中文摘要：

详细的地球化学解析表明,乌木龙—铜厂街地区出露的蛇绿混杂岩主要包括方辉橄榄岩、纯橄榄岩和碱性玄武岩。其中,方辉橄榄岩和纯橄榄岩具有极低的CaO含量（〈0.1%）、稀土总量（〈5×10^-6）和（La/Yb）N（0.96～1.14）值,（Ce/Yb）N为1.04～1.37,为轻稀土弱亏损型。本区碱性玄武岩具有高TiO2（2.57%～3.33%）、高K2O（2.29%～5.52%）的显著特征,（La/Yb）N为15.42～19.81,（Ce/Yb）N为12.48～14.76,为轻稀土强烈富集型;岩石Ti/V、Th/Ta、Th/Yb、Ti/Yb、Ta/Yb与来自亏损地幔的MORB以及与俯冲有关的岛弧火山岩明显不同,而主要显示为OIB型火山岩的微量元素地球化学特征,乃是典型的大洋板块内部岩浆作用的产物。该区洋岛型火山岩的厘定,表明昌宁—孟连古洋盆在石炭—二叠纪期间曾经历过一个由初始洋盆到成熟洋盆的完整发育演化过程。

英文摘要：

Ophiolite mélange from the Wumulong-Tongchangjie area,Changning-Menglian tectonic zone mainly consists of ultrabasic and basaltic rocks.The ultrabasic rocks are mainly composed of harzburgite and dunite.They exhibit distinctive geochemical characteristics of extremely low CaO （〈0.1%）,low rare earth element content （〈5×10^-6）,（La/Yb）N=0.96-1.14 and （Ce/Yb）N=1.04-1.37,showing the depletion of light rare earth elements.The basaltic rocks are alkaline and have high TiO2 （2.57%-3.33%） and K2O （2.29%-5.52%） content,as well as high （La/Yb）N=15.42～19.81 and （Ce/Yb）N=12.48-14.76,which show strong enrichment in light rare earth elements.The Ti/V,Th/Ta,Th/Yb,Ti/Yb and Ta/Yb of the alkaline basalt are much similar to that of the typical oceanic island basalt （OIB）;while are obviously different from that of the basalts originated from depleted mantle and/or generated by oceanic crust subduction.Therefore,the alkaline basalts in the studied area belong to typical oceanic island basalt （OIB） which was generated by magmatism within oceanic plate.It implies that the Changning-Menglian ancient ocean basin had undergone a whole evolutionary process from initial limited ocean basin to a mature ancient ocean basin.