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  • 1
    Description / Table of Contents: The ten articles in this book describe the mode of emplacement of various types of intrusions (salt diapirs, mud volcanoes and magmatic bodies) by means of theoretical reasoning, analogue and analytical modelling, interpretation of seismic and field data, and geodetic surveying. All the articles emphasize the role of regional tectonics in driving or controlling the emplacement of the intrusions. The selection of articles includes examples from Spain, Romania, onshore and offshore Italy, the Eastern Mediterranean, Israel and iran. Better understanding of the mode of emplacement of these intrusions has applications in hydrocarbon exploration (e.g., where salt structures or mud diapirs are present) and in the mining industry (where mineralization is related to the emplacement of batholiths).
    Pages: Online-Ressource (204 Seiten)
    ISBN: 1862390665
    Language: English
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  • 2
    Publication Date: 2014-03-31
    Description: This study investigates the large strain rheological behaviour of pelitic rocks undergoing melting and subsequent crystallization during deformation. Constant strain rate ( =3x10 -4  s -1 ) torsion experiments were performed to achieve large strains ( γ max  = 15) on synthetic aggregates of quartz and muscovite at 300 MPa confining pressure and temperature of 750 °C. A set of hydrostatic experiments for equivalent times of the torsion experiments was also conducted at 300 MPa and 750 °C to evaluate the reaction kinetics and microstructures under static and under deforming conditions. Microstructures of the deformed samples reveal four distinct but gradational stages of crystal-melt interactions - a) solid state deformation, b) initiation and domination of partial melting, c) simultaneous partial melting and crystallization and d) domination of crystallization. These four microstructural stages are linked to the changes of the bulk mechanical response of the deforming samples. Partial melting starts at relatively low finite shear strains ( γ  = 1-3) and is associated with strong ( ca . 60%) strain softening. With further shearing ( γ  = 4-10) the partially molten bulk material shows a constant (“steady state”) flow at low stress. Further crystallization of new crystals at the expense of melt between γ  = 10 and 15 causes weak strain hardening until the material fails by developing brittle fractures. The stress exponent ( n ) values, calculated at three different shear strains ( γ  = 1, 5 and 10), increase from ∼ 3 to ∼ 43 with increasing deformation, pointing out a transition from power to power law break-down or exponential flow of the bulk system. These new experimental data establish that partially molten rock does not flow according to a constant strain rate dependent power law (“steady state”) rheology. The rheological transition from strain rate sensitive to strain rate insensitive flow is interpreted as a function of melt-crystal ratio, their mutual interactions and the evolution of microstructures in the partially molten rock.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2012-08-09
    Description: The highest concentrations of metals (e.g., Cu, Au, Ag, Mo) in the Earth's crust are found in porphyry-type deposits. The metals are ultimately sourced from magmas, and appear to be concentrated hundred to thousand-fold from typical magmatic contents (ppm-ppb) in the exsolved volatile phase. To better quantify the purging and transport of metals, we develop a physical model of volatile evolution in an incrementally built upper crustal magma reservoirs that considers (1) partitioning of metals from the melt to an exsolved volatile phase, and (2) advection of the buoyant volatile phase using a single dimensionless parameter, the Péclet number (Pe; ratio of advection rate over diffusion rate). We propose that metal extraction and segregation from magmas can occur in 3 stages with different Pe: (1) during exsolution of the magmatic volatile phase in shallow, crystal-poor magma bodies (slow volatile advection; Pe ≪ 1), (2) during the growth of volatile channels that develop in the reservoir as crystallinity increases (Pe 〈 1), and (3) during advection in connected channels (rapid volatile advection, high Pe ≥ 1). For each stage, a metal enrichment factor can be calculated, allowing insight into the optimal conditions to maximize metal mass flux into the overlying hydrothermal system. The model predicts that the most efficient purging of metals occurs for magmas with intermediate volatile contents and is enhanced during late-stage magmatic activity, as the reservoirs reach high crystallinity and are not disturbed by volcanic venting, in agreement with natural observations suggesting that ore formation post-dates volcanic activity.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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