Petrology and geochemistry of mafic intrusions in the Western Krušné hory pluton in the vicinity of Abertamy and Mariánské Lázně

 

Emil Jelínek, Wolfgang Siebel, Václav Kachlík, Miroslav Štemprok, František Holub, Pavla Kovaříková

Geoscience Research Reports 37, 2004 (GRR for 2003), pages 109–111

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Abstract

Small mafic plutonic bodies (to about 1 km sizes) spatially associated with the granites of the Western Krušné hory pluton were studied in the W Krušné hory Mts./Erzgebirge (Abertamy) and Slavkovský les (Mariánské Lázně and Kynžvart). Most of them are well comparable with the so-called redwitzites described from Oberpfalz in Germany. They range from gabbronorite and gabbro to quartz diorite and melagranodiorite compositions. In a great majority of samples, primary mafic minerals, i.e. orthopyroxene, clinopyroxene and in some places also olivine, are replaced by uralitic amphiboles of actinolite to magnesio-hornblende compositions and by serpentine. Presence of large poikilitic biotite (phlogopite) flakes up to 1 to 2 cm in diameter gives them the appearance specific for redwitzites from the classical locality. Chemical composition is variable but high contents of MgO, increased contents of K2O and of many incompatible trace elements are characteristic. The most primitive mafic varieties of these rocks from Abertamy and Kynžvart have MgO up to 13-18 wt% and strongly increased contents of Ni, Cr, V, and Co. Other less mafic rocks, namely from the Mariánské Lázně area, correspond more closely to redwitzites described from the Leuchtenberg area (Germany). According to the single-zircon dating (done at the University of Tübingen) the mafic rocks from Abertamy and Mariánské Lázně have the ages from 322.4 ± 2.9 Ma to 324.8 ±3.0 Ma. These ages are undistinguishable from the single-zircon age of biotite granite from Abertamy belonging to the Older Intrusive Complex (OIC) of the W Krušné hory pluton.