Noble and Non-Feerrous Resources of Georgia



Excluding small placers in Enguri and Khrami river basins (not more than 8,000 kg of Au in both), Au is mainly related to both base metal massive sulfide and porphyry copper formations (for getting geological & metallogenic framework, please,
click
here).

Excluding small placers in Enguri and Khrami river basins (not more than 8,000 kg of Au in both), Au is mainly related to both base metal massive sulfide and porphyry copper formations (for getting geological & metallogenic framework, please, click here). Two types of base metal massive sulfides are widespread in Georgia (Tvalchrelidze, 1995). The first one is related to typomorphic Cimmerian (Lower Jurassic) mineral formation in the Chkhalta-Tphani subterrane and consists of copper-pyrrhotite stratiform and vein ores (Adange, Zeskho, Artana). These deposits, thoroughly investigated by geological, mineralogical, geochemical, isotopic, and thermodynamic methods (Buadze and Tvalchrelidze, 1980; Yaroshevich and Tvalchrelidze, 1981; Tvalchrelidze, 1984; 1986; 1987; Tvalchrelidze and Chichinadze, 1985, etc.), represent hydrothermal-sedimentary copper massive sulfides that underwent replacement of pyrite by pyrrhotite during regional green schist metamorphism. According to existing data (Buadze and Tvalchrelidze, 1982; Tvalchrelidze, 1986; 1987) these copper-pyrrhotite deposits, in common, consist of three zones:

1.     Main ore zone presented by a concordant pyritic stratum metamorphosed into copper-bearing pyrrhotite;

2.    Sub-ore zone consisting of copper-pyrrhotite veins suggested to be metamorphic ore channels;

3.    Supra-ore zone built up non-commercial quartz-pyrite veinlets interpreted as a metamorphic halo.

This halo is suggested to be formed a result of sulfur removal from stratiform orebodies during "pyrrhotinization" of pyrite. It is interesting to note that there is a direct relation between composition of pyrrhotite (including its sulfur isotopic composition) and type of ores (inherited stratiform or vein). If the concordant bodies are presented by typical hexagonal pyrrhotite Fe10S11, veins consist of admixture of pseudohexagonal and monoclinic pyrrhotites, which have a varying composition from Fe6S7 up to Fe8S9 (Tvalchrelidze and Chichinadze, 1985). This event may be explained by kinetics and thermodynamics of interaction of pyritic bodies and cupriferrous hydrothermal-metamorphic solutions (Tvalchrelidze, 1986). Copper supply during metamorphism of pyrite bodies is proved by: (i) constant difference in Cu content in vein and stratiform ores; (ii) absence of Cu in supraore zone; (iii) constant difference in Cu content in relict pyrite and inherited-stratiform Cu-pyrrhotite ores; (iv) crystallographic and experimental data demonstrating obligatory metamorphic "shrinkage" in course of the "pyrrhotinisation" process (Tvalchrelidze, 1987). The latter process is due to the fact that the volume of elemental cell of pyrite (about 0.1584 nm3) is over than that of hexagonal pyrrhotite - 0.05829 nm3 (Tvalchrelidze, 1987). Experimental data (Tvalchrelidze and Pataridze, 1986) demonstrated that pyrrhotite formed as a result of thermal decomposition of pyrite occupies 30% less volume than the iron disulfide. As inherited-stratiform Cu-pyrrotite ores have a massive structure, it seems logical to suppose that free space was occupied by quartz-non-ferrous paragernesis. Calculation of matter balance and comparison of these data with Cu content in different ores indicate that about 25% of Cu was supplied during metamorphism.

The Table below demonstrates that three important deposits of this type have only a minor gold content but are characterized by important copper reserves.


Reserves of Copper-Pyrrhotite Deposits


Deposit Metal Grade, % Reserves, t
Adange Cu 2.90 250,000
Zesxo Cu Zn 3.50 1.67 801,000 101,000
Artana Cu 3.87 350,000


The second group of base metal massive sulfide deposits is related to the Bolnisi Mining District. These deposits were formed in Early Alpine time within the limits of the Somkhito-Karabakh terrane. Au-Ag-Cu-Pb-Zn-barite mineralization is connected with volcanic depressions of calc-alkaline homodrome volcanism and has many features of the Kuroko-type ores. The main difference of these deposits from the typical Kuroko ores (Geology..., 1974) consists in their subvolcanic metasomatic origin (Kekelya et al., 1984). Deposits are characterized by vertical zoning (Gogishvili et al., 1976; Ore..., 1982): in ascending section Cu ores are replaced by lead-zinc and, then, barite bodies. Commercial contents of Au are related to both Cu (pyrite-chalcopyrite) ores and ore-hosted quartz-alunite-sericite metasomatic rocks. Among them the largest is the Madneuli Mine. The latter represents a zonal deposits of the bottom of which typical pyretic ores are widespread.




Pyritic Ores at Madneuli Mine. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili Tbilisi State University

At the upper horizons of the mine these ores are gradually replaced by copper-pyritic and, then, by lead-zinc bodies. The column is terminated by typical barite-polymetallic and barite ores. In addition to typical base metal massive sulfides their hosting hydrothermally altered rocks bear significant reserves of gold.




Copper-Pyritic Ores at Madneuli Mine. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili

Tbilisi State University




Lead-Zinc Ores at Madneuli Mine. A. Tvalchrelidze Mineralogical Museum, I. Javakhishvili

Tbilisi State University




Gold-Bearing Quartzites at Madneuli Mine. A. Tvalchrelidze Mineralogical Museum, I.

Javakhishvili Tbilisi State University

Madneuli Mine is owned by the state-owned Joint Stock Company Madneuli, which operates
the open pit and produces the gold-bearing copper concentrate.




Open Pit of the Madneuli Mine

The company Quartzite Ltd operates gold-bearing quartzites by the heap leaching technology.




Gold Heap Leaching Unit at the Madneuli Mine

Table below demonstrates ore and metal reserves of the mine




Economic Characteristics of the Madneuli Mine


Ore Type Element Grade, % Reserves, t (kg for Au)
or mineral Ores Element or mineral Already mined ele-ment or mineral
Cu-pyrite Cu Au Ag S Se Te 1.28 0.000073 0.000431 6.92 0.000710 0.000759 79,087,500 516,700 5,773 34 5,472,855 56,152 60,027 67,700 756 5 717,074 7,357 7,865
Cu-Zn Cu Zn 0.39 1.80 1,425,200 5,558 25,654
barite-polymetallic barite Pb Zn 31.7 0.62 4.09 1,324,000 419,708 8,209 54,152 125,306 5,900 10,600
barite barite 36.3 338,000 122,694 122,694
Au-bearing quartzites Au Ag 0.000180 0.000915 10,896,000 48,247 100 1,250 5.6


Metal reserves of other important deposits (Tsiteli Sopeli, David-Gareji, Kvemo Bolnisi, Sakdrisi)
of the Bolnisi Mining District are shown below.


Metal Reserves in Small Deposits of the Bolnisi Mining District


Deposit Metal Grade, % Reserves, t (kg for Au)
Sakdrisi Au Ag Cu 0.000193 0.000300 1.03 19,800 22 77,600
Tsiteli Sopeli Au Ag Cu 0.000070 0.000400 1.58 8,000 4 202,800
David Gareji Au Ag Pb Zn Cu 0.000250 0.001500 2.50 5.00 0.80 5,000 169 50,000 100,000 16,800
Kvemo Bolnisi Cu 1.46 80,000


In close vicinity to these deposits the Dambludi veins host 1,882 kg of Au with grade of 1.18 ppm; 50.63 tons of Ag (30.10 ppm); 13,700 tons of Cu (0.73%); 47,600 tons of Pb (2.5%); 95,900 tons of Zn (5.3%); 49.5 tons of In (26.5 ppm).

The Merisi Mining District in the Ajara-Trialeti subterrane is much smaller. Merisi-Namonastrevi granodiorite-monzonite complex in Mountainous Adjara is surrounded by a number of polymetallic quartz veins that form a peripheric zone of a porphyry copper system with typical regional and local rhythmical zoning (Tvalchrelidze et al., 1991; Tvalchrelidze, 1992). Polymetallic lodes have been mined since the beginning of our century. Mining have been cancelled during the Second World War. Present-day reserves of this district are shown in Table below.




Varaza Vein Au-Cu-Pb-Zn Ores at the Merisi Mining District. A. Tvalchrelidze Mineralogical
Museum, I. Javakhishvili Tbilisi State University


Noble and Non-Ferrous Metal Reserves in the Merisi Mining District


Metal Grade, % Reserves, t (kg for Au)
Au Ag Pb Zn Cu 0.000071 0.001870 1.80 1.40 2.84 859 16 15,000 11,000 74,800


In addition to these typical auriferous ore formations, about 10 tons of gold (with grade of 0.5-3.5 ppm) and at least two times more of economic resources are known in the Lukhumi Au-As Mine characterized by very unusual geological features (Tvalchrelidze, 1961). This Mine belongs to the Carlin-type deposits, where realgar-orepigment mineralization is encountered in a thick stratum of limestones among rhythmical calcaceous Upper Cretaceous affinity. The ore zone is related to a long-living deep fault at the margin of the Mestia-Tianeti and the Chkhalta-Tphani subterranes. Gold-bearing arsenopyritic impregnation form a halo between the handing wall of the fault and the lying contact of realgar-orepigment veinlet bodies.

Beyond the Madneuli and the Merisi mining districts, there are 8 lead-zinc deposits in Georgia. All of them are distributed into the Gagra-Java subtarrane and were formed during the Early Alpine mineralisation epoch. These deposits belong to two genetic groups: (i) Late Jurassic - Early Cretaceous (?) Mississippi-Valley-type limestone-related ores that lie just on the roof of Jurassic evaporites in the North-Western Caucasus (Brdzyshra and Dzyshra); (ii) Cretaceous telethermal sphalerite-galena-quartz-calcite subvertical lodes of enormous and large vertical extension (over 1,500 m at the Kvaisi Mine, about 300-500 m at other deposits: Skatykom, Razdarankom, Amtkheli, etc.). These veins have important admixture of Ag, Ga, Ge, Se, Te, Tl (Zhabin et al., 1982). Among them the largest is the Kvaisi Mine reserves of which is given in Table below.




Quartz-Calcite-Chalcopyrite-Sphalerite Vein of the Kvaisi Mine. A. Tvalchrelidze Mineralogical
Museum, I. Javakhishvili Tbilisi State University




Sphalerite-Chalcopyrite (left) and Galena (right) Vein Ores at the Kvaisi Mine. A. Tvalchrelidze
Mineralogical Museum, I. Javakhishvili Tbilisi State University


Ore/Metal reserves at the Kvaisi Mine


Element Grade, % Reserves, t
Ores Metal Already mined metal
Pb Zn Ag Cd 2.24 6.47 0.001540 0.02 2,851,000 56,200 197,700 18 279 37,600 134,200 34 418


Resources of important Ga, Ge, Tl, Se, Te admixtures have not been calculated. Reserves of other
deposits are shown below.


Metal Reserves in Small Lead-Zinc Deposits


Deposit Metal Grade, % Reserves, t
Skatikom Pb 6.71 9,800
Razdaranrom Pb Zn 1.50 1.00 5,100 990
Amtkheli Pb Zn 2.36 3.80 3,360 7,300
Rtskhmeluri Pb Zn 1.61 2.67 4,100 6,800
Brdzyshkha Pb Zn 1.20 1.00 15,500 23,200


Thus, total reserves of precious and non-ferrous metals in Georgia are as follows:

Bulk Reserves of Noble and Non-Ferrous Metals in Georgia


Metal Reserves, t (kg for Au)
Au 104,636
Ag 448
Cu 2,389,000
Pb 214,900
Zn 623,700
Se 56
Te 60
In 21
Cd 834
Bi 181


An unusual Gelati Al deposit must be mentioned separately. Here this metal is presented by Al-bearing zeolite - analcite. Al presence is determined by specific Early Alpine autigene ore formation in the Dzirula subterrane. The deposit represent a 31.2-114.5 m-thick stratum of analcite sandstones composed of analcite, quartz, feldspar, mica, pyrite and calcite. Analcite occupy about 80-90% of the sandstone matrix, and content of Al2O3 reaches 18.9%. Reserves of these ores in the district, explored only partially, are over 300,000,000 tons, whereas the Gelati deposit itself hosts 176,000,000 t of ores. Unfortunately, Georgia, being an inseparable part of the USSR, was unable to work out an efficient technology of Al2O3 leaching.


References


ABuadze V.I., Tvalchrelidze A.G. (1980) - Geological, geochemical, and physico-chemical conditions of formation of stratiform non-ferrous deposits in sedimentary rocks of the Caucasus. In J.D. Ridge (ed.) Proc. Fifth Quadrennial IAGOD Symposium, Vol. 1: Stuttgart, E. Schweizerbart'sche Verlagbuchhandlung, 245-260.

Geology of Kuroko deposits (1974) - Soc. Min. Geol. Japan, 438 p.

Gogishvili V.G., Guniava V.D., Ratman I.P., Gogishvili T. Sh. (1976) - Poste-Eocene ore formation in the Transcaucasia (Somkhito-Karabakh and Gagra-Java zones),. USSR Acad. Sci. Trans., Ser. geol., N 11, 99-115 (in Russian).

Kekeliya S.A., Tvalchrelidze A.G., Yaroshevich V.Z., (1984) - The geological and physicochemical conditions of formation of massive-sulfide-barite-base metal deposits. Intern. Geol. Rev., 26, 1437-1444.

Ore deposits of the Caucasus (1982) - G.A. Tvalchrelidze (ed.) Gudebook. Tbilisi, Metsniereba Publ., 141 p.

Tvalchrelidze, A.G. (1984) - Petrologic mechanisms of origination of pyrite-bearing hydrothermal systems. Geologica Carpathica, 35, 91-103.

Tvalchrelidze, A.G. (1986) - Physico-chemical conditions of base Metal massive sulphide formation. In: C.H. Fridrich et al. (eds.) Geology and Metallogeny of Copper Deposits, Springer Verlag, 358-369.

Tvalchrelidze A.G. (1987) - Geochemical conditions of formation of base metal massive sulphide deposits. Moscow, Nedra Publ., 188 p. (in Russian).

Tvalchrelidze A.G. (1990) - Three-dimensional quantitative models of vein-type ore deposits and a theory of rhythmical zoning . 8th IAGOD Symposium, Abstracts, A231.

Tvalchrelidze A.G. (1992) - A zonal and paleotemperature model for plutonogenic polymetallic ore districts and fields. Geology of Ore Deposits, N 1, 58-69 (in Russian).

Tvalchrelidze A.G. (1995) - Development of a geological-economic system for governmental management of Georgian mineral resources. John D. & Catherine T. MacArthur Foundation, Tbilisi, 89 p.

Tvalchrelidze A.G., Chichinadze M.K. (1985) - Features of pyrrhotite in pyritic stratiform and vein ores in black schists. Intern. Geol. Rev., 27, 492-501.

Tvalchrelidze A.G., Pataridze D.V. (1986) - Experimental investigation of pyrite thermal decomposition in vacuum. Trans. of the USSR Mineralogical Society, CXV, issue 6, 727-735 (in Russian).

Tvalchrelidze A.G., Magalashvili A.G., Kikava A.A. (1991) - Thermophysical simulation of the Merisi Mining District. Tbilisi, A. Jandelidze Geological Institute, 23 p. (in Russian).

Tvalchrelidze, G.A. (1961) - Endogenous metallogeny of Georgia. Moscow, Gosgeoltekhizdat Publ., 344 p. (in Russian).

Yaroshevich V.Z., Tvalchrelidze A.G. (1981) - Distribution of sulfur isotopes in iron sulfides of some types of pyrite deposits. Intern. Geol. Rev., 23, 524-534.

Zhabin A.G., Tamazashvili N.A., Meshveldishvili T.A., Naniev M.I., Margiev M.A. (1982) - Deep forecasting of polymetallic ores at the Kvaisi ore field. USSR Acad. Sci. Bull., 265, 410-413.