青森県深浦地方の新第三系 : とくにマンガン鉱床について

The district concerned is located in the green tuff region along the coast of Japan Sea, Northern Honshu. The stratigraphic sequence of the Neogene Tertiary intercalating the beds of manganese dioxide ore is therein, in descening order, shown as follows:
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The uppermost formation is of non-marine facies, while the remainders are of marine ones.
In the district, there appear two structural trends: one points to NS as is represented by the pre-vailing anticlinal axis of fold and fault with the same direction, and the other to NW-SE as is shown by the anticlinal axis of fold and fault revealing the similar trend.
The volcanic rocks are distributed inferably in a close relation to the geologic structure. Especially, the pyroxene andesites relating intimately to genesis of the ore deposits are located in the marginal place around the intersection between two different anticlinal fold-axes alluded to above.
In connection with the geology briefly mentioned above, the ore deposits are generally considered as follows:
1) Because of the tabular or bedding form and of being intercalated conformably in the strata, the deposits in question are infered to be of sedimentary origin.
2) . Basing on the fact that the ores are found deposited restrictively in the strata lying over the pyroxene andesites, it seems sure that the, manganese in the deposits might have been derived chiefly from the submarine hot spring during the postvolcanism of the pyroxene andesites and partly from weathering of the same volcanics after their eruptions.
3) That the formations including the ore deposits are of 'marine facies produced with mixing of fresh water suggests the facility for oxidation of the ore into manganese dioxide.
4) The ore deposits are used to occurring in the formations correlative to the Nishikurosawa and Onnagawa formations of the middlle Miocene.