Permskie skały wylewne w południowo-zachodniej części monokliny przedsudeckiej

Elżbieta Siemaszko

Abstract


Na podstawie badań chemicznych i petrogrfaficznych skał wylewnych z SW części monokliny przedsudeckiej wyróżniono kilka typów tych skał, z których wydzielono cztery grupy petrograficzne. Przedstawiono charakterystykę chemiczną i petrograficzną grup, ze szczególnym uwzględnieniem udziału procesów wtórnych przeobrażeń.

Z następstwa typów i grup petrograficznych w profilach badanych otworów wiertniczych wyciągnięto wnioski odnośnie pochodzenia magmy macierzystej.

 

PERMIAN EFFUSIVE ROCKS FROM SW PART OF THE FORE-SUDETIC MONOCLINE

Autunian effusive rocks from SW part of the Fore-Sudetic Monocline were studied. Several new types of these rocks were differentiated using a new classification of effusive rocks proposed by A. Rittmann. Taking into account chemical and petrographic properties and the position on A. Rittmann scheme, the identified rock types were assigned to 4 petrographic groups: trachytes, rhyodacites, dacites and basalts. The groups differ in: 1) chemistry, and mostly in content of alkali and, somewhat, magnesium and iron, 2) petrography, mostly in structures of rocks and groundmass, and type and degree of advancement of secondary alterations.

The present-day diversity of petrographic groups is essentially of the secondary character and the structures represent relics of original differentiation.

Projection of point data of chemical analyses on M. Masao differential triangle indicates secondary saturation of the studied rocks in alkali, which is reflected by their mineralogy.

The identified petrographic types and their succession in lithological profiles are typical of derivatives of tholeitic basalt magma of the Pacific series, sometimes changed in result of contamination. The M. Masao differential triangle displays a shift of the studied rocks from the tholeitiic series field partly on the alkali field but mostly outside it also. This reflects the influence of secondary changes on the present-day appearance of these rocks.

 


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