Diamond prospects in the southwestern flank of the Tungusk syneclise

Prospecting in the southeastern flank of the Tungusk syneclise and the geological structure, mineralogy, geochemistry, and conditions and history of the formation of the revealed aureoles of kimberlites-indicator minerals-are reviewed in this work. Middle Paleozoic diamond-bearing kimberlite bodies are shown to be the source of these aureoles. The aureoles represent redeposited units. At the initial stage of their development in the Middle Proterozoic, they formed under near-shore conditions, which defined the monomineral pyrope composition of the assemblage of kimberlite minerals, the limiting degree of grain rounding, and the profound hydraulic grading. At least two kimberlite fields are predicted based on morphotypes of pyropes (including their geochemical features)-the Tychany aureole in the north of the studied area and the Tarydak aureole in the south of it. The northern aureole is similar in pyrope geochemistry to the Daldyn aureole of the Yakutian diamond-bearing province; the southern, to the Malo-Botuobin region. Diamonds form a polychronous mixture: one part of them are background diamonds for the Siberian platform and are derived from Precambrian sources, whereas the other part is associated with the predicted Middle Paleozoic kimberlites. Reconnaissance and prospecting works are recommended west of the studied territory in the exposed areas. Methods of work are suggested that are based on the mineralogical control of aeromagnetic anomalies potentially related to karst. The latter is considered as a relict of old, productive, probably Upper Paleozoic deposits now eroded.