Minor and trace elements in bornite and

Minor and trace elements in bornite and associated Cu–(Fe)-sulﬁdes: A LA-ICP-MS study

a c Nigel J. Cook c ⇑ , Cristiana L. Ciobanu , Leonid V. Danyushevsky , Sarah Gilbert

a Centre for Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, University of Adelaide, SA 5005, Australia

b South Australian Museum, Adelaide, SA 5000, Australia c CODES, University of Tasmania, Australia

Received 4 May 2011; accepted in revised form 10 August 2011

Abstract In situ laser ablation inductively-coupled mass spectroscopy (LA-ICP-MS) has been used to provide a baseline dataset on

the minor element contents in hypogene bornite and accompanying Cu-sulﬁdes from 12 deposits with emphasis on syn-metamorphic Cu–vein systems in Norway, and skarn, porphyry and epithermal systems in SE Europe.

Bornite contains significant concentrations of both Ag and Bi, especially in the vein and skarn deposits studied and has the potential to be a major Ag-carrier in such ores. Concentrations of up to >1 wt.% of both elements are documented. Measured concentrations appear to be independent of whether discrete Ag- and/or Bi-minerals are present within the analyzed sulfide. Where bornite and chalcocite (or mixtures of Cu-sulfides) coexist, Ag is preferentially partitioned into chalcocite over co-existing bornite and Bi is partitioned into the bornite. Bornite is a relatively poor host for Au, which mimics Ag by being typically richer in coexisting chalcocite. Most anomalous Au concentrations in bornite can be readily tracked to micron- and submi- cron-scale inclusions, but bornite and chalcocite containing up to 3 and 28 ppm Au in solid solution can be documented. Sele- nium and Te concentrations in bornite may be as high as several thousand ppm and correlate with the abundance of selenides and tellurides within the sample. Selenium distributions show some promise as a vector in exploration, offering the possibility to track a fluid source. Bornite and chalcocite are poor hosts for a range of other elements such as Co, Ni, Ga and Ge, etc. which have been reported to be commonly substituted within sulfides. Hypogene bornite and chalcocite may have significantly different trace element geochemical signatures from secondary (supergene) bornite. Ó 2011 Elsevier Ltd. All rights reserved.

1. INTRODUCTION District, Indonesia; Rubin and Kyle, 1997 ). Simon et al. (2000), Kesler et al. (2002) and Kesler (2004) contend that

high-temperature bornite may, at least initially, host a sig- common Cu-sulﬁdes. Bornite is a major Cu-carrier in many

After chalcopyrite, bornite (Cu 5 FeS 4 ) is among the most

niﬁcant amount of the total gold budget in some porphyry high-sulﬁdation epithermal deposits ( White and Heden-

deposits. Bornite can also be a major mineral in parts of quist, 1990 ), sedimentary-hosted copper deposits such as

some volcanogenic massive sulﬁde (VMS)-type deposits the Kupferschiefer of northern Europe (e.g., Piestrzynski

(e.g., Neves Corvo, Portugal; Gaspar, 2002 ). Importantly, and Sawlowicz, 1999 ) and some porphyry–Cu deposits

together with chalcocite (Cu 2 S), bornite is the dominant and associated Cu- and polymetallic skarns (e.g., Ertsberg

Cu-carrier in iron oxide–copper–gold (IOCG) deposits, such as Olympic Dam, Prominent Hill and others in the

⇑ Corresponding author at: Centre for Tectonics, Resources and Gawler Province of South Australia (e.g., Skirrow et al.,

Exploration (TRaX), School of Earth and Environmental Sciences, 2002; Skirrow and Davidson, 2007 ). University of Adelaide, SA 5005, Australia.

Understanding of Cu–(Fe)-sulﬁde mineral chemistry has E-mail address: nigel.cook@adelaide.edu.au (N.J. Cook).

both processing and exploration implications in all the

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

above deposit types. This is because knowledge of the min- tration of Ag and other elements in solid solution within or and trace elements carried by a host sulﬁde, including

bornite and co-existing Cu–(Fe)-sulﬁdes. Even if bornite ss bornite, is essential to evaluate the distribution and parti-

hosts structurally-bound minor elements, how would they tioning of potential economically-valuable components,

be partitioned within diﬀerent ﬁelds of exsolution at critical such as Au, Ag or In, between co-existing minerals. Such

points during cooling, and how are they retained in the information can be used to optimize processing and thus

structures of Cu–(Fe)-sulﬁdes across phase transforma- ensure improved recoveries of by-products. The minor

tions? Determination of minor and trace element concen- and trace element concentrations in sulﬁdes and their distri-

trations in bornite and associated Cu–(Fe)-sulﬁdes from butions have potential as vectors to assist in mine-scale

deposits of diﬀerent types, and displaying diverse types of exploration. Understanding how supergene processes aﬀect

exsolution and inclusions, is thus a first step towards under- bornite and Cu–(Fe)-sulfides and influence their surface

standing the mechanisms controlling exsolution relative to properties also has implications for minerals processing

retention of elements in the crystal structure. and environmental geochemistry (e.g., Vaughan et al.,

Our study provides a set of baseline data on the minor 1987; Harmer et al., 2005 ).

element contents in bornite and accompanying Cu-sulﬁdes The Cu-rich corner of the system Cu–Fe–S is complex,

from ores with an apparently relatively simple geological featuring many low-T phases but a large ﬁeld of solid-solu-

history using in situ laser-ablation inductively-coupled mass tion (bornite ss ) at high temperature ( Yund and Kullerud,

spectroscopy (LA-ICP-MS). Thirty-two samples from 12

deposits were analyzed. A total of 28 isotopes were moni- Cu 5 FeS 4 –Cu 9 S 5 . From the latter, hexagonal, high-T chalco-

1966 ), which covers the compositional range Cu 2 S–

tored ( 49 Ti, 51 V, 53 Cr, 55 Mn, 57 Fe, 59 Co, 60 Ni, 65 Cu, 66 Zn, cite becomes stable below 435 °C and the bornite ss ﬁeld

69 Ga, 72 Ge, 75 As, 77 Se, 93 Nb, 95 Mo, 107 Ag, 111 Cd, 115 In, splits into two, where the larger part is the bornite–digenite

118 Sn, 121 Sb, 125 Te, 182 W, 185 Re, 197 Au, 205 Tl, 208 Pb, 209 Bi solid solution and the smaller is the chalcocite solid solution

and 238 U) from which element concentrations were calcu- ﬁeld. Monoclinic low-T chalcocite (<104 °C) and djurleite

lated. The trends within this data are compared with pub- (Cu 1.97 S) are structurally related to high-T chalcocite.

lished data and interpreted in terms of both observed Upon cooling, a series of bornite superstructures are

textures and phase diagrams. Our purpose is to identify formed at T < 265 °C ( Pierce and Buseck, 1978 ). Super-

the more common trace elements in these minerals and to structures are larger structures with a distinct structural

establish common trends in the data. sub-motif expanded in 1, 2 or 3 dimensions, in which one feature in the motif varies an ordered manner, e.g. the

2. DEPOSITS AND SAMPLE SUITE arrangement of metal vacancies in 2a, 4a or 6a bornite

Sample material ( Table 1 ) was selected from deposits in tures result from further cooling below 75 °C when com-

( Pierce and Buseck, 1978 ). Digenite (Cu 1.8 S) superstruc-

which chalcophile (Ag, Bi ± Au, As, Sb) and chalogenide bined with changes in the Fe/Cu and M/S ratios. This

elements (Se, Te) give a prominent geochemical and miner- complexity is also reﬂected in the presence of ﬁne inter-

alogical signature closely tied to hypogene bornite and Cu– growths with varying textures in natural samples. It is often

(Fe)-sulﬁdes. Our sample suite encompasses bornite (±chal- diﬃcult to distinguish exsolution sequences from supergene

cocite) assemblages formed in a single event, i.e., without low-T replacement relationships. Despite numerous studies

signiﬁcant overprinting, replacement or supergene alter- ( Morimoto and Kullerud, 1961; Brett, 1964; Morimoto,

ation which might inﬂuence trace element patterns. 1964; Yund and Kullerud, 1966; Sugaki et al., 1975; Putnis

The samples are from two distinct geological terranes: (i) and Grace, 1976; Kanazawa et al., 1978; Durazzo and Tay-

Late Proterozoic metamorphic Cu–vein systems in southern lor, 1982; Grguric and Putnis, 1999; Grguric et al., 2000;

Scandinavia; and (ii) magmatic hydrothermal deposits Fleet, 2006 ), there are still some uncertainties as to the sta-

(skarn, porphyry and epithermal systems) from the one of bility of bornite and associated phases and how exsolution

the metallogenetic belts in SE Europe, the Late Cretaceous textures develop, especially in the low-temperature part of

Banatitic Magmatic and Metallogenetic Belt, BMMB; Cio- the system. On the other hand, the central part of the sys-

banu et al., 2002 ). One sample of bornite (Museum collec- tem Cu–Fe–S also contains an important ﬁeld of solid solu-

tion, South Australian Museum) from the Proterozoic tion (iss), which diminishes in size from >600 °C to below

Olympic Dam IOCG deposit, South Australia, was ana- 400 °C and which is linked by tie-lines with bornite ss ( Cabri,

lyzed for purposes of comparison. In contrast to the other 1973 ).

samples, this consists of equal amounts of bornite and chal- Bornite commonly hosts inclusions of mineral phases,

copyrite and is free of any mineral inclusions containing notably Ag-, and more rarely, Bi-bearing chalcogenides,

chalcophile or chalcogenide elements. gold grains, and even platinum-group minerals (PGM). Can such inclusions be exsolved from high-temperature

2.1. High-temperature hypogene bornite and chalcocite from bornite (bornite ss ) containing structurally-bound Ag, Bi,

Cu–vein systems (Type-A)

Au, etc.? Alternatively, are they the result of later replacement during interaction with ﬂuids? Sugaki et al. (1984)

The Late Proterozoic Sveconorwegian province hosts found that bornite can incorporate >10 wt.% Bi at

numerous small but often rich vein-type deposits and pros- 300 °C, coexisting with wittichenite exsolved at 395 °C;

pects of Cu–(Ag)–(Au), many of which have been histori- chalcocite incorporates rather less Bi. Relatively little is

cally exploited, especially in Telemark County, Southern

Table 1 Sample suite for analyzed Cu–(Fe)-sulﬁdes.

Locality Geology

Reference(s) Metamorphosed Late Proterozoic veins, Southern Scandinavia

Samples

Ore mineralogy

Tinnsja˚, Late Proterozoic amphibolites-associated Tsj1, Tsj1a, Tsj2 (open pit)

Cook et al. (2010) Telemark,

Magnetite, bornite, chalcocite, minor

vein Cu–Ag deposit

Tsj5, Tsj6, Tsj7 (lower dump)

djurleite, wittichenite, Ag-minerals, minor

Norway

Tsj9 (upper adit)

molybdenite (Tsj9 only) Chalcopyrite

Tsj14 (lower adit)

only Bornite, hematite, wittichenite

Tsj12 (lower adit) Tsj13 (lower adit)

Moberg, Late Proterozoic granite-associated vein

Bornite, chalcocite, digenite, chalcopyrite http://www.ngu.no Telemark,

Mo1, Mo2, Mo6 (dumps next to upper adits) Mo3

Cu–Ag–(Au)-Mo deposit

(dump next to lower adits)

(Mo2 only), molybdenite, wittichenite

Norway

(except Mo3), galena–clausthalite, native gold, hessite, petzite, cervelleite (Mo3), Bi–tellurides

Grusen, Late Proterozoic granite-associated vein

Bornite, chalcocite, digenite, chalcopyrite, http://www.ngu.no Telemark,

Gr1, Gr2, Gr3 (dumps next to adits)

Cu–Ag–(Au)-Mo deposit

wittichenite, minor molybdenite, hessite,

Norway

native gold

Nordrum (1972) Bornite Telemark,

Tjøstølﬂaten, Veinlets in basalts

Tj1 (roadside dump)

Hematite, bornite, wittichenite

Norway Glava, Sweden

Sveconorwegian (ca. 1.15–0.9 Ga) Cu–

Oen and Kieft (1981) mineral Ag–Au veins in granitic gneisses, Mjøsa-

GL99.5 (dump next to adit)

Magnetite, bornite, chalcocite and

covellite (supergene), native gold, Au–Ag

Va¨nern belt

and Bi–tellurides

chemistry Late Cretaceous Banatitic Magmatic and Metallogenetic Belt, Se Europe ( Ciobanu et al., 2003 )

North Apuseni Mts. (Romania) Baitßa Bihor

Cu–Mo–(Pb–Zn) skarn

BB20A (garnet-diopside

Bornite

Ciobanu et al. (2002, 2003)

skarn, central part of Antoniu Nord orepipe)

Bornite, mm- to cm-sized sphalerite

BB19CB (diopside-wollastonite skarn, Antoniu Nord

(exsolved)

orepipe) BB13F (garnet skarn at marble contact,

Bornite Bornite, carrollite, Co–Ni-

Antoniu Nord orepipe)

sulphides

BB13B (pyroxene Di 80 Hed 15 Joh 5 – wollastonite skarn, Bornite, chalcocite (late), Ag-minerals

outer marble contact, Antoniu Nord orepipe)

(hessite, etc.)

BB3 (humite skarn, deeper level, Antoniu Nord

Bornite, chalcopyrite, chalcocite (late)

orepipe)

Bornite, chalcopyrite, chalcocite (late)

BB170B (humite skarn, Antoniu Nord orepipe)

Bi-bearing tetrahedrite, miharaite

BB171 (humite skarn, Antoniu Nord orepipe)

All samples contain exsolved chalcopyrite and wittichenite

Banat (Romania) Ocna de Fier

Fe–Cu–(Zn–Pb) skarn

CuSI (forsterite skarn, Simon Iuda orebody, proximal Bornite, magnetite, minor chalcopyrite,

Cook and Ciobanu (2001),

Cu skarn)

galena, wittichenite, mawsonite, valleriite Ciobanu and Cook (2004)

CuPP SI (diopside skarn, Petru-Pavel – Simon Iuda

Chalcopyrite, minor bornite, chalcocite

orebody, proximal Cu skarn)

(supergene)

Sasca Montana˘ Cu–Au skarn

SM2 (roadside dump)

Pyrite, bornite

Ciobanu et al. (2002) (continued on next page)

Besides bornite, Cu–(Fe)-sulfides are also major components of the ores, i.e., chalcocite at Tinnsja˚, digenite at Mo- berg and Grusen; chalcopyrite is a relatively minor component of some samples only. Exsolution relationships between bornite and the Cu-sulfides ( Fig. 1 a–c) indicates a hypogene origin for the latter in all deposits except Glava, where the subordinate chalcocite is clearly secondary. The more complex exsolution sequence in a type of bornite from Moberg (Mo2) is, however, more difficult to interpret. This bornite has chalcocite only as fine mesh-like symplectites, with their density varying across the grain and appears later than the exsolution of chalcopyrite followed by galena- clausthalite ( Fig. 2 a and b). In this study, we address element partitioning between bornite and chacocite and bornite and digenite in the Tinnsja˚, Moberg and Grusen deposits.

All the Cu-ores have a prominent Bi-rich signature and wittichenite (Cu 3 BiS 3 ), is a conspicuous component in all except Glava ( Fig. 2 a–c). Bornite from the Moberg, Grusen and Glava deposits contains abundant telluride, tellurosulfide and telluroselenide phases of the tetradymite group ( Fig. 2 d and e; Cook et al., 2007a; Ciobanu et al., 2009a ) and at Moberg, also the aleksite group ( Cook et al., 2007b ), as well as Au–Ag–tellurides and tellurosulfides (hessite, petzite and the Ag–tellurosulfide cervelleite; Cook and Ciobanu, 2003 ; Fig. 2 f), altaite, clausthalite and other species (volynskite, kostovite) in Glava ( Bonev et al., 2005 ). On the other hand, bornite from Tinnsja˚ ( Cook et al., 2010 ), and Tjøstølflaten, lacks tellurides or gold but contains, in Tinnsja˚, various Ag-and Bi-minerals (stromeyerite, larosite and bismuthinite derivatives). The nine samples from Tinnsja˚ are representative of the 500 m vertical extent of the vein system; all samples contain both bornite and chalcocite ( Fig. 1 c), but the latter is absent in sample Tsj13. Chalcopyrite is appreciably more abundant in material from upper levels (Tsj9), where bismuthinite derivatives and molybdenite are also observed.

In the Tinnsja˚ occurrence, a transmission electron microscope (TEM) crystal-chemical investigation of larosite and host Cu–(Fe)-sulﬁdes has shown a coherency between the exsolved Ag-minerals and varieties of Cu–(Fe)- sulﬁdes present. Boundary zones between host and exsolved phases feature sub-microscopic intergrowths of chalcocite, djurleite and low-temperature bornite superstructures inti-

Reference(s)

Cu–Au

na–cla

l Cu–Au

Cu–Au

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

Bornite mineral chemistry

Fig. 1. Photomicrographs in reflected light. (a–c) Typical primary bornite–chalcocite associations in the Norwegian hypogene sulfide samples. Dark spots are LA-ICP-MS craters. (a) Digenite (Dg), with formation of supergene covellite (Cv) along fractures; Moberg, sample Mo1. Bn: bornite. (b) Detail of a larger area of coarse symplectite between bornite (Bn) and Cu-sulfides showing that the latter consist of a fine mixture of chalcocite (Cc) and digenite (darker bluish color on image). Note how fine symplectites surround larger areas of Cu-sulfides; Grusen, sample Gr1. (c) Worm-like intergrowth of bornite (Bn) and chalcocite (Cc); Tinnsja˚, sample Tsj9. (d–f) Aspects of bornite in skarn ores. (d) Typical, oriented type of exsolutions of wittichenite (Witt) and chalcopyrite (Cp) in bornite (Bn) from Baita Bihor; sample BB1b. (e) Unusual, coarse symplectite of bornite (Bn) and In-bearing sphalerite (Sp) from Baita Bihor; sample BB19CB. Note marginal (secondary) chalcocite (Cc). (f) Typical galena (Gn) exsolution in Ocna de Fier bornite (Bn) and narrow veinlets composed of valleriite (Val, middle) and chalcocite + wittichenite (margins); sample CuSI. (g) Atoll-like textures composed of fine-grained, dusty bornite (atoll cores) and chalcopyrite/pyrite (on margins), Sasca Montana; sample SM2. (h) Pyrite showing atoll-like textures within a matrix of bornite (Bn) and coarse and bleb-like inclusions of native gold (Au), Chelopech; sample CPK3. (For interpretation of color mentioned in this figure the reader

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

Fig. 2. Back-scattered electron images showing aspects of Scandinavian (a–f) and Baita Bihor skarn ores (g and h). (a and b) Cleavage- controlled exsolution of chalcopyrite (Cp) in bornite (Bn) onto which bleb-like exsolution of intermediate galena–clausthalite solid solution (PbS–PbSe; Gn–Cls) is superimposed. Surrounding the chalcopyrite lamellae and on the margins of bornite is a fine network of late djurleite (Dj) of possible supergene character; Moberg, sample Mo2. (c) Typical field of wittichenite (Witt) exsolution in chalcocite (Cc), possibly reflecting crystallisation from a higher-temperature precursor phase; Tinnsja˚, sample Tsj2 (d) Characteristic type of trace Ag- and Bi-telluride inclusions (Hs – hessite and Tbs – tellurobismuthite) in Glava bornite; sample GL99.5. (e and f) Inclusions of tellurides, tellurosulfides and selenides in bornite from Moberg. In (e), (sample Mo1), hessite (Hs) with lamellae of clausthalite (Cls) and in (f) (sample Mo3), hessite with marginal symplectite of cervelleite (Cerv). (g) Cleavage-oriented fine exsolution of wittichenite (Witt) in bornite (Bn); Baita Bihor, sample BB20A. (h) Atypical symplectite of galena (Gn) and chalcocite (Cc) in bornite (Bn); Baita Bihor, sample BB1a.

oscillatory twinning. There is clearly crystal-structural an unambiguous name to the Cu-phases analyzed by LA- control on nucleation of exsolved Ag and Bi from structur-

ICP-MS.

ally-related Cu–(Fe)-sulﬁdes. The TEM study also helped The exsolution relationships in Moberg and Grusen

6479 400 °C, i.e., chalcopyrite-bornite from iss and digenite–

Bornite mineral chemistry

ated with magnetite and chalcopyrite, forms the early (high- (bornite) and chalcocite from bornite ss . Similarly, the born-

temperature), proximal Cu–Fe core of the oreﬁeld ( Cook ite–chalcocite and chalcocite–wittichenite relationships in

and Ciobanu, 2001; Ciobanu and Cook, 2004 ). Bornite the Tinnsja˚ samples can be ascribed to formation above

hosts lamellar exsolution of galena–(clausthalite) cross-cut- 400 °C (probably > 435 °C). In the present study these are

ting former valeriite–witichenite–chalcocite exsolutions collectively considered as high-temperature (Type-A)

f. As at Baita Bihor, bornite also hosts a range of bornites.

( Fig. 1

other minerals (coarse native silver, cobalt pentlandite, carrollite, mawsonite, jalpaite and minor gold).

2.2. Hypogene mineralization in skarn and epithermal Bornite is also rarely present in the porphyry deposits of environments (Type-A)

the BMMB. An exception is the bornite associated with magnetite from the high-temperature, potassic Cu–Fe core

Bornite is an ore component in all deposit types from preserved in the Elatsite porphyry Cu–Au deposit. This across the magmatic-hydrothermal spectrum in the Late

bornite is remarkable for the occurrence of platinum-group Cretaceous Banatitic Magmatic and Metallogenetic Belt

minerals and gold ( Tarkian et al., 2003 ), is rich in selenides (BMMB) of southeastern Europe ( Ciobanu et al., 2002 ).

(chieﬂy as an intermediate galena–clausthalite phase) but This belt is also characterized by a prominent Bi–Te signa-

lacks any discrete Ag- or Bi-minerals. ture, in particular within Ag–Au-rich ores ( Ciobanu et al.,

The bornite from Baita Bihor is ‘Bi-saturated’; (ﬁelds of 2003 ).

wittichenite exsolution) and thus formed above 400 °C. Evi- The Cu–Mo–Pb–Zn skarn at Baita Bihor consists of a

dence for high-temperature bornite is also given for Ocna dozen orepipes located some 1.2 km above a granitic bath-

de Fier ( Cook and Ciobanu, 2003; Ciobanu and Cook, olith and hosted within a sequence of Triassic-Jurassic car-

2004 ) and Elatsite, where the ore ﬂuids had temperatures bonate units ( Cioﬂica et al., 1977 ). There is a west-to-east

from 340 to >700 °C ( Tarkian et al., 2003 ). We regard these metal zonation (Mo–Cu–Pb/Zn) across the oreﬁeld, but

skarn and porphyry bornites as analogous to the Type-A each orepipe also features similar zonation trends from core

bornites in the Scandinavian veins above. to the skarn-marble contact, sometimes with superposition due to telescoping. Such aspects are reﬂected in the four

2.3. Lower-temperature Cu-rich systems in skarn and analyzed bornites from the Antoniu Nord orepipe, with

epithermal environments (Type-B) positions from inner humite–diopside skarn (BB20A) to diopside–wollastonite skarn (BB19CB) to outer skarn-mar-

Bornite is not a major component of the Cu-skarns asso- ble contact (BB13F, 13B). Bornite contains a wide variety

ciated with porphyry mineralization in the BMMB, but we of exsolved assemblages which vary from sample to sample

include a sample representing low-temperature, atoll-like, ( Cook and Ciobanu, 2003 ). Wittichenite is nevertheless

ﬁne-grained bornite, forming the cores of collomorph arse- ubiquitous and is often present as exsolutions oriented

g) from the Au-rich ore at Sasca Mon- along cleavage in bornite from the inner part of orepipes

nian pyrite ( Fig. 1

tana ( Constantinescu, 1980 ). Bornite contains neither Ag- (BB20A; Fig. 2 g). The abundance of Bi and intimate asso-

nor Bi-minerals, but contains dusty, sub-microscopic As– ciation of Bi-minerals in the Cu-ores presents a signiﬁcant

Sb-bearing minerals. Although part of a skarn system, the problem in ore processing. Exsolutions of chalcopyrite are

bornite from Sasca Montana is clearly a late, low-tempera- observed either together with wittichenite, or with chalco-

ture mineral in the assemblage because of the ﬁne-grain size cite ( Fig. 1 d). Baita Bihor bornite also displays more unu-

and presence of atoll textures and dusty inclusions. We will sual textures, such as ﬁne symplectites with galena

here refer to it as Type-B, to clearly distinguish it from the ( Fig. 2

h) or Bi-tetrahedrite, mm-scale intergrowths with higher-temperature bornite from the Scandinavian systems sphalerite (BB19CB; Fig. 1 e), and rims of tennantite zoned

and from the Baita Bihor, Ocna de Fier and Elatsite depos- with respect to Bi. Among other mineral inclusions abun-

its above.

dant in bornite are native gold, hessite and cervelleite (see The Panagyurishte District in the BMMB hosts epither- Cook and Ciobanu, 2003 ). A range of more exotic minerals

mal systems with variable sulﬁdation states, but bornite is are also observed, including Sn-minerals (mawsonite in

only present in the high- and intermediate-sulﬁdation BB20A), Ag-sulﬁdes and selenides, and Ni–Co-minerals

deposits. In Chelopech, bornite forms part of the Au-rich (millerite, polydymite and vaesite in BB13B). Although

ores, showing abundant inclusions and skeletal exsolutions Baita Bihor is well known for a wide range of Bi-sulfosalts

of gold ( Fig. 1 h). Bornite is associated with spectacular col- and – tellurides, such minerals are rare in bornite. Unlike

lomorph arsenian pyrite, chalcopyrite and enargite. Fluid the above samples, specimens from deeper working levels

inclusions in enargite gave homogenization temperatures in the deposit (BB3, BB170B, BB171) contain abundant

of 175–221 °C ( Moritz et al., 2004 – but requiring a correc- chalcopyrite, as well as a late (possibly supergene) chalco-

tion upwards by 15–25 °C; Moritz, 2006 ). In Radka, born- cite. Miharaite, an Fe-bearing Bi-sulfosalt is also conspicu-

ite is known from several stages of mineralization, where it ous within bornite from deeper parts of the Antoniu Nord

is considered late in the sequence following chalcopyrite pipe (sample BB171).

Kouzma- The Ocna de Fier-Dognecea Fe–Cu–(Zn–Pb) skarn is a

nov, 2004 ). Similar to Chelopech, the bornite in our sample zoned, 10 km-long oreﬁeld tied to a granodiorite intrusion,

contains inclusions of enargite. Bornite is associated with with 15 orebodies located at the contact between Jurassic

minor chalcopyrite, sphalerite and galena and predates a

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

Bornite from the Chelopech and Radka epithermal systems The LA-ICP-MS method is, essentially, a bulk analytical and bornite from Sasca Montana are here considered as a

method in which a volume of sample material is ablated relatively lower-temperature of bornite (Type-B).

which may contain micron-scale inclusions exposed at or below the sample surface, as well as ﬁne- or nanoparticles

3. ANALYTICAL METHODOLOGY (100–2500 nm and <100 nm, respectively) that are invisible even under the SEM. The quest for low minimum detection

One-inch polished mounts were prepared from the se- limits means that the spot diameters (and thus analyzed vol- lected samples. Optical and scanning electron microscopy

umes) need to be suﬃciently large to generate an adequate (SEM) in back-scattered electron (BSE) mode was used to

count rate. We thus caution the reader that there is always a characterize each; generally, the phases analyzed by LA-

risk that measured elements interpreted to be lattice-bound ICP-MS were coarse-grained and, wherever possible, free

may actually be present as ‘collateral’ inclusions only visible of visible inclusions or exsolutions of ‘exotic’ minerals.

at the nanoscale. Although the method allows for resolu- Each sample was also studied by electron microprobe to

tion of lattice-bound trace elements vs. sub-micron-scale ascertain the wt.% Cu content in bornite and Cu–(Fe)-sul-

inclusions, these inclusions need to be greater than a certain ﬁdes, and any minor elements present at elevated

size to be visible on the time-resolved depth spectra (see dis- concentrations.

cussion in Ciobanu et al., 2009b ). Homogeneously distrib- Electron probe microanalysis was carried out using a

uted nanoinclusions (<100 nm) of a discrete mineral will Cameca SX-51 instrument at Adelaide Microscopy. Oper-

generally give a ﬂat proﬁle indistinguishable from that ob- ating conditions were an accelerating voltage of 20 kV

tained if the elements in question are lattice-bound. These and a beam current of 20 nA. Standards used were: Bi 2 Se 3 issues, and new data on trace element distributions in Sn–

Ag-bearing ZnS, are highlighted in a recent paper in which lowing spectral lines: Bi Ma, Se La, Ag La, Cu Ka, Fe Ka

(Bi,Se), Ag 2 Te (Ag), CuFeS 2 (Cu,Fe,S), monitoring the fol-

LA-ICP-MS data are compared against high-resolution Fo- and S Ka. Count times were 20 s for all elements.

cused Ion Beam (FIB)-SEM, High-Angle Annular Dark LA-ICP-MS analysis was made using Agilent HP4500

Field (HAADF) STEM imaging and TEM studies ( Cio- (2007 run) and 70 (2009 run) Quadrupole ICP-MS

banu and Cook, 2011 ). We recommend that LA-ICP-MS instruments at CODES (University of Tasmania, Hobart,

trace element data are checked against observations from Australia). The instrument is equipped with a high-perfor-

other techniques permitting nanoscale resolution of the so- mance New Wave UP-213 Nd:YAG Q-switched laser abla-

lid solution vs. nanoinclusion issue whenever possible. This tion system equipped with MeoLaser 213 software. In our

has particular relevance for certain trace elements which, analytical routines, we have followed the methodology out-

intuitively, do not appear to have an obvious position with- lined by Danyushevsky et al. (2011) and applied to studies

in a tetrahedral-metal dominated structure. We also take of Bi-chalcogenides ( Ciobanu et al., 2009b ), pyrite ( Cook

the opportunity to remind the reader that a holistic appre- et al., 2009a ) and sphalerite ( Cook et al., 2009b ). We have

ciation of element incorporation at scales of observation be-

monitored the following isotopes: 49 Ti, 51 V, 53 Cr, 55 Mn,

tween the micron- and nanoscales is not available for most

57 Fe, 59 Co, 60 Ni, 65 Cu, 66 Zn, 69 Ga, 72 Ge, 75 As, 77 Se, 93 Nb,

sulﬁdes since application of nanoscale techniques to ore

95 Mo, 107 Ag, 111 Cd, 115 In, 118 Sn, 121 Sb, 125 Te, 182 W, mineralogy is very much in its infancy at present. 185 Re, 197 Au, 205 Tl, 208 Pb, 209 Bi and 238 U. A total of 204

spot analyses of bornite, and 87 of chalcocite/digenite

4. RESULTS (40–80 lm diameter spot size) were made. Fifteen analyses

of coexisting chalcopyrite were made for comparison. Total

4.1. Electron probe microanalysis

analysis time for each analysis (30 s pre-ablation and 60 s ablation time) was 90 s. Calibration was performed using

Electron probe microanalysis (EPMA data; Electronic the in-house standard (STDGL2b-2), see Danyushevsky

Appendix A ) was performed both before and after LA- et al., 2011 ). The composition of the bornite/chalcocite

ICP-MS analysis. The purpose of the EPMA runs prior (from electron microprobe data) allowed us to use Cu as

to LA-ICP-MS analysis was to conﬁrm the identity of the an internal standard to quantify the analyses.

main phases, allow selection of grains for LA-ICP-MS Low Ge concentrations cannot be quantiﬁed with full

and provide the necessary wt.% Cu values for quantitative

analysis (see below). The runs after LA-ICP-MS analysis dard, and the Ge concentration in the standard is not high

conﬁdence because of interference from 40 Ar 32 S in the stan-

were made around the ablation spots targeting chalcocite enough to ignore these interferences. For this reason, no Ge

and other Cu-sulﬁdes in order to constrain some of the value is published for standard STDGL2b2 ( Danyushevsky

anomalous Ag and Fe values obtained. Throughout the et al., 2011 ).

data, only Ag and Bi were noted alongside the major ele- For the Type-A hypogene sulﬁdes, our spot analyses

ments, at concentrations approximately comparable with measured element concentrations in clean grains of sulﬁde,

those measured by LA-ICP-MS (see below). except where sub-surface (collateral) inclusions were picked

The probe data showed bornite from all occurrences to up during analysis. Finding and analyzing clean areas of the

be stoichiometric Cu 5 FeS 4 , within analytical accuracy, ex- Type-B sulﬁdes was more problematic and we conceded

cept in sample Mo3, where an anomalous, Cu-rich, Fe-poor that, particularly in the cases of material from Sasca Mon-

bornite, commonly carrying microscopic intergrowths with tana and Chelopech, the analyzed grains contained abun-

other Cu-sulﬁdes ( Fig. 3 b), has a mean composition of

Bornite mineral chemistry

Fig. 3. (a) Diagram expressing electron probe microanalytical data for Cu–Fe–sulfides plotted as M/S (where M = Cu + Fe + Bi + Ag) vs. atom.% Ag, showing variation in M/S ratio and apparent non-stoichiometry in Cu-sulfides. Yellow squares represent anomalous, Ag-rich Cu–Fe–Sulfide compositions we attribute to sub-microscopic inclusions of stromeyerite and other Ag-minerals rather than solid solution. (b–

e) Reflected light photomicrographs of Norwegian hypogene sulfide specimens in immersion oil showing intergrowths among Cu–(Fe)-sulfides that explain some of the anomalous stoichiometry identified in (a). (b), Fine mesh of djurleite (blue) replacing bornite (pink, Bn) from sample Mo3 (Moberg). (c) Incipient and (d) advanced replacement of early Cu-sulfides (chalcocite, Cc) by patchy, fine-grained djurleite (Dj, darker blue); samples Gr1 (Grusen) and Tsj1a (Tinnsja˚), respectively. Note (in d) that replacement follows the chalcocite lamellae. (e) Pronounced anisotropy of digenite (Dg) replaced by covellite (Cv); sample Mo1 (Moberg). Note the homogeneity of the digenite. (For interpretation of color mentioned in this figure the reader is referred to the web version of the article.)

Gray-white ‘chalcocite’ from Tinnsja˚ has a composition (Cu 1.89 Ag 0.015 Fe 0.015 ) 1.925 S 1.015 , close to ideal djurleite,

ranging from close to Cu 2 S (mean Cu 1.95 Ag 0.04 S 1.01 ; M/

Cu 1.94 S.

A second population of a blue mineral, exempliﬁed by S = 1.905, e.g., sample Tsj1a). As explained in Section

S = 1.97, sample Tsj9) to Cu 1.931 Ag 0.015 Fe 0.016 S 1.034 (M/

samples Tsj2 and Tsj14 ( Fig. 3 c), has a mean composition

2.1 , the high variability in M/S ratio can be attributed to and distinct M/S ratio (1.80) very close to digenite, some microscopic intergrowths between chalcocite, the ma-

(Cu 1.78 Ag 0.01 Fe 0.01 ) 1.80 S 1.00 if calculated to 2.8 atoms. We jor species present, and other Cu-sulﬁdes, of which djurleite

illustrate the variation in M/S ratio on Fig. 3

a, which also

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

the diagram suggests that silver concentration would ap- the same order of magnitude and distributions show ‘nor- pear to decrease with M/S ratio and it lowest in composi-

mal’ Gaussian distributions on the histograms ( Fig. 4 a). tions approximating to digenite.

Silver concentrations in coexisting chalcocite/digenite The Cu–(Fe)-sulﬁdes from Moberg and Grusen have low-

from the Norwegian deposits are consistently higher than er M/S ratios than in Tinnsja˚, even though some individual

in bornite, although at the same order of magnitude ( Table analyses correspond to ideal chalcocite ( Fig. 3 a). In Grusen,

3 , Fig. 5 a). Like for bornite, proﬁles are ﬂat, indicating so- for example, mean compositions vary between Cu 1.925 -

lid solution ( Fig. 7 ). Mean concentrations for individual Ag 0.015 S 1.06 (M/S = 1.83) in Gr1 to Cu 1.86 Ag 0.01 Fe 0.03 S 1.10 samples range from 3866 to 8164 ppm. The highest single

(M/S = 1.72) in Gr3. This conﬁrms the identiﬁcation of analysis is 36,000 ppm in one grain from Grusen Gr3 ‘digenite’ from optical microscopy (characteristic blue color;

( Fig. 7 a).

Fig. 3

d) even though the lamellar habit and pleochroism Where both bornite and Cu-sulﬁdes coexist the data indicate that the phase(s) present are not necessarily cubic

show that Ag is concentrated into the Cu-sulﬁdes. Bornite digenite but rather superstructures derived from digenite.

in sample Tsj13, the single sample from Tinnsja˚ in which

chalcocite is conspicuously absent, has Ag concentrations in Gr3 approaches if expressed in terms of a formula unit of

These include anilite (Cu 1.75 S), which the mean composition

as high as in chalcocite from the same locality.

2.75 atoms [(Cu 1.70 Ag 0.01 Fe 0.03 ) 1.74 S 1.01 ]. Recalculation of

the mean composition in Gr1 to 2.8 atoms per formula unit

4.2.2. Bismuth

As for Ag, signiﬁcant concentrations of Bi were identi- The typically deep-blue Cu-sulﬁdes from Moberg

gives [(Cu 1.80 Ag 0.01 ) 1.81 S 0.99 ].

ﬁed in all analyzed bornites (hundreds or thousands ppm, ( Fig. 3

e) gave M/S ratios within the range of 1.64 to 1.82 in some cases up to 1 wt.%; Fig. 4 b). Some variation ap- and also characteristically higher Fe contents [mean

pears in samples from the same vein locality, e.g., Bi in

(Cu 1.86 Ag 0.01 Fe 0.04 ) 1.91 S 1.01 ; M/S = 1.74]. Recalculated as

bornite in samples Tsj13 and Tsj14 from Tinnsja˚ is around

half that in the other samples, suggesting some vertical that some of the lowest M/S ratios could be explained

anilite, this gives (Cu 1.705 Ag 0.01 Fe 0.035 ) 1.75 S 1.00 . We suspect

zonation in the system. The highest and most consistent by the presence of other phases such as spionkopite

concentrations were determined in all specimens from the

Baita Bihor skarn, the locality with the most abundant these have not been identiﬁed as such.

(Cu 1.39 S), yarrowite (Cu 1.12 S) or covellite (CuS), even if

ﬁelds of wittichenite exsolution. Otherwise, the presence For the purposes of convenience in the present paper, we

of discrete Bi-minerals other than wittichenite does not ap- refer to the analyzed grains with composition Cu 1.9-2.0 S as

pear to inﬂuence Bi concentrations in bornite. Like Ag, the chalcocite (e.g., in the Tinnsja˚ deposit) and those with com-

element always mimics the behavior of Cu in the time-re- position Cu <1.90 S as digenite (e.g., in samples from Moberg

solved downhole proﬁles ( Fig. 6 ), indicating the measured and Grusen).

Bi resides in solid solution. Standard deviations between spots from the same sample are low.

In Tinnsja˚, Bi concentrations in coexisting chalcocite

4.2. LA-ICP-MS data are several orders of magnitude lower than bornite ( Fig. 7 c). The digenite from Moberg and Grusen appears

Results for the LA-ICP-MS spot analyses of bornite somewhat higher (hundreds of ppm). The data indicate that (204) and chalcocite/digenite (87) and chalcopyrite (15)

Bi is always concentrated in bornite relative to both are summarized in Tables 2 and 3 and in Figs. 4 and 5 . Rep-

Cu-sulﬁdes, but that digenite is a better Bi-carrier than resentative LA-ICP-MS downhole proﬁles are shown in

chalcocite.

Figs. 6 and 7 for bornite and chalcocite/digenite, respectively. Full details and statistical analysis of the dataset

4.2.3. Gold

are given in Electronic Appendix A. Measured Au values in bornite are low (rarely >0.1 ppm), although individual spots from Sasca Montana

4.2.1. Silver and Chelopech give values up to 4 and 6 ppm, respectively. Silver has among the highest measured values of all ana-

Large signal variations in the time-resolved LA-ICP-MS lyzed elements; all bornites were found to contain Ag

downhole proﬁles for these spots suggest the concentrations ( Fig. 3 a), with mean concentrations in a given sample rang-

relate to sub-lm inclusions.

Sample Mo2, with complex sequential exsolution 13). All the metamorphic Cu–veins in southern Scandina-

( Fig. 2 b), is anomalous in terms of Au content; concentra- via, except Glava, and most of the BMMB skarns, have

tions in bornite range from 0.55 to 3.0 ppm – with smooth comparable Ag concentrations (>1000 ppm). Bornite is

LA-ICP-MS downhole proﬁles ( Fig. 6 b), conﬁrming that clearly a major Ag-carrier in these deposits. Silver mimics

Au may still be locked within the bornite structure, espe- the behavior of Cu in the time-resolved downhole proﬁles

cially if Cu-sulﬁdes are absent or minor in the sample. collected by LA-ICP-MS ( Fig. 6 ), regardless of whether dis-

In both Moberg and Grusen, coexisting Cu-sulﬁdes may crete Ag-minerals are present in the sample or not. This

contain Au at concentrations at least one order of magni- suggests that the element likely resides in solid solution.

tude higher than bornite ( Electronic Appendix A). Of note Standard deviations between laser spots from the same

are concentrations of 1.6 to 24 ppm Au in digenite from sample are typically <5% of the respective mean. Mean val-

Gr3 (the spot giving >36,000 ppm Ag gave 24 ppm Au;

Table 2 Mean concentrations for minor and trace elements in bornite determined by LA-ICP-MS (ppm).

Sn Te Tl U Late Proterozoic metamorphosed veins (Norway, Sweden)

Tinnsja˚ Tsj1 (6)

0.01 3.3 0.04 0.10 <0.01 0.002 Tinnsja˚ Tsj1a (3)

0.07 1.5 a 1.35 0.02 15.3 <mdl 0.23 <mdl 0.01 Tinnsja˚ Tsj2 (4)

1701 <mdl <mdl 1017

0.02 <mdl <mdl 0.56 0.15

0.39 <mdl <3.5 <mdl 2.8 <mdl <mdl Tinnsja˚ Tsj6 (5)

1609 <mdl <mdl 897

<mdl <0.05 <mdl –

<mdl <mdl 0.01 <mdl Tinnsja˚ Tsj7 (8)

0.03 4.0 <mdl 0.30 0.02 <mdl Tinnsja˚ Tsj8 (5)

1325 <mdl <mdl 987

<mdl <mdl <mdl –

0.38 0.07 <mdl 1.4

1329 <mdl 0.012 1238

<mdl <mdl <mdl –

1.3 <mdl <mdl 0.17

<mdl 3.2

<mdl 2.8 <mdl <mdl

<mdl 3.8 0.02 <mdl Tinnsja˚ Tsj13 (4)

Tinnsja˚ Tsj9 (6) b 1167 <mdl 0.001 1449

0.03 a 0.02 0.01 0.52 0.75

0.02 0.01 30.0 a <mdl 5.7

2.7 0.18 19.4 0.02 12.9 0.18 2.3 0.20 3.8 Tinnsja˚ Tsj14 (6)

1.2 0.02 6.7 <mdl 16.7 0.05 0.18 0.01 0.01 Moberg Mo1 (3)

15.3 <mdl 1156 <mdl 27.3 0.01 <mdl Moberg Mo2 (7)

0.31 86.1 0.08 6.5 a Moberg Mo3 (4)

31.1 a 0.01 185 a 0.11 879

<mdl 4617 0.65 63.9 <mdl <mdl Grusen Gr1 (3)

Moberg Mo6 (11) b 4189 <mdl 4.9

17366 <mdl 0.60

<mdl –

0.32 <mdl <mdl 40.2

0.22 80.3 <mdl 0.08 Bornite Grusen Gr2 (5)

1240 <mdl 0.013 2611

a 0.24 0.01 0.01 0.61 2.3

0.03 a 0.02 4.8 a 0.01 128

0.43 7.9 0.13 5.1 a Grusen Gr3 (3)

0.09 16.2 0.02 0.13 Tjøstølﬂaten Tj1 (5)

0.25 0.01 a 18.0 <mdl 143

12.3 1.6 0.21 0.32 4.8 9.3 0.10 29.7 0.45 43.4 1.3 – mineral Glava Gl99.5 (10)

403 a 0.02 2224 0.10 402 0.20 – Cretaceous skarn, epithermal and porphyry deposits (SE Europe) Baita Bihor BBH13F (6)

0.13 9.9 0.01 – chemistry Baita Bihor BBH13B (6)

1.1 11.8 0.02 – Baita Bihor BBH19CB (6)

1.1 0.8 0.05 1.2 0.91 <mdl 16.4 a 7.8 0.09 147

0.38 0.09 <mdl 1.1 1.0 0.61 0.10 4.3 0.15 54.0 0.06 2.7 0.04 – Baita Bihor BBH20A (6)

0.19 40.2 40.1 a 6.9 0.56 – Baita Bihor BB3 (11)

<mdl 7666

1.9 0.02 0.02 1.1 1.2 <mdl <mdl 11.8

<mdl 2.2 0.07 <mdl Baita Bihor BB170B (10)

1262 <mdl 0.06

<mdl <mdl <mdl –

0.08 <mdl 0.14

15.1 <mdl 209

0.33 85.7 0.02 <mdl Baita Bihor BB171 (8)

0.35 82.3 <mdl <mdl Ocna de Fier CuSI (6)

1531 <mdl <mdl 1505

<mdl <mdl <mdl –

0.09 <mdl <mdl 43.0 a 0.04 235

0.14 43.5 0.13 – Ocna de Fier CuPP SI (8)

0.67 0.56 0.06 0.96 8.0 a <mdl 0.08

8.0 a 0.06 0.48 1916 a 0.06 1046 0.67 148 0.26 0.003 Sasca Montana SM2 (6)

77.1 105 1.5 4.3 Chelopech CPK3 (12)

2.0 a 75.3 6.2 – Radka R449 (4)

1.1 0.01 47 a 6.4 a 0.1 1.2 0.20 151 a 11 a 299

0.44 1.5 1.0 0.16 0.24 <mdl Elatsite Els (6)

0.32 27.4 0.09 – Iron oxide – copper – gold (Gawler Craton, South Australia) Olympic Dam OD1 (10)

0.48 <mdl <mdl 1.1

0.08 <mdl <mdl 3.4

<mdl 36.8 a 0.46 0.13 18.8 0.20 9.5 <mdl – Number in brackets indicates No. of individual spot analyses.

70.5 <mdl <mdl 204

0.52 233 a 0.03 0.82 0.03

Mean minimum detection limits, mean standard deviations, maxima, minima, mean precisions (%) and mean stage error (%) are given in Electronic Appendix A , together with supplementary data for Fe and Zn not included in this table.

a Time-resolved proﬁle indicates presence of inclusions in some spot analyses; – not analyzed. b No co-existing chalcocite. c Anomalous, low-Fe bornite.

Table 3 Mean concentrations for minor and trace elements in Cu

S sulﬁdes and chalcopyrite determined by LA-ICP-MS (ppm).

S sulﬁdes N.J. Late Proterozoic metamorphosed veins (Norway)

Cook

0.13 0.02 <mdl Tinnsja˚ Tsj1a (3)

Tinnsja˚ Tsj1 (6)

1.46 0.06 <mdl Tinnsja˚ Tsj2 (11)

1.6 0.02 4.1 0.25 5.7 a 0.05 0.035 et al.

<mdl <mdl <mdl Tinnsja˚ Tsj7 (6)

Tinnsja˚ Tsj6 (5)

<mdl 0.04 <mdl Geochi Tinnsja˚ Tsj8 (5)

<mdl 0.03 <mdl Tinnsja˚ Tsj9 (3)

2.7 0.08 <0.01 mica Tinnsja˚ Tsj14 (3)

2.1 0.11 0.01 Moberg Mo1 (5)

0.07 460 0.04 21.8 a et Moberg Mo3 (6)

183 0.01 1.3 a Cosmoch Grusen Gr1 (3)

0.04 27.3 0.01 1.0 a Grusen Gr2 (2)

5.0 <mdl 0.02 Grusen Gr3 (8)

0.15 221 0.05 31.4 a imica Cretaceous skarn deposits (SE Europe)

0.55 5.1 a 302

0.10 0.26 0.97 a <mdl

0.15 42.4 a 0.13 21.6 0.08 185

Baita Bihor BB3bn (17)

2.7 0.14 0.005 Acta Ocna de Fier CuPP SI (4)

0.19 35.6 0.26 <mdl 75 Chalcopyrite

15.3 a 1.8 8470 a 0.15 1.5 <mdl

0.12 0.15 0.4 975 a 0.42 383

(2011) Cretaceous skarn deposits (SE Europe)

20.7 0.43 0.27 <mdl <mdl Baita Bihor BB171 (6)

Tinnsja˚ Tsj12 (3)

16.6 4.5 <mdl <mdl 6473–64 Ocna de Fier CuPP SI (2)

0.16 39.7 a <mdl

3.4 6.6 0.03 <mdl Olympic Dam OD1 (4)

0.83 0.16 0.66 1.8 0.18 8.7 1.0 1.5 <mdl – 96 Number in brackets indicates no. of individual spot analyses. Mean minimum detection limits, mean standard deviations, maxima, minima, mean precisions (%) and mean stage error (%) are given

in Electronic Appendix A Electronic, together with supplementary data for Fe and Zn not included in this table. a Time-resolved proﬁle indicates presence of inclusions in some spot analyses; – not analyzed.

Bornite mineral chemistry

Fig. 4. Histograms (semi-logarithmic scale) illustrating variation in concentrations of (a) Ag, (b) Bi, (c) Se, and (d) Te in bornite from the diﬀerent deposits in the sample suite.

Fig. 5. Histograms (semi-logarithmic scale) illustrating variation in concentrations of (a) Ag, (b) Bi, (c) Se, and (d) Te in chalcocite and digenite from the diﬀerent deposits in the sample suite.

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

Fig. 6. Representative time-resolved LA-ICP-MS depth profiles for bornite. From left, the background count is 30 s, followed by 60 s ablation time, which is integrated. Parts-per-million concentrations are given for selected elements. (a). Bornite from Moberg; note flat spectra for Ag and Bi, but also for Pb, Se and Te. (b) Bornite from Moberg; note small peaks on profile for Pb reflecting mineral inclusions. (c) Bornite from Baita Bihor; note flat spectra for many elements, including Tl. (d) Bornite from Ocna de Fier. (e) Bornite from Chelopech. (f) Bornite from Elatsite. (g) Bornite from Elatsite. (h) Bornite from Olympic Dam.

6487 In both these samples, Au shows smooth LA-ICP-MS

Bornite mineral chemistry

downhole proﬁles. The data suggest that Au is concentrated in Cu-sulﬁdes over coexisting bornite.

4.2.4. Lead and thallium Concentrations of up to several hundred ppm Pb have been measured in bornite ( Table 2 ). In most samples values vary from point to point within a given sample over several orders of magnitude. This characteristic, as well as the roughness of the depth profiles and pronounced spikes (e.g., Fig. 6 b), suggests that little of the measured Pb is likely to be in the sulfide structure, but is rather contributed by microinclusions of galena and sulfosalts. We exclude any analytical interference since measured 208 Pb (in cps) is only two orders of magnitude higher than 205 Tl. Our interpretation is corroborated by the presence of exsolved galena– (clausthalite) solid solution in several specimens. In Sasca Montana, Radka, Elatsite and especially Chelopech, however, the majority of profiles are flat, suggesting that he measured Pb is in solid solution (e.g., Fig. 6 e and f). In the four exceptions consistent Pb concentrations of tens or hundreds of ppm are seen with flat downhole profiles. In deposits where irregular profiles dominate, however, flat profiles are also obtained for some spots, e.g., Moberg and Baita Bihor ( Fig. 6 a and c).

Thallium patterns mimic those of Pb throughout the dataset but at much lower concentrations (typically <1 ppm). However, values >1 ppm are recorded in bornite from Sasca Montana and Chelopech; the latter giving as much as 19.4 ppm Tl in individual spot analyses. In such cases, the time-resolved depth proﬁles are ﬂat (e.g., Fig. 6 c), but this may also be interpreted as due to the presence of homogeneously-distributed Pb–Tl–sulfosalts.

4.2.5. Cobalt and nickel Cobalt and Ni concentrations in bornite and chalcocite are typically around the minimum detection limits (mdl). In sample BB13B from Baita Bihor, where inclusions of Ni–(Co)-bearing phases are observed, anomalous concentrations in some points ( Electronic Appendix A) are tied to such inclusions. Evidence of Co and Ni incorporation

in bornite is seen only from the Sasca Montana sample, Fig. 7. Representative time-resolved LA-ICP-MS depth proﬁles in which reasonably smooth time-resolved downhole pro- for hypogene chalcocite/digenite from (a) Grusen, (b) Moberg, and

60 s ablation time, which is integrated. Parts-per-million concen-

62 ppm Ni (range 28–102 ppm) are noted. In line with the trations are given for selected elements. Note flat profiles for many behavior of Co and Ni in other common sulfides, we as-

elements, including Mo, U and Pb, suggesting residence (at least in sume there must be a degree of substitution of the two ele-

part) in solid solution.

ments into the Fe site within bornite.

4.2.6. Gallium, germanium and indium Concentrations of Ga in bornite are low to extremely

Bornite from Sasca Montana, Radka and Chelopech is low (<0.5 ppm if not <mdl) in all samples except those from

also enriched in Ge (means 31, 20 and 6 ppm, respectively), Sasca Montana, Radka and Chelopech. In Sasca Montana

again with smooth proﬁles; Fig. 6 f), concentrations <1 ppm and Radka, the smooth ablation depth proﬁles and small

are typical of the other samples. Both Ga and Ge are typi- relative variation in concentrations are suggestive of solid

solution, with mean concentrations of 22 and 13 ppm, trations cannot be quantiﬁed with full conﬁdence because respectively. Erratic higher Ga concentrations in other sam-

of isotopic interference ( Danyushevsky et al., 2011 ). ples (e.g., some analyses from Chelopech) are best attrib-

Our data show that bornite and chalcocite are very poor uted to ﬁne inclusions of discrete Ga-bearing phases (e.g.,

hosts for In; concentrations rarely exceed a couple of ppm.

N.J. Cook et al. / Geochimica et Cosmochimica Acta 75 (2011) 6473–6496

Minor and trace elements in bornite and