Geological evolution of the south Tarim craton : constraints from magmatic and sedimentary rocks and implications for positions of the Tarim craton in supercontinents

Abstract

The Tarim Craton is one of the three cratons in China (the other two being the North China Craton and the Yangtze Craton). It is bounded by the Tianshan to the north, the Western Kunlun to the southwest, and the Eastern Kunlun, the Altyn Tagh and the Qilian to the southeast. Position of the Tarim Craton in supercontinents has been hindered by poor exposure due to the widespread Cenozoic Taklamakan desert, with exposure of Precambrian basement rocks and Paleozoic to Quaternary rocks limited to isolated outcrops around its margins. South Tarim, composed mainly of the Western and Eastern Kunlun orogenic belts, the focus of this Ph.D. thesis, experienced a complicated evolutionary history with respect to Rodinia and Gondwana evolution. The breakup of Rodinia and Gondwana resulted in the opening of the Proto-Tethys Ocean during Neoproterozoic time and of the Paleo-Tethys Ocean during Silurian-Devonian times, respectively. Thus, this thesis first places emphases on the evolution of the Proto-Tethys and Paleo-Tethys oceans followed by locating positions of the Tarim Craton in supercontinents. In Western Kunlun, the Proto-Tethys lithosphere underwent doubled-sided subduction during early Paleozoic time. The southward subduction initiation occurred around or prior to 531 Ma and the northward subduction occurred at around or prior to 470 Ma. The final closure of the Proto-Tethys Ocean occurred at 431-420 Ma. In Eastern Kunlun, the southmost branch of the Proto-Tethys Oceanic lithosphere subducted northward and closed at 444-424 Ma. In Eastern Kunlun, the ca. 390-380 Ma continental rifting leading to the final opening of the Paleo-Tethys Ocean is attributed to the post-collisional gravitational instability associated with the closure of the Proto-Tethys Ocean and the far-field extensional stress induced by retreating subduction of the Paleo-Asian Ocean along the northern margin of Tarim-Qaidam. The initial northward subduction of the Paleo-Tethys oceanic lithosphere occurred at ca. 366-335 Ma and the closure occurred at 235-225 Ma followed by 225-200 Ma post-collisional extension. North Tarim collided with southern Siberia at 1.8-2.0 Ga within Columbia and drifted away at 0.9-1.5 Ga. South Tarim possibly collided with northern India during the assembly of Rodinia and drifted away at 800 Ma. Well comparable zircon age spectra and Hf isotopic compositions suggest a close linkage of South Tarim and North India in Gondwana. Moreover, South Tairm and North India lay at the periphery of both Rodinia and Gondwana.