New 40Ar-39Ar age constrains for magmatic and hydrothermal activity in the Holy Cross Mts. (southern Poland)

Abstract

New 40Ar-39Ar isotope ages of diabase intrusions from the Holy Cross Mountains (Poland) confirm the presence of at least two events of Paleozoic magmatic activity in the study area. The oldest, latest Silurian/earliest Devonian (ca. 424–416 Ma) episode is recorded by a diabase from the Bardo Syncline (Zarobiny PIG-1 borehole) in the Kielce Region. A younger, Serpukhovian (ca. 331–323 Ma) event is documented by a diabase from the Milejowice-1 borehole drilled in the Łysogóry Region. The diabase intrusion penetrated by the Wzorki-1 borehole, also located in the Łysogóry Region, is most probably of the same age. It provided, however, consistent mid-Triassic (243 Ma) 40Ar-39Ar isotopic age reflecting its pervasive hydrothermal alteration. The first stage of the post-Caledonian hydrothermal activity in the Holy Cross Mts. which produced polymetallic copper and iron-bearing mineralisation may be linked with the younger magmatic phase defined here. The second stage of post-Caledonian hydrothermal activity in the Holy Cross Mts., associated with the lead-zinc mineralisation, may be correlated with the Middle Triassic hydrothermal event recorded in the Wzorki diabase. Suggestions of temporal relationships between magmatic/hydrothermal activities and mineralisation events should, however, be constrained by further detailed geochemical and mineralogical studies.