岩手県和賀仙人鉱山の熱水性苦灰岩に伴う蛇紋石類について

今井 直哉, 大塚 良平, 本多 朔郎, 磯田 信人, 鈴木 滋

doi:10.2465/ganko1941.71.339

Serpentines associated with hydrothermal dolomite-rock at the Waka Sen-nin mine, Iwate Prefecture, have been examined by means of optical, X-ray diffraction, electronoptical, chemical, thermal and infrared absorption methods. As a result, it was confirmed that the serpentines may be classified into the following three varieties on the basis of the mode of occurrence, external appearance and the characterization of polymorphs and polytypes of the constituent serpentine minerals.<br> 1) Clayey serpentine with greenish-white colour, occurring as a pocket in partly dolomitized limestone; the material consists almost entirely of antigorite (superlattice parameters: a_??_43Å and rarely a_??_38Å) with a negligible amount of clino-chrysotile. 2) Fibrous serpentine with milky-white colour and silky lustre (so-called mountain leather), occurring in open cavities of hydrothermal dolomite-rock; the material consists predominantly of clino-chrysotile with a negligible amount of antigorite. 3) Massive serpentine with milkywhite colour, filling small open cavities or fractures in hydrothermal dolomite-rock; the material is a mixture of antigorite, and, clino- and ortho-chrysotiles.<br> These serpentines are considered to have been formed by the reaction of “impure calcite-marble” rich in SiO₂, A1₂O₃, etc. with ascending magnesium-bearing hot water. The hydrothermal magnesium-metasomatism which involves the formation of the present serpentines, the alteration of clinopyroxene skarn, and the hydrothermal dolomitization of limestone wallrock must be regarded as representing earlier“barren stage” in the course of the Mid-Miocene iron-copper mineralization that formed the major ores.

岩手県和賀仙人鉱山の熱水性苦灰岩に伴う蛇紋石類について

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岩手県和賀仙人鉱山の熱水性苦灰岩に伴う蛇紋石類について

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収録刊行物

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書き出し

問題の指摘

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