Sökning: "mafic"

Visar resultat 1 - 5 av 35 avhandlingar innehållade ordet mafic.

1. 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

   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

3. 2. The geochemistry and petrogenesis of the Notträsk mafic intrusion, northern Sweden

   Författare :Nikos Arvanitidis; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : The Notträsk intrusive body is an early Proterozoic layered mafic intrusion probably of lopolithic form. It intrudes metasedimentary gneisses and shows the characteristics of Precambrian plutons which are contemporaneous with intercratonic tholeiitic volcanism; it represents the cumulates of a crustal-level magma chamber that may have been the source of basaltic volcanism in the area. LÄS MER

4. 3. New constraints on paleoreconstructions through geochronology of mafic dyke swarms in North Atlantic Craton

   Författare :Mimmi Nilsson; Berggrundsgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; baddeleyit; U-Pb; geokronologi; large igneous province; mantelplym; superkontinent; paleorekonstruktion; North Atlantic craton; baddeleyite; Large Igneous Province; Mantle plume; supercontinent; paleoreconstruction; U-Pb; geochronology; North Atlantic craton;

   Sammanfattning : 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. LÄS MER

5. 4. Geochronology and petrology of mafic dykes in the Idefjorden terrane of the Sveconorwegian province, SW Sweden

   Författare :Fredrik Hellström; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : .... LÄS MER

7. 5. Crystal chemistry of Fe-Ti oxides in mafic rocks and metabasites: A study aimed at refinement of geological tools and interpretations

   Författare :Benyam Estifanos; Berggrundsgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Fe-Ti oxide; hercynite; siderite; stilpnomelane; olivine corona; Swedish Caledonides; hysteresis; PIXE; synchrotron XRD; Rietveld; microprobe; red corundum; palaeomagnetism; eclogite; plagioclase clouding; dolerite; pyroxene gneiss; Geology; physical geography; Geologi; fysisk geografi;

   Sammanfattning : This thesis consists of four subprojects: (A) ‘Clouding of plagioclase by Fe-Ti oxides’, (B) ‘Fe-Ti oxides during high-pressure metamorphism of mafic rocks’, (C) ‘Magnetic study of Fe-Ti oxides in mafic rocks and metabasites’, and (D) ‘Topotactic phase transitions in oxide minerals’. A) In southern Sweden dolerite dikes and gabbros with clouded plagioclase are common. LÄS MER