华北、华南、塔里木三大陆块中-新元古代岩浆岩的特征及其地质对比意义

The characteristics of Meso-Neoproterozoic magmatic rocks in North China,South China and Tarim blocks and their significance of geological correlation

我国三个主要的古老陆块(华北、华南和塔里木陆块)都发育中-新元古代岩浆岩。根据大量的同位素年代学资料,华北陆块中-新元古代岩浆事件可以分为7个阶段,其中1.78Ga和1.32Ga两期影响范围较大,可以构成大火成岩省。华北陆块中-新元古代的岩浆岩均形成于大陆地壳伸展的构造背景,意味着华北并未介入Rodinia超大陆的聚合过程。华南陆块中-新元古代岩浆事件可以分为8个阶段,从1.78Ga到1.5Ga的四期岩浆事件形成于大陆地壳伸展的构造背景,1.4Ga左右的一期岩浆-构造事件分布局限,可能形成于局部的构造拼合背景。1.0Ga左右的岩浆事件,在华南陆块的不同部位表现形式不同,意味着发生过不同地块的拼合。从0.95Ga到0.82Ga的岩浆事件主要分布在江南造山带和扬子地块北缘,这一阶段的岩浆事件导致扬子地块和华夏地块拼接成一体,形成华南陆块。之后从0.78Ga到0.72Ga的岩浆事件几乎遍布华南陆块,反映了陆块形成后的伸展过程。塔里木陆块中-新元古代的岩浆事件可以分为8个阶段,1.78Ga和1.5Ga的岩浆事件仅在局部有反映,它们形成于拉伸的构造背景。1.4Ga的岩浆事件在塔里木陆块的北缘和西南缘表现形式不同,北缘钙碱性岩浆岩形成于大陆弧构造背景,而西南缘A2型花岗岩则形成于拉伸的构造背景。0.96~0.88Ga期间,塔里木东南缘和北缘的花岗岩以I型和S型为特点,形成于活动大陆边缘,而在塔里木陆块的西南缘该时期则形成了塞拉加兹塔格群中双峰式火山岩,形成于陆内裂谷环境。0.88~0.82Ga期间,在北缘的库鲁克塔格地区形成了与俯冲增生相关的岩浆岩组合,而在东南缘则形成了与拉张构造环境有关的双峰式火山岩。塔里木陆块不同部位,不同阶段岩浆岩组合的差异意味着塔里木陆块原来并不是一个统一的陆块,很可能是在不同时期由不同块体拼合而成的。华北、华南和塔里木三个陆块中-新元古代岩浆岩的差异演化,揭示了它们各自形成陆块的过程和方式及相互关系。

Meso-Neoproterozoic magmatic rocks widely occur in three Chinese blocks of China(North China,South China and Tarim blocks).Based on a large number of geochronologic data,the Meso-Neoproterozoic magmatic events in the North China Block can be divided into seven stages(1.78 Ga,1.70 Ga,1.63 Ga,1.32 Ga,1.23 Ga,0.93 Ga and 0.83 Ga),in which 1.78 Ga and1.32 Ga magmas have a large influence range and form the large igneous provinces,respectively.The Meso-Neoproterozoic magmatic rocks in the North China Block formed in the intracontinental extensional environment indcating that North China Block was not involved in the assembly process of the Rodinia supercontinent.The Meso-Neoproterozoic magmatic events in the South China Block can be divided into eight stages(1.78 Ga,1.72 Ga,1.67 Ga,1.5 Ga,1.42 Ga,1.0 Ga,0.84 Ga and 0.77 Ga),the four stages of magmatic events from 1.78 Ga to 1.5 Ga were formed in extensional environment.The sporadic 1.4 Ga magmatic rocks likely formed in an assembly setting in local area.The magmatic stages around 1.0 Ga performed differently in different parts of the South China Block,indicating the different blocks have been aggregated together.Magmatic events from 0.95 Ga to 0.82 Ga,mainly distributed in the Jiangnan Orogen and the northern margin of the Yangtze massif,led to the coherent Yangtze massif(or Yangtze Block)and Cathaysia massif(or Cathaysia Block)into the South China Block.Subsequently,magmatic events from 0.78 Ga to 0.72 Ga were almost all over the South China Block,reflecting the extensional process after the formation of the entire continental block.The Meso-Neoproterozoic magmatic events in the Tarim block can be subdivided into eight stages(1.78 Ga,1.5 Ga,1.43 Ga,1.1 Ga,0.92 Ga,0.83 Ga,0.74 Ga and 0.65 Ga).The magmatic events of 1.78 Ga and 1.5 Ga are only locally distributed,and they formed in the extensional setting.1.4 Ga magmatic events performed differently in the northern and southwestern margins of the Tarim Block.Calc-alkaline magmatic rocks in the northern margin emplaced in the continental arc setting,while A2 type granites in the southwestern margin were formed in the tensional setting.During the period of 0.96~0.88 Ga,the granites in the southeastern and northern margins of Tarim Block are dominated by I-type and S-type and formed in the active continental margin,while in the southwestern margin of Tarim Block,bimodal volcanic rocks in the Sailajiazitage Group formed in the intra-continental rift environment.During 0.88~0.82 Ga,magmatic sequences,related to subduction and accretion,were formed in Kuruktagh area on the northern margin,while bimodal volcanic rocks related to extensional tectonic setting were formed on the southeastern margin.The difference of magmatic rock assemblages in different locations and stages of the Tarim Block denotes that the Tarim Block originally is not originally a unified block,but likey assembled by different massifs in different periods.The differential evolutions of the Meso-Neoproterozoic magmatic rocks reveal their independent processes in the North China,South China and Tarim blocks in this period.