Sökning: "U Pb"

Visar resultat 1 - 5 av 52 avhandlingar innehållade orden U Pb.

  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. Sveconorwegian orogenesis in the southwestern Baltic Shield - Zircon geochronology and tectonothermal setting of orthogneisses in SW Sweden

    Författare :Jenny Andersson; Berggrundsgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Petrology; Geologi; fysisk geografi; physical geography; Geology; structural markers; augen gneiss; orthogneiss; migmatite; ion microprobe; Pb-Pb evaporation; U-Pb; geochronology; zircon; Sweden; Mylonite Zone; Western Segment; Sveconorwegian orogen; Eastern Segment; mineralogy; geochemistry; Petrologi; mineralogi; geokemi;

    Sammanfattning : The Mylonite zone (MZ) is a prominent late-Sveconorwegian lithological terrane boundary in the SW Baltic Shield along which large-scale crustal block movements took place during the Sveconorwegian orogeny. The southern section of the MZ also defines a conspicuous metamorphic break separating upper amphibolite and high-pressure granulite facies rocks in the parautochthonous Eastern Segment (ES), from middle amphibolite facies rocks in the overlying Western Segment (WS). LÄS MER

  4. 3. 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

  5. 4. 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

  7. 5. Cryptic Orogeny : uplift of the Al Hajar Mountains at an alleged passive margin

    Författare :Reuben Johannes Hansman; Ring Uwe; Joachim Jacobs; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; uplift; mountains; structural; low-temperature; thermochronology; dating; fission-track; U-Th He; U-Pb; calcite; structure-from-motion; photogrammetry; UAV; trishear; fault-propagation; Hafit; Al Hajar Mountains; United Arab Emirates; Oman; Geology; geologi;

    Sammanfattning : Mountains evolve and grow because of the large forces that occur from the collision of tectonic plates. Plate boundaries change and move through time, and regions that were once stable, shallow-marine environments can be dragged into subduction zones and get transformed into vast mountain ranges. LÄS MER