The latest Neoproterozoic basaltic and siliciclastic rocks and tectonic implications in the Tarim Craton, NW China

Abstract

The Tarim Craton records protracted late Neoproterozoic rifting that overlaps with the breakup of Rodinia and assembly of Gondwana. However, the timing and interactions of these two tectonic processes remain contested. To constrain the tectonic significance of this prolonged rifting event, we present LA-ICP-MS zircon U–Pb ages and geochemical data from mafic and (meta)sedimentary rocks at the top of the craton’s Ediacaran succession. Two basalt samples from the northwestern Tarim Craton contain inherited zircon grains with a wide range of U–Pb ages, the youngest at ca. 620 ± 11 providing a maximum age for the magmatism. The youngest detrital zircon U–Pb ages from the southwestern and northern Tarim Craton are ca. 607 Ma and 617 Ma, respectively. Integrated with compiled magmatic and detrital zircon U–Pb ages, our study suggests that an episode of latest Neoproterozoic (ca. 620–600 Ma) magmatism occurred throughout the Tarim Craton. The Ediacaran mafic rocks form a transitional eruptive series between alkali and tholeiitic basalts derived from lithospheric mantle with slight crustal contamination and formed in an intra-continental rifting environment through mantle reactivation during post-subduction extension. Positioned at the outer margin of Rodinia, it is considered unlikely that the magmatism records prolonged plume-related breakup. Instead, it is thought to reflect rifting of an active continental margin in a fashion analogous to many of the peri-Gondwanan terranes, possibly related to the subduction mechanism of supercontinental breakup.