Chapter 11 Paleoproterozoic tectonic evolution

Geochronology of the Palaeoproterozoic Kautokeino Greenstone Belt, Finnmark, Norway: Tectonic implications in a Fennoscandia context

“…10E, F) and Vuolgamašvuopmi pluton in the Masi Formation (1865 ± 11 Ma; Fig. 11A) straddle the time interval between c. 1890 and 1860 Ma of synorogenic granitoid magmatism associated with the Svecokarelian orogeny, documented in southern, northern and central Finland (Central Finland granitoid complex; Lahtinen et al, 2005;Nironen, 2005;Korja et al, 2006). More specifically, the age and metaluminous character of the Rietnjajávri pluton links this pluton to the Haaparanta (Haparanda) suite in northern Sweden and Finland.…”

“…This interpretation was already suggested by Olesen & Sandstad (1993). (2) The Ráiseatnu Complex represents a reworked Svecofennian sedimentary-volcanic succession deposited in the c. 1960-1850 Ma time interval, akin to the widespread basins exposed southwestwards in Finland and Sweden in the Svecokarelian orogen (Lahtinen et al, 2005;Korja et al, 2006;Högdahl et al, 2008). This basin is possibly far travelled and unrelated to the Kautokeino Greenstone Belt.…”

“…Accretion was followed by several orogenic and magmatic phases between c. 1890 and 1770 Ma (Lahtinen et al, 2005;Nironen, 2005;Korja et al, 2006).…”

“…1). In a set of synthetic models, Lahtinen et al (2005), Korja et al (2006), and Lahtinen et al (2008Lahtinen et al ( , 2009) unravelled the evolution between these two cratons by using geological evidence from Central Lapland. The new data presented in this paper, however, emphasise the lack of correlation between the Kittilä Group and Čáskejas Formation (Fig.…”

Sm-Nd data for mafic-ultramafic intrusions in the Svecofennian (1.88 Ga) Kotalahti Nickel Belt, Finland - Implications for crustal contamination at the Archaean/Proterozoic boundary

“…Many authors have modelled the evolution of the Archaean/Proterozoic boundary and presented different views on the direction of the possible subduction (e.g. Gaál, 1982Gaál, , 1986Gaál, , 1990Ward, 1987;Ekdahl, 1993;Lahtinen, 1994;Ruotoistenmäki, 1996;Nironen, 1997;Lahtinen et al, 2005). On the basis of the fact that Archaean influence (low ε Nd value) is controlled by the Archaean/ Proterozoic contact at the present erosion level and assuming that the magma conduit in the upper crust was vertical to subvertical, we can assume that the Archaean basement was not present further west at deeper levels during magma ascent at 1880 Ma.…”