40Ar/39Ar-age of the Talakhtakh diatreme rocks (Arctic Siberia)

In the Eastern margin of the  Anabar shield the Proterozoic alkaline pipes, dikes, and stocks are widespread. The largest Talakhtakh diatreme cut Middle-Upper Riphean dolomites (MP3-NP2) at the left bank of Kuonamka River (Fig. 1). The Talakhtakh diatreme includes alkaline basaltoids, ultra-K-trachytes, lamproites, olivine leucitites, tephrites, (Vishnevsky et al., 1986). TRE distribution indicates the proximity of sanidine trachytes to lamproites.

 The ⁴⁰Ar/³⁹Ar laser dating show two age maxima 1476 ± 17 (N = 14) and 1321 ± 17 (N = 9) Ma. If 10 points form a linear regression, with an age value of 1497 ± 40 million years, an initial ratio of 189 ± 100, then most of the remaining points are located along the abscissa axis. This arrangement may be associated with different degrees of rejuvenation of the K/Ar isotope system within the dating sites. The weighted average of 1476 ± 17, as more accurate, corresponds to the age of sample formation.

Ernst et al (2016) identified a new Kuonamka Large Igneous Province (LIP), based on U-Pb dating of baddeleyites from dolerite dikes and sills of the Anabar shield. The age of Kuonamka LIP is ~ 1501 ± 3 Ma. The resulting 40Ar/39Ar is the age of leucite trachytes (lamproites) The Talakhtakh diatreme fully corresponds to the time of occurrence of the Kuonamka LIP and indicates the formation of high-K effusions of the Talakhtakh complex during this period.

This work supported by RFBR grants: No. 18-05-70109 and the Russian Ministry of Education and Science

Gusev N.I., et al. State Geological Map of the Russian Federation. Sheet R-49-Olenek. An explanatory Memorandum. Saint Petersburg: Map factory VSEGEI. . 2016. 448 с.

Vishnevskiy S.A., Dolgov Yu. A., Sobolev N. V.  Geology&Geophysics, 1986. № 8. P. 17-27.

Ernst R. E., Okrugin A.V. et al.  Russian Geology&Geophysics. 2016. № 5. P. 653,-671.