FIRST LA-ICP-MS APATITE FISSION-TRACK AGES FROM THE SIBERIAN PLATFORM BASEMENT (NEPSKO-BOTUOBINSKAYA ANTECLISE)

Abstract

We present the first results of LA-ICP-MS apatite fission-track dating (AFT) from nine core samples from wells, that exposed the top of the crystalline basement of the Siberian platform within the Nepsko-Botuobinskaya anteclise on the ~2 km depth. Obtained AFT ages belong to three clusters with mean values of 200, 140, and 60 Ma. A thermal event of ~200 Ma is widespread throughout almost the entire Siberian platform and reflects the stage of its Early Jurassic uplift. Reset of the fission-track geochronometer in apatite ~140 Ma correlates with tectono-thermal event marking the final stage of the Mongol-Okhotsk fold belt collision. The youngest AFT ages of ~60 Ma, on the one hand, may reflect the early (crypto) stage of the Baikal rifting, and, on the other hand, be a consequence of the high content of uranium in apatite.