During the second half of the 20th century, several

dozen large and medium deposits of disseminated

pyrite–marcasite ores with total gold reserves of more

than 6000 t and annual gold production of ~200 t were

found in the Basin and Range Province, Nevada, United

States [1, 2]. This unique gold district is termed as the

Carlin trend. The limited development of the Carlintype

mineralization in other gold districts of the world

is presently a debated issue. Naturally, each Carlin-type

mineralization inferred beyond Nevada requires

detailed investigations. In 2004, we began to study the

Alshar deposit with Carlin-type mineralization together

with Macedonian geologists [3]. The Alshar deposit is

a large object in terms of Tl reserves and a medium

reserve in terms of inferred Au reserves [3, 4]

Kochneva, Nina T.

Serafimovski, Todor

Tasev, Goran

Tomson, Ilmar N.

Volkov, A.

UGD Academic Repository

 175 ISSN 1028-334X, Doklady Earth Sciences, 2006, Vol. 407, No. 2, pp. 175–178. © Pleiades Publishing, Inc., 2006.Original Russian Text © N.T. Kochneva, A.V. Volkov, T. Serafimovski, G. Tasev, I.N. Tomson, 2006, published in Doklady Akademii Nauk, 2006, Vol. 406, No. 6, pp. 784–787. During the second half of the 20th century, severaldozen large and medium deposits of disseminatedpyrite–marcasite ores with total gold reserves of morethan 6000 t and annual gold production of ~200 t werefound in the Basin and Range Province, Nevada, UnitedStates [1, 2]. This unique gold district is termed as theCarlin trend. The limited development of the Carlin-type mineralization in other gold districts of the worldis presently a debated issue. Naturally, each Carlin-typemineralization inferred beyond Nevada requiresdetailed investigations. In 2004, we began to study theAlshar deposit with Carlin-type mineralization togetherwith Macedonian geologists [3]. The Alshar deposit isa large object in terms of Tl reserves and a mediumreserve in terms of inferred Au reserves [3, 4].The territory of Macedonia experienced long-termgeological evolution. Its majority is occupied by theSerbian–Macedonian and Pelagonia crystalline mas-sifs, separated by the Mesozoic Vardarian riftogenicgraben (Fig. 1). Macedonia is located in the Serbian–Macedonian part of the Eurasian Tethys metallogenicbelt. Mineralization related to the Cenozoic activationin this area is expressed in the formation of volcanoplu-tonic associations in the dispersed spreading environ-ment [4]. The activation spanned the Serbian–Mace-donian Massif and part of the Vardarian riftogenic zone.Superimposed structures of this period occur as narrowNW-trending grabenlike depressions complicated bylocal ring structures of the chamber type.Previous joint works with Macedonian geologistsshowed that the present-day tectonic structure of Mace-donia reflects dislocations closely related to Cenozoicmagmatism and productive mineralization. These dis-locations were reconstructed from tectonic elements ofthe present-day relief surface using morphostructuralanalysis and deciphering aerial and satellite photo-graphs. Based on the dislocations, we distinguishedthree (Oligocene–Miocene) NW-trending metallogeniczones superimposed onto the metamorphic sequence ofthe Serbian–Macedonian Massif. They are mainly com-posed of the Cenozoic tuffogenic–sedimentary and vol-canic sequences and are crosscut by granitoids anddikes of intermediate composition. The metallogeniczones compose an ore belt (Fig. 1), which extends tothe northwest (Serbia) and southeast (Greece and Bul-garia).From southwest to northeast, the metallogeniczones show variation in ore type and decrease in age ofmagmatic complexes and ores. One can see a distinctcorrelation between age and ore composition. North-eastward, the mineralization evolves from high-temper-ature (relatively low-sulfide) to low-temperature(polysulfide) types. The directed change of ore compo-sition can be related to differentiation of ore matter inthe deep-seated chambers. The ore type changes acrossmetallogenic zones in the following way: skarn–mag-netite ores (Borov Dol deposit), porphyry copper ores(Buchim), base metal copper ores (Kratovo–Zletovo),and base metal ores (Sasa and Toranica). In the SW–NEdirection, the age of ore-magmatic clusters varies in thefollowing order: 28–24.5 Ma (Borov Dol–Buchim dis-trict), 27.2–16 Ma (Kratovo–Zletovo district), and 24–12 Ma (Sasa–Toranica district). Deposits of the latterdistrict are the youngest ones. Thus, one can see a dis-tinct compositional trend caused by decreasing age anddifferentiation. These features suggest the existence ofa link between the metallogenic zones at depth.The Pliocene Kozuf–Arid metallogenic zoneextending along the Greek–Macedonian boundary (Fig. 1)is located in southernmost Macedonia. In addition tothe Alshar deposit, this zone also incorporates several Tectonic Position of the Alshar Au–As–Sb–Tl Deposit, Macedonia N. T. Kochneva 1, A. V. Volkov 1 , T. Serafimovski 1 , G. Tasev 2, and  Corresponding Member of the RAS  I. N. Tomson 1 Received September 20, 2005  DOI:  10.1134/S1028334X06020036 1  Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017 Russia; e-mail: alexandr@igem.ru 2  Faculty of Mining and Geology, Kiril and Methodie University of Skopje, Goce Delcev 89, 92000 Shtip, Macedonia GEOLOGY 176 DOKLADY EARTH SCIENCES      Vol. 407     No. 2     2006 KOCHNEVA  et al. Sb–As–Au occurrences, porphyry copper deposits, andnative sulfur occurrences. The mineralization is dis-tinctly related to the Pliocene volcanoplutonic complexdeveloped along the main regional fault zone betweenthe Pelagonia crystalline block on the west and Vardarzone on the east. The rock complex includes differenttypes of andesites and quartz latites. Volcanic and plu-tonic activity lasted from 7 to 1.8 Ma [4].Ore mineralization at the Alshar deposit is devel-oped as mineralized breccia at the contact of volcaniccover with dolomites, jasperoid beds in the carbonaterocks, and vein–disseminated zones in dolomites andTertiary volcanic rocks.The Alshar deposit includes several ore bodies withspecific geochemical association of elements and com-position. This is the only deposit in Macedonia, whichhas economic-grade contents of Tl (0.1–0.5%), Sb (upto 2.5%), As (1.5%), and gold (>1 g/t). It should benoted that gold is unevenly distributed in the ores. Thehighest Au contents (3–4 g/t; occasionally, up to 20 g/tor more) were found in jasperoid zones in the southernpart of the deposit [3].By analogy with the Carlin-type deposits in Nevada,Percival and Radtke [3] distinguished four economic-grade types of gold ores at the Alshar deposit: (1) Sb–Au jasperoid ore (+ Au + As + Tl); (2) siliceous gold ore(+Au + Sb + Tl); (3) As–Au ore (+ Tl + Hg + Sb + Au);and (4) Tl ore.The ores form three mineral assemblages of differ-ent ages: pyrite–marcasite, antimonite, and orpiment–realgar–lorandite.The tectonic position of the Alshar deposit area wasdeciphered with morphostructural analysis and satelliteimages. First, we determined the present-day struc-tural–tectonic plan of the southern part of Macedonia.For this purpose, we applied the known method of mor-photectoisohypse, which implies subsequent generali-zation of contour lines and analysis of the river net-work. Analyzing the present-day surface with different-order structural elements of the relief, structures of dif-ferent taxonomic ranks were outlined.The Alshar deposit is located at upper reaches of theRozhdenska River (right tributary of the Crna river). Thestreams in the Rozdenska River basin form a nearly idealradial-centripetal pattern on the plan (Fig. 2). U-shapedridges from 1500 to 1800 m high outline the radial-centripetal river channels. The ridges are followed byU-shaped valleys. Such an orography suggests anendogenous ring structure (18  ×  15 km across) with arelatively subsided central part and uplifted peripheralbelt. The ring structure is situated at the intersection oftwo extended diagonal deep-seated fault zones. Thenorthwestern fault belongs to the Vardar zone. Thenortheastern fault deciphered from linear anomalies ofcolor in the satellite image is emphasized by linearity ofthe Boshavica River valley, bends in the present-dayrelief, and a chain of domal structures no more than Fig. 1.  Tectonic scheme of Macedonia. ( 1 ) Serbian–Macedonian Massif; ( 2 ) Vardarian riftogenic graben; ( 3 ) Pelagonia Massif;( 4 ) West Macedonian area; ( 5 ) Cenozoic metallogenic zones and fault systems; ( 6 ) Vardarian metallogenic zone; ( 7 ) boundary ofthe Macedonia Republic SerbiaBulgariaGreeceAlbaniaAlshar0 20 km22°00  41°00  1 2 3 4 5 6 7 DOKLADY EARTH SCIENCES      Vol. 407     No. 2     2006 TECTONIC POSITION OF THE ALSHAR Au–As–Sb–Tl DEPOSIT 177 10 km across. In addition, one can also see a system ofthe younger NE-trending faults with related Pliocenevolcanic flows. The Alshar ring structure is rimmed bya belt of subordinate domes no more than 5 km acrossalong its periphery. Each of these structures can becomparable with the associated ore-hosting magmachambers (Fig. 2). Three subordinate domes locatedsouth of the Alshar structure in Greece have the mostcomplex structure and contrast morphology. By analogywith other studied regions, such associated structureshost large ore districts and deposits [5].The tectonic position of the Alshar deposit isemphasized by the morphology of geochemical halos.The Fe–Ni halo extends along the Vardar zone, whilethe Sb–As–Tl–Pb–Zn–Cu halo coincides with theyoungest NE-trending fault system that extends acrossthe Oligocene and Miocene metallogenic zones (Fig. 2).According to Yankovic [4], the main ore-controllingstructure of the Alshar deposit is represented by thevery wide and extended meridional fracture zone,which is radial with respect to the ring structure. At thesame time, satellite image of the deposit shows a latitu-dinal fault zone that also represents a fragment of thelarge and extended system.Thus, morphostructural analysis and deciphering ofsatellite images showed that the Alshar deposit is con-fined to the central part of the ring structure located atthe intersection of two large diagonal fault zones,which host mineralization of different ages. The depositoccupies a special structural position within southern Fig. 2.  Morphostructures of southern Macedonia. Hypsometric levels (m): ( 1 ) 1500–2000, ( 2 ) 1000–1500, ( 3 ) 500–1000, ( 4 ) below 500;( 5 ) zones of diagonal dislocations; ( 6 ) boundaries of ring structures; ( 7 ) orthogonal deep-seated faults; ( 8 ) other faults; ( 9 ) geochem-ical halos; ( 10 ) Alshar deposit. Crna R.Rozdenska R.Boshavica R. Fe–NiSb–As–Tl–Pb–Zn–CuAlsharÄu2 0 2 4 6km 1 2 3 45 6 7 8 9 10 178 DOKLADY EARTH SCIENCES      Vol. 407     No. 2     2006 KOCHNEVA  et al. Macedonia. Geological, geochemical, and morpho-structural investigations indicate that this structure rep-resents a center of long-term endogenous activity,which appeared in Jurassic–Cretaceous and evolvedduring subsequent epochs.ACKNOWLEDGMENTSThis work was supported by the Russian Founda-tion for Basic Research, project nos. 03-05-64095,03-05-64334, 04-05-64359.REFERENCES 1. A. H. Hofstra and J. S. Cline, Rev. Econ. Geol.  13 , 163(2000).2. T. G. Theodore, B. B. Kotlyar, D. A. Singer,  et al.,  Econ.Geol.  98 , 287 (2003).3. T. J. Percival and A. Radtke, Can. Mineral., No. 32, 649(1994).4. S. Jankovic, Neues Jahrb. Mineral. Abh.  166 , 25 (1993)5. A. V. Volkov and A. A. Sidorov,  A Unique Gold Districtof Chukotka  (Sev.-Vost. Kompleks. Nauch. Issled. Inst.,Magadan, 2001) [in Russian].

Tectonic Position of the Alshar Au–As–Sb–Tl Deposit,

Macedonia

http://eprints.ugd.edu.mk/1589/1/Tectonic%20position%20of%20the%20Alshar%20Doklady%202006.pdf

Tectonic Position of the Alshar Au–As–Sb–Tl Deposit, Macedonia

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