扬子板块西缘新元古代蛇绿岩研究及其构造意义

According to single grain U-Pb dating of zircon and comprehensive studies of trace.element and Nd, Sr, O isotopes, the crystalline ages(936~853Ma) of the Shimian, Yanbian and.Luding gabbros in western margin of Yangtze block are first obtained. They are all formed at the.island arc setting. Based on the field correlation, and trace element and isotopic characteristics, it.is first suggested that the Shimian ophiolite was existed and was derived from intensive depleted.mantle source. Confirmation of the Shimian ophilite gives the most important evidences for the.subduction of oceanic plate of Jinning period in western margin of Yangtze plate and the position.of subduction belt. In accordance with field occurrence of the Lengshuiqing body, its trace.element and isotopic characteristics and in comparison with basalts of Yanbian Group, it is.obviously suggested that the Lengshuiqing body is not belonged to the range of ophiolite. This.project has very important significance for the existence Jinning orogeny around the Yangtze old.land.

扬子板块西缘盐边、石棉等蛇绿岩是扬子周边环状继续分布的新元古代蛇绿岩带的重要组成部分。本课题拟通过精细的同位素定年和系统的微量元素、稀土元素与同位素的示踪研究，准确厘定蛇绿岩套的形成时代，查明蛇绿岩浆起源与演化、壳--幔作用及其形成的构造环境和板块构造意义，为深入完整地研究扬子周边环状新元古代造山带演化史作出贡献。..