Detrital zircon U-Pb dating from Tiekelike of southwestern Tarim Basin: Implications for the age and composition of Bochatetag Formation

The Bochatetag Formation outcrops at Tiekelike on the southwestern margin of the Tarim Craton. The sedimentary rocks of the formation contain conglomerate and shallow-marine carbonatite. Previous researchers assigned its formation age to Mesoproterozoic Jixian System. Detrital zircons in conglomerate on the base of the Bochatetag Formation yielded U-Pb ages ranging from 2.3 to 1.9 Ga, with the youngest detrital zircon concordant age being 1953 Ma. In contrast, the overlying marble in the middle-upper formation which contains significant Neoproterozoic detrital zircon grains has ages ranging from 0.77 to 0.85 Ga, with the youngest detrital zircon concordant age being 772 Ma. Therefore, the composition and age of the Bochatetag Formation should be redefined. The carbonatite constitutes the main composition of the formation and its formation age should be of the Nanhua system. The concordant age of 772 Ma represents the maximum deposition age.