3D geological and potential field modelling of the buried alkaline-carbonatite Tajno massif (East European Craton, NE Poland)

Abstract

Geological and geophysical data are used to model the 3D geometry of the Tajno alkaline massif intruded during the Early Carboniferous in NE Poland. The massif consists mainly of pyroxenite, mafic intrusive and volcanic rocks, and carbonatites containing rare earth elements (REE) and other important mineral resources. The deep structure of the massif, and its thickness, shape and internal structure, has been poorly known making it impossible to properly search for useful mineral resources. In order to better constrain the distribution, geometries and relationships between the main rock types, a 3D geological model of the Tajno massif has been developed. The input data comprise a set of geological cross-sections built on an updated subsurface geological map, and borehole, magnetic and gravity data. 3D Geomodeller software was applied to integrate geological data into a coherent and geologically feasible model of the massif using geostatistical analysis. The magnetic and gravity data were used to constrain the 3D geological modelling results. The final 3D model is thus compatible with the geological data, as well as with geophysical data. The most important conclusions obtained from the modelling are as follows: (i) a higher proportion of nepheline syenites or tuffs and pyroclastic breccia in relation to pyroxenites; and, (ii) a smaller proportion of chimney breccia relative to chimney-hosted tuffs and volcanic breccia than proposed in previous geological interpretation. These results are important for further studies on the evolution of the Tajno massif and its associated carbonatites.