By Sergey M. Rodionov1, Alexander A. Obolenskiy2

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Yanliao 2 Metallogenic Belt of

Chemical-Sedimentary Fe-Mn

and Sedimentary-Exhalative Pb-Zn

(SEDEX) Deposits

(Belt YL-2) (Northern and Northeastern China)

This Mesoproterozoic metallogenic belt is hosted in the Jixian Group in platform sedimentary cover rocks on the Sino-Korea Craton. The belt occurs in the eastern Yanshan Mountain in the West Liaoning and Northeast Hebei Provinces, is 200 to 300 km long, over 50 km wide, and strikes in east-west. The belt is the continuation of the Yanliao Mesoproterozoic metallogenic belt. The deposits are mainly hosted in the Neoproterozoic Jixian Group with isotopic ages of 1400 to 1100 Ma. The host rocks for the deposits are variably-colored siltstone and silty shale and intercalated with limestone. The significant deposits are at Wafangzi and Gaobanhe.

Wafangzi Chemical-Sedimentary Fe-Mn Deposit

This deposit (Ye, Lianjun and others, 1994) consists of stratiform and lensoid masses. The thickness of a single layer is only 10 to 30 cm. The deposit comprises three layers that are 1 to 2 m thick on average. These three layers are hosted in pelitic rock the middle part of the Mesoproterozoic Tieling Formation of the Jixian Group in a northeast-striking anticlinorium. The deposit occurs on the southeastern limb of the anticlinorium. The ores are divided into three types: (1) sedimentary manganite and rhodochrosite with para-oolitic, banded, massive, and psephitic textures; and (2) contact metamorphic ores consisting of bixbite, braunite, manganoferrite, coarse-grained rhodochrosite, Ca-rhodochrosite, Mn-olivine, Mn-garnet, diopside, and sulphides; (3) oxidized ores consisting of massive, banded, and radiating psilomelane, pyrolusite, calcite, dolomite, and quartz. The sedimentary environment is interpreted as shallow marine or nearshore. To the west of the deposit are a group of smaller sedimentary Mn deposits. The deposit is large with reserves of 37.69 million tonnes grading 18-24% Mn.

Gaobanhe Sedimentary Exhalative Pb-Zn (SEDEX) Deposit

This deposit (Tu Guangzhi and others 1994) consists of nine stratiform deposits that occur in an east-west-trending belt that is 6 km long and 3 km wide. The host rocks are Mn shale and dolomite of late Proterozoic Gaoyuzhuang Formation. Ore minerals are mainly sphalerite, galena, and pyrite, and the ore varies from massive to banded. Framboidal, colloform and pelletoidal pyrite are common. The deposit occurs in the east-west-trending Yanliao basin on the Sino-Korea Craton. The deposit is medium size with an average grade of about 2% Zn and a lower concentration of Pb.

Origin and Tectonic Controls for

Yanliao 2 Metallogenic Belt

The belt is interpreted as forming in a shallow marine basin on the Sino-Korea Craton and is hosted in the Middle and Neoproterozoic Hebei-Liaoning sedimentary basin. The Mesoproterozoic part of the basin consists of: (1) sandy-muddy dolomite; (2) dolomite; (3) shale; (4) quartz sandstone, dolomite, and limestone, dolomitic limestone; (5) sandstone and siltstone; (6) muddy limestone. The Yanliao oceanic basin changed from shallow sea in the Jixianan period to an epicontinental sea in the Qinbaikou period (Wang Hongzhen, 1985). The Mn deposits of the Wafangzi type are interpreted as forming in a shallow oceanic basin.

REFERENCES: Wang Hongzhen, 1985.

Fanhe Metallogenic Belt of

Carbonate-Hosted Pb-Zn

(Mississippi Valley type) Deposits

(Belt FH) (Northeast China)

This Early to Middle Mesoproterozoic metallogenic belt is hosted in the small Fanhe Mesoproterozoic sedimentary basin (too small to show at 5 M scale) in part of the Sino-Korea platform sedimentary cover. The belt occurs in the eastern Liaoning Province, is 80 km long, over 30 km wide, and strikes north-northeast. The isotopic ages for the Fanhe Group range from 1600 to 1300 Ma. The host rocks for the deposits are siltstone and silty shale, dolomite and limestone. The significant deposit is at Chaihe.

Chaihe (Guanmenshan) Carbonate-Hosted Pb-Zn (Mississippi Valley type) Deposit

This deposit (Rui, Zongyao, 1994; Tu, Guangzhi, and others, 1994) consists of about 150 pod-like, stratiform, vein-type deposits. Host rocks are mainly banded dolomite of Early Mesoproterozoic Fanhe group. Ore minerals are mainly galena, sphalerite, pyrite, and others. that occur in masses, veinlets, and disseminations. The deposit is controlled by a northeast-striking fracture zone that is the secondary structure of major Yilan-Yiton fault zone. This fault zone occurs between the Fanhe basin and Tieling-Jingyu uplift. The deposit is medium-size with reserves of 147,800 tonnes Pb, 391,500 tonnes Zn, and an average grade of 3.90% Pb and 8.18% Zn.

Origin and Tectonic Controls for

Fanhe Metallogenic Belt

The belt is interpreted as forming in Fanhe Group that occurs in a small Mesoproterozoic aulacogen superposed on the Sino-Korean Craton. The Fanhe Group consists of: (1) quartz and feldspar sandstone (Dahongyu Formation) that is 570 m; thick (2) dolomite (Gaoyuzhuang Formation) that is 1190 m thick; and (3) shale, quartz sandstone, and dolomite (Yanzhuang Formation) that is about 2,800 m thick. The Pb-Zn deposits occur in the.upper part of dolomite horizons. The Fanhe Pb-Zn deposit may be transitional between Mississippi Valley and the SEDEX types (Rui Zonggyao, 1994).

REFERENCES: Tu Guangzhi and others, 1989, Rui Zonggyao, 1994.

Chungnam Metallogenic Belt of

Banded Iron Formation (BIF, Superior Fe) and

Metasomatic U(?) Deposits

(Belt CN) (South Korea)

This Late Paleoproterozoic and Early Mesoproterozoic metallogenic belt occurs in the Gyenggi granulite-paragneiss terrane in the Ogcheon Group (part of the South China Craton) that is intruded by the Jurassic Daebu Granite belt. Isotopic age of the metallogenic belt ranges from 1400 to 800 Ma. The Ogcheon Group consists of graphitic black schist, mica schist, quartz schist, and granite gneiss. The Daebu granite belt consists of biotite granite, granite porphyry, and quartz porphry. The major deposits are at Seosan, and Kongju.

Seosan Banded Iron Formation (BIF, Superior Fe) Deposit

This deposit (Kim, 1965) of zones or lenses in Precambrian quartz schist that is intruded by various probable Cretaceous igneous intrusives. The ore bodies are generally low grade hematite and magnetite and are interpreted as a dynamo-metamorphic deposit of sedimentary origin that was enriched in the northern area by thermal metamorphism following intrusion of granite gneiss. The ore minerals exhibit five textures: fine banded, medium banded, coarse banded, coarse spotted , and massive. In the southern area, hematite is dominent exhibits a well-developed banded structure, with alternating hematite and silica bands parallel to schistosity of the country rock. In the northern area, most of the ore minerals are coarse-grained spotted or massive with various ratios of hematite to magnetite. A ratio of 7:1 to 5:1 is dominant in medium banded type. The deposit averages 5 to 60 meters wide and 30 to 200 meters long. Assays reveals traces of TiO₂, S, and P. SiO₂ content is high, varies inversely with Fe. The deposit is medium-size with average grade of 31.42% Fe and a resource of 5,222,000 tonnes and reserve of 1,476,000 tonnes Fe.

Kongju Metamorphic Graphite and Metasomatic U Deposit

This deposit (Yun and Kim, 1959) is hosted in Proterozoic graphitic black shale in the Kongju Formation. Seven drill holes peneterate the deposit. The host rocks consists of Precambrian metasedimentary rock, mostly mica schist, and granite gneiss, and Jurassic intrusive rocks. Graphite deposit consists of recrystallized graphite, quartz, feldspar, muscovite, and biotite with minor zoisite, chlorite, zircon, pyrite, sphene, galena, uraninite, and V-oxides. Size of crystalline graphite flakes ranges from 0.5 mm to 1 mm mostly. Minimum size is 4 microns. Size of uraninite is 6 to14 microns. Average grade is 24.4% C, 0.03% U₃O₈, and 0.08% V₂O₈. Graphite formed in two stages: (1) carbonaceous material in arenaceous sedimentary rock recrystallized to crystalline graphite during regional metamorphism,; and (2) carbon dioxide from limestone that was converted to graphite during intrusion of younger granitoids. Uranite is interpreted as forming in a reducing environment from U that was absorbed in the carbonaceous material during circulation of U-bearing ore solution. V-oxide(?) replaced carbonaceous material during circulation of V-bearing solution. The graphite deposits are at Sohak-ri, Kaeryong-myon, Kongju-gun, Chungchong-namdo. The deposit is small with an average grade of 0.0385% U₃O₈ and reserves of 2,560,000 tonnes ore.

Origin and Tectonic Controls for

Chungnam Metallogenic Belt

The belt is hosted in middle Proterozoic Gyeonggi metamorphic complex and Ogcheon Group that consists of graphitic black schist, mica schist, quartz schist and granite gneiss. Graphite deposits occur in zones or lenses in quartz schist. Uranite interpreted as forming in a reducing environment from U that was absorbed in the carbonaceous material, during circulation of U-bearing ore solution.

REFERENCES: Kim, and Yun, 1959; Koo and others, 1977; Kim, 1965; Duk Hwan Hwang, this study.

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