Kůstrý ortoruly
General Characteristics
County (administration):
Jihočeský kraj
District (town):
Strakonice
Village:
Nová Ves
Cadastre:
Víska u Strakonic
Map sheets:
22-34 Vimperk, 22-341 Vacov
Accessibility:
entry permit for car necessary
ID:
4235
Geology
Short characteristics of the site:
The location is accessible only on foot, but along a network of well-maintained ice asphalt roads, the best start is from the east of Kváskovice, along the forest asphalt (green tourist sign), you can reach the settlement U Benedy and from there continue on foot. About 100 m from the top of Kůstrý are along the road leading almost flat along the ridge of the rock and abundant blocks of amphibolic to amphibole-biotite orthogneiss with pyroxene, about 100 m before the height of the gazebo (elevation 845 m) begins the body of leucocratic orthogneiss, which continues ridge paths another 600 m. Below the Gazebo also crosses the path of a vein of syenite porphyry, generating large blocks on the slope. At the top of Kůstrý, at the documentation points, a fine-grained (grain size 0.1–1.5 mm), strongly directed and weakly banded pyroxen-amphibolic ortorula with magnetite appears, which in some places passes into sharply separated pegmatoid parts of similar composition. The rock consists of predominant plagioclase (35%) and quartz (about 30%), minor K-feldspar (10%), strongly pleochroic amphibole 15%, light green clinopyroxene 8% and titanite 3%. In some parts, a light red grenade also appears in a proportion of up to several%. The abundant apatite and magnetite, as well as zircon and allanite are accessories. Magnetic susceptibility 3–15 x 10-3 corresponds to the high content of magnetite in the rock; the contents of natural radioactive elements are K = 1.8%, eU = 2.3 ppm, eTh = 12.6 ppm. On the rocks at the elevation of the Gazebo (d. B. SZ653) and further along the road (d. B. SZ654), a fine-grained leucocratic orhogneiss of light gray to almost white appears. The rock has a hypidiomorphically fine-grained to slightly cataclastic parallel-directed structure, sometimes containing quartz bands and a grain size between 0.05–2 mm, in some places it turns into pegmatoid parts of coarser grain size.
Regional geologic unit:
Bohemian Massif > Moldanubicum > Metamorphic units in Moldanubicum > Moldanubicum of Šumava and South Bohemia
Stratigraphy:
Proterozoic - Paleozoic
Subject:
geology, petrology, geomorphology
Geological phenomenon:
rock bag, block field
Genesis:
metamorphic (general metamorphism), frost weathering
Rock:
orthogneiss, pegmatite
Territorial protection
Level of protection:
Registered interesting geological localities
Conflicts of interests:
without conflicts
References
- Žáček V et al. (2021): Vysvětlivky k základní geologické mapě České republiky, list 22-341 Vacov, archiv České geologické služby, Praha
Elaboration and Updating
Elaborated by:
Vladimír Žáček, 23.01.2021
Updated by:
Citation
The database Important geological localities of the Czech Republic: 4235 [online]. Prague: Czech Geological Survey, 1998 [cit. 2023-06-16]. Available from: https:// lokality.geology.cz/4235.
Location in map:
Assessment
Scientifical assesment:
medium
Educational assesment:
middle
Significance:
supraregional
Representativeness:
major
Geological importance:
geo-regional value (mapping)
Excursion locality:
yes
Locality conditions:
no problems
You can send information about a change in the status of the site to lokality@geology.cz
