Magmatic episodes in the Holy Cross Mountains, Poland – a new contribution from multi-age zircon populations

Abstract

This contribution reports on new U–Pb zircon age data from magmatic rocks from the Holy Cross Mountains (HCM) of Poland. The analyzed samples were taken from lamprophyre and diabase veins of Podkranów and Janowice-2 as well as from tuff horizon of Kielce Beds (Ludlow). Internal morphologies have been investigated by SEM-BSE and cathodoluminescence images and they have been used as a guide for the selection of genetically various type of grains, e.g. potential auto-, ante- and xenocrysts, that were analyzed by ion microprobe. The U–Pb age of the magmatic events at 414.2 ±6.6 Ma (Kielce tuff), 322 ±12 Ma (Podkranów, lamprophyre), and 300±10 Ma (Janowice-2, diabase) confirmed the time frame of known magmatic activity reported within the HCM, as determined by 40Ar/39Ar geochronology in previous studies. The zircon investigation revealed also multiple populations with record of an earlier pulse of magma system (antecrysts), as well as abundant xenocrysts.