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Svojšín - outlook summerhouse

The instruction trail „Svojšínské spilitové skály“ (Svojšín spilite rocks), which belongs to the Czech – Bavarian geopark, has been opened in June 2006. It has 13 stays and is 1.6 km long. Start of the trail is at the palace in Svojšín and the end is at spilite rocks above river Mže.

Svojsin spilitte

At the end there is an outlook summerhouse in the top point on a rock promontory above the river. Spilite is the common term for fine-grained basic magmatic rocks, which formed mainly by metasomatism from oceanic basalts and belong to ophiolite formation. Spilites form smaller bodies, veins and especially effusions in form of pillow lavas. They have green-gray, greenish or red-brown to black color.

Mikroskopicthin section of spillite

Visually is spilite similar to basalt. It is often filled by veinlets of calcite or chaldcedony, and has frequently an aphanitic, amygdaloidal texture with cavities filled by secondary minerals. Differences between spilite and basalt are not apparent until examination of a thin-section in microscope. Characteristic minerals of spilites are albite and chlorite, further actinolite, olivine, titanite, carbonates, epidote, prehnite, limonite, also relicts of pyroxenes can be present. Formation of spilites is explained by primary crystallization during the final phase of magma solidification, or by secondary transformation of basaltic lavas by so-called spilite reaction. This includes replacement of basic plagioclase by albite, and enrichment of the rock in sodium, water and carbon dioxide together with lowering aluminium-, potassium- and calcium contents. Thus the transformation proceeds as a consequence of action of residual solutions (so-called autometamorphism), or of seawater (which is rich in sodium), on the original lava. The process leading to spilite formation is called spilitization. The term “spilite“ was introduced in the year 1827 by Alexandr Brongniart. At present the term “metabasalt” is used. The Stříbro-Plasy spilite band is exposed in a mighty rock defile, whose cliffs reach 55 meters in height. In the whole Neoproterozoic unit outcrop several spilite strips of NE-SW direction. The strip here has NE elongation, inclination 30°-40° to the SE and it is markedly morphologically modeled by a deep meander of river Mže.

Look on Sovjšín

Look at valley of the river Mze

Svojsin_altan.avi [123 kB]

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Caption: Svojsin_altan.avi

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GPS position

N 49° 46.101', E 12° 55.608'