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Au-Ag-telluride Deposits of the Golden Quadrilateral, Apuseni Mts., Romania .... jamesonite) with the gold-bearing base-metal ores that typify lower parts of the ...
N.J. Cook & C.L. Ciobanu (Eds.), 2004 Au-Ag-telluride Deposits of the Golden Quadrilateral, Apuseni Mts., Romania Guidebook of the International Field Workshop of IGCP project 486, Alba Iulia, Romania, 31 August –7 September 2004 IAGOD Guidebook Series 12, pp. 111-144.

7. TELLURIDES AND SULPHOSALTS FROM DEPOSITS IN THE GOLDEN QUADRILATERAL Nigel J. Cook1,2, Cristiana L. Ciobanu2, Gheorghe Damian3, Floarea Damian3 1

Geological Museum, University of Oslo, Postboks 1172 Blindern, N-0318 Oslo, Norway 2 3

Geological Survey of Norway, N-7491 Trondheim, Norway

Universitatea de Nord, Str. V. Babe 62/A, RO-4800 Baia Mare, Romania

Abstract: There are currently 19 known occurrences of tellurides in the Golden Quadrilateral of the South Apuseni Mountains. These range in scale from 'classic' telluride rich deposits such as S c rîmb, to more modest and relatively minor occurrences, which are nevertheless growing in number as investigations become increasingly detailed. Each of these is briefly described, and each telluride species reported from the district is discussed with reference to occurrence, association and mineral chemistry.

Introduction There is probably no other ore province in the world that, prior to mining, contained as much gold occurring primarily as tellurides. Particularly between 1750 and 1914, several of the vein gold deposits of the Golden Quadrilateral (GQ) delivered high-grade gold ore containing abundant, and in the case of S c rîmb, dominant tellurides. Accordingly, the ore deposits of the GQ have, since the early days of mineralogy in the 18th and 19th centuries, been one of the most productive provinces in Europe for the discovery of new minerals. More than half the known gold- and silvertellurides have their type localities here. Among mineral enthusiasts and museum curators, deposits such as S c rîmb, St nija, Baia de Arie and Bote have become synonymous with spectacular and valuable specimens of a quality unrivalled anywhere else in the world (Fig. 1). In contrast, the sulphosalts from GQ deposits are rather poorly represented in museum specimens. The richest sulphosalt veins are known from the Cîrnic and Cîrnicel vein systems at Ro ia Montana, the only district lacking historical recognition of tellurides. However, Pb-Sb-As, Ag-Sb-As and to lesser extent Bi-sulphosalts are included in the mineralogical inventories of many of the 64 deposits and prospects in the GQ. Although many vein provinces worldwide are recognized for their rich and diverse sulphosalt assemblages, these tend to be base metal- (e.g., Baia Mare, Western Carpathians, Erzgebirge), Ag- (Guanajuato, Mexico), or Sn- (Bolivia) provinces rather than Au provinces. It is therefore of particular interest to characterize the distribution, speciation and assemblages of sulphosalts in the GQ. Relationships between different groups of sulphosalts, as well as between sulphosalts and tellurides, may provide valuable information to trace mineralising trends within a deposit, district or province. The history and development of ore mineralogy in Romania is closely linked to discovery and exploitation of the deposits of the GQ. The early identification and description of telluride minerals by many of the most famous mineralogists of the late 18th and 19th centuries (several of which lent

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their names to the newly-discovered tellurides), gave way to a second 'golden' age for the science in the inter-war years, during which numerous ore mineralogical descriptions (e.g., by Ghi ulescu, Giu c , Helke and Petrulian) helped place the telluride-rich assemblages into the context of regional metallogeny. This basis (including detailed description of mine workings by Ghi ulescu and Socolescu, 1941) allowed successive workers in the 1960's, 70's and '80's (led by Berbeleac, Cioflica, Borco and many others) to develop integrated models for the GQ.

Fig. 1. Specimens of tellurides and native elements from the Golden Quadrilateral. All are in the 'Gold Museum', Brad, with the kind permission of Grigore Verde . (a) and (b) Sylvanite from Baia de Arie , (c) and (d) Nagyágite from S c rîmb, (e) and (f) Hessite from Bote , (g) Native tellurium from Fa a B ii (Zlatna), (h) Native arsenic from Musariu1.

1

In Filonul Negru (the Black Vein) at Musariu, Cioflica et al. (1999) quote the presence of gold and arsenopyrite as inclusions in native arsenic with collomorph textures.

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The high-grade telluride ores were mainly derived from the upper part of the deposits. As these became worked out, fewer spectacular finds were made, and today, discovery of macroscopic tellurides in the open pits and underground stopes is rare. At the same time, application of modern investigative techniques, on older material located in museum collections in Romania, around Europe and the world2, and also directed towards the micro-scale mineralogical characterisation of ores being worked today, is giving rise to a third 'golden age' for mineralogical discovery in the province3, fuelled by the continued fascination of those fortunate to work in the area. This trend is set to continue in the future, spurred also by the requirements of industry to have a greater control of ore mineralogy to successfully exploit ores of lower grade. Despite the historical importance of tellurides, their major contribution to the economic development of the district in the modern era, and a comprehensive volume of literature devoted to them (see, for example, Ianovici et al., 1969, 1976)4, few modern studies have specifically addressed the role of the telluride associations within the overall picture of hydrothermal mineralisation in the district. This deficiency is in contrast to the modern description and modelling of telluride-bearing systems in other important gold provinces worldwide in which tellurides are an important part of the ore assemblage and where Au-tellurides may account for a significant volume of the gold, e.g., Emperor, Fiji (Ahmad et al., 1987; Pals and Spry, 2003), Golden Mile, Kalgoorlie, Western Australia (Shackleton et al., 2003); Montana, U.S.A. (Spry et al., 1997), Altaid belts of Uzbekistan (e.g., Kovalenker et al. 1997, 2003). This contribution reviews the distribution and paragenesis of telluride and sulphosalt minerals in the GQ, incorporating new, published data up until 2004. The new developments are important given the current need to understand and interpret telluride paragenesis as part of an overall appreciation of metallogeny and ore formation in the Golden Quadrilateral, and to allow comparison with other Au-Ag-telluride districts worldwide. Furthermore, given the coexistence of several Au-Ag-telluride species and also their relationships with other tellurides as reported in many of the recent studies, sample material from GQ deposits is invaluable in terms of understanding phase stability for minerals within this group. Distribution and speciation of tellurides in deposits of the GQ Of the several deposits in the GQ known for abundant and/or spectacular samples of tellurides (at the macroscopic scale), the best example is S c rîmb where Au-Ag-tellurides formed the main, and in some parts of the veins the only, gold ore. In S c rîmb, as in other Au-Te deposits worldwide (e.g., Emperor; Pals and Spry, 2003), tellurides provided as much as 50 % of the total gold exploited Au (Ghi ulescu and Socolescu, 1941; Uduba a et al., 1992a). Although generally less abundant, similar macroscopic telluride-rich assemblages have been found in a number of deposits spread throughout the entire province, e.g., St nija, Fa a B ii, Br di or, Musariu, Baia de Arie , Bote , Bucium-Arama, M gura ebei. Despite the really rather limited number of macroscopictelluride occurrences with respect to the total number of deposits in the district (Fig. 2), the presence of exceptional telluride-rich veins (e.g., sylvanite vein, Baia de Arie ), or spectacularly coarse 2

Spectacular collections of telluride-rich samples from the GQ can be found in the following museums in Romania: the 'Gold museum', Brad, in the collection of Babe -Bolyai University, Cluj-Napoca and the Brukenthal Museum, Sibiu. Further specimens can also be found in the National Mineralogical Museum, Bucharest and in the 'Giu c ' and 'Petrulian' collections of the Department of Mineralogy, Bucharest. Brief descriptions and contact details are given in Szakáll (2002). Notable collections outside Romania include the Naturhistorisches Museum, Vienna and the Natural History Museum in Budapest.

3

Also including new discoveries and confirmations of secondary minerals in old mine galleries (e.g., Onac et al., 2003).

4

Other more generalised reference sources on the mineralogy of the GQ include R dulescu and Dimitrescu (1966), Huber and Huber (1983), Uduba a et al. (1992a, b) and Szakáll (2002). Zepharovich (1859, 1873, 1893) is a valuable early secondary reference. Papp (1997) provides authoritative data on early mineral discoveries.

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telluride samples (e.g., hessite from Bote ), stresses further the Au-Te character of epithermal mineralisation throughout the entire GQ.

Fig. 2. Geological map of the Golden Quadrilateral (yellow dashed line), simplified from Fig. 2 in Ciobanu et al. (this volume, a), showing the location of the nineteen currently known telluride occurrences (yellow circles). Note that earlier authors had defined the Golden Quadrilateral as a smaller area, not including deposits at Deva and in the Zarand Mts.

Underlying the above is not only the fact that the number of documented telluride occurrences is increasing (currently 19; see below), but also the fact that the presence of tellurides are confirmed from the upper to the deeper parts of deposits, and also straddling various types of mineralisation (e.g., veins, skarn and porphyry in Larga-Fa a B ii-Trîmpoiele; Cook and Ciobanu, 2004). These observations are in contrast to previous beliefs in which development of tellurides was considered restricted to the transition between the uppermost gold-only ores (± stibnite, native arsenic, jamesonite) with the gold-bearing base-metal ores that typify lower parts of the veins (e.g., Ianovici et al., 1969, 1976, Berbeleac et al., 1995a).

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Investigation of samples from deposits previously considered devoid of tellurides is valuable evidence that, at the microscopic scale, tellurides and gold are present as inclusions in base metal sulphides in, e.g., the Ro ia Montan district (T ma et al., 2004; Ciobanu et al. this volume). Therefore one of the important questions to be addressed is whether the presence or absence of tellurides in a given deposit is only a matter of carrying out sufficiently detailed investigation. It appears that, in order to understand the link between gold and tellurides throughout the GQ, it is less important to find additional occurrences of tellurides than it is to constrain the genesis and evolution of gold-rich parts of deposits that lack tellurides. The GQ offers an entire spectrum of magmatic-hydrothermal types of deposits, with various styles of mineralisation represented. Although of dominantly low-sulphidation character, the fact that the few high sulphidation occurrences only carry few tellurides, if at all, is also a factor when considering the position of tellurides in the overall metallogenetic evolution of the district. Additionally, although several vein kin-porphyry systems that carry tellurides are known (e.g., Musariu Nou, Larga), other systems, e.g., S c rîmb, display no immediate relationships to porphyry mineralisation. The underlying reasons for the observed distribution and speciation of tellurides in individual deposits and throughout a given orefield is still an unsolved puzzle in the GQ. Macroscopic telluride associations have typically been found in veins from the upper levels (although not necessarily the uppermost levels) of certain deposits, particularly S c rîmb also less abundantly in others (St nija, Fa a B ii, Hondol, Br di or, Musariu, Baia de Arie , Bote etc.). It is impossible to give a general picture for the entire district, in which the styles of vertical mineralogical zonation differ from deposit to deposit and zones or mineralisation stages are missing, telescoped or superimposed. Nevertheless, the traditional picture has been of maximum development of tellurides at the transition between the uppermost gold-only ores (± stibnite, native arsenic, jamesonite) with the gold-bearing base-metal ores that typify lower parts of the veins. Tellurides are commonly preceded by or intergrown with tetrahedrite and other sulphosalts, particularly bournonite. In the classical, formalistic understanding of the deposits (e.g., in publications by Petrulian, 1934; Helke, 1934; Giu c 1935, 1936a, b; Borco et al., 1964; Cioflica et al., 1973, and numerous others), the 'telluride-sulphosalt' stage is the third of four stages, after the iron-sulphur and basemetal stages, but preceding the gold stage. Ianovici et al. (1969) summarise the mineral succession and zoning patterns in many deposits of the district and expand the paragenetic approach to describe no less than 24 type associations across the district, which can be used as a basis both for deposit classification and genetic modelling. The same publication also reproduces a number of diagrams (by Ghi ulescu, Borco and others), illustrating the spatial position of telluride assemblages in S c rîmb, Dealul Fericelii-St nija and Baia de Arie (see elsewhere in this volume). A more general description of the paragenesis and position of the telluride associations has been given by Berbeleac (1986), emphasising the vertical transition from the native-gold silver paragenesis (only observed in some deposits in the GQ, notably Ro ia Montan , Baia de Arie ) to the complex gold-silver telluride-base metal sulphides paragenesis, and further below to the base metal sulphide-gold-silver paragenesis. The subsequent sections give a brief description of the occurrence and distribution of tellurides in the 19 confirmed occurrences (S c rîmb, St nija-Fericeaua, St nija-Dealu Negru (vein Vilanela), Fa a B ii-Larga, Trîmpoiele, M gura-Hondol, Brad-Br di or, Brad-Musariu, Brad-Valea Morii, Baia de Arie , Bucium-Arama, Bote , M gura ebei, Cordurea-Cerburea, Ro ia Montan -Cetate and Ro ia Montan -Cîrnicel; Fig. 2; Table 1), largely based on descriptions by Ghi ulescu and Socolescu (1941) and Ianovici et al. (1969, 1976) later publications that have confirmed earlier observations, or added new data, and also our own observations.

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Trîmpoiele

Baia de Arie

Bote

Arama

Rosia Montana Cîrnicel

Fa a B ii – Larga (Horia level, 516 m)

X3,15

X2 ?6 X40

Rosia Montana- Cetate

St nija – Fericelii Hill

Caraci – M gura Tebei

St nija – Ungurului Hill (Vilaneli vein)

Brad (Valea Morii)

Brad (Br di or)

Brad (Musariu)

V li oara-Porcurea

Cordurea-Cerburea

Pîrîul lui Avram

Coranda-Hondol

M gura-Hondol

S c rîmb

Table 1 Telluride minerals reported from GQ deposits (Apuseni Mts., Romania).

Au-Ag tellurides Calaverite empressite AuTe hessite Ag2Te Kostovite CuAuTe4 Krennerite (Au,Ag)Te2 montbrayite Au2Te3 museumite muthmannite AuAgTe2 Nagyágite

X2,15,32 X6 1,16,17 X

X25 X25

?5 X1,2,3,8,9

X13 X35

X25

X27 X26,27 X26,27 X2

X38

X26,27 X27

X38

X45 X44

X41 X1,18

X2

X1

X2,37

X

X45

X42 X14,43

X28

X1,2,3,12,13,19-

X25

21,44

26,27

2

X

X2,37

X

petzite Ag3AuTe2 stützite Ag5-xTe3

X1, 310,11,16 X5,32

X13

X25

X26,27 X2 X27

Sylvanite (Au,Ag)Te2

X1,2,3,16,44

X13

X25

X2

X1 X1 X2

X38

X3,15

X2 X44 X40,44

X3,15 X2,40

X44 X1,18 X41 X1,18

X45 X2,3,7,3 7

Bi-tellurides aleksite PbBi2Te2S2 pilsenite Bi4Te3 rucklidgeite PbBi2Te4 tellurobismuthite Bi2Te3 tetradymite, Bi2Te2S tsumoite BiTe

X36 X33 X40 X23

X2

X2,15 X2,15

X40 X40 X40

Other tellurium-bearing minerals altaite, PbTe X1,3,16,17,22 cervelleite Ag4TeS coloradoite, HgTe X3,32 frohbergite FeTe2 X24 melonite NiTe X native tellurium, Te X2,17 tellurite, TeO2 X2 tellurantimony Sb2Te3 X35 Te-bearing argyrodite weissite, CuTe Unnamed SbTe2 Unnamed (Au,Ag)TeO2 X34 Unnamed (Ag,Au)2AsTe2 X44

X31

X26,27 X2

X38

X3

X2,40 X39 X44

X41 X44

X3,30 X27

X18

X2,37

X

X37 X24 X

X26,27 X2 X35

X2

X2 X2

X35 X44 X27 X29

Reference sources: 1: Ghi ulescu and Socolescu (1941); 2: Ianovici et al. (1969); 3: Cioflica et al. (1993); 4: R dulescu and Dimitrescu (1966); 5: Uduba a et al. (1992): 6: Schrauf (1878); 7: Neckar (1835); 8: vom Rath (1877); 9: Krenner (1877); 10: Petz (1842); 11: Haidinger (1845); 12 Werner (1789), Sipöcz 1885, Hankó 1886; 13: Giu c 1937; 14: Zambonini (1911); 15: Helke (1933); 16: Helke (1934); 17: Giu c (1935, 1936a, b); 18: Ghi ulescu and Giu c (1938); 19: Stumpfl (1970); 20: Uduba a et al. 1993; 21: Stanley et al. (1994) and Lupulescu (1994); 22: Koch and Krasselly (1950); 23: Socolescu et al. (1963); 24: Ramdohr and Uduba a (1973); 25: Berbeleac, 1975; Ianovici et al. (1976); 26: Berbeleac (1980); 27: Berbeleac and David (1982); 28: Spiridonov and Chileva (1985); 29: Cioflica et al. (1992); 30: Popescu and Constantinescu (1992); 31: Ioan et al. (1993); 32: Popescu and imon (1995); 33: imon and Alderton (1995a); 34: imon and Alderton (1995b); 35: Popescu and imon (1992) and imon et al. (1995); 36: Shimizu et al. (1999); 37: Cioflica et al. (1999); 38: Jude (1998, 2000); 39: Cook and Ciobanu (2003); 40: Cook and Ciobanu (2004); 41: T ma et al. (2004); 42: Bindi and Cipriani (2004a); 43: Bindi and Cipriani (2004b); 44: this work.; 45: Cabri (1965). Type localities are indicated with bold crosses.

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Telluride occurrences in vein deposits S c rîmb S c rîmb is unique among the deposits of the GQ with respect to the abundance of telluride minerals. It is the type locality for nagyágite (Figs. 1c, d), krennerite, petzite, stützite, muthmannite and museumite. Based on earlier data and mining records, Ghi ulescu and Socolescu (1941) described distinct mineral associations in different parts of the S c rîmb deposit5 (see Ciobanu et al., this volume a, b). Veins of the Magdalena field in the SE part of the orefield, between 335 and 784 m (Maria and Nicolae galleries) typify the nagyágite association. The Magdalena vein exceeds 400 m in height and a similar length. Lesser parallel and transversal veins include Adam, Daniel, Weisse, Liegend, Carolina, Emilia, Antoniu, Cartausi, and at upper levels, Felicia, Aloïsi, Clement, Ferdinand, Wettertur, Wiedersenische etc. In this part of the deposit, gold occurs nearly exclusively as nagyágite, together with base metal sulphides (pyrite, galena, sphalerite, chalcopyrite and occasional alabandite) in a matrix of quartz, rhodochrosite and rare calcite. Veins of the Longhin-Antilonghin group to the north are numerous. The Antilonghin vein extends more than 450 m vertically beneath the Ferdinand gallery. Individual veins vary in width from a few cm up to more than 2 m. Geodes are abundant within the veins. A similar base metal assemblage as in the Magdalena field is observed, with gold chiefly as sylvanite, native gold and krennerite, rarely as nagyágite. Gangue minerals are quartz, barite, rhodochrosite and rare calcite. The less important Nepomuc field, to the west of the above, consists of veins similar to the Antilonghin type, but with appreciably more calcite, and gold occurring chiefly as petzite. More than 230 veins are known from S c rîmb, with an average width of 30 cm. The veins reached their greatest extent between the Carol and Ferdinand levels, becoming thinner and lower grade at lower levels. Beneath the level of the Nicolae gallery, they become sparse, the grade is subeconomic and tellurides are virtually absent. The clear distinction between different parts of the S c rîmb deposit has generally been interpreted as resulting from non-synchronous vein generation. Because so much ore had already been removed when modern era metallogenetic and ore mineralogical studies began in the 1930's (by Helke, Giu c , Petrulian and others), it is not entirely clear if the mineralogical zoning is more generalised than real. The tendency for formation of base metal sulphides, followed by tellurides and then sulphosalts can be seen in the publications of these authors (e.g., Helke, 1934; Giu c , 1935). A common paragenetic scheme for the S c rîmb deposit (Ianovici et al., 1969, p. 650) suggests the following sequence of telluride deposition: krennerite-sylvanite-nagyágite-altaite-tetradymitehessite-petzite-native tellurium. However, decomposition, replacement and recrystallisation have all been observed. In the presence of Pb or Bi minerals, the Ag/Au ratio tends to increase. Tetrahedrite and other subordinate sulphosalts occur. Goldfieldite is known from upper levels, closely associated with tellurides. A more detailed description of telluride assemblages at S c rîmb can be found in Ciobanu et al., this volume, b. Coranda-Hondol ('Certej' deposit) Although gold is chiefly present as electrum, some minor Au- and Ag-tellurides, as well as sulphosalts, are known from veins and impregnations in the Coranda quarry, to the immediate northwest of S c rîmb (e.g., Ionescu and T ma , 2003). A preliminary identification of kostovite was made by Uduba a (1981, unpubl., mentioned in Uduba a et al. 1992b).

5

A brief historical summary of the S c rîmb deposit has recently been given by Uduba a (2001).

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M gura-Hondol Located in the westernmost part of the S c rîmb sub-district, the M gura-Hondol deposit (see Fig. 8 in Ciobanu et al., this volume, a) was relatively recently also demonstrated to contain tellurides. Ioan et al. (1993) report krennerite, sylvanite, petzite and tellurantimony (M gura, Ludovica, Vîna Neagr , Florian, Francisca, Eleonora, Rudolf veins; see also Orlandea and Velciov, 1996). imon et al. (1995), in their more detailed description of tellurantimony, also mention the presence of altaite and montbrayite from M gura-Hondol. The tellurides occur in open vugs and represent a 'late mineralisation stage'. Brad district (Musariu, Br di or, Valea Morii) There are three confirmed occurrences of tellurides in the celebrated Brad district, perhaps the most productive area of the entire GQ in terms of gold mining. The Musariu (Nou) vein deposit, (see Ciobanu et al., this volume, a) at the upper part of a porphyry system, is synonymous with the spectacular specimens of native gold, now housed in the 'Gold Museum' in Brad. The occurrence of native tellurium and a range of tellurides (sylvanite, calaverite, nagyágite, petzite, hessite, empressite, montbrayite, frohbergite, weissite, altaite, stützite, tellurite) comes from "a vein neighbouring vein 44" and was a relatively recent discovery (Berbeleac, 1980; Berbeleac and David, 1982). The Br di or occurrence is within vein 25/37 and includes altaite, petzite, sylvanite, hessite, native tellurium and tetradymite (Ianovici et al., 1969). Ghi ulescu and Socolescu (1941) do not mention tellurides within vein 25/37, but refer to the occurrence of tellurium and bismuth minerals in Vein 41 in the same mine. Sylvanite has been recorded by Ianovici et al. (1969; figure 233) on a paragenetic scheme given for the Valea Morii deposit. No locality details are provided and we also note that Ghi ulescu and Socolescu (1941) do not mention tellurides from Valea Morii. Pîrîul lui Avram (Coasta Mare) Positioned within the Cetra volcanic structure (Ianovici et al., 1976; pp. 425-7), this small occurrence carries an assemblage untypical of GQ deposits, with a distinct high-sulphidation character (chalcocite-covellite-sphalerite-chalcopyrite-luzonite-stibioluzonite-famatinite-enargitestannite-bismuthinite-jamesonite-tennantite-argyrodite-galenobismuthite (Socolescu et al., 1963). Tetradymite is conspicuous among the minerals reported. Cordurea-Cerburea and V li oara-Porcurea NW-SE striking polymetallic veins at Cordurea (accessed by galleries Pavel, P tru, and Noroc Bun), host a mineralogically complex ore containing nagyágite, krennerite, sylvanite, hessite and petzite6. Sulphosalts, as well as bornite, enargite, famatinite, are noted (Berbeleac, 1975; Ianovici et al., 1976). The same sources indicate the presence of hessite from Curila vein (pîrîul erbanilor) and Volbura Cr i or, within the V li oara-Porcurea prospect. Caraci- ebea The westernmost reported occurrence of gold tellurides is from stockwork mineralisation accessed from Petru i Pavel gallery on the western flank of M gura ebei (Ghi ulescu and Socolescu, 1941). A contemporary description of this mineralisation and the telluride assemblage (sylvanite, krennerite, hessite, altaite) has been given by Jude (1998, 2000).

6

The occurrence is given in Berbeleac (1975) as from the Buna Vestire vein, Cordurea.

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St nija district Tellurides are known from two localities in the St nija district. The occurrence in the Vilanela vein (Popa-St nija - Ungurului Hill; Fig. 3) includes altaite (Ghi ulescu and Socolescu, 1941), petzite and tetradymite (Helke, 1933). The abundant altaite-galena intergrowths are of particular note.

Fig. 3. Simplified geological section of Ungurului Hill (Popa St nija deposit) redrawn after Ianovici et al. (1984). The veins are represented by red lines. Dashed lines are veins projected onto the section.

The second occurrence in Dealul Fericeaua (or Fericelii; Fig. 4) is within veins hosted by sedimentary rocks; the veins are related to an andesitic body at depth. These veins (accessed in the Ro ia and Acra gallery) are today more commonly referred to as Munc ceasca-St nija (or Munc ceasca West), rather than St nija.

Fig. 4. Simplified geological map (A) and section (B) of Dealul Fericeaua (St nija district), redrawn after Ianovici et al. (1969). The veins are represented by red lines.

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TELLURIDES AND SULPHOSALTS IN THE GOLDEN QUADRILATERAL

Several individual veins (Ro ia, Iolanda, Spoiala, Scara, Robotin, Haber) within the group host telluride mineralisation, with significant quantities of sylvanite and petzite locally lending the ore a high gold grade (Ghi ulescu and Socolescu, 1941). The telluride assemblage includes sylvanite, calaverite, hessite, petzite, stützite, tetradymite and native tellurium (Helke, 1933; Ghi ulescu and Socolescu, 1941). imon et al. (1995) observed the above telluride assemblage, as well as tellurantimony and frohbergite. Cioflica et al. (1992) earlier reported on unnamed SbTe2 from the same locality. Popescu and Constantinescu (1992) reported coloradoite in specimens from St nija. Fa a B ii -Larga The NW-SE striking Fa a B ii group of high-level veins is a prime example of high-grade gold mineralisation in which tellurides are present. Ghi ulescu and Socolescu (1941) report the occurrence of tellurides (tellurure, p. 362) from the Alpha vein at Fa a B ii, without giving more specific details. Ianovici et al. (1969) list the following species from Fa a B ii: nagyágite, krennerite, tetradymite, calaverite7 and empressite, native tellurium and tellurite8. The Fa a B ii mine is accredited as the TL for both native tellurium (Fig. 1g) and tellurite9. The former occurs as ~1 mm long prismatic needles in an assemblage including tellurides, pyrite and sulphosalts.

Fig. 5. Simplified geological map of mineralisation accessed from the Horia (+516 m) gallery, at Larga (after Cook and Ciobanu, 2004).

The Larga deposit, as originally defined, consists of a number of pyrite-dominated, gold-enriched lenses on the northeastern side of Roata Hill, a rare style of mineralisation within the GQ. These underlie the Fa a B ii veins. Workings on the Horia level at Larga also insersect the lower parts of veins exploited from Fa a B ii. Cook and Ciobanu (2004) have described Bi-tellurides (tetradymite, tellurobismuthite, tsumoite, Bi3Te4 - Pb-free rucklidgeite?), hessite, petzite, altaite, sylvanite10 and 7

The distinction between calaverite and krennerite by Ianovici et al. (1969) is unclear and the two minerals are effectively treated as a single phase in their review. 8 We note, however, discrepancies between the tabulated listing of minerals and the paragenetic scheme given in Fig. 243. 9 There has been some historical uncertainty about this (see Uduba a et al. 1992a). The latter quotes the work of Binder (1958) who proved the origin of native tellurium. In our view, some uncertainty must be considered to remain, given that there is no record of the Maria Hilf gallery in Ghi ulescu and Socolescu, 1941). 10 Not reported in Cook and Ciobanu (2004); compositional data are reported here for the first time.

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native tellurium from veins and minor skarn-like replacement mineralisation accessed from the Horia (+516 m) gallery (Larga deposit; Fig. 5). This mineralisation represents an intermediate part of the Fa a B ii system. Cervelleite is a minor component of the same ores (Cook and Ciobanu, 2003). Ag-Pb-Bi sulphosalts, some with Sb and/or Se, are intimately associated with the Bitellurides (see section on sulphosalts below). Taken with the occurrence of tellurides in the Trîmpoiele porphyry positioned below Larga (see below), the above trace mineralogy of the entire system is suggestive of a hydrothermal system strongly zoned with respect to fTe2 and, to a lesser extent, also fS2. Mineralogical and textural evidence suggests that initial crystallisation took place at temperatures in excess of 400 ºC. The association of gold with Bi-minerals is linked to the role of Bimelt as a scavenger for gold, and deposition within 'droplets' simultaneous with formation of arsenopyrite from löllingite + pyrrhotite. Cook and Ciobanu (2004) considered that, when there are widely distributed as in the Larga system, Bi-minerals (sulphosalts, tellurides/tellurosulphides) have considerable, untapped potential as tracers of the physical-chemical character of an evolving hydrothermal system. Ro ia Montan -Cetate There are no historical records of tellurides in the world-class Ro ia Montan breccia deposit, the gold is traditionally considered to occur only as native gold and electrum. Silver, however, displays a more diverse mineralogy with argentian tetrahedrite, argentite, proustite-pyrargyrite, pearceitepolybasite and stephanite accounting for a significant proportion of silver. Recent investigation (Ciobanu et al., this volume, c) of base metal-rhodochrosite11 veins in black breccia, Cetate pit at Ro ia Montan has revealed the presence of tellurides associated with gold. The assemblage (hessite, cervelleite, petzite, sylvanite) is described elsewhere. Studies of ore concentrates by Ro ia Montan Gold Corporation have also identified the presence of tellurides. Ro ia Montan -Cîrnicel T ma et al. (2004) have recently identified tellurides (hessite, altaite and an unspecified Au-Ag-Te phase) occurring with tetrahedrite and argyrodite, within high-grade (4.70 g/t Au, 1,152 g/t Ag) galena-sphalerite ore from Cîrnicel vein on mining level +853 m). Subsequent work on the tetrahedrite-dominant Cîrnicel occurrence has additionally confirmed the presence of cervelleite, petzite, sylvanite (presumably the previously unspecified Au-Ag-Te phase) in the assemblage, and has shown that the argyrodite is Te-bearing (Ciobanu et al., this volume, c). Arama and Bote (Bucium area) The N-S striking Arama vein accessed from the Napoleon gallery (845 m) is more than 4 km in length. This vein is noted between the Sf. Treime and Ana levels for the occurrence of hessite, with sylvanite, petzite and altaite, associated with base metal sulphides, sulphosalts and also bornite, covellite, chacocite and enargite (Ghi ulescu and Giu c , 1938; Ghi ulescu and Socolescu, 1941). The Bote deposit mainly worked a single vein (Iacob-Ana, although this was given different names on different levels) and is to be noted for the occurrence of exceptionally coarse hessite12 (Figs. 1e, f) and native gold (Ghi ulescu and Socolescu, 1941). Exploitation at Bote in the 19th century was characterised by repeated discovery (1857, 1875, 1891) of particularly rich lenses within the vein (Huber and Huber, 198313) that yielded spectacular Au grades, as well as numerous classic specimens.

11 12 13

The samples also contain Mn-pyroxenoids.. Often reported as bote ite in the classical literature, although this is not the type locality. 'Bote und Vuljóy-Korábia'. Lapis 8 (10): 28-30.

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TELLURIDES AND SULPHOSALTS IN THE GOLDEN QUADRILATERAL

Baia de Arie The Baia de Arie deposit (Fig. 6), known as the type locality for sylvanite (Figs. 1a, b) consists of spatially distinct gold and base metal ores14. Gold mineralisation occurs both as veins and breccia pipes15.

Fig. 6. Simplified geological map of the Baia de Arie deposit, after Cioflica et al. (1999). AVBR: Afini Vîn t-Baia Ro ie.

Two types of gold-bearing veins are recognised in the Baia de Arie deposit (Cioflica et al., 1999). Telluride-bearing veins are restricted to the E and SE parts of the Afini structure. These veins (nos. 9-21, Danieli, Sylvanite, Silberkluft, Goldkluft16, Neuekluft, Karoly (Carol), Kiesskluft, Ferdinand, Antoniu etc.) are NE-SW or E-W strikes, dipping 20-50º, with thickness of 1-30 m and lengths of up to 150 m. Quartz, rhodochrosite, calcite and barite host Au-tellurides, native gold, with some sulphides and sulphosalts. The telluride-free gold veins are generally thicker and are concentrated in the NW part of the Afini structure. The sylvanite vein is considered an exceptional case (Cioflica et al., 1999), with sylvanite forming monomineralic aggregates in quartz and barite. Significantly, this vein cuts breccia pipe no. 4. Cabri (1965) notes the following assemblages in samples from Offenbanya (sic.): gold-calaverite-petzite-altaite and calaverite-krennerite-petzite-altaite. Telluride occurrences in porphyry systems Several porphyry systems are recognised in the GQ; Bo tinescu, 1984; Berbeleac et al., 1995a, b; Cioflica et al., 1995). Minor quantities of sulphosalts have been reported, chiefly in peripheral veins (e.g., T lagiu, Voia), but to our knowledge, no tellurides have been historically described from any of them. The Deva porphyry is known to contain minor amounts of clausthalite (PbSe). 14

See Laz r (1966) for description of the polymetallic base metal ores.

15

See Ghi ulescu et al. (1979) and Cioflica et al. (1999) for detailed description of the gold breccia pipes.

16

With more native gold than is typical for this vein group; also argentite, pyrargyrite, stephanite (Cochet, 1957).

TELLURIDES AND SULPHOSALTS IN THE GOLDEN QUADRILATERAL

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Trîmpoiele Investigation of drillhole samples intersecting the Trîmpoiele porphyry system, 600 m beneath the Horia level, which is itself below the Fa a B ii veins, identified rucklidgeite as the single stable telluride, commonly associated with native gold (Cook and Ciobanu, 2004). Subsequent investigation of other samples from the same drillcore, but intermediate between Larga and the porphyry, have confirmed that tellurides are persistent over significant vertical extents, with the presence of hessite, altaite and clausthalite confirmed, as well as the second reported occurrence of melonite in GQ. Telluride mineralogy Gold and silver tellurides Nagyágite [Pb(Pb,Sb)S2](Au,Te) The mineral, which may occur as foliated blades up to several mm in size was first mentioned by Scopoli (1769) and von Born (1772) and subsequently reported by Werner (1789) as ‘Nagiakererz’ from S c rîmb. Haidinger (1845) named the mineral nagyágite17. Numerous studies have been carried out until modern times to discern the composition and structure of nagyágite from S c rîmb or other occurrences (Schrauf, 1878; Sipöcz, 1885; Hankó, 1886; Helke, 1934; Gossner, 1935; Giu c , 1937; Stumpfl, 1970; Uduba a, 1986; Spiridonov, 1991; Uduba a et al., 1993; Stanley et al., 1994; Lupulescu, 1997 etc.). Further details tracing the unique 216-year story of nagyágite can be found in several of the above publications. Compositional data compiled in R dulescu and Dimitrescu (1966), together with more recent compositional data, are summarised in Table 2. Recently, Effenberger et al. (1999) proposed the formula [(Pb3(Pb,Sb)3)S6][(Au,Te2)3], which fits their structural data. Nagyágite is considered as a hybrid phase, with characteristics of both sulphosalts and tellurides. Furthermore, it is proposed to belong to a homologous series with buckhornite, [(Pb2Bi)3S3][(Au,Te2)3]. Despite the earlier claim that nagyágite displays a consistent composition (Stumpfl, 1970), Cioflica et al. (1993a) and imon et al. (1994) demonstrated compositional zonation within single grains of nagyágite, thus confirming the earlier supposition of Giu c (1937) that the mineral may not be homogeneous, and the microscopic observation of distinct varieties by Uduba a (1986). imon et al. (1994) described As-nagyágite as a possible new mineral, forming a continuous series with nagyágite, in which As substitutes for Sb, i.e., [(Pb3(Pb,Sb)3)S6][(Au,Te2)3] - [(Pb3(Pb,As)3)S6] [(Au,Te2)3]. The As-rich variety was also marked by a relative deficiency in Pb and surplus of (Au+Te). Lupulescu (1997) investigated the lack of homogeneity in some specimens of nagyágite in further detail. Compositional data was presented that showed significant compositional variation also with respect to Au/Te, including varieties lower in Au (nagyágite 2 and 3) than had been reported previously18.

17

Several synonyms exist in the early literature, including aurum galena, black tellurium, foliated tellurium, Blättererz, Blättertellur, elasmose, elasmosine and Graugolderz.

18

Taking this into account, the formula may better be written as [(Pb3(Pb,Sb)3)S6][(Au1-xTe2+x)3].

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Sipöcz (1885) Hankó (1886)

1 2

Tokody (1930) Giu c (1937)

1 2 3 4 5 6 1 2

Palache et al. (1944)

Dana (7th ed.) in Stumpfl (1970) Stumpfl (1970) Cioflica et al. (1993) 1 2 Maury et al. (1993) 1 2 3 4 Uduba a et al. (1993) Stanley et al. (1994) 1 2 imon et al. (1994) 'high As' 'high As' – mean of 53 'low As' 'normal' nagyágite Lupulescu (1997)* 1 2 3 4 5 6 7 8 9 Effenberger et al. (1999)

Pb 56.81 57.20 57.13 54.50 56.36 56.45 55.90 56.31 56.06 55.95 55.44 53.55 57.16 57.6 57.74 57.22 59.03 56.96 55.10 54.20 56.77 56.78 56.84 54.2 53.1 55.0 55.8 59.19 58.99 57.13 56.19 57.65 56.66 57.95 58.09 56.58 55.98

Au 7.51 7.61 7.21 7.61 7.65 7.57 8.20 8.02 8.03 8.18 8.43 9.47 7.41 7.6 5.66 3.62 7.90 8.56 9.25 9.68 7.78 7.47 7.66 11.5 10.1 10.3 10.5 3.12 3.18 5.60 3.56 6.59 3.43 5.47 5.60 3.98 11.15

Ag 0.28 0.03 0.03 0.20 0.12 0.19 0.12 0.07 0.1 0.1 0.1 10 wt. % Te. We cautiously propose (Ciobanu et al., this volume, b) that there may exist partial solid solution along the FeTe2-FeAs2 join. Coloradoite (HgTe) Ramdohr (unpubl. notes) had identified coloradoite in a section (10 777) from his collection. Popescu and Constantinescu (1992) reported coloradoite in specimens from St nija within the 'Petrulian' collection, University of Bucharest. Coloradoite occurs as sub-100 µm rims (overgrowths or replacements?) on krennerite and sylvanite and along fissures and cleavage planes of krennerite. Coloradoite was considered to be the youngest telluride formed at St nija. Cioflica et al. (1993a, b) and Popescu and imon (1995) respectively give compositional and reflectivity data for coloradoite from S c rîmb. The mineral is also reported from Baia de Arie , where it is associated with sylvanite, bournonite and tetrahedrite (Cioflica et al., 1999), deposited after the latter two minerals. Cioflica et al. (1993) (S c rîmb)

Hg 56.50

Au -

Ag 0.20

Sb -

Mo 2.76

Te 40.50

S -

Total 99.96

Table 10 Compositional data for coloradoite.

Melonite (NiTe2) Sindeeva (1959) reported melonite from S c rîmb, where the mineral occurs as inclusions within nagyágite. A second occurrence in the GQ is the occurrence of numerous but minute (