COPPER MINES, CHROMITE-CONTAINING COPPER ORES AND SLAGS OF THE ISHKININSKY ARCHAEOLOGICAL MICRODISTRICT (SOUTHERN URALS)*

The structure of mines, the composition of copper ores and donkeys from the Ishkininsky archaeological microdistrict in the Orenburg region are considered. Ores and donkeys contain inclusions of chromites inherited from host hyperbasites. Chromites are divided into three groups according to the Cr2o content 3 - 45 - 50 50 - 55 and 55 - 61%. Similar parameters are characteristic of chromites from malachite-bearing ores of the Ishkininsky cobalt-copper-pyrite deposit. Copper sulfides, as well as iron phosphides with a high nickel content, are present in the copper kings of donkeys. The data obtained indicate the use of local copper ores by paleometallurgists. The article presents an overview of the distribution of chromite-bearing ores and donkeys on the archaeological sites of the Southern Urals and outlines the tasks of future work.

Keywords: copper, copper ores, donkeys, malachite, goethite, chrome spinelides, sulfides, hyperbasites, Bronze Age, Ural, Ishkinino.

Introduction

In the late Bronze Age, the Southern Urals was part of the Eurasian Metallurgical Province, which united several mining and metallurgical centers [Chernykh, 2007, p.76]. In the province, a series of discretely located compact groups of archaeological sites are identified, tending to ancient mining workings (Figure 1). The Ishkininsky archaeological microdistrict in the Sukhaya Gubernia River valley in Eastern Orenburg region is among the most well-supplied with ore sources (Figure 2), which can be regarded as a reference for the Ural-Mugodzhar mining and metallurgical center Late Bronze Age (Tkachev, 2011a). The Ishkininsky cobalt-copper-pyrite deposit, which was developed in ancient times, is located on the territory of the microdistrict (Yuminov and Zaikov, 2002). Since an archaeological microdistrict usually covers the area of operation of a stable economic structure and a separate social unit [Sinyuk, 1990, p. 6], then, taking into account the industrial specialization of the population in this case, lo is recorded-

* The research was supported by the interdisciplinary project of the Ural Branch of the Russian Academy of Sciences "Nature and Society of the Southern Trans-Urals in the Bronze Age: an interdisciplinary analysis of archaeological sites". The authors are grateful to G. I. Zaitseva, P. F. Kuznetsov for determining the age of archaeological sites, A. S. Aleshinskaya, M. D. Kachalova, E. A. Spiridonova for conducting palynological studies, V. A. Kotlyarov, E. I. Churin, P. V. Khvorov for analytical studies, E. V. Zaikova, O. L. Buslovskaya for technical assistance in preparing the article.

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Figure 1. Layout of Bronze Age mines and settlements in the Southern Urals (compiled using data from [Zdanovich and Batanina, 2007]). The inset shows the position of the Ishkininsky archaeological microdistrict (I) in Northeastern Eurasia. 1 - ancient mines with chromite-containing ores; 2-ancient mines where no chromite-containing ores were detected; 3-Bronze Age settlements with chromite-containing slags; 4-Bronze Age settlements where no chromite-containing slags were detected; 5-modern settlements; 6-western seam of the Main Ural Fault; 7 - boundary of the proposed site of the Ural Fault. division of the southern and northern groups of settlements with different sources of copper raw materials.

a municipal metal production center based on the exploitation of this deposit.

The ancient quarries identified by K. D. Subbotin in 1940-1942 during geological exploration were not known to archaeologists for a long time. In the late 1950s, this site was visited by Aktobe geologist R. A. Segedin, who discovered a massive stone hammer on the dump of an ancient mine [Tkachev, Segedin, and Greshner, 1996, Fig. 13]. Exploration of the deposit, during which information about ancient quarries was obtained, was carried out in 1957-1965 under the direction of A. P. Sidorenko and A. G. Poluektov. In 1992, an expedition of the Orsk Museum of Local Lore, headed by S. N. Satsedateleva and O. F. Bytkovsky, discovered the Bronze Age settlement of Ishkinovka on the northern flank of the ore field. A detailed study of ancient quarries was carried out in 1998-2001 by A. M. Yuminov and V. V. Zaikov [2002]. During several field seasons from 1996 to 2004, V. V. Tkachev carried out archaeological excavations of burial grounds north of the ore field, during which materials of the Yamnaya, Sintashta and Alakul cultures belonging to different periods of the Bronze Age were obtained [Tkachev, 2005, 20116].

A new stage in the study of the Ishkininsky archaeological microdistrict is associated with the implementation of the RFBR project No. 08-06-00136a on a comprehensive study of the Ural-Mugodzhar mining and Metallurgical center of the Late Bronze Age. In 2007, 2009-2010. The archaeological expedition of the Orsk Institute of Humanities and Technology under the leadership of V. V. Tkachev with the participation of A. V. Fomichev and S. M. Umrikhin conducted a detailed archaeological survey. A group of necropolises was identified, and work began on a stationary study of the settlement and mine workings, accompanied by paleosoil, palynological, geoarchaeological studies, and sampling for radiocarbon dating.

Mineralogical interest in the monument is caused by the presence in the ores of the Ishkininsky cobalt-copper-pyrite deposit of FeCr2O4 chromite, a mineral from the chrome spinel group, which contains Mg, Al, Ti, Mn, Zn, and V as impurities in various proportions. It is a refractory mineral, the melting point of high-chromium varieties reaches 2180 °C [Bolshaya Sovetskaya entsiklopediya, 1978, p. 400]. Chromite is a typical accessory mineral of hyperbasites, so its presence in slags is an indicator of the use of ores spatially associated with these rocks. Hyperbasites consist of olivine and pyroxenes, and their main differences, containing chromite, are dunites and harzburgites (Geologicheskiy Slovar', 1973, p. 120). Hydrothermal and metamorphic processes transformed hyperbasites into talc-carbonate rocks and serpentinites.

The purpose of the article is to provide a comprehensive description of the ancient mine, chromite-containing ores and slags identified on the territory of the Ishkininsky archaeological microdistrict. This will allow you to get a description of the reference object where the extraction, processing and metallurgical processing of copper ores took place. Previously, such comparisons for the ancient mines of the Southern Urals were indirect,

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2. Layout of archaeological sites in the Ishkininsky archaeological microdistrict, a -mine; b-settlement; c-burial grounds; d-locations of artifacts; e-roads.

1-Ishkininsky mine; 2 - Ishkinovka; 3-Ishkinovka I; 4-Ishkinovka II; 5 - Ishkinovka III; 6-Aulgan I; 7-Aulgan II; 8-Aulgan III; 9-Aulgan IV; 10-Sukhaya Gubernya I; 11-Sukhaya Gubernya II; 12 - Sukhaya Gubernya III; 13-Dry Drop IV.

because chromite-containing slags did not have an exact reference to the places of ore extraction.

Data on the structure of ore deposits were obtained as a result of mapping, mining operations, and testing of mine workings with the participation of I. Yu. Melekestseva, A. Yu. Dunaev, and R. R. Shavaleev [Zaikov et al., 2009, pp. 27-37]. Yu. I. Starostin, Director of the Gaisky Mining and Processing Plant, assisted in the opening of ancient workings and provided earthmoving equipment. Using an excavator, seven trenches were completed, which made it possible to study the structure of the dumps. In addition, the dumps of five quarries were opened manually in the field season of 2009 by the expedition of V. V. Tkachev.

The mineral composition was studied at the Institute of Mineralogy of the Ural Branch of the Russian Academy of Sciences using OLYMPUS optical microscopes, a SEMMA 202M X-ray spectral microanalyzer (analyst V. A. Kotlyarov), and a JEOL-733 microprobe analyzer (analyst E. I. Churin). The ore samples were enclosed in an epoxy resin-based preparation and polished. Their study determined the properties of chromites and other minerals. To establish the identity of chromites from slags and copper ores, the composition of sulfide and malachite-containing ores and their host rocks was studied. X-ray fluorescence method was used (analyst P. V. Khvorov) and chemical analysis (Yuminov et al., 2009).

Characteristics of the Ishkininsky archaeological microdistrict

The Late Bronze Age in this microdistrict is associated with a group of compactly located synchronous monuments, represented by mining workings, a settlement, a series of localities and burial grounds (Figure 2). Most likely, they belonged to a single economic and cultural center based on a combination of mining and metallurgical production and cattle breeding [Tkachev, 20116].

Mining operations are located on the left bank of the Aulgan Stream , a left tributary of the Sukhaya Gubernia River. On the opposite bank of the stream, the settlement of Ishkinovka was located on a flat area. Exploration pits and a small excavation were laid on the settlement area, which opened two economic complexes with light frame sheds and wells dedicated to housing depressions. The cultural layer in this part of the settlement reached 1 m. In addition to mass osteological material, a representative collection of ceramics, stone, clay, bone and metal tools, metallurgical and ceramic slags was obtained during the work. The vast majority of pottery fragments correspond in technological and morphological characteristics, ornamentation and technique of its application to the ceramic complex of the Alakul burial grounds Ishkinovka I-III. However, some fragments of vessels with a smooth profile, a taped roller on the neck and cross ornaments found in the upper horizons of the cultural layer, most likely belong to the final Bronze Age.

In the immediate vicinity of the mine and the settlement, a series of Late Bronze Age pottery sites were found that do not form a cultural layer. They can be considered as points of periodic visits related to the peculiarities of pastoral forms of cattle breeding and trade and exchange operations. One locality (N 8) was found on the bank of an unnamed stream near its confluence with the Aulgan, two localities (N 7, 6) - on sites on both sides of the Aulgan at the mouth of an unnamed stream, and another (N 9) - at the confluence of the Aulgan with the Sukhaya Gubernia River. Ceramics and bones of domestic animals were found on the left bank of the river 1 km upstream from the mouth of the stream (localities N 10, 11).

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Another compact group of Late Bronze Age archaeological sites is located on the right bank of the Sukhaya Gubernia River to the north of the described sites. At the mouth of its right tributary, the Zheriklinsky Stream, on the edge of a gentle watershed hill, Ishkinovka I (N 3) burial ground was located. Not far from it, on a promontory - shaped site, a site of Bronze Age ceramics was discovered (N 12). 2 km upstream of the Sukhoi Gubernia is the Ishkinovka II burial mound (N 4), and another 1 km upstream is the Ishkinovka III burial mound (N 5). Between them, the location of ceramics was revealed (N 13). By the nature of the artifacts, the monuments belong to the Alakul culture [Ibid.].

Structure of the deposit and dumps of ancient mine workings

The deposit is located in the axial part of the Main Ural Fault, to which hyperbasites are confined. The latter are transformed by tectonic deformations into a block melange - a mosaic joint of blocks that have experienced significant displacements, as a result of which various hyperbasites with different chromites compositions are spatially connected.

Copper mineralization forms two ore-bearing zones: east and west, confined to the bodies of talc-carbonate rocks framing the hyperbasite massif (Fig. 3). Ore formation occurred by replacing blocks of hyperbasites and talc-carbonate rocks with sulfide material. 33 bodies of massive sulfides with a thickness of 0.2-5.5 m, composed of pyrrhotite, pyrite, and chalcopyrite with an admixture of chromite and minerals Co, Ni,and As are outlined in the roof of the eastern zone. Near the surface, sulfide ores are replaced by oxidized ones - malachite-azurite and malachite-goethite, which are most pronounced in talc-carbonate rocks.

The deposit has eight ancient quarries with a diameter of 20-80 m and a depth of up to 20 m, from which oxidized copper ore was extracted (Zaikov et al., 2009, pp. 27-37). 3, except for quarry No. 5, located in the southern part of the ore field, 500 m south of the settlement of Ishkinovka.

In terms of shape, they are divided into "pear - shaped" - distinctly elongated - and more isometric-almost round and oval. The first (N 1,6) are linear workings with a length of 40-80 m with a predominant depth of 6-7 m, passed through steeply falling ore bodies. The second ones (N 2 - 4, 7, 8) with a diameter of 15 - 100 m and a depth of 3 - 10 m developed shallow-lying ore bodies. In addition, there were two vertical workings (N 9, 10), in which sulfide ores were extracted. Ore dressing, judging by the presence of crushed stone of malachite-bearing rocks, occurred on a flat area (N 11) in the northern part of the ore field.

3. Layout of ancient quarries, ore-bearing zones, and mine workings at the Ishkininskoye field (Zaikov et al., 2009, p. 34). 1 - hyperbasites; 2-volcanomictic breccias; 3 - contours of ore-bearing zones with accompanying talc-carbonate rocks; 4 - sites of ore drift sampling; 5 - excavated trenches completed in 2001; 6 - contours of ancient quarries; 7 - vertical ancient workings; 8 - proposed processing site; 9 - sites of mining operations. location of individual gold grains; 10 - Gai-d highway. Ishkinino.

4. General view from the north of the Ishkininsky pit No. 1, opened by a trench, photo 2001.

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5. Diagram of the structure of the eastern part of the open pit dump No. 1 of the Ishkininsky field. 1, 2-lower horizon: 1-ore warehouse N 1 with azurite-malachite ores, 2-crushed talc-carbonate rocks; 3 - 8-middle horizon: 3-ore warehouse N 2 with malachite-goethite ores, 4-crushed brown ironstone, 5-crushed talc-carbonate rocks, 6-storage of talc raw materials, 7-ash pits, 8 - location of anvils; 9-upper horizon: dark brown loam with crushed talc-carbonate rocks; 10, 11-soils: 10-buried, 11 - modern soil and vegetation layer.

The largest open pit No. 1 (Fig. 4) is extended in the meridional direction according to the orientation of the eastern ore zone. Its length is 120 m, maximum width is approx. 40, depth is more than 5 m. On the bottom there are three swollen dumps, which were poured on top of each other as the quarry was being worked out in the direction from south to north. The height of the largest of them is approx. 5 m.

The upper part of the northern dump is excavated to a depth of 4 m by trench No. 3. The dump is composed of gravelly-gravelly material, the layers of which lie in a curtain pattern (Fig. 5). The section of the dump deposits includes three horizons that differ both in the mineralogical and petrographic features of the material composing them and in the size of the fragments. The lower and middle horizons are separated by buried soils, which indicates long breaks in the development of the mine.

In the lower horizon, at a depth of 2.0 - 2.5 m, a lens composed of pieces of copper ore of azurite-malachite composition, their size is up to 15 cm across, is found. This cluster is an ore warehouse (N 1), i.e. a special place for storing the most valuable raw materials after its extraction and pre-enrichment. The apparent thickness of the lens is 0.6 m, the length is 4 m. The lens is covered with a layer of ancient buried soil. In the middle horizon at a depth of 0.75-1.0 m in the central part of the trench, another ore deposit (N 2) was found in the form of a subhorizontal lens with a length of 4.5 m and a maximum thickness of 0.75 m. It is provided with crushed goethite (brown ironstone) with inclusions, films and thin veins of malachite. The content of copper and arsenic in the ore is 2-3 times lower than in the ore from warehouse No. 1. The upper horizon consists of several curtain-like layers of grayish-brown loam containing sparse gravel and small crushed serpentinites.

The deepest quarry (N 6) is located in the western zone. It is embedded in the north-eastern slope of the stone ridge, extended in a meridional direction according to the orientation of the ore zone. A quarry consists of a series of workings connected to each other and separated by dumps. Total length approx. 60 m, maximum width up to 25 m, modern depth 2 - 3 m. Crescent-shaped dumps are filled out along the north and north-west sides of the quarry. Their current height is 0.5-2.5 m, the width of the sole in some cases reaches 20 m. The dumps are composed of gravel-gravelly material, the layers of which lie in a curtain-like pattern. On the surface of the dump of this quarry, an ore crushing stone was found, which was used in the process of preliminary dry enrichment.

According to A.D. Poluektov (Zaikov et al., 2009, p. 35), one of the deep pits drilled in the southern part of quarry No. 6 revealed an ancient mine (No. 9) at a depth of 20 m. This mine produced sulfide ores, and possibly gold-bearing rocks. Signs of gold mineralization in the form of gold grains were noted by A. M. Yuminov (Yuminov and Zaikov, 2002) on the southern flank of the western ore-bearing zone.

A vertical mine (N 10), which also opens up sulfide ores, was discovered by trench N 1. In the western part of the trench, among veined and interspersed sulfide ores, there is a notch with a depth of more than 4 m and a width of 1-4 m, filled with crushed limonitized rocks with secondary copper minerals.

The location of the processing site is tentatively planned in a depression between the northern flanks of the western and eastern zones, on a section measuring 60x100 m (N 11). Numerous small fragments of malachite-bearing ores that are not associated with bedrock are found here. Within the geologic limit

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a stone hammer with a groove for tying the handle was found in the pit laid in the northern part of the production processing site.

Age of workings

Analysis of the results obtained allows us to conclude that the described ancient workings belong to the Bronze Age. This is evidenced by stone hammers, ore-crushing stones, and anvils found in their dumps, which are identical to those found in dozens of other ancient mines in the Ural-Mugodzhar region (Tkachev, 2005; 2011a, Fig. 4, 6). This conclusion is confirmed by the presence of ore fragments, metallurgical slags, stone terochny slabs,etc. in the materials of the ancient settlement of Ishkinovka. pestles, hammers, blanks of mining and tunneling bone wedges.

The results of palynological studies and radiocarbon dating of buried soils preserved under the dumps of ancient quarries indicate a long period of operation of the Ishkininsky deposit, during which changes in vegetation cover and climatic conditions were noted. In particular, calibrated radiocarbon dates (68.2% probability) obtained at the Institute of Chemical Research of the Russian Academy of Sciences for buried soils from the dumps of three quarries (N 6 - 8) allowed us to identify a confidence interval in the range of 3100-2400 years BC (58.8%) (definitions of G. I. Zaitseva, P. F. Kuznetsov), which corresponds to the early Bronze Age. However, the results of radiocarbon dating of buried soils often show an aging trend compared to 14C dates obtained from other materials. The exploitation of quarries could have been resumed by the bearers of the Alakul culture in the late Bronze Age. The absolute age was determined from the bones of animals from the cultural layer of the settlement of Ishkinovka - 1610-1210 years BC (68.2% probability). It is close to the definitions obtained for the Gorny settlement in the Kargalinsky archaeological microdistrict - 1700-1500 years BC (Chernykh et al., 2002, pp. 125-128). These data are in good agreement with the results of palynological studies performed in the Laboratory of Natural Science Methods of the IA RAS by A. S. Aleshinskaya, M. D. Kachanova, and E. A. Spiridonova. Two palynological complexes were identified in the buried soils of the studied ancient quarries, which allow us to attribute the soils to different stages of the Bronze Age and note gradual climate changes from a fairly humid one in the early Bronze Age to a drier one in the late One. It is noteworthy that during geoarchaeological surveys, two stages of formation of dumps of the largest open pit No. 1 were also recorded [Zaykov et al., 2005, p. 107].

Ore composition

The deposit has revealed primary sulfide ores and their oxidized differences, which are dominated by copper carbonates. The main minerals of primary sulfide ores are*: chalcopyrite-CuFeS 2, pyrrhotite-Fe 1-xs, pyrite-FeS 2, cobaltine-CoAsS, pentlandite - (Fe, Ni)9S8, arsenopyrite-FeAsS, chromite-FeCr 2O4.

Sulfide ores are composed of massive and veined-interspersed differences [Zaikov et al., 2009, pp. 171-217]. The former belong to three mineral types: pyrite-pyrrhotite, chalcopyrite-pyrite-pyrrhotite, and cobaltine-chalcopyrite. The content of Cu 0.5-5.1%, Co 0.01 - 0.05, Ni 0.2 - 0.4, As 0.1 - 4.7% is established in pyrite - pyrrhotite ores; chalcopyrite-pyrite-pyrrhotite ores are characterized by a high concentration of copper-6.4-10.0%; in cobaltine-chalcopyrite ores, which contain an admixture of arsenopyrite, the content increases sharply arsenic and cobalt - respectively 8.1-9.3 and 0.1 - 0.7%. Veined-interspersed differences have pyrite-pentlandite-pyrrhotite and chalcopyrite compositions (Cu content 0.5 - 2.0%, Co content 0.01 - 0.12%, Ni content 0.2 - 0.5%). Octahedral chromite crystals (Cr - 0.1 - 0.5%) are recorded in all varieties of sulfide ores, which indicates their formation on a hyperbasite substrate. This is also indicated by the increased nickel content.

The main minerals of oxidized ores are: malachite-Cu2 (OH)2[CO3], azurite - Cu3(OH) 2[CO3] 2, cuprite-Cu2o, goethite-α FeOOH. Relict minerals include chromite. The oxidized ores contain azurite-malachite and malachite-goethite differences. The former are characterized by an increased copper content (6-8%), arsenic is also present (1.1%). Malachite-goethite ores are composed of goethite with veins and nests of malachite. The average content of copper in them is 2.6%, arsenic-0.6, nickel - 0.2%. Azurite-malachite ores were extracted by ancient miners at the first stage of the deposit's operation. Mining was carried out in the south-eastern part of open pit No. 1, where the oxidation zone of primary sulfide ores was located. After a break in mining operations, during which a layer of soil with a thickness of 20 - 30 cm was formed, mining operations resumed. During this period, malachite-goethite ores formed by interspersed sulfide varieties were mainly mined.

According to our calculations, the Ishkininsky mine produced approx. 30 thousand tons of copper ore, from which about 750 tons of copper could be obtained.

* Here and further, mineral formulas are given according to the monograph of A. A. Godovikov [1983].

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Composition of slags and chromites

Let us compare the composition of chromites from slags of oxidized and sulfide ores and host rocks. For this purpose, according to chemical analysis, the types of chromites are distinguished by the main parameter-the Cr2o3 content. The boundaries are determined using a histogram made up in 0.5% increments. As a result, it was found that chromites form three groups with a Cr2o3 content of 47-50%, 50-55%, and 55-61%. Slags from the cultural layer of the settlement of Ishkinovka are represented by fragments of semi-crystallized glassy mass of brown color with copper crowns. It contains crystals of pyroxene, olivine, and magnetite formed from the melt, as well as fragments of chromite grains that are relics of the ores used. Chromite grains are hypidiomorphic or have a rounded shape, and some contain molten silicate inclusions of several microns in size.

Copper crowns range in size from 10 microns to 4 mm. Small ones contain 97% copper and 2.4% iron. The larger ones consist of similar ferrous copper, copper sulfide and iron (Cu-64%, Fe-12, 5-23%). There are also small worm-like precipitates of iron phosphide with an admixture of nickel (Fe-88%, P-10, Ni-1.5%). The crown periphery is formed by a thin (5-10 microns) border of copper sulfide (Cu-80%, Fe-1.5, S - 18.4%).

In some samples, inclusions of melted copper ores with a size of 0.1 - 2.0 mm were detected. They are based on copper-containing glass of two different compositions: 1) Cu - 47 - 53%; 2) Cu - 2,0%, Cr - 0,6, V2O5 - 0,5%. In the last difference, there are the smallest (several micrometers) copper precipitates with an admixture of iron (Cu-99%, Fe-1%).

17 chromite grains were identified and studied in six slag samples. Grains have a size of 0.1-0.6 mm, and their shape is either determined by the faces of the octahedron, or rounded and comminuted (Fig. In slags, chromites are distributed evenly. Most grains (N 1, 2, 4, 8, 9, 11, 14 - 17) They contain CR2O3 48.6-52.3%, Al2o3 13.8-18.6, MgO 8.6-12.7, FeO 18.2 - 24.3% (Table 1). A third of the grains belong to Type II and III and has, respectively, a Cr2o3 content of 53-56 and 59-60%.

The oxidized ores are composed of concentrically zonal aggregates of malachite (Fig. 6, 2). Chromites are observed in them as single crystals or their aggregates (Fig. 6, 3). The host medium is oxide-

6. Photos of slags and ores of the Ishkininsky archaeological microdistrict (reflected light). 1-slag with inclusions of chromite (Cr) and copper crown (Cu), model Ish-1; 2-malachite (Ma) - goethite (Gt) ore of kidney-shaped texture, model T3-A; 3 - coalescence of chromite (Cr) crystals in goethite; 4-chromite (Cr) inclusions in massive chalcopyrite-pyrrhotite ore.

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Table 1. Composition of chromites from slags of the Ishkininsky archaeological microdistrict

Sample number

Grain Number

Number of tests

Composition Group

Content,%

Cr2O3

Al2O3

MgO

FeO

MnO

TiO2

The amount

lsh-1

1

4

I

49,39

18,55

12,26

19,69

-

0,09

99,97

2

3

I

49,27

18,56

11,95

19,95

-

0,12

99,84

3

1

III

57,13

9,27

8,38

24,97

-

0,18

99,94

4

1

II

50,71

17,50

12,49

19,17

-

0,18

100,05

5

5

III

60,42

9,00

10,92

19,50

-

0,08

99,92

6

3

III

55,95

12,20

10,30

21,44

-

0,07

99,95

lsh-A2 - 1

7

6

III

60,02

8,32

7,91

22,41

0,04

0,11

98,85

lsh-A2 - 3-1

8

6

II

52,31

15,01

9,02

22,44

0,02

0,10

98,90

9

6

I

49,25

19,43

12,70

17,24

-

0,17

98,78

lsh-A2 - 3-2

10

6

II

53,30

16,50

11,31

18,24

-

0,07

99,43

11

6

II

52,01

14,43

8,10

24,12

0,07

0,10

98,96

lsh-A2 - 3-3

12

6

III

59,78

9,46

9,13

20,55

0,09

0,12

99,13

13

6

II

53,78

15,50

12,09

17,58

-

0,08

99,03

KV-1

14

6

I

48,64

16,98

10,24

22,37

-

0,30

98,52

15

6

I

49,30

15,48

8,74

24,31

-

0,21

98,04

16

5

I

49,35

15,37

8,64

25,44

0,05

0,20

99,07

17

4

I

50,09

13,79

8,56

25,54

0,06

0,20

98,25

Notes: 1) groups of compositions determined by the histogram: I-45-50%, II-50-55, III-55-61%; 2) analysis of the Ish-1 sample was performed on an X-ray spectral microanalyzer SEMMA 202M (analyst V. A. Kotlyarov), the rest-on a JEOL-733 microprobe analyzer (analyst E. V. Kotlyarov). I. Churin); 3) material from the excavations of V. V. Tkachev.

carbonated and calcined rocks are considered to be the main types of mineral ores. Sulfide ores are characterized by a greater variety of chromite morphology, which forms single crystals and clusters intersected by sulfides (Figs. 6, 4), which clearly indicates the inheritance of chromites from hyperbasites and the later formation of copper sulfide ores.

When comparing chromites from slags, malachite-containing ores, and talc-carbonate rocks containing the latter (Tables 1 and 2), first of all, a wide variety of their composition is noteworthy, covering the range of 44-61% Cr2o3. There are three groups of slags: 47-50%, 50-55%, and 59-61%. It is close to chromites from oxidized ores and host talc-carbonate rocks. Sulfide ores differ from oxidized ores by a narrow range of Cr2o3 concentrations (49-52%) in chromites (Zaikov et al., 2009, pp. 244-248). The reason for the diversity of the composition of the studied mineral is probably that the ores were formed in the tectonic zone of the Main Ural Fault, where as a result of displacements, hyperbasite blocks of different compositions were combined. They contained chromite of various compositions.

Until now, no special attention has been paid to chromite inclusions in ancient slags; their descriptions are known from two publications (Grigoriev, Dunaev, and Zaykov, 2005; Zaykov et al., 2005, p. 111-113). The presence of chromites in copper ores from Cyprus is mentioned (Zwicker, 1990). We should expect to detect such inclusions in the slags of ore regions where copper ore of the Ishkininskaya type was used.

In the Southern Urals, hyperbasites with accessory chromite are distributed as separate bodies and linear groups of massifs almost everywhere east of the Main Ural Fault. Chromite inclusions were found in slags from eight settlements (see Figure 1). Preliminary mineralogical and geochemical studies have shown that chromites in the slags of the southern group of archaeological sites (from Ishkinovka to Arkaim) are close to each other. In the slags of the northern group of settlements (Kuysak, Kamenny Ambar, Ustye), they are characterized by an increased concentration of zinc (0.2-1.3% ZnO) and the presence of differences with a Cr2o3 content of 38-42%. Accordingly, these monuments had a different source of ores, for the establishment of which it is necessary to continue studying chromites from slags in all settlements,

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Table 2. Composition of chromites from oxidized copper ores and ore-bearing talc-carbonate rocks of the Ishkininsky archaeological microdistrict

Sample number

Grain Number

Number of tests

Composition Group

Content,%

Cr2O3

Al2O3

MgO

EFeO

MnO

TiO2

V2O5

The amount

Azurite-malachite ores

T3

1

3

50,49

15,31

10,63

23,40

0,37

0,27

-

100,46

2

3

47,81

15,31

9,35

27,45

0,42

0,33

-

100,67

3

3

46,49

17,60

9,21

26,17

0,43

0,31

-

100,20

4

3

48,39

15,92

9,83

24,65

0,40

0,29

-

99,48

5

3

50,22

14,27

9,89

23,97

0,41

0,29

-

99,06

T3a

6

3

II

53,66

14,52

10,95

21,77

-

0,00

-

100,91

7

4

II

50,95

14,16

8,70

26,18

-

-

-

100,00

8

6

II

52,81

12,43

8,57

25,50

-

-

-

99,30

T3-2-1

9

2

II

56,57

11,01

9,84

21,51

0,49

0,14

-

99,56

T3-2-2

10

9

50,92

13,29

8,66

25,97

0,33

0,30

-

99,47

T3-2-3

11

5

51,63

13,65

9,56

24,88

0,28

0,29

-

100,30

Malachite-goethite ores

T3-3-1

12

6

51,07

13,36

7,17

27,27

0,52

0,53

-

99,92

T3-3-2

13

9

46,75

14,51

7,12

28,89

0,81

0,97

0,88

97,63

T3-3 - 3

14

3

48,98

13,76

7,76

27,61

0,79

0,99

-

99,89

T3-3-4

15

3

51,79

12,49

8,20

26,24

0,75

0,50

-

99,97

T3-3-5

16

6

47,75

14,6

8,31

27,07

0,85

0,93

0,40

99,91

6a

22

6

III

59,52

11,58

12,84

15,53

0,49

-

-

99,96

7a

23

8

III

61,37

9,74

12,68

15,64

0,46

0,04

-

99,94

8a

24

4

III

59,47

10,68

12,69

16,33

0,40

-

-

99,57

9a

25

4

II

54,09

9,94

9,31

25,95

0,36

-

-

99,97

Ore-bearing talc-carbonate rocks

1a

17

4

I

50,08

13,64

10,48

24,34

0,37

0,15

0,30

99,68

2a

18

8

II

52,51

9,69

8,35

27,56

0,39

0,29

0,24

99,40

3a

19

3

II

52,27

12,41

9,76

25,17

0,22

0,29

0,04

100,27

4a

20

7

II

53,68

10,72

9,23

26,12

0,21

0,23

-

100,36

5a

21

6

III

59,42

11,39

12,63

16,16

0,87

-

-

100,47

Notes: 1) analysis of samples T3-2-1, T3-3-1, T3-3-2, T3-3-3, T3-3-4, T3-3-3-5 They were performed on a SEMMA 202M X-ray spectral microanalyzer, while the rest were performed on a JEOL-733 microprobe analyzer; 2) collection A. M. Yuminova.

where they are found, and in the ores of ancient mines using modern microprobe and X-ray equipment.

Conclusions

1. In the Ishkininsky archaeological microdistrict in the Bronze Age, there were mines for the extraction of copper ores. Based on the study of their dumps, two stages of development were established, in the interval between which buried soils were formed.

Preliminary data indicate the extraction of ores in the early (3100 - 2400 BC) and late (1610 - 1210 BC) Bronze Age.

2. The analysis of copper ores showed that they belong to varieties formed from various hyperbasites, as evidenced by chromite inclusions and an increased nickel content.

3. A comparison of the composition of chromites from ores and slags revealed their identity, which clearly indicates that paleometallurgists used the ores of the Ishkininsky deposit.

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4. The presence of copper sulfides, as well as iron phosphides with a high nickel content, has been established in the copper crowns of slags. This fact supports the conclusion about the beginning of the use of copper sulfide ores in the Urals in the Bronze Age.

5. Geochemical and mineralogical criteria for the use of copper ores associated with hyperbasites are determined, which is relevant for establishing the mineral resource base of ancient societies.

6. An important task of further research is to identify chromite-containing slags on the monuments of the region and analyze chromites to determine specific sources of copper ores for various settlements.

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The article was submitted to the editorial Board on 14.02.11, in the final version-on 16.06.11.

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