摘要
本文对云南省墨江县风别山霏细斑岩进行了锆石U-Pb年代学、岩石地球化学分析。LA-ICP-MS锆石U-Pb测年显示,风别山霏细斑岩年龄为266.1±1.5Ma,形成于中二叠世晚期。岩石地球化学显示,风别山霏细斑岩SiO_2含量为75.04%～81.88%,全碱(Na_2O+K_2O)含量为7.07%～9.52%;岩石富集轻稀土,负铕异常明显(δEu:0.04～0.08),相对富集Th、U,相对贫化Sr、Ta、Cr、Au。通过图解显示风别山霏细斑岩形成于碰撞期后板内构造环境,说明哀牢山构造带的古特提斯支洋或弧后盆地在中二叠世晚期266.1±1.5Ma可能已经闭合。
Objectives： The Ailaoshan tectonic belt is situated at the contact site of Tethys—Himalaya tectonic region and coastal Pacific tectonic region.At present,it is still controversial that whether Jinshajiang—Ailaoshan tectonic belt exists paleotethys ramose ocean basin or not in late Paleozoic era.In regard to this dispute,we focus on the study of petrogeochemistry and zircon U-Pb chronology of the Fengbieshan felsophyre in Yunnan to evaluate geological evolution in late Paleozoic era in southern section of Ailaoshan tectonic belt.Methods： Factitious heavy fraction was conducted to select zircons from the fresh sample of PM3005Z and well-crystallized,crackless,and transparent zircons were selected under the microscope,then photos of zircons were taken under reflected light and transmission light and CL image.The U-Pb isotope analysis was carried out at the laser probe of LA-ICP-MS Elan6100DRC in isotope geochemistry national key laboratory of Guangzhou Geochemical Institute.The analysis of major element compositions was completed with fluorescent spectrometer（ XRE） of Rigaku RIX 2000.The analysis of trace element compositions was performed with inductively coupled plasma source mass spectrometer（ LA-ICP-MS） of Perkin-Elmer Sciex ELAN 6000.Results： LA-ICP-MS zircon U-Pb dating results show that the Fengbieshan granodiorite formed in the Late Permian（ 263.6 ±2.4 Ma）.The Fengbieshan granodiorite is characterized by SiO2 62.10%～63.09%,alkali（ Na2O＋K2O） 6.28%～7.21%,and Na2O〉K2O.Moreover,it is enriched in LREE and Sc,Hf,and depleted in Sr,Zr,Th,U,with negative Eu anomalies（ δEu： 0.84～1.32）.Conclusions： According to the analysis data,we consider that the Fengbieshan granodiorite formed in the tectonic environment of island arc—continent or continental—arc collision,indicating that the branch of PaleoTethys Ocean or arc basin in Ailaoshan tectonic belt may have been closed in the Late Permian（ 263.6 ± 2.4 Ma）.
作者
孙崇波
李忠权
陈晓东
谢万洪
王道永
SUN Chongbo;LI Zhongquan;CHEN Xiaodong;XIE Wanhong;WANG Daoyong(Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation of Ministry of Land and Resources（Chengdu University of Technology）,State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation（Chengdu University of Technology）,Chengda,610059;Hydro-Engineering Party of Sichuan Metallurgical Geology and Exploration Bureau,Chengdu,611730)
出处
《地质论评》
CAS
CSCD
北大核心
2018年第5期1251-1262,共12页
Geological Review
基金
中国地质调查局项目"西南三江成矿带南段基础地质调查"(编号:1212010880406
1212011120582)的成果~~
