The northern margin of the Tarim Block (NTB) is an essential tectonic unit for understanding the tectonic-sedimentary system and geodynamic mechanisms of the Tarim Block and the surrounding region. Five Ordovician limestone samples and six Silurian sandstone samples were collected from the Keping-Bachu area, an early Paleozoic platform basin. Detrital zircon U-Pb chronology analysis shows that most of the early Paleozoic samples yield evident detrital zircon U-Pb age peaks of 454 Ma, 768/804 Ma, 976 Ma, 1818 Ma, and 2372 Ma. However, there was a 1000–940 Ma gap in the igneous rock records of the NTB, which means no magmatic provenance corresponding to the early Neoproterozoic detrital zircons with a peak age of ca. 976 Ma. Based on comparisons with potential provenance areas, the Yili-Central Tianshan Block (YCTB) may be the missing source, which was migrated to the NTB after the mid-Neoproterozoic orogenic event. The detrital zircon U-Pb age spectra of different regions in the NTB are significantly different. The early Paleozoic detrital zircons were abundant in the Ordovician strata in Keping-Bachu, but rare in Tabei and Quruqtagh. With the Hf isotopic compositions, the early Paleozoic detrital zircons came from the Southwest Tarim during the late Ordovician. Here, we present a bidirectional model for the provenance supply of the northwestern platform controlled by Tabei Uplift and Southwest Uplift. Moreover, the proportion of 480–420 Ma detrital zircons in Silurian strata gradually decreased from east to west, implying that the magmatic activity in the northern margin gradually weakened along the margin. By comparing the peak ages of early Paleozoic detrital zircons in the northwestern platform (435–434 Ma), Tabei (436 Ma), and Quruqtagh (454–450 Ma), we propose that the northeastern margin had transformed into an active continental margin in the late Ordovician, while the northwestern margin was later than it.

中文翻译：

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塔里木盆地西北地台奥陶系-志留系地层碎屑锆石U-Pb年代学：对物源系统和构造演化的启示


塔里木地块北缘（NTB）是认识塔里木地块及周边地区构造沉积体系和地球动力机制的重要构造单元。在早古生代台地盆地柯坪-巴楚地区采集了奥陶系灰岩样品5个和志留系砂岩样品6个。碎屑锆石U-Pb年代学分析表明，大部分早古生代样品均存在明显的碎屑锆石U-Pb年龄峰值，分别为454 Ma、768/804 Ma、976 Ma、1818 Ma和2372 Ma。然而，NTB火成岩记录中存在1000~940 Ma的差距，这意味着没有与峰值年龄约为1000年的新元古代早期碎屑锆石相对应的岩浆物源。第976章通过与潜在物源区的比较，伊犁-中天山地块（YCTB）可能是缺失的物源，它是在新元古代中期造山运动后迁移到NTB的。 NTB不同区域的碎屑锆石U-Pb年龄谱存在显着差异。柯坪—巴楚奥陶系地层中早古生代碎屑锆石含量丰富，而塔北和库鲁克塔格地区则很少见。从Hf同位素组成来看，早古生代碎屑锆石来自晚奥陶世塔里木西南地区。在这里，我们提出了塔北隆起和西南隆起控制的西北台地物源供应的双向模型。此外，志留系地层中480~420 Ma碎屑锆石的比例由东向西逐渐减少，表明北缘岩浆活动沿边缘逐渐减弱。 通过比较西北地台（435~434 Ma）、塔北地台（436 Ma）和库鲁克塔格（454~450 Ma）早古生代碎屑锆石峰值年龄，我们提出东北边缘在2007年已经转变为活动大陆边缘。晚奥陶世,西北缘晚奥陶世。