Sökning: "zircon"

Visar resultat 6 - 10 av 53 avhandlingar innehållade ordet zircon.

1. 6. Crustal evolution of the Arabian–Nubian Shield : Insights from zircon geochronology and Nd–Hf–O isotopes

   Författare :Fitsum Girum Yeshanew; Victoria Pease; Martin J. Whitehouse; Robert J. Stern; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Gondwana; Arabian–Nubian Shield; Azania; zircon U–Pb–O–Hf isotopes; Nd isotopes; Cambrian Sandstones; juvenile; pre–Neoproterozoic; reworking; Geology; geologi;

   Sammanfattning : The Arabian–Nubian Shield (ANS) represents a major site of juvenile Neoproterozoic crustal addition on Earth and documents Neoproterozoic tectonics bracketed by two supercontinent cycles, namely the fragmentation of Rodinia and the amalgamation of Gondwana. There is general consensus that the ANS formed by juvenile magmatic arc accretion and subsequent shield–wide post–tectonic magmatism. LÄS MER

3. 7. The tectonic evolution of northwest Svalbard

   Författare :Carl Henrik Pettersson; Victoria Pease; Robert Strachan; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Svalbard; Rodinia; Laurentia; Zircon; Provenance; Migmatites; Clockwise P-T; Solid earth geology and petrology; Berggrundsgeologi och petrologi; Geology; geologi;

   Sammanfattning : Svalbard represents the uplifted and exhumed northwest corner of the Barents Sea Shelf. Pre-Carboniferous rocks of Svalbard are divided into the Eastern, Northwestern and Southwestern Terranes, were amalgamated during the Caledonian Orogen and are separated by north-south-trending strike-slip faults. LÄS MER

4. 8. Evolution of continental crust in the Proterozoic : growth and reworking in orogenic systems

   Författare :Andreas Petersson; Berggrundsgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; crustal reworking; Proterozoic; O-isotopes; Lu–Hf; U–Pb; zircon; Crustal growth;

   Sammanfattning : To understand the growth of continental crust, the balance between juvenile mantle derived extraction, infracrustal reworking and crustal recycling, needs to be estimated. Since the beginning of the century, the use of coupled in situ zircon U–Pb, Lu–Hf and O isotope analyses as a tool to address these questions have increased exponentially. LÄS MER

5. 9. 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

7. 10. The Prevalence of Radioactivity in a Number of Non-Nuclear Industries

   Författare :Torbjörn Gäfvert; Lund Medicinsk strålningsfysik; []
   Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Kärnfysik; Nuclear physics; zircon; ceramics industry; thorium; TIG welding; waterworks; calcium chloride; dicalcium phosphate; phosphate industry; non-nuclear industries; TENORM; Natural radioactivity; NORM;

   Sammanfattning : Four different non-nuclear industries have been investigated regarding the presence of radioactive elements, with the focus on natural radioactivity. The aim of the studies was to investigate the flow of radionuclides in the processes and/or to estimate doses to exposed workers. LÄS MER