塔里木盆地碎屑锆石年龄分布对前寒武纪基底的指示

The Distribution of Detrital Zircon U-Pb Ages and Its Significance to Precambrian Basement in Tarim Basin

应用碎屑锆石LA-ICP-MS U-Pb定年方法研究塔里木盆地前寒武纪基底与超大陆的关系,对盆地内部不同地区井下11个碎屑岩样品进行锆石年代学分析。塔里木盆地南部与北部分别检测到早元古代、中元古代产生的物源,结合周边造山带测年资料分析佐证了早中元古代塔里木南北块体演化有差异,北部大量的中元古代早期年代数据可能预示塔北微块体存在与Columbia超大陆裂解时间相近的构造-热事件。南北塔里木在新元古代早期才发生碰撞拼合形成统一的基底与演化进程,所有样品都检测到南华纪年龄数据证实塔里木板块及其周缘在此期发生大规模裂解事件,南华纪大规模火成岩活动形成了盆地显生宙碎屑岩最主要的蚀源,塔里木板块存在与Rodinia超大陆裂解时间相当的构造-热事件。碎屑锆石测年资料为研究塔里木板块与超大陆的关系提供了来自盆地内部的证据。

In order to get the information concerning the relationship between the Tarim Precambrian basement and the supercontinent,the authors analyzed the U-Pb isotopic ages of zircons from 11 clastic rocks in different areas of Tarim Basin in situ by means of LA-ICP-MS.The results show that there existed Early Paleoproterozoic provenance in northern Tarim and Middle Mesoproterozoic provenance in southern Tarim.An analysis of detrital zircon ages and data of surrounding orogenic belts indicates that a uniform Tarim basement did not exist in Paleoproterozoic and Mesoproterozoic,during which the North and South Tarim continents had different evolution events.The North Tarim continent probably had the same tectonic event as the breakup of Columbia supercontinent.The collision between North and South Tarim continents took place in Early Neoproterozoic,resulting in the formation of a uniform Tarim basement.All of the clastic rocks have Nanhuan ages,which indicates that there was a large scale breakup of the Tarim continent in Nanhuan period.The thermo-tectonic event in Nanhuan period provided widespread provenance of the cap rocks.The Tarim continent might have had the same tectono-thermal events as the breakup of the Rodinia supercontinent.These results have yielded new intraplate evidence for con-straining the relation between the Tarim plate and the supercontinent.