Chlorine in sedimentary rocks

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Concentrations of total, soluble and insoluble Cl were determined for various sedimentary rocks from differing localities and ages with a distillation method examined by the authors. Rock samples were investigated with an X-ray diffractometer and a microscope. The followings were proved: (1) Tertiary tuffaceous sandstones have considerable amounts of ins. Cl, while non tuffaceous sandstones have little. Ins. Cl of these rocks is contained mostly in glassy tuffaceous material and not in clays and crystals such as quartz or feldspar. Ins. Cl content of the Tertiary sandstones from the same locality varies according to the proportion of glassy material, clay minerals and crystals. (2) Sedimentary rocks of Permian age show very low concentrations of ins. Cl without regard to rock types. This means that ins. Cl has been leached out during weathering, diagenesis or recrystallization. (3) Ins. Cl content of clays is nearly zero, Cl being leached out when rocks alter to clays. (4) There are two types of tuffs. One retaines glassy material and has a considerable amount of ins. Cl. The other has altered to clays, contains no glassy material and reveals almost no ins. Cl.