Magma types and the tectonic evolution of the Swedish Proterozoic

Abstract

Information on tectonic evolution can be obtained from the succession of magmatic types represented (I-type and S-type granitoids and volcanics, basic dykes and alkali complexes). The earliest Proterozoic magmatic activity resulted in the formation of greenstone belts within the “Karelian” continent area, probably in the age range 2500-2100 Ma. This was followed by an event similar to “Andinotype” orogeny at around 1900 Ma with I-type granitoids and calc-alkaline volcanics. This progressed to an event of “Hercynotype” which was concluded by about 1750 Ma. Subsequent magmatic activity (I-type granitoids and volcanics) suggests a new phase of Andino-type orogeny until about 1630 Ma (S and C Sweden) or 1500 Ma (N Sweden). Tension-related magmatism at around 1550 Ma (basic dykes, alkaline complexes and gabbro) may relate to rifting prior to the independant evolution of SW Sweden which includes intrusion of I-S-type granitoids, metamorphism, followed by continental rotation and collision with N America at about 1050 Ma. Basic dykes and S-type granites are related to subsequent uplift 950-850 Ma ago.