Hydroxyapofylit-(K) z kamenolomu Těchlovice u Děčína (Česká republika)

Abstract

One xenolith of a contactly metamorphosed feldspar-hydroxyapophyllite hornfels from basaltic volcanite of the active quarry in Těchlovice village near-by the town of Děčín has been investigated. Its main components are represented by K-feldspar and hydroxyapophyllite-(K), which was hitherto reported from a single locality only in the territory of the Czech Republic. It forms grains up to 2 mm in size tightly associated with K-feldspar and subsidiary quartz, pyroxene (aegirine, enstatite-ferrosilite and diopside) and titanite. The unit cell parameters of hydroxyapophyllite-(K), derived from the powder X-ray data, are a = 8.975(4), c = 15.8371(3) Å and V = 1275.6(5) Å3. Chemical analyses correspond to the empirical formula K0.93Ca3.75Si7.87O20(OH0.96F0.04)·8 H2O. The xenolith originated by a comparatively weak contact metamorphic effect of the basaltic magma to a marly sediment under high partial pressure of H2O. Among xenoliths of North Bohemian Cainozoic volcanites the rock represents a rarity, which has not been known hitherto.