云南云县漫湾蛇绿混杂岩岩石特征及地质意义

THE LITHOLOGIC CHARACTERS AND GEOLOGICAL SIGNIFICANCE OF MANWAN OPHYOLITE MELAN GE IN YUNXIAN COUNTY,YUNNAN

通过云南云县地区1∶5万漫湾镇幅区域地质调查,从前人划分的上二叠统邦沙组(P_(3)b)分布区分解出来的一套中深变质岩系,为一套洋底玄武岩与洋内弧泥岩-碎屑岩的沉积组合,并称其为漫湾蛇绿混杂岩。该混杂岩中的火山岩,总体表现出洋中脊-准洋中脊拉斑玄武岩特点,在已变质的火山岩(角闪变粒岩)中获单颗粒锆石U-Pb谐和年龄值为295.6±0.92 Ma,表明漫湾蛇绿混杂岩形成于晚古生代。应为澜沧江洋盆闭合后的残留物,证实了澜沧江洋的存在。

According to the 1∶50000 regional geological survey of Manwan sheet in Yunxian county,Yunnan,the middle-hypogene metamorphic rock series resolved from original Upper P Bangsha Formation(P_(3)b)distribution area are the sedimentary assemblage of submarine basalt and oceanic inner arc mudstone-clastic rock called Manwan phiolite mélange.The volcanic rock of it generally shows the feature of mid-oceanic ridge or para mid-oceanic ridge tholeiite.The U-Pb Concordia age 295.6±0.92Ma of single zircon grain in metamorphic volcanic rock(amphibole granulitite)shows Manwan phiolite mélange is formed in Late Paleozoic,must be the relics after Lancangjiang ocean basin close,which confirms the viewpoint of Lancangjiang ocean.