The Features And Potash Index Systerm Of The World Marine Solid Potash Deposits

Potassium is one of the three nutritive elements that control agricultural production. China is a large agricultural country with an annual production capacity of 3 million tons of potash fertilizerm while it needs 7 million tons of potash fertilizer import which accounts for 70% of all the potash fertilizer consumption in 2009. So it is necessary for china to do some research about the conditions of potash-forming in some large scale sedimentary basins to make important breakthroughs in finding potash deposits. The paper compares basic potash-forming features of 25 typical potash deposits all around the world. From the macroscopic perspective, it determines the climate conditions, sedimentary environment, material source, basin structure,basin scale and potash-forming age, etc. While from the microscopic perspective, it determines the precipitation stage, ore-bearing structural positon, potash-forming favorable structural position, etc. In addition, it preliminarily sets up the quantitative and semi-quantitative index system of potash deposits, and it analyzes the potash-forming conditions. By comparison, the conclusions are as follows:(1) It shows that almost all global potash deposits formed in the early period of continent plate convergence and divergence, especially the potash resource is the largest in the early period of divergence. It is found that the potash deposits developed during Late Sinian-Palaeozoic era are mostly present in some huge-large epicontinental basin in some large cratons. And the ones developed during Mesozoic are mainly present in some microcontinents and epicontinental basins in Tethyan realm while the ones developed during Late Mesozoic- Cenozoic era are mainly present in continental rift basin.When it comes to Quaternary period, lots of continental Salt Lake potash deposits appear in the hinterland of some major continental blocks.(2)The comparative statistics of the tectonic environment of global potash deposites show that potash resource extent is large in relative activity area. the stable tectonic region was favorable for potash concentration in a quasi-stable region, and quasi-stable was favorable for salt concentration and potash formation in a local stable tectonic region, therefore, which should pay attention to relative tectonic active region type basins in the potash process.(3)It is found that large-scale potash resources most likely came into being at Calcite Sea Period(high Ca2+ low). by comparing the component evolution of seawater and the age distribution of potash resources.(4)It is found that the layers of most potash deposits, particularly large-super large potash deposits are thick, and the evaporates distribute widely and their layers are thick, with few sedimentary rhythm layers, which mostly grew as three kinds of salt group, and the potash mostly located at the middle salt group, also the thickness of the potash layers were positively correlated with the distribution range of the underlying rock and the sediment thickness.(5)Synthetical tectonics, paleoclimate, paleogeography, geochemistry and other factors, we thepreferred that Yangtze plate have the potential of potash-forming in structure and climate aspects, during the period of Late Sinian-Early Cambrian,Early-Middle Cambrian and middle-Lower Triassic.