古阿尔金断裂的岩石构造依据及意义

本文把元古宙阿尔金断裂称为古阿尔金断裂，以区别于第三纪以来左旋剪切的阿尔金断裂。古阿尔金断裂具有右旋剪切的运动学特点，规模大，至少影响到地壳中部层次，并伴有同剪切就位的伟晶岩体。由于塔里木地块与华北陆台之间的汇聚碰撞在时间上晚于柴达木地块与华北陆台之间的汇聚碰撞，所以古阿尔金断裂是在新元古代超大陆汇聚过程中，塔里木地块相对于柴达木地块大规模东移在地块边界走滑剪切的产物。

LITHO-STRUCTURAL EVIDENCES OF ANCIENT ALTYN TAGH AND ITS SIGNIFICANCE

Altyn Tagh Fault is located in northwestern China, extending for more than 1500km in NEE direction. To the north is Precambrian Tarim block (TTG and khonalite series),and to the south are Precambrian Qaidam block(Precambrian metarnorphic basement with unclearconstitution) and CaledOnian Qilian Mountain orogenic belt. This fault has intermittently been inactivity since Proterozoic. This paper terms the fault occurred during Proterozoic as Ancient AltynTagh Fault (AATF) in order to distinguish from the sinistral shearing fault revived sincePaleogene. AATF is characteriZed by a large scale of dextral shearing that effected to the middlelevel of crust at least, and some syn-shearing intrusive pegmatites with the U-Pb signal zircon ageof 910 Ma.Recently, two Nooproterozoic granite-eclogite belts have been discovered near the AltynTagh. One is the Liuyuan belt between Tarim block and North China block and the other is thebelt Of northern edge of Qaidam between Qaidam blOck and North China blDck (or anotheruncertain block). The former yield U-Pb single zircon ages of 9OO - 95OMa, the latter 86O -880Ma, which implies that the col1ision between the Qaidam b1ock and the North China block isearlier than that between the Tarim bfork and the North China block.ln the assembly process of Neoproterozoic supercontinent, AATF may be the margin strikeslip shear sone produced by a large sca1e motion of Tarim block eastwards Qaidam blOck after thecollision between Qaidam and North China blocks, and then at about 86O ~ 88O Ma, Tarim blockrnoved to the border of North China block and began to collide with it.