摘要
识别前寒武纪地质单元对了解松嫩地块物质组成和前寒武纪构造演化过程具有重要的科学意义。本文对出露于松嫩地块西缘龙江地区的花岗质岩石和乌兰浩特地区的斜长角闪岩进行了LA-ICP-MS锆石U-Pb同位素和Hf同位素分析。石英二长岩和二长花岗岩形成年龄分别为2480±12Ma和2544±23Ma,样品中存在~2.6Ga的继承锆石以及~2.0Ga的变质锆石,形成时代为新太古代;多数锆石ε_(Hf)(t)>0,二阶段模式年龄为2793~3019Ma,少量锆石ε_(Hf)(t)<0,二阶段模式年龄为3012~3138Ma,锆石Hf同位素特征表明松嫩地块西缘龙江地区存在新-中太古代的地壳生长事件,且在岩浆演化过程中受到中太古代古老地壳的混染。乌兰浩特斜长角闪岩存在2544±15Ma的继承锆石,形成年龄为2042±29Ma,形成时代为古元古代;多数锆石的ε_(Hf)(t)>0,二阶段模式年龄为2301~3015Ma,少量锆石ε_(Hf)(t)<0,二阶段模式年龄为2647~3073Ma,锆石Hf同位素特征表明乌兰浩特地区存在古元古代中期-中太古代的地壳生长事件,且在岩浆演化过程中受到新太古代古老地壳的混染。综合区域研究成果,松嫩地块西缘龙江-乌兰浩特地区存在~1.8Ga、~2.0Ga、~2.5Ga和~2.7Ga四期岩浆事件以及古元古代中期-新太古代晚期和新-中太古代的地壳生长事件,其构造岩浆热事件与华北克拉通及全球古老大陆地壳增生时限一致。
The discrimination of Precambrian geological units is helpful to understand the compositions and Precambrian tectonic evolution of the Songnen massif.In this paper,zircon U-Pb and Lu-Hf isotopes are reported for Longjiang granitic rocks(quartz monzonites and monzogranites)and Ulanhot amphibolites.LA-ICP-MS analysis shows the quartz monzonites were formed at 2489±12Ma with inherited zircons of 2539±16Ma.The monzogranites were emplaced at 2544±23Ma,including inherited zircons of 2605±18Ma and metamorphic ages of~2.0Ga.Amphibolites were formed at 2049±29Ma with inherited zircons of 2554±15Ma.Most of Neoarchean zircons have positiveε_(Hf)(t)values with t_(DM2) ages of 2793~3019Ma while a few zircons have negativeε_(Hf)(t)values with t_(DM2) ages of 3012~3138Ma,suggesting that the crustal growths occurred during Neoarchean and the primary magma should be influenced by reworking of the Mesoarchean crusts.The Middle Paleoproterozoic zircons in amphibolites mainly have positiveε_(Hf)(t)values with t_(DM2) ages of 2301~3015Ma while a few zircons have negativeε_(Hf)(t)values with t_(DM2) ages of 2647~3073Ma,indicating that the crustal growths occurred during Paleoproterozoic and Neoarchean and the primary magma should be influenced by reworking of the Neoarchean crusts.Four magmatic events(~1.8Ga,~2.0Ga,~2.5Ga and~2.7Ga)are distinguished in Longjiang area and Ulanhot area,western Songnen massif.The Precambrian tectonic thermal and crustal growth events in the western Songnen massif are similar to the ones in North China Craton and the ancient cratons in the world.
作者
吴新伟
张超
邵军
郭威
李林川
张广宇
刘宝山
宋万兵
WU XinWei;ZHANG Chao;SHAO Jun;Guo Wei;LI LinChuan;ZHANG GuangYu;LIU BaoShan;SONG WanBing(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Northeast Geological S&T Innovation Center of China Geological Survey,Shenyang 110034,China;Key Laboratory of Deep Mineral Resources Exploration and Evaluation,Department of Natural Resource of Liaoning Province,Shenyang 110034,China;School of Resources and Environmental Engineering of Shandong University of Technology,Zibo 255049,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第9期2811-2828,共18页
Acta Petrologica Sinica
基金
国家自然科学青年基金项目(41802238)
国家重点研发计划项目(2017YFC0601300-01)
中国地质调查局项目(DD20221687、DD20221632、DD20160047、DD20190156、12120113053900)联合资助.
