The Late Mesoproterozoic Sirdal Magmatic Belt, SW Norway: Relationships between magmatism and metamorphism and implications for Sveconorwegian orogenesis

The U–Pb age of the Finse batholith, a composite bimodal Sveconorwegian intrusion

“…Vander Auwera et al (2011, however, postulated a provenance of the more juvenile component by melting of underplated mafic crust. The second point, the orientation of small intrusive bodies and their local deformation indicating emplacement in a stress regime, is indicative of a compressional setting, a feature already evident by the general N-S arrangement of the plutons on the larger scale of the craton (Coint et al, 2015). These features are in principle compatible with aspects of both models presently under discussion.…”

“…Crustal imbrication and deep burial creating highpressure rocks are also indicative of convergent processes; and they also emphasise the difficulty of achieving ultrahigh-temperature metamorphism, such as is observed in Rogaland at about 1010 Ma, in a 'cold' subduction environment. Coint et al (2015), however, concluded that these ultrahigh-temperature processes were likely of local rather than of regional extent. Slagstad et al (2013a, b) argued, furthermore, that the magmatic and metamorphic record of the western part of the Sveconorwegian orogen is most compatible with long-lived accretionary processes in an Andean-type subduction setting, stressing in particular that there is no direct evidence in that part of the orogen for crustal thickening and collision with another continent.…”

“…Three main plutonic associations have been recognised: (1) the Sirdal Magmatic Belt (SMB), including the Feda-Fennefoss suite, formed between 1060 and 1020 Ma (Bingen et al, 2008(Bingen et al, , 2015Vander Auwera et al, 2011;Slagstad et al, 2013a;Coint et al, 2015); (2) the hornblende-biotitegranitoid suite (HBG), formed between 990 and 920 Ma (Bingen et al, 2008;Vander Auwera et al, 2011); and (3) the anorthosite-mangerite-charnockite suite formed between 950 and 920 Ma (Schärer et al, 1996;Vander Auwera et al, 2011). The SMB is a calc-alkaline, magnesian association whereas the HBG is more alkaline and ferroan (Slagstad et al, 2013a).…”

“…Slagstad et al (2013a, b) argued, furthermore, that the magmatic and metamorphic record of the western part of the Sveconorwegian orogen is most compatible with long-lived accretionary processes in an Andean-type subduction setting, stressing in particular that there is no direct evidence in that part of the orogen for crustal thickening and collision with another continent. The difference in apparent tectonic regimes between the eastern and western domains of the Sveconorwegian orogen may reflect relatively late amalgamation of crustal blocks (Coint et al, 2015). A separate evolution between Telemarkia and the rest of the orogen, and their eventual collision, has been considered before (e.g., Bingen et al, 2005).…”

Laurentia-Baltica-Amazonia relations during Rodinia assembly

“…Ma (see also Coint et al, 2015) within the Telemarkia terrane that they related to ongoing convergence on the margin of Rodinia. Similarly, Bybee et al (2014) agued on the basis of isotopic data from anorthosite and co-magmatic pyroxene megacrysts within the 950-920 Ma…”