The formation time and tectonic significance of Yuejinshan accretionary complex in eastern Heilongjiang Province
Objectives and Methods:The Yuejinshan and Raohe accretionary complexes in the Nadanhada Mountains terrane can provide important geological evidence to reconstruct the subduction—accretion process of the Paleo-Pacific Plate and reveal the tectonic transformation process between the Paleo-Pacific Ocean and Paleo-Asian Ocean.However,the time of the initial subduction of the Paleo-Pacific slab under Eurasia Plate and the properties of the ancient ocean related to the Yuejinshan accretionary complex are still controversial.Based on the field geological survey of the Yuejinshan accretionary complex,zircon U-Pb geochronology and geochemical tests of the matrix and rocks were carried out.Combined with the existing research results,the accretion and in-situ age of the Yuejinshan accretionary complex was further limited,providing evidence for the subduction—accretion process of the paleo-Pacific Plate.Results:This field survey shows the Yuejinshan accretionary complex has a typical structure of"matrix and block"in terms of rock assemblage.Through this study,The geochemical compositions of the green schist block are similar to those of ocean the island basalt.The U-Pb zircon age of the green schist is 194.7±4.8 Ma,and the U-Pb age of detrital zircons of the meta-argilaceous siltstone in matrix show that the depositional age is not earlier than 233.1±5.1 Ma.Combined with the published geochronological data on the region,it is believed that the accretionary age of the Yuejinshan accretionary complex is mainly Triassic.Conclusions:Combined with previous research results,it is believed that the accretionary age of the Yuejinshan accretionary complex is mainly Triassic,its sediment source is mainly from the rocks in Jiamusi block and sillar in accretionary complex,the final location age is Early Jurassic,it is the product of subduction—accretion of the paleo-Pacific plate and records the process of subduction—accretion of the paleo-Pacific plate.
万方数据
维普
