大兴安岭东北部侏罗纪花岗岩类Sr-Nd同位素特征及其地质意义

Sr-Nd isotopic characteristics of Jurassic granites in northeastern Da Hinggan Mountains and their geological implications

大兴安岭东北部侏罗纪花岗岩类的Sr-Nd同位素研究结果表明,兴安地块侏罗纪花岗岩具有较低的初始锶值(0.7048～0.7065)、高的εNd(t)值(+0.23～+2.54)和较低的TDM2(0.76～0.95Ga),反映其源区物质主要为显生宙期间从亏损地幔增生的地壳物质。额尔古纳地块侏罗纪花岗岩具有相对较高的初始锶值(0.7057～0.7075)、较低的εNd(t)值(-2.47～-9.72)和较高的TDM2(1.16～1.7Ga),反映其源区物质主要为中—新元古代从亏损地幔增生的地壳物质。额尔古纳地块和兴安地块各自具有不同的地壳增生时期,表明它们具有不同的早期地壳演化历史。

Sr-Nd isotopic data of the Jurassic granites in northeastern Da Hinggan Mountains show that Xing＇an massif has relatively low initial Sr（0.7048～0.7065）,high εNd（t）（＋0.23～＋2.54）,and low TDM2（0.76～0.95 Ga）,suggesting that their source materials were mainly crustal materials derived from the depleted mantle during Phanerozoic.In contrast,Jurassic granites in Ergun massif have relatively high initial Sr（0.7057～0.7075）,low εNd（t）（-2.47～-9.72）,and high TDM2（1.16～1.7 Ga）,implying that their source materials were mainly crustal materials derived from the depleted mantle in Meso-Neo-Proterozoic.Different crustal accretion periods of Ergun and Xing＇an massifs suggest they have different early crustal evolution histories.