Defects and hydrolytic weakening in α-berlinite AlPO4 a structural analog of quartz     

Bruno Boulogne  Patrick Cordier  Jean-Claude Doukhan 《Physics and Chemistry of Minerals》1988,16(3):250-261

Berlinite, AlPO₄, is a structural analog of quartz and a number of physical properties are very similar in both materials. It is thus interesting to compare their mechanical properties and investigate the possible role of water. Constant strain rate tests on wet synthetic crystals have been performed at room temperature and at 600 MPa confining pressure. They indicate that \((000){1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0em} 3}\langle 11\bar 20\rangle \) is the easy glide system. Detailled investigation of the crystal structure shows that the corresponding a dislocations can glide in such a way that only the weaker Al—O bonds are broken. This explains why this glide system is much more easily activated in berlinite than in quartz. Deformation experiments at higher temperature and at atmospheric pressure clearly show a thermally activated regime. However the actually available crystals are so rich in water that above 300° C the dislocation structure resulting from deformation is completely hidden by water precipitation and coarsening of the as-grown fluid inclusions. Like for wet quartz this later phenomenon generates numerous bubbles and sessile dislocation loops.  相似文献   

Registrazione dei bradisismi costieri     

Dr. Silvio Polli 《Pure and Applied Geophysics》1948,12(3-4):113-120

Riassunto Si descrive un procedimento di livellazione mareografica mediante il quale è possibile determinare la misura di un movimento verticale costiero in senso assoluto, cioè indipendentemente dai moti relativi della costa e del livello medio marino. Esso si basa sulla determinazione delle velocità dell'aumento (aumento in un dato intervallo di tempo) del livello medio marino di tutti i mari e di quella contemporanea della stazione in esame. Queste determinazioni rendono possibile di stabilire un piano fondamentale invariabile nel tempo e nello spazio. Si mette inoltre in evidenza come il procedimento possa dare una precisione che arriva sino al mm su zone costiere lunghe centinaia di km. Si confronta la livellazione mareografica con quella geometrica di precisione. Sono dati infine i risultati di una applicazione al caso delle coste italiane.

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Zusammenfassung Man beschreibt ein Verfahren für eine mareographische Nivellierung womit man eine absolute vertikale Küstenbewegung bemessen kann und zwar unabh?ngig von der relativen Bewegung der Küste und des mittleren Wasserniveaus. Das Verfahren begründet sich auf die Bestimmung der Geschwindigkeiten der Zunahme (Zunahme in einer bestimmten Zwischenzeit) des mittleren Wasserniveaus aller Meere und von der gleichzeitigen Geschwindigkeit der Zunahme der mareographischen Station die geprüft werden soll. Mit diesen Bestimmungen ist es m?glich ein fondamentales Niveau unver?ndert in Zeit und Raume festzustellen. Man bezeigt ausserdem wie das Verfahren eine Pr?zision eines mm für 200–400 km Küstenl?nge geben kann. Man vergleicht die mareographische mit der geometrischen Nivellierung. Man gibt die Resultate der Anwendung dieses Verfahrens an der italienischen Küste.

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Sul sistema: Precipitazione-ghiaccio-deflusso     

Prof. Dr. Silvio Polli 《Pure and Applied Geophysics》1950,17(3-4):221-223

Riassunto Nel sistema precipitazione-deflusso si distinguono i 3 casi secondo che si passa dalla prima al secondo direttamente, o mediante la neve, oppure mediante il ghiaccio. Si considera in particolare questo ultimo caso mettendo in evidenza le proprietà inerziali dell'elemento intermedio. Facendo applicazione alle condizioni glacioclimatiche attuali si prevede per i prossimi anni un deflusso d'ablazione normale.

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Summary In the precipitation-runoff system they are distinguished the 3 cases according to it goes from the precipitation to the runoff directly or by the snow or by ice. Particular consideration is given to this last case. Then is brought in evidence the inertial property of the ice. Applying these considerations to the present conditions, it is forecast for the next years a nearly normal runoff.

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Riflessione ottica di una superficie marina in condizioni naturali     

Prof. Silvio Polli 《Pure and Applied Geophysics》1952,21(1):142-146

Riassunto Mediante cellula fotoelettrica e vetri-filtri selezionatori si determinarono le intensità delle radiazioni riflesse da una superficie acquea in condizioni naturali per ogni altezza solare fra 10^o e 80^o. Per angoli d'incidenza minori di 60^o circa la riflessione effettiva risultò 2–3 volte maggiore di quella teorica, per angoli più grandi risultò notevolmente minore. Massimi scostamenti dai valori teorici si ebbero per le radiazioni azzurre e violette.

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Summary By means of photocells and Schott's glass-filters the intensity of the reflected radiations from a surface of the sea have been determined for every sun-height between 10^o and 80^o. For the incident angles less than 60^o, the effective reflection resulted 2–3 times greater than the theoretic reflection, for greater angles it resulted remarkably inferior. The greatest differences between the determined and the theoretic values have been found for the blue and violet radiations.

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Near bottom variations of turbidity in the St Lawrence estuary     

Bruno d'Anglejan  R. Grant Ingram 《Estuarine, Coastal and Shelf Science》1984,19(6):655-672

Observations of the turbidity and velocity fields in the near-bottom waters of the St Lawrence estuary were obtained with a package which includes a self-recording attenuance meter and a currentmeter. The latter also measures salinity and temperature. Time series varying in length between 26 h and 26 days, and with repetition rates between one and 15 min are discussed for 3 typical open-channel and nearshore stations. A high-frequency sampling mode provides a means to observe the passage of a frontal disturbance over the bottom during the semi-diurnal cycle. With lower frequency records having lengths of one week to one month, contributions to the turbidity fluctuations due to the spring-neap oscillations, seasonal changes in run-off, and the sudden rise in solid discharge of local tributaries following storms, can be resolved. From turbidity polar diagrams, local onshore sources of particulate suspended matter can be identified. Among other advantages, it is possible from such records to time precisely the occurrence of turbidity peaks in relation to the ebb and flow velocities, to assess the importance of resuspension, and to specify exactly the time rate of change of the turbidity. On the whole, self-recording equipments provide a wealth of information unavailable from more traditional hydrocast sampling techniques.  相似文献   

Classifying chalk microtextures: Sedimentary versus diagenetic origin (Cenomanian–Santonian,Paris Basin,France)     

Jessica Saïag  Pierre‐Yves Collin  Jean‐Pierre Sizun  Frdric Herbst  Ophlie Faÿ‐Gomord  Carmela Chateau Smith  Bruno Caline  ric Lasseur 《Sedimentology》2019,66(7):2976-3007

Microtexture describes the type of particles and their arrangement in matrix samples at scanning electron microscopy scale. Although a microtexture classification exists for micritic limestone, it cannot be directly applied to chalk. This study therefore proposes a classification of chalk microtextures and discusses the origin of microtexture variability. Chalk was sampled at thirteen spatio‐temporal locations along the coastline of northern France (Cenomanian–Santonian). Four criteria are defined to describe, characterize and determine chalk matrix microtexture: (i) mineralogical content; (ii) biogenic fraction; (iii) micritic fraction; and (iv) cement fraction. From these criteria, two major groups are defined: Pure Chalk Microtexture Group, with seven classes, and Impure Chalk Microtexture Group, divided into two subgroups: Argillaceous Microtexture with four classes and Siliceous Microtexture with two classes. Microtexture variability is related both to initial sedimentation and to diagenesis. Sedimentological conditions (for example, climate and distance from shore) affect chalk composition (carbonate content and type of insoluble particles), thus influencing microtexture. Changes in Pure Chalk Microtexture are the result of increasing diagenetic intensity. This classification can also be used to characterize the microtexture of subsurface chalk reservoirs. Reservoir quality depends on the petrophysical and mechanical properties of reservoir rocks, which can be better understood by exploring their sedimentary and diagenetic history, revealed by the study of chalk microtexture variability.  相似文献   

New aspects of magma storage and transfer     

Bruno Scaillet  Laurent Arbaret  Fabrice Gaillard 《Comptes Rendus Geoscience》2019,351(8):523-524

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Titanite: A potential solidus barometer for granitic magma systems   总被引：1，自引：1，他引：0  

Saskia Erdmann  Rucheng Wang  Fangfang Huang  Bruno Scaillet  Kai Zhao  Hongsheng Liu  Yan Chen  Michel Faure 《Comptes Rendus Geoscience》2019,351(8):551-561

Constraining crystallization pressure and thus intrusion depth of granites in various geodynamic settings remains challenging, yet important to further our understanding of magma system and crustal evolution. We propose that titanite, which is a common accessory in metaluminous and weakly peraluminous granites, can be used as a barometer if it crystallized in magmatic, near-solidus conditions and in equilibrium with amphibole, plagioclase, K-feldspar, quartz, biotite, and magnetite ± ilmenite. Titanite Al₂O₃ increases with pressure (P) according to: P (in MPa) = 101.66 × Al₂O₃ in titanite (in wt%) + 59.013 (R² = 0.83) with estimated uncertainties of ~±60 to ~±100 MPa for crystallization between ~150 and 400 MPa. We highlight that the current calibration dataset is limited, and that systematic experimental studies are needed to rigorously quantify the relation. The most important use of this empirical barometer will be for rocks in which amphibole is present but significantly altered, or in combination with amphibole barometry, as titanite can be easily dated by LA-ICP-MS.  相似文献   

Automatic correction and simplification of geological maps and cross-sections for numerical simulations     

Pierre Anquez  Jeanne Pellerin  Modeste Irakarama  Paul Cupillard  Bruno Lévy  Guillaume Caumon 《Comptes Rendus Geoscience》2019,351(1):48-58

Incorporating prior geological knowledge in geophysical process models often meets practical meshing challenges and raises the question of how much detail is to be included in the geometric model. We introduce a strategy to automatically repair and simplify geological maps, geological cross-sections and the associated meshes while preserving elementary consistency rules. To identify features breaking validity and/or the thin features potentially problematic when generating a mesh, we associate an exclusion zone with each model feature (horizon, fault). When these zones overlap, both the connectivity and the geometry of the geological layers are automatically modified. The output model enforces specific practical quality criteria on the model topology and geometry that facilitates the generation of a mesh with lower bounds on minimum angles and minimum local entity sizes. Our strategy is demonstrated on an invalid geological cross-section from a real-case study in the Lorraine coal basin. We further explore the impacts of the model modifications on wave propagation simulation. We show that the differences on the seismograms due to model simplifications are relatively small if the magnitude of simplifications is adapted to the physical problem parameters.  相似文献   

Rates of generation and growth of the continental crust   总被引：4，自引：1，他引：3  

Chris Hawkesworth  Peter A. Cawood  Bruno Dhuime 《地学前缘(英文版)》2019,10(1):165-173

Models for when and how the continental crust was formed are constrained by estimates in the rates o crustal growth. The record of events preserved in the continental crust is heterogeneous in time with distinctive peaks and troughs of ages for igneous crystallisation, metamorphism, continental margin and mineralisation. For the most part these are global signatures, and the peaks of ages tend to b associated with periods of increased reworking of pre-existing crust, reflected in the Hf isotope ratios o zircons and their elevated oxygen isotope ratios. Increased crustal reworking is attributed to periods o crustal thickening associated with compressional tectonics and the development of supercontinents Magma types similar to those from recent within-plate and subduction related settings appear to hav been generated in different areas at broadly similar times before ~3.0 Ga. It can be difficult to put th results of such detailed case studies into a more global context, but one approach is to consider when plate tectonics became the dominant mechanism involved in the generation of juvenile continental crust The development of crustal growth models for the continental crust are discussed, and a number o models based on different data sets indicate that 65%-70% of the present volume of the continental crus was generated by 3 Ga. Such estimates may represent minimum values, but since ~3 Ga there has been reduction in the rates of growth of the continental crust. This reduction is linked to an increase in th rates at which continental crust is recycled back into the mantle, and not to a reduction in the rates a which continental crust was generated. Plate tectonics results in both the generation of new crust and it destruction along destructive plate margins. Thus, the reduction in the rate of continental crustal growth at ~3 Ga is taken to reflect the period in which plate tectonics became the dominant mechanism b which new continental crust was generated.  相似文献