黑龙江东部伊春-延寿晚三叠世-早侏罗世花岗岩岩基带深部约束机制

Deep constraints mechanism of late Triassic-early Jurassic Yichun-Yanshou granite batholith belt,eastern Heilongjiang

通过对新近编制完成的1∶50万黑龙江省地质矿产分布图特征的总结,基于大量最新地质资料、科研成果的分析,厘定了松嫩地块东部的地层单位,重新构建了该区地质构造格架。依据研究区地球物理特征,伊春—延寿晚三叠世—早侏罗世花岗岩的闪长质包体、Hf同位素组成、锆石U-Pb年龄、A型花岗岩构造背景等讨论了伊春—延寿花岗岩基带的形成过程,即早中生代佳木斯地块—松嫩地块碰撞促使地壳加厚,佳木斯地块板片前缘断裂诱发软流圈地幔上涌并发生壳幔混融,形成岩基带主体(二长花岗岩)岩浆。此后,板片根部断离并伴随局部岩石圈的拆沉,促使区域构造背景转入崩塌—伸展机制,形成A型花岗质岩浆,由此形成了平行于俯冲碰撞带呈南北向展布的伊春—延寿晚三叠世—早侏罗世花岗岩岩基带,及出露于牡丹江断裂东侧的黑龙江群—构造混杂岩。

Based on summary on the newly compiled Heilongjiang geological map at a scale of 1 ： 50 000 and integrated analysis on the latest geological achievement,the stratum located in the eastern Sougnen block was redefined and the geological tectonic frame- work was re-constructed. The mechanism process of the granite batholith belt was discussed on the basis of studying regional geophysics characteristics, dioritic inclusion within late Triassic-Early Jurassic granite batholith in Yichun and Yanshou areas, Hf isotopic compo- sition, zircon U-Pb isotopic ages and tectonic setting of A-type granite. In the early Mesozoic period, the crust was thickened after Jia- musi block collided with Songnen block. The break off of the subducted Jiamusi slab triggered asthenosphere mantle upwelling, then re- suited in the melting of the crust and mantle, then the main batholith body（ monzonitic granite） was formed. After that, the separation of the root of plate and lithosphere delamination brought the region into the extensional setting, then the A-type granitic magma was generated. The Yichun-Yanshou granite batholith of late Triassic-Early Jurassic outcropped along south-north direction, which paral- lels to the collision zone, and the Heilongjiang complex was exposed to Mudanjiang fault.