塔里木陆块在Rodinia超大陆中位置的新认识——来自地层对比和古地磁的制约

New opinion on the position of the Tarim block in the Rodinia supercontinent:Constraints from stratigraphic correlation and paleomagnetism

塔里木周缘的新元古代地层中均记录了涉及Rodinia聚合和裂解的构造热事件,但塔里木在Rodinia超大陆中位置尚存争议.本文综合地层对比以及古地磁的研究方法,将塔里木陆块在Rodinia超大陆中置于澳洲板块的西北缘,并且塔里木的西南缘（现今位置）和澳洲的西北缘（现今位置）相连.基于塔里木周缘的构造热事件和塔里木、澳洲运动学特征分析,认为塔里木陆块周缘在约800～700 Ma中发生了强烈的裂谷事件,导致塔里木从Rodinia超大陆中裂解,但塔里木并没有完全从澳洲裂离,而是随澳洲一起,加入冈瓦纳大陆.在约450 Ma左右,塔里木与澳洲发生分离,其原因为古特提斯洋的扩张.

The Tarim block is one of the most important blocks of China.The Neoproterozoic strata which are distributed on the periphery of the Tarim block record lots of tectonothermal events related to the assembly and breakup of the Rodinia supercontinent.But the position of the Tarim block in Rodinia,the relationship between the Tarim block and Australia plate and the movement pattern of the Tarim block from Neoproterozoic to early Paleozoic remain controversial.Based on the method of stratigraphic correlation and paleomagnetism,we discuss these questions. The Neoproterozoic strata of Tarim are mainly distributed along its periphery.Based on the field work,we analyze the stratigraphic correlation of Neoproterozoic strata in Tarim（including the Aksu area in northwest,Quruqtagh area in northeast and Tiekelike area in southwest）and corresponding strata in Australia to discuss the relationship between the Tarim block and Australia plate in Rodinia.Besides,we collect and select the published paleomagnetic data（Q≥4）of Tarim and Australia plate from Neoproterozoic to early Paleozoic,and build the APWP（apparent polar wander path）and reconstruct the paleolatitude of Tarim and Australia Plate from Neoproterozoic to early Paleozoic,so that we can estimate the separation time of Tarim block and Australia plate and the drift path of Tarim. From the stratigraphic correlation of the Tarim block and Australia plate,the Neoproterozoic strata in the northwest,northeast and southwest of Tarim are very similar,so are the strata in Australia.They are all characterized by continental rift-littoral and neritic facies sediments,which all have several layers of tillite.So the Tarim block might be close to the Australia plate in Rodinia,but the relative orientation between Tarim and Australia need to be constrained by the paleomagnetic method.The APWP of the Tarim block and Australia plate from Neoproterozoic to early Paleozoic are similar.In the reconstruction map,the paleolatitudes of Tarim and Australia from Neoproterozoic to Ordovician are also similar.After 450 Ma,the Tarim block drifted northward rapidly,while Australia plate drifted southward slowly. Based on the method of stratigraphic correlation and paleomagnetism,we reconstruct the Tarim block on the northwest edge of the Australia plate and the southwest edge of Tarim（the present position）connects with the northwest edge of Australia（the present position）in Rodinia.There was a strong rifting event surrounding Tarim during 800～700Ma,which caused Tarim to break off the Rodinia supercontinent.However,the separation was not complete,Tarim joined Gondwana along with Australia.At the time of about 450 Ma,Tarim was totally separated from Australia as a result of the expansion of the Paleo-Tethys ocean.