Fe-Ti-V Deposits of Eastern Siberia: Their Similarities and Differences

Abstract

Fe-Ti-V deposits related to the basic-ultrabasic intrusions are widespread within eastern Siberia, in its northern and southern parts. Two large massifs are located in the Kodar-Udokan trough Siberian Platform, and in the Taimyr Peninsula. They are the Chineysky intrusion and the Dyumtaleysky massifs consequently. The problem of ore origin includes an estimation of parental melt composition and its evolution. To solve it, we have studied the internal structure, composition of rocks and ores from these massifs. The Chineysky lopolith has a thickness of 2.5 km and consists of four rock groups formed during different stages. Layering is a typical feature of the second group of rocks enriched in titanomagnetite. Economic Cu-Ni sulfide mineralization (Cu/Ni=10-100) concentrates within the lower boundary of the massif and includes the endo-and exocontact ore. Chineysky massif consists of basic rocks with typical crustal characteristics (Ta-Nb negative and Pb positive anomalies). The Dyumtaleysky intrusion represents a tabular body of 600 m in thickness. It consists of two groups of rocks - gabbro (upper zone, 300 m) and peridotites (lower zone, 300 m). It was suggested that they were formed at two stages. The upper zone is characterized by thin layering which is similar to the layering of the Chineysky massif. Sulfides are concentrated within the massif (between upper and lower zones) and in its endocontact zone. The mineralization consists of chalcopyrite, pyrrhotite, pentlandite, millerite, cubanite; Cu/Ni= 1-0.5. In contrast to the rocks of the Chineysky massif, the rocks of the Dyumtaleysky intrusion are characterized by patterns without Ta-Nb anomaly. Gd/Yb ratio demonstrates the origin of these two massifs from different magma sources: shallow for the Chineysky intrusion and deep (with garnet) for the Dyumtaleysky one. Thus, Fe-Ti-V deposits could be formed from different magmas but contain the same type of ores because the leading process of ore formation is a multiple fractional crystallization.