【摘要】 滇西古特提斯构造带某些玄武岩的Ｓｒ、Ｎｄ、Ｐｂ同位素资料显示存在富集放射成因Ｐｂ同位素的Ｄｕｐａｌ异常。五素玄武岩的：８７Ｓｒ／８６Ｓｒ＝０．７０６３，εＮｄ（Ｔ）＝５．４─６．５；铜厂街洋岛玄武岩的８７Ｓｒ／８６Ｓｒ＝０．７０３６─０．７０８３，εＮｄ（Ｔ）＝０．６５─６；双沟、德钦、铜厂街、勐连蛇绿岩玄武岩的８７Ｓｒ／８６Ｓｒ＝０．７０３８─０．７０７３，εＮｄ（Ｔ）＝８．２─１０．９．Ｓｒ、Ｎｄ同位素资料表明这些玄武岩来源于地幔源区，未受壳源物质的混杂，而个别８７Ｓｒ／８６Ｓｒ异常高值与其形成之后的海水蚀变作用有关，并不影响其Ｎｄ、Ｐｂ同位素组成。Ｐｂ同位素组成表明它们具有异常高的放射成因Ｐｂ，显示其地幔源区具Ｄｕｐａｌ异常特征，而Ｄｕｐａｌ异常源区的形成与古代洋壳俯冲带入深部地幔的壳源物质参加到地幔重新循环有关。更多还原

【Abstract】 The Sr, Nd and Pb isotopic components of some basalts in Western Yunnan Paleo─Tethyan belts shown the existence of Dupal anomaly which enriched in radiogeneic lead isotope. The Wusu basalts which lacates at western Mojiang County and erupted in the sea floor with earliest eruption at early Carboniferous in back─are extensional settings, have87Sr/86Sr= 0.7036 - 0.7083, εNd(T)= 0.65-6.0.The Shuanggou, Deqin, Tongchuangjia and Monglian ophiolitic basalts, which all developed in Paleo─Tethyan oceans between late Devonian and late Permian, have 87Sr / 86Sr = 0.7038-0.7073, and εNd(T)= 8.2-10.9. Sr and Nd isotopic data show that these basalts were all derived from mantle sources with very less or no crustal contamination. Seldom high 87Sr / 86Sr ratios of basalts were affected by the alternation of oceanic water befor its emplacement, thus, it would not affect the Nd and Pb isotopic components. In Pb vs. Pb diagram, almost all these basalts are plotted above Northern Hemisphere Referenee Line (NHRL), showing the enrichment of cadiogeneic lead isotope. This inferred that these basalts were derived from mantle sources with Dupal anomaly. The further analysis indicated that the Dupal anomaly of mantle sources was related to the crustal material which was subducted into deep mantle by ancient oceanic crustal subduction and then taken part in the mantle recycling. Based on Paleomagnatic research, the Western Yunnan Paleo─Tethyan was located at Southem Hemisphere before Permian, this inferred that all these analysed basalts were formed at Southern Hemisphere. It suggested that their Dupal anomaly were related to the Gondwana land.更多还原