岩石鉱物鉱床学会誌

化石イルメナイト砂鉱床の形成および保存を規定する造構要素

宮城県蒲沢鉱山周辺の地質鉱床

斎藤洋彦

1972 年 67 巻 7 号 p. 209-217
発行日: 1972/07/05
公開日: 2008/08/07

DOIhttps://doi.org/10.2465/ganko1941.67.209

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The factors which influence the depositional environment of fossil iron-sand placer deposits are the climate, tectonic regime, general palaeogeographic environments, peculiarities of the source area, and the hydro-dynamic conditions in the front basin. It is obvious that the deposition of fossil iron-sand placer deposit is controlled more or less by these factors.
The author (Saitoh, 1972) has reported on the general geology and tectonic movement near Kabasawa Mine area. The warping movement of Okubushi-Line which is the main tectonic line in this area controlled the differentiation and development of the Pliocene sedimentary basin and the deposition of Pliocene Sendai Group, especially Kabasawa sandstone and conglomerate member intercalated ilmenite placer deposit.
It is the purpose of this paper to point out the fact that Kabasawa ilmenite placer deposit has been built up and kept in a very good condition being controlled by the warping movement of Okubushi-Line.

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室戸岬はんれい岩体の岩石学的研究

矢島敏彦

1972 年 67 巻 7 号 p. 218-241
発行日: 1972/07/05
公開日: 2008/08/07

DOIhttps://doi.org/10.2465/ganko1941.67.218

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The Murotomisaki differentiated gabbroic complex locates at the extreme point of the Cape Murotomisaki, Shikoku Island. This complex intruded into the Murotohanto Group of Eocene in age. The zonal arrangement of which complex shows the indication of the fractional crystallization with gravitational sinking. Principal rock types of the complex are as follows: chilled marginal dolerite, picrite gabbro, fine-grained hyperathene bearing olivine augite gabbro, medium-grained hyperathene bearing olivine augite gabbro, augite gabbro pegmatite and ferrogabbro. The pegmatitic rocks of the latest stage intruded as small veins. Anygrain of pigeonite or inverted pigeonite is not found, whereas a small amount of hypersthene is observable as internal precipitates. Iron concentration in olivine and in augite is conspicuous at the upper part of the complex. Ilmenite is the predominant opaque minerals through the course of fractionation and magnetite appears at the latest stage. Fractional crystallization of OLIVINE THOLEIITE to intermediate iron concentration under low vapour pressure and low oxygen partial pressure is studied on these bases.

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鉱物共生関係のステレオ投影

坂野昇平

1972 年 67 巻 7 号 p. 242-245
発行日: 1972/07/05
公開日: 2008/08/07

DOIhttps://doi.org/10.2465/ganko1941.67.242

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多成分系の共生関係の投影において,過剰成分を表わす点と,共生する鉱物とを結んだ直線を,過剰成分を中心とした球に投影し,球面で共生関係を表現できる。この方法を用いると,投影の立体角に制限がないため, Thompsonの投影法のように無限遠に点が投影されることはない。3相共存の領域は球面3角で表わされる。

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