【作者】 陈永振；

【导师】 周立发；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2013， 博士

【摘要】 南祁连地区位于木里断裂-拉脊山南缘断裂以南,宗务隆山北缘断裂以北的地质区域,东南与西秦岭相连。西秦岭北带是指甘肃夏河县以东,陕西凤县以西,武山-天水以南,临潭-岷县-宕昌-凤县一线以北的地区。无论从早古生代构造单元划分的角度还是从现今构造单元划分的角度来看,南祁连地区与西秦岭北带分割于商丹古缝合带两侧,南祁连地区属于祁连加里东构造带的组成部分,而西秦岭北带则属于西秦岭华力西-印支构造带的组成部分。但是南祁连地区和西秦岭北带的石炭系、二叠系和下中三叠统皆为海相沉积,它们在这一时期是否为同一大地构造环境中的沉积产物,在地层层序及其结构、岩相特征、地球化学特征等诸多方面是否存在相关性是本文研究的主要内容。研究结果表明：志留纪末的晚加里东运动,使南祁连地区与中祁连-陇西地块、柴达木地块和阿拉善地块拼贴形成一个北部的统一大陆,在石炭纪-中三叠世阶段,南祁连地区为这一北部大陆的大陆边缘。中志留世至晚志留世末祁连洋的关闭,使西秦岭北带由扬子板块向北拼贴至华北板块,与南祁连地区形成了统一的北部大陆的大陆边缘。西秦岭北带南缘在石炭纪发育的一套重力流沉积以及晚石炭世合作-宕昌一带深水碳酸盐相沉积中零星出现的中性火山岩以及沉积物的分布特征说明石炭纪合作-宕昌一带的确存在—西宽东窄、西深东浅的海底峡谷。以此海槽为界,其中沉积的重力流沉积物中皆有南北两带成分,且其后西秦岭北带的沉积物特征明显与南部不同,说明西秦岭北带的沉积环境因该海槽的分隔作用与其南部有着巨大差异。而西秦岭北带与南祁连地区的石炭系-中三叠世的沉积构造特征、岩相特征、地球化学特征、沉积岩碎屑成分特征一致说明,这两个地区在这一时期的海相沉积体具有可比性。从大地构造背景分析来看,在石炭纪-中三叠世时期,西秦岭北带与南祁连地区共同形成了统一的北部大陆的大陆边缘。更多还原

【Abstract】 Southern Qilian area is located in the southern part of Qilian fold belt, the northern parts connect to the Middle Qilian block, southeast is linked together with the West Qinling. It is limited between Muli falt-the south margin of Lajishan falt and the north margin of Zongwulong mountain. The northern belt of West Qinling Mountains area is located in the east of Xiahe county in Gansu province, west of the Fengxian county in Shaanxi province, the noth side from the line of Wushan-Tianshui and the south side from the line of Lintan-Minxian-Dangchang-Fengxian county. No matter from which angle between the division of tectonic units both in the Early Paleozoic and today, South Qilian area and the northern belt of West Qinling Mountains area belonged to two separate tectonic units. They are separated by Shangdan ancient suture zone. South Qilian area is a part of Qilian Caledonian fold and fault zone while the norh zone of West Qinling area is a part of the West Qinling hercynian-indosinian fold and fault zone. However, the strata form Carboniferous to middle Triassic are all marine deposits. Whether they are the products of the same sedimentary tectonic environment, and the correlation of the stratigraphic sequence, lithofacies features and geochemical characteristics between both two areas are the main research contents.The research results show that the late Caledonian movement at the end of the Silurian, made the south Qilian area linked with middle Qilian-west Gansu block, the Qaidam massif and Alxa Block form a northern unified continent, and in the Carboniferous-Middle Triassic epoch, the south Qilian area should be a continental margin of the northern continent. In the Middle to the late Silurian, the closing of Qilian ocean made the north zone of the West Qinling collage from the Yangtze plate to the north to the North China plate, forming a continental margin of a unified northern continent with the south Qilian area.During the period of Carboniferous, the gravity flow deposits and the odd intermediate volcanic rock and sediments developed in deep water carbonate facies showed up in the southern margin of the northern belt of West Qinling Mountains. The combination of these sediments proved that there had been a submarine canyon west east wide-narrow and deep-shallow existing in Carboniferous in the area of Hezuo-Dangchang. Bounded by the trench, the components of the north and south belt could both be found in the gravity flow deposits. Meanwhile the sediments’ characters in the northern belt of West Qinling Mountains were quite different from the sediments in the south, indicating there were great differences between the sedimentary facies of the northern and southern belt. However, the same characters of sedimentary structures, lithofacies, geochemistry and debris components of Carboniferous-Middle Triassic in the northern belt of West Qinling Mountains and the southern region of Qilian declared that marine facies sediments of the two areas in the same period could be comparable. From tectonic background analysis, in the Carboniferous-Triassic period, the northern belt of West Qinling Mountains was connected to the south Qilian area, forming acontinental margin of a unified northern continent.更多还原