Revisiting the Precambrian evolution of the Southwestern Tarim terrane: Implications for its role in Precambrian supercontinents

The Tarim block in NW China consists of a Precambrian basement and late Neoproterozoic to Paleozoic cover sequences. In order to better understand its roles in Precambrian supercontinent evolution, we used SHRIMP and LA-ICPMS U-Pb methods to date late Paleoproterozoic rifting-related mafic dykes and Mesoproterozoic igneous activity in the Precambrian of the southwestern Tarim terrane (STT): 1) WNW trending mafic dyke swarm emplaced at ca. 1785 Ma; 2) Mesoproterozoic bimodal volcanic sequence (the lower member) and marble- clastic-quartzite sequences (the upper member) deposited at ca. 1525 Ma and 1500–1400 Ma, respectively; 3) late Mesoproterozoic granodiorite-augen granite-leucogranite complex emplaced at ca. 1117 Ma. Geochemistry revealed that the 1784 ± 12 Ma mafic dykes were derived from an E-MORB – like mantle source suggesting an extensional setting, and likely linked with coeval major large igneous provinces (LIPs) on several crustal blocks which collectively suggest a pulse of rifting associated with assembly of the Columbia supercontinent. The obtained U-Pb age of 1525 ± 4 Ma from a meta-rhyolite in the bimodal sequence matches a recently discovered 1525–1529 Ma Large Igneous Province from the southern West African craton (Essakane-Sambarabougou swarm) and formerly adjacent Amazonian craton (Kayser event). Geochemistry of the ca. 1117 Ma granitic intrusions defines their A-type signature. These may be linked to coeval intraplate mafic magmatism of a reconstructed 1110 Ma LIP involving Kalahari, Congo, India (Bundelkhand block), Amazonia cratons. In line with these three newly recognized pulses of Precambrian igneous activities in STT and the significant diachroneity of the Precambrian tectono-magnetic events between the STT and the Northern Tarim terrane (NTT), we argue that the Precambrian basement of the Tarim were most likely composed of two distinct terranes (i.e., the STT and the NTT). These originated from different Precambrian nuclei and they did not amalgamate as the Tarim block until to the early middle Neoproterozoic