松廣鑛山의 地質鑛床

Geology and ore deposits of Songgwang mine

Songgwang lead zinc mine is located in about 12km to the north-east of Jeonju City. Geology of the mine and its visinity is consisted of Jeonju series belonged to so-called Okcheon system, Seodaesan tuff formation, Silla series, and the quartz porphyry intruded into these formations. Jeonju series comprising 3 formations; that is, of Sadaeri, Sindong, and Girinbong. Jeonju series is generally distributed in southern part of the area, striking NNW, and diping NE 30°, or NW 30°. It is deformed to form synclinorium and anticlinorium plunging to the north with low angle. In the northern part of the area. Jeonju series was cut by Sinpeongri-fault of NEE direction near Sinpeongri. In the north side of the fault, it is overturned and shows NEE or NWW strikes and NW 60° dips. At the west of Songgwangri, it is cut by 3 thrusts; the two are almost parallel each other, and the third one is manifested by the fact that the lower black shale zone thrusted over the upper limestone. Songgwangri thrust, so named, is a post-mineral faulty and its plane represents a premineral slip plane. Enrichment of ore took place along the bedding plane or fissure parallel to it, as seen adit No. 1 or No. 2 along the floor of the thrust, and along the sheared zone or the brecciated zone oblique to the plane near the thrust in crystalline limestone of Sindong formation as observed in the underground levels of inclined slop. Ore minerals are chiefly zincblende, galens, pyrrhotite, arsenopyrite, accompanied pyrite and chalcopyrite, and contain Au and Ag. In earlier stage of mineralization, the limestone was recrystalized, and sulphide menerals were enriched in the permiable zone said above by pyrometasomatism, and in later stage the limestone was affected chloritization and sericitization. However hydrothermal replacement was weak, so that enrichment did not took place. It seems that mineralizing materials came up through the premineral slip plan and injected, and replaced the limestone in permiable zone said above with sulphide ore minerals. Then Songgwangri thrust took place and the lower black shale zone thrusted upon crystalline limestone.