Baltic Shield - Kola Province

Kola Province

The Archaean Kolmozero-Voronja greenstone belt is located on the Kola Peninsula between Murmansk, Central Kola and the Keivy terrains of Upper Archaean age. Four suites are distinguished in the greenstone belt:

Ljavozerskya (lower terrigenous formation), Polmostundrovskya (komatiite-tholeiite), Voronjatundrovskya (basalt-andesite-dacite) and Chervurtskya (an upper terrigenous formation). Zircon in the quartz of the upper part of the Voronjatundrovskya suite yield an U-Pb age of 2.8 Ga. This is interpreted as the intrusive emplacement of the quartz porphyry during the final stage of the belt development. Ovoid plagioamphibolites are present among schistose plagioamphibolites of the Polmostundrovsky suite and have been dated at ~2.6 Ga, indicative of andalusite-sillimanite facies metamorphism. Tourmaline granites are found all over the Kolmozero-Voronja belt occurring among volcanogenic sedimentary rocks with good correlation dating of 2520±70 Ma. (Kudryashov, 1999).

The geochronological data document a long and complicated evolution of the belt:

• 3.0–2.9 Ga formation of a mafic volcanic sequence and its probable magmatic analogue, a ~2.9 Ga old gabbro,
• 2.9–2.8 Ga formation of intermediate and felsic volcanic rocks with an upper age limit of ~2.83 Ga,
• 2.7–2.6 Ga granodiorite intrusions and their vein analogues,
• and 2.6–2.5 Ga intrusion of postkinematic tourmaline and microcline granites. (Kudryashov, 2001).

Within the Murmansk block, from west to east, there is an increase in the rare earth elements (REE) content in the initial melts, a change in composition of protoliths from tholeiite with the highest content of REE to subalkaline basalt, and in the eastern part of the Murmansk block the REE content is even higher. The origin of tonalites and trondhjemites (TT) is most likely the result of partial melting of mafic sources. The increase of alkalinity in the protoliths of TT-gneisses correlates with the abundance of the Late Archean peralkaline (2750±50 Ma) and alkaline (2760±60 Ma) granite massifs here. (Turkina and Vetrin, 1999).