东北地块群:构造演化与古大陆重建

Combined NE China Blocks:Tectonic Evolution and Supercontinent Reconstructions

东北地区位于西伯利亚板块、华北板块和太平洋板块之间,为＂中亚造山带＂的东段和太平洋构造域的叠加部位,因此东北地块群构造属性和背景的研究对深入探讨二大构造域的叠加与转化背景具有重要的理论意义。东北地块群从东到西可细分佳木斯—兴凯、松辽、兴安和额尔古纳四大地块,这些地块具有相同的新元古代——泛非期变质基底,而古生代沉积岩也存在一定的可比性,表明这些地块存在相同或者相似的构造演化背景。分割这些地块的构造边界特征为：1）额尔古纳与兴安地块的缝合带为早古生代头道桥—新林缝合带,而非中生代德尔布干断裂;2）兴安地块与松辽地块之间的贺根山黑河缝合带形成时代为晚石炭世（330~300 Ma）,而非最近报道的中生代;3）古亚洲洋分布在东北陆块群与华北板块之间,沿西拉木伦—长春缝合带闭合,时代为三叠纪;4）佳木斯—兴凯地块与松辽地块之间的吉黑高压带形成于古亚洲构造域与环太平洋构造域转换的关键时期（210~180 Ma）;5）那丹哈达增生杂岩为中国境内古太平洋板块俯冲增生的唯一直接证据,并记录了晚三叠早白垩世古太平洋板块向欧亚大陆俯冲增生的过程。在此基础上,分析了东北地块群发育的典型古生物和年代学标志,重建了东北地块群从Gondwana大陆到Pangea大陆的位置与模型。

NE China has traditionally been considered as the eastern part of the Central Asian Orogenic Belt（CAOB）,located between the Siberia and North China cratons.They constitute Paleozoic accretionary margins to the Siberia and the North China cratons,terminated to the east by the PaleoPacific orogens.In detail,NE China is the key area for understanding the geodynamics between the CAOB and Paleo-Pacific subduction.The tectonic units of the combined NE China blocks（NEC）include the Jiamusi-Khanka blocks in the northeast,the Xing＇an and Songliao blocks in the central area,and theErguna block in the northwest.The basement rocks in NEC constitute a common khondalitic sequence of Neoproterozoic with high grade metamorphism occurred at ~500 Ma.The Paleozoic sediments also show slimier sequences in most blocks in the NE China,suggesting that the combined NE China blocks（NEC）might be have similar or same tectonic evolutions during that time.The boundary between these blocks show following new evidences：1）the suture zone between the Eerguna and Xing＇an blocks is the Early Paleozoic Toudaoqiao-Xinlin suture and not the Mesozoic Derbugan fault.2）the emplacement time of the Hegenshan-Heihe suture between the Xing＇an and Songlao blocks is the Late Carboniferous and not the Mesozoic as recently reported.3）the Paleo-Asian Ocean between the combined NE China blocks（NEC）and North China block is along the Xar Moron-Changchun suture and the collision timing is the Triassic.4）the collision timing of the Jilin-Heilongjiang high pressure metamorphic belt（Ji-Hei HP belt）between the Jiamusi-Khanka and Songliao blocks is the switch time when end of the CAOB and beginning the Paleo-Pacific subduction at sometime between 210 and 180 Ma,and 5）the Nadanhada accretionary complex is the only records for the Paleo-Pacific subuduction from Late Triassic to Early Cretaceous in NE China.In addition,we also focus on the evidences of the both typical tectono-magmatic events and Paleontologic signatures,and reconstruction of the NEC from Gondwana to Pangea supercontinent.