海洋中磷的循环与沉积作用

磷在海洋中的循环与沉积主要是靠生物作用进行的。海洋表层水中的溶解磷几乎全部被海洋植物摄取，海洋植物及动物死亡后最终以生物碎屑的形式沉入海底，在其沉降和到达深层水的过程中大部分被分解、破坏，变成可溶组分又重新返回海水，使深层水中磷浓度提高。含磷浓度高的深层水被上升洋流带到表层后又被生物吸收，重复循环。当上升洋流抵达大陆边缘，特别是遇有陆缘坻存在时，磷等营养物质滞留，导致磷质生物大量繁衍，死亡后沉积，并经成岩作用，便形成大规模的工业磷块岩矿床

CIRCULATION AND PRECIPITATION OF PHOSPHORUS IN OCEANIC BASINS

Phosphorus, one of main organic elements, is circulating and precipitating in oceanic basins highly with the help of oceanic organisms.For example, oceanic microplants (algae, bacteria and the like) are able to absorb almost whole dissolved phosphrous from the upper shading zones of oceanic water bodies, as a result,the surficial oceanic waters seriously short of phosphorus. In addition, these oceanic plants, along with some oceanic animals, after their deaths and before sinking in the form of detritus down to the deep level, would be broken down to get soluble back into the oceanic waters, thereby increasing the phosphorus solubility of the deep waters. The detritus hard to be dissolved, however, will sink straightly onto the oceanic floor and become part of the bottom sediments.When the phosphorus rich deep oceanic waters are taken up by upwelling oceanic currents to the surficial waters,and the contained phosphorus is absorbed by the microorganisms once again, another cycle of phosphorus’ circulation and precipitation is about to start. On the way to continental margins, the upwelling currents happen to rush in a so called “luyuanchi” when they would unload their phosphorus and let it to be trapped in the seafloor pitfall with the help of microorganisms. A luyuanchi, an unique paleo geographic and structural unit, could have made much contribution to phosphorus’ being trapped because it had created an environment favourable exclusively for phosphorus to precipitate, in which slower current speed, lower pressure, higher temperature and larger CO 2 fugacity all play a key role in concentrating phosphorus a great deal and hence in accelerating the flourishing of phosphorus addicting organisms. These organisms die and then are buried on ocenic floors before they can form large scale phosphorite deposits of commercial importance due to further enrichment of phosphorus by post depositional diagenesis.