Sökning: "Archean"

Visar resultat 1 - 5 av 11 avhandlingar innehållade ordet Archean.

  1. 1. U-Pb dating of detrital zircon from the Mt. Alfred area, Yilgarn Craton, Western Australia

    Författare :Ross Kielman; Martin Whitehouse; Alexander Nemchin; Victoria Pease; Åke Johansson; Jenny Andersson; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Detrital zircon; Geochronology; Archean; Hadean; Western Australia; Geology; geologi;

    Sammanfattning : Hadean and Paleo-Eoarchean aged detrital zircon provide a rare glimpse into the nature of the early Earth. Thus, the characterisation of new localities with rocks that host Hadean and Paleo-Eoarchean zircon provide invaluable insight into the Earth’s early crust. LÄS MER

  3. 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

    Författare :Johan Olsson; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; U-Pb TIMS geochronology; geochemistry; baddeleyite; mafic dyke swarms; mantle plume; Bushveld Complex; Kaapvaal Craton; Zimbabwe Craton; Archean; Proterozoic;

    Sammanfattning : 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. LÄS MER

  4. 3. Timing and Origin of Igneous Rocks in the Gällivare area, Northern Sweden

    Författare :Zimer Sarlus; Christina Wanhainen; Sabina Strmic Palinkas; Luleå tekniska universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Ore Geology; Malmgeologi;

    Sammanfattning : The Gällivare area is one of Europe’s top mining regions. The area is located in the northern Norrbotten ore district which hosts ore deposits such as the Malmberget underground iron ore mine, the Aitik open pit Cu-Au mine and the currently explored Nautanen Cu-Au deposit. In addition, several small, mineralized bodies are found. LÄS MER

  5. 4. Cambro-Ordovician microorganisms: acritarchs and endoliths

    Författare :Martin Stockfors; Malgorzata Vidal-Moczydlowska; John S. Peel; Kenneth John Dorning; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Earth sciences; Cambrian; Ordovician; acritarch; endolith; Kolguev Island; North Greenland; Stratigraphy; Geovetenskap; Earth sciences; Geovetenskap;

    Sammanfattning : Organic-walled microfossils are abundant and taxonomically diverse in Cambrian-Ordovician strata; some are important for biostratigraphy and for the correlation of geological successions. New assemblages of Cambrian-Ordovician acritarchs from Kolguev Island, Arctic Russia and Middle Cambrian ichnofossils of endoliths from Peary Land, North Greenland are studied. LÄS MER

  7. 5. Phosphate and Arsenic Cycling under Experimental Early Proterozoic Marine Conditions

    Författare :Christoffer Hemmingsson; Iain Pitcairn; Ernest Chi Fru; Per Andersson; Christophe Dupraz; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; DIP; Early Proterozoic; coprecipitation; adsorption; Iron formations; BIF; geokemi; Geochemistry;

    Sammanfattning : Nutrient dynamics in the Archean-Paleoproterozoic oceans strongly influenced primary productivity and the rise of atmospheric O2. Reconstructing the cycling of key nutrients such as dissolved inorganic phosphate (DIP) at this time is important for our understanding of the timing, rate and extent of atmospheric oxygenation at this time. LÄS MER