【作者】 张旗； 赵大升； 周德进； 黄忠祥； 韩松；

【Author】 Zhang Qi Zhao Dasheng Zhou Dejin (Institute of Geology,Chinese Academia of Science) Huang Zhongxiang Hansong (Institute of High Energy Nuclear Physics,Chinese Academia of Science)

【机构】 中国科学院地质研究所； 中国科学院高能物理研究所；

【摘要】 三江地区蛇绿岩分为新特提斯和古特提斯两个时期．新特提斯蛇绿岩以丁青为代表,具玻安岩特征,产于洋内岛弧的弧前环境,古特提斯蛇绿岩是 MORB 型,除了昌宁-孟连带之外,都具有弧后盆地的特征,表明亏损地幔源区受到了来自深部的富集地幔的影响．古特提斯玄武岩大多具 DUPAL异常,推测可以用冈瓦纳大陆下岩石圈分层的模式来解释．更多还原

【Abstract】 The ophiolites in the Sanjiang region can be classified into Neo-Tethyan and paleo- Tethyan ophiolites according to their age.The D(?)ngq(?)n ophiolite is the representative of the Neo-Tethyan ophiolites,Extending westwards,it connects with the Bangongco- Dongqiao ophiolite in northern Tibet.The D(?)ngq(?)n ophiolite,rich in $i and refractory ele- ments,and poor in high field strength elements(such as Ti,Zr,Y,and HREE),is similar to boninites in the islands of the westere Pacific Ocean,it may be formed in a fore-arc tec- tonic environment within the oceanic basin. The Paleo-Tethyan ophiolites are wideky distributed over the Sanjiang area.Geochemi cally,most of the Paleo-Tethyan ophiolites have similarities.Their basalts and diabases, similar to MORB,some of which are LREE-depleted,and others are slightly enriched and equivalent to N-MORB and E-MORB,respectively.Our researches show that most of the Paleo-Tethyan ophiolites,for example,the Yunshu-Litang ophiolite the Jinshajiang ophio- lite,and the Ailaoshan ophiolite were formed in the back-arc basin environments,except the Changning-Menglian ophiolite belt. Accordingly,it could be suggested that the depleted mantle sources had been influ- enced by fertile lower mantle.Most of Paleo-Tethyan basalts show Dupal anomality ac- cording to Pb isotopic data,which could be explained by the detachment of lithosphere be- neath Gondwanaland.更多还原