WIEK MOLIBDENITÓW W POLSCE W ŚWIETLE BADAŃ IZOTOPOWYCH Re-Os

Abstract

THE AGE OF MOLYBDENITES IN POLAND IN THE LIGHT OF Re-Os ISOTOPIC STUDIESAbstract. The paper presents the results of molybdenites that closely correlate with the Variscan granite intrusions in Poland. In the Karkonosze Massif and its eastern metamorphic cover, there are two separate stages of Re-Os ages of molybdenite crystallization (326 ±1 to 310 ±1 Ma), which reflect pneumatolitic and hydrothennal activity in the Carboniferous (from the "Visean/Serpukhovian to the Moscovian) In the Strzegom-Sobótka Massif, both rosette-like molybdenites disseminated in granitoids and those from the quartz veinlets reveal similar Re-Os ages that range from 309 ±1 to 296 ±2 Ma. Molybdenite crystallization in the Strzegom-Sobótka Massif was related to the post-magmatic processes associated with a slow cooling of magma responsible for the formation of homblende-biotite monzogranites. The time range of molybdenites crystallization form the contact zone between the Małopolska and Upper Silesian blocks is from 301 ±2 to 296.3 ±1.4 Ma. The oldest Re-Os isotopic age of molybdenite (350.5 ±1.2 Ma) was received for a molybdenite sample from the Polish part of the Tatra Mountains. The molybdenites from the eastern part of the Strzegom-Sobótka Massif (Siedlimowice quarry. 25? ±1 Ma) and from the Miedzianka abandoned Cu (-U) mine (213 ± 1 Ma) yielded the youngest Re-Os ages. These ages indicate tectonic reactivation and remobilization of hydrothennal fluids in the Late Permian and Late Triassic. The Re-Os isotopic studies of molybdenites allowed defining the time relation between successive hydrothennal stages of ore precipitation and tectonic-magma tic processes during ca. 140 million years e.g. from the Mississippian (Carboniferous) to the Norian (Late Triassic) in different areas of the occurrence of Variscan granitoid intrusions in Poland.