Przedgranitoidowy semilamprofir z Rogówka (kłodzko-złotostocki masyw granitoidowy)

Abstract

Opisano pozycję geologiczną, cechy petrograficzne i petrochemiczne żyły semilimprofiru z Rogówka koło Ołdrzychowic Kłodzkich w Sudetach Środkowych. Żyła ta przecina gnejsy osłony granitoidów kłodzko-złotostockich tworzące wtrącenia w granitoidach. Tworzy ona także bryłowate enklawy występujące w granitoidach. Pozycja geologiczna żyły obserwowana w kamieniołomie, jak również szereg faktów pośrednich tektonicznych i petrograficznych wskazują na jej przedgranitoidowy wiek.PRE-GRANITOID SEMI-LAMPROPHYRE AT ROGÓWEK (KŁODZKO-ZŁOTY STOK GRANITOID MASSIF)Lamprophyre veins recorded in the Kłodzko - Złoty Stok massif, central Sudety Mts, were hitherto regarded as post-granitoid and differentiation in their chemical composition was explained in terms of contamination of magma of the spessartite composition. The studies carried out by the author have shown the presence of semi-Iamprophyre vein older than the Kłodzko - Złoty Stok granitoids in quarry at Rogówek near Ołdrzychowice Kłodzkie (Fig. 1). The vein, with composition corresponding to that of quartz, alkaline-feldspar syenites, is cutting enclaves of biotite gneisses/embedded in granitoids and it forms block-like enclaves in the latter. The geological setting of the vein in the quarry and several indirect tectonic, petrographic .and chemical premises suggest pre-granitoid age of the semi-Iamprophyre.Vein rock from Rogówek is primarily built of microcline and clinoamphiboles close to hornblende in nature and characterized by needle-like appearance of crystals, as well as quartz, chlorites, titanite, leucoxene, apatite and iron oxides. It is characterized by strong, diablastic intergrowths of K-feldspar and c1inoamphiboles and intense K-feldspar blasts.Chemical composition of Rogówek semi-Iamprophyre (Tables 1-2) is markedly different of that typical of post-granitoid lamprophyres, represented by lamprophyre from Ołdrzychowice. It is somewhat similar to that of alkaline varieties of vein rocks of the K-differentiation series, recognized in NE part of the Bohemian Massif by D. Nemeč (1975, 1977).