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Geochemistry and geochronology of mafic intrusions in the northern part of the Carlsbad pluton
Holečková, Pavla
ii SUMMARY In the NW part of Bohemian massif occur small bodies of mafic intrusive rocks. These rocks are called redwitzites and they include various rock types from diorites to quartz gabbros. They are always close to granites OIC (old intrusive complex). They are probably precursors of Late Variscan granitoid magmatism. Small body of redwitzites is situated near Abertamy (7 km NW of Jáchymov) in the western part of Krušné hory Mts. This body is inhomogeneous; it is formed by two types of mafic rocks. Both rocks distinguish in mineralogy and chemistry. First type, biotitic gabronorite, forms the western part of the body, another type, biotitic - hornblende quartz gabrodiorite, forms the NE part. The expressive sign of Abertamy redwitzites are flakes of brown biotite which can be as large as 2 cm. They are often poikilitic. Gabronorite is a fine-grained green-grey rock consisting of orthopyroxene, biotite, feldspar, quartz and hornblende. Most of the mafic minerals are altered to uralite. Accessories are represented by apatite, zircon, monazite, allanite and sphene. From the chemical point of view is gabronorite enriched in compatible elements (Mn, Fe, Mg, Ni, Cr, Sc, V, Ca, Co, Zn, Cu). Gabrodiorite is medium-grained rock and it is collored light gray. Its composition is similar to the gabronorite. It does...
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