摘要
柴北缘前寒武纪基底岩系发育、岩浆活动频繁,对它们进行年代学研究与对比是探索区域构造过程与成因联系的有效手段.对达肯大坂岩群西段条带状混合片麻岩、黑云斜长片麻岩、二云斜长石英片岩及侵入其中的片麻状石英闪长岩进行了物质组成及变质-变形特征研究.LA-ICP-MS锆石U-Pb同位素年代学测试均获得了达肯大坂岩群约460Ma和约430Ma两组峰值年龄信息.结合区域构造演化,认为约460Ma的次峰值年龄是柴北缘早古生代大陆深俯冲过程中构造-岩浆事件的地质记录;而约430Ma变质作用时代与片麻状石英闪长岩的结晶年龄(429.0±4.1Ma)基本一致,结合片麻状石英闪长岩地球化学及达肯大坂岩群锆石稀土元素特征,认为该期变质作用为同期岩浆事件导致的构造-热事件的响应.片麻状石英闪长岩具有明显亏损Nb-Ta、Zr-Hf等高场强元素,富集Pb,指示了与板块俯冲作用相关的造山岩浆作用特征.该研究可为进一步揭示欧龙布鲁克地块西段早古生代构造-热事件的性质提供重要信息.
It is a valid approach to explore the tectonic evolution and origin by comparative chronological research of the rocks in the northern margin of Qaidam basin characterized by outcropped basement rocks and frequent magmatic activities.Dakendaban Rock Group（DRG）is one of the dominant crystal basement rocks of Oulongbuluke block.A study was carried out on material composition,deformation and metamorphism of the banded migmatitic gneiss,biotite plagioclase gneiss,two-mica plagioclase quartz schist sampled from the DRG,and the gneissic quartz diorite that intruded the DRG.The zircons from DRG samples yield nearly unanimous two peak age of about 460 Ma and peak age of about 430 Ma by LA-ICP-MS zircon U-Pb isotopic analyses.Combined with the regional tectonic processes,we maintain that the age of about 460 Ma is the geological response to the tectono-magmatism caused by ultradeep continental subduction in the North Qaidam.The metamorphic age about 430 Ma is consistent with the crystallization age（429.0±4.1Ma）of the gneissic quartz diorite.Combined the chronolgical data with geochronological analyses on the gneissic quartz diorite,and the zircon REE data from DRG samples,it proves that the metamorphism of about 430 Ma is closely related to the homochronous tectono-thermal event.The obvious depletion of HFSE,including Nb,Ta,Zr,Hf,and the Pb enrichment demonstrate that the characteristics of the gneissic quartz diorite are related to the plate subduction which formed the active continental margin.This study provides important information for further revealingthe tectonic properties and the evolution of the tectono-thermal event at Early Paleozoic in western Oulongbuluke bolck.
出处
《地球科学（中国地质大学学报）》
EI
CSCD
北大核心
2016年第4期586-604,共19页
Earth Science-Journal of China University of Geosciences
基金
中国地质调查局项目(No.1212011121193)
国家青年自然科学基金项目(No.41002063)
