By Sergey M. Rodionov1, Alexander A. Obolenskiy2

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tarix	24.06.2016
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Gyeongnam Metallogenic Belt of

Polymetallic Pb-Zn  Cu (Ag, Au) Vein

and Stockwork, Polymetallic (Pb, Zn±Cu,

Ba, Ag, Au) Volcanic-Hosted Metasomatite,

Fe Skarn, W-Mo-Be Greisen, Stockwork,

and Quartz Vein, Porphyry Mo (±W, Sn, Bi),

Cu-Ag Vein, Au in Shear Zone, and

Quartz Vein Deposits

(Belt GN) (South Korea)

This metallogenic belt is hosted in Yeongnam Metamorphic Complex (part of Sino-Korean Craton, Yeongnam granulite-paragneiss terrane), Gyeongsang Supergroup, and the Late Cretaceous Bulgugsa Granite. The age range of the belt is interpreted as Cenomanian through Campanian (96 to 75 Ma). Yeongnam metamorphic complex consists of leucogranite gneiss, hornblende plagioclase gneiss, biotite gneiss and schist of Wonnam Formation. The Gyeongsang Supergroup consists of shale and sandstone of the Hadong and Sindong Groups and volcanic rock of Yucheon Group that are intruded by Late Cretaceous Bulgugsa biotite granite, granodiorite, anorthosite, porphyry, and felsic and quartz porphyry dikes. The major deposits are at Cheolma, Gwymyeong, Mulkum, Kuryong, Ulsan, Goseong, Tongyoung, and Haman-Gunbuk.

Cheolma Au in Shear Zone and

Quartz Vein Deposit

This deposit (Hwang and others, 1987) consists of gold bearing quartz veins following fault shear zone, joint and fractures. Host rocks are Cretaceous andesitic rocks, lapilli tuffs, rhyolitic tuffs and felsophyre intruded by Cretaceous granodiorite, hornblende granite, biotite granite and aplite. Veins trend N20-40°W, dip 70-85°NE, and range in length and width 65-130 m and 1.0-1.5 m, respectively. Ore minerals are chalcopyrite, galena, sphalerite, pyrite, pyrrhotite and magnetite. The deposit is small with resources of 98,700 tonnes grading 0.5-1.3 g/tAu, 2-30 g/t Ag, and 0.5-3.01% Cu.

Gwymyeong Polymetallic

(Pb, Zn±Cu, Ba, Ag, Au)

Volcanic-Hosted Metasomatite

Deposit

This deposit (Hwang and others, 1989) is hosted by Cretaceous tuffaceous rock and Late Cretaceous andesite and diorite. Deposit occurs along fissures and shear zones in andesite and diorite. The width, length, and depth of veins are 0.3-1 m, 60-120 m, and 90-200 m, respectively. Ore minerals are chalcopyrite, galena, and sphalerite. The deposit is small with reserves of 6,080 tonnes ore grading 6.8% Pb, 9.2%Zn, 1.3% Cu, 1.1 g/t Au and 94.83g /t Ag.

Kuryong Polymetallic (Pb, Zn±Cu, Ba, Ag, Au)

Volcanic-Hosted Metasomatite Mine

This mine (Park, 1963; Kim and Oh, 1966) is hosted in a Cretaceous granite porphyry that intrudes widespread limestone of unknown age. Associated with the granite porphyry is a succession of intrusive andesite, agglomerate, pyroxene andesite, masanite, quartz-feldspar porphyry, and altered andesite. The intrusive andesite is partly covered by the agglomerate that forms an extrusive phase. The pyroxene andesite forms a bedded flow. The deposit is mainly sulfide veins and propylitic, hydrothermal alteration zones. Quartz monzonite intrudes both the andesite and the altered andesitic. Quartz-feldspar porphyry ocurs only in drill cores. The altered zone occurs in both andesite and agglomerate. The alteration is contemporaneous with, or post-dates quartz monzonite intrusion. Propylitically-altered rocks are green-grey, weather to light grey, and contain a fine-grained pyrite in disseminations. Chlorite, epidote, sericite, kaoline, calcite, quartz, and pyrite are extensively developed in the propylitic zone. Degree of alteration and pyrite content increase with proximity to veins. The deposit is small with resources of 413,280 tonnes grading 41.6% Fe,0.11% S, 0.04% P.

Mulkum Polymetallic (Pb, Zn±Cu, Ba, Ag, Au)

Volcanic-Hosted Metasomatite Mine

This mine is (Hwang and Kim, 1962) hosted in a Cretaceous feldspar porphyry that was intruded by an extensive Late Cretaceous biotite granite. The deposit consists of a magnetite metasomatite that occurs in fissure fillings. The ore minerals are magnetite, pyrite, chalcopyrite, galena, and sphalerite. The average width of veins ranges from 1 to 6 m, and the average length ranges from 44 to 250 m. In The average depth ranges from 70 to 150 m. The deposit is small with reserves of 1,741,875 tonnes ore. Average grade is 60% Fe,13.61% SiO₂, 0.12% S, 0.26% P, and 0.006% TiO₂.

Ulsan Fe Skarn Mine

This mine (Hwang, 1963) is hosted in limestone and serpentine of unknown age, Cretaceous slate and hornfels, and Cretaceous biotite granite. The Fe skarn occurs along the bedding limestone, or on the contact zone between limestone and serpentinite. The ore minerals are magnetite, chalcopyrite, sphalerite, galena, pyrrhotite, and arsenopyrite. Drilling reveals several deposits occur that have a lenticular shape that vary from170 to 180 m long, 140 m wide, and 80 m deep. The deposit is medium size with reserves of 1,708,400 tonnes grading 43% Fe and 0.02% Pb.

Goseong Cu-Ag Vein Mine

This mine (Park and others 1988) is hosted in Cretaceous greenish grey shale and sandstone of Jindong Formation, rhyolite tuff of Yucheon group, and that are intruded by late Cretaceous granodiorite. Deposit occurs along fissures and a fault-shear zone. The ore minerals consist of arsenopyrite, pyrite, sphalerite, chalcopyrite and galena. The mine is small with production of 6,900 tonnes from 1929 to 1964 grading 2.6-10.0% Cu, 1.2-10 g/t Au and 65-300 g/t Ag.

Tongyoung Cu-Ag Vein Mine

This mine (Park and others 1988) is hosted in Cretaceous andesite and andesitic tuff breccia of Yucheon group that are intruded by a Late Cretaceous quartz porphyry and diabase. The veins occur along fissures and shear zones in andesite, andesite tuff breccia, and quartz porphyry. The ore minerals are chalcopyrite, pyrite, galena, sphalerite, electrum, and argentite. The deposit is small with production of 5,000 tonnes grading 0.3-5.5 g/t Au,15-366 g/t Ag, 0.2-1.2% Cu.

Haman-Gunpuk Polymetallic (Pb, Zn±Cu, Ba, Ag, Au)

Volcanic-Hosted Metasomatite Deposit

This deposit (Kim and Kim, 1977) is hosted in light-gray chert of the Cretaceous Jindong Formation. The deposit consists of fissure-filling hydrothermal veins composed of Cu sulfide, specularite, and tourmaline. Sixteen veins crop out at the surface. Drilling reveals that the C and M veins are economic. The C vein is0.1 to 1.2 m wide, 130 m long, and 120 m deep, and has reserves of 34,920 tonnes grading 0.89% Cu. The M vein is 0.5 to 3.3 m wide, 160 m long, and 75 m deep, and has reserves of 77,992 tonnes grading 0.83% Cu. The deposit is medium size with reserves of 112,912 tonnes grading 0.86% Cu.

Origin and Tectonic Controls for Gyeongnam Metallogenic Belt

The belt is interpreted as forming during generation of granitoids during the Late Cretaceous to Early Tertiary Bulgugsa orogeny. The deposits occur along the fissures and shear zones and formed during intrusion of Bulgugsa granite (biotite granite, granodiorite and quartz-porphyry).

REFERENCES: Hwang and Kim, 1962; Park, 1963; Hwang, 1963; Kim and Kim, 1977; Park and others, 1988; Duk Hwan Hwang, this study.

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