For a long time, the thermal history of northeastern (NE) Fennoscandia in the Phanerozoic and Precambrian remained unknown, since no thermochronological studies were carried out within the Kola Peninsula area. Two years ago, we developed the first model of tectono-thermal evolution of the Kola Peninsula territory for the last 1.9 Gyr using a set of newly obtained apatite fission-track (AFT) and Ar/Ar thermochronological data. However, the low-temperature history of the most ancient tectonic unit of the northeastern part of the Kola Peninsula—the Archean Murmansk craton—remained poorly constrained due to the lack of AFT data. In this paper, we present the first results of AFT studies of 14 samples representing intrusive and metamorphic Precambrian rocks, located within the Murmansk craton of NE Fennoscandia. AFT ages and track length distributions indicate a similar tectono-thermal evolution of Precambrian tectonic units in NE Fennoscandia over the last 300 Myr. The AFT ages are distributed between ca. 177 and ca. 384 Ma; their median value, ~293 Ma, confirms the presence of a previously identified hidden thermal event that took place at about 300 Ma. However, a detailed analysis of the AFT age distribution shows the presence of three statistically distinguishable age components: 180–190 Ma (C1), 290–320 Ma (C2) and 422 Ma (C3). We assume that the relatively young AFT ages of C1 may originate from apatite crystals with low thermal resistivity. Remarkably, this value coincides with the initial stage of the Barents Sea magmatic province activity during large-scale plume-lithospheric interaction, as well as with the assumed age of an enigmatic remagnetization event throughout the Kola Peninsula. C2 ages can be observed in both the gabbroic and non-gabbroic samples, whereas C3 ages can only be found in gabbro. It is supposed that C2 ages, similarly to the Central Kola terrane, correspond to a cooling event related to the denudation of a thick sedimentary cover, representing a continuation of the Caledonian foreland basin towards NE Fennoscandia. C3 ages may be associated with a thermal event corresponding to the Caledonian collisional orogeny.

<p>The thermal history of the Siberian platform has not been studied and only single thermochronological study is available now [Rosen et al., 2009]. According to high-precision U-Pb dating the main phase of magmatic activity of the Siberian Traps Large Igneous Province took place ~252.0-251.3 Ma [Kamo et al., 2003] and its duration didn’t exceed ~1 Myr. But according to Ar/Ar dating (~240 Ma) [Ivanov et al., 2013] the total duration of the Siberian Traps formation may be estimated as long as ~10 Myr. In addition, single apatite fission track (AFT) ages are approximately 222-185 Ma [Rosen et al., 2009].</p><p>We present the first results of AFT dating from the Guli pluton and computer modeling of its post-magmatic cooling, as well as some new AFT ages from other magmatic bodies within the Siberian platform. Based on these data we present the first model of the tectonothermal evolution of the Siberian platform in Mesozoic and Cenozoic.</p><p>The Guli massif is located within the Maymecha-Kotuy region of the Siberian Permian-Triassic Traps and is the world's largest alkaline-ultrabasic complex. Results of U-Pb dating of baddeleyite from the carbonatites – the latest intrusion phase – 250.2±0.3 Ma [Kamo et al., 2003] correspond to the time of massif’s crystallization.</p><p>AFT dating was conducted by an external detector method at the University of Arizona (Tucson). The fission track ages of the Guli are in the range of ~250-231 Ma with the mean standard error (1σ) ±34 Myr. In addition, we obtain five new AFT ages as well as U-Pb age obtained from different intrusive bodies within the Siberian platform: Kontayskaya intrusion, Odikhincha massif and Padunsky sill. All obtained AFT ages are in the range of 195-173 ±13 (1σ) Ma, which corresponds to the Early-Middle Jurassic. At the same time, the U-Pb LA-ICPMS age of apatite from Padunsky sill is 242±7 Ma.</p><p>Thermal history modeling using fission track age data and track lengths distribution was performed in HeFTy v.1.8.3. Based on the obtained results we consider the following model of tectonic-thermal evolution of the studied intrusive massifs: (1) the emplacement of intrusions ca. 250 Ma; (2) their burial under a thick sedimentary (volcanic?) cover; (3) regional exhumation and cooling below 110°C about 220-190 Ma.</p><p>The research was carried out with the support of RFBR (grants 18-35-20058 and 18-05-00590) and Programs of development of Lomonosov Moscow State University.</p>

<p>We present results of apatite fission-track (AFT) and other geochronological data (apatite U-Pb (LA-MC-ICPMS) and Rb-Sr dating) from several intrusions located within the Siberian Traps Large Igneous Province: (1) alkaline-ultramafic ring plutons of Odikhincha, Yessey and Magan, (2) intrusions of Norilsk-1 and Kontay, (3) Padunsky sill and (4) Kotuy dike. The studied intrusions were emplaced close to the age of the voluminous phase of the Siberian Traps LIP based on the new apatite U-Pb and Rb-Sr ages, as well as other results obtained earlier by other researchers. The obtained AFT ages are distributed between ca. 207 and ca. 173 Ma, and are much younger than the available latest Permian to earliest Triassic U-Pb and Ar/Ar data on the Siberian Traps. We interpret the AFT ages as a consequence of sedimentary burial of the studied magmatic complexes to below the closure temperature of the AFT system, which took place after the formation of intrusions ca. 252-250 Ma. Later cooling as a result of exhumation of the studied rocks to near surface temperatures and decreasing of thermal flow then took place in the Late Triassic-Early Jurassic.</p>