Foto: Růždí - Devils anvil
Maleč - Čertova kovadlina,
Porphyry is atypical, darker than the usual type with a fine-grained matrix and with irregularly interspersed sporadic phenocrysts of potassium feldspar up to 1 cm, phlogopite accumulations reach 4 mm. The cracking is sparse into large blocks, one of which forms said anvil.The rock structure is hyautomorphically omnidirectionally grained, the approximate composition is K-feldspar 35%, plagioclase 30% phlogopite 20%, pseudomorphisms after ortopyroxene and / or olivine 10%, clinopyroxene 2%. As an accessory, long prismatic apatite and zircon are very abundant, ilmenite is rare, xenomorphic pyrite is abundant, rarely with the inclusion of chalcopyrite. Secondary is actinolite, serpentine minerals and fine-grained talc. K-feldspar forms idiomorphic phenocrysts up to 5 mm, and is also in the matrix together with plagioclase. Abundant brown phlogopite is isometric to shortly prismatic, often with abundant prismatic apatite, often hexagonal tables, 0.1–2 mm in size. There are abundant 1-2 mm large brown isometric pseudomorphoses or after ortopyroxene or partly after olivine, completely pushed by a mosaic of secondary minerals. Compared to the typical syenite porphyry, there are no large KF phenocrysts and there are fewer, amphibole outgrowths, and in addition there are abundant pseudomorphoses in the rock.Gamma spectrometrically determined contents of natural radioactive elements, especially uranium, are high (average of 2 measurements): K = 4.9%, eU = 17.5 ppm, eTh = 33.7 ppm, magnetic susceptibility varies in the range of 0.18–0, 24 x 10-3. | Žáček, Vladimír | 2015
Base information
Photo localization
WGS84:
49.1703092633,
13.6929486451
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Photo linksThemeChronostratigraphyRegional geologyRockGeological phenomenonLinked recordsImportant geological locality© Photo: Vladimír Žáček, 2015Autorská práva k tomuto snímku nevlastní Česká geologická služba. Cite of the archive photo No: 30992ŽÁČEK, V. (2015): Foto - Růždí - Devils anvil.
In: Fotoarchiv České geologické služby [online databáze]. Praha, Česká geologická služba [cit. 2024-05-01].
Dostupné z URL http://www.geology.cz/foto/30992
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