Kaalamo and Velimyaki paleoroterozoic gabbroid massifs of the Northern Ladoga area: thermodynamic modeling of crystallization and evolution trends of igneous rocks

Kaalamo and Velimyaki gabbroid massifs are located in the south-eastern part of Raahe-Ladoga suture zone Karelian craton Sveсofennian mobile belt. These were formed almost simultaneously 1.89 Ga ago, occupy same tectonic position a single unit Early Proterozoic metamorphosed rocks: intrusions contained by supracrustal stratas: garnet-biotite gneisses micaceous shales Ladoga series, as well amphibolites Sortavala series. Despite this, gabbroids compared differ sharply their material composition, especially content alkalis differentiated series rocks. The results thermodynamic modeling magmatic crystallization (Magma Chamber Simulator, MELTS packages) showed that sub-alkaline rocks massif cannot be obtained from magma slightly changing such parameters pressure, water melt, oxygen fugacity. assumption significant difference these for magmas is not confirmed at mineralogical-petrographic level other characteristics ones. effect contamination chamber also does significantly shift trend rock compositions calc-alkaline region to region. Analysis mineral formation two allows us make it possible conclude either various parent melts, or initial melt was one, but underwent with enrichment along migration route until upper crust reached.