Application of U-Pb dating in the study on the provenance analysis of detrital zircons in the southern margin of Junggar Basin,China

The piedmont structural zone of Yilinhebilgen Mountain is the important suture orogen belt of the foreland basin of the south margin of Junggar Basin with the organ belts of northern Tianshan,Northwest China.Four sandstone samples,formed in Mesozoic,were collected from the piedmont structural zone.The U-Pb age of 250 detrital zircons contained in the sandstone samples were analyzed by LA-ICP-MS method.Based on the age distribution,mineralogical characteristics and CL images of the detrital zircons,combined with the constraints of palaeocurrent,the provenance and structural setting of the detrital zircons can be analyzed.It is shown that,their ages are in a wide range of 170 ~ 2 886 Ma.The youngest detrital zircon is in(170±1)Ma,implying that this sequence of the strata is not older than Middle Jurassic;the age of older detrital zircons in 2 200～2 900 Ma and 1 000～1 600 Ma,they may be from the erosion area of old basement rocks after Yanshan Movement of Tianshan;the zircons whose age in 290～310 Ma and 400~410 Ma are from both areas,mostly from Yilinhebilgen Mountain and partly from the south of Middle-Tianshan Mounts;the age peak values of 170～200 Ma indicate that,marked uplift and erosion are occurred in North Tianshan Mounts and the south margin of Junggar Basin during late Jurassic,and the provenance of the zircons may be in the north slope of Tianshan Mounts.