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The terranes composing the basement of the Tian Shan were originally sutured together during two collisions in Late Devonian-Early Carboniferous and Late Carboniferous-Early Permian time. Since then, the range has repeatedly been uplifted and structurally reactivated, apparently as a result of the collision of island arcs and continental blocks with the southern margin of Asia far to the south of the range. Evidence for these deformational episodes is recorded in the sedimentary histories of the Junggar and Tarim foreland basins to the north and south of the range and by the cooling and exhumation histories of rocks in the interior of the range. Reconnaissance apatite fission-track cooling ages from the Chinese part of the range cluster in three general time periods, latest Paleozoic, late Mesozoic, and late Cenozoic. Latest Paleozoic cooling is recorded at Aksu (east of Kalpin) on the southern flank of the range, at two areas in the central Tian Shan block along the Dushanzi-Kuqa Highway, and by detrital apatites at Kuqa that retain fission-track ages of their sediment source areas. Available 40 Ar/ 39 Ar cooling ages from the range also cluster within this time interval, with very few younger ages. These cooling ages may record exhumation and deformation caused by the second basement suturing collision between the Tarim-central Tian Shan composite block and the north Tian Shan. Apatite data from three areas record late Mesozoic cooling, at Kuqa on the southern flank of the range and at two areas in the central Tian Shan block. Sedimentary sections in the Junggar and Tarim foreland basins contain major unconformities, thick intervals of alluvial conglomerate, and increased subsidence rates between about 140 and 100 Ma. These data may reflect deformation and uplift induced by collision of the Lhasa block with the southern margin of Asia in latest Jurassic-Early Cretaceous time. Large Jurassic intermontane basins are preserved within the interior of the Tian Shan and in conjunction with the fission-track data suggest that the late Mesozoic Tian Shan was subdivided into a complex of generally east-west-trending, structurally controlled subranges and basins.Apatite data from five areas record major late Cenozoic cooling, at sites in the basin-vergent thrust belts on the northern and southern margins of the range, and along the north Tian Shan fault system in the interior of the range. The thrust belts

The Du-Ku Highway traverses the Tian Shan from the cities of Dushanzi to Kuqa in western China and provides a section across the full width of this Paleozoic orogen.The north Tian Shan consists of an accretionary complex of deformed ophiolite, arc volcanic assemblages, and siliciclastic sedimentary rocks derived mainly from volcanic arcs. The central Tian Shan is underlain by Precambrian basement covered mainly by Carboniferous andesitic tuff, Paleozoic marine carbonate and siliciclastic strata, and abundant Carboniferous-Early Permian granitoids. The south Tian Shan features continuous sequences of Silurian to Lower Carboniferous carbonate, chert, and siliciclastic strata of the deformed Paleozoic passive continental margin of the Tarim block.A high pressure-temperature (P-T) blueschist belt, parallel to and south of the Nikolaev line, which bounds the central and south Tian Shan, is exposed to the west of the Du-Ku Highway. Previously published radiometric ages bracket the blueschist metamorphism of the blueschist belt as 415-315 Ma. A paired coeval magmatic belt to the north was active from at least 400 Ma to ca. 330 Ma. Radiolarian fossils from chert associated with the north Tian Shan ophiolite, and Lower to Middle Carboniferous lithic turbidites structurally imbricated with ophiolite and tuff in the north Tian Shan, indicate that subduction-accretion along the north Tian Shan lasted at least through the end of the Early Carboniferous. Plutonism in the Borohoro arc along the northern margin of the central Tian Shan block culminated during Late Carboniferous-Early Permian time based on radiometric dating.We infer that amalgamation of the Tian Shan proceeded in two steps: (1) accretion of the central Tian Shan block to the northwest margin of the Tarim block by the Middle Carboniferous, with attendant cessation of arc magmatism and high P-T subduction metamorphism; (2) accretion of the Junggar arc complex and the