Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Petrology and whole-rock geochemistry of metabasites from borehole cores in the Na Zeleném and Pluhův Bor catchments in the Slavkov Forest, western Bohemia
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Long-term geochemical monitoring of soils and drainage water in three lithologically contrasting catchments in the Slavkov Forest in western Bohemia (Krám et al. 2012) challenged the project team to study also the subsurface variability of basement rocks. Three core boreholes were drilled in the Lysina (granite, LYS-V1), Pluhův Bor (serpentinite, PB-V1) and Na Zeleném (amphibolite, NZ-V1) catchments (Fig. 1). The latter two drill holes provided comparable samples of metamorphosed basic to ultrabasic rock suite belonging to the Mariánské Lázně Complex (MLC) on the triple junction between Saxothuringian, Moldanubian and Teplá-Barrandian regional units. The PB-V1 drill hole on the top of the Pluhův Bor ridge documents a thin serpentinite layer on its top only, and almost 20 m of mixed and highly sheared amphibolites of variable geochemical features with affinity mostly to calc-alkaline subvolcanic suite referred to as the source of some MLC amphibolites and metagabbros. The NZ-V1 drill hole proved mostly Mg-rich tholeiitic nature of retrogressed garnetiferous amphibolite in the Na Zeleném catchment, at the very rim of the MLC. Three parallel intrusions of perpotassic Mg-rich metadiorite (redwitzite) up to few metres in thickness were documented from the NZ-V1 core. These members of the redwitzite group were dated from the locality at 324±4 Ma by Jelínek et al. (2004). Profiles of both the boreholes are given in Tables 1 and 2, selected photomicrographs of serpentinized spinel peridotite/amphibolite/Mg-schist assemblage from PB-V1 drill hole and the amphibolite series with redwitzite intrusions from NZ-V1 are presented in the Figures 2 and 3, respectively. Geochemical features of 23 rock samples (Tab. 3) are projected in selected ternary (Fig. 4) or binary (Fig. 5) plots of the main and trace elements showing principal geochemical features and selected classification indices of both rock series. References
