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    黔东北地区大塘坡组早期含锰沉积充填、岩相古地理与锰矿的关系

    The lithofaces, Mn-bearing sedimentary filling and palaeogeographic pattern of Early Datangpo Stage and implied for manganese in the northeastern Guizhou Province

    • 摘要: 黔东北地区是中国南华纪“大塘坡式”锰矿重要富集区,而岩相古地理是沉积型锰矿最重要的控矿因素。笔者根据松桃—江口地区南华系各组岩性及碎屑锆石年龄特征对清水江组、两界河组、铁丝坳组及大塘坡组进行细致的地层划分,在建立了本区南华纪大塘坡早期沉积充填序列的同时,将本区沉积盆地划分为4个II级盆地、12个III级盆地以及11个次级(IV)聚锰盆地。在不同盆地内的大塘坡一段中识别出14种岩相类型,划分出2类沉积系、10类主要的岩相古地理单元,进而编绘了本区南华纪大塘坡早期岩相古地理图。提出在大陆边缘裂谷盆地的背景下,研究区南华纪大塘坡早期沉积环境应属大陆边缘障壁海岸体系,属于典型的“大塘坡式”锰矿,与障壁后侧迅速沉降的深水局限盆地密切相关。

       

      Abstract: The Cryogenian (Nanhua) Period "Datangpo type" manganese deposits in northeastern Guizhou Province constitute the most important manganese resource base of China, and the lithofacies-paleogeographical environment is the most important orecontrol factor. Based on analyzing the lithology and age histogram of detrital zircon U-Pb ages of Qingshuijiang Formation, Liangjiehe Formation, Tiesi'ao Formation and Datangpo Formation, the authors present the stratigraphic division of Nanhuan System. Totally, there are four level II basins, twelve level III basins and eleven Mn-bearing basins according to distinct sedimentary filling patterns in northeastern Guizhou Province. It is suggested that there are nine types of palaeogeographic units in early Datangpo Age based on identifying fourteen types of lithofaces in 1st member of Datangpo Formation. Furthermore, the authors compiled the lithofacies paleogeographic map of Early Datangpo Age of Cryogenian (Nanhua) Period in northeastern Guizhou Province. In conclusion, under the background of continental margin rifting, the authors hold that the sedimentary environment of early Datangpo Age in the study area belonged to the barrier coastal system of continental margin, and the typical "Datangpo type" manganese deposit was closely related to the deep-water limited basin with rapid subsiding behind the barrier.

       

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