华北克拉通胶东莱州地区中太古代-新太古代早期TTG岩石的发现——锆石SHRIMP U-Pb定年

Discovery of Mesoarchean-early Neoarchean TTG Rocks in Laizhou Area in Eastern Shandong of North China Craton——SHRIMP U-Pb Zircon Dating

胶东是华北克拉通早前寒武纪变质基底重要分布区之一,已发现～2.9Ga,～2.7Ga和～2.5Ga三期TTG岩石,并确定新太古代晚期和古元古代晚期两期构造热事件。但是,有关胶东地区早前寒武纪变质基底的认识几乎都来自对莱阳以北地区(主要为栖霞地区)的研究。该文对莱州地区早前寒武纪变质基底8个岩石样品开展了SHRIMP U-Pb锆石定年,首次发现～2.9Ga岩石(条带状英云闪长岩和片麻状闪长质岩石),发现大量～2.7Ga英云闪长岩和奥长花岗岩。确定存在多期次构造热事件叠加改造,包括中太古代晚期-新太古代早中期构造热事件。研究表明,莱州地区与莱阳-栖霞地区具有类似的早前寒武纪地质过程,它们共同构成胶东太古宙变质基底。该文总结了胶东地区早前寒武纪变质基底形成演化历史。

Jiaodong is one of the important distribution area of early Precambrian metamorphic basement in North China Craton.~2.9 Ga,~2.7 Ga and^2.5 Ga TTG rocks have been found,and late Neoarchean and late Paleoproterozoic tectono-thermal events have been identified.However,all knowledge on the early Precambrian basement of eastern Shandong are from the study in the north of Laiyang area(mainly in Qixia area).SHRIMP U-Pb zircon dating on 8 samples from early Precambrian basement of Laizhou area have been carried out.~2.9 Ga rock(banded tonalite and gneissic dioritic rock)has been discovered for the first time,and^2.7 Ga tonalitic and trondhjemitic rocks have been found.Several tectono-thermal events have been identified,including late Mesoarchean and middle to early Neoarchean tectono-thermal events.It is indicated that Laizhou area is similar to Laiyang-Qixia area in early Precambrian processes.They form Archean basement in Jiaodong area together.The formation and evolution history of the early Precambrian basement in Jiaodong area has been summarized.