By Sergey M. Rodionov1, Alexander A. Obolenskiy2
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Mugursk Metallogenic Belt ofBanded Iron Formation (BIF) Deposits(Belt MG) (southeastern Tuva, Altai-Sayan folded area, Russia)This Paleoproterozoic metallogenic belt is hosted in the Sangilen passive continental margin terrane and occurs in southeastern Tuva in the Sangilen Upland. The belt extends latitudinally for 70 km and is hosted in Precambrian rocks with ferruginous quartzite. The base of the host Precambrian rock sequence consists of uniform mica-plagioclase gneiss about 3000 m thick with garnet, sillimanite, and amphibole. The BIF deposit is hosted in gneiss and quartzite-graphite-schist in the upper part of the sequence. Ferruginous quartzite deposits occur mainly in the Erzin River basin in the Erzin Fe district (Matrosov and Shaposhnikov, 1988) that contains the Mugurskoye, Aryskanskoye, and other deposits. The more prospective deposit is at Mugurskoye. Abundant staurolite gneiss and numerous occurrences of corundum hornfels are high-alumina and ferrous host rocks in the Sangilen terrane. Mugurskoye Banded Iron Formation (BIF) DepositThis deposit (Matrosov and Shaposhnikov, 1988)consists of steeply-dipping layers of ferrous quartzite hosted in Precambrian metamorphic rock. The enclosing host rocks are micaceous quartzite, biotite schist, amphibolite, marble, ferrous quartzite, graphite schist. Ore layer varies from 4 to 10 m thick, extends up to 8 km along strike, and is strongly corrugated into small folds. Deposit layers consist of magnetite quartzite, hematite-magnetite quartzite, amphibole-magnetite quartzite, garnet-amphibole-magnetite schist, and high magnetite layers. Major minerals are quartz, magnetite, hematite, amphibole, cummingtonite, and grunerite. Secondary minerals are garnet, apatite, biotite, plagioclase, and pyrite. S content ranges from is 0.1 to 0.3% (sometimes up to 1.5 to 2%), and P content ranges from 0.2 to 0.4% (sometimes up to 0.8 to 1.9%). The deposit is small with an average grade of 30 to 47% Fe. Origin and Tectonic Controls forMugursk Metallogenic BeltThe belt is interpreted as forming in Tuva-Mongolian microcontinent margin as a fragment of Laurasia. BIF deposits occur in metamorphosed Paleoproterozoic sedimentary rocks (Zonenshain and others, 1990; Berzin and others, 1994). REFERENCES: Matrosov and Shaposhnikov, 1988; Zonenshain and others, 1990; Berzin and others, 1994. Khan Hohii Metallogenic Belt ofBanded Iron Formation (BIF) Deposits(Belt KH) (Northwestern Mongolia)This Paleoproterozoic(?) metallogenic belt is hosted in the Khan Hohii and the North Songino fragments of the Baydrag cratonal terrane. The major group of occurrence is at Tomorchuluut and is hosted in Fe quarzite (Bahteev and others, 1984). These belt extends along an east-west trend for about 100 km long and is about 50 km wide. Tomorchuluut Banded Iron Formation (BIF) DepositThis deposit (Filippova, 1977; Bakhteev and others, 1984) consists of bodies of silica-magnetite lenses and layers in Paleoproterozoic gneiss and greenstone schist. Bodies trend northwest, are concordant with host rock, and occur in an area 2.5 by 0.2 km. Approximately 10 occurrences similar to, and in the vicinity of the deposit, occur in a horizon of amphibolite and schist, in an northeast-trending area that is 17 km long. The length of silica-magnetite bodies ranges from tens of m to 2,000 m, and thickness ranges from 5 to 60 m. Main ore mineral is magnetite. The deposit is small with resources of 18 million tonnes magnetite grading 24-41% Fe. Origin and Tectonic Controls forKhan Hohii Metallogenic BeltThe BIF is hosted in Paleoproterozoic gneiss, amphibolite, crystalline schist marble and quartzite derived from a volcanic and clastic sedimentary rock basin that is interpreted as forming along a continental margin arc. REFERENCES: Bahteev, and Chijova, 1990; Tomurtogoo and others, 1999. Tarvagatai Metallogenic Belt ofBanded Iron Formation (BIF, Algoma Fe);and Mafic-Ultramafic Ti-Fe Occurrences(Belt TA) (Central Mongolia)This Paleoproterozoic(?) metallogenic belt is hosted in the Paleoproterozoic Tarvagatai fragment of the Baydrag (unit BD) cratonal terrane. The belt consists of BIF and mafic-ultramafic related Ti-Fe deposits. The major deposits are the Salbart occurrences and Most uul group occurrences in the northern and parts of the southern Tarvagatai fragment, respectively. The northeast-striking metallogenic belt is approximately 150 km long and 60 km wide. BIF OccurrencesVarious BIF occurrences, as in the Salbart Group are are hosted in lower Proterozoic gneiss, amphibolite, schist, marble, and quartzite in the Baydrag metamorphic complex (Bahteev and others, 1984). The host rocks are derived from volcaniclastic clastic sedimentary rock that formed in a small volcanic and sedimentary basin. Most uul Mafic-Ultramafic Fe-Ti OccurrencesVarious mafic-ultramafic related Fe-Ti occurrences in the Most uul group are related to early Proterozoic gabbro and anorthosite in the Most uul complex that consists of gabbro, pyroxenite, anorthosite, and gabbro (Izoh and others, 1984). The complex intrudes the Baydrag metamorphic complex and has isotopic ages for anorthosite of 1800 to 3000 Ma (Kozakov, 1986). The Baydrag complex is interpreted as forming in a continental margin arc. The Most uul massif that crops out over 150 km2. The massif consists mainly of anorthosite (90%). Main ore minerals are magnetite and ilmenite. Early magmatic disseminated and massive ore minerals occur mostly in an inner contact facies peridotite that is 1.0-2.0 km wide. Ore minerals constitute up to 30-40% host rock, form lenses ranging from 25-40 m up to 200 m thick, and up to hundreds meter long Early magmatic stage contains an average 5.0-6.0% TiO2. Postmagmatic ore occurs mostly in the central part of the massif, and is related to replacement veins and veinlets. The ore minerals are magnetite, ilmenite, and apatite. One zone is appoximately 50 m by 70 m. Grades are 30-40% Fe in peridotite and 50-60% Fe in post-magmatic zones, and 6-16% TiO2 and 12-16% TiO2, respectively. Origin and Tectonic Controls forTarvagatai Metallogenic BeltThe BIF occurrences are hosted in lower Proterozoic gneiss, amphibolite, schist marble and quartzite derived from a volcaniclastic and sedimentary sequence deposited in a small volcaniclastic basin. The anorthosite hosting the Ti-Fe occurrences is interpreted as forming in a continental margin arc. REFERENCES:; Izoh, Polyakov, and Krivenko, 1984; Kozakov I.K., 1986; Bahteev, and Chijova, 1990; Tomurtogoo and others, 1999. |