Search for dissertations about: "dyke swarm"
Showing result 1 - 5 of 7 swedish dissertations containing the words dyke swarm.
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1. Validating the existence of the supercraton Vaalbara in the Mesoarchaean to Palaeoproterozoic
Abstract : In this thesis, the longevity and continuity of the Vaalbara supercraton is addressed in six papers aimed at placing new temporal and spatial constraints onthe supercraton in the Mesoarchean to Paleoproterozoic. It has been speculated since the 1960’s that the Kaapvaal Craton in southern Africa, together withthe Pilbara Craton in Western Australia existed as a single landmass during the Precambrian – the Vaalbara supercraton. READ MORE
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2. U-Pb baddeleyite geochronology of Precambrian mafic dyke swarms and complexes in southern Africa - regional scale extensional events and the origin of the Bushveld Complex
Abstract : Dolerite dykes are formed when iron- and magnesium-rich (mafic) mantle-derived magmas ascend through the lithosphere (upper part of the mantle) and crystallize as ‘hydro-fractures’ within the crust. Dykes may exist in great numbers to form dyke swarms (linear or radiating), which can be linked to time periods of continental break-up, or attempted break-up events, associated with voluminous volcanism. READ MORE
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3. Origin and composition of the Hällefors composite dyke, central Sweden
Abstract : The Hällefors dyke is a large, wedge-shaped high-level intrusion that trends E-W and has a subvertical dip, the overall dimensions being about 42 km in length and 1 km in width. It was emplaced ca 1550 Ma ago in gneisses of the Svecokarelian (1950-1750 Ma) orogenic belt in south central Sweden. READ MORE
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4. New constraints on paleoreconstructions through geochronology of mafic dyke swarms in North Atlantic Craton
Abstract : Earth history is punctuated by a series of events of supercontinent amalgamation and break-up. Fragments of old continents display rifted margins and orogenic sutures that testify their involvement in supercontinent cycles. READ MORE
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5. Rapakivi granite and basic dykes in the Fennoscandian shield : a palaeomagnetic analysis
Abstract : Rapakivi rocks and basic dykes in the central part of Sweden have been subject to a palaeomagnetic study with the aim of putting the formation of these rocks into a plate tectonic context. Virtual geomagnetic poles were calculated and found to be distributed around the Jotnian Loop of the APWP of Fennoscandia. READ MORE