The Tommot pluton: a Middle Paleozoic rift-related alkaline gabbro and syenite complex, Yakutia, northeast Russia
1Yakutian Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, 39 Lenin Prospect, 677891, Yakutsk, Russia
2Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
3Yakutian State Geological Expedition, 13 Kirov Street, 677891, Yakutsk, Russia
*formaly at: Yakutian Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, 39 Lenin Prospect, 677891, Yakutsk, Russia
Abstract. The Tommot pluton is located within the continental Omulevka terrane of the inner zone of the Verkhoyansk-Kolyma Mesozoic orogen. It is a small complex (~12 km2) composed of alkaline-ultramafic rocks, alkaline and subalkaline gabbroids, and alkaline and quartz syenites. The pluton is unique both in the composition and age of its constituent rocks. Mineralogical-petrographical and geochemical studies of the rocks indicate that the alkaline rocks resulted from the melting of depleted mantle horizons. K-Ar, Rb-Sr, and 40Ar/39Ar age determinations confirm a Paleozoic age of the rocks. Formation of the alkaline rocks is related to Middle Paleozoic rifting which occurred as two discrete events: a Late Devonian event, which affected the marginal part of the Siberian continent, and a Late Carboniferous event that reflects internal deformation of the Omulevka terrane or late-stage extension. A spatially associated alkali granite, the Somnitel'nyy pluton, is Late Jurassic–Early Cretaceous in age and is synchronous with accretion of the Kolyma-Omolon Superterrane to Siberia in the Mesozoic.
Trunilina, V. A., Layer, P. W., Parfenov, L. M., Zaitsev, A. I., and Orlov, Y. S.: The Tommot pluton: a Middle Paleozoic rift-related alkaline gabbro and syenite complex, Yakutia, northeast Russia, Stephan Mueller Spec. Publ. Ser., 4, 97-109, doi:10.5194/smsps-4-97-2009, 2009.