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

摘要: 提要：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 ~0.95 Ga），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 ~ 1.7 Ga），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。

Abstract: Abstract：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.