阿拉善地块东南缘与鄂尔多斯盆地西缘中、上奥陶统浊流演化及其与内波相互作用研究

Under the situation of the researchment of deep-water deposits become one of the development of the petroleum geology, it is time for the study of evolution of turbidity currents under different tectonic environments and establish the corresponding sedimentary model using the latest research results about sedimentation fluid as the following resons: ① established the theory of turbidity current deposits based on outcrop observation; ② established submarine fan model based on the exploration and research of submarine; ③ the study of deposition mechanism and process around sedimentary fluid. The area located on the southeastern margin of Alxa block and western margin of Ordos basin is an ideal site for the study of turbidity currents evolution based on outcrop observation of turbidites which is different from dassic turbidites (with Bouma sequence). The reason is not only for the abundant turbidites with significant reworking by deep-water tractive currents in Middle and Upper Ordovician but also for tectonic position between Proto-Tethyan ocean and Paleo-Asian ocean. Here we forcus on turbidity current evolution and its interaction with internal waves depend on the special turbidites in study area and the study of internal-wave and internal-tide deposits in China, which is an advantage study area in deep-water deposits study in the world. This researchment will found to hold promise for advantage in the study of the interaction between turbudity current and short-period internal wave. And also have significance in several regional geological hot issues, such as the tectonic ownership of study area (the boundary of southeastern margin of Alxa block and western margin of Ordos basin) and the Paleozoic helian aulacogen.

浊流沉积研究在经历了以野外露头研究为主建立浊流沉积理论；以深海调查为主建立扇模式和以沉积流体为核心展开新一轮的理论探索后。在深水沉积已成为当今油气地质理论发展趋势之一的形势下，充分利用沉积流体的最新研究成果，展开浊流沉积的野外露头研究，积极探索不同大地构造环境下浊流的演化，并建立相应沉积模式的时机已渐趋成熟。阿拉善地块东南缘与鄂尔多斯盆地西缘处于始特提斯与古亚洲洋的连接部位,中、上奥陶统浊流沉积类型丰富，同时又明显受到深水牵引流的改造，已成为有别于经典浊积岩的浊流演化研究的理想场所。本项目以该地区中、上奥陶统"特殊"浊积岩为研究对象，结合中国在世界深水沉积研究的优势领域-内波、内潮汐沉积，及时开展浊流演化及其与内波相互作用研究，有望在浊流沉积理论方面走向世界的前沿。同时对该地区的大地构造归属（阿拉善地块东南缘与鄂尔多斯盆地西缘的界线问题）、古生代贺兰坳拉谷等区域地质热点问题均具有重要意义。

本项目以鄂尔多斯盆地西缘和阿拉善地块东南缘中、上奥陶统深水沉积为主要研究对象，采用沉积学与地球化学相结合的研究方法，对该地区广泛发育的浊流沉积、内波沉积和等深流沉积及其沉积环境进行了广泛的调查和详细的研究。同时根据研究工作的实际需要，对滇中地区底寒武统（筇竹寺组和沧浪铺组）、华北克拉通寒武系标准剖面（山东张夏剖面）也进行了调研。实测地质剖面4条，其中内蒙古桌子山地区石峡谷剖面进行了逐层测量；磨制和鉴定岩石薄片835张（其中鄂尔多斯盆地西缘519张），地球化学样品152件（其中鄂尔多斯盆地西缘117件），分别进行了主量、微量、碳氧同位素、亚铁分析、硫分析等测试。研究取得了4项创新型成果：1）在香山群徐家圈组发现短周期内波沉积；2）在克里摩里组发现了完整的等深流海进沉积序列；3）发现深水层流沉积；4）发现等深流水动力氧化现象。特别是层流沉积和水动力氧化现象的发现，将预示着早古生代夹在华北地块、扬子地块、哈萨克斯坦板块等之间的原特提斯洋可能为层化大洋，这种层化大洋则可能是介于元古代硫化氢大洋和现今大洋之间的一种大洋类型。因此，本项目的研究成果将对古海洋沉积学研究及地球演化研究具有重要意义。