锆石U-Pb测年与综合地球物理方法研究塔里木盆地前寒武基底结构特征

Zircon U-Pb Dating and Comprehensive Geophysics Study on the Structural Features of Precambrian Basement in Tarim Basin

塔里木盆地的基底结构研究对其沉积演化和烃源岩分布具有重要意义。通过锆石U-Pb测年,并结合钻井、地震等资料,探讨了塔里木盆地前寒武基底结构属性和形成演化特征。研究表明,中央航磁异常带盆地内钻井揭示的花岗岩锆石U-Pb年龄测定发现了1.9 Ga前寒武纪基底,南北塔里木块体可能在该时期拼合;中央隆起带发育前寒武纪古陆,控制南华系-震旦系-下寒武统地层向中央古陆逐渐尖灭;周缘南华系-震旦系露头地层发育特征反映塔里木盆地在早期演化阶段存在多个大小不等的、彼此孤立的裂陷中心,一般都经历了快速的填平补齐;中央隆起带寒武系沉积前总体为多个古隆起发育区,基底零星出露,震旦系地层遭受不同程度的剥蚀,古隆起区玉尔吐斯组沉积缺失或发生相变,古隆起之间坳陷区可能发育玉尔吐斯组。

The study of basement structure in Tarim basin is of great significance to its sedimentary evolution and source rock distribution.Based on zircon U-PB dating,combined with drilling and seismic data,the structural properties,formation and evolution features of the Precambrian basement in Tarim basin are discussed.It turms out that,U-Pb dating of granite zircons drilled in the central aeromagnetic anomaly basin reveals a Precambrian basement of 1.9Ga,during which the north and south Tarim blocks may have been fused together.The central uplift zone developed the Precambrian ancient land and controlled the south China-Sinian-lower Cambrian strata to gradually cusp out the central ancient land.The development of Nanhua-Sinian outcrop strata around the Tarim basin reflects the existence of several different and isolated rift centers in the early evolutionary stage of the Tarim basin.Before the deposition of Cambrian in the central uplift zone,there were several developing areas of ancient uplift,the basement was scattered,the Sinian strata suffered from different degrees of denudation,the deposition of Yuertuis Formation in the ancient uplift zone was absent or underwent phase change,and the depression area between the ancient uplift may have developed Yuertuis formation.