COMPLEX INTERPRETATION OF SEISMIC AND DENSITY ANOMALIES OF UPPER CRUST OF THE KHIBINY AREA (NW RUSSIA)

Abstract

The study area is located in the central part of the Kola Peninsula and represents a part of tectonically compound terrane, consisting of the AR, PR and PZ geological structures of the East of Fennoscandian shield (NW Russia). The Khibiny massif (PZ) intrudes the Archean complexes (the Northern contact) and the Paleoproterozoic volcanosedimentary Imandra-Varzuga complex (Southern and SW-contacts).The results of the 3D seismic and density modelling showed two correlated local high-velocity and highdensity anomalies with dimensions of 5 x 10 km approximately in central part of the Khibiny massif and close to contact with Imandra-Varzuga sedimentary-volcanic complex. The first anomaly cannot be explained by substance factor only (titanomagnetite-apatite ore bodies), as it has a structural disconformity to general structure of the pluton. The zone of abnormally high tectonic stress is the best explanation for this anomaly. Based on the properties of typical rocks and geological structure of the region the second anomaly is well interpreted by large layered intrusion of Fedorova-Pana type, subsurface of which is cut by Khibiny massif. Thus we forecast big “blind” (not outcropping) PGE-bearing layered intrusion, the upper part of which was cut during the magma intrusion of the Khibiny pluton.