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Petrography, geochemistry and post-eruption phenomena of the olivine-poor apatite nephelinite from the Slánská hora Hill
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The columnar jointing of the Slánská hora olivine-poor apatite nephelinite suggests single-phase effusion in the form of a lava lake filling a former phreatomagmatic crater. Unusual petrography with abundant apatite microphenocrysts is consistent with geochemical data. Pseudomorphic calcite replaced olivine during extensive carbonate metasomatism, resulting in Cr and Ni loss. A steep trace element pattern is documented by high chondrite-normalized La/Yb of 26; together with modest anomalies in HFSE and LILE and the absence of Eu anomaly these observations point to low-degree partial melting of enriched source with crystal fractionation of nepheline and without plagioclase segregation, underscored by high Zr/Hf paralleled by relatively low Sc, as well as Nb/U and U/Pb ratios, typical of oceanic basalts.References
