Deformation Characteristic Analysis And Discussion On The Deformation Environment Of The Erlangdong Accretionary Complex,Northern Margin Of Qaidam Basin

An accertionary complex outcrop in the Erlangdong area,northern margin of the Qaidam basin(NQB),comprises different age and different type rocks.However,previous works about this accertionary complex were mainly focused on its constitution and formation time but the deformation characteristics and timing were still overlooked,which constrains the study on the tectonic evolution of the NQB.Detailed field investigation indicates that the Erlangdong accrertionary complex is primarily composed of banded migmatite,granulite,biotite-plagioclase gneiss,amphibolite,marble,chlorite-quartz schist,and granitic gneiss,and records two deformation events.The earlier deformation(Di)featured regional penetrative foliation(S1,232°?49°),S-C fabrics,? and ? rotated prophyroclasts,and shear folds,and resulted in the occurence of L and L-S tectonites,suggesting a sinistral strike-slip shearing with thrust component.The stretching lineations in the L tectonites plunged to the SE(around 142°)at 2°-54°,approximately parallel to the NQB.The later deformation(D2)occurred at smaller regions and was featured by S-C fabrics and kink band structure,which revealed a dextral strike-slip with normal faulting component and partially modified the Di.LA-ICP-MS zircon dating yields early Paleozoic ages of 457 Ma and 406 Ma for the L tectonites and undeformed andesitic sub-volcanic rocks intruding into the L tectonites,respectively.Therefore,deformation timing of the L tectonites can be restricted to between 457 Ma and 406 Ma:The fabric analysis of quartz and feldspar suggested the deformation temperature of the L tectonites ranges from 470? to 500?with corresponding depths of 12-14 km.Based on the deformation and petrographic studies on the L-tectonites,in combination with the temporal framework of the early Paleozoic magmatism in NQB,we concluded that the protoliths of the L and LS tectonites may be early Paleozoic granites generated during the northward subduction of the Proto-tethys Ocean.Moreover,the D1 deformation likely occurred as a result of the oblique collision between Qaidam-East Kunlun block and Qilian block but the D2 deformation were related to the post-orogenic extension.