滇西北中甸地区哈工组放射虫及其构造古地理意义  

RADIOLARIANS FROM HAGONG FORMATION IN ZHONGDIAN, NW YUNNAN,AND ITS TECTONO-PALEOGEOGRAPHIC IMPLICATIONS

作　　者：冯庆来[1] 张世涛[1] 葛孟春[1] 严城民 余华 段国玺 包俊跃 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]云南省地勘局区域地质调查大队,云南玉溪653100 [3]云南省地勘局第三地质大队,云南大理671000

出　　处：《地质科学》2002年第1期70-78,T003,T004,共11页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：原地质矿产部PANGEA项目 (95 0 1 1 0 5 )资助

摘　　要：位于甘孜—理塘构造带和金沙江构造带之间的德格—中甸微板块 ,可分为乡城晚三叠世岛弧带、义敦晚三叠世弧后盆地带和中咱地块等次级构造单位。滇西北中甸地区上三叠统哈工组包含大量沉积混杂岩块 ,与乡城、得荣泥砾混杂岩相连 ,形成晚三叠世沉积混杂岩带。哈工组沉积序列和沉积混杂岩沉积特征研究表明 ,中甸地区沉积混杂岩带为义敦晚三叠世弧后盆地形成过程中 ,由盆地边缘垮塌沉积形成 ,混杂岩块物源为近源下伏地层。沉积混杂岩块主要为晚古生代灰岩 ,但也有含中泥盆世、早石炭世和中二叠世放射虫化石的层状硅质岩 ,说明德格—中甸微板块晚古生代不是统一的碳酸盐台地 ,而是碳酸盐台地与深水断陷盆地并存的构造古地理格局。另外 ,哈工组三段还发现侏罗纪放射虫化石 。The Dege Zhongdian microplate, located between the Garze Litang and Jinshajiang Belts, was considered as a part of the Yangtze plate and a whole carbonate platform in Late Paleozoic, which could be tectonically divided into the Xiangcheng island arc, the Yidun back arc basin and the Zhongzan block in Late Triassic. Three members of the Upper Triassic Hagong Formation in Zhongdian, NW Yunnan, are as follows in ascending order: terrestrial conglomerate and sandstone, neritic siltstone and mudstone with a lot of chaotic blocks, and deep sea turbidites with interlayers of silicolites. The sedimentary mélange could be linked with the Upper Triassic mélange in West Sichuan. They were deposited in the Late Triassic Yidun back\|arc basin and all chaotic blocks came from the margin of the basin. Except the Late Paleozoic limestone blocks, there are some siliceous blocks from which the radiolarians in ages of Middle Devonian, Early Carboniferous and Middle Permian are also found in Zhongdian. The results indicate that the Dege Zhongdian microplate must have a complicated tectono geographic feature in Late Paleozoic, including shallow water carbonate platform and deep sea basin, instead of a simple carbonate platform. In addition, it was commonly accepted that the region east of Jinshajiang belt became continent after Triassic. However, the Jurassic radiolarians were discovered from the siliceous interlayers in the top part of the Hagong Formation in Zhongdian, which comprehends that there might be a marine basin during Jurassic in the studied area.

关 键 词：沉积混杂岩 放射虫 构造古地理 云南 晚三叠世 侏罗纪 德格-中句微板块 

分 类 号：Q915.811.3[天文地球—古生物学与地层学] P534.5[生物学—古生物学]