Abstract
We present results of apatite fission-track analysis of seven intrusions located within the Permian-Triassic Siberian Traps Large Igneous Province (LIP): (1) alkaline-ultramafic central type plutons of Odikhincha, Yessey and Magan, (2) intrusions of Norilsk-1 and Kontay, (3) Padunsky sill, and (4) Kotuy dike. Additionally, we also present a set of new geochronological data for some of studied intrusions: (a) LA-ICPMS UPb apatite ages of the Odikhincha pluton (266 ± 29 Ma) and the Padunsky sill (241 ± 12); (b) RbSr ages from the Odikhincha (258.0 ± 0.6 Ma), Magan (242.8 ± 6.8 Ma) and Yessey (243.1 ± 2.7 Ma) plutons; and (c) 40Ar/39Ar mica ages from the Odikhincha (264.3 ± 3.0 Ma) and Magan (254.7 ± 3.1 Ma) plutons. Most of these intrusions, probably with the exception of the Odikhincha, were emplaced during the most voluminous phase of the Siberian Traps magmatism ca. 252–251 Ma, but their AFT ages are distributed from 207 ± 17 to 173 ± 13 Ma and much younger than Late Permian to Early Triassic isotopic ages from these and other Siberian Traps LIP intrusions. Available AFT, UPb, RbSr and 40Ar/39Ar data and time-temperature modeling has allowed us to create the first model of the post-Paleozoic tectono-thermal history of the Siberian Traps. After their emplacement ca. 251 Ma the studied rocks underwent a later phase of rapid cooling to below 120–60 °C during the time interval ~207–173 Ma and have remained near the surface until present. We propose this later cooling event is linked to exhumation associated with coeval Late Triassic-Early Jurassic large-scale uplift of the Siberian platform caused by collisional processes at its periphery. Our new results also indicate that at least a 1–2 km thickness of Siberian Traps lavas have been removed by erosion in the north of the Siberian platform since eruption, implying the total volume of the Permian-Triassic lavas was much greater than that currently preserved today.
Published Version
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