New Age Datings of Gabbroides of the Kershor Complex (Polar Urals)

摘要

The Kershor dunite-wehrlite-clinopyroxenite gabbroic complex stretches continuously along the eastern border of the Voykar-Synya hyperbasite massif in the southern segment of the Polar Urals (Fig. 1). At present it is considered as a part of the Paleozoic unified ophiolite association, which also includes hyper- basites of the Rai-Iz and Voykar complexes and diabase dikes of the Lagorta complex. However, the Sm- Nd isotopic age datings obtained recently are disputed. On the one hand, the age of harzburgites, web-sterites, dunites, gabbro, and diabases is 387 ± 34 Ma . On the other hand, the U-Pb age of zircons from chromitites of the Voykar complex is 585 ± 6 Ma. The age datings based on the Re-Os method for dunites, pyroxenites, chromitites, and banded peridotites of the same complex are 600 and 536 ± 17 Ma. In the opinion of the authors, who dated rocks of the Rai-Iz and Voykar hyperbasite complexes, these age datings recorded the time of "melt percolation through harzburgites" in the oversubduction environment . The calculations of trace-element composition of the "percolating melts" lead to the conclusion that the model melts are similar to gabbroides of the Kershor complex in trace-element composition. In this regard, the age and origin of rocks of the Kershor complex is the fundamental problem of the geology of the Polar Urals.