塔里木克拉通基底古隆起构造-热事件及其结构与演化

通过盆地内部锆石U-Pb测年分析表明,塔里木克拉通基底存在2950～ 3100Ma、2100 ～ 2400Ma、1900～2000Ma、1300～1600Ma、900 ～ 950Ma、700～800Ma、540 ～ 560Ma、400～ 500Ma和270～290Ma等9期构造-热事件.中央航磁异常带井下花岗岩锆石SHRIMP U-Pb年龄测定发现1908.2±8.6Ma前寒武纪基底,表明盆地内部可能存在古元古代构造-热事件形成的古老花岗岩基底.结合新的地质与地球物理资料综合分析,塔里木盆地前寒武纪具有不同年代、不同类型的基底结构,北部为中-新元古代中浅变质岩基底、中部为古元古代花岗岩基底、南部为新元古代早-中期岩浆岩与变质岩基底、东南部为遭受早志留纪区域变质改造的变质岩基底.井震结合发现塔里木盆地寒武系/前寒武系发育广泛分布的大型不整合,形成塔北与塔南两大前寒武纪基底古隆起,可能与550Ma“泛非运动”相关.塔里木盆地基底古隆起主要经历5期演化,古元古代中期形成克拉通化基底,新元古代早期形成统一的变质结晶基底,寒武纪沉积前两大基底古隆起形成,加里东晚期五大基底古隆起基本定型,海西期以来发生局部调整改造.

The tectonothermal events, architecture and evolution of Tarim craton basement palaeo-uplifts

Based on the U-Pb zircon dating analysis within Tarim basin, it is indicated that there were 9 stages of tectonothermal events of the Precambrian basement with the peak age of 2950~3100Ma, 2100~2400Ma, 1900~2000Ma, 1300~1600Ma, 900~950Ma, 700~800Ma, 540~560Ma, 400~500Ma and 270~290Ma. The SHRIMP U-Pb zircon dating of the central aeromagnetic anomaly zone yields the age of 1908.2±8.6Ma, which revealed that there was granitoid basement by Palaeoproterozoic tectonothermal event. By the dating data with new geology and geophysics data, there are different age and type of Precambrian crystalline basements in Tarim basin,which divided into the northern basement with Meso-Neoproterozoic low-to medium-grade metamorphic rocks, the middle basement of Palaeoproterozoic granite, the southern basement with Early-Middle Neoproterozoic magmatite and metamorphite, the southeastern metamorphite basement undergone reformation in Early Silurian epimetamorphism. It is found that there is a wide range unconformity between Cambrian and Precambrian by well and seismic date,which developed the northern and southern basement palaeo-uplifts as the result of the potential influence of Pan-African orogenic occurred about 550Ma. The basement palaeo-uplifts undergone 5 stages evolution: the cratonization miniature basement in Archean-Middle Palaeoproterozoic,the united metamorphic crystalline basement in Early Neoproterozoic,the two basement palaeo-uplifts formative stage before Precambrian,the five basement palaeo-uplifts complete period in the late of Caledonian and local regulation since Hercynian.