塔北古隆起形成时间研究：来自锆石U-Pb年代学和超深层楔形结构的限定

The Tabei paleo-uplift in the Tarim Basin is one of the key regions of deep petroleum exploration in western China. Its initiation and evolution are still unclear due to deep burial, serious erosion and complex structure. According to basin research in regional scale, the Nanhuan and Sinian strata were deposited in the northern rift basin with an overlapping law from the rift center to the Tabei paleo-uplift, showing a syn-depositional wedge-shaped structure. And also, some deep drillings reveal that the Paleoproterozoic-early Mesoproterozoic igneous rocks might be distributed in the Tabei paleo-uplift, while the middle Mesoproterozoic- Neoproterozoic detrital zircons were mainly deposited around the paleo-uplift, which are different but probably interrelated between their provenances. These preliminary evidences show that the Tabei paleo-uplift may be formed earlier than the Caledonian-Haixian period in the majority view. Based on outcrops, drilling and seismic data, this study aims to comprehensively analyze the detrital zircons U-Pb age and their provenances, establish gridded geological sections of the Tabei paleo-uplift, and decipher the characteristics and formation of the syn-depositional wedge-shaped structure, defining the initiation age of the Tabei paleo-uplift and its paleogeographic pattern. This study can provide basin evidence for the Precambrian tectonic evolution of the Tarim Craton, but also effectively predict the ultra-deep source rocks and petroleum distribution.

塔里木盆地塔北古隆起是我国西部深层油气勘探关注的重点区域之一，由于埋藏深、剥蚀程度高、构造复杂等因素导致其形成演化认识并不明确。从盆地区域尺度解析超深层发现：新元古代发育北部裂谷盆地，南华系、震旦系由裂谷中心向塔北古隆起处超覆减薄，表现出同沉积成因的楔形地质结构特征；深钻井揭示塔北古隆起可能发育古元古代-中元古代早期火成岩，而古隆起周缘前寒武系-寒武系碎屑锆石年龄主要为中元古代中期-新元古代，二者物源可能存在区别与联系。这些证据均初步表明塔北古隆起形成时间可能更早于多数学者认为的加里东期-海西期。本研究拟综合利用露头、钻井及地震数据，分析碎屑锆石U-Pb年龄与物源，建立塔北古隆起的网格化地质剖面，剖析超覆型楔形地质结构特征及形成过程，明确塔北古隆起形成时间及隆坳格局，为恢复塔里木克拉通前寒武纪构造过程提供盆地响应证据，有效指导超深层烃源岩和油气分布预测。

塔里木盆地塔北古隆起是我国西部深层油气勘探关注的重点区域之一，由于埋藏深、剥蚀 程度高、构造复杂等因素导致其形成演化认识并不明确。本研究拟综合利用塔北古隆起及周缘露头、钻井及地震数据，分析碎屑锆石U-Pb年龄与物源，剖析超深层超覆型楔形地质结构特征及形成过程，明确塔北古隆起形成时间及隆坳格局。. 通过锆石U-Pb年代学测定了五个沉积岩样品的年龄，进行其沉积年龄限定和区域地层对比。Yuli地区的前寒武纪地层属于上成冰纪-下埃迪卡拉纪（约660 Ma）；Sawapuqi地区的前寒武纪地层属于埃迪卡拉纪（约595 Ma）；Wikiritag地区的地层属于早古生代（约410 Ma）。. 对这5个新样品和54个已发表的新元古代样品中3962个锆石的分析揭示了其U-Pb年龄谱的时间和空间变化。从塔里木克拉通北部外围到塔北隆起，在同一时期（如拉伸纪、成冰纪和埃迪卡拉纪），新元古代锆石的比例降低，而新太古代-古元古代锆石的比例增加。对于同一位置，从拉伸纪到埃迪卡拉纪，新元古代锆石的比例降低，而新太古代-古元古代锆石的比例增加。同时在地质与地震剖面中，塔里木克拉通北部新元古界发育楔形地层结构，新元古代同时形成塔里木北部造山带和相邻裂谷盆地，造山带为周边盆地提供物源。本次研究发现，塔里木克拉通北部发育古元古代、新元古代两期造山带旋回。古元古代造山带起始于约1.9–1.8 Ga，终止于约1.8 Ga；新元古代造山带开始于约900–740 Ma，终止于大约600 Ma。新元古代盆山格局受控于罗迪尼亚超大陆边缘裂解过程，两期造山带继承演化为现今塔北隆起。. 研究成果不但可以为超大陆重建提供盆地响应证据，而且指导超深层古老层系油气勘探，具有重要的理论和现实意义。