滇西古特提斯多岛洋的结构及其南北延伸

FRAMEWORK OF PALEOTETHYAN ARCHIPELAGO OCEAN OF WESTERN YUNNAN AND ITS ELONGATION TOWARDS NORTH AND SOUTH

在深化滇西古特提斯构造古地理格局研究基础上 ,提出了区分多岛洋与多岛海的时、空尺度标准。根据藏北羌塘、泰国北部与滇西古特提斯沉积地质学的比较研究 ,论证了滇西昌宁—孟连带北延连接冈玛错缝合带 ,南延与泰国北部隐蔽缝合带相接。泰国东北部著名的难河—程逸缝合带北延很可能潜伏于思茅盆地中新生代红层之下 ,因此古特提斯阶段并不存在稳定的“思茅地块”。泰国西北部湄萨良带存在洋盆硅质岩、海山碳酸盐岩和被动陆缘碎屑岩的构造混杂沉积组合 ,原属“泥盆系”的硅质岩中已发现早石炭世和晚三叠世卡尼期放射虫动物群 ,启示了古特提斯东段存在双子星座式主支洋盆的构造古地理格局。湄萨良带北延最可能与保山地块、腾冲地块之间的潞西三台山蛇绿混杂带相连。滇西北地区原属晚三叠世哈工组内侏罗纪放射虫化石的发现等 ,启示了青藏高原三江带在古。

Based on the deepening research of the Paleotethyan tectono paleogeographic framework in western Yunnan, we have suggested a scale of time and space standard concerning the differentiation between archiopelagic sea and archiopelagic ocean. According to the comparison study of the Paleotethyan sedimentary geology among northwestern Tibet, northern Thailand and western Yunnan, we demonstrate that the Changning Menglian belt of western Yunnan elongates towards north to the Gangmacuo suture zone of northwestern Tibet and towards south to the cryptic suture zone in northern Thailand respectively. The Nan Uttaradit suture zone of northeastern Thailand is probably elongated to north and hidden under the Mesozoic Cenozoic red beds of Simao basin. Of course, there is no evidence concerning a stable Simao block during the Paleotethyan stage. Tectono sedimentary mélanges consist of oceanic bedded cherts, seamount carbonates and passive margin clastics that are found in the Mae Sariang zone of northwestern Thailand; moreover, Early Carboniferous and Late Triassic (Carnian) radiolarian faunas are also discovered in previously so called 'Devonian' strata of this area. It indicates that the tectono paleogeographic framework of eastern Paleotetethys probably exists as the Gemini type archipelagic ocean with double main branches. Mae Sariang zone probably connects northward the Luxi ophiolitic mélange zone between Baoshan and Tengchong blocks in western Yunnan. The discovery of Jurassic radiolarian fauna in previously so called 'Late Triassic' Hagong Formation in northwestern Yunnan also inspires the variety and complexity of geological history in southeastern Asia during the transitional stage between Paleaotethys and Neotethys.