International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Petrology and geochemistry of a peridotite body in Central- Carpathian Paleogene sediments (Sedlice, eastern Slovakia) Introduction and brief geological background

Pages: 387 - 399

Authors: MATÚŠ KOPPA, FRIEDRICH KOLLER, MARIÁN PUTIŠ

Abstract: We studied representative samples from a peridotite body situated NE of Sedlice village within the Central- Carpathian Paleogene sediments in the Central Western Carpathians. The relationship of the peridotite to the surrounding Paleogene sediments is not clear. The fractures of the brecciated peridotite margin are healed with secondary magnesite and calcite. On the basis of the presented bulk-rock and electron microprobe data, the wt. % amounts of mineral phases were calculated. Most of calculated “modal” compositions of this peridotite corresponds to harzburgites composed of olivine ( ~ 70—80 wt. %), orthopyroxene ( ~ 17—24 wt. %), clinopyroxene ( < 5 wt. %) and minor spinel ( < 1 wt. %). Harzburgites could originate from lherzolitic protoliths due to a higher degree of partial melting. Rare lherzolites contain porphyroclastic 1—2 mm across orthopyroxene (up to 25 wt. %), clinopyroxene ( ~ 5—8 wt. %) and minor spinel ( < 0.75 wt. %). On the other hand, rare, olivine-rich dunites with scarce orthopyroxene porphyroclasts are associated with harzburgites. Metamorphic mineral assemblage of low-Al clinopyroxene (3), tremolite, chrysotile, andradite, Cr-spinel to chromite and magnetite, and an increase of fayalite component in part of olivine, indicate low-temperature metamorphic overprint. The Primitive Mantle normalized whole-rock REE patterns suggest a depleted mantle rock-suite. An increase in LREE and a positive Eu anomaly may be consequence of interactive metamorphic fluids during serpentinization. Similar rocks have been reported from the Meliatic Bôrka Nappe overlying the Central Western Carpathians orogenic wedge since the Late Cretaceous, and they could be a potential source of these peridotite blocks in the Paleogene sediments.

Keywords: peridotite, petrology, geochemistry, Slovakia

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