Contribution of studies of sub-seismic fracture populations to paleo-hydrological reconstructions (Bighorn Basin, USA)

This work reports on the reconstruction of the paleo-hydrological history of the Bighorn Basin (Wyoming, USA) and illustrates the advantages and drawbacks of using sub-seismic diffuse fracture populations (i.e., micrometric to metric joints and veins forming heterogeneous networks), rather than fault zones, to characterize paleo-fluid systems at both fold and basin scales. Because sub-seismic fractures reliably record the successive steps of deformation of folded rocks, the analysis of the geochemical signatures of fluids that precipitated in these fractures reveals the paleo-fluid history not only during, but also before and after, folding. The present study also points out the need for considering pre-existing fluid systems and basin-scale fluid migrations to reliably constrain the evolution of fluid systems in individual folds

Zebra pattern in rocks as a function of grain growth affected by second-phase particles

Alternating fine grained dark and coarse grained light layers in rocks are often termed zebra patterns and are found worldwide. The crystals in the different bands have an almost identical chemical composition, however second-phase particles (e.g., fluid filled pores or a second mineral phase) are concentrated in the dark layers. Even though this pattern is very common and has been studied widely, the initial stage of the pattern formation remains controversial. In this communication we present a simple microdynamic model which can explain the beginning of the zebra pattern formation. The two dimensional model consists of two main processes, mineral replacement along a reaction front, and grain boundary migration affected by impurities. In the numerical model we assume that an initial distribution of second-phase particles is present due to sedimentary layering. The reaction front percolates the model and redistributes second-phase particles by shifting them until the front is saturated and drops the particles again. This produces and enhances initial layering. Grain growth is hindered in layers with high second-phase particle concentrations whereas layers with low concentrations coarsen. Due to the grain growth activity in layers with low second-phase particle concentrations these impurities are collected at grain boundaries and the crystals become very clean. Therefore, the white layers in the pattern contain large grains with low concentration of second-phase particles, whereas the dark layers contain small grains with a large second-phase particle concentration. The presence of the zebra pattern is characteristic for regions containing Pb-Zn mineralization. Therefore, the origin of the structure is presumably related to the mineralization process and might be used as a marker for ore exploration. A complete understanding of the formation of this pattern will contribute to a more accurate understanding of hydrothermal systems that build up economic mineralization

Sens et articulation dans Sein und Zeit : vers une grammaire de l'être

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Fingerprinting stress: stylolite and calcite twinning paleopiezometry revealing the complexity of progressive stress patterns during folding-the case of the Monte Nero anticline in the Apennines, Italy

In this study we show for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a fold-and-thrust belt. First, we present a new method that gives access to stress inversion using tectonic stylolites without access to the stylolite surface and compare results with calcite twin inversion. Second, we use our new approach to present a high-resolution deformation and stress history that affected Meso-Cenozoic limestone strata in the Monte Nero Anticline during its late Miocene-Pliocene growth in the Umbria-Marche Arcuate Ridge (northern Apennines, Italy). In this area an extensive stylolite-joint/vein network developed during layer-parallel shortening (LPS), as well as during and after folding. Stress fingerprinting illustrates how stress in the sedimentary strata did build up prior to folding during LPS. The stress regime oscillated between strike slip and compressional during LPS before ultimately becoming strike slip again during late stage fold tightening. Our case study shows that high-resolution stress fingerprinting is possible and that this novel method can be used to unravel temporal relationships that relate to local variations of regional orogenic stresses. Beyond regional implications, this study validates our approach as a new powerful toolbox to high-resolution stress fingerprinting in basins and orogens combining joint and vein analysis with sedimentary and tectonic stylolite and calcite twin inversion techniques

A new stylolite classification scheme to estimate compaction and local permeability variations

This study was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 “Mineral Vein Dynamics Modeling”, which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, DEA Deutsche Erdoel AG and Wintershall Holding GmbH, within the basic research program of the WEG Wirtschaftsverband Erdoel- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish these results. This work has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 31688. The Zechstein data were collected with the help of Simon Gast. We thank Jean-Pierre Gratier and an anonymous reviewer for their comments that improved an earlier version of the manuscript.Peer reviewedPostprin

Paleostress magnitudes in folded sedimentary rocks

International audienceUsing Sheep Mountain Anticline (Wyoming, USA) as a case study, we propose a new approach to quantify effective paleo-principal stress magnitudes in the uppermost crust. The proposed mechanical scenario relies on a well-documented kinematic and chronological sequence of development of faults, fractures and microstructures in the folded strata. Paleostress orientations and regimes as well as differential stress magnitudes based on calcite twinning paleopiezometry are combined with rock mechanics data in a Mohr construction to derive principal stress magnitudes related to the successive steps of layer-parallel shortening and to late stage fold tightening. Such quantification also provides original insights into the evolution of the fluid (over)pressure and amount of syn-folding erosion

Entraînement d'un modèle supervisé pour la détection du plaisir en contexte de jeu vidéo à partir de signaux physiologiques et d'indices comportementaux

La modélisation de l’expérience de jeu présente un intérêt considérable pour la conception de jeux vidéo adaptatifs. Les jeux vidéo adaptatifs utilisent l’information émotionnelle contenue dans les signaux physiologiques et les indices comportementaux pour personnaliser l’expérience de jeu vidéo, et ce dans le but de générer une expérience optimale de jeu. Afin de modéliser l’expérience de jeu, le présent projet de recherche s’est penché sur la détection du plaisir d’un joueur à partir de signaux physiologiques (électrocardiogramme, activité électrodermale, activité respiratoire et électromyogramme) et d’indices comportementaux (expressions faciales, mouvements de la tête et entrées d’un contrôleur Xbox). Dans ce travail, des modèles supervisés(SVM, Forêt d’arbres décisionnels et kNN) ont été entrainés sur un jeu de données construit à partir de la base de données FUNii, qui contient les données physio-comportementales de 219 joueurs réparties sur 362 séances de jeu de la franchise Assassin’s Creed. Une méthode pour la création de classes de plaisir à partir du facteur-fun, un outil d’annotation continue du plaisir, à également été proposée. Le meilleur modèle entrainé a permis de distinguer trois classes de plaisir avec un taux de classement de 53, 5% sur un jeu de test, une amélioration de 12,5% par rapport au meilleur résultat obtenu dans des travaux antérieurs.Modeling the gaming experience is of considerable interest for designing adaptive video games. Adaptive video games use the emotional information contained in physiological signals and behavioral cues to personalize the video game experience,in order to generate an optimal gaming experience. With the purpose of modeling the gaming experience, this research project has focused on the detection of a player’s fun using physiological signals (electrocardiogram, electrodermal activity, respiratory activity and electromyogram) and behavioral cues (facial expressions,head movements and facial expressions and inputs from an Xbox controller). In this work, supervised machine learning models (SVM, Random Forest and kNN) were trained on a dataset built from the FUNii database, which contains the physiobehavioral data of 219 players spread over 362 game sessions of the Assassin’s Creed franchise. A method for creating fun classes from the fun factor, a tool for continuous annotation of fun, has also been proposed. The best model trained allowed to distinguish three classes of pleasure with an accuracy of 53, 5% on a test dataset, an improvement of 12, 5% compared to the best result obtained in previous works

Reaction-induced porosity fingering: replacement dynamic and porosity evolution in the KBr-KCl system

In this contribution, we use X-ray computed micro-tomography (X-CT) to observe and quantify dynamic pattern and porosity formation in a fluid-mediated replacement reaction. The evolution of connected porosity distribution helps to understand how fluid can migrate through a transforming rock, for example during dolomitization, a phenomenon extensively reported in sedimentary basins. Two types of experiment were carried out, in both cases a single crystal of KBr was immersed in a static bath of saturated aqueous KCl at room temperature and atmospheric pressure, and in both cases the replacement process was monitored in 3D using X-CT. In the first type of experiment a crystal of KBr was taken out, scanned, and returned to the solution in cycles (discontinuous replacement). In the second type of experiment, 3 samples of KBr were continuously reacted for 15, 55 mins and 5.5 hours respectively, with the latter being replaced completely (continuous replacement). X-CT of KBr-KCl replacement offers new insights into dynamic porosity development and transport mechanisms during replacement. As the reaction progresses the sample composition changes from KBr to KCl via a K(Br,Cl) solid solution series which generates porosity in the form of fingers that account for a final molar volume reduction of 37% when pure KCl is formed. These fingers form during an initial and transient advection regime followed by a diffusion dominated system, which is reflected by the reaction propagation, front morphology, and mass evolution. The porosity develops as fingers perpendicular to the sample walls, which allow a faster transport of reactant than in the rest of the crystal, before fingers coarsen and connect laterally. In the continuous experiment, finger coarsening has a dynamic behaviour consistent with fingering processes observed in nature. In the discontinuous experiment, which can be compared to rock weathering or to replacement driven by intermittent fluid contact, the pore structure changes from well-organized parallel fingers to a complex 3D connected network, shedding light on the alteration of reservoir properties during weathering