Tektonika uskokowa cokołu krystalicznego platformy prekambryjskiej w Polsce

Abstract

 W skałach podłoża krystalicznego zaznaczyły się trzy style tektoniki uskokowej: prekarelski – najsłabiej zaznaczony, uwarunkowany biegiem stref fałdowych (uskoki równolegle i prostopadle do biegu) oraz kolistymi masywami granitoidowymi (uskoki koncentryczne); karelski - dobrze zachowany, o kierunkach południkowych i równoleżnikowych; prewendyjski - najsilniejszy, równoległy i prostopadły do linii Teisseyre'a-Tornquista (NW-SE i NE-SW). Styl tektoniki uskokowej wpływał na rozwój granityzacji, magmatyzm gotyjski i platformowy.

FAULT TECTONICS OF CRYSTALLINE SOCKLE OF THE PRECAMBRIAN PLATFORM

IN POLAND

Crystalline basement of Polish part of the East-European Plaftorm has been formed in a number of tectonic cycles. It consists of pre-Karelian central granitoid massifs separated with fold zones. Disharmonically folded Karelian rocks resting on deeply peneplenized pre-Karelian basement, were subjected to erosion and they are preserved in some areas only. Gothian transfomations were here connected with strong granitization and migmatization of rocks. Rocks of the quasiplatform complex are younger than the above, and those of platform intrusions the youngest here.

Metamorphic rocks of individual fold zones are characterized by specific style of fault tectonics.

Faults parallel and normal to the strike of structures predominate in these zones. The fault tectonics of the central (Masovian) granitoid massif appears completely different, being characterized by predominance of concentric faults.

A system of deep longitudinal and latitudinal faults is related to Karelian movements. Traces of that system are best preserved in the Mazury zone and at its contact with the Podlasie and Ciechanów zones and Masovian massif. Karelian faults markedly facilitated origin of anorthosite massifs and they accelerated granitization of substratum in the Mazury zone, where rapakiwi-like granitoids have been forming on great scale.

The direction NE-SW, predominating at the contacts of the Kaszuby, Ciechanów and Podlasie (southern part) fold zones and granitoid massifs, is of special importance here. It is evidenced by a high geophysical gradient and the presence of mylonitized zones and Gothian granitoids. It may represent direction of the inferred pre-Vendian strike-slip movements which could result in translocations of structural elements at distances not greater than 50 km. Much stronger strike-slip movements have taken place in the crystalline basement in Byelorussia. The movements have proceeded at the contact of the Okolov Series and Byelorussian-Peribaltic granulite zone which passes to SW into the Lublin zone in the area of Poland. The movements of these units resulted in translocation of structural elements at distance up to 200 km.

Granitizing emanations healed old fault zones and they resulted in homogenization of deep crystalline basement which nowadays almost do not vary in granitic composition down to the depth of 10 km. Tectonic fractures acted as zones most favourable for migration of granitizing matter but they were also very easily to heal. Therefore, it appears fairly probable that the tectonic pattern of the crystalline basement has been shaped by longitudinal and latitudinal Karelian faults, especially the pre-Vendian ones which are set parallel and normal to the Teisseyre-Tornquist zone (NW-SE and NE-SW).