Thermal evolution of the continental crust beneath the northeastern Siberian craton was studied based on the interpretation of apatite fission-track ages. The samples selected for AFT dating were collected from depths between 2 and 3 km along a 1000-km-long profile, from the crystalline basement of the Siberian platform. The AFT ages range from 185 to 222 Ma, indicating that in the late Triassic-early Cretaceous, the top of the crystalline basement was cooled below ∼100°C. Once the apatite cooled below this temperature, it began to accumulate and preserve tracks produced by spontaneous fissioning of 238U, and the number of tracks preserved is effective in determining the ages of events using the apatite fission-track method (AFT).

New trace element data were obtained by ICP-MS for 58 samples representing eight intrusive phases of the Raumid granite Pluton. All of the rocks, except for one sample that was deliberately taken from a greisenized zone, were not affected by postmagmatic fluid alteration. The sequential accumulation of incompatible trace elements (Rb, Ta, Nb, Pb, U, and others) in the Raumid Pluton from the early to late phases coupled with a decrease in incompatible element contents (Sr, Eu, Ba, and others) indicates a genetic link between the granites of all phases via fractional crystallization of a granite melt. The REE distribution patterns of final granite phases are typical of rare-metal granites. The Ta content in the granites of phase 8 is only slightly lower than that of typical rare-metal granites. Greisenization disturbed the systematic variations in trace element distribution formed during the magmatic stage. The ranges of trace element contents (Rb, Sr, Ta, Nb, and others) and ratios (Rb/Sr, La/Lu, Eu/Eu*, and others) in the Raumid granite overlap almost entirely the ranges of granitic rocks of various compositions, from the least differentiated with ordinary trace element contents to rare-metal granites. This indicates that the geochemical signature of rare-metal granites can develop at the magmatic stage owing to fractional crystallization of melts, which is the case for the melt of the Raumid granite.

The Kalguty ore-magmatic system comprises two intrusive complexes: the Kalguty granite-leucogranite complex and Eastern Kalguty complex of dikes and small intrusions. U-Pb dating of individual zircon grains from granites of the main intrusive phase demonstrated that the crystallization age of small grains of magmatic habits and outer rims of large grains is almost concordant and is 216 ± 3 Ma. Ar-Ar isotope study shows that the K-Ar system of biotites from granites of the main phase within the Kalguty ore field was disturbed (radiogenic Ar was partially lost) and gave an age of 202 ± 1 Ma. The Ar-Ar dating of muscovites from intraore and postore dikes of the Eastern Kalguty complex devoid of signatures of postmagmatic recrystallization and superimposed greisenization gave similar ages of 205–201 Ma. This date is considered as the emplacement age of the Eastern Kalguty dikes and associated complex W-Mo-Bi-Be ore mineralization. Sm-Nd and Pb-Pb isotopic study of granites, ongonites, and elvans of the Kalguty ore-magmatic system and host rocks shows that these systems were closed. For example, recalculation of Nd isotopic ratios for corresponding ages of crystallization of magmatic systems (216 and 205 Ma) shows that ɛNd(T) values decrease from −1.9 to −3.5 ... −5.08 with transition from granite-leucogranite to subvolcanic granite porphyry, ongonite, and elvan dikes with corresponding increase of model ages of protoliths from 1.0 to 1.25 Ga. Lead isotopic ratios for leaching residues of whole-rock samples of all rock varieties (206Pb/204Pb = 18.305–18.831; 207Pb/204Pb = 15.527–15.571) are plotted well below the line of average crustal lead evolution according to the Stacey-Kramers model.

Geochronological database considered in the work and characterizing the Anabar collision system in the Northeast Siberian craton includes coordinated results of Sm-Nd and Rb-Sr dating of samples from crustal xenoliths in kimberlites, deep drill holes, and bedrock outcrops. As is inferred, collision developed in three stages dated at 2200–2100, 1940–1760, and 1710–1630 Ma. The age of 2000–1960 Ma is established for substratum of mafic rocks, which probably originated during the lower crust interaction with asthenosphere due to the local collapse of the collision prism. Comparison of Sm-Nd and Rb-Sr isochron dates shows that the system cooling from ≈700 to ≈300°C lasted approximately 300 m.y. with a substantial lag relative to collision metamorphism and granite formation. It is assumed that accretion of the Siberian craton resulted in formation of a giant collision mountainous structure of the Himalayan type that was eroded by 1.65 Ga ago, when accumulation of gently dipping Meso-to Neoproterozoic (Riphean) platform cover commenced.

Detailed paleomagnetic studies of the Ui Group of sedimentary rocks and Late Riphean basic sills from the Yudoma-Maya zone of the Uchur-Maya area have been performed. The Sm-Nd and K-Ar radiomet- ric ages of the sills were determined. A high-confidence paleomagnetic pole was obtained for the Siberian Cra- ton, corresponding to an age of 942 ± 19 Ma. Along with the poles previously obtained for the Kerpyl' and Lakhanda groups of the Uchur-Maya area, the new pole makes up a segment of the apparent pole wander path describing the paleogeographic position and drift of the Siberian Craton during the time interval between 1070-1030 and 1000-950 Ma ago. A comparison of the new segment and the respective paths for Laurentia and East Gond- wana suggests that these cratons might have been parts of one supercontinent only if the generally accepted option of the polarity of Precambrian paleomagnetic directions is revised for Laurentia (and East Gondwana) or Siberia. The use of the polarities of the paleomagnetic directions proposed in (31, 37, 39) suggests that the paleomagnetic poles of the reviewed cratons fall into the same region of the globe after the matching of East Gondwana with Laurentia as in the classical configuration of Rodinia and after connecting the SSW portion of Siberia with the northern part of Laurentia. In such a configuration, the respective segments of the apparent polar wander paths for Siberia and Laurentia virtually repeat one another, this supporting the view that these cratons belonged to the same supercontinent during the Middle and Late Proterozoic.