Wulkanity permskie Gór Suchych w niecce śródsudeckiej
Abstract
Permian volcanites of the Suche Mts. in the Intrasudetic Basin
Abstract
A petrographic and chemical description is given of the-Middle Rotliegendes volcanites encountered in the Suche Mts. range, south of the town of Wałbrzych (Central Sudetes). Among these rocks, in the geological literature known under the name of melaphyres, orthophyres, porphyrites and porphyries, the writer has differentiated trachybasalts, latites, rhyolites and pyroclastic rhyolitic rocks represented by tuffs and ignimforites. In the course of three successive volcanic cycles the lava eruptions have supplied two basic rock varieties, i. e. the trachybasalts and the rhyolites or rhyolitic tuffs. During the second volcanic cycle the eruptions of trachybasalts were attended by powerful effusions of latite magmas.
Plagioclases of the volcanic rocks are characterized by transitional optics, between high- and low-temperature. Similar optical properties are displayed by alkali feldspars, the anorthoclase latites excepted, since these commonly display high-temperature optics.
The trachybasalts and latites have yielded to strong autohydrothermal transformations consisting in the albitization of basic plagioclases and the chloritization and riebeckitization of pyroxenes and olivines. Secondary albites stand out by special optical properties, namely a negative and a rather rare poorly positive optic sign, and transitional optics between high- and low-temperature, grading into low temperature optics. Trachybasalts from the Suche Mts. have many petrochemical analogies in common with the Permian melaphyres and diabases of the Cracow region, also with the tholeiites of the Saar Nahe area.
In the present paper reference is made to 52 chemical analyses of volcanites from the Suche Mts., supplemented by 11 chemical analyses and 53 planimetric analyses made by the writer himself.