鄂西陡山沱村期岩相古地理与含磷岩系沉积规律

PHOSPHORIC ROCK SERIES IN THE EDIACARAN DOUSHANTUOCUN AGE(SINIAN PERIOD)IN WESTERN HUBEI

湖北西部震旦纪陡山沱村期沉积地层分布广泛,上扬子地层区陡山沱组则是沉积型磷矿的重要产出层位,其含磷岩系组合明显受古地理环境控制。为查明该期岩相古地理格局,划分岩相古地理单元,研究磷矿形成条件和沉积规律,寻找更多磷矿资源,通过调查研究认为,鄂西上扬子区陡山沱组为华南海盆地北部的碳酸盐台地,可将其进一步划分为局限台地、开阔台地,台缘浅滩和潮坪通道。其中潮坪通道是含磷岩系聚集的最佳沉积相单元,通道两端与浅海盆地相通,通道内藻类繁盛,海水具有适度的波浪和潮汐作用,不仅有充足的陆源磷质供给,还有适宜于磷质沉淀的弱动荡水动力条件,有利于藻类对磷质的捕获粘结,也有利于磷酸盐颗粒化和颗粒的簸选,聚集与沉积。

The Ediacaran Doushantuo Formation is widely distributed in western Hubei province, and it is an important deposit of sedimentary phosphorite. The distribution of phosphoric rock series is controlled by palaeogeographic factors. In order to understand the lithofacies and paleographic control on phosphorite distributionto guide the exploration of phosphorite resources, we carried out a systematic investigation of the Doushantuo Formation in western Hubei Province. Our investigation shows that the Doushantuo Formation in western Hubei Province was deposited on a carbonate platform in the northern part of the South China craton. This carbonate platform can be divided into restricted platform, open platform, platform margin shoal, and tidal inlet facies. The tidal inlet facies is an optimal sedimentary environment for the accumulation of phosphoric rock series. Tidal inlets are connected with tidal flat and shallow platform facies. The inlet facies is characterized by abundant algal fossils and moderate wave and tidal activities. The supply of terrigenous phosphate was abundant and weakly turbulent hydrodynamic conditions were optimal for phosphorite deposition in the tidal inlet facies, where phosphatic sediments were winnowed and accumulated.