黔中地区震旦纪含磷岩系时空变化及沉积模式

黔中地区聚磷盆地是在南沱期沉积的基础上发展起来的,陡山沱早期海侵时期,福泉-瓮安-开阳-温泉一带为半封闭海湾,从东部上升的含磷酸盐洋流运移到此半封闭环境,产生了胶磷矿沉积,之后黔中古陆快速隆升,早期形成的胶磷矿处于滩相环境,受波浪作用改造,形成砂屑磷块岩矿床;开阳地区富磷矿形成与矿层顶板及其间的假整合面对应,磷矿层形成后受强烈的暴露淋滤影响。在黔中古陆的南东侧外陆棚区,含磷组分难以聚集,形成厚度薄、品位低的磷块岩矿床;在灯影组沉积期-早寒武世期间,贵州大部分处在广阔陆表浅海环境,仅在织金形成相对深水泻湖相沉积,含磷酸盐的上升洋流运移至其中形成低品位磷块岩矿床。通过黔中地区震旦纪典型磷矿床含磷岩系及顶、底板地层的相剖面及时空变化分析,建立了黔中地区磷矿沉积模式。 

Spatial and Temporal Variation and Mineralization Model of the Sinian Phosphorus-bearing Sequences in Central Guizhou Province

The phosphorus accumulation basin in central Guizhou province was developed on the basis of sedimentary basement of Nantuo Formation.During the transgression period of early Doushantuo Formation,the phosphate bearing upwelling from eastern deep ocean flooded into the semi-closed bays of central Guizhou in Fuquan,Weng'an,Kaiyang and Wenquan,where collophane synchronous was deposited.After that the central Guizhou old land uplifted rapidly and the original semi-closed bays transformed into highbeach.The previous cellophane layer was broken and leached by turbulent waves and ultimate formed sand-sized phosphorite ore bed.The disconformable contact between phosphorite deposits and overlying or underlying strata in Kaiyang indicated that the phosphorite ore beds suffered exposure and leaching.As the southeastern area of central Guizhou old land was outer continental shelf,the phosphorus was difficult to assemble in seawater and only thin and poor grade phosphorite ore bed was deposited in the area.During Dengying period to Early Cambrian,most areas of Guizhou turned into open shallow marine facies,but areas like Zhijin which was located in western of central Guizhou old land was relatively deep sea lagoon facies,the phosphate bearing upwelling flooded into these areas and formed low grade phosphorite ore bed.Based on the temporal and spatial variation analysis of sedimentary facies and the contact relation of layers in the Sinian phosphorus-bearing sequences,the authors proposed a mineralization model which explains the phosphogenesis event in central Guizhou.