JUNGGAR, TURFAN AND ALAKOL BASINS AS LATE PERMIAN TO EARLY TRIASSIC EXTENSIONAL STRUCTURES IN A SINISTRAL SHEAR ZONE IN THE ALTAID OROGENICCOLLAGE, CENTRAL-ASIA

The Junggar, Turfan and Alakol basins in northwestern China and Kazakh stan formed as Late Permian to ?Early Triassic extensional structures in a broad sinistral shear zone between large strike-slip faults that separate two main domains of the Altaid orogenic collage. This extensi on was in response to an inferred large (>1000 km) sinistral motion of the East European craton with respect to the Angaran craton during th is time. Deformation associated with the formation of the basins was t aken up in part by counter-clockwise rotations of crustal blocks with respect to the Altaid orogenic collage and to the Angaran craton. This event is the only important phase of extension in a region otherwise dominated by compressional tectonics throughout the Phanerozoic. The b asement rocks of these basins formed by Altaid subduction-accretion th rough the latter half of the Palaeozoic and the region was subsequentl y thrown into compression again during the Mesozoic Cimmeride and Ceno zoic Alpide evolution.