Microstructures of shear zones from selected domains of the Western Tatra Mountains

Abstract

1 In sti tute of Geo log i cal Sci ences, Jagiellonian Uni ver sity, Oleandry 2a, 30-063 Kraków, Po land Kania, M., 2015. Micro struc tures of shear zones from se lected do mains of the West ern Tatra Moun tains. Geo log i cal Quarterly, 59 (4): 679-699, doi: 10.7306/gq.1243The pa per is fo cused on the meso-and microstructural char ac ter is tics of se lected shear ing zones in the West ern Tatra Mts. The do mains of crys tal line rocks stud ied (D³ugi Up³az Ridge, Rakoñ Mt., Zabraty Ridge and Zabraï Pass, Wo³owiec Mt., Trzydniowiañski Wierch Mt., Czubik Mt. and Jarz¹bczy Wierch Mt.) show ev i dences of het er o ge neous shear ing with de velop ment of shear zones. Four types of shear zones were dis tin guished: (1) duc tile shear zones in gneiss es, (2) brit tle-duc tile com plex shear zones, (3) gneiss es with clear later brit tle de for ma tion, (4) leucogranites, pro duced by anatexis with later brittle de for ma tion. The de vel op ment of these shear zones is char ac ter ized by oc cur rences of var i ous types of fault rocks: cataclasites, S-C cataclasites and mylonites. The dif fer ent shear ing-re lated rocks and struc tures are in ter preted as an ef fect of protolith di ver sity and strain par ti tion ing. Shape-pre ferred ori en ta tion is an im por tant struc tural fea ture of all the shearing-re lated rocks. Ki ne matic anal y ses re vealed gen er ally a south ward sense of shear ing doc u mented by struc tures re lated to brit tle con di tions and north wards sense of shear ing rec og nized in ductily sheared crys tal line rocks. The time re la tion ships be tween dif fer ent shear zone types are dis cussed, lead ing to the con clu sions that the 1st type of shear zone is pure Variscan, the 2nd type is Variscan with Al pine brit tle de for ma tion, and the 3rd and 4th types are mainly Al pine brit tle de for mations of Variscan syntectonic anatectic leucogranites.