By Sergey M. Rodionov1, Alexander A. Obolenskiy2

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Darvi Metallogenic Belt of

Sedimentary Bauxite and

Sedimentary Fe-V Occurrences

(Belt DR) (Mongolia)

This Mesoproterozoic metallogenic belt is related to sedimentary layers in the Baydrag cratonal terrane in the Govi-Altai region. The main sedimentary bauxite deposit is at Alag uul. The Alaguul diaspore deposit is hosted in Riphean sedimentary rocks in the Darvi fragment of the Baydrag terrane.

Alag Uul Sedimentary Bauxite Deposit

This deposit (Pinus and others, 1984) is hosted in intercalated chloritite, amphibolite, graphite-bearing metaclastic rock and is closely spatially related to sedimentary Fe deposits (Zaitsev and others, 1984). The Riphean diaspore bauxite occurs in a zone up to 10 km long and 5 km wide. The belt is interpreted as forming during bauxite sedimentation in a Riphean sedimentary basin that overlapped the Baydrag cratonal terrane and subsequent regional metamorphism of sedimentary bauxite. The average grades are 49% Al₂O₃, 36% of Fe₂O₃, 2% SiO₂, 4% TiO₂. Probable reserves are 100,000 tonnes bauxite.

Origin and Tectonic Controls for

Darvi Metallogenic Belt

The belt is interpreted as forming during bauxite sedimentation in Lower to Middle Riphean sedimentary basin along a passive continental margin.

REFERENCES: Pinus and others, 1984; Zaitsev and others, 1984; Tomurtogoo and others, 1999.

Tseel Metallogenic Belt of

Muscovite Pegmatite and

Banded Iron Formation (BIF) Deposits

(Belt Tse) (Mongolia)

This metallogenic belt is hosted in the Tseel metamorphic terrane. The major deposits are in the Bodonch district (muscovite pegmatite), and Ikh Ganga district (BIF). Sokolov and Zaitsev (1990) name this belt as the Altai belt of muscovite and REE-muscovite pegmatite. We interpret that the REE pegmatite deposits formed in the younger Permian Turgen metallogenic belt. Kovalenko and others (1990) report that potential exists for stratiform scheelite deposits in Precambrian metamorphic schist of the Tseel metamorphic block.

Bodonch Muscovite Pegmatite District

This deposit (Kleiner and others, 1977) consists of eight mica bearing pegmatite bodies that occur in Lower and Middle Devonian metasedimentary rocks that are metamorphosed to garnet-biotite and biotite gneiss and intercalated with two-mica and garnet-two mica schists that are intruded by small, late Paleozoic granite plutons. Muscovite is abundant metamorphic mineral in schist. Conformable pegmatite veins range up to 1.5 km long and 2-5 m thick. Muscovite crystals in pegmatite veins are mainly small, but locally range up to 25 cm. Pegmatite minerals are quartz, muscovite, and microcline, and rare beryl, tourmaline, apatite and garnet. A Pb-Pb zircon isochron age for related aplite is 780 Ma. Deposit is located in the large Bulgan pegmatite zone of the southern slope of the Mongolian Altai. The deposit was mined from 1960 to 1970 and is exhausted.The deposit is small and grades up to 170 kg/m3 muscovite.

Ikh Ganga Banded Iron Formation Occurrence

This occurrence (Baikova and others, 1987) occurs in the eastern part of the belt in a Precambrian metamorphic complex in the Tseel block in an area about 0.5 km by 6 km. The deposit consists of lenses and layers of length about 250 to 400 m long and 10 m to 80 m thick that are composed of biotite-garnet, pyroxene-epidote-garnet-magnetite and massive magnetite beds. Metamorphic garnet deposits occur at Altanhudag in the Tseel block. Grade ranges from 53% to 67% FeO and 42% to 52% Fe, and with a trace of Co, Ni, V and Mn. Local placer garnet deposits occur and are derived from garnet-jedrite-biotite lode metasomatitic bodies (Sokolov and Zaitsev, 1990). The metasomatites are extensive and occur in the Tseel, Bodonch and Uench blocks. A muscovite pegmatite with a 780 Ma isotopic age intrudes garnet-jedrite-biotite metasomatite (Sokolov and Zaitsev, 1990).

Origin and Tectonic Controls for

Tseel Metallogenic Belt

The belt is interpreted as forming during Fe sedimentation in an early to middle Riphean sedimentary basin and during granitoid magmatism along an active continental margin.

REFERENCES: Kleiner and others, 1977.

Tsenhermandal-Modot

Metallogenic Belt of

Metamorphic Graphite Deposits

(Belt TsM) Mongolia)

This Mesoproterozoic(?) metallogenic belt is hosted in Ereendavaa fragment of Argunsky passive continental margin terrane. The metamorphic graphite deposits and occurrences occur in a northeast-striking zone along the North Govi-South Hentei regional fault. Deposits and occurrences are hosted in Paleoproterozoic gneiss and marble, and also in middle and upper Riphean metamorphosed clastic and carbonate rocks. The deposits occur mainly in the southwestern Ereendavaa terrane, southeast of Ulaanbaatar. Age of metamorphism of host rocks is not known. Graphite deposits and occurrences are interpreted as forming during late Riphean metamorphism. The major deposit is at Zulegt.

Zulegt Metamorphic Graphite Deposit

This deposit (Milin and Stepanenko.,1967; P.Shaandar and others, written commun., 1992) consists of graphite-bearing quartzite and graphite skarn lenses that occur in intensively deformed Proterozoic metamorphic rock. The average thickness of the graphite-bearing quartzite bed is 20 meters and the length is 100-150 m. The average graphite content is 3.91-7.86%. The graphite skarn occurs in about 200 bodies with a thickness of 0.1-11 m. The deposit contains phenorocrystalline and coarse squamose types.The deposit age is interpreted as Proterozoic. The deposit is small with reserves of 0.96 million tonnes grading 6.28-10.65% graphite

Origin and Tectonic Controls for

Tsenhermandal-Modot Metallogenic Belt

This belt is interpreted as derived from carbon-and iron-bearing sedimentary rocks that precipitated in a basin along Riphean passive continental margin that was regionally metamorphosed in the upper Riphean.

REFERENCES: Kleiner and others, 1977.

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