The Platform is surrounded by major Phanerozoic suture zones formed during the assembly of the Pangaean supercontinent. The boundaries of the Siberian Platform are defined by the North-Siberian or Khatangian Depression in the north, Aldan-Vitim Massif and Baikal-Patom folded area in the south, Verkhoyansk foldbelt in the east and the Sayano-Taymyr fault zone, separating the Siberian Platform from the “young” West Siberian plate, on the west.
Kimberlite magmatism of the Siberian (Yakutian) province is believed to relate to deep-seated fractures along a major hinge zone between the Anabar Shield (between the Yenisei and Lena Rivers) and the relatively downwarped area during the crust movements associated with the folding of the Verkhoyansk belt. A remarkable characteristic of this region is that it contains more pipes with fresh, unaltered olivine than any other kimberlite region within the Siberian diamondiferous province. About 10% of the intrusions exhibit either two adjacent channelways or repeated intrusion of magma through the same chimney.
The Udachnaya pipe, the best known example of these twin diatremes, is located in the north-west part of the Daldyn field on the left bank of Pyropovy Creek. It consists of two adjacent bodies (East and West). At a depth of 250-270 m the two bodies separate.
Country rocks comprise Early Ordovician massive dolomites, limestones, argillites and sandstones and Late to Middle Cambrian dolomites, marls, argillites and limestones. The contact between country rocks and the kimberlite body is sub-vertical and well defined structurally. Both kimberlite and country rocks show significant alteration, and mechanical destruction and brecciation is common near contacts.
Both pipes are enriched in peridotitic nodules. Based on stratigraphic relationships, both intrusions are interpreted to be Devonian (~350 Ma), and most investigators believe that the Western pipe was formed earlier. A series of ages ranging from 389 to 335 Ma have been suggested for the Udachnaya pipes.
Groundmass textures, mineralogy and chemistry of the kimberlite rocks comprising both bodies of the Udachnaya pipe suggest two intruding phases. The Eastern and Western bodies of the Udachnaya kimberlite pipe differ from each other in terms of mineralogy, petrography, composition, and degree of alteration. The alteration of the Western pipe can be considered typical for kimberlite, while the rocks of the Eastern body are unique in having a lower degree of alteration, and in parts they are completely fresh.
Distribution of diamonds within the body of the Udachnaya pipe remains regular or changes very little with depth. Most diamonds have octahedral or rhombododecahedral habits. A large amount of diamond fragments is also present, usually with traces of corrosion on broken surfaces.
After Maya Kamenetsky, 2005
