Pozycja petrologiczna i geologiczna granitu z Bugaja

Abstract

Petrologic and geologic position of the Bugaj granite Recent investigations in the Cieszyn-Rzeszotary region (Western Polish Carpathians) have shown that the accumulation of granitic blocks and klippen occurs as an accumulation among formations of the Sub-Silesian Nappe at Bugaj, near Kalwaria Zebrzydowska (Figs. 1, 2). The accumulation is composed of tectonically detached blocks, torn from the crystalline basement by the overthrust Sub-Silesian Nappe and then dragged up to the present location. The place of origin of those blocks is far to the south, where Jurassic strata were deposited “directly on the crystalline base” (Książkiewicz, 1956). Exact localization of the area may be accomplished only by means of a deep drilling project. Examination of so called “exotics” occurring in the various flysch series, is not sufficiently precise to permit detailed conclusion on the basement composition of nappes in the inner part of the Carpathians. The results of work on the origin of the metamorphic complexes occurring under the overthrust Flysch Carpathians in the Cieszyn-Rzeszotary region (Heflik, Konior, 1971, 1974) indicate the relation of those formations to Precambrian sediments of the forelands; the origin of the former is due to metamorphism of the sediments. On the other hand, the results outlined above demonstrate a connection between the metamorphised strata with crystalline rocks of the Goryczkowa tectonic outlier in the Tatra Mountains, Central Carpathians (Heflik, Konior 1974b), described in detail by Burchart (1970). All these factors are remeniscent of the problem of the so called “Bugaj granite” . Detailed pétrographie study revealed that the “Bugaj granite” , a big exotic block recognized by Kreutz (1928) as a rock of magmatic origin is, according to recent criteria, a metamorphic — metasomatic granitoid, similar to pre-Devonian granitoids of both the Cieszyn-Rzeszotary region and the Tatra Mts. The characteristics of the Bugaj granitoid are: a porphyro-glomeroblastic texture, a partly preserved banded structure and numerous mineral relics composed of quartz, apatite, zircon and plagioclase. In texture the “Bugaj granite” shows a strong resemblance to the granitoids penetrated by bore-holes in the Cieszyn-Rzeszotary region (Kęty 7, Kęty 8 , Kęty 9). Both have a porphyro-glomeroblastic texture; this type of texture is better developed in the granitoids from the Kęty boreholes. On the basis of relict mineral and textural features, Heflik, Konior (1974) found a similarity between metamorphic complexes from the basement of the Cieszyn-Rzeszotary region and rocks of the Goryczkowa tectonic outlier in the Tatra Mts. Since there are certain analogies between the “Bugaj granite” and the granitoid formations penetrated in the Kęty region and, partly, those of the region of the Koszysta and the Pięciu Stawów valley in the Tatra Mts., then the “Bugaj granite” , as well as the granitoids from the Cieszyn-Rzeszotary region and from the Tatra Mts., belong to a common petrogenetic family. They are all granitoids, formed by means of processes, mainly of a metamorphic-metasomatic character. A somewhat individual character of the Bugaj granitoid is a function of the different location of its orginal occurrence, slightly different conditions of metamorphism and granitization and differences in the primary composition of the deposits, which had been changed by metemorphism and metasomatic processes. The genetic relationship of these factors was discovered by Heflik, Konior (1974).