Position of the Aqtau-Dzungar microcontinent in the structural framework of the paleozoides of central Kazakhstan

The structure of the Riphean basement and the Early Paleozoic cover of the Aqtau-Dzungar massif and the surrounding Ordovician-Silurian island-arc, flysch, and accretionary complexes of western Central Kazakhstan and Northern Tian Shan are discussed. The rocks were obviously formed at the western (modern coordinates) active margin of a vast long-lived Dzungar-Balkhash paleoceanic basin. The similarity between the sequences of the Aqtau-Dzungar massif and coeval rocks at the back of the margin, as well as the occurrence of Late Ordovician granitoids within these zones along with their absence in the forearc structures, suggest, that the massif was located in the rear of the active margin of the paleocean until the latest Ordovician. Early in the Silurian, the margin was deformed by oblique wrench faults, along which the Aqtau-Dzungar massif was brought forward from the rear. Later, the Silurian volcanic front, flysch trough, and accretionary prism were offset eastward, and the massif was incorporated in the basement beneath the island-arc and flysch sequences.