Earth and Planetary Science Letters 355-356 (2012) 327340Contents lists available at SciVerse ScienceDirectEarth and Planetary Science Letters0012-82

http://d

n Corr

E-mjournal homepage: www.elsevier.com/locate/epslPartitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb,and Bi between sulfide phases and hydrous basanite meltat upper mantle conditionsYuan Li n, Andreas Audetat

Bayerisches Geoinstitut, Universitat Bayreuth, 95440 Bayreuth, Germanya r t i c l e i n f o

Article history:

Received 15 December 2011

Received in revised form

5 July 2012

Accepted 8 August 2012Editor: T. Elliotupper mantle in different tectonic settings. The silicate melt was produced by partial melting of aAvailable online 26 October 2012

Keywords:

experimental

partitioning

sulfide

silicate melt

upper mantle1X/$ - see front matter & 2012 Published by

x.doi.org/10.1016/j.epsl.2012.08.008

esponding author. Tel.: 49 0921 553721; faail address: yuan.li@uni-bayreuth.de (Y. Li).a b s t r a c t

The partitioning of 15 major to trace metals between monosulfide solid solution (MSS), sulfide liquid

(SL) and mafic silicate melt (SM) was determined in piston-cylinder experiments performed at 1175

1300 1C, 1.53.0 GPa and oxygen fugacities ranging from 3.1 log units below to 1.0 log units above thequartzfayalitemagnetite fO2 buffer, which conditions are representative of partial melting in the

natural, amphibole-rich mantle source rock, resulting in hydrous (B5 wt% H2O) basanitic melts similarto low-degree partial melts of metasomatized mantle, whereas the major element composition of the

starting sulfide (B52 wt% Fe; 39 wt% S; 7 wt% Ni; 2 wt% Cu) was similar to the average composition ofsulfides in this environment. SL/SM partition coefficients are high (Z100) for Au, Ni, Cu, Ag, Bi,intermediate (1100) for Co, Pb, Sn, Sb (7As, Mo), and low (r1) for the remaining elements. MSS/SMpartition coefficients are generally lower than SL/SM partition coefficients and are high (Z100) for Ni,Cu, Au, intermediate (1100) for Co, Ag (7Bi, Mo), and low (r1) for the remaining elements. Mostsulfidesilicate melt partition coefficients vary as a function of fO2, with Mo, Bi, As (7W) varying by afactor 410 over the investigated fO2 range, Sb, Ag, Sn (7V) varying by a factor of 310, and Pb, Cu, Ni,Co, Au, Zn, Mn varying by a factor of 310. The partitioning data were used to model the behavior of Cu,

Au, Ag, and Bi during partial melting of upper mantle and during fractional crystallization of primitive

MORB and arc magmas. Sulfide phase relationships and comparison of the modeling results with

reported Cu, Au, Ag, and Bi concentrations from MORB and arc magmas suggest that: (i) MSS is the

dominant sulfide in the source region of arc magmas, and thus that Au/Cu ratios in the silicate melt and

residual sulfides may decrease with increasing degree of partial melting, (ii) both MSS and sulfide liquid

are precipitated during fractional crystallization of MORB, and (iii) fractional crystallization of arc

magmas is strongly dominated by MSS.

& 2012 Published by Elsevier B.V.1. Introduction

Chalcophile and siderophile elements are important tracers toreconstruct core-formation and mantle (-crust) differentiationprocesses in the Earth (e.g., Newsom et al., 1986; Yi et al., 2000;Righter, 2003), and all form economically valuable ore deposits(e.g., Kesler, 1994; Robb, 2005). Both chalcophile and siderophileelements tend to partition into sulfide phases relative to silicatemelt, hence sulfidesilicate melt partition coefficients need to betaken into account when constraining the geochemical behaviorof these elements in magmatic systems that are sulfur-bearing.Sulfides are actually common in the upper mantle (Lorand et al.,1989, 1990; Szabo and Bodnar, 1995; Shaw, 1997), in mid-oceanElsevier B.V.

x: 49 0 921 55 3769.ridge basalts (MORB; Mathez, 1976; Peach et al., 1990; Jenneret al., 2010), in arc basalts (Metrich et al., 1999; de Hoog et al.,2001; Di Muro et al., 2008), and in many intermediate and felsicderivatives of these magmas (Jenner et al., 2010; Wallace andEdmonds, 2011), hence in all these environments the effect ofsulfidesilicate melt partitioning should be considered. Studies onmantle xenoliths and orogenic peridotites have shown that thedominant sulfide phase in the upper mantle is monosulfide solidsolution (MSS) (e.g., Lorand et al., 1989, 1990; Szabo and Bodnar,1995; Shaw, 1997), followed by Cu-rich, interstitial sulfides thatare interpreted to have been introduced during periods of mantlemetasomatism (Alard et al., 2000; Lorand and Alard, 2001; Luguetet al., 2007).

Previous experimental studies dealing with sulfidesilicate meltpartitioning have focused mostly on PGE and Au (Fleet et al., 1991;Bezmen et al., 1994; Fleet et al., 1996, 1999; Crocket et al., 1997),whereas only few data are available for V, Mn, Co, Ni, Cu, Zn, As, Mo,

www.elsevier.com/locate/epslwww.elsevier.com/locate/epsldx.doi.org/10.1016/j.epsl.2012.08.008dx.doi.org/10.1016/j.epsl.2012.08.008dx.doi.org/10.1016/j.epsl.2012.08.008mailto:yuan.li@uni-bayreuth.dedx.doi.org/10.1016/j.epsl.2012.08.008

Fe3/Fe

*DVoliv/SM

logfO

2DFM

QlogfS

2

SS

0.137

0.03

n.a.

8.45

1.00

0.15

SSSL

0.287

0.03

n.a.

6.93

0.42

1.35

SSSL

0.297

0.02

n.a.

6.65

0.70

1.69

n.a.

n.a.

7.10

1.00

n.a.

n.a.

n.a.

7.10

0.10

n.a.

n.a.

n.a.

8.70

1.50

n.a.

MSS

n.a.

n.a.

7.21

0.10

n.a.

0.227

0.02

n.a.

6.98

0.37

1.27

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0.217

0.03

n.a.

7.00

0.35

1.16

n.a.

n.a.

n.a.

n.a.

n.a.

SL

n.a.

n.a.

n.a.

n.a.

n.a.

0.057

0.01

0.09577

0.0123

9.78

2.10

1.18

0.297

0.02

n.a.

6.27

0.91

1.89

0.237

0.02

n.a.

6.93

0.25

1.30

n.a.

0.1637

0.004

10.28

3.10

2.36

SSL

0.337

0.02

n.a.

6.21

0.97

2.02

0.197

0.03

n.a.

5.33

0.62

1.98

n.a.

n.a.

n.a.

n.a.

n.a.

;SL:

sulfideliquid;n.a:notanalyze

d.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340328Ag, Sn, Sb, W, Pb, and Bi (Rajamani and Naldrett, 1978; Li and Agee,2001; Gaetani and Grove, 1997; Wood et al., 2008; Mengason et al.,2011). Most of these studies were performed with dry silicate meltsat 1 atm, and virtually all involved only sulfide liquid, which is atodds with the dominance of MSS in the source region and laterevolutionary stages of arc magmas (see below). An exception is a fewstudies concerning the partitioning of Au, Ag, and Cu betweenpyrrhotite and felsic silicate melt (Lynton et al., 1993; Jugo et al.,1999; Simon et al., 2008). Thus, there is a great need for sulfidesilicate melt partition coefficients at conditions relevant to the uppermantle.

In this contribution we report a coherent set of partitioncoefficients of V, M, Co, Ni, Cu, Zn, Mo, As, Sn, Sb, Ag, Au, W, Pb,and Bi between coexisting MSS, sulfide liquid, and hydroussilicate melts representative of partial melts generated in meta-somatized upper mantle. To exemplify the large number ofpotential applications we use our results to model the influenceof sulfides on the behavior of Cu, Ag, and Au during meltproduction in the upper mantle, and during fractional crystal-lization of primitive mantle melts in the lower crust.Table

1Overview

ofexperimentalco

nditionsandru

nproducts.

Exp.ID

T(1C)

P(G

Pa)

Duration(hours)

Startingmaterial

Capsu

leIm

posedfO

2Quench

phases

LY01

1175

1.5

24

AG4S03su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOliv12%SM

M

LY04

1185

1.5

20

AG4S03su

lfide

double

Pt 9

5Rh05Oliv

ReReO

CpxAmphOliv10%SM

M

LY08

1185

1.5

20

AG4S03su

lfide

double

Pt 9

5Rh05Oliv

ReReO

CpxAmphOliv20%SM

M

LY12

1300

1.5

0.5

AG4S03su

lfide

double

Pt 9

5Rh05Oliv

FeOFe

3O4

SM

withquench

etexture

SL

LY15

1200

1.5

2AG4S03su

lfide

MDC

NiNiO

SM

withquench

etexture

MSS

LY16

1200

1.5

0.7

AG4S03su

lfide

MDC

CoCoO

SM

withquench

etexture

SL

LY17

1190

1.5

0.6

AG4S03su

lfide

MDC

NiNiO

SM

withquench

etexture

SL

LY19

1185

1.5

15

AG4S03su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOlivSM

MSS

LY20

1185

1.5

8AG4S03su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOlivSM

MSS

LY22

1185

1.5

2AG4S03su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOlivSM

MSS

LY23

1185

1.5

15

AG4S04su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOlivSM

MSS

LY24

1185

1.5

15

AG4S02su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOliv7%SM

MSS

LY25

1185

1.5

15

AG4S05su

lfide

Pt 9

5Rh05Oliv

-CpxAmphOlivSM

MSS

LY26

1200

1.5

40

AG4S06su

lfide

Pt 9

5Rh05graphiteOliv

-CpxOlivSM

MSSSL

LY28

1200

1.5

42

AG4S02su

lfide

double

Pt 9

5Rh05Oliv

MnOMn3O4

CpxOlivSM

MSSSL

LY29

1200

1.5

44

AG4S06su

lfide

double

Pt 9

5Rh05Oliv

ReReO

CpxOlivSM

MSSSL

LY30

1200

1.5

21

AG4S02su

lfide

FegraphiteOliv

-CpxOlivSM

MSSSL

LY31

1200

1.5

30

AG4S02su

lfide5%CaSO4

Pt 9

5Rh05Oliv

-CpxOlivanhydriteSM

MS

LY32

1250

2.5

30

AG4S02su

lfide

Pt 9

5Rh05Oliv

-CpxOlivSM

MSSSL

LY33

1300

3.0

25

AG4S02su

lfide

Pt 9

5Rh05Oliv

-CpxOlivSM

MSSSL

MDC:modifieddouble

capsu

le;Cpx:clinopyroxene;Oliv:olivineorolivinecapsu

le;Amph:amphibole;SM:silicate

melt;MSS:monosu

lfideso

lidso

lution

nVanadium

partitionco

efficientbetw

eenolivineandsilicate

melt.

2. Experimental methods

2.1. Starting materials

In all experiments we used a hornblende-rich, natural mantlerock as starting material to which 58 wt% synthetic FeNiCusulfide was added. The hornblendite stems from a hydrous vein inorogenic peridotite of the French Pyrenees (Fabri es et al., 2001;for composition, see supplementary Table 1) and was kindlyprovided by Sebastian Pilet, who used the same starting materialto experimentally reproduce alkaline magmas (AG4 in Pilet et al.,2008). The major element composition of the synthetic sulfide(50.054.4 wt% Fe; 38.341.1 wt% S; 6.87.7 wt% Ni; 1.83.0 wt%Cu; supplementary Table 1) is similar to that of typical sulfides inmetasomatized lithospheric mantle, which contain 3841 wt% S,5054 wt% Fe, B7.0 wt% Ni and 1.83.0 wt% Cu (Lorand, 1989;Szabo and Bodnar, 1995; Shaw, 1997; Lorand and Alard, 2001).Between 50 and 3400 ppm of Co, Ni, Cu, Zn, Mo, As, Sn, Sb, Ag, W,Au, Pb, and Bi were added to the synthetic sulfide (supplementaryTable 1). Five different sulfide compositions were synthesizedfrom mixtures of pure metals and sulfur powder (99.99%) inevacuated silica glass tubes at 1200 1C as follows. About 0.5 g ofthe mixture was added into silica tubes of 6 mm O.D. and 3.6 mmI.D. which had previously been sealed on one end using ahydrogenoxygen torch. A neatly fitting silica rod of 2 cm lengthwas then placed above the mixture to prevent loss of startingmaterials during subsequent evacuation to o105 bar and seal-ing with the hydrogenoxygen torch. In order to avoid evapora-tion of sulfur during sealing, the sample-containing bottom of thesilica tube was cooled by wet tissues. Finished silica tubes wereput into the furnace and heated from room temperature to 600 1Cwithin 1 h and kept at this temperature for 2 h. Then thetemperature was increased to 1200 1C within 1 h and kept therefor another 2 h. The samples were quenched by dropping thesilica glass tubes into cold water. The run products were opticallyhomogeneous, showing no evidence for immiscibility at hightemperature or exsolution during the quench, and compositionalhomogeneity with respect to major and trace element contentswas confirmed by electron microprobe and laser-ablationinductively-coupled-plasma mass-spectroscopy (LA-ICP-MS).Manganese and vanadium were introduced by the hornblenditestarting material, except for runs LY12 and LY16 to which 0.10.3 wt% V were added in form of V2O5.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340 3292.2. Sample capsules and control of fO2

Several capsule configurations were used to impose differentoxygen fugacities on the samples (Table 1). In all setups thestarting materials were loaded into San Carlos olivine capsules(wall thickness 1 mm) in order to restrict interactions of thesulfides with the noble metal capsules to a minimum. In someruns (LY01,19-25,31-33) the olivine capsule was placed directlyinto a Pt95Rh05 capsule and the oxygen fugacity was kept atintermediate values by the composition of the starting materials.In this setup fO2 was not buffered, but was measured after the runby Mossbauer spectroscopy (see below).

Reducing conditions were obtained in three different ways. Inone run (LY26) the olivine container was loaded into a graphitecapsule that itself was placed into a Pt95Rh05 capsule. In run LY30a similar graphite capsule was placed into an iron capsule thatsealed mechanically under high pressure. Another four experi-ments (LY12, LY15, LY16, and LY17) were performed with amodified double capsule setup similar to that described in Baliet al. (2010). In this method, a small inner Pt95Rh05 capsulecontaining the olivine capsule plus the starting mix was loadedinto outer capsules made of Ni or Co, and the space between wasfilled with corresponding oxides (NiO and CoO) and water. Thefirst several experiments performed with a duration of 20 h allfailed because the sulfide reacted to a volatile phase producing alarge cavity in the sample. Raman spectroscopic analysis of fluidinclusions trapped in the olivine capsule shows that the principalcomponents of the fluid phase are H2S and H2O. This suggests thathydrogen diffusing into the inner capsule continuously reactedwith the sulfide and silicate to form H2S and H2O. After a few triesit was clear that the run duration had to be reduced to about 2 hin order for significant amounts of hydrogen to diffuse in and thesulfide not getting exhausted.

To obtain relatively high oxidation states a conventionaldouble capsule setup (Chou, 1987) was used. The olivine contain-ers were welded into small inner Pt95Rh05 capsules, which wereloaded together with buffer materials plus H2O into largerPt95Rh05 capsules (LY04, 08, 28, 29). Because the silicate meltsin these experiments are fluid-undersaturated the oxygen fuga-city attained in the sample is considerably lower than that in theexternal buffer (see below). Thus, only strongly oxidizing buffers(ReReO, Mn3O4Mn2O3) were used. In one run (LY30) a highoxygen fugacity was achieved by adding B5 wt% anhydrite to thestarting mixture and welding the olivine capsule directly into aPt95Rh05 capsule.

2.3. High temperature and pressure equipment

All experiments were conducted at 1.53.0 GPa and 11751300 1C in end-loaded, solid media piston cylinder apparatususing 0.5 in. diameter MgONaCl assemblies with stepped gra-phite heaters. The hot piston-in method was used to pressurizethe assembly. Temperature was monitored by PtPt90Rh10(S-type) thermocouples with an estimated temperature uncer-tainty of 710 1C. A friction correction of 5% was applied to thenominal pressure based a bracketing of the quartzcoesite transi-tion at 790 1C and using the data of Bose and Ganguly (1995) asreference. The experiments were quenched by switching off theelectrical power.

2.4. Analytical methods

2.4.1. Electron microprobe

Major elements in sulfide liquid, MSS, and quenchable silicatemelts were measured with a JEOL JXA8200 microprobe. Theanalyses were performed in wavelengthdispersive mode, and aPAP matrix correction was applied to the raw data. Sulfideswere analyzed with 20 kV acceleration voltage and 20 nA beamcurrent, whereas quenched silicate melts were analyzed with15 kV/10 nA. A defocused beam of 30 mm diameter was used forall the standardizations and sample measurements. Both naturaland synthetic standards were used to calibrate the instrument.For sulfide analysis, Fe and S were calibrated on a syntheticpyrrhotite with well-known Fe:S ratio, Ni, Co, and Cu werecalibrated on pure metals, and O was calibrated on magnetite.For silicate melts, Na was calibrated on albite, Ca on wollastonite,K on orthoclase, Ti and Mn on ilmenite, Si on enstatite, Mg onforsterite, Al on spinel, P on GaP, Fe on metallic Fe, and Cl onvanadinite. Sulfur concentrations in reduced and oxidized glasseswere calibrated on pyrrhotite and barite, respectively.

For sulfide liquids, which unmixed into several phases at thescale of 10 mm during quenching (Fig. 1(f), the use of a 30 mmdefocused electron beam resulted in well reproducible results.In contrast, hydrous silicate melts displaying a coarse quenchtexture (LY12, LY15, LY16, LY17) could not be analyzed reliably byelectron microprobe. In these samples, the major element com-position was measured by LA-ICP-MS data and the resultsnormalized to 100 wt% major element oxides.

2.4.2. LA-ICP-MS

Major and trace elements of sulfide liquid, MSS, non-quenchable silicate melt, and silicate minerals were analyzed byLA-ICP-MS, using a Geolas M 193 nm ArF Excimer laser (Coherent/Lambda Physik) attached to an Elan DRC-e quadrupole massspectrometer (Perkin Elmer Instruments). The laser was operatedat a frequency of 10 Hz and energy of 80 mJ for silicates; at afrequency of 7 Hz and energy of 70 mJ for sulfides. The laser beamsize ranged from 10 mm to 80 mm and was chosen as large aspossible to get an average composition of heterogeneouslyquenched sulfide liquid and silicate melt, and to obtain lowdetection limits. The sample chamber was flushed with He at arate of 0.4 L/min, to which 5 ml/min H2 was added on the way tothe ICP-MS. Dwell times were 10 ms for the isotopes 23Na, 25Mg,27Al, 29Si, 39K, 42Ca, 49Ti, 51V, 55Mn, 57Fe, 59Co, 62Ni, 65Cu, 75As93Nb, 98Mo, 107Ag, 121Sb, 184W, 208Pb, and 209Bi, and 20 ms for197Au. NIST SRM 610 glass was used as external standard for allanalyses, whereas Al and Fe determined by electron microprobewere used as internal standard for silicates and sulfides, respec-tively. Tests on a synthetic monosulfide solid solution standardkindly provided by Lesley Rose and Jim Brenan (MSS-5) revealedgood agreement between LA-ICP-MS measurements and solutionICP-MS data (r10% deviations for Ni, Cu, Sb, and Pb; r15% forAu and Bi, and 20% for Ag). A similar test on the PGE- and Au-bearing Laflamme Po724-T3 pyrrhotite standard (Sylvester et al.,2005) returned an agreement between measured and certifiedconcentration within 3%. The uncertainties arising from internaland external standardization are thus considered better than1520% for all elements significantly above the detection limit.

2.4.3. Mossbauer spectroscopy

Samples containing relatively large volumes of quenchedsilicate melt were measured using 57Fe Mossbauer spectroscopyto determine Fe3/SFe in the silicate melt. The samples wereprepared as doubly polished thin sections with an effectivethickness of about 500 mm. Lead foils featuring holes of 200 or400 mm in diameter were used to restrict the irradiation to areasof pure silicate melt. Spectra were collected at room temperaturein transmission mode on a constant acceleration Mossbauerspectrometer with a 50 mCi 57Co source in a 6 mm Rh matrix.The velocity scale was calibrated relative to a 25 mm thick a-Fefoil at room temperature. Mirror image spectra were recorded

Fig. 1. Petrography of experimental run products. (a) BSE image of sample LY28 (1200 1C, 1.5 GPa) showing partially melted silicate starting material and sulfide phases(bright globules) contained in an olivine capsule (dark gray). Silicate melt (light gray) accumulated at the top of the charge, which is located on the left. (b) BSE image of the

upper portion of sample LY26 (1200 1C, 1.5 GPa) showing pure silicate melt at the top and sulfides plus crystals of olivine (dark gray) intermixed with silicate melt furtherbelow. (c) Reflected light image of the bottom part of hydrous sample LY16 (1200 1C, 1.5 GPa), which shows one exposed sulfide globule (bright) and several epoxy-filledvapor bubbles (dark globules at the rim of the charge) in non-quenchable silicate melt. (d) Transmitted light image of aqueous fluid inclusions in the olivine liner of sample

LY15 (1200 1C, 1.5 GPa). (e) Reflected light image of coexisting MSS, sulfide liquid and silicate melt in sample LY04 (1185 1C, 1.5 GPa). The non-quenchable sulfide liquidforms a thin mensicus on top of MSS. (f) Reflected light image of a large globule of sulfide liquid at the bottom of sample LY12 (1300 1C, 1.5 GPa). The exsolution features inthe interior of the globule are characteristic of sulfide liquid.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340330over 512 channels with a velocity range of 75 mm/s. Eachspectrum took at least 2 days to collect and was fitted to Lorentzianline shapes using the Recoil software package. The fitted Mossbauerspectra showed two strong absorbance doublets corresponding toFe2 and another shoulder corresponding to the absorption of Fe3 .The Fe3/SFe ratios were derived from the calculation of areafraction of Fe3 in the total Fe area. Details regarding this techniquecan be found in McCammon (2004).3. Results

3.1. Sample petrography

The experimental conditions and obtained run products are listedin Table 1, and representative textures are shown in Fig. 1. In runsperformed below 1200 1C, B510% silicate melt was produced at thetop of the charge (Fig. 1a, b). The rest recrystallized mainly toamphibole, clinopyroxene, and olivine. In runs performed atZ1200 1C, B1050% silicate melt was produced and the restrecrystallized to clinopyroxene and olivine. The starting rock powdercontains B2 wt% H2O stored in amphibole (F and Cl contents arevery low; Fabries et al., 2001), thus decomposition of amphiboleduring the run released significant amounts of H2O into the silicatemelt. Based on the difference of EMPA totals to 100 wt% the watercontent of the silicate melt produced in runs without H2O-containingdouble capsules is estimated at B5 wt%.

The four reduced experiments performed in H2O-bearing doublecapsules (LY12, LY15, LY16, and LY17) show a different texture.Because the incoming hydrogen reacted with silicates to produceH2O, the silicate melt became very water rich and saturated in anaqueous H2OH2S fluid, as demonstrated by numerous cavities in therecovered samples (Fig. 1c) and the presence of fluid inclusions in thesurrounding olivine capsules (Fig. 1d). Due to the high water contentthe entire starting rock powder plus variable amounts of thesurrounding olivine capsule were melted in these runs, and thesilicate melts were not quenchable (Fig. 1c). Experimental data onH2O solubility in the system Mg2SiO4SiO2H2O at 1.5 GPa(Nakamura and Kushiro, 1974) suggest that these melts containedZ20 wt% dissolved H2O.

Table 2Partition coefficients (DMSS/SM) between MSS and silicate melt.

Exp. ID V Mn Co Ni Cu Zn As Mo Ag Sn Sb W Au Pb Bi

LY01 n.d 0.24 69 790 450 0.55 0.50 1.78 42 0.09 0.06 o0.01 160 0.10 1.61s 0.02 5 150 50 0.07 o0.5 0.30 6 0.01 0.00 40 0.02 0.3LY04 0.02 0.19 46 510 340 0.42 0.07 0.42 31 0.10 0.02 0.20 60 0.11 0.8

1s 0.00 0.01 2 80 30 0.08 0.00 0.03 3 0.02 0.00 0.06 10 0.01 0.1LY08 0.03 0.14 46 270 370 0.39 o0.5 0.60 68 o0.05 o0.06 o0.01 90 0.12 2.21s 0.00 0.01 3 50 40 0.10 0.10 22 40 0.02 1.3LY15 0.02 0.19 33 260 200 0.33 0.31 0.42 23 0.12 0.02 0.00 n.d. 0.07 0.7

1s 0.00 0.00 2 50 40 0.03 0.01 0.02 6 0.00 0.00 0.00 0.01 0.1LY17 0.02 0.17 25 230 230 0.19 0.15 0.20 25 0.07 0.08 0.06 n.d. 0.12 0.9

1s 0.00 0.00 3 90 190 0.03 0.03 0.01 15 0.01 0.02 0.01 0.04 0.4LY19 0.03 0.22 40 580 350 0.27 o0.05 0.62 64 0.09 0.03 0.01 310 0.09 1.11s 0.01 0.01 3 100 30 0.05 0.07 12 0.00 0.01 0.01 30 0.02 0.2LY20 0.02 0.21 57 1240 410 0.30 o0.04 0.35 34 0.04 0.01 0.07 140 0.07 0.51s 0.00 0.01 3 200 140 0.06 0.02 7 0.10 0.00 0.06 20 0.01 0.1LY22 0.03 0.21 41 510 340 0.24 o0.04 0.42 76 0.07 0.02 0.31 140 0.09 1.41s 0.01 0.03 2 40 30 0.05 0.05 18 0.01 0.00 0.18 80 0.02 0.5LY23 0.02 0.20 37 530 330 0.24 o0.12 0.62 69 o0.1 0.02 o0.02 210 0.09 1.51s 0.01 0.01 1 70 60 0.02 0.04 6 0.00 20 0.01 0.2LY24 0.03 0.20 39 490 250 0.19 o0.5 0.79 28 o0.1 0.02 0.01 190 0.05 0.81s 0.01 0.02 1 50 20 0.02 0.02 7 0.00 0.00 40 0.02 0.1LY25 0.06 0.22 33 340 270 o0.5 0.17 0.68 28 o0.6 0.23 0.14 200 0.13 0.91s 0.04 0.09 2 60 30 0.01 0.06 4 0.02 0.01 60 0.05 0.2LY26 0.13 0.18 47 830 420 0.30 1.09 14.48 67 o1 0.13 o0.03 200 0.24 4.71s 0.00 0.03 2 170 110 0.11 0.11 0.75 19 0.01 70 0.01 1.3LY28 0.02 0.16 39 370 280 0.29 o0.02 0.29 29 o0.2 0.01 0.01 170 0.10 0.61s 0.00 0.01 3 40 20 0.00 0.01 3 0.00 0.00 120 0.00 0.1LY29 0.02 0.14 41 400 300 0.19 0.01 0.64 28 o1 o0.04 o0.02 360 0.10 0.81s 0.00 0.01 1 40 20 0.05 0.00 0.05 2 130 0.02 0.1LY30 0.08 0.17 45 700 260 0.31 1.79 9.99 110 o0.3 0.14 o0.01 140 0.18 8.41s 0.02 0.02 7 170 70 0.05 0.14 1.26 60 0.04 60 0.07 1.9LY31 0.01 0.10 30 340 250 0.21 o0.1 0.21 22 o0.4 o0.2 0.01 220 0.10 1.11s 0.00 0.00 1 50 40 0.01 0.01 8 0.00 20 0.01 0.2LY32 0.05 0.10 33 320 180 0.21 o0.12 0.95 19 o0.24 o0.02 o0.01 190 0.06 0.61s 0.03 0.00 3 20 20 0.01 0.14 3 100 0.01 0.1

n.d.not determined.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340 331The PT conditions of most runs were chosen such that twodifferent sulfide phases were present. One is crystalline MSS andthe other is sulfide liquid (Fig. 1e), both being present asindividual, spherical globules within the charge. MSS quenchesto a homogeneous solid as evidenced by its optical appearanceand chemical homogeneity (Fig. 1e), whereas sulfide liquid is notquenchable and exsolves into an assemblage consisting of FeNi-rich MSS and Cu-rich sulfide (chalcopyrite) (Fig. 1e, f). Where MSSand sulfide liquid are in direct contact with each other, the sulfideliquid is always pointing upward (Fig. 1e). At a constant pressureof 1.5 GPa the phase proportions change from MSS only at 11751185 1C, over MSS sulfide liquid at 11851200 1C, to sulfideliquid only at 1300 1C in good agreement with the phase diagramof Bockrath et al. (2004a; cf. Fig. 4). The slightly higher solidustemperature in our study can be explained by the lower Nicontent of our starting material (78 wt% versus 16 wt% inBockrath et al., 2004a). In runs LY12, LY15, LY16, and LY17, thesulfides agglomerated to a single sphere and sank to the bottomof the olivine capsule. In these runs the extremely hydrous silicatemelt and coexisting fluid phase may have taken up majoramounts of sulfur, which may have led to a change in themetal/sulfur ratio of the residual sulfide. For this reason theseruns are not considered in Fig. 4. Generally, only sulfides andsilicate melts in direct contact with each other were selected foranalysis. Cases in which the phases were separated by mineralswere discarded, e.g., the MSS data in sample LY33.

3.2. Major and trace element content of silicate melt

The major and trace element contents of the silicate melts arelisted in supplementary Tables 2 and 3. From each sample 15 and25 microprobe analyses were performed across the whole area ofsilicate melt. In each of the four samples with non-quenchablesilicate melt five 80 mm-sized Laser-ablation ICP-MS spots werecollected. Major elements are generally reproducible within 5%and trace elements within 10%. All silicate melts are alkaline andbasanitic, consistent with the experimental results of Pilet et al.(2008). The silicate melts of runs LY12, LY15, LY16, and LY17contain considerably more Mg and less Al, Na, and K than theother runs, which is due to the partial dissolution of the olivinecapsule in these experiments.

All measured trace elements were well above the detectionlimit of our LA-ICP-MS and were homogeneously distributed inthe silicate melt, except for run LY17 which shows a relativelylarger range in Cu and Ag concentrations. Dissolved sulfur con-centrations measured by EMPA increase from B0.15 to B1.4 wt%as the oxygen fugacity increases from 3.1 log units below thefayalitequartzmagnetite buffer to 1.0 log units above it (FMQ-3.1 to FMQ1.0). The full data set of sulfur analyses will bereported along with Au concentrations and Au partition coeffi-cients in a separate paper.

3.3. Major and trace element content of sulfide phases

Major and trace element contents in MSS and sulfide liquid arelisted in supplementary Tables 46. Major element abundances inMSS and sulfide liquids are well reproducible both among differentspots analyzed within one globule and among different globulesanalyzed from the same sample. Compared to sulfide liquid, MSS isenriched in Fe and S, while sulfide liquid has higher contents of Cu, Ni,and O. The time-resolved LA-ICP-MS signals demonstrate that bothmajor and trace elements are homogeneously distributed in MSS.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340332Although this is obviously not the case in the unquenchablesulfide liquid, the size of the laser pits and the durations ofanalyses were usually such that by integrating the signals repre-sentative averages could be obtained. In the sulfide liquid ana-lyzed from run LY16 tungsten is concentrated in phases that donot seem to be quench products, as tungsten concentrations inmany other sulfide liquids are below detection limit. These datawere thus rejected. Sn, Sb, and As were below detection limit inMSS grown at relatively oxidizing conditions.

3.4. Partition coefficients

Nernst partition coefficients (D) of major and trace elementswere calculated from their weights in sulfide phases and silicatemelt. The data are tabulated in Tables 2 and 3, and are summar-ized and compared with literature values in Fig. 2. The effect ofoxygen fugacity on the partition coefficients of selected elementsis shown in Fig. 3. In the following sections SL refers to sulfideliquid, MSS refers to monosulfide solid solution, and SM refers tosilicate melt. Literature data are commonly available for sulfideliquidsilicate melt partitioning (SL/SM) and sulfide liquidmonosulfide solid solution (SL/MSS) partitioning, but only rarelyfor monosulfide solutionsilicate melt (MSS/SM) partitioning.

3.4.1. Bi and Pb

The partition coefficient of bismuth between sulfide liquid andsilicate melt, denoted as DSL=SMBi , ranges from 110 to 1130, whereasDMSS=SMBi is about two orders of magnitude lower and ranges from0.6 to 8.4. Both DSL=SMBi and D

MSS=SMBi decrease with increasing oxygen

fugacity. The Bi content of a sulfidesaturated silicate melt thusdepends mainly on the type and amount of sulfide present plus onoxygen fugacity, given that silicate minerals do not accommodateappreciable amounts of Bi (Adam and Green, 2006).

DSL=SMPb ranges from 14 to 48 and is about two orders ofmagnitude higher than DMSS=SMPb , which ranges from 0.1 to 0.24.Both partition coefficients decrease only slightly with increasingoxygen fugacity. Our values of DSL=SMPb are within the range of valuesTable 3Partition coefficients (DSL/SM) between sulfide liquid and silicate melt.

Exp. ID V Mn Co Ni Cu Zn As

LY04 0.06 0.29 29 520 1040 0.94 0.7

1s 0.00 0.01 1 80 90 0.10 0.0LY08 0.02 0.17 39 490 1070 o0.5 o0.51s 0.00 0.00 2 90 70LY12 0.07 0.40 33 210 540 0.98 1.0

1s 0.01 0.01 3 90 140 0.13 0.2LY16 0.05 0.24 28 1010 600 0.77 19.7

1s 0.00 0.01 6 140 160 0.15 5.4LY17 0.02 0.26 23 250 330 0.47 0.3

1s 0.00 0.02 3 100 280 0.10 0.1LY25 0.04 0.20 30 440 800 0.60 1.9

1s 0.00 0.02 1 60 90 0.05 0.7LY26 0.03 0.15 47 1180 720 0.39 10.5

1s 0.01 0.02 2 110 40 0.08 1.0LY28 0.03 0.20 31 470 820 0.54 0.3

1s 0.01 0.04 2 60 40 0.26 0.1LY29 0.02 0.15 35 620 910 0.40 0.3

1s 0.00 0.00 1 60 50 0.02 0.0LY30 0.03 0.17 49 1270 600 0.55 15.4

1s 0.02 0.02 8 260 120 0.10 0.8LY31 0.02 0.21 33 470 740 0.58 0.3

1s 0.00 0.04 6 110 150 0.08 0.1LY32 0.03 0.10 26 450 540 0.28 0.6

1s 0.00 0.01 2 20 40 0.01 0.1LY33 0.02 0.19 32 450 540 0.50 1.1

1s 0.00 0.01 1 20 60 0.04 0.1

n.d.not determined.reported by Lagos et al. (2008) and Wood et al. (2008), but areslightly higher than those reported by Shimazaki and MacLean(1976) from the experiments performed in strongly simplifiedsystems without control on fO2. D

SL=MSSPb is calculated from 130 to

430, which is comparable with a value of 200 reported by Joneset al. (1993) from troilitesulfide liquid partitioning at very redu-cing conditions. Thus, the presence of MSS has only little influenceon the Pb content of coexisting silicate melt, whereas sulfide liquidhas a considerable effect if present in significant quantity.3.4.2. Cu, Ag, and Au

DSL=SMCu and DMSS=SMCu are relatively insensitive to oxygen fugacity,

changing by only about a factor of two over the investigated fO2range. With increasing fO2 the partition coefficients first increase,and then decrease again. The maximum value of DSL=SMCu is located

atBFMQ0.5, and that of DMSS=SMCu atBFMQ1. The DSL=SMCu values

of 9001100 obtained at FMQ0.2 to FMQ0.7 agree well withthe values of 9131383 obtained from coexisting sulfide liquidand MORB (Peach et al., 1990; Francis, 1990) in which system theoxygen fugacity is generally believed to be around FMQ. Our dataare also within the data range reported in Ripley et al. (2002) andGaetani and Grove (1997), but are approximately five timeshigher than the data of Rajamani and Naldrett (1978) andMaclean and Shimazaki (1976) whose experiments were con-ducted at unknown oxygen and sulfur fugacity. DMSS=SMCu rangesfrom 180 to 450, which is comparable to the value of 329 835obtained by Lynton et al. (1993) at oxidizing conditions, but aboutone order of magnitude lower than the data of Jugo et al. (1999),and slightly higher than the data of Simon et al. (2008). All ofthese studies were performed with felsic melts. Our DSL=MSSCu valuesrange from 1.4 to 3, which are within the range of values reportedby Li et al. (1996) and Ballhaus et al. (2001).

DSL=SMAg remains constant at B1000 up to a fO2 of BFMQ0.5,above which it slightly decreases. In contrast, DMSS=SMAg decreasesregularly from B100 to B30 with increasing oxygen fugacity.The DMSS=SMAg values agree well with those of Simon et al.(2008) obtained in felsic melts at NiNiO, and the correspondingMo Ag Sn Sb W Au Pb Bi

0.15 1680 5.9 3.5 0.003 4470 48 350

0.01 110 0.3 0.1 0.00 560 2 10

o0.2 950 3.6 2.2 o0.01 790 28 21070 0.1 0.1 310 1 20

0.67 480 6.0 3.8 0.01 n.d. 32 140

0.13 80 0.7 1.1 0.00 7 80

5.15 420 4.7 9.3 n.d n.d. 10 850

0.34 80 0.8 3.4 5 120

0.13 300 3.2 1.4 0.43 n.d. 24 130

0.01 200 1.0 0.6 0.19 11 70

0.15 1050 6.4 5.2 o0.0 930 45 4200.02 150 1.8 1.7 270 13 110

5.10 920 6.3 8.5 o0.1 2720 31 8001.28 160 0.6 0.7 70 5 140

0.10 890 3.1 2.0 o0.01 3690 27 1700.02 70 0.7 0.3 1630 4 40

0.73 970 3.3 2.1 0.06 4070 27 200

0.03 40 0.1 0.2 0.00 1390 2 20

3.46 970 8.6 11.2 o0.01 2360 45 11301.02 100 0.3 0.5 560 1 60

0.14 610 2.7 1.6 o0.01 5500 23 1300.07 230 0.4 0.2 740 3 30

0.26 450 2.2 1.6 o0.01 2650 14 1100.12 100 0.2 0.3 740 2 20

2.58 470 2.4 2.8 o0.1 2380 24 1200.91 130 0.2 0.4 350 2 10

V Mn Co Ni Cu Zn As Mo Ag Sn Sb W Au Pb Bi0.001

0.01

0.1

1

10

100

1000

10000

DS

L/S

M

V Mn Co Ni Cu Zn As Mo Ag Sn Sb W Au Pb Bi0.001

0.01

0.1

1

10

100

1000

DM

SS

/SM

Fig. 2. Sulfide liquidsilicate melt partition coefficients (DSL/SM) and monosulfidesolid solutionsilicate melt partition coefficients (DMSS/SM) determined in this

study (colored symbols) compared to the literature data (light crosses; entire

range covered by gray bars). For references regarding the literature data, see the

text. Yellow triangles refer to data obtained at oxygen fugacities between FMQ3and FMQ1; red circles refer to data obtained at oxygen fugacities betweenFMQ1 and FMQ0.5; blue diamonds refer to data obtained at oxygen fugacitiesbetween FMQ0.5 and FMQ1. (For interpretation of the references to color inthis figure caption, the reader is referred to the web version of this article.)

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340 333DSL=MSSAg values are consistent with the experiment data of Jones et al.(1993), but are one order of magnitude higher than the valueestimated by Barnes et al. (2006) on magmatic sulfide ore deposits.

DSL=SMAu and DMSS=SMAu values will be discussed in detail in a

complementary paper (Li and Audetat, in preparation). BothDSL=SMAu and D

MSS=SMAu do not show much dependence of oxygen

fugacity, with DMSS=SMAu 180 780 and DSL=SMAu 3400 71200.

In summary, the compatibility of these three elements insulfide liquid decreases in the order Au4CuEAg, and theircompatibility in MSS in the order Cu4Au44Ag. DMSS=SMAu isB20 times lower than DSL=SMAu at all conditions. Thus, a silicatemelt equilibrated with MSS contains more Cu, Au, and Ag than thesame melt equilibrated with an equivalent amount of sulfideliquid. Continuous exsolution of sulfide liquid from a crystallizingmagma results in approximately constant Cu/Ag ratios butdecreasing Au/Ag and Au/Cu ratios in the silicate melt, whereascontinuous exsolution of MSS causes all three ratios to decrease.3.4.3. Ni and Co

DSL=SMNi decreases from 1300 to 200 as the oxygen fugacityincreases. Our values are comparable to those of Peach et al.(1990), Gaetani and Grove (1997), Rajamani and Naldrett (1978),and Francis (1990), but are several times lower than the data ofPeach and Mathez (1993). The disagreement with the latter dataseems to be due to differences in oxygen fugacity, sulfur fugacity,

and the composition of the sulfide liquid. DMSS=SMNi shows a similar

behavior as DSL=SMNi , decreasing fromB800 toB300 as fO2 increases.Corresponding DSL=MSSNi values range from 1.0 to 1.8, which arewithin the range of values reported by Fleet et al. (1993, 1996),Li et al. (1996), and Ballhaus et al. (2001).

DSL=SMCo and DMSS=SMCo depend only weakly on oxygen fugacity and

vary from 30 to 50 and 30 to 60, respectively. These values areconsistent with the sulfide liquid-MORB partitioning data ofPeach et al. (1990) and are within the range reported byGaetani and Grove (1997). The similarity of DSL=SMCo and D

MSS=SMCo

suggests that the behavior of Co in sulfide-bearing silicate meltsdoes not depend on the type of sulfide present.

3.4.4. V, Mn, W, and Zn

These four elements are incompatible in both MSS and sulfideliquid, with DSL=SM and DMSS=SM values below unity. The Znpartitioning data of MacLean and Shimazaki (1976) andShimazaki and Maclean (1976) are consistent with this observa-tion. Higher DSL=SMZn values reported by Logas et al. (2008) andWood et al. (2008) 1oDSL=SMZn o10 may be due to the extremelylow fO2 of these experiments. Our V, Mn, and W partitioncoefficients are consistent with the data of Gaetani andGrove (1997) and are within the range found by Loddersand Palme (1991). Some higher values in the latter study0:03oDSL=SMW o3:1 seem to be related to very low oxygenfugacities. A DSL=SMW value of 9 was reported by Mengason et al.(2011) in a study with felsic melt. These results suggest thatsulfides are a negligible carrier of V, Mn, W, and Zn in magmas.

3.4.5. Sn, Sb, As, and Mo

DSL=SM and DMSS=SMvalues of these four elements are rathersensitive to variations in fO2. The maximum values are obtainedat reducing conditions, but they do not exceed 15 and 5,respectively. Sn, Sb, and As prefer sulfide liquid over MSS, whichis consistent with the findings of Helmy et al. (2010). In contrast,Mo prefers MSS over sulfide liquid. The much higher DSL=SMMo valuesof 60200 reported by Lodders and Palme (1991) might be due tolow oxygen fugacities in these experiments. The recent study onpyrrhotitesulfide liquidrhyolite system gave a DSL=SMMo value of 30and showed that Mo preferentially partitions into sulfide liquidrather than MSS at oxygen fugacity of NiNiO buffer (Mengasonet al., 2011). Our results suggest that limited amounts of sulfidesin natural magmas do not affect the abundance of these elementsin the silicate melt.4. Discussion

4.1. Estimation of oxidation state and sulfur fugacity

The basic principle of external oxygen buffering involvesdiffusion of hydrogen through a permeable membrane(Pt95Rh05 in our case) and dissociation equilibria of H2O onboth sides of the membrane (Chou, 1987). To obtain equaloxygen fugacities in the sample and the external buffer theactivities of water in the two reservoirs need to be the same. Inthis study the silicate melts produced in oxidized runs weresignificantly water-undersaturated, for which reason the oxi-dation states in these samples are expected to be significantlylower than the ones in the external, H2O-saturated ReReO andMnOMn3O4 buffers (Luth, 1989).

10

100

1000Ag

0.01

0.1

1

10As

0.1

1

10

100

1000 Bi

20

40

60

80

100Co

100

1000 Cu

0.1

1

10Mo

FMQ

500

1000

1500Ni

0.01

0.1

1

10

100Pb

-3

0.01

0.1

1

10Sb

1

10

Sn

DMSS/SM DSL/SM

-2 -1 0 1 FMQ

-3 -2 -1 0 1

-3 -2 -1 0 1 -3 -2 -1 0 1

-3 -2 -1 0 1 -3 -2 -1 0 1

-3 -2 -1 0 1 -3 -2 -1 0 1

-3 -2 -1 0 1 -3 -2 -1 0 1

Fig. 3. DMSS/SM (black dots) and DSL/SM (open diamonds) partition coefficients as a function of log fO2 relative to FMQ. Only data from runs with fO2 conditions determinedafter the experiment by either Fe3/ SFe (LY01, 04, 08, 19, 23, 26, 28, 29, 31, 32) or DVolivine/melt (LY30) are plotted in this figure. For simplicity, the error bars regarding fO2are shown only in the first plot.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340334Although the partial melts produced in runs externally buf-fered by NiNiO, CoCoO, and FeOFe3O4 were initiallywater-undersaturated too, diffusion of hydrogen into the capsulesand its interaction with silicate melt resulted in the production ofH2O and ultimately in saturation with an aqueous fluid phase.Thus, these samples ultimately reached approximately the same

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340 335oxygen fugacities as those imposed by the external buffers.A close correspondence between external and internal fO2 isconfirmed by the partitioning behavior of redox-sensitive ele-ments such as Mo. For example, hydrous run LY16 buffered at CoCoO returned a sulfide liquidsilicate melt partition coefficient of5.2, which is close to the value of 5.1 measured in less hydrousrun LY26 equilibrated at a similar oxygen fugacity, and hydrousrun LY17 buffered at NiNiO returned a sulfide liquidsilicatemelt partition coefficient of 0.13, which is close to the value of0.15 observed in less hydrous run LY08 equilibrated at a similaroxygen fugacity.

In those experiments in which fO2 was either not buffered atall or was expected to be significantly lower than the fO2 imposedby external buffers the oxidation state of the sample wasestimated based on the Fe3/SFe ratio in the silicate melt usingthe calibrations of Jayasuriya et al. (2004) and ONeill et al. (2006).In sample LY30, in which the melt pool was too small to beanalyzed by Mossbauer spectroscopy, fO2 was estimated based onolivine-melt partitioning of vanadium using the calibration ofCanil (1997). A test on sample LY26 shows a good agreementbetween fO2 estimated based on Fe

3/SFe (FMQ-2.6) and thatbased on vanadium partitioning (FMQ-2.1).

Sulfur fugacities can be estimated from the composition of thesilicate melt in equilibrium with MSS based on the reaction2FeOsilicate meltS22FeSMSSO2, (Bockrath et al., 2004b). To beable to extend the 1 atm calibration of Bockrath et al. (2004b) tohigh pressures, a volume change term was added by Liu et al.(2007). Sulfur fugacities in our samples were thus estimatedbased on equation (2) in Liu et al. (2007). The presence of23 wt% Cu and 78 wt% Ni in our MSS has a negligible effecton calculated fS2 (Kosyakov et al., 2003; Raghavan, 2004;Mengason et al., 2010).

4.2. Attainment of equilibrium

The time required for chalcophile elements to attain equili-brium between sulfide and silicate melt at temperatures above1000 1C has been shown to be short. Maclean and Shimazaki(1976) reported that equilibrium partitioning of Ni, Co, Cu, and Znbetween dry silicate melts and sulfides was attained after only15 min at 1150 1C. Rajamani and Naldrett (1978) demonstratedby forward and reverse runs that equilibrium partitioning of Fe,Co, Ni, and Cu in similar experiments was reached in less than12 h at 1255 1C. Several lines of evidence suggest that equili-brium was also reached in our experiments. First, both the silicatemelt and sulfide phases are compositionally homogeneous withrespect to both major and trace elements. Second, the partitioncoefficients do not show any dependence on run duration or theelement concentrations in the starting sulfide, but vary as afunction of oxygen fugacity (see below). Third, our data comparewell with the literature data, particularly if looking at the studiesusing natural silicate melts such as MORB (Peach et al., 1990;Francis, 1990).

4.3. Summary and significance of the partitioning data

In summary, the partition coefficients of most elementsinvestigated in this study are affected mainly by oxygen fugacityand/or the type of sulfide present. Variations in temperature andpressure have no significant effect in the range from 1175 1C/1.5 GPa to 1300 1C/ 3 GPa, the same as variations in the watercontent (from B5 wt% to 410 wt% H2O) and (MgOFeO)/(Al2O3Na2OK2O) ratio (0.92.2), of the silicate melt. A com-paratively small dependence on melt composition is also indi-cated by the good agreement of the present data with thosedetermined on natural sulfide melt globules in MORB glasses(Francis, 1990; Peach et al., 1990), which melts contain much lesswater (o0.5 wt% H2O) and alkalies than those of the presentstudy. This means that the partition coefficients determined inthe present study should be applicable to mantle melting andmagma crystallization in a large range of tectonic settings,including MORB and arc environments. SL/SM partition coeffi-cients decrease in the order Au4Ni, Cu, Ag, Bi4Co, Pb4Sn, Sb,As, with the remaining elements fractionating into the silicatemelt. MSS/SM partition coefficients decrease in the order Ni, Cu,Au4Co, Ag4Bi, Mo, with the remaining elements fractionatinginto the silicate melt. SL/MSS partition coefficients are almostalways 41 and decrease in the order Pb4Bi, Sb4Au4Ag4Cu,As4Mo, Ni4remaining elements. Most sulfidesilicate meltpartition coefficients vary as a function of fO2, with Mo, Bi, As(7W) varying by a factor 410 over the investigated fO2 range,Sb, Ag, Sn (7V) varying by a factor of 310, and Pb, Cu, Ni, Co, Au,Zn, Mn varying by a factor of o3. To constrain the abundance ofsulfides in magmatic environments elements with very highSL/SM partition coefficients (e.g., Au, Cu, Ag, and Bi) are mostappropriate. To constrain the type of sulfide present elementswith high SL/MSS partition coefficients (e.g., Pb, Bi, Sb, and Ag) aremost appropriate. Thus, combinations between Au, Cu, Ag, and Biare best suited to constrain both the absolute abundance and typeof sulfide present. The capability of this approach is illustrated bythe following two applications.5. Applications

5.1. Constraints on the metal content of primitive mantle melts

During partial melting, the concentration of metals in thesilicate melt depends on the abundances of MSS and sulfide liquidin the mantle source, the corresponding partition coefficients, andthe degree of partial melting. The experimental study of Bockrathet al. (2004a) showed that in the upper mantle both MSS andsulfide liquid may coexist, which result is confirmed by thepresent study. According to the sulfide phase diagram ofBockrath et al. (2004a) and estimated PT conditions of magmaproduction in MORB and arc settings (Fig. 4), sulfides in thesource region of MORB are probably dominated by sulfide liquid,whereas in the source region of arc magmas they are probablydominated by MSS.

The abundance of sulfur in the source region is a critical factorwith regard to the behavior of metals during partial melting.Studies on mantle peridotite xenoliths have shown that sulfur isheterogeneously distributed in the upper mantle (e.g., Lorand,1990; McInnes et al., 2001; Lee, 2002; Alard et al., 2011). For thedepleted mantle source of MORB an average sulfur concentrationof 190750 mg/g was estimated by several authors (Lorand, 1990;Saal et al., 2002; Bezos et al., 2005), whereas for primitive mantlea concentration of 250750 mg/g was estimated by McDonoughand Sun (1995). Metasomatized mantle seems to be enriched insulfur. Average concentrations of 250500 mg/g were estimatedfor metasomatized arc mantle by Metrich et al. (1999) andde Hoog et al. (2001), while individual mantle xenoliths containup to 1190 ppm sulfur (McInnes et al., 2001). A positive correla-tion between the degree of hydrous metasomatism, sulfur enrich-ment and increased oxidation state has been noted in many cases(e.g., McInnes et al., 2001; Rowe et al., 2009; Wallace andEdmonds, 2011).

In the following model, absolute and relative concentrations ofthe highly chalcophile elements Cu, Au, and Ag in primitive arcbasalt were modeled as a function of degree of partial melting andthe relative abundances of MSS versus sulfide liquid in the mantlesource (Fig. 5). The latter was assumed to have an oxidation state

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340336of FMQ1 (Parkinson and Arculus, 1999; Frost and McCammon,2008), a sulfur content of 350 mg/g, and the Cu, Au, and Agconcentrations estimated for depleted mantle (Salters andStracke, 2004). Using these numbers, the average Cu content ofsulfides turns out at 3.0 wt% (assuming that no Cu is storedin other phases), which agrees well with the Cu content ofnatural mantle sulfides. The following partition coefficients were

used: DMSS=SMCu 280, DMSS=SMAg 40, D

MSS=SMAu 180, D

SL=SMCu 180,0.0001

0.001

0.01

0.1

1

10

100

1000

0% partial melting

con

c. in

sili

cate

mel

t (pp

m)

Cu MSS

Cu SL

Ag MSS Ag SL

Au MSS

Au SL

Cu

Ag

Au

5 10 15 20

Fig. 5. Modeled Cu, Au, Ag concentrations and Cu/Au, Cu/Ag, Ag/Au ratios in primitive aMSS relative to sulfide liquid (0 wt% MSS, 50 wt% MSS, and 100 wt% MSS). The process

exhaustion occurs at 14 wt% melting. The gray boxes on the right show the ranges of na

increases with increasing degree of partial melting if the proportion of MSS is very hig

1100Temperature (C)

3

2

1

0

1000

0.1 wt

% H 2

O

0.05 w

t% H 2

O

dry pe

ridoti

te

solid

us

4

sulfid

e soli

dus

1500

sulfide liquidus

MORB

Arc

wet peridotite solidus

Pre

ssur

e (G

Pa)

1200 1300 1400

Fig. 4. PT diagram showing the phase relations of sulfide according to Bockrathet al. (2004a) and the effect of added volatiles on the mantle solidus. Gray symbols

represent data points of Bockrath et al. (2004a) (full squaresMSS; half-filledsquaresMSS coexisting with sulfide liquid; open squaressulfide liquid). Blackand white symbols represent data points of this study (full circleMSS; half-filledcircleMSSsulfide liquid; open circlesulfide liquid). Notice the generally goodagreement between the results obtained by Bockrath et al. (2004a) and those of

the present study. Dry peridotite solidus is from Katz et al. (2003), wet peridotite

solidus is from Grove et al. (2006), and solidi with 0.05 and 0.1 wt% H2O added are

from Katz et al. (2003). Estimated PT conditions of partial melting for arc

magmas and MORB are shown as blue and red fields, respectively. The former

are based on Sobolev and Chaussidon (1996), Ulmer (2001), Pichavant et al.(2002), Johnson et al. (2009), and Kimura et al. (2009), and the latter are based on

Kushiro (2001) and Presnall and Gudfinnsson (2008). (For interpretation of the

references to color in this figure caption, the reader is referred to the web version

of this article.)DSL=SMAg 1000, and DSL=SMAu 3400. At a sulfur content of 350 mg/g

in the source and a sulfur solubility of 2500 mg/g S in the silicatemelt (Jugo et al., 2010), sulfide exhaustion occurs at 14 wt%partial melting. For melting in the presence of both MSS andsulfide liquid we assumed constant relative proportions of thesetwo phases until total sulfide exhaustion. Whether or not sulfidemelts can be extracted by physical means (i.e., as entraineddroplets) is still a matter of debate (e.g., Ballhaus et al., 2006;Barnes et al., 2008). Experimental and theoretical studies on meltextraction from partially molten mantle suggest that partialmelting is near-fractional (Kelemen et al., 1997; Kohlstedt andHoltzmann, 2009). We thus modeled the process as fractionalmelting in steps of 1 wt% melting. The effects of batch meltingwould be qualitatively the same but less pronounced. Similarly,changes in the sulfur content of the source and/or the sulfursolubility in the partial melt result in trends that are qualitativelythe same, but sulfide exhaustion is attained at different degrees ofpartial melting (e.g., at 1000 mg/g instead of 350 mg/g S in thesource, sulfide exhaustion is reached at 40 wt% instead of 14 wt%).

The modeling results show that the absolute abundances of Cu,Au, and Ag in the silicate melt increase with increasing degree ofpartial melting, except for Ag in the case of a high proportion ofMSS. The calculated element concentrations and element ratiosagree well with actual concentrations reported from primitive arcmagmas (Jenner et al., 2010). Ratios of Cu (which has a DSL=MSSof1.43) to Ag and Au (which have DSL=MSS values of 1050 and 20,respectively) are sensitive to the proportion of MSS relative tosulfide liquid (Fig. 5b). For example, at high MSS fractions theCu/Au ratio in partial melts increases with increasing degree ofpartial melting, whereas at intermediate to low MSS fractions theCu/Au ratio in the melt decreases. Since MSS seems to be thedominant sulfide in the source region and during later evolutionof arc basalts (see below), the Cu/Au ratio in the silicate melt maythus increase with increasing degree of partial melting. This resultis in contrast to previous models in which the Cu/Au ratio wasconsidered to decrease with increasing degree of partial melting,leading to arc magmas with particularly high Au/Cu ratios whensulfide exhaustion is approached (Mungall, 2002; Richards, 2009).These models are correct only if the dominant sulfide phase in thesource region is sulfide liquid.1

10

100

1000

104

105

106

0

met

al ra

tio in

sili

cate

mel

t

% partial melting

Cu/Au MSS

Cu/Au SL

Cu/Ag MS

S

Cu/Ag SL

Ag/Au MSS

Ag/Au SL

Cu/Au

Cu/Ag

Ag/Au

5 10 15 20

rc basalt as a function of the degree of parial mantle melting and the proportion of

was modeled as fractional melting with steps of 0.7 wt% melt production. Sulfide

tural, arc-like magmas reported by Jenner et al. (2010). Notice that the Cu/Au ratio

h.

0.001

0.01

0.1

1

10

0

Bi MS

S

Bi SL

Ag MSS

Ag SL

Au MSS

Au SL

% crystallization

con

c. in

sili

cate

mel

t (pp

b)

10000

1000

100

con

c. in

sili

cate

mel

t (pp

b)

0

5

10

15

20

25

30

35

40

45678910MgO (wt%)

AgBiAu

20 40 60 80 100

Fig. 6. (a) Modeled concentrations of Ag, Au, and Bi in sulfide-saturated MORB as a function of the degree of fractional crystallization and proportion of MSS relative tosulfide liquid. (b) Measured concentrations of Ag, Au, and Bi in variously differentiated MORB according to Jenner et al. (2010). The increasing Bi concentration but

decreasing Ag concentration with decreasing amount of MgO in the silicate melt implies that MSS made up between 28% and 70 wt% of the precipitating sulfide.

1

10

100

1000

104

105

106

0

met

al ra

tio in

sili

cate

mel

t

% crystallization

Cu/Au MSS

Cu/A

u SL

Cu/Ag MSS

Cu/Ag SL

Ag/Au MSS

Ag/A

u SL

0246810

10

100

Ag/

Au

MgO (wt%)

100

1000

10000

Cu/

Ag

MgO (wt%)

20

40

60

80100

Cu/

Au

MgO (wt%)

0246810

024681020 40 60 80 100

Fig. 7. (a) Modeled Cu/Au, Cu/Ag, and Ag/Au ratios in arc basalt as a function of the degree of fractional crystallization and the proportion of MSS relative to sulfide liquid.The magma is assumed to be initially sulfide undersaturated, reaching saturation at 40% crystallization. (b) Measured Cu/Au, Cu/Ag, and Ag/Au ratios in natural, arc-like

magmas as reported by Jenner et al. (2010). The observed trends require Z95 wt% MSS in the precipitating sulfide.

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 327340 337

Y. Li, A. Andreas / Earth and Planetary Science Letters 355-356 (2012) 3273403385.2. Constraints on the type of sulfide phase(s) present during

magma differentiation

The solubility of sulfur in silicate melts is a function of tempera-ture, pressure, melt composition, and oxygen fugacity. Decreasingmagma temperature, crystallization of Fe-bearing minerals, andincreasing SiO2 content all leads to a decrease in sulfur solubility.Thus, basically any magma that has experienced significant fractiona-tion should be sulfide-saturated (Parat et al., 2011). If sulfide satura-tion is common in magmas, which type of sulfide phase can beexpected for magmas of different tectonic settings? Arc magmascrystallize at lower temperatures and higher pressures than MORBand thus are more likely to precipitate MSS. This trend is supportedby the recent data on chalcophile element concentrations in variouslydifferentiated MORB and arc magmas (Jenner et al., 2010). Based onconstant Cu/Ag ratios but increasing Cu/Au ratios with increasingdegree of differentiation these authors concluded that MORBmagmasfractionated mainly sulfide liquid, whereas arc fractionated dom-inantly MSS. The sulfidesilicate melt partition coefficients presentedin this study allow the conclusions of Jenner et al. (2010) to be testedquantitatively.

Sulfur content and sulfur solubility in arc basalts were chosen tobe 0.15 wt% and 0.25 wt%, respectively, whereas for MORB bothvalues were set at 0.1 wt% (i.e., the arc basalts were assumed to beinitially sulfide-undersaturated, and MORB were assumed to besulfide-saturated from the beginning). The starting concentrationsof Cu, Ag, Bi, and Au in the silicate melt were 200, 0.05, 0.005, and0.005 ppm in both cases. For MORB we used the following sulfidesilicate melt partition coefficients: DMSS=SMBi 2, D

MSS=SMAg 40,

DMSS=SMAu 180, DSL=SMBi 500, D

SL=SMAg 1100, and D

SL=SMAu 3400,

whereas for arc basalts we used DMSS=SMCu 280, DMSS=SMAg 40,

DMSS=SMAu 180, DSL=SMCu 180, D

SL=SMAg 1000, and D

SL=SMAu 3400. Crys-

tallization was assumed to be fractional (modeled in steps of 3 wt%),and sulfur and metals were assumed to be 100% incompatible in allminerals except for sulfides. For the scenario that involves precipita-tion of both MSS and sulfide liquid the relative proportions of thesetwo phases were assumed to remain constant during the entirecrystallization interval (which is of course an oversimplification).

The modeling results for MORB are shown in Fig. 6a. The stronglydecreasing Ag concentrations with decreasing MgO contents ofnatural MORB (Fig. 6b) suggest that the proportion of SL in theprecipitating sulfides was at least 50 wt%, whereas the slightlyincreasing Bi concentrations require a similar amount of MSS beingpresent. Thus, although SL not necessarily had to be dominant, itcertainly made up a major fraction of the precipitating sulfides. Thisconclusion is consistent with the finding of Bezos et al. (2005) thatresidual MSS is required to explain the PGE patterns observedin MORB.

The modeling results for arc basalts are shown in Fig. 7a.Measured metal ratios in the Pual Ridge magmas remain nearlyconstant until the MgO content of the silicate melt becomes less than4 wt% (Fig. 7bd), and then suddenly increase or decrease. Thissuggests that originally sulfide-undersaturated magmas reachedsulfide saturation at B4 wt% MgO. The fact that Cu/Ag and Cu/Auin the Pual Ridge magmas decrease with increasing differentiation(Fig. 7b and c) requires a very high proportion (495%) of MSS in theprecipitating sulfides, as already minor amounts of sulfide liquid leadto increasing Cu/Ag and Cu/Au with increasing differentiation(Fig. 7a). Thus, the modeling results for both MORB and arc basaltssupport the conclusions drawn by Jenner et al. (2010).

Acknowledgments

We like to thank Hans Keppler for discussions, CatherineMcCammon for discussions and help with the Mossbauer analyses,Sebastian Pilet for providing the AG4 starting material, FrancesJenner for sharing her whole-rock analyses of MORB and arcbasalts, and Detlef Kraue and Julia Huber for help with themicroprobe analyses. Thoughtful comments by editor Tim Elliottand an anonymous reviewer greatly helped to improve the paper.Appendix A. Supporting information

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Partitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide phases and hydrous basanite...IntroductionExperimental methodsStarting materialsSample capsules and control of fO2High temperature and pressure equipmentAnalytical methodsElectron microprobeLA-ICP-MSMssbauer spectroscopy

ResultsSample petrographyMajor and trace element content of silicate meltMajor and trace element content of sulfide phasesPartition coefficients3.4.1. Bi and Pb3.4.2. Cu, Ag, and Au3.4.3. Ni and Co3.4.4. V, Mn, W, and Zn3.4.5. Sn, Sb, As, and Mo

DiscussionEstimation of oxidation state and sulfur fugacityAttainment of equilibriumSummary and significance of the partitioning data

ApplicationsConstraints on the metal content of primitive mantle meltsConstraints on the type of sulfide phase(s) present during magma differentiation

AcknowledgmentsSupporting informationReferences