Przeobrażenia egzo- i endokontaktowe związane z cieszynitami Karpat fliszowych Polski

Abstract

EXO- AND ENDOCONTACT ALTERATIONS CONNECTED WITH TESCHENITES OF THE POLISH FLYSCH CARPATHIANS

Summary

Some misconceptions have arisen from previous statements and oversimplifications of the problem of age, mode, and environmental conditions of the teschenite intrusions in the Polish Flysch Carpathians. This is evidenced, for example, by the assumptions deeply rooted in the Polish literature that no significant contact-metamorphic changes occur around the teschenite bodies. Present research conducted on the best exposed natural and artificial exposures in the vicinity of Żywiec, Bielsko, and Cieszyn reveals that the contact-metamorphic alterations are not restricted to decalcification of marls and recrystallization of limestones into marbles only. The paragenetic contact-metamorphic assemblages have been found grossularite - dolomite - calcite - sericite - chlorite, and also diopside - albite - sanidine - qartz - dolomite. The grossularite from Goruszka quarry near Grodziec originated by gradual replacement of chlorite-sericite segregations. This process was followed by post-magmatic hydrothermal action such as dolomite metasomatism of limestones. The lime garnets with 10 to 36 per cent of andradite molecule occur in the form of euhedral dodecahedrons and perimorphs. The greater admixture of clayey minerals in original rocks, for example marls, favoured the formation of diopside-feldspar hornfels. The scarcity of dolomite and quartz indicates that the reaction: CaMg(CO₃)₂ + 2SiO₂ = CaMgSi₂O₆ + 2CO₂ attained equilibrium shifted to decarbonation products and CO₂ escape. Both examples mentioned indicate, considering the experimental data, the temperatures of 400-500°C in the neighbourhood of the contact. In the neighbourhood at the magmatic body at Hałcnów (near Bielsko) there occur three, nearly 1 cm thick, intercalations of mixed volcanoclastic-sedimentary rocks amidst the upper Teschen shales. According to the author’s determinations the appearance of the same basaltic augite, aegirine, lamprobolite, apatite, sphene, and other minerals as in the intrusions mentioned, adequately proves the Lower Cretaceous age of the teschenite magmatism.