Studies on the Japanese Acid Earth. Part II : Physical properties of Japanese Acid Earth.

Abstract

This is a report of genetic studies on the Japanese Acid Earth from Imai, Niigata Prefecture. The geological map and shematic profile ofthe location where the present sample was taken are shown in Fig. I-1 and I-2. In the Fig. I-2,P shows the rock which the author estimated to be liparitic tuff. In present case, the Japanese Acid Earth seems to be divided into two series according to the process of weathering, one is P-H_1-G_1 and the other P-H_2-G_2. The data of total analysis of the Acid Earth are given in Table I-1. Each content of H_2O from G_1 to H_2 is greater than that of P, these values indicating that the weathering is in process towards hydration. The ratio of SiO_2 : Al_2O_3 in each horizon is shown in Table I-2,and the value of G_1 to H_2 is very smaller than that of P, and moreover, the valueof G_1 and G_2 is smaller than that of H_1 and H_2. The value of P reaches 17.15 but when author culculated the average of chemical consistuents of the 16 liparitic rocks which are cited in Rosenbush's "Elementeder Gesteinslehre", this value was found to be 9.31. Judging from this number and the results of microscopic examination, the parent rock is concluded as glassy liparite or liparitic tuff. Therefore, it seems that the rock P rich in silica, is changing into H_1 and H_2 through the process of desilicification. At the same time, H_1 and H_2 gradually turn into G_1 and G_2 as the result of weathering, and the formergroup is richer in silica. The 10% HCl soluble component after Gedroiz is shown in Tabbe I-3. From these data, it is found that SiO_2 and Al_2O_3 in G_1 to H_2 are much easily soluble but alkali earth and alkali are not so easily soluble, but especially not is MgO. The Japanese Acid Earth is known by its acid reaction. So the author furthermore inveseigated of ths earth, the value of Exchange Acidity, Hydrolytcc Acidity and PH. P and H_2 are not so acidic but G_1 and G_2 indicate very high acidity. These values agree with the content of exchangeable hydrogen of every horizen. But base exchang capacity of H_2 is very high and followed by G_2,but that of H_1 and G_1 is fairly low. These value correspond to the amount of 10% HCl soluble SiO_2. Then, the author investigated the clay minerals which constitute the Japanese Acid Earth. For this purpase, he studied the dehydration curves and the differential heating curves of each horizon of the Acid Earth. From the form of dehydration curves (Fig. II-1), he was able to point out that the clay mineral of G_1,G_2,H_1 and H_2 belongs to a kaolinite group, but the form of P does not show such characteristic a type. The differential heating curves of G_1 and H_1 are shown to be the halloysite type, but those of G_2 and H_2 are not clealy defined (Fig. II-2). Then, in order to know the crystalline forms of these constituent clay minerals of investigated earth, he used for this purpose, electron ultramicroscopic photograph and X-ray diffraction diagram. The former is given in Fig. II-3. Needles crystalline halloysite is shown in G_1 sample only, but none in other samples. The diagram of X-ray pattern of earth is given in Table II-2. This result accounts for that the constituent clay mineral of investigated earth belongs to halloysite type. From these investigtions, the author has concluded that the clay mineral of Japanese Acid Earth consists of hydrated halloysite (Endellite).