Anders Scherstén
Universitetslektor
Formation of Archean continental crust constrained by boron isotopes
Författare
Summary, in English
The continental crust grew and matured compositionally during the Palaeo- to Neoarchean through the addition of juvenile tonalite-trondhjemite-granodiorite (TTG) crust. This change has been linked to the start of global plate tectonics, following the general interpretation that TTGs represent ancient analogues of arc magmas. To test this, we analysed B concentrations and isotope compositions in 3.8-2.8 Ga TTGs from different Archean terranes. The 11B/10B values and B concentrations of the TTGs, and their correlation with Zr/Hf, indicate
differentiation from a common B-poor mafic source that did not undergo addition of B from seawater or seawater-altered rocks. The TTGs thus do not resemble magmatic rocks from active margins, which clearly reflect such B addition to their source. The B- and 11B-poor nature of TTGs indicates that modern style subduction may not have been a dominant process in the formation of juvenile continental crust before 2.8 Ga.
differentiation from a common B-poor mafic source that did not undergo addition of B from seawater or seawater-altered rocks. The TTGs thus do not resemble magmatic rocks from active margins, which clearly reflect such B addition to their source. The B- and 11B-poor nature of TTGs indicates that modern style subduction may not have been a dominant process in the formation of juvenile continental crust before 2.8 Ga.
Avdelning/ar
- Berggrundsgeologi
Publiceringsår
2019-11-14
Språk
Engelska
Sidor
23-26
Publikation/Tidskrift/Serie
Geochemical Perspective Letters
Dokumenttyp
Artikel i tidskrift
Förlag
European Association of Geochemistry
Ämne
- Geology
- Geochemistry
Nyckelord
- TTG
- archean
- B isotopes
- crust formation
- continental crust
- trace elements
- archean tectonics
Aktiv
Published
ISBN/ISSN/Övrigt
- ISSN: 2410-3403