SBMS. Previous works interpreted the Lherz sapphirine-bearing rocks as crustal protoliths modified at depth along the contact with the ultramafic rocks of the Lherz body during their ascent towards shallower depths. These new data imply: (i) an Upper Triassic to Lower Jurassic origin for the main protolith of the sapphirine-bearing rocks; (ii) the metamorphism of this protolith along an active hot crust–mantle detachment during Cenomanian times with the involvement of metasomatic, brine-type fluids; and (iii) its brecciation during the exhumation of the material due to the evolution of the detachment, followed by subsequent sedimentary reworking of the metamorphic material.

Aux limites des plaques tectoniques, la lithosphère est déformée et la déformation peut se localiser jusqu'à l'échelle kilométrique, avec formation de zones de cisaillement. Cela suggère que la résistance de la lithosphère est localement réduite. La formation de couches interconnectées de minéraux plus faibles mécaniquement est un mécanisme potentiel pour parvenir à un tel affaiblissement dans la lithosphère. Les péridotites serpentinisées sont couramment présentes dans et aux limites de plaques tectoniques. Elles sont principalement composées des minéraux serpentine et d'olivine, la serpentine étant généralement considérée comme étant plus déformable que l'olivine aux taux de déformation géologiques. La déformation devrait donc se distribuer préférentiellement dans la serpentine plutôt que dans l'olivine. Cela peut conduire à la formation de couches faibles interconnectées (IWL, pour « interconnected weak layer » en anglais) de serpentine, où la contrainte se localise.Ce travail est basé sur l'investigation microstructurale pour comprendre l'accommodation de la déformation dans les roches. Des agrégats d'olivine+serpentine sont utilisés comme proxy pour les péridotites partiellement serpentinisées. Ces agrégats sont déformés en torsion sous haute pression (HP, > 2 GPa) et hautes températures (HT, > 300°C) à un taux de déformation équivalent de 10-4 s-1. Les expériences sont couplées avec de la tomographie in-situ par contraste d'absorption de rayons X. J'obtiens des informations microstructurales en 2D et 3D sur la connectivité et l'orientation de la fabrique de la serpentine, plus déformable. La microscopie électronique est réalisée sur les échantillons post mortem pour relier les observations de tomographie en rayons X aux propriétés plastiques des phases.Je décris tout d'abord les procédures spécifiques, expérimentales et d'analyses d'images in situ, pour la déformation sous haute pression. Ensuite, j'étudie la déformation des agrégats sous un cisaillement croissant à plusieurs échelles d'observation. Le but principal est d'observer la formation et le développement des IWL. Les relations entre la morphologie et les propriétés plastiques des phases dans la roche sont étudiées pour comprendre la localisation de la déformation dans la péridotite partiellement serpentinisée.Les principaux résultats montrent que le régime de déformation dans les agrégats d'olivine + serpentine peut être décrit comme semi-fragile, la phase dominante olivine (plus résistante mécaniquement) présentant principalement une déformation fragile, tandis que la phase serpentine (plus déformable) montre un style de déformation ductile. Un cisaillement γ d'environ 4-5, une teneur en serpentine de 20 % en volume, et une fraction initiale de grands clusters (volumes de serpentine) > 15 % en volume, sont des conditions pour une configuration IWL dans les agrégats d'olivine + serpentine. Inversement, à une teneur en serpentine d'environ 10 % en volume, la configuration IWL ne se produit pas, indépendamment du cisaillement ou de la distribution de taille des clusters initiaux de serpentine. Dans ce cas, un comportement de type « load bearing framework » (LBF) est observé où les grains d'olivine se bloquent et sont broyés lors de la déformation, entraînant une réduction de la taille des grains. Ces grains réduits pourraient accommoder une grande partie de la déformation dans la roche.Ces résultats suggèrent que des teneurs en serpentine > 10 vol.% ou ca. 20 vol.% définissent un seuil clé pour des changements cruciaux dans la morphologie de la serpentine dans les péridotites serpentinisées déformées. Celui-ci pourrait correspondre à des changements importants dans la rhéologie et les propriétés mécaniques de la roche.Enfin, au vu de ces résultats je donne des perspectives sur la localisation de la déformation et l'initiation des zones de cisaillement dans la lithosphère
At plate tectonic boundaries, the lithosphere is deformed and strain localization occurs up to kilometers-scale, which can manifest in form of shear zones. The strain localization suggests the strength of the lithosphere is locally weakened. The formation of interconnected layers of weaker minerals in the lithosphere is a potential mechanism to achieve such weakening. Serpentinized peridotite is commonly found within and between tectonic plates. It is mainly composed of olivine and serpentine minerals. The latter is generally accepted to be weaker than olivine at geological strain rates. During deformation, strain is thus expected to preferentially partition into serpentine than into olivine. This can lead to the formation of interconnected weak layers (IWL) of serpentine where strain localizes.The present work is based on microstructural investigation to infer the strain accommodation in rocks. Olivine+serpentine aggregates with two compositions (10 and 20 vol.% serpentine) are used as a proxy for partially serpentinized peridotites. The aggregates are experimentally deformed in torsion at high pressures (HP, > 2 GPa) and high temperatures (HT, > 300°C) at an equivalent strain rate of 10-4 s-1. The experiments are coupled with in-situ absorption contrast X-ray tomography. I obtain 2D and 3D information on connectivity and structural layering in the microstructure of the ‘weak' serpentine. Electron microscopy is performed on recovered samples to link the in-situ X-ray tomography observations to the plastic properties of the phases.I first outline experimental and image-data processing procedures specific to in-situ HP experimental deformation. Then, I study the deformation of the aggregates with increasing shear deformation at multiple scales of observations. The main aim is to observe the onset and development of IWL in its microstructure. The relations between the morphology and plastic properties of the phases in the rock are investigated to understand the strain localization in serpentinized peridotite.The main results show the deformation regime in olivine+serpentine aggregates can be described as semi-brittle, with the dominant phase of olivine (‘stronger') mainly displaying brittle deformation, whereas the serpentine (‘weaker') showing a dominant ductile-style deformation. A strain γ of ca. 4-5, serpentine content of ca. 20 vol.%, and initial fraction of large clusters >15 vol.% determine the condition for IWL configuration in the olivine+serpentine aggregates. Conversely, at serpentine content of ca. 10 vol.%, IWL do not occur, independently of strain or initial clusters size distribution of serpentine. This is more consistent with a load-bearing framework (LBF) behavior, where the stronger olivine grains are jammed, and during deformation crush one another, leading to grain size reduction and accommodating much of the deformation in the rock. These findings suggest contents of serpentine >10 vol.% or ca. 20 vol.% define a threshold for crucial changes in the morphology, connectivity, percolation, of the weak serpentine in serpentinized peridotites under shear. This may lead to important changes in deformation behavior and mechanical properties of the rock.In light of these findings, I give some perspectives for strain localization and shear zones initiation in the lithosphere

Целью данной работы является демонстрация нескольких методологических подходов к решению задач управления процессами трансформационных превращений вещества на границе раздела фаз макроповерхности и в дисперсных системах, которые можно, на наш взгляд, использовать в качестве критериев количественной характеристики одного из основополагающих законов научного направления «Геоника» - закона «Сродства структур». Предложенные подходы базируются на фундаментальных положениях физической и коллоидной химии, кристаллоэнергетики. В качестве данных критериев, позволяющих управлять структурообразованием на межфазной границе, предложены энергетическая интерпретация кинетической модели топохимического взаимодействия компонентов и значение аналоговой постоянной Гамакера. Разработаны методологические принципы экспериментального определения этих характеристик. Проведена апробация предложенных подходов на примере различных тонкодисперсных композиций: глиоксаль-кора, базальт-кора, базальт-полиминеральный кварцево-полевошпатовый песок и базальт-сапонит. Кроме того, коллоидно-химический подход к созданию суспензий на основе тонкодисперсных частиц горных пород, обладающих специфическими свойствами, позволяет синтезировать агрегативно устойчивые суспензии магнитных жидкостей. Приводятся примеры их использования в строительном материаловедении. This work aims to demonstrate several methodological approaches to solving problems of controlling the transformation processes of matter at the interface of the macro-surface and in dispersed systems, which, in our opinion, can be used as criteria for the quantitative characteristics of one of the fundamental laws of the scientific direction "Geonics" - the "Affinity of structures" law. The proposed approaches are based on the fundamental principles of physical and colloidal chemistry, crystal energy. The energy interpretation of the kinetic model of the topochemical interaction of thecomponents and the analog Hamaker constant value are proposed as these criteria make it possible to control the structure formation at the interface. We have developed the methodological principles for the experimental determination of these characteristics. We have tested the proposed approaches on various finely dispersed compositions: glyoxal-bark, basalt-bark, basalt-polymineral quartz-feldspar sand, and basalt-saponite. Besides, the colloidal-chemical approach to the creation of suspensions based on finely dispersed particles of rocks with specific properties makes it possible to synthesize aggregately stable suspensions of magnetic fluids. Examples of their use in building materials science are given.