Late Vendian age of the Khan-Taishiri ophiolite complex in western Mongolia

The age of ophiolite plagiogranites from the Khan-Taishiri ophiolite comple x, western Mongolia, was determined by the U-Pb zircon method as 568.1 +/- 4.0 Ma This complex is a rare fragment of the ancient Central Asian blocks where real geological relationships within large tectonic slabs making up t he ridge have been established between all ophiolite sequences but ultrabas ic rocks: pyroxenite and gabbro from banded sequence, basic rocks of dike c omplex, dolerite sills, basic pillow lava, and deep-water clay-siliceous se diments. The Neoproterozoic age of the Khan-Taishiri ophiolite complex suggests the presence of a Vendian island-arc system within the Central Asian Mobile Bel t. The model for this system was described for the first time by L.P. Zonen shain and O. Tomurtogoo on geologic objects of western Mongolia from the Dz avhan River to the northern slopes of the Mongolian Altai Ridge (Dzavhan, G obi-ALtai, Khan-Taishiri, Naran, Ulan-Shandian, and Kuroi subzones). This s ystem obviously included the Daribi ophiolites of western Mongolia; the Aga rdag and Shishkhid ophiolites of Tuva; the Dzhida and Ol'khon fragments of island-arc system; the belt of subductional layered massifs of Northern Bai kal and eastern frame of the Muya Block; the Naran, Eastern Sangilen, South ern Khamar-Daban, OL'lhon, and Bodaibo fragments of sedimentary basin; the Dzavhan, Hovsgol-Bokson, Western Baikal, and Baikal-Patom shelf fragments. Ocean lithosphere was represented by Bayan-Khongor ophiolotes.