哀牢山硅质岩特征及其意义

CHARACTERISTICS AND SIGNIFICANCE OF SILICOLITES IN AILAOSHAN AREA

“三江”地区哀牢山两类硅质岩的岩性组合、放射虫生态组合、稀土元素（ＲＥＥ）和硅同位素（δ３０Ｓｉ）特征表明，哀牢山晚泥盆世（Ｄ３）硅质岩属浊流成因，沉积于深海环境，证明扬子地台西缘在晚泥盆世（Ｄ３）时已裂开了一个深海槽；早石炭世（Ｃ１）硅质岩属哀牢山蛇绿岩的组成单元，形成于半深海环境，暗示哀牢山蛇绿岩代表的是一个相对封闭的小洋盆；海水深度、氧逸度条件、陆源物质及火山物质是影响哀牢山硅质岩稀土组成和硅同位素组成的因素。

Characteristics of lithology,paleoecology of radiolarian assemblages,rare earth elements (REE) and silicon isotopes (δ30Si) of two categories of siliceous rocks in Ailaoshan,“Shanjiang” area show as follows:The siliceous rocks of Late Devonian Epoch (D3) result from turbidity current,formed in the deep sea environment,and prove that a deep sea channel split open in the western margin of Yangtze platform in D3.The siliceous rocks of Early Carboniferous Epoch(C1)belong to the top unit of Ailaoshan ophiolites,formed in the bathyal milieu environment,and indicate that the ocean represented by Ailaoshan ophiolites is a relative closer small ocean basin.In addition,the data of these siliceous rocks still show that the influence factors of the REE composition and silicon isotopes of siliceous rocks in Ailaoshan area are the depth of seawater,condition of oxygen fugacity,terrigenous materials and volcanic activity.