Geochemistry and Sr, Nd isotopic composition of the Hronic Upper Paleozoic basic rocks (Western Carpathians, Slovakia)

The paper presents new major and trace element and first Sr-Nd isotope data from selected lavas among the Permian basaltic andesite and basalts of the Hronicum Unit and the dolerite dykes cutting mainly the Pennsylvanian strata. The basic rocks are characterized by small to moderate mg numbers (30 to 54) and high SiO contents (51-57 wt. %). Low values of TiO (1.07-1.76 wt. %) span the low-Ti basalts. Ti/Y ratios in the dolerite dykes as well as the basaltic andesite and basalt of the 1 eruption phase are close to the recommended boundary 500 between high-Ti and low-Ti basalts. Ti/Y value from the 2 eruption phase basalt is higher and inclined to the high-Ti basalts. In spite of this fact, in all studied Hronicum basic rocks Fe * is lower than 12 wt. % and Nb/La ratios (0.3-0.6) are low, which is more characteristic of low-Ti basalts. The basic rocks are characterized by Nb/La ratios (0.56 to 0.33), and negative correlations between Nb/La and SiO , which point to crustal assimilation and fraction crystallization. The intercept for Sr evolution lines of the 1 intrusive phase basalt is closest to the expected extrusions age (about 290 Ma) with an initial Sr/ Sr ratio of about 0.7054. Small differences in calculated values I document a partial Sr isotopic heterogeneity source (0.70435-0.70566), or possible contamination of the original magma by crustal material. For Nd analyses of the three samples, the calculated values εCHUR (285 Ma) are positive (from 1.75 to 3.97) for all samples with only subtle variation. Chemical and isotopic data permit us to assume that the parental magma for the Hronicum basic rocks was generated from an enriched heterogeneous source in the subcontinental lithospheric mantle.