REDOX STATE OF PERIDOTITE XENOLITHS FROM SOUTH AND MIDDLE TYAN-SHAN -EXPERIMENTAL-DETERMINATION

Intrinsie oxygen fugacity measurements have been conducted for individ ual minerals (olivines, pyroxenes, spinels) of mantle inclusions in Ea rly-Mesozoic alkaline basaltoids of South and Middle Tyan Shan. Predom inant type of mantle xenoliths in the first region is ''green'' chrome -spinel pyroxenite, whereas in the second one - spinel lherzolite and ''black'' titanium-bearing pyroxenite. Wide variety of f(O2). values a n the interval WM to IW buffers and more reduced state as compared to the same rocks of Baikalian and Mongolian rift zones are the specific features of redox state of these mantle rocks. The first feature agree s with the signs of deep chemical differentiation of the peridotites e xpressed in chemical and mineral composition as well as metasomatic al teration. The second one gives evidence of the mantle material involve d in depths in the process of folded Tyan Shan area formation has f(O2 ) values close to that expected for the primary mantle matter.