Revisiting to the Neoproterozoic tectonic evolution of the Tarim Block, NW China

Abstract

Abstract The Tarim Block comprises two terranes, namely, the Northern Tarim terrane (NTT) and the Southern Tarim terrane (STT). The distinct geological features of the Pre- Cryogenian basement and igneous activity between these two terranes that share common Cryogenian cover sequences strongly suggest that they underwent independent pre-Cryogenian evolutions. However, owing to the likely position of the Tarim Block on the margin of Rodinia, the Neoproterozoic igneous rocks and sedimentary sequences of this block should provide important insights into the geodynamics of the evolution of this supercontinent. In this contribution, our new geochronological data show that the earliest glacial deposit in the Tarim Block, namely, the Beiyixi tillite, was deposited a little later than 720 Ma, which is consistent with the timing of the global Sturtian glaciation. The other two glacial deposits, namely, the Altungol–Tereenken and Hankachocugh tillites, were deposited at 685–635 Ma and later than 591 Ma, consistent with the global Marinoan and Gaskiers glaciations, respectively. Combining our field observations and new geochronological data with a comprehensive synthesis of the Precambrian basement rock units, metamorphic events, and igneous activities in both the NTT and STT, we construct a detailed late Mesoproterozoic to Cryogenian evolution for the Tarim Block, and discuss its relationship to Precambrian supercontinent evolution. We suggest that the STT might be a continental fragment that separated and drifted from the Congo Craton during the initial breakup of Rodinia and subsequently docked along the northern fringe of Australia a little later than ca. 800 Ma. In contrast, the NTT might be a continental fragment that detached and drifted from North China–India during the breakup of the Columbia supercontinent. During the process of breakup of Columbia and the assembly of Rodinia, the NTT amalgamated with the STT a little earlier than 800 Ma, owing to circum-Rodinia subduction between 1000 and 760 Ma. However, upwelling of the Rodinia plume could have affected subduction along the northern margin of the Tarim Block, as demonstrated by a voluminous ca. 770 Ma mafic dyke swarm. The Rodinia plume terminated the subduction along the northern margin of the Tarim Block at ca. 740 Ma, suggesting that the plume could have played a key role in the breakup of Rodinia. This conclusion is supported by Cryogenian–Cambrian sedimentary sequences with passive-continental-margin affinity in the Tarim Block, indicating the detachment and movement of this block from Rodinia. Both the characteristics of Cryogenian–Cambrian basins and coeval igneous activity argue strongly against long-term subduction along the northern margin of the Tarim Block.