Sökning: "U-Pb geochronology"

Visar resultat 1 - 5 av 32 avhandlingar innehållade orden U-Pb geochronology.

  1. 1. The evolution of lunar breccias : U-Pb geochronology of Ca-phosphates and zircon using Secondary Ion Mass Spectrometry

    Författare :Fiona Karen Thiessen; Martin Whitehouse; Alexander Nemchin; Victoria Pease; Barbara Cohen; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Moon; impact breccias; Apollo missions; impact event; Late Heavy Bombardment; zircon; Ca-phosphates; U-Pb; SIMS; geochronology; Geology; geologi;

    Sammanfattning : Planetary bodies in our Solar System, including the Moon, were exposed to an intense asteroid bombardment between ~4.5-3.8 Ga, shaping their surfaces and leaving visible “footprints” in the form of large impact basins. The end of this period (~4. LÄS MER

  3. 2. The tectonic evolution of the western part of the Svecofennian orogen, central Sweden : Insight from U/Pb and 40Ar/39Ar geochronology at Forsmark

    Författare :Tobias Hermansson; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; physical geography; Geology; Svecofennian orogen; Tectonic models; Tectonic cycles; Uplift; Cooling; Ductile deformation; Geochronology; U Pb; 40Ar 39Ar; Geologi; fysisk geografi; Petrology; mineralogy; geochemistry; Petrologi; mineralogi; geokemi;

    Sammanfattning : The Forsmark area, in the western part of the Svecofennian orogen, central Sweden, is situated between two major Palaeoproterozoic tectonic domains that show contrasting histories with respect to timing of igneous activity, ductile deformation and metamorphism. At Forsmark, WNW to NW trending, ductile deformation belts anastomose around tectonic lenses with an inferred lower degree of ductile strain. LÄS MER

  4. 3. Geography and geometry of pre-Caledonian western Baltica: U-Pb geochronology and Palaeomagnetism

    Författare :Emma Rehnström; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physical geography; geomorphology; pedology; cartography; climatology; Fysisk geografi; geomorfologi; marklära; kartografi; klimatologi; Fennoscandia; correlations; Baltica; Early Palaeozoikum; palaeogeography; orthogneisses; nappes; palaeomagnetism; U-Pb geochronology; Caledonian orogen; Scandinavia;

    Sammanfattning : In an attempt to reconstruct the pre-Caledonian cratonic margin of Fennoscandia, U-Pb geochronological and geochemical investigations have been performed on allochthonous orthogneisses in the northern Swedish Caledonides. The crystalline basement of the nappes have also been examined to further constrain the continuation of various chronologically defined orogenic belts. LÄS MER

  5. 4. 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

  7. 5. Geochronology of Tectonothermal Events in the Parautochthonous Eastern Segment of the Sveconorwegian (Grenvillian) Orogen, Southwestern Sweden

    Författare :Ulf Söderlund; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sveconorwegian; SW Sweden; Eastern Segment; geochronology; U-Pb; zircon; titanite; polymetamorphic; high-grade; Geology; exhumation; physical geography; Geologi; fysisk geografi;

    Sammanfattning : Timing of deformation and metamorphism yield important information for understanding the development of orogenic processes and correlation of mobile belts and continents. This thesis adds new geochronological data constraining the age of protoliths and events of reworking in the frontal region of the c. 1.2-0. LÄS MER