STREFY ŚCINANIA PODATNEGO NA OBSZARZE ZŁOŻA RUD Fe-Ti-V „UDRYŃ" SUWALSKIEGO MASYWU ANORTOZYTOWEGO

Abstract

DUCTILE SHEAR ZONES FROM THE "UDRYŃ" Fe-Ti-V ORE DEPOSITS OF THE SUWAŁKI ANORTHOSITE MASSIFAbstract. Detailed structural analysis of non-oriented drill cores (ca. 10,000 m) from 12 deep boreholes from the "Udryń" Fe—Ti—V ore deposits area (the Suwałki anorthosite massif, NE Poland) has been carried out. Special attention has been paid to recognition of ductile shear zones in preserved drill cores, probably more than 485 zones, attitudes of the SM mylonitic foliation and the LM extensional (mineral) lineations, and to kinematic indicators. The results of the analysis made it possible to establish the direction of tectonic transport and deformation regimes in individual boreholes and throughout the area of the "Udryń" ore deposits. In general, the dip angle of the SM foliation is about 50-60° with approximately parallel to the dip of the LM stretching lineations. Both the structural elements are inferred to be remnants of the Gothian orogeny (ca. 1.55-1.45 Ga) with shortening and localised ductile thrusting. There are problems in the reliability of the SM foliation orientations using curving axis of individual boreholes. On the basis of the curvature axis it is proposed that the strike of SM foliation is consistent at a regional scale with NW—SE to WNW—ESE directions. Almost all shear sense indicators show reverse sense of movements with the top to the NE. The development of strongly heterogeneous ductile shear zones controlled the distribution and shapes of ore deposits in the vicinity of Udryń. It is quite probable that frequent occurrences of ilmenite-magnetite ores in the vicinity of Udryń are situated mainly in frontal and/or bottom domains of thrust sheets displaced towards the NE. More localised and younger tectonic processes were connected with ductile-brittle and brittle conditions during faulting.