Charakterystyka petrograficzna i geochemiczna law bazaltoidowych rejonu Bogatyni

Abstract

Przedstawiono wyniki badań trzeciorzędowej formacji wulkanicznej rejonu Bogatyni (niecka żytawska), oparte o badania mikroskopowe i chemiczne 19 próbek law. Wyróżniono sześć odmian law występujących w badanym rejonie: nefelinit oliwinowy, fonotefryt, mugearyt zbliżony do bazaltu toleitowego, mugearyt, trachit kwarcowy zbliżony do latytu, oraz trachit. Na podstawie obserwacji terenowych oraz metod przekształceń analiz chemicznych ustalono stopień zdyferencjonowania poszczególnych odmian lawy dla określenia szeregu dyferencjalnego.

PETROGRAPHIC AND GEOCHEMICAL CHARACTERISTICS OF BASALT LAVAS OF THE BOGATYNIA REGION

The paper presents results of petrographic and geochemical studies on Tertiary volcanic formation from the vicinities of Bogatynia (Żytawa Basin) at the background of regional geological structure of this area. On the basis of microscopic studies on 19 samples of volcanic lavas from south-eastern margin of the Żytawa Basin and conversions of results of chemical analyses into mineral composition, carried out with the use of the A. Rittmann method, the Authors identified 6 varieties of the Javas: olivine nephelinite, phonotephrite, mugaerite similar to tholeiitic basalt, mugaerite, quartz trachyte similar to latite, and trachyte.

The method of conversion of results of chemical analyses was used to evaluate hypothetical degree of differentiation of the studied volcanic series. This made it possible to assign lavas of the olivine ne-phelinite type to primary magma melts, presumably formed in result of melting of Upper Mantle peridotites. Phonotephrites, mugaerites similar to tholeiitic basalt, and mugaerites were assigned to magma melts somewhat modified by fractional differentiation. In turn, quartz trachyte similar to latites, and other trachytes may represent most strongly differentiated igneous rocks and they seem to be also affected by some other process leading to a change in their chemical composition. The results of petrographic and geochemical analyses and field studies suggest that evolution of Tertiary volcanic formation of the vicinities of Bogatynia was taking place in several phases. Petrographic and geochemical character and structural setting suggest that the volcanic complex of the Żytawa Basin is genetically related to tectonic·vo1canic zone of the Ohre Tertiary continental rift.