Monazite U-Th-total Pb age constraints on an early Permian volcanic event in the South Carpathians, Romania.

The sequence of Permian volcanic and volcaniclastic rocks (up to 2 km thick) in the Sirinia Basin (Svinița-Svinecea Mare sedimentary zone) of the Upper Danubian Units, South Carpathians, is considered to be the product of subaqueous volcanism passing into a subaerial volcanism and subsequent deposition by debris flow. The investigated volcano-sedimentary rocks are composed of a rhyolitic clastic framework embedded within a fine-grained matrix. The electron probe microanalyses of monazites in the rhyolite clasts and in the volcaniclastic matrix yielded a U-Th- total Pb mean age of 296±3.2 Ma. This result is the first to constrain the age of the volcanic activity event recorded in the volcaniclastic rocks of the Sirinia Basin. The monazite age also estimates the maximum depositional age of the volcano-sedimentary rocks as not older than early Permian (middle Asselian). [ABSTRACT FROM AUTHOR]