南盘江盆地中部西林断隆南翼中-下三叠统沉积学特征及其大地构造意义  

Sedimentary characteristics of the Early-Middle Triassic on the south flank of the the Xilin faulted block in the Nanpanjiang basin and its tectonic implications

作　　者：夏文静 闫全人 向忠金[3] 夏磊 江文 卫巍 李晓剑 周斌 XIA WenJing;YAN QuanRen;XIANG ZhongJin;XIA Lei;JIANG Wen;WEI Wei;LI XiaoJian;ZHOU Bin(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Institut des Sciences de la Terre d＇ Orleans,UMR 7327-CNRS/ Universitd d＇ Orleans,Orleans 45100,France;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]Institut des Sciences de la Terre d' Orleans, UMR 7327-CNRS/Universite d' Orleans, Orleans 45100 [3]中国地质科学院地质研究所,北京100037 [4]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石学报》2018年第7期2119-2139,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40472119、40872147);中国地质调查局项目(12120113067500、DD20160201-07);中国科学院大学博士研究生国际合作培养计划(UCAS[2015]37)联合资助

摘　　要：印支造山带对华南地质演化具有重要影响,南盘江盆地作为华南与印支造山带相关的最大的盆地,其构造演化过程备受关注,然而对于盆地由伸展到挤压的构造转换时限还存在争议。西林县位于南盘江盆地的中部,古生界和中-下三叠统出露良好,是进行沉积大地构造学研究的理想地区。为进一步明确南盘江盆地的构造演化过程,本文选取南盘江盆地中部西林县一带中-下三叠统进行了详细的沉积相分布和演化、古水流以及碎屑组成分析。结果表明,空间上,下三叠统自下而上自北向南依次出露:(1)泥岩、泥灰岩、砂屑灰岩和凝灰岩构成的潮坪-泻湖相沉积;(2)砾岩、含砾砂岩、细砂岩和粉砂岩构成的块体搬运沉积(MTD,Mass-transport deposit)与浊积扇相沉积互层;(3)中粗砂岩、粉砂岩、泥岩组成的浊积扇相沉积,构成向上水体急剧加深的沉积序列。中三叠统为一套浊积扇相沉积,由粗砂岩、细砂岩、粉砂岩和泥岩组成。古水流和碎屑组成分析结果显示,西林县一带下三叠统碎屑物主要来自北侧西林-隆林一带的碳酸盐岩台地,而中三叠统碎屑除来自北侧相邻碳酸盐岩台地外,还可能来自江南造山带、康滇古陆、云开地块和峨眉山玄武岩。沉积相的垂向变化记录了西林一带由古生代孤立碳酸盐岩台地向三叠纪半深海浊积岩盆地的演化过程,而早三叠世MTD是盆地张开过程中的直接沉积记录,以上地质事实暗示了南盘江盆地在早三叠世受控于区域伸展体制,西林一带的古生代孤立碳酸盐岩台地则是伸展过程中形成的断隆。盆地内的基性岩墙侵位(258~248Ma)以及西林一带早三叠世晶屑沉凝灰岩的锆石U-Pb年代学分析结果(249.4±1.2Ma)表明南盘江盆地在晚二叠世至早三叠世处于伸展构造背景之下,中三叠统为半深海浊积岩沉积则表明这一伸展过程至少持续至中三叠世。由于在时间上�The Indosinian orogeny plays an important role in the tectonic evolution of the South China block（ SCB）. As the biggest basin associated with the Indosinian orogeny on the southern margin of the SCB,the Nanpanjiang basin draws great attention in the geological community. Although many advances have been achieved,the time of the tectonic regime transition from extension to compression of the Nanpanjiang basin remains in dispute. In the central Nanpanjiang basin,the Paleozoic and Triassic strata are well outcropped around the Xilin faulted block,which provides an ideal studying object on revealing the basin evolution. In order to reveal the tectonic evolution of the Nanpanjiang basin,we have conducted a detailed sedimentary faces analysis,paleo-current measurement and frame-work clast statistics in the south flank of the Xilin faulted block. Our detailed field investigations show that the Lower Triassic on the south flank of the Xilin faulted block is composed of three subsequences which outcrop one by one in a southward younger order：（ 1） Tidal flat and lagoon deposits consist of mudstone,marlstone and calcarenite with tuff layers;（ 2） Mass-transport deposits（ MTD）alternated with turbidite fan deposits include conglomerate,pebbly sandstone,fine sandstone and siltstone; and（ 3） Turbidite fans deposits include medium-coarse sandstone,siltstone and mudstone. The Middle Triassic consists of a sequence of coarse sandstone,fine sandstone,siltstone and mudstone which is interpreted to be a turbidite deposition. The facies＇ evolution indicates a deepening sediment environment during the Early to Middle Triassic. The paleocurrent and detrital composition analysis indicate that the detritus of the Lower Triassic in the Xilin area were mainly sourced from the Xilin fault block,while the Middle Triassic deposits in the basin were from composed provenances including the Jiangnan orogenic belt,the Kangdian massif,the Yunkai massif,the Emeishan basalt and the faulted blocks. The sediment facies＇ and pro

关 键 词：西林断隆 南盘江盆地 中-下三叠统 块体搬运沉积 

分 类 号：P588.2[天文地球—岩石学] P597.3[天文地球—地质学]