Geology and geochemistry of the Sambo Pb-Zn deposit, Republic of Korea

Abstract

The Sambo Pb-Zn mine is located approximately 45 km south of Seoul within the Precambrian metamorphic belt of the southern Korean Peninsula. The Sambo Pb-Zn deposits are composed of fissure-filling quartz-barite veins within Proterozoic biotite schist which has been intruded by granite ahd granodiorite stocks. K-Ar dates of biotite and muscovite from the intrusions are 177 _ 4 and 164 _ 3 m.y., suggesting a Jurassic age for Pb-Zn-Ba mineralization. This age is in agreement with data for metallogenic epochs in Korea. Ba-rich Pb-Zn deposits are related to a Jurassic-Early Cretaceous epoch, whereas Ba-poor Pb-Zn deposits are generally related to Late Cretaceous-Tertiary igneous activity.Mineralization at Sambo consists of three distinct stages of quartz-barite veins (I, II, and III) which were separated in time by tectonic fracturing and brecciation events. Ore textures of stage II suggest rhythmic deposition. Five successive mineralization cycles of stage II, each with up to seven nearly monomineralic bands, are recognized. Fluid inclusion data suggest that each stage evolved from early high temperatures (near 300øC) to later lower temperatures (less than 200øC). Although the maximum temperature of stage III is slightly lower than the maximum temperature of stages I and II, we suggest that each stage represents a separate cooling mineralizing system that was interrupted by renewed tectonism.Sulfur isotope and fluid inclusion evidence indicates that galena, sphalerite, and barite were deposited at temperatures near 160 ø to 265øC from solutions with salinities ranging from 2 to 17 equivalent weight percent NaC1. Fluid inclusion evidence of boiling suggests pressures of less than 100 bars during portions of stage II mineralization. This pressure corresponds to depths at the time of mineralization of between 500 and 1,250 m.

Oxygen and sulfur isotopic compositions of quartz, barite and sulfide minerals from the Sambo Pb-Zn-barite ore deposits, South Korea.

“…This clas sification is different from that of So et al (1984) in mineral assemblage of each stage. Generally, quartz-bearing barite veins have Fe rich sphalerite, while Fe-poor sphalerite is ob served in the barite-rich quartz veins.…”

“…The geology of the Sambo mine area has been summarized by Park and Park (1980), So et al (1984) and Jwa (1989) as shown on the simplified geologic map (Fig. 1).…”

“…1). granodiorite in the northwestern part of the mine was dated as 163.6 ± 3.3 m.y (So et al, 1984). So et al concluded that the Pb-Zn mineralization was associated with the intrusion of those plutonic rocks.…”

“…Gangue minerals are quartz and small amounts of calcite, fluorite and rhodochrosite. So et al (1984) reported detailed vein mineralogy and divided the mineralization at Sambo into three distinct stages on the basis of ore texture, tectonic fracturing and brecciation events.…”

“…From 1983 to 1990, the mine produced 2200 metric tons/y of barite ores with 15-20 wt% Ba, 3000 metric t/y of lead ores with 15-20 wt% Pb, and 9000 metric t/y of zinc ores with 4-5 wt% Zn, respectively. Park and Park (1980) and Jwa (1989) have studied the geology and fluid inclu sion, but little is known about depositional condi tions of ore minerals (So et al, 1984). This paper presents the oxygen and sulfur isotope data for ore and gangue minerals including sulfides, sulfate and quartz in the Sambo deposits.…”