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In order to obtain a better understanding of fluorite deposits, rare earth impurities have been analyzed for a large number of samples taken from cross-sections of several low temperature hydrothermal veins. Two types of measurements have been used: Electron Paramagnetic Resonance (EPR) and Neutron Activation Analysis (NAA). For Gd, the ratio of spin concentrations to total concentration [Gd3+]/[Gdtotal] is close to 1 in all the samples; on the other hand, the ratios [Eu2+]/[Eutotal] and [Ce3+ -F ? i ]/[Cetotal] exhibit large variations. The first result suggests that the major part of the lanthanides in the samples is incorporated in the crystal lattice and that clustering of lanthanides ions is not important. The behaviour of Eu and Ce is ascribed to charge state changes and symmetry state changes respectively. 相似文献
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Granite magma migration and emplacement along thrusts 总被引：1，自引：0，他引：1
Eric C. Ferré Olivier Galland Domenico Montanari Thomas J. Kalakay 《International Journal of Earth Sciences》2012,101(7):1673-1688
This paper investigates the influence exerted by brittle tectonic structures in the emplacement of granite plutons in contractional settings. We address both cases where contractional tectonics and magma intrusion are (1) coeval, to study how active contractional tectonics controls the transport of magma, and (2) diachronous, to study the role of pre-existing structures on the transport of magma. In light of new experimental models, we show that magma can rise along thrusts ramps and flats. This phenomenon occurs for both low-viscosity magma (basalts to andesite) and high-viscosity magma (dry granite). The experimental results also allow the evaluation of the role played by magma viscosity in determining pluton geometries. In addition, a review of literature demonstrates a spatial and causal relationship between granites and thrusts and highlights the geometric control of magma pathways in the pluton final shape. The abundance of subhorizontal and tabular granitic intrusions indicates that the location of inflating granitic sills along thrust flats can be common. We argue that active and pre-existing flats-and-ramps thrusts provide a preferential continuous planar anisotropy susceptible to become a granitic magma migration pathway. 相似文献
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Résumé Après avoir vérifié que l'ion paramagnétique Tm2+ est créé dans la fluorite naturelle par réduction de l'ion Tm3+ sous irradiation, nous proposons une estimation de la fraction [Tm2+]/[Tmtotal], à une proportionnalité près, fondée sur la seule spectroscopie de R.P.E.. L'analyse par R.P.E. d'un échantillonnage qui recouvre divers gisements de fluorite prouve alors qu'il existe deux contributions possibles à l'irradiation: un rayonnement gamma émis par des descendants de l'uranium présents dans le gisement, le rayonnement alpha du samarium 147 que recèle le réseau même de la fluorite. Nous montrons que la sonde paramagnétique Tm2+/fluorite est suffisamment sélective pour caractériser une radioactivité anormale dans l'histoire du gisement.
We verify that the paramagnetic ion Tm2+ is created in natural fluorite by the reduction of the ion Tm3+ under irradiation. We propose that the fraction [Tm2+]/[Tmtotal] may be estimated, to within a factor of proportionality, by a method based solely on E.P.R.. The analysis by E.P.R. of samples of fluorite from diverse origins then shows that there are two possible contributions to the irradiation: a gamma radiation emitted by daughter isotopes of uranium present in the deposit, the alpha radiation from samarium 147 in the fluorite lattice itself. We show that the paramagnetic probe Tm2+ in fluorite is selective enough to characterize abnormal radioactivity in the history of the deposit.相似文献
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To investigate how magma rises through the brittle upper crust in a context of compressional tectonics, we have performed experiments on scaled physical models. Powdered silica (having a cohesion of 300 Pa and an angle of internal friction of 38°) was used to represent brittle crust. A vegetable oil (with a Newtonian viscosity of 10?2 Pa·s at 50 °C) was used to represent magma. A moving piston shortened the models in a box, while oil was injected steadily at the base. On cooling to room temperature, the oil solidified. The resulting intrusions were thin sills, dykes and laccoliths. Their shapes and emplacement modes depended on the ratio R between rates of shortening and injection. From shapes and orientations of intrusions, we infer that hydraulic fracturing was one mechanism of emplacement. Unconsolidated intrusions strongly influenced thrust formation. On the basis of our experiments, we suggest that magmas in orogenic belts can rise along thrust faults. 相似文献
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Margaret Galland Kivelson 《Planetary and Space Science》1984,32(11):1335-1341
Conditions for the development of Kelvin-Helmholtz (K-H) waves on the magnetopause have been known for more than 15 years; more recently, spacecraft observations have stimulated further examination of the properties of K-H waves. For amagnetopause with no boundary layer, two different modes of surface waves have been identified and their properties have been investigated for various assumed orientations of magnetic field and flow velocity vectors. The power radiated into the magnetosphere from the velocity shear at the boundary has been estimated. Other calculations have focused on the consequences of finite thickness boundary layers, both uniform and non-uniform. The boundary layer is found to modify the wave modes present at the magnetopause and to yield a criterion for the wavelength of the fastest growing surface waves. The paper concludes by questioning the extent to which the inferences from boundary layer models are model dependent and identifies areas where further work is needed or anticipated. 相似文献
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Juan Bautista Spacapan Alejandro D´Odorico Octavio Palma Olivier Galland Kim Senger Remigio Ruiz Rene Manceda Hector Armando Leanza 《Basin Research》2020,32(1):3-24
Igneous sills and laccoliths emplaced in sedimentary basins may significantly impact petroleum systems, both positively and negatively. Igneous intrusions provide heat to maturate regionally immature organic-rich host rocks, act as fractured reservoirs hosting commercial accumulations of hydrocarbons, and form structures affecting fluid flow and trapping at different scales. Nevertheless, the petrophysical implications of igneous intrusions on their host rock are poorly known. In this study, we analyse 200 wells in the Río Grande Valley oil field, Neuquén basin, Argentina, where the main reservoirs are in fractured igneous sills. This dataset represents a globally unique possibility to characterize the igneous–host rock interaction using both wireline logs and core material. We identify a systematic Contact Low Resistivity Zone (CLRsZ) at both the upper and lower contacts of the sills emplaced in the organic-rich Vaca Muerta and Agrio Formations. We characterize the nature of these CLRsZ and their petrophysical properties by integrating resistivity and gamma ray well logs, petrographic analyses, petrophysical tests and geochemical analyses. The low resistivity signal of the CLRsZ is dominantly carried by massive-sulphide deposits, mainly pyrite, observed both in the host rock and the chilled margin of the sills. Well log images and porosity-permeability analysis on core plugs show that both the sills and their associated CLRsZ can act as carrier for fluid flow and reservoir for hydrocarbons storage. The thickness of the upper and lower CLRsZ correlates linearly with the thickness of the sill, and the volume of both the upper and lower CLRsZ represents ca. 40% with respect to the volume of their associated sill. The thickness of the CLRsZ represents ca. 13% of the thickness of contact aureole induced by the sills. In the CLRsZ, a great proportion of kerogen was transformed to hydrocarbon, so that CLRsZ were restricted to the innermost contact aureole of the sills. Our results show that the CLRsZ can have major implications on fluid flow and should be considered in reservoir models in volcanic basins hosting sills emplaced in organic-rich formations. 相似文献
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The ocean plays a major role in regulating Earth's climate system, and is highly vulnerable to climate change, but continues to receive little attention in the ongoing policymaking designed to mitigate and adapt to global climate change. There are numerous ways to consider the ocean more significantly when developing these policies, several of which offer the co-benefits of biodiversity protection and support of marine-dependent human communities. When developing forward-thinking climate change policy, it is important to understand the ways that the ocean contributes to global climate and to fully inventory the services that the ocean provides to humans. Without more inclusive consideration of the ocean in climate policy, at all levels of governance, policy makers risk weaker than necessary mitigation and adaptation strategies. 相似文献
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C. Bonadonna R. Cioni A. Costa T. Druitt J. Phillips L. Pioli D. Andronico A. Harris S. Scollo O. Bachmann G. Bagheri S. Biass F. Brogi K. Cashman L. Dominguez T. Dürig O. Galland G. Giordano M. Gudmundsson M. Hort A. Höskuldsson B. Houghton J.C. Komorowski U. Küppers G. Lacanna J.L. Le Pennec G. Macedonio M. Manga I. Manzella M. de’ Michieli Vitturi A. Neri M. Pistolesi M. Polacci M. Ripepe E. Rossi B. Scheu R. Sulpizio B. Tripoli S. Valade G. Valentine C. Vidal N. Wallenstein 《Bulletin of Volcanology》2016,78(11):84
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Olivier Galland Sverre Planke Else-Ragnhild Neumann Anders Malthe-Sørenssen 《Earth and Planetary Science Letters》2009,277(3-4):373-383
Saucer-shaped dolerite and sandstone intrusions are common in sedimentary basins world-wide. We have conducted a series of scaled experiments simulating the process of magma emplacement in sedimentary basins, with particular attention on the formation of saucer-shaped sills. The model materials were (1) cohesive fine-grained silica flour, representing brittle crust; and (2) molten low-viscosity oil, representing magma. The experiments were performed in both homogeneous and layered models. In all the experiments, oil injection resulted in doming of the surface. In the homogeneous models, the injected oil formed cone sheets and sub-vertical dykes. Cone sheets formed for shallow injection (1–3 cm), and vertical dykes formed for deeper injection (4–5 cm). In layered models, the injected oil always formed saucer-shaped intrusions. Our experimental results show that (1) sill intrusion results in the formation of a dome, with melt erupting at the rim; (2) layering controls the formation of sills and saucer-shaped sills; (3) saucer-shaped sills are fed from the bottom and the fluid flows upward and outward; and (4) the diameter of saucer-shaped sills increase with increasing emplacement depth. The systematic relation between domes and sills and the depth-dependence of sill diameters show that saucer-shaped intrusions result from the interaction between a growing flat-lying shallow sill and doming of the free surface. We conclude that saucer-shaped intrusions represent fundamental geometries formed by shallow magma intrusion in stratified basins. 相似文献
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