Wall Rock Alteration of the Mikawa Mine, Niigata Prefecture

SUDO Toshio, NAGASAWA Keinosuke, IWAO Shuichi, OMORI Eiko

doi:10.11456/shigenchishitsu1951.3.87

The general features of lateral changes of propylitized andesite caused by a vein-forming agency was studied by recording the properties of several rock specimens collected at intervals of 5-10m. along a cross-cut tunnel, from the vein toward its outlet. The wall rock at more than 60m. distance from the vein has been unaffected by the vein-forming agency and is characterized by the development of chlorite and albite or by the lack of pyrite. The rock at less than 60m. distance from the vein has been affected by hydrothermal vein-forming solution. Chloritization and sericitization are particularly intense near the vein; this fact is revealed on the D.T.A. curves of the rock specimens collected at less than 20m. from the vein. Away from the vein, silicification is remarkably intense in place. Pyritization appears to be uniform all over the region and small amounts of adularia and carbonates are often found. The degree of staining by "Safranine Y" seen on the thin slices is proportional to the quantities of chlorite and sericite. The abrasion pH of the rock specimens in water is estimated sensitively by the intensity of fluorescence seen by adding "Fluorescein" to the water suspension. The intensity is strong near the vein and weak in the silicified part.

Wall Rock Alteration of the Mikawa Mine, Niigata Prefecture

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