First LA-ICP-MS Apatite Fission-Track Ages from the Basement of the Siberian Platform (Nepa-Botuoba Anteclise)

摘要

The first results of laser ablation inductively-coupled plasma mass-spectrometry apatite fission-track dating are presented from drill core of boreholes, which exposed the top of the Siberian Platform's crystalline basement in the Nepa-Botuoba Anteclise. Apatite fission-track ages, obtained for nine samples from a depth of ~2 km, form three groups with mean values of 200, 140, and 60 Ma. A thermal event with an age of ~200 Ma is widely abundant almost within the entire Siberian Platform and reflects the stage of its intense Early Jurassic uplifting. Resetting of the apatite fission-track system -140 Ma corresponds to tectono-ther-mal events, which mark the final stage of collision of the Mongol-Okhotsk fold belt. The youngest apatite fission-track ages age of ~60 Ma, on the one hand, may reflect the beginning of the Baikal rifting and, on the other hand, may be a result of the high U content of apatite.