南越鉱山の地質と鉱床の形成

The Geology and Vein Formation of the Nan-etsu Mine, Niigata Prefecture

SASAKI Den-ichi

廣島大學地學研究報告

Geological report of the Hiroshima University

The Nan-etsu Mine is situated about 12 km west of Muika-machi in the southern part of Niigata Prefecture.
The prevailing rocks in the environs of the mine are composed of a part of the Palaeozoic formations including clayslate, sandstone, chert and pyroclastic basic rocks, as well as of an older intrusive, i.e. hornblende-gabbro, intruding the former.
Both the Palaeozoic formation and hornblende-gabbro are converted to hornfels by intrusion of stocks of the younger biotite granite named Daikura granite and Kuromata granite.
Dyke rocks of porphyrite, quartz-porphyry and dacite distributing in the district are assumed to have been derived from the source similar to that of the younger intrusive.
The principal ore deposits are classifiable into a sort of hypo- or mesothermal fissure-filling veins, developing along the faults with ENE trend and fissures accompanied.
The related ores consist mainly of sphalerite, galena, chalcopyrite, pyrrhotite, pyrite and arseno-pyrite, associated with small amount of magnetite, cubanite, tetrahedrite and marcasite.
In many deposits such as Daikura, Mikagura, Hinata, Arayama, Hinokigura, Matagoro and Kōgai distributing widely around the stocks of the Daikura and Kuromata granites, the principal veins are found running along the dykes, especially of dacite or quartz-porphyry, pointing to their formation during the latest stage of younger igneous activity.

jpn

廣島大學理學部地學教室

[ISSN] 0073-2303

[NCID] AN00213676