Протерозойская спилито-диабазовая формация Имандра-Варзуга на Кольском полуострове / Н. И. Соустов. - Москва : Изд-во Академии наук СССР, 1940. - 63, [2] с., [1] л. к. : ил.

nitegneissic complex. Into the composition of this complex enter mica schists and gneisses, oligoclase gneiss-granites, ampliibolites and microclinic granites. The amount of gabbro-norites and pyroxenites in the region is much less. The gneiss-schist series has a thickness of about 9 km. and is subdi vided into three horizons in ascending order: ( 1 ) the horizon of magmatized gneisses and oligoclase gneiss-granites; ( 2 ) the horizon of fine-grained mica and mica-garnet gneisses, and (3) the horizon of mica-garnet schists. Among the ampliibolites one may distinguish varieties tha t originated probably at the expense of a recrystallization ( 1 ) of large gabbro massifs and ( 2 ) of effusive rocks (amphibolite-mandelsteins). The latte occur mainly among the mica-garnet schists. The Imandra —Varzuga series lies in the narrow geosynclinal depression stretching nearly through the whole of the Kola Peninsula. The axis of this depression in its western part, investigated by the author, is some what raised to the north-west towards the Monclie-Peninsula on Lake Iman dra, due to which in the above direction a wedging out of the series occurs. The contact being insufficiently exposed makes it is impossible to establish the nature of the contact of the greenstone series with respect to the surrounding ancient series of gneisses. But in so far as it is possible to establish from observations, the boundary of these series of different age seems to be everywhere a tectonic one. The rocks of the Imandra —Varzuga series are strongly dislocated and crumpled in a number of fan-shaped folds with steep dips and with an overturning of the limbs of the folds, as it shown in the accompanying sections. The dislocation is especially strongly marked along the southern margin of the greenstone belt, gradually dying out to the north where already relatively slightly metamorphosed rocks are encountered. In the Imandra — Varzuga formation the author distinguishes: (1) igneous rocks and ( 2 ) metamorphosed sedimentary rocks. The igneous rocks belong in time to one eruptive cycle, but the author divides their appearance into three phases: (a) rocks connected with normal sedimentation — pyro- clastic products, amygdaloid lavas, effusive diabases; (b) synorogenic intrusions — intrusive diabases; (c) postorogenic intrusions: metagabbroes, gabbro-diabases, pyroxenites. The sedimentary rocks are represented by a large section, at the base of which occur chlorite-muscovitic and muscovite-biotitic schists with intercalations of quartzites, succeeded further upward by limestones and dolomites, passing in turn into the uppermost horizon of phyllites and coal shales. The thickness of the whole section is 3000—4000 m. The greenstone rocks are encountered in all the horizon of the normal section. The author gives a brief survey of the stratigraphy of the greenstone rocks of Finland and Karelia and reaches the conclusion enat the Imandra — Varzuga series belong to the formations of Karelia age. To the same age the author refers also the albitophyres exposed m a number of places among greenstone rocks. Of more recent age within the series is a large intrusion of alkaline and nepheline syenites near the station Titan, representing a satellite injection closely related to and obviously of the .same age as the Khibina alkaline massif.