The extended Northern Kola greenstone belt was formed within the Kola granu
lite-greenstone terrane in the Late Archean. Its lower part consists of vol
canogenic basalt-komatiite sequences metamorphosed to amphibolite facies. T
he most representative and well preserved these rocks were found in the wes
tern part of the belt, in the middle reaches of the Ura, Western Litsa, and
Titovka rivers. The rocks of the komatiite association compose massive and
pillow lavas, differentiated lava flows, horizons and lenses of lava brecc
ias and agglomerate tuffs of variable thickness and length, as well as subv
olcanic bodies. The komatiites and basalts are products of areal subaqueous
eruptions. Volcanic eruptions were accompanied by occasional phreatic expl
osions. The scarce differentiated flows consist of cumulate, spinifex-textu
red, and brecciated zones. Temperature and pressure in the mantle source ar
e estimated as 1734 degrees C and 7-8 GPa, respectively. The temperature of
erupted lavas was about 1520 degrees C. Geochemically, the komatiites appr
oximate the Yilgarn type but show some what lower Al2O3/TiO2 ratio. They ex
perienced intense three-stage metamorphism. The first stage produced serpen
tine-magnetite acid later chlorite-tremolite assemblages with partial prese
rvation of primary magmatic high-Mg olivine. The second stage resulted in t
he local extensive development of olivine porphyroblasts owing to chlorite
breakdown at 650-700 degrees C. The third, retrograde stage caused the form
ation of carbonate and idding-site-bowlingite, The intense carbonation was
responsible for partial redistribution of REE and other elements.