© N.V. Tsukanov1, S.G. Skolotnev2

1 P.P. Shirshov Institute of Oceanology RAS. Moscow, 117997
2 Geological institute RAS, Moscow, 109017.

The chemical composition of minerals and ultramaphic and maphic rocks from peridotite massiff of Poputnaya Mountin and from blocks in serpentinite melanges in northern part of Valagin Ridge was studied. It was assigned to two ophiolites complexes. One of them is a fragment of ancient oceanic crust, which was a basement for Achayvayam-Valagin paleoarc. It is represented by tholeiite basalts, pelagic sedimentary deposits and gabbroids from melange. The tholeiite basalts and gabbroids are similar to N-tipe MORB by petrogrochemical composition. Pelagic sediments are represented by red and braun chert which have santonian-campanian age by microfauna radiolariya. The second ophiolite complex is represented by highly depleted supra-subduction peridotites massiff of Poputnaya Mountin. According to the composition of mine minerals these peridotites are joined in four groups. Rocks from different groups are irregulary interbedded into massiff of Poputnaya Mountin. These groups are separated by composition of spinels and ortopiroxen. Some of them lie in the field of abisal oceanic peridotites. The others - in the field of supra-subduction garzburgites and dunites, some rocks have intermediate compositions.