Search for dissertations about: "Precambrian craton"
Found 5 swedish dissertations containing the words Precambrian craton.
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1. 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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2. 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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3. Constraining the timing of veins, faults and fractures in crystalline rocks by in situ Rb-Sr geochronology
Abstract : Precambrian cratons are continent cores archiving the oldest crustal histories on Earth. The crystalline basement of cratons is typically characterized by complex arrays of multiple fracture and fault generations hosting minerals formed by fluids flowing through fracture networks. READ MORE
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4. Precambrian Crustal Evolution of the Rehoboth Province, Southern Africa
Abstract : This thesis uses U-Pb, Sm-Nd Lu-Hf, Ar-Ar and Oxygen isotope data on well-documented rock samples, to investigate crustal evolution of the Precambrian Rehoboth Province of Southern Africa. This province is defined by its smooth magnetic character, reflecting deep magnetic basement in contrast to the adjoining mobile belts and the Kaapvaal Craton. READ MORE
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5. Mesoproterozoic crustal evolution in Southern Africa
Abstract : The objects of this thesis were to use geochronology to investigate crustal evolution of part of Southern Africa that formed during a global event, resulting in the ~1 Ga supercontinent Rodinia. The timing of assembly by continent-continent collisions and the position of the individual continental blocks of this ancient landmass is still largely unknown. READ MORE