摘要
对原划为新太古代古元古代康定杂岩的雅江桥片麻状奥长花岗岩、花滩奥长花岗岩和磨盘山花岗岩的地球化学分析表明,其具有低Mg#、Na2O>K2O,轻重稀土元素强烈分异,无或略具微弱的负Eu异常,低YbN、Cr、Ni、V、Nb、Ta、Ti,高Ba,Sr变化较大,与TTG类似。雅江桥奥长花岗岩的SHRI MP锆石U-Pb年龄测定结果为778±11Ma。初步认为本次工作所选的康定杂岩为形成于新元古代的TTG花岗岩。结合TTG的形成环境和前人研究成果,认为扬子地台西缘新元古代花岗岩是板块俯冲环境体制下玄武质洋壳部分熔融的产物。
Geochemical data indicate that Yajiangqiao trondhjemite, Huatan trondhjemite and Mopanshan granite, considered as component parts of Kangding complex formed in Late Archean or Palaeoproterozoic, are similar to TTG in such aspects as low Mg#, Na2O〉K2O, strong fractionationed REE, no or slightly negative Eu anomaly, low YbN, Cr, Ni, V, Nb, Ta, Ti, high Ba, and changeable Sr. SHRIMP zircon dating suggests that Yajiangqiao trondhjemite was emplaced in 778 ± 11 Ma. The results of the study show that Kangding complex is composed of Neoproterozoic granites bearing characteristics of TTG. The formation environments of TTG together with the results of previous studies imply that Neoproterozoic granites were formed by melted basaltic ocean crust under the condition of plate subduction along the western margin of Yangtze block.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2006年第4期273-281,共9页
Acta Petrologica et Mineralogica
基金
中国地质调查局地质调查项目(200313000061)
关键词
扬子西缘
康定杂岩
TTG
新元古代
板块俯冲环境
western margin of Yangtze block
Kangding complex
TTG
Neoproterozoic
plate subduction
