Główne kierunki strukturalne bloku sowiogórskiego

Abstract

Main structural directions of the Góry sowie Block (Sudetes) The Góry Sowie Block is the oldest, Moldamulbian part of the Sudetic structure. It oocupies the 'central position among Proterozoic-Palaeozoic metamorphic series of the Sudetic structure, in relation to which it constitutes a well-defined intermontane massif. It is surrounded with a ring of basite-utlrabasite massifs. The Block is built of migmatites, paragneisses and granitoids. Besides there also occur amphibolites, serpentinites and calcareous-siliceous rocks. Marginal zones of the Block were subjected to cataclasis, manifested by the occurrence (breccias, cataclasites and mylonites). The Sudetic marginal fault — the main Sudetic dislocation — subdivides the Góry Sowie Block into a mountainous part (the Góry Sowie Mts), belonging to the Sudeten and a foremontane one, overlying the Fore-Sudetic Block. The paper present a reinterpretation of the results of mesostructural studies on the fold tectonics of the Góry Sowie Block obtained so far. (Grocholski, 1958a, 1958b, 1961, 1962, 1964a, 1964b, 1966, 1967a, 1967b, 1969, 1975 and a lecture delivered at the meeting of the Polish Geologiсаl Society in Wrocław on 5th May 1968). Grocholski (1969, 1975) distinguished four stages of the fold type of deformation: 1. B0(1) — direction of fold axes N—S, foliation s1 (stratification planes); 2. B1 — direction of fold axes NW—SE, foliation s2; 3. B2 — direction of fold axes NE—SW to EW, foliation s3; 4. B3 — direction of fold axes NNE—SSW, foliation s4. The distribution of fold movements intensity in the foremontane area is shown in Fig. 1. On the other hand, in the mountainous area in the NW part of the Góry Sowie Mts the direction B2 dominates over the B0, and B1 ones. Grocholski (1969) subdivided the region of the Góry Sowie Mts Biock into smaller homogeneous fields (Fig. 2) and constructed separate diagrams of foliation and В-lineation for them. System B0 apart from sporadic observation, it has no documentation. and, despite the author’s reservations, is introduced into the evolution of the Góry Sowie Mts (Grocholski 1967a) and of the whole Block (Grocholski 1969, 1975). System B2 — has been incorrectly distinguished. Its distinction is based on the fact that the strike of foliation, corresponding to the maximum in the diagram, is perpendicular to the lineation (b1) in regions I and II (Fig. 3 and 5, cf. Fig. 6). Grocholski identifies this strike (NE— SW) with the deformation axis B2 (NE—SW) and denotes the foliation itself with the symbol s3 (considering that it overlaps s2). However, even if the foliation s3 were present, it would form the same girdle as s2, and the possible axis B2 does not run in the NE—SW direction but overlaps B1 and may this be identified with it. System B3 — is connected with the eastern marginal zone. It is characterized by mylonitization. Preserved relic fragments, showing no deformation phenomena, have their foliation consistent with the new mylonitic foliation (Fig. 8), and their lineation has the SE direction (it did not undergo rotation at the time of B3 deformation — Fig. 9). The main fold structures were formed during one folding, event which is indicated by a structural conformity of foliation and lineation (Fig. 3—5, 10—15). Axes of these structures have a constant orientation (125/35) in three fourths of the area (Fig. 16). Only in the NW part there occur NE directions which pass gradually, through parallel directions, into SE ones in the region of the Wielka Sowa Massif. In the earlier period, when metamorphic series were folded around the Block, the latter behaved as a stable fragment and did not undergo folding. On the margins of the Block only mylonitization could be observed, while the interior was faulted.