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  • 1
    Publikationsdatum: 2018-04-25
    Beschreibung: Economically viable concentrations of mineral resources are uncommon among the predominantly silicate-dominated rocks in Earth's crust. Most ore deposits that were mined in the past or are currently being extracted were found at or near Earth's surface, often serendipitously. To meet the future demand for mineral resources, exploration success hinges on identifying targets at depth, which, on the one hand, requires advances in detection and interpretation techniques for geophysical and geochemical data. On the other hand, however, our knowledge of the chain of events that lead to ore deposit formation is limited. As geoscience embraces an integrated Earth systems approach, considering the geodynamic context of ore deposits can provide a step change in understanding why, how, when and where geological systems become ore-forming systems. Contributions to this volume address the future resources challenge by: (i) applying advanced microscale geochemical detection and characterization methods; (ii) introducing more rigorous 3D Earth models; (iii) exploring critical behaviour and coupled processes; (iv) evaluating the role of geodynamic and tectonic setting; and (v) applying 3D structural models to characterize specific ore-forming systems.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2016-10-14
    Beschreibung: The Ilomantsi greenstone belt is a Neoarchaean, c. 2.75–2.70 Ga volcanic–sedimentary complex in which metamorphic grade increases from staurolite grade in the SW of the belt to sillimanite grade in the NE. In the staurolite zone, prograde garnet zoning indicates pressure and temperature increases from 480–500°C at 2–4 kbar to 560–570°C at 6–7 kbar. Within the sillimanite zone temperatures peaked at 660–670°C at pressures of around 6 kbar. The U–Pb age determinations on monazite from the sillimanite zone yielded both Archaean and Proterozoic ages. One sample contains an exclusively Archaean monazite population of 2620±24 Ma, while another sample has two generations of monazite, with ages of 2664±33 Ma and 1837±13 Ma. The monazite data confirm that the Ilomantsi greenstone belt was metamorphosed simultaneously with the surrounding Neoarchaean migmatite complexes. The apparent clockwise PT path and medium P / T -type metamorphism are consistent with collisional tectonic settings, but the two distinct metamorphic events recorded by monazite indicate that a second, Palaeoproterozoic thermal event caused recrystallization and new mineral growth, in line with previous evidence from other isotopic systems. Accordingly, great care is necessary in defining metamorphic evolutionary P–T–t paths in rocks with complex mineral assemblages, to ensure correct identification of truly coeval mineral assemblages.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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