滇西昌宁—孟连带“中—上泥盆统”和“二叠系拉巴组”中的石炭系南段组及其成因机制探讨  

SUCCESSIONS OF THE MISSISSIPPIAN NANDUAN FORMATION INTHE“MIDDLE-UPPER DEVONIAN”AND THE“PERMIAN LABA FORMATION” OF THE CHANGNING-MENGLIAN BELT,WESTERN YUNNAN,CHINA AND ITS GEOLOGICAL SIGNIFICANCE

作　　者：郑建彬[1] 金小赤[1] 宗普[1] 闫振 黄浩 ZHENG Jian Bin;JIN Xiao Chi;ZONG Pu;YAN Zhen;HUANG Hao(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《地层学杂志》2024年第1期87-99,共13页Journal of Stratigraphy

基　　金：国家自然科学基金(92155202、42002118、42172040)资助。

摘　　要：滇西昌宁—孟连带是探索古特提斯地质演化的热点地区之一。识别和梳理带内不同岩石地层单元所包含的内容,追索其分布情况,是深入、准确地了解这一地区地质演化的一个重要前提。石炭系密西西比亚系南段组分布于昌宁—孟连带东带,是一套厚度大、成熟度较高的被动陆缘浅海沉积。笔者近期在昌宁—孟连带西带的“中—上泥盆统”和“二叠系拉巴组”中识别出了一套碎屑岩地层,其化石面貌及岩石学和锆石年代学特征反映其为南段组沉积。它们与不同时代的硅质岩、碎屑岩、灰岩等混杂分布。前期的研究显示南段组为冈瓦纳大陆被动大陆边缘的“原位沉积”,而西带不同时代的硅质岩、碎屑岩、灰岩和玄武岩等则为源于古特提斯的“外来岩片”。在古特提斯闭合过程中,这些“外来岩片”就位于冈瓦纳大陆被动陆缘的“原位沉积”(南段组)之上。构造挤压和褶皱变形,以及后期的剥蚀,使得在“原位沉积”(南段组)与“外来岩片”的接触部位出现南段组与时代不同、沉积构造背景迥异的岩片穿插、混杂分布的现象。The Changning-Menglian Belt in western Yunnan,China,is an area of great significance to decipher the geological history of the Paleo-Tethys.Identifying the components of various stratigraphic units and tracing their distribution pattern are fundamental for deep understanding of the geological evolution of the belt.The Mississippian Nanduan Formation,which has a large thickness and high maturity,distributed in the east zone of the Changning-Menglian Belt,was deposited in a shallow marine environment in a passive continental margin.Recently,we identified clastic rock sequences from the“Middle-Upper Devonian”and“Permian Laba Formation”in the west zone of the Changning-Menglian Belt.Fossil assemblages,lithological features,and zircon age spectra indicate that they are outcrops of the Nanduan Formation.The newly found sequences of the Nanduan Formation in the west zone exist randomly,normally with fault contact and with siliceous,clastic,and limestone slices of varied ages.Previous studies show that the Nanduan Formation represents“autochthonous sediments”in a passive continental margin of Gondwana-derived Baoshan-Shan block.The siliceous,clastic rock slices,limestones,and basalts of different ages in the west zone are allochthons of Paleo-Tethyan origin.During the closing period of the Paleo-Tethys,these allochthonous slices were emplaced on to the“autochthonous sediments”of the Baoshan-Shan block.Meanwhile,folding,faulting and other deformations,and also later erosion resulted in the pattern of mixed distribution of the“autochthonous” Nanduan Formation and the allochthonous slices of different ages,and varied tectono-sedimentary settings in the west zone of the Changning-Menglian Belt.

关 键 词：昌宁—孟连带 石炭系 南段组 “外来岩片” 古特提斯 

分 类 号：P534.45[天文地球—古生物学与地层学]