滇西北金沙江带蛇绿混杂岩的形成时代及大地构造意义

ON THE TIME AND TECTONIC SIGNIFICANCE OF OPHIOLITIC MELANGE IN JINSHA RIVER BELT, NORTHWEST YUNNAN

本文报导了滇西北德钦县拱卡、拖顶等地晚古生代放射虫、、非有孔虫类化石新资料。提出当前用古生物法确定蛇绿岩套形成时代及蛇绿混杂岩定位时代应注意的问题。并根据化石资料，将金沙江蛇绿岩套的形成时代厘定为二叠纪，蛇绿混杂岩的就位时代厘定为早、中三叠世，据此将金沙江古特提斯构造演化分为裂谷阶段、洋盆阶段和闭合阶段。其中，金沙江洋盆阶段较短暂，蛇绿岩不具有隔离冈瓦纳及华夏两大古生物地理区系的作用，金沙江缝合带不能构成古特提斯域的主缝合带．

The authors report the new material of Late Paleozoic radiolarians, fusulinids, and non-fusulinids foraminiferas collected from Gongka, and Tuoding, Deqin county, northwest Yunnan. They point out the age of ophiolite suite by paleontological method and the emplacement age of ophiolitic melange. According to the fossils identified, the ophiolite suite is judged to be of Permian period and the ophiolitic melange was emplaced during EarlyMiddle Triassic. Hence, the tectonic evolution of the Paleotethys in the Jinsha river consists of three stages--the rift, the oceanic basin and the closing. As the oceanic basin stage in the Jinsha river was relatively short, the ophiolite should not serve as a barrier separating the Gondwana from the Cathaysian province. Consequently, the Jinsha river suture zone could not form the main suture zone in the Paleotethys.