Abstract: After the montmorillonites saturated with KCl and experienced through compaction or heatings,feldsparizations would take place,bringing about the transformation of sodium-montmorillonites into iso-potassium feldspars and calcium-montmorillonites into plagio-clases.In the sedimentary rocks with 10μm clay,the iso-potassium feldspar is the product from the sodium-montmorillonites with high pressure in sedimentary system of trench-trough or graben,Therefore,the iso-potassium feldspar can be taken as the marks for the dynamic characters of downward-excavating sea water current in hydrothermal cyclic system.Based on existence of the iso-potassium feldspar,the ratio of the characteristic peak values of 3.71A,4.23A and 3.3A in the oriented X-ray deiffratogram(XRD)is about 1:1:3.8.Such a diffratogram texture may be fixed in a certain ratio and is probable to be the proecursor of graphic granites.