Eclogites in the Chara zone, NE Kazakhstan: New geochemical and geochronological data

The Chara shear zone trends from northwest to southeast for hundreds of kilometers across eastern Kazakhstan and is the main structure separating the Siberian and Kazakhstan continents (Dobretsov, 1974; Ermolov et al., 1981; Buslov et al., 2003). The Chara ophiolite belt in the axial part of the zone is megame-lange of ophiolite fragments and blocks of volcanic, HP/LT (high-pressure/low-temperature) metamorphic, and sedimentary rocks in a serpentinite matrix. The oceanic-floor, guyot, and arc-slope sedimentary rocks are dated mostly at the Late DevonianEarly Carboniferous (Ermolov et al., 1981; Sennikov et al., 2003), although abyssal silicic rocks were found out to contain Ordovician Radiolaria (Iwata et al., 1994). Detailed petrological and geochemical studies (Simonov et al., 2010; Safonova et al., 2004, 2012) of volcanic rocks in the Chara zone have proved that these rocks were formed in various geodynamic environments: mid-oceanic ridges, oceanic plateaus, intraplate oceanic islands, and island arcs. Data on the sequence of geologic events that produced the megamelange of the Chara zone significantly help in understanding the geodynamic evolutiona of eastern Kazakhstan, southern Siberia, and northwestern China.