Rhenium systematics in submarine MORB and back-arc basin

glasses: laser ablation ICP-MS results

W. Suna,*, V.C. Bennetta, S.M. Egginsa, R.J. Arculusb, M.R. Perfitc

aResearch School of Earth Sciences, The Australian National University, Canberra, ACT 0200, AustraliabDepartment of Geology, The Australian National University, Canberra, ACT 0200, AustraliacDepartment of Geological Sciences, University of Florida, Gainesville, FL 32611-2120, USA

Abstract

Rhenium and other trace elements, including the moderately chalcophile elements Mo and Cu, were determined for 37

submarine basaltic glasses from the Lau and Coriolis Troughs (CT) back-arc basins and Woodlark marginal basin, as well as 30

mid-ocean ridge basalt (MORB) glasses from the Pacific and Atlantic Oceans, using laser ablation ICP-MS. Rhenium is

strongly positively correlated with Yb for all these submarine basaltic glasses. Enriched (E-) and normal (N-) MORB as well as

King’s Triple Junction samples show similar correlations with constant Yb/Re ratios, indicating that Re and Yb exhibit similar

compatibility during melt evolution [Chem. Geol. 139 (1997) 185]. In contrast, samples from the East and Central Lau

Spreading Centers have much higher ratios compared with MORB samples and form steeper arrays on Re–Yb variation

diagrams, similar to komatiites. More incompatible element-depleted samples including those from the Lau and Woodlark Basin

spreading centers and the more depleted (D-) MORB samples are also distinguished from E- and N-MORB and samples from

King’s Triple Junction and Coriolis Troughs Basin on the basis of their higher Cu/Re ratios. These observed elemental

systematics are interpreted to reflect progressive melting of depleted mantle, where previous melting events result in the

elimination of sulfides in the source regions of the depleted samples.

Using the determined Yb/Re and Ce/Mo ratios and assuming that the abundances of Yb and Ce are 10% and 40% reduced in

the DMM compared to the primitive mantle (PM), average concentrations of 0.12 ppb for Re and 34 ppb for Mo are estimated

for the DMM. The partition coefficients of the analysed moderately incompatible elements are in the order of

Mo <Ce <Re <Yb for the depleted samples (no residual sulfide), while for those that were derived from sources with

residual sulfide, the order is Mo =Ce <Yb=Re.

D 2002 Elsevier Science B.V. All rights reserved.

Keywords: Rhenium; MORB; Back-arc basin basalts; Laser ablation; Highly siderophile elements

1. Introduction

The long-lived chalcophile–siderophile Re–Os

isotopic system is contributing to a more compre-

hensive understanding of the evolution of the Earth.

A fuller application of this system is, however,

limited by a lack of detailed knowledge of the

budgets and geochemical behavior of these elements,

0009-2541/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved.

doi:10.1016/S0009-2541(02)00416-3

* Corresponding author. Tel.: +61-2-612-53404; fax: +61-2-

612-50738.

E-mail addresses: weidong.sun@anu.edu.au (W. Sun),

vickie.bennett@anu.edu.au (V.C. Bennett),

stephen.eggins@anu.edu.au (S.M. Eggins),

richard.arculus@anu.edu.au (R.J. Arculus), perfit@geology.ufl.edu

(M.R. Perfit).

www.elsevier.com/locate/chemgeo

Chemical Geology 196 (2003) 259–281

particularly in the subduction environment. The sim-

ilar behavior of Re and heavy REE such as Yb

during melting of mantle peridotite is well docu-

mented (Hauri and Hart, 1997; Reisberg and Lorand,

1995; Reisberg et al., 1991, 1993) although the cause

of this coherence is paradoxical as the behavior of

these two elements during melting and crystallization

is controlled by different phases. In general, Re is

strongly compatible in sulfide and possibly mildly

compatible in garnet (Righter and Hauri, 1998) but

incompatible in other silicates, whereas Yb is incom-

patible in sulfide and compatible in garnet (Righter

and Hauri, 1998). This is illustrated by the different

correlations between Re and Yb for mid-ocean ridge

basalt (MORB) and komatiite suites, with the dis-

placement between the Yb/Re correlation lines being

interpreted as resulting from the presence and

absence of residual sulfide, respectively (Schaefer

et al., 2000).

Rhenium and Yb also behave differently in sub-

duction environments, with Yb demonstrated to be

one of the least mobile elements (Becker et al., 2000;

Johnson and Plank, 1999). In contrast, studies of

eclogites and blueschists show that up to 60% of Re

can be lost from the oceanic slab during subduction

(Becker, 2000). This ‘‘lost Re’’ is expected to be

transferred to the mantle wedge and therefore to arc

and/or back-arc magmas, presumably resulting in

higher average Re concentrations in arc-related mag-

mas than in MORBs. Rhenium enrichment in veined

peridotite xenoliths from a supra-subduction location

has been reported (McInnes et al., 1999). However,

the average Re concentration of arc volcanics is only

0.301F 0.019 ppb (n = 147) (Alves et al., 1999; Alves

et al., 2002; Woodland et al., 2002), which is much

lower than that of average MORB (0.885F 0.063

ppb, n = 35) (Schiano et al., 1997). Possible explan-

ations for the apparent low Re contents include

volatile loss of Re syn- or post-eruption in the analysed

arc volcanic rocks, most of which were subaerially

erupted; oxide fractionation may also contribute to the

low Re in the more evolved arc samples. To explore

further the behavior of Re in the subduction zone

environment we have analysed Re along with other

trace elements including the moderately chalcophile

elements Mo and Cu, from suites of back-arc basin

basalt (BABB) glasses. All data were obtained in situ

using laser ablation ICP-MS. Also included in the

analyses were natural glasses from both the Atlantic

and Pacific Oceans to provide coherent data sets of a

range of typical MORB for comparative purposes. A

significant advantage of laser analysis is that only

small amounts of glass are necessary, greatly expand-

ing the range of suitable samples. Analysis was limited

to only deeply (>1000 m) erupted submarine samples

to avoid complexities potentially arising from syn- and

post-eruption loss of Re, which can be volatile during

eruption. This effect has been observed in Hawaiian

lava suites (Bennett et al., 2000; Bernard et al., 1990;

Taran et al., 1995) and may be an even greater problem

in arc and BAB lavas owing to both higher volatile

contents and potentially higher oxygen fugacities in

these environments.

2. Geological setting and samples

The Lau Basin, Woodlark Basin and Coriolis

Troughs (Vate), all located in the Southwestern

Pacific, have broadly developed as the result of

complex interactions between the Pacific and Indo-

Australian plates (Taylor, 1995). The Lau Basin is a

1300 km long triangular depression, 450 km wide in

the north and narrowing to 190 km in the south

(Gill, 1976). It is an active extensional back-arc

basin, which opened through rapid clockwise rota-

tion (7j/Ma) of the Tonga arc (Bevis et al., 1995;

Fischer and Wiens, 1996; Hawkins, 1994; Taylor et

al., 1996). Basaltic rocks from the Lau Basin have

been well studied, especially during the decade

following the 1990 cruise of Akademic Mstislav

Keldysh/Mir (Falloon et al., 1992; Honda et al.,

1993). Early geochemical studies suggested that

basalts from the Lau back-arc basin are similar to

mid-ocean ridge basalts (MORB) (Carlson et al.,

1978; Gill, 1976; Hawkins, 1976). Later work,

however, has documented considerable variation in

their compositions and significant differences com-

pared with MORB (Falloon et al., 1992; Hawkins,

1995; Hawkins and Melchior, 1985).

Overall, the Lau Basin samples are enriched in

H2OF large ion lithophile elements (LILE)F light

rare earth elements (LREE), believed to be a con-

sequence of high concentrations of these elements in

hydrous fluids derived from the subducting slab

beneath the Tonga-Kermadec and Lau Basin (Falloon

W. Sun et al. / Chemical Geology 196 (2003) 259–281260

et al., 1992). This is supported by noble gas isotopic

compositions of Lau samples, which show slightly

more radiogenic He isotopic compositions compared

with MORB, and higher proportions of atmospheric

heavier noble gases (Bach and Niedermann, 1998;

Honda et al., 1993; Poreda, 1985; Sano et al., 1986).

Atmospheric Ar isotopic compositions have also

been attributed to the influence of the subducting

slab (Bach and Niedermann, 1998; Honda et al.,

1993). The radiogenic He has been variously inter-

preted as reflecting the involvement of either small

portions of recycled helium (Honda et al., 1993;

Poreda, 1985; Sano et al., 1986), assimilated old

basement (Gasparon et al., 1994; Hilton et al.,

1992, 1993), or ingrowth of radiogenic helium in a

highly depleted mantle wedge after its enrichment in

U and Th from the subducting slab (Bach and

Niedermann, 1998).

The Lau Basin samples studied in this paper were

dredged from three different locations at more than

2000 m depth within the Lau Basin during the 1990

cruise of the Akademic Mstislav Keldysh: (1) the

King’s Triple Junction (KTJ. 15jS), a nascent triple

junction in the northeastern part of the basin (dive

station 2218); (2) the Central Lau Spreading Center

(CLSC, 19jS, dive station 2231); and (3) the northern

end of the Eastern Lau Spreading Center (ELSC,

20jS, dive station 2239). All of the glass samples

analysed here are fractions of the same separates

previously selected for noble gas analysis (Honda et

al., 1993). The vesicularity of all samples is less than

1% (Falloon et al., 1992), suggesting that no signifi-

cant volatile loss has occurred.

The Woodlark basin is an actively spreading mar-

ginal basin located at the northeastern edge of the

Australian plate, extending eastward from eastern-

most New Guinea to the frontal part of the Solomon

island-arc and splitting the formerly contiguous

Woodlark and Pocklington Rises. Spreading in the

Woodlark basin began at about 5 Ma with current

spreading rates of 5.6 cm/year in the west and 7.3 cm/

year in the east (Dril et al., 1997; Petterson et al.,

1999). Samples from the Woodlark spreading center

are primarily N-type MORB, but more arc-like lavas

have been recovered from near the triple junction with

the New Georgia Group of the Solomon Islands

(Perfit et al., 1987; Trull et al., 1990). The samples

used in this study were dredged from a seamount in

the Eastern Woodlark Basin at a water depth of about

3000 m during the RV Franklin 04/00 SHAARC

cruise in April 2000. All of the analysed materials

are fresh glasses without any visible phenocrysts or

vesicles.

The Vanuatu Island Arc experienced two episodes

of subduction: westward subduction of the Pacific

plate in the early Tertiary and eastward subduction of

the Indo-Australian plate from about 10 Ma (Baker

and Condliffe, 1996; Pelletier et al., 1998). The

Coriolis Troughs samples are fresh glasses collected

about 50 km east of the arc volcanic front at water

depths of about 2000 m. Two of the samples have

more than 5% vesicles (VD-21, 23), and possibly

experienced some volatile loss, while the third sample

has no vesicles.

MORB samples from both the Pacific and Atlan-

tic Oceans were analysed. The Atlantic MORB

(FAMOUS) suite includes samples studied by Lang-

muir et al. (1977). This suite has almost as much

variation in major element composition as basalts from

the rest of the global ocean floor, as well as a large

variation in trace elements abundances (Langmuir et

al., 1977). Fresh MORB glasses from the northern East

Pacific Rise (EPR) and the southern Juan de Fuca

Ridge were recovered using the submersible ALVIN.

The EPR samples are from the 9–10jN segment and

are representative of the range of MORB compositions

from this fast-spreading axis (Haymon et al., 1993;

Perfit et al., 1994; Rubin et al., 2001). The samples

range from typical mafic N-MORB recovered from the

axial summit collapse trough, to moderately fractio-

nated enriched varieties (E-MORB) recovered from

off-axis (2489-#; Table 1). The most enriched samples

(2390-#; Table 1) were recovered from within the

Siqueiros Transform from the ridge–transform inter-

section where the EPR overlaps and descends into the

transform domain. These samples have trace element

and isotopic compositions that suggest they were

derived from relatively enriched oceanic sources

(Lundstrom et al., 1999).

The suite of glasses from the intermediate spread-

ing-rate Juan de Fuca Ridge (JdF) are from the Cleft

Segment along the southernmost portion of the ridge

and from Axial Volcano, a ridge-centered seamount,

north of the Cleft segment. Samples from the Cleft

segment are representative of the moderately evolved

N-MORB from the JdF and include very young

W. Sun et al. / Chemical Geology 196 (2003) 259–281 261

Table 1

Trace element concentrations of submarine basaltic glass samplesa

Sc V Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd

E-MORB East Pacific Rise

Alv2390-8 37.6 337 15.4 296 38.9 190 22.5 0.180 172 17.9 42.5 5.59 23.4 6.57 2.15 7.23

Alv2390-4 36.9 326 13.9 276 36.9 172 19.8 0.150 150 16.0 37.7 5.00 21.2 5.86 1.98 6.80

Alv2390-4 38.4 341 14.3 292 38.9 183 20.9 0.170 160 16.8 40.3 5.37 22.7 6.37 2.05 7.20

Alv2390-3B 37.9 331 13.9 282 37.6 177 20.3 0.150 154 16.3 38.8 5.15 21.7 6.08 2.00 6.93

Alv2390-3 37.7 333 13.7 278 37.1 175 20.0 0.150 152 16.0 38.2 5.12 21.4 5.97 2.00 6.92

2489-8 42.9 365 7.08 195 40.3 156 10.7 0.080 76.0 10.2 26.7 3.89 17.5 5.47 1.89 6.79

2489-5 44.0 346 7.40 167 36.7 141 9.22 0.090 72.0 8.70 22.7 3.25 15.1 4.75 1.67 6.01

2489-3 43.1 330 6.58 157 33.8 129 8.46 0.080 65.0 7.83 20.5 3.00 13.7 4.36 1.51 5.50

2489-3 43.4 332 6.72 159 34.4 131 8.48 0.090 66.0 8.05 21.2 3.06 13.9 4.42 1.52 5.62

N-MORB East Pacific Rise

2392-9 40.4 275 0.88 120 24.6 68.9 1.86 0.010 7.67 2.71 8.66 1.45 7.31 2.67 1.02 3.80

2372-1 40.8 278 0.84 124 25.3 70.2 1.93 0.010 7.82 2.83 9.00 1.48 7.57 2.83 1.06 3.83

2364-11 44.4 329 1.17 117 31.1 89.1 2.51 0.010 10.0 3.73 11.5 1.93 9.69 3.54 1.27 4.84

2358-4 44.7 336 1.17 119 31.5 89.9 2.50 0.010 10.1 3.74 11.7 1.93 9.85 3.47 1.29 4.80

D-MORB Ecuador Rift

1121-1 43.6 290 0.16 84.4 24.0 50.6 0.40 0.008 1.48 1.28 5.28 1.03 5.94 2.52 0.99 3.47

1123-2 47.2 328 0.28 64.1 27.9 48.2 0.58 2.39 1.36 5.27 0.99 5.76 2.54 1.00 3.80

1128-3 45.2 313 0.30 79.1 26.0 52.3 0.68 0.012 2.96 1.56 5.80 1.07 6.00 2.49 0.98 3.70

N- and E-MORB FAMOUS

523-1 37.3 268 6.38 124 20.7 58.4 10.3 0.072 67.3 6.30 14.8 1.93 8.37 2.60 0.91 3.22

525-5-2 41.1 236 3.00 78.9 18.2 39.4 5.47 0.036 31.1 3.60 8.85 1.18 5.49 1.74 0.68 2.44

526-5 39.9 311 6.87 110 27.2 73.9 11.6 0.078 68.6 7.26 17.2 2.29 10.2 3.16 1.11 4.11

527-1-1 43.9 217 1.74 60.6 17.5 26.2 2.94 0.028 18.8 2.03 5.24 0.75 3.65 1.40 0.59 2.01

529-4 37.3 261 4.39 102 21.7 55.2 7.52 0.054 43.3 4.84 11.9 1.65 7.35 2.41 0.90 3.21

N-MORB Juan de Fuca Ridge

2257-1 45.3 396 3.01 105 35.9 98.9 5.28 0.034 29.3 4.88 13.9 2.19 10.7 3.84 1.38 5.22

2257-3 46.4 427 2.72 92.7 40.2 106 4.87 0.032 25.7 4.82 14.2 2.23 11.3 4.16 1.50 5.80

2262-8 44.3 330 1.23 117 26.7 72.2 3.07 0.009 13.0 3.35 10.1 1.62 8.07 2.88 1.11 4.10

2263-6 45.0 397 1.71 114 37.1 105 4.47 0.012 17.1 4.75 14.2 2.27 11.3 4.04 1.48 5.53

2269-2 46.8 367 1.46 116 30.7 85.1 3.64 0.013 15.3 3.92 11.9 1.84 9.31 3.46 1.25 4.66

D-MORB East Pacific Rise

Alv1558 41.4 269 0.22 74.0 20.1 37.1 0.59 2.26 1.06 4.03 0.78 4.31 1.93 0.80 2.88

Alv1558 41.3 271 0.24 78.0 21.0 39.5 0.63 2.35 1.11 4.36 0.81 4.64 2.00 0.85 2.93

Alv1566 43.0 281 0.28 87.5 23.2 50.5 0.79 0.002 2.67 1.46 5.60 1.06 5.89 2.47 0.94 3.44

N-MORB Axial

XL1739-2A 44.8 302 2.21 142 24.5 75.1 4.29 0.016 25.3 4.18 11.8 1.80 8.57 2.90 1.13 3.95

XL1723-1A 48.0 324 2.37 152 26.5 81.5 4.59 0.026 27.2 4.54 12.7 1.94 9.32 3.20 1.23 4.24

N-MORB Megaplum

2078-4 43.2 335 1.12 98.5 28.3 71.1 2.78 0.008 11.0 3.06 9.51 1.55 7.80 2.99 1.13 4.16

2093-1A 43.8 350 1.38 111 30.3 82.8 3.54 0.004 14.0 3.74 11.4 1.82 8.99 3.33 1.24 4.51

Eastern Lau Spreading Center

2239-2 44.3 376 1.90 83.9 27.1 51.2 1.30 0.021 13.5 2.00 6.60 1.10 6.70 2.50 0.93 3.70

2239-2 44.2 371 1.90 84.7 27.3 51.4 1.30 0.019 13.9 2.00 6.60 1.10 6.80 2.60 0.94 3.70

2239-1 41.3 324 1.85 87.0 25.1 45.7 1.16 0.020 12.4 1.87 6.25 1.09 5.84 2.35 0.89 3.37

W. Sun et al. / Chemical Geology 196 (2003) 259–281262

Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U Cu Mo Re(U)b Re(C)c Re(ID)d

7.76 4.34 4.02 0.59 4.72 1.43 1.59 1.57 0.55 65.3 1.58 1.1 1.0

7.13 4.12 3.79 0.56 4.16 1.24 1.45 1.36 0.47 66.2 1.41 1.0 0.9

7.60 4.40 4.10 0.60 4.58 1.33 1.52 1.46 0.50 67.6 1.37 1.0 0.9

7.30 4.20 3.88 0.57 4.43 1.28 1.45 1.41 0.47 62.9 1.37 1.0 0.9

7.16 4.12 3.83 0.57 4.34 1.27 1.47 1.39 0.48 67.1 1.46 1.1 1.0

7.58 4.46 4.28 0.63 3.97 0.68 1.04 0.75 0.27 75.0 0.86 1.1 1.0

6.88 4.14 3.90 0.59 3.62 0.580 1.11 0.71 0.26 77.7 0.83 1.1 1.0

6.33 3.84 3.68 0.55 3.26 0.540 1.02 0.66 0.23 80.2 0.83 1.2 1.1

6.45 3.88 3.80 0.54 3.33 0.550 1.00 0.67 0.23 81.3 0.75 1.0 0.9

4.56 2.79 2.66 0.39 1.89 0.130 0.790 0.11 0.05 83.8 0.27 0.9 0.8

4.71 2.88 2.74 0.40 1.91 0.130 0.430 0.11 0.05 85.8 0.28 0.9 0.8

5.77 3.53 3.43 0.51 2.45 0.170 0.520 0.15 0.07 73.3 0.35 1.0 0.9

5.85 3.58 3.43 0.52 2.48 0.170 0.530 0.16 0.07 72.8 0.34 1.1 1.0

0.63 4.33 0.94 2.74 0.389 2.71 0.39 1.58 0.033 0.326 0.033 0.018 100 0.10 0.8 0.8

0.70 4.98 1.07 3.21 0.475 3.20 0.48 1.59 0.043 0.333 0.047 0.019 103 0.10 1.1 1.0

0.67 4.80 1.01 2.93 0.437 3.01 0.44 1.66 0.048 0.356 0.052 0.023 94.6 0.12 1.0 0.9

0.56 3.81 0.79 2.35 0.343 2.32 0.35 1.69 0.619 0.547 0.70 0.24 77.8 0.63 0.9 0.8

0.44 3.22 0.70 2.13 0.323 2.22 0.33 1.11 0.348 0.341 0.35 0.13 100 0.38 0.8 0.7

0.70 4.90 1.03 3.07 0.453 3.03 0.45 2.08 0.674 0.584 0.76 0.25 70.3 0.72 1.1 1.0

0.38 2.90 0.67 2.09 0.321 2.24 0.34 0.80 0.173 0.252 0.19 0.073 117 0.25 1.0 0.9

0.55 3.91 0.84 2.49 0.358 2.45 0.37 1.56 0.443 0.457 0.47 0.18 84.4 0.47 1.0 0.9

0.93 6.40 1.39 4.08 0.599 4.04 0.62 2.74 0.336 0.579 0.33 0.12 65.0 0.53 1.5 1.4

1.02 7.21 1.53 4.64 0.662 4.60 0.67 2.91 0.305 0.602 0.31 0.13 63.6 0.56 1.8 1.6

0.70 4.77 1.01 3.06 0.441 2.97 0.44 2.04 0.211 0.505 0.17 0.073 79.3 0.40 0.9 0.8

0.95 6.71 1.44 4.24 0.595 4.16 0.61 2.91 0.288 0.588 0.27 0.12 65.2 0.54 1.4 1.3

0.79 5.64 1.19 3.50 0.504 3.42 0.51 2.26 0.249 0.539 0.22 0.10 77.0 0.46 1.3 1.1

0.51 3.69 0.78 2.32 0.345 2.33 0.33 1.18 0.051 0.237 0.030 0.017 120 0.12 1.0 0.9

0.53 3.81 0.82 2.43 0.341 2.38 0.36 1.30 0.049 0.276 0.032 0.018 125 0.11 1.1 1.0

0.61 4.21 0.89 2.70 0.378 2.57 0.39 1.54 0.059 0.338 0.041 0.026 104 0.15 1.0 0.9

0.66 4.65 0.95 2.83 0.393 2.72 0.40 2.08 0.267 0.560 0.27 0.11 102 0.44 1.2 1.1

0.71 4.80 1.03 2.96 0.417 2.97 0.42 2.23 0.279 0.573 0.31 0.12 109 0.45 1.2 1.1

0.72 5.15 1.10 3.25 0.476 3.23 0.47 2.06 0.184 0.457 0.17 0.071 76.3 0.39 1.3 1.2

0.78 5.41 1.16 3.37 0.491 3.43 0.50 2.32 0.229 0.533 0.20 0.091 68.8 0.46 1.3 1.2

4.90 3.20 3.20 0.47 1.60 0.092 0.590 0.12 0.043 117 0.67 1.7 1.54 1.54

4.80 3.20 3.20 0.46 1.60 0.092 0.530 0.12 0.049 115 0.31 1.7 1.51 1.54

4.57 2.95 2.92 0.44 1.43 0.090 0.380 0.11 0.030 115 0.18 1.4 1.2

(continued on next page)

W. Sun et al. / Chemical Geology 196 (2003) 259–281 263

Table 1 (continued)

Sc V Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd

Central Lau Spreading Center

2231-13 45.0 371 0.92 87.0 34.6 74.5 1.18 0.010 8.28 2.47 8.58 1.55 8.33 3.36 1.23 4.88

2231-13 46.4 375 0.88 88.0 35.1 75.3 1.25 0.010 8.26 2.49 8.59 1.55 8.34 3.33 1.24 5.03

2231-8 47.2 343 0.89 81.0 29.3 55.0 0.94 0.010 7.64 1.79 6.38 1.17 6.48 2.66 1.03 4.08

2231-7 46.8 379 0.95 92.0 37.3 80.5 1.31 0.010 8.81 2.67 9.36 1.65 9.08 3.75 1.35 5.34

2231-6 46.9 373 0.89 86.0 34.5 72.7 1.19 0.010 8.38 2.43 8.42 1.51 8.13 3.36 1.23 4.80

2231-5 47.2 405 0.86 86.5 35.0 77.5 1.20 0.012 8.50 2.40 8.60 1.50 9.20 3.4 1.30 5.00

2231-3 49.1 360 0.80 97.8 30.4 65.2 1.00 0.010 8.00 2.10 7.30 1.30 8.00 3.0 1.20 4.40

2231-2 47.5 343 0.85 78.0 28.4 53.3 0.92 0.010 7.27 1.72 6.10 1.11 6.21 2.53 0.99 3.82

King’s Triple Junction

2218-12 38.0 382 16.7 153 38.8 103 4.10 0.37 76.5 6.54 18.1 2.77 13.1 4.39 1.50 5.84

2218-12 38.6 383 16.3 150 38.0 101 3.97 0.35 74.6 6.36 17.5 2.66 12.8 4.34 1.47 5.71

2218-11 41.6 256 6.65 136 24.1 59.7 2.12 0.15 34.8 3.60 10.2 1.58 7.64 2.71 0.98 3.60

2218-11 42.3 257 6.60 135 24.0 59.7 2.10 0.14 34.6 3.56 10.2 1.60 7.62 2.69 1.00 3.66

2218-10 41.1 262 3.10 140 24.3 66.5 2.10 0.05 25.6 3.50 10.0 1.60 8.60 2.70 1.00 3.70

2218-9 41.1 262 3.00 140 24.2 66.2 2.10 0.04 25.4 3.50 10.0 1.60 8.60 2.70 1.00 3.70

2118-8 41.6 253 10.4 135 21.4 52.8 1.96 0.29 38.3 3.25 9.3 1.43 7.00 2.49 0.91 3.23

2118-7 38.0 283 8.37 141 27.8 72.4 2.83 0.15 49.2 4.61 12.7 1.93 9.22 3.17 1.11 4.13

2218-4 40.6 260 3.00 139 24.1 66.0 2.00 0.04 25.3 3.40 10.0 1.50 8.50 2.70 1.00 3.60

2118-3 37.3 307 20.9 162 28.0 68.8 2.60 0.62 65.8 4.84 13.4 2.05 9.85 3.25 1.17 4.18

2218-2 40.4 301 7.80 140 27.4 73.1 2.70 0.13 48.3 4.40 12.0 1.80 9.80 3.10 1.10 4.10

2118-1 41.9 313 8.87 141 30.3 74.6 2.47 0.18 44.2 4.42 12.6 1.96 9.50 3.39 1.18 4.55

Woodlark (136505-1)

A 42.9 263 0.36 148 27.3 83.6 1.47 0.004 3.20 2.99 10.1 1.71 8.74 3.15 1.24 4.32

B 39.5 240 0.35 152 24.8 76.3 1.37 0.009 3.00 2.80 9.33 1.58 8.11 2.90 1.13 3.87

C 41.7 260 0.34 145 27.1 82.4 1.43 0.005 3.12 2.98 9.99 1.71 8.72 3.19 1.24 4.24

D 41.3 258 0.35 144 26.8 82.2 1.44 0.003 3.09 2.97 10.0 1.70 8.64 3.30 1.21 4.23

E 41.6 258 0.33 145 27.0 82.9 1.41 0.004 3.12 3.00 10.1 1.71 8.82 3.12 1.25 4.27

F 42.7 263 0.37 148 27.6 84.5 1.44 0.007 3.20 3.08 10.3 1.73 8.90 3.26 1.23 4.31

G 41.5 261 0.35 146 27.1 83.0 1.43 0.004 3.09 3.02 10.1 1.71 8.77 3.28 1.23 4.29

H 41.0 257 0.33 143 26.8 82.3 1.41 0.004 3.11 3.02 9.99 1.70 8.76 3.08 1.23 4.28

I 41.3 253 0.37 153 26.6 81.6 1.40 0.009 3.11 2.94 9.86 1.68 8.66 3.17 1.21 4.27

J 39.2 241 0.35 156 25.4 77.6 1.42 0.006 3.06 2.82 9.47 1.60 8.16 2.92 1.12 4.04

K 37.4 227 0.31 164 23.8 73.3 1.26 0.006 2.88 2.67 8.97 1.52 7.69 2.68 1.12 3.78

L 39.5 243 0.37 157 25.3 78.0 1.38 0.003 3.07 2.82 9.41 1.60 8.16 2.93 1.12 3.95

M 41.9 262 0.36 147 27.6 84.2 1.47 0.008 3.14 3.04 10.1 1.79 8.90 3.31 1.26 4.27

N 42.1 263 0.36 146 27.6 84.0 1.44 0.007 3.15 3.04 10.3 1.78 9.02 3.13 1.25 4.38

O 38.6 238 0.34 152 24.7 76.0 1.37 0.002 3.05 2.82 9.28 1.58 7.92 2.92 1.13 3.81

O 38.7 238 0.35 153 24.9 76.5 1.37 0.006 3.03 2.84 9.41 1.62 8.21 3.04 1.15 3.92

Coriolis Troughs

VD-23A 24.9 288 31.6 228 57.3 234 17.2 0.34 170 17.34 41.1 5.73 25.5 7.75 2.36 9.19

VD-23B 25.0 290 32.1 228 58.2 238 17.5 0.36 172 17.65 41.9 5.81 25.8 7.87 2.43 9.44

VD-23C 25.3 292 31.3 227 56.6 232 17.0 0.34 168 17.29 40.6 5.70 25.0 7.62 2.35 9.19

VD-22A 35.2 260 16.9 227 32.5 136 17.5 0.20 151 13.61 29.7 3.89 16.3 4.56 1.59 5.43

VD-22B 35.3 258 16.8 228 32.7 137 17.5 0.21 152 13.75 29.8 3.86 16.3 4.61 1.60 5.49

VD-22C 35.9 266 17.3 227 34.1 142 17.9 0.22 153 13.96 30.5 3.99 16.8 4.73 1.62 5.62

VD-21A 26.0 319 30.6 224 53.2 213 15.9 0.33 160 15.95 38.0 5.29 23.4 7.11 2.22 8.54

VD-21B 23.3 279 26.2 245 47.2 192 14.4 0.28 146 14.40 34.2 4.73 21.0 6.31 2.03 7.62

VD-21C 25.4 296 32.0 231 58.6 239 17.5 0.34 173 17.80 41.9 5.86 26.1 7.86 2.41 9.49

VD-21D 26.2 322 29.9 222 50.6 203 15.3 0.32 155 15.36 36.1 5.03 22.5 6.75 2.13 8.16

W. Sun et al. / Chemical Geology 196 (2003) 259–281264

Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U Cu Mo Re(U)b Re(C)c Re(ID)d

6.32 3.97 3.85 0.59 2.20 0.080 0.510 0.10 0.040 108 0.27 1.6 1.47 1.43

6.39 4.07 4.01 0.60 2.28 0.080 0.490 0.11 0.040 109 0.25 1.5 1.38 1.43

5.33 3.43 3.35 0.51 1.70 0.060 0.370 0.080 0.020 120 0.20 1.4 1.2

6.90 4.34 4.34 0.65 2.45 0.090 0.520 0.13 0.050 104 0.25 1.5 1.39 1.38

6.28 3.98 3.93 0.59 2.20 0.090 0.470 0.11 0.040 103 0.23 1.5 1.3

6.40 4.00 4.00 0.58 2.30 0.085 0.520 0.12 0.043 108 0.29 1.8 1.6

5.70 3.60 3.50 0.50 1.90 0.075 0.500 0.10 0.034 114 0.25 1.3 1.2

5.09 3.27 3.27 0.47 1.64 0.060 0.380 0.07 0.030 120 0.20 1.4 1.3

7.11 4.43 4.40 0.67 2.86 0.270 1.52 0.61 0.27 40.3 0.58 1.2 1.1

6.87 4.31 4.35 0.65 2.74 0.260 1.49 0.61 0.27

4.42 2.76 2.67 0.41 1.64 0.140 0.840 0.28 0.12 87.2 0.44 0.8 0.7

4.42 2.79 2.72 0.41 1.66 0.150 0.840 0.29 0.12

4.40 2.80 2.80 0.40 1.80 0.140 0.88 0.23 0.079 77.0 0.56 0.8 0.7

4.50 2.80 2.80 0.40 1.80 0.140 0.83 0.23 0.079 81.1 0.45 0.8 0.7

3.89 2.42 2.37 0.36 1.47 0.130 0.77 0.32 0.16 87.7 0.36 0.8 0.7

5.15 3.13 3.13 0.48 1.95 0.180 1.10 0.37 0.15 65.6 0.40 0.9 0.8

4.40 2.80 2.80 0.40 1.70 0.140 0.84 0.23 0.077 73.0 0.42 0.7 0.57 0.58

5.08 3.21 3.11 0.48 1.92 0.160 1.25 0.53 0.31 83.8 0.51 1.0 0.9

5.00 3.10 3.20 0.45 2.00 0.190 1.00 0.37 0.14 68.1 0.48 0.9 0.82 0.87

5.46 3.44 3.44 0.50 2.07 0.170 1.09 0.36 0.15 67.0 0.42 1.0 0.9

0.72 4.97 1.03 3.01 0.43 2.88 0.41 2.18 0.110 0.49 0.078 0.053 110 0.30 0.9 0.8

0.65 4.48 0.93 2.73 0.39 2.61 0.38 2.00 0.100 0.49 0.079 0.039 110 0.30 0.8 0.7

0.73 4.91 1.05 2.96 0.42 2.84 0.43 2.17 0.094 0.51 0.082 0.048 104 0.30 1.0 0.9

0.71 4.87 1.03 2.96 0.44 2.79 0.41 2.15 0.108 0.54 0.075 0.201 104 0.30 0.7 0.6

0.74 4.92 1.02 2.96 0.42 2.88 0.41 2.15 0.112 0.50 0.081 0.040 104 0.30 0.8 0.7

0.74 4.99 1.05 3.09 0.43 2.95 0.43 2.21 0.109 0.52 0.085 0.048 111 0.30 0.7 0.6

0.72 4.96 1.02 2.97 0.42 2.86 0.40 2.15 0.102 0.50 0.075 0.043 105 0.30 0.7 0.6

0.73 4.81 1.03 2.97 0.41 2.82 0.40 2.15 0.104 0.50 0.081 0.046 100 0.30 0.8 0.7

0.73 4.79 1.00 2.90 0.43 2.84 0.42 2.19 0.097 0.49 0.075 0.044 112 0.28 0.7 0.6

0.67 4.60 0.97 2.71 0.40 2.61 0.39 2.04 0.107 0.47 0.077 0.044 111 0.26 0.7 0.6

0.61 4.30 0.91 2.63 0.37 2.49 0.35 1.93 0.091 0.47 0.064 0.045 105 0.27 0.5 0.5

0.65 4.51 0.94 2.75 0.40 2.66 0.38 1.96 0.101 0.44 0.073 0.050 113 0.28 0.6 0.5

0.72 5.07 1.04 3.03 0.43 2.88 0.42 2.15 0.103 0.52 0.079 0.047 106 0.29 0.7 0.6

0.75 4.99 1.02 3.06 0.43 2.87 0.42 2.14 0.110 0.51 0.072 0.045 103 0.30 0.5 0.5

0.66 4.54 0.95 2.67 0.39 2.61 0.38 1.91 0.098 0.46 0.064 0.044 110 0.28 0.7 0.6

0.66 4.42 0.96 2.72 0.39 2.68 0.38 1.98 0.099 0.49 0.076 0.046 110 0.28 0.7 0.6

1.51 10.2 2.14 6.32 0.93 6.28 0.92 5.72 1.08 2.71 2.10 0.71 31.1 1.81 1.2 1.1

1.54 10.4 2.18 6.37 0.94 6.36 0.94 5.85 1.11 2.77 2.10 0.72 31.5 1.80 1.2 1.1

1.51 10.1 2.11 6.17 0.91 6.18 0.91 5.75 1.08 2.67 2.07 0.71 33.7 1.75 1.2 1.1

0.89 5.87 1.22 3.60 0.50 3.51 0.51 3.25 1.08 1.68 1.62 0.46 97.0 1.33 0.8 0.7

0.89 5.95 1.23 3.57 0.51 3.51 0.51 3.32 1.09 1.70 1.62 0.46 96.5 1.36 0.8 0.7

0.92 6.10 1.28 3.71 0.53 3.62 0.54 3.43 1.10 1.71 1.65 0.48 97.8 1.35 0.8 0.7

1.41 9.43 1.96 5.77 0.85 5.73 0.84 5.16 0.99 2.46 1.88 0.64 38.3 1.49 1.1 1.0

1.24 8.41 1.75 5.17 0.75 5.07 0.73 4.79 0.88 2.14 1.70 0.59 33.2 1.44 1.2 1.1

1.54 10.4 2.16 6.48 0.92 6.26 0.93 5.78 1.09 2.66 2.12 0.70 32.5 1.80 1.3 1.2

1.34 9.05 1.88 5.56 0.80 5.45 0.80 4.99 0.95 2.38 1.82 0.63 44.1 1.60 1.3 1.2

(continued on next page)

W. Sun et al. / Chemical Geology 196 (2003) 259–281 265

samples from the so-called ‘‘megaplume site’’ at

North Cleft (Embley et al., 1991; Smith et al.,

1994). Glasses from Axial Volcano are from the

central caldera, which lies along the ridge axis of

the Axial Segment. Although these samples are from a

seamount that is part of a ‘‘hotspot’’ chain, they

exhibit only slightly enriched characteristics and they

are isotopically similar to the Cleft MORB (Chadwick

et al., 1999, and in preparation).

Samples from the Ecuador Rift, just east of the

Galapagos Spreading Center are also included in the

sample suite and represent a relatively primitive and

depleted variety of N-MORB (Perfit et al. 1983).

All of the N-MORB samples are fresh glasses with

less than 2% phenocrysts or vesicles. A few of the E-

MORB from Siqueiros and off-axis EPR have sig-

nificantly more phenocrysts, but typically less than

10% by volume. Glasses used in the analyses were

picked free of visible phenocrysts and any alternation.

3. Analytical methods

MORB and Lau Basin glass samples were selected

from previously prepared glass separates (Falloon et

al., 1992; Honda et al., 1993; Perfit et al., 1994; Smith

et al., 1994). Samples from the Coriolis Troughs and

Woodlark Basins were carefully broken and washed

using an ultrasonic bath in 1 N HCl and then high

purity (18 MV) water. Up to eight pieces of fresh

glass for each sample, ranging from 1 to 5 mm in size,

were mounted in epoxy after careful examination

under a binocular microscope to avoid alteration and

weathering. The mounts were then sectioned and

polished using new polishing pads to avoid potential

sample contamination. Before analysis, sample

mounts were cleaned in an ultrasonic bath in petro-

leum spirits and then detergent solution for 2 min

each, washed with high purity (18 MV) water, and

then dried at 60 jC for 15 min. These procedures

served to minimize surface contamination, particularly

for Re and Pb.

Major elements were analyzed using a JEOL6400

electron microscope in EDS mode in the Electron

Microscope Unit, Australian National University.

Operating conditions were: 15 kV accelerating volt-

age, 1 nA sample current, and 110 s counting time in

defocused mode (0.5� 0.5 Am) to avoid Na and K

loss. Analytical data for different glass fragments from

the same samples were very similar for most of the

Table 1 (continued)

Sc V Rb Sr Y Zr Nb Cs Ba La Ce Pr Nd Sm Eu Gd

Coriolis Troughs

VD-21E 25.3 310 31.8 228 55.7 227 17.1 0.34 168 16.98 40.7 5.62 24.9 7.45 2.32 9.01

VD-21F 25.5 325 29.2 226 49.7 200 15.1 0.30 153 15.13 35.9 4.98 22.1 6.67 2.09 8.04

NIST 612e 41.1 38.2 31.6 76.5 38.3 36.0 38.1 41.6 37.7 35.8 38.4 37.2 35.2 36.7 34.4 37.0

BCR-2g 34.3 438 52.7 334 32.1 164 12.3 1.25 663 24.4 52.8 6.48 25.1 6.39 1.87 6.12

BCR-2g 34.5 438 51.6 328 31.8 162 12.2 1.23 653 23.9 52.0 6.40 24.9 6.20 1.83 6.08

BCR-2g 34.5 438 51.9 330 31.9 163 12.3 1.25 657 24.3 52.4 6.42 25.1 6.23 1.84 6.21

BCR-2g 34.0 435 51.7 328 31.5 161 12.2 1.25 656 24.1 52.4 6.40 24.9 6.18 1.83 6.12

BCR-2g 34.4 430 52.1 334 32.8 168 12.0 1.23 676 25.1 53.6 6.61 28.5 6.39 1.87 6.51

BCR-2gf 34.4 436 52.0 331 32.0 164 12.2 1.24 661 24.4 52.6 6.46 25.7 6.28 1.85 6.21

BCR-2gg 33.5 429 48.1 335 39.4 201 13.1 1.13 672 24.4 51.9 6.48 28.4 6.58 1.98 6.67

BCR-2gh 33F2

416F14

48F2

346F14

37F2

188F16

1.1F0.1

683F28

25F1

53F2

6.8F0.3

28F2

6.7F0.3

2.0F0.1

6.8F0.3

DL (ppb)i 5 2 3 0.4 0.3 0.5 0.4 1 0.4 0.3 0.2 0.1 0.7 1 0.2 0.7

a Rhenium concentrations are given as ng/g; others are given as Ag/g.b U = uncorrected.c C = corrected.d ID = isotope dilution.e NIST 612 value for Re from Sylvester and Eggins (1997), others from Pearce et al. (1997).f Average of five analyses. Most of the elements are identical with literature results. Rhenium is not homogenous in BCR-2g.g Solution ICP-MS results from Norman (1998), except Mo is from O’Neill and Eggins (2002).h USGS recommended and information (in italic) values.i DL= detection limit calculated as (3jbackgroud/sensitivity)� ((1/nbackground)+(1/nablation))^0.5 (Longerich et al., 1996).

W. Sun et al. / Chemical Geology 196 (2003) 259–281266

major oxides, suggesting that these volcanic glasses

are quite homogenous. Data for minor oxides such as

P2O5, K2O differed by up to 50% especially when

their concentrations are below 0.1%. The consistency

between the electron microprobe results and previous

X-ray fluorescence (XRF) data for Lau Basin samples

(Falloon et al., 1992) and MORB samples (Perfit et

al., 1994; Smith et al., 1994) indicates the reliability of

these analyses.

Trace elements were analyzed using laser ablation

ICP-MS system at the Research School of Earth

Sciences, Australian National University. This system

consists of a Lambda Physik LPX 120I pulsed ArF

excimer laser coupled to a Agilent 7500 ICP-MS.

Isotopes were measured in peak-hopping mode using

one point-per-peak. NIST 612 was used as the exter-

nal standard and minor isotope of Ca (43Ca) was used

as an internal standard. Rhenium concentration in

NIST 612 is from (Sylvester and Eggins, 1997). The

concentration data for other trace elements in NIST

612 used for determining sample concentrations are

from Pearce et al. (1997) (Table 1).

Most of the trace elements were analyzed using a

103 Am diameter spot and a laser repetition rate of 5 Hz

(Table 1). Re, Cu, Mo, Ta, Hf and Yb were analyzed

separately using a larger spot (170 Am diameter) and a

faster laser repetition rate of 20 Hz (Table 1) to improve

the detection limits (Sylvester and Eggins, 1997). The

interference of 171Yb16O on 187Re has been corrected

based on their production ratios determined before and

after each group of analyses using NIST 610. The 188/

172 (172Yb16O/172Yb) and 189/173 (173Yb16O/173Yb)

ratios were determined. They give the same values,

suggesting that there is little Os in the NIST 610 and the

above ratios are the really production ratios of Yb

oxide. Interference corrections were usually less than

5% for 187Re. Errors for 187Re calculated from counting

statistics range from 4% to 15%. Detection limit of Re

calculated based on the gas backgrounds and sensitiv-

ity (Longerich et al., 1996) is 0.001 ng/g. No surface

contamination is observed.

Rhenium is not perfectly homogenous in the NIST

612 standard. Variations of 3.5% have been reported

(Sylvester and Eggins, 1997) and in some domains Re

contents range between 5% and 100% of the accepted

concentration used in this study (Eggins and Shelley,

2002). To confirm the reliability of our laser results,

the NIST 612 standard used in this paper was care-

fully examined for its homogeneity by using laser

spots and scans. Rhenium contents of five of the Lau

Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U Cu Mo Re(U)b Re(C)c Re(ID)d

1.45 9.94 2.08 6.11 0.87 6.05 0.89 5.55 1.06 2.58 2.00 0.69 37.1 1.78 1.3 1.2

1.30 8.83 1.84 5.45 0.77 5.35 0.79 4.83 0.93 2.36 1.78 0.62 41.9 1.44 1.2 1.1

35.9 36.0 37.9 37.4 37.6 40.0 37.7 34.8 39.8 39.0 37.2 37.2 36.7 38.3 6570

0.92 6.12 1.21 3.34 0.50 3.31 0.49 4.36 0.798 11.8 5.62 1.71 19.4 265

0.90 6.00 1.20 3.37 0.48 3.29 0.48 4.28 0.761 11.1 5.49 1.68 19.3 266

0.94 6.14 1.21 3.45 0.49 3.34 0.48 4.41 0.770 11.6 5.61 1.71 19.5 264

0.92 6.00 1.21 3.37 0.48 3.34 0.49 4.38 0.773 11.6 5.63 1.71 19.2 261

6.39 3.52 3.47 0.49 4.61 0.775 11.9 5.78 1.72 19.3 266

0.92 6.13 1.21 3.41 0.49 3.35 0.49 4.4 0.78 11.6 5.63 1.71 19 264

1.06 6.33 1.32 3.73 3.34 0.50 4.9 0.81 10.3 6.03 1.69 19.4 262

1.07F0.04

1.33F0.01

0.54 3.5F0.2

0.51F0.02

4.8F0.2

11F2

6.2F0.7

1.69F0.19

19F2

248F17

0.5 0.7 0.2 0.5 0.2 0.8 0.3 0.7 0.2 1 0.2 0.2 0.1 0.002 0.001

W. Sun et al. / Chemical Geology 196 (2003) 259–281 267

Basin samples were also analyzed using isotope

dilution solution (ID) ICP-MS methods. The isotope

dilution results are well correlated with the laser

results, and agree within errors of the methodologies

(Fig. 1) confirming our ability to make accurate Re

determinations at the sub-ppb concentrations. Using a

Re concentration for NIST 612 of 6.57 ppm (Sylvester

and Eggins, 1997) there is a suggestion in the data of a

systematic displacement to higher concentrations by

about 10% for the laser analyses, although the differ-

ence is within the error limits. Corrections have been

applied to all analyses using the correlation between

laser and ID results to adjust the laser data to be

consistent with the ID data.

The standard BCR-2g (glass) was analysed as an

unknown to check trace element data quality and the

data, including those for Mo and Cu show excellent

reproducibility and are consistent with previous re-

sults (Norman, 1998; O’Neill and Eggins, 2002). The

duplicate analyses and average compared with con-

centrations determined by solution ICP-MS are pre-

sented in Table 1. The consistency of these results

indicates that both the standard and the samples are

homogenous within the reproducibility of the techni-

que. However, rhenium appears to be heterogeneous

in BCR-2g (8 to 17 ppb), possibly due to Re loss

during the melting and the cooling of the glass and/or

sequestering by the Mo furnace.

4. Results

4.1. MORB

The MORB samples studied here are classified into

three types based on their trace element patterns;

enriched MORB (E-MORB) (Fig. 2D and G), normal

MORB (N-MORB) (Fig. 2A–D and H) and depleted

MORB (D-MORB) (Fig. 2E and F). Note that the

samples classified in this study as D-MORB would

generally be considered to be variations of N-type

MORB and are not the extremely depleted types

reported from other locales, e.g. some near axis

seamounts and transform faults. In an N-MORB-

normalized (Sun and McDonough, 1989) abundance

diagram, all the trace elements of the analysed N-

MORB samples are close to 1 as expected, with the

exception of a slight Pb positive anomaly in sample

2392-9, which is from the East Pacific Rise (Fig. 3A–

D and H). E-MORB samples are enriched in Cs, Rb,

Ba, Th, U (Fig. 3D and G), whereas D-MORB are

strongly depleted in incompatible elements and have

slight positive Pb anomalies (Fig. 3E and F). In

chondrite-normalized diagrams show flat REE pat-

terns with slight LREE depletion for N-MORB sam-

ples (Fig. 2), LREE enrichment for E-MORB samples

(Fig. 2D and G) and strong LREE depletion for D-

MORB samples (Fig. 2E and F). The trace elements

of the FAMOUS glasses cover a large range as

previously described (Langmuir et al., 1977).

The analysed N-MORB samples, with the excep-

tion of sample 2392-9, have Ce/Pb ratios from 21 to

24 (mean = 24F 1, n = 26), which is close to the

global average value of 25 for MORB and OIB

(Hofmann, 1997). The E-MORB suite has a virtually

identical mean Ce/Pb of 24F 2 (20 to 27, n = 9). The

low D-MORB average of 16.4F 0.7 (15.9 to 17,

n = 5) and sample 2392-9 with Ce/Pb = 11 is consistent

with their positive Pb anomalies on mantle normalized

diagrams (Fig. 3E and F). The Nb/U of E- and N-

MORB are also fairly close to the global average

MORB and OIB value of 47F 10 (Hofmann, 1997),

ranging from 35.5 to 43.2 (mean = 40F 2) for the

analyzed E-MORB and 35.7 to 45.7 (mean = 40F 1)

for the analyzed N-MORB. Nb/U ratios of the D-

MORB suite range from 22.2 to 33.9 (mean = 29F 5),

which is clearly lower compared with other MORB

types.

Fig. 1. Laser ablation ICP-MS determinations versus isotope

dilution solution ICP-MS results for Re concentrations. The good

correlation supports the reliability of laser results at concentration

levels as low as sub-ppb.

W. Sun et al. / Chemical Geology 196 (2003) 259–281268

Fig. 2. Chondrite normalized REE abundance patterns for MORB and back-arc basin basalts (BABB) determined using laser ablation ICP-MS.

Chondrite values are from McDonough and Sun (1995) and Sun and McDonough (1989).

W. Sun et al. / Chemical Geology 196 (2003) 259–281 269

Fig. 3. N-MORB normalized trace element abundance patterns for MORB and BABB analyzed using laser ablation ICP-MS. N-MORB

normalizing values from Sun and McDonough (1989).

W. Sun et al. / Chemical Geology 196 (2003) 259–281270

Fig. 3 (continued).

W. Sun et al. / Chemical Geology 196 (2003) 259–281 271

The measured Re concentrations of the 30 MORB

samples analysed here (0.7–1.6 ppb) are within the

range of published concentrations determined using

isotope dilution methods (0.163 to 2.283 ppb; Schiano

et al., 1997) and have a similar average value

(0.89F 0.06 ppb for ID; 0.93F 0.05 ppb for LA-

ICP MS). The laser results exhibit a positive linear

correlation between Re and Yb and are within the

MORB field defined by published isotope dilution

data (Fig. 4B). These observations testify to the

reliability of our laser ablation ICP-MS results. There

is no obvious systematic difference between E-MORB

and N-MORB in terms of Re contents or Yb/Re ratios.

4.2. The Eastern and Central Lau Spreading Centers

The Lau Spreading Center samples analyzed here

are similar to N-MORB based on their major and

trace element concentrations (Falloon et al., 1992).

The parental magmas have been suggested to be

picritic (13–16 wt.%) based on experimental study

on a refractory sample, with the current low MgO

contents of these samples resulting from large

degrees of fractional crystallization (Falloon et al.,

1999). Chondrite-normalized REE patterns have

slight LREE depletion, similar to N-MORB (Fig.

2I). These patterns are in agreement with published

results (Falloon et al., 1992) with the exception of

slight negative Eu anomalies which have not been

observed previously. A possible explanation is that

the LA ICP-MS method has a smaller chance of

sampling plagioclase microphenocrysts than the

whole-rock powder solution method previously used.

Most of the incompatible elements are close to unity

on the N-MORB normalized diagram with the excep-

tion of Nb and Ta, which show slight negative

anomalies (Fig. 3I). Slight enrichments of Cs, Rb,

Ba and Pb are present in samples from the Eastern

Lau Spreading Center (ELSC), which is closer to the

Tonga Arc. These characteristics have been described

and interpreted as resulting from the involvement of

H2OFLILEFLREE-enriched hydrous fluids de-

rived from a subducting slab (Falloon et al., 1992).

The Sr contents of the Lau BABB are similar to N-

MORB, and much lower than those of arc volcanics

in general (McCulloch and Gamble, 1991), indicating

little Sr has been added from a subduction-related

hydrous fluid.

Fig. 4. Re versus Yb diagram for MORB and BABB analyzed using

laser ablation ICP-MS results. CLSC=Central Lau Spreading

Center; ELSC=Eastern Lau Spreading Center; KJT=King’s Triple

Junction; PUM=primitive upper mantle. Also plotted are MORB*

(+) and komatiites* (� ) from literature analyzed using solution

isotope dilution method. Data sources: MORB* data are from

Schiano et al. (1997). Yb concentrations for MORB are calculated

from Tb (Schiano et al., 1997) assuming a chondritic Yb/Tb. Up to

10% error can be induced by this calculation depending on the REE

patterns of MORB samples. Re concentrations of Gorgona

komatiite are from Walker et al. (1999). Corresponding Yb data

are from Aitken and Echeverria (1984), Arndt et al. (1997),

Echeverria (1980) and Kerr et al. (1996). Re concentrations of

Munro komatiites are from Shirey and Walker (1995), correspond-

ing Yb values are calculated based on Sm, Nd concentrations

(Walker et al., 1989) and REE patterns for Munro komatiites (Arndt,

1986; Arndt and Nesbitt, 1984; Xie et al., 1993). The komatiites

exhibit a positive correlation between Re and Yb, with a slope

similar to that of Lau Basin Spreading Center samples. PUM

compositions are from McDonough and Sun (1995).

W. Sun et al. / Chemical Geology 196 (2003) 259–281272

The Ce/Pb (11 to 18) of the LSC samples is lower

than that of MORB and OIB. Similarly, the Nb/U is

also lower than in MORB and OIB (26 to 31) with

two exceptions (39 for 2239-1, and 47 for 2231-8).

The values of Ce/Pb and Nb/U have been regarded as

indicators of inputs of subduction-related materials,

either as fluids or melts of sediments (Plank and

Langmuir, 1998). This is because Pb and Ce have

similar incompatibilities during mantle melting as do

Nb and U; however, Pb and U are much more fluid

mobile in the subduction environment resulting in

characteristic low Ce/Pb and Nb/U in fluid-influenced

arc lavas (Johnson and Plank, 1999). Therefore, the

low Ce/Pb, Nb/U support the involvement of fluids

released from the subducted slab.

A significant characteristic of Lau Spreading Cen-

ter samples is that Re concentrations (1.37F 0.04 ppb

in average) are higher than published concentrations

in both MORB (0.89F 0.06 ppb, n = 35) (Schiano et

al., 1997) and arc volcanic rocks (0.30F 0.02 ppb,

n = 147) (Alves et al., 1999, 2002; Woodland et al.,

2002) (Table 1). Furthermore, Re and Yb are posi-

tively correlated but with a steeper slope (lower Yb/

Re) compared to that of MORB (Fig. 4A).

4.3. The King’s Triple Junction

The King’s Triple Junction (KTJ) samples represent

magmas generated in a hybrid tectonic environment,

which allows further examination of the potential role

of fluids in controlling Re compositions. The major

elements of the KTJ samples are similar to N-MORB,

and are clearly different from typical BABB except

sample 2218-2, which is more similar to E-MORB

(Falloon et al., 1992). Chondrite-normalized REE

patterns are flat (Fig. 2J); highly incompatible ele-

ments differ from those of N-MORB, with enrich-

ments of Cs, Rb, Ba, Th, U and Pb from less than a

factor of 2 to nearly a factor of 100 in the N-MORB-

normalized diagram (Fig. 3J). The Ce/Pb is low and

nearly constant (11 to 12), while Nb/U ranges from 8

to 27, but all are lower than those of MORB and OIB.

These observations argue for the involvement of

H2OFLILEFLREE-enriched hydrous fluids (Fal-

loon et al., 1992).

Rhenium concentrations of samples from the KTJ

(0.57 to 1.1 ppb, n = 10) are within the MORB range

and are positively correlated with Yb similar to that of

MORB (Fig. 4B). The similarity between MORB and

KTJ samples in terms of Re and Yb indicates that no

additional Re was added to the KTJ samples by the

fluids which likely contributed to the LILE enrich-

ments.

4.4. The Woodlark Basin

Woodlark Basin samples have a narrow range of

major element compositions, with SiO2 contents

between 50.07 and 50.92 wt.% and MgO contents

of 7.6 to 8.4 wt.%. Light-REE depletions in the

samples are similar to N-MORB (Fig. 2K), but with

other highly incompatible trace elements displaying

greater degrees of depletion. In the N-MORB nor-

malized diagram, most of the less incompatible

elements (to the right of La in Fig. 3K) are close

to 1, while Cs, Rb, Ba, Th, Nb, Ta are mostly lower

than 1 with slight positive U, Sr, Pb anomalies.

Only one sample has a U content higher than N-

MORB (Fig. 3K). These suggest that the Woodlark

samples are very depleted in highly incompatible

trace elements.

Rhenium and Yb concentrations of the Woodlark

basalts fall within the MORB field and at the lower

end of the CLSC trend (Fig. 4A); the narrow range of

concentrations does not define a trend (Fig. 4A).

4.5. The Coriolis Troughs Basin

The Coriolis Troughs (CT) samples are more

evolved than samples from the other BAB localities

with higher TiO2 (1.7% to 2.7%) and lower MgO (3.1

to 6.5 wt.%) contents. Their SiO2 contents range from

50.81 to 54.89 wt.%. Up to six pieces of glass were

measured for each of the three CT samples (all

duplicate analyses for the three samples are listed in

Table 1). The results from different glass chips for

each sample confirms both sample homogeneity and

LA ICP-MS reproducibility. In the N-MORB-normal-

ized diagram (Fig. 3L), all the elements are above 1

with Cs, Rb, Ba Th values that are higher than 10 and

a slight positive Pb anomaly. Nb and Ta concentra-

tions are also much higher than those of N-MORB,

without any evidence for Nb and Ta depletions (Fig.

3L) in their extended trace element patterns, indicat-

ing that they were derived from an enriched mantle

source, although they are close to an active arc. All

W. Sun et al. / Chemical Geology 196 (2003) 259–281 273

samples have LREE enrichment in the chondrite-

normalised diagram (Fig. 2L).

Rhenium concentrations of the 3 CT samples are

lower than those of LSC samples. Sample VD-22,

which contains few vesicles, falls in the MORB range

on a Re versus Yb diagram. The other two samples,

both with abundant vesicles (>5%), are displaced to

lower Re concentrations (Fig. 4B) compared to

MORB and possibly have experienced some Re loss.

5. Discussion

Systematics of two lithophile–chalcophile element

pairs (Yb/Re and Ce/Mo) are shown for the MORB

and BABB sample suites in Fig. 5. The constant Yb/

Re and Ce/Mo for the E- and N-MORB and KTJ

samples (Fig. 5) confirm that Re has an incompati-

bility similar to that of Yb and Mo behaves similarly

to Ce, as previously suggested by Hauri and Hart

(1997) and Sims et al. (1990), and McDonough and

Sun (1995), respectively. In contrast, the more depleted

samples (D-MORB, Woodlark and Lau Spreading

Centers samples) are different from E- and N-MORB

in that Re and Mo appear to be more incompatible

than Yb and Ce, respectively. In the following

sections we examine the possible cause for this

differing behavior.

5.1. Contributions from the slab?

The high Re concentrations of samples from the

Eastern and Central Lau Spreading Centers are appa-

rently consistent with the general suggestion of Re

losses from subducted slabs (Becker, 2000) followed

by the involvement of these subduction-derived com-

ponents to the source regions of these BAB magmas

(Falloon et al., 1992). However, if this were the case,

we might not anticipate such a strong correlation

between Re and Yb in the BABB glasses, but would

rather a range of Re concentrations for a given Yb. If

Re was controlled by fluid fluxing from the slab,

then systematic Re and Yb variations would require

that both elements behave similarly within a sub-

duction-derived fluid (Fig. 4A). Yet, experimental

evidence indicates that Yb is one of the least mobile

elements during subduction (Johnson and Plank,

1999).

This line of argument can be extended to include

the correlations between Re and other mobile trace

elements. For example, it is well documented that Pb

is one of the most mobile elements during subduction,

whereas Ce is less mobile (Johnson and Plank, 1999;

McCulloch and Gamble, 1991). This results in dehy-

dration fluids and melts of sediments both having low

Ce/Pb (Plank and Langmuir, 1998). If subduction-

derived fluids and/or melts contribute to the observed

Fig. 5. Diagrams of (A) ln(Yb/Re) versus ln(Re), (B) ln(Ce/Mo)

versus ln(Mo). The similarities between chalcophile trace elements

Re, Mo and lithophile trace elements Yb and Ce, respectively, are

well illustrated by the constant Yb/Re and Ce/Mo of the less depleted

samples (E- and N-MORB as well as KTJ and Coriolis Troughs

samples, light gray field). Whereas Re andMo are more incompatible

than Yb and Ce, respectively, for the more depleted samples (D-

MORB, CLSC, ELSC and Woodlark samples, dark gray field).

W. Sun et al. / Chemical Geology 196 (2003) 259–281274

high Re concentrations, then a negative correlation

between Re and Ce/Pb is expected. For the BABB

glasses analysed here, there is no correlation between

Re and Ce/Pb with the two exceptions of samples

from the ELSC (offset relative to CLSC) and CT

samples, which show a weak negative sense (Fig. 6).

These localities are notable for being in much closer

proximity to volcanic arcs than the other sample

localities, suggesting that subduction-derived compo-

nents might have slightly modified the Re concentra-

tions in these two examples. Overall, all observations

argue against major contributions of Re from the

subduction-released fluid in the generation of back-

arc basin glasses.

5.2. Effects of variable melt extraction

The linear arrays on Re–Yb variation diagrams

(Fig. 4) for the various sample suites likely reflect the

effect of partial melting and fractional crystallisation

(Hauri and Hart, 1997). The samples from the Lau

Spreading Centers (LSC) are distinct and form slopes

steeper than the MORB trends and similar to some

komatiite suites. The difference between MORB and

komatiite in terms of Re–Yb correlations has been

explained by the presence and absence of residual

sulfide, respectively (Schaefer et al., 2000). The

reasoning is that Re is chalcophile, whereas Yb is

lithophile such that where there is no sulfide in the

residue, Re becomes more strongly incompatible. By

analogy, the Re–Yb relationships in the Lau Spread-

ing Center samples may also reflect melting in the

absence of residual sulfide. In addition, Re might be

more incompatible in BABB magmas than in MORBs

owing to the higher oxygen fugacity during mantle

(Righter, 1999) of the mantle wedge as a result of the

involvement of water- or sulfate-rich fluids (Parkinson

and Arculus, 1999). For the following reasons, the

former interpretation is preferred.

The partition coefficients of chalcophile elements

are controlled primarily by the presence of sulfide.

They will decrease markedly when residual sulfides

are exhausted due to melt removal. The relative

incompatibility of two trace elements X and Y can

be inferred using CX/CY versus CY plots (Hofmann et

al., 1986) or ln(CX/CY) versus ln(CY), where CX and

CY are the concentrations of trace elements X and Y,

respectively (Minster and Allegre, 1978; Hofmann

and White, 1983; Hofmann, 1988; Niu and Batiza,

1997). When element X is more incompatible than

element Y, a positive correlation occurs (DX <DY);

when X is less compatible than Y (DX>DY) a negative

correlation and when DX =DY, no correlation is

observed between ln(CX/CY) and ln(CY).

The ratios Cu/Re, Yb/Re and Ce/Mo comprise

element pairs that have been demonstrated to behave

coherently in a range of geochemical settings (e.g.

McDonough and Sun, 1995; Hauri and Hart, 1997;

Bennett et al., 2000). Copper and Re are both mod-

erately incompatible, moderately chalcophile ele-

ments. Owing to the absence of geochemical datasets

with both Re and Cu, their behavior in MORB and

BABB suites has not been systematically investigated.

Here, Cu and Re were determined simultaneously for

all samples.

Cu/Re is negatively correlated with Re (Fig. 7),

indicating that Re is more incompatible than Cu. More

interestingly, the current sample set is clearly divisible

into two groups (Fig. 7) with the samples from more

depleted sources, i.e. Woodlark, LSC and D-MORB,

displaced to higher Cu/Re and with a flatter slope

compared to the other samples. CT, KTJ and E- and

N-MORB samples lie on a steeper trend with the CT

samples and E-MORB having the lowest Cu/Re (Fig.

7). The MORB and KTJ samples lie below and above

the primitive mantle values, respectively.

Fig. 6. Re versus Ce/Pb for MORB and BABB. The absence of a

correlation suggests Re concentrations are not affected by fluid

mobility.

W. Sun et al. / Chemical Geology 196 (2003) 259–281 275

As the slopes of the correlation lines between

ln(Cu/Re)� ln(Re) are controlled by the partition

coefficients of Cu and Re (Fig. 7), the different slopes

suggest significant differences in partition coeffi-

cients. In general, the partition coefficients of trace

elements are constant at different degrees of partial

melting, unless the mineral composition of the source

is changed. For the chalcophile elements Cu and Re,

sulfide is the main controlling phase. The MORB

source (both E- and N-MORB) is generally consid-

ered to contain a significant amount of residual sulfide

(Helz, 1977; McGoldrick et al., 1979; Mitchell and

Keays, 1981; Wendlandt, 1982; Yi et al., 2000).

Subsequently, E- and N-MORB magmas are S-satu-

rated (Mathez, 1976) and sulfide melts can possibly

segregate from silicate melts (Yi et al., 2000) and

contribute to the fractionation of Re and Cu. The other

group of samples (Woodlark, LSC and D-MORB

samples) are more depleted in incompatible elements

compared to N-MORB (Figs. 2 and 3). A plausible

interpretation is that the melting of previously

depleted mantle resulted in the exhaustion of sulfides

in the source regions of these incompatible element

depleted basalts. This results in the partition coeffi-

cients of Re, Cu and other chalcophile elements of the

depleted samples being controlled by silicates only,

while those for the KTJ and CT samples are controlled

by both sulfide and silicates and similar to those in N-

MORB and E-MORB.

Support for this scenario comes from the correla-

tions between Yb/Re versus Re and Ce/Mo versus Mo

(Fig. 5). Rhenium and Mo are geochemically similar

to Yb and Ce, respectively, during the evolution of

MORB magmas (Hauri and Hart, 1997; McDonough

and Sun, 1995). This is confirmed by our LA ICP-MS

results: E- and N-MORB as well as King’s Triple

Junction samples show no correlation between ln(Ce/

Mo) and ln(Mo), and ln(Yb/Re) and ln(Re) with near

constant Mo/Ce and Yb/Re (Fig. 5). Coriolis Troughs

samples show a similar pattern, however, they are

displaced to high Yb/Re (Fig. 5) possibly reflecting

Re loss. In contrast, the samples from more depleted

sources show negative correlation between ln(Ce/Mo)

and ln(Mo), and ln(Yb/Re) and ln(Re) (Fig. 5),

indicating that Mo is more incompatible than Ce,

while Re is more incompatible than Yb. These obser-

vations are consistent with the increased incompati-

bility of chalcophile elements when there is no residual

sulfide in the source.

5.3. Rhenium concentration in the depleted mantle

Owing to the similar geochemical behavior of Re

and Yb in MORB and therefore the very similar

incompatibility of these two elements during magma

evolution in the presence of residual sulfide, the

average Yb/Re value for the MORB source mantle

(DMM) should be equivalent to that of N-MORB.

The average Yb/Re values are 3.4F 0.1 and 3.9F 0.2

ppm/ppb for MORB and King’s Triple Junction

samples, respectively. These are similar to the average

of isotope dilution data (Schiano et al., 1997;

4.0F 0.2 ppm/ppb, n = 35 with Yb values estimated

using Tb concentrations) and previously estimated

values for MORB (f 3.6; Hauri and Hart, 1997).

Based on all available data, the average Yb/Re value

for the DMM is therefore estimated to be 3.6F 0.1

ppm/ppb (n = 83). This is about two times higher than

that of the primitive mantle (PM= 1.8; McDonough

and Sun, 1995). Assuming that the DMM is 10%

depleted in Yb relative to the PM (YbPM = 0.493 ppm.

(Sun and McDonough, 1989) then a Re concentra-

tion = 0.12 ppb is obtained for the DMM. This is

Fig. 7. Diagram of ln(Cu/Re) versus ln(Re) for MORB and BABB

analyzed using laser ablation ICP-MS. Samples from the Lau

Spreading Centers and the Woodlark Basin as well as D-MORB are

distinctively separated from MORB and the King’s Triple Junction

samples with higher Cu/Re and flatter slopes. The negative slope

indicates Re is more incompatible than Cu.

W. Sun et al. / Chemical Geology 196 (2003) 259–281276

similar to the low end of previous estimates calculated

on the basis of 187Os/188Os compositions of modern

abyssal peridotites and an assuming mean age of the

DMM of 1.8 Ga (Re = 0.122 to 0.177 ppb; Hauri and

Hart, 1997). This estimate is significantly lower than

estimates of primitive mantle Re concentrations (i.e.

Re = 0.28 ppb; McDonough and Sun, 1995, Re = 0.25

ppb; Morgan, 1986, Re = 0.19 ppb; Meisel et al.,

2001). The low and constant Yb/Re of MORB is

significant for understanding mantle processes.

The estimated Re abundance of the continental

crust is f 0.2 to 0.4 ppb (Esser and Turekian, 1993;

Peucker-Ehrenbrink and Jahn, 2001; Saal et al.,

1998). Assuming the Yb concentration of the con-

tinental crust is 2 ppm (Rudnick and Fountain,

1995), then the Yb/Re value of the continental crust

is about 5 to 10 (ppm/ppb). This is even higher than

that of MORB and the depleted mantle. If this

estimated Re abundance in the DMM is correct, then

either there is a substantial reservoir with lower Yb/

Re, perhaps in the deep mantle, that has not been

accounted for (Hauri and Hart, 1997; Martin et al.,

1991), or the Re abundance in the continental crust

has been significantly underestimated, or a combina-

tion of both.

5.4. Molybdenum concentration in the depleted

mantle

Molybdenum is a moderately chalcophile element

(McDonough and Sun, 1995), however, it is similarly

incompatible as the lithophile element Ce such that

there are near constant Ce/Mo and Pr/Mo in modern

oceanic basalts (Hofmann et al., 1986; Newsom et al.,

1986) and various crustal rocks of Archean and post-

Archean ages (Sims et al., 1990). The Mo/Ce of the

silicate Earth is estimated to be f 0.03 (McDonough

and Sun, 1995). The new results confirm the similar

chemical behavior of Mo and Ce, except in samples

from more depleted sources (without residual sulfide).

On the basis of our LA ICP-MS data, we revise the

average Mo/Ce for MORB and the DMM to be

0.034F 0.001. Assuming that Ce is about 40%

depleted in the DMM relative to the primitive mantle,

and using a Ce abundance of 1675 ppb and Mo/Ce of

0.034 for the primitive mantle (McDonough and Sun,

1995), a Mo abundance of 34 ppb is obtained for the

DMM.

6. Conclusions

New LA ICP-MS analyses of 30 MORB glasses

and 37 back-arc basin basalt glasses provide an

enhanced understanding of the behavior of Re and

the moderately chalcophile elements Mo and Cu

during mantle melting. The high Re concentrations

and the positive linear correlations between Re and

Yb, for the LSC, the KTJ and MORB glasses indicate

that the potential loss of volatile Re after eruption has

been limited by the high pressure of sea water. There-

fore, submarine volcanic glasses provide more reliable

estimates of Re concentrations as compared to sub-

aerial erupted basalts. Based on the analyses here we

propose an average Re for back-arc basin basalts of

0.92F 0.09 ppb. This concentration is the same,

within errors, as the MORB average. The observed

correlations also exclude any obvious addition of Re

from subduction derived components despite demon-

strations of high Re losses from slabs (Becker, 2000).

Therefore, Re might have been lost at the early stage

of subduction and then transferred to the arc and/or

forearc, rather than the back-arc environment.

The mantle sources of the more highly depleted

samples including some MORBs (D-MORB) and

samples from Lau Spreading Center and the Woodlark

Basin are more incompatible element depleted than

that of E- and N-MORB. More extensive melting of

MORB sources has resulted in the formation of these

more depleted sources that have no residual sulfide,

thus resulting in a steeper slope for Re versus Yb

correlations and negative correlations between ln(Yb/

Re) and ln(Re), and ln(Ce/Mo) and ln(Mo) as well as

shallower slope in ln(Cu/Re) versus ln(Re) in derived

magmas.

Based on the similarity between Yb and Re, it is

proposed that the average Yb/Re value for the

depleted mantle (DMM) is 3.6F 0.1 ppm/ppb and

the average Re concentration of the present-day DMM

is estimated to be 0.12 ppb. This is at the lower end of

the range of previous estimates based on 187Os/188Os

compositions of abyssal peridotites and requires a

significant sink for Re. Similarly, the Mo concentra-

tion of the DMM is estimated to be 34 ppb.

The elemental systematics observed here allow a

better estimate of the relative incompatibilities of a

range of moderately incompatible and variously lith-

ophile and chalcophile elements in MORB and BABB

W. Sun et al. / Chemical Geology 196 (2003) 259–281 277

sources. Partition coefficients are in the order of

Mo =Ce <Yb =Re <Cu for E- and N-MORB (with

residual sulfide in the source) and Mo < Ce < R-

e <Yb <Cu for D-MORB and Lau Spreading Centers

and Woodlark (no residual sulfide in the source).

Acknowledgements

S.-s. Sun is thanked for many constructive com-

ments and suggestions. Thanks also to M. Honda and

I.S. Williams for constructive discussions. C. Allen

and J.M.G. Shelley assisted with ICP-MS trace

element analyses and N. Ware with EM analyses.

WS acknowledges the support of an International

Postgraduate Research Scholarship from the Austral-

ian National University. M. Perfit acknowledges

research and sample recovery support from the

National Science Foundation (NSF grants OCE89-

18890, OCE 90-18820, OCE90-19154) and the

NOAA Vents Program (50-ABNR-7-00131). This

manuscript benefited from the comments of W.

McDonough and an anonymous reviewer. [RR]

References

Aitken, B.G., Echeverria, L.M., 1984. Petrology and geochemistry

of komatiites and tholeiites from Gorgona Island, Colombia.

Contrib. Mineral. Petrol. 86, 94–105.

Alves, S., Schiano, P., Allegre, C.J., 1999. Rhenium–osmium iso-

topic investigation of Java subduction zone lavas. Earth Planet.

Sci. Lett. 168 (1–2), 65–77.

Alves, S., Schiano, P., Capmas, F., Allegre, C.J., 2002. Osmium

isotope binary mixing arrays in arc volcanism. Earth Planet. Sci.

Lett. 198, 355–369.

Arndt, N.T., 1986. Differentiation of komatiite flows. J. Petrol. 27

(2), 279–301.

Arndt, N.T., Nesbitt, R.W., 1984. Magma mixing in komatiitic lavas

from Munro Township, Ontario. In: Kroener, A., Hanson, G.N.,

Goodwin, A.M. (Eds.), Archaean Geochemistry; the Origin and

Evolution of the Archaean Continental Crust. Springer-Verlag,

Berlin, Federal Republic of Germany, pp. 99–114.

Arndt, N.T., Kerr, A.C., Tarney, J., 1997. Dynamic melting in

plume heads; the formation of Gorgona komatiites and basalts.

Earth Planet. Sci. Lett. 146 (1–2), 289–301.

Bach, W., Niedermann, S., 1998. Atmospheric noble gases in

volcanic glasses from the southern Lau Basin; origin from

the subducting slab? Earth Planet. Sci. Lett. 160 (3 – 4),

297–309.

Baker, P.E., Condliffe, E., 1996. Compositional variations in sub-

marine volcanic ashes from the vicinity of the Vanuatu Island

Arc; a response to ridge–arc collision? J. Volcanol. Geotherm.

Res. 72 (3–4), 225–238.

Becker, H., 2000. Re–Os fractionation in eclogites and blueschists

and the implications for recycling of oceanic crust into the man-

tle. Earth Planet. Sci. Lett. 177 (3–4), 287–300.

Becker, H., Jochum, K.P., Carlson, R.W., 2000. Trace element

fractionation during dehydration of eclogites from high-pressure

terranes and the implications for element fluxes in subduction

zones. Chem. Geol. 163 (1–4), 65–99.

Bennett, V.C., Norman, M.D., Garcia, M.O., 2000. Rhenium and

platinum group element abundances correlated with mantle

source components in Hawaiian picrites; sulphides in the plume.

Earth Planet. Sci. Lett. 183 (3–4), 513–526.

Bernard, A., Symonds, R.B., Rose Jr., W.I., 1990. Volatile transport

and deposition of Mo, W and Re in high temperature magmatic

fluids. Appl. Geochem. 5 (3), 317–326.

Bevis, M., et al., 1995. Geodetic observations of very rapid con-

vergence and back-arc extension at the Tonga Arc. Nature

(Lond.) 374 (6519), 249–251.

Carlson, R., Macdougall, J.D., Lugmair, G.W., 1978. Differential

Sm/Nd evolution in oceanic basalts. Geophys. Res. Lett. 5 (4),

229–232.

Chadwick, D.J., Perfit, M.R., Embley, R.W., Chadwick, W.W., Rid-

ley, W.I., 1999. The magmatic and tectonic evolution of Axial

Seamount and associated rift zones: Juan de Fuca Ridge. Trans.-

Am. Geophys. Union, EOS 80 (46), F1085.

Dril, S.I., Kuzmin, M.I., Tsipukova, S.S., Zonenshain, L.P., 1997.

Geochemistry of basalts from the western Woodlark, Lau and

Manus basins; implications for their petrogenesis and source

rock compositions. Mar. Geol. 142 (1–4), 57–83.

Echeverria, L.M., 1980. Tertiary or Mesozoic komatiites from Gor-

gona Island, Colombia; field relations and geochemistry. Con-

trib. Mineral. Petrol. 73 (3), 253–266.

Eggins, S.M., Shelley, M., 2002. Nature and extent of composi-

tional heterogeneity in NIST610-617 serires glasses. Geostand.

Newsl., 98–99 26 (3), 1–18.

Embley, R.W., Chadwick, W., Perfit, M.R., Baker, E.T., 1991.

Geology of the northern Cleft Segment, Juan de Fuca Ridge;

recent lava flows, sea-floor spreading, and the formation of

megaplumes. Geology (Boulder) 19, 769–775.

Esser, B.K., Turekian, K.K., 1993. The osmium isotopic composi-

tion of the continental crust. Geochim. Cosmochim. Acta 57

(13), 3093–3104.

Falloon, T.J., Malahoff, A., Zonenshain, L.P., Bogdanov, Y., 1992.

Petrology and geochemistry of back-arc basin basalts from Lau

Basin spreading ridges at 15, 18 and 19S. Mineral. Petrol. 47 (1),

1–35.

Falloon, T.J., Green, D.H., Jacques, A.L., Hawkins, J.W., 1999.

Refractory magmas in back-arc basin settings; experimental

constraints on the petrogenesis of a Lau Basin example. J. Pet-

rol. 40 (2), 255–277.

Fischer, K.M., Wiens, D.A., 1996. The depth distribution of mantle

anisotropy beneath the Tonga subduction zone. Earth Planet.

Sci. Lett. 142 (1–2), 253–260.

Gasparon, M., Hilton, D.R., Varne, R., 1994. Crustal contamination

processes traced by helium isotopes; examples from the Sunda

Arc, Indonesia. Earth Planet. Sci. Lett. 126 (1–3), 15–22.

W. Sun et al. / Chemical Geology 196 (2003) 259–281278

Gill, J.B., 1976. Composition and age of Lau Basin and ridge

volcanic rocks; implications for evolution of an interarc basin

and remnant arc. Geol. Soc. Amer. Bull. 87 (10), 1384–1395.

Hauri, E.H., Hart, S.R., 1997. Rhenium abundances and systematics

in oceanic basalts. Chem. Geol. 139 (1–4), 185–205.

Hawkins Jr., J.W., 1976. Petrology and geochemistry of basaltic

rocks of the Lau Basin. Earth Planet. Sci. Lett. 28 (3), 283–297.

Hawkins, J.W., 1994. Petrologic synthesis; Lau Basin Transect (Leg

135). In: Hawkins, J.W., et al. (Eds.), Proceedings of the Ocean

Drilling Program, Scientific Results, Lau Basin; Covering Leg

135 of the Cruises of the Drilling Vessel JOIDES Resolution,

Suva Harbor, Fiji to Honolulu, Hawaii, Sites 834–841, 17 De-

cember 1990–28 February 1991. Proceedings of the Ocean Drill-

ing Program, Scientific Results. OceanDrilling Program, TexasA

& M University, College Station, TX, USA, pp. 879–905.

Hawkins, J.W., 1995. Evolution of the Lau Basin; insights from

ODP Leg 135. In: Taylor, B., Natland, J. (Eds.), Active Margins

and Marginal Basins of the Western Pacific. Geophysical Mono-

graph. American Geophysical Union, Washington, DC, United

States, pp. 125–173.

Hawkins, J.W., Melchior, J.T., 1985. Petrology of Mariana Trough

and Lau Basin basalts. JGR. J. Geophys. Res., B 90 (13),

11431–11468.

Haymon, R.M., et al., 1993. Volcanic eruption of the mid-ocean

ridge along the East Pacific Rise crest at 9 degrees 45–52VN;direct submersible observations of seafloor phenomena associ-

ated with an eruption event in April 1991. Earth Planet. Sci.

Lett. 119 (1–2), 85–101.

Helz, R.T., 1977. Determination of the P–T dependence of the first

appearance of FeS-rich liquid in natural basalts to 20 kb. Eos,

Trans.-Am. Geophys. Union 58 (6), 523.

Hilton, D.R., Hoogewerff, J.A., Van, B.M.J., Hammerschmidt, K.,

1992. Mapping magma sources in the East Sunda–Banda arcs,

Indonesia; constraints from helium isotopes. Geochim. Cosmo-

chim. Acta 56 (2), 851–859.

Hilton, D.R., Hammerschmidt, K., Loock, G., Friedrichsen, H.,

1993. Helium and argon isotope systematics of the central

Lau Basin and Valu Fa Ridge; evidence of crust/mantle inter-

actions in a back-arc basin. Geochim. Cosmochim. Acta 57 (12),

2819–2841.

Hofmann, A.W., 1988. Chemical differentiation of the Earth: the

relationship between mantle, continental crust, and oceanic

crust. Earth Planet. Sci. Lett. 90, 297–314.

Hofmann, A.W., 1997. Mantle geochemistry; the message from

oceanic volcanism. Nature (Lond.) 385 (6613), 219–229.

Hofmann, A.W., White, W.M., 1983. Ba, Rb and Cs in the Earth’s

mantle. Z. Naturforsch. 38, 256–266.

Hofmann, A.W., Jochum, K.P., Seufert, M., White, W.M., 1986. Nb

and Pb in oceanic basalts; new constraints on mantle evolution.

Earth Planet. Sci. Lett. 79 (1–2), 33–45.

Honda, M., Patterson, D.B., McDougall, I., Falloon, T.J., 1993.

Noble gases in submarine pillow basalt glasses from the Lau

Basin; detection of a solar component in backarc basin basalts.

Earth Planet. Sci. Lett. 120 (3–4), 135–148.

Johnson, M.C., Plank, T., 1999. Dehydration and melting experi-

ments constrain the fate of subducted sediments. Geochem.

Geophys. Geosystem-G 3 (1999GC000014).

Kerr, A.C., Marriner, G.F., Arndt, N.T., Tarney, J., Nivia, A.,

Saunders, A.D., Duncan, R.A., 1996. The petrogenesis of Gor-

gona komatiites, picrites and basalts: new field, petrographic

and geochemical constraints. Lithos 37 (2–3), 245–260.

Langmuir, C.H., Bender, J.F., Bence, A.E., Hanson, G.N., 1977.

Petrogenesis of basalts from the FAMOUS area; Mid-Atlantic

Ridge. Earth Planet. Sci. Lett. 36 (1), 133–156.

Longerich, H.P., Jackson, S.E., Gunther, D., 1996. Laser ablation-

inductively coupled plasma-mass spectrometric transient signal

data acquisition and analyte concentration calculation. J. Anal.

At. Spectrom. 11, 899–904.

Lundstrom, C.C., Sampson, D.E., Perfit, M.R., Gill, J., Williams,

Q., 1999. Insights into MORB petrogenesis: U-series disequi-

libria from the Siqueiros Transform and Lamont Seamounts.

J. Geophys. Res. 104, 13035–13048.

Martin, C.E., Esser, B.K., Turekian, K.K., 1991. Re–Os isotopic

constraints on the formation of mantle and crustal reservoirs.

Aust. J. Earth Sci. 38 (5), 569–576.

Mathez, E.A., 1976. Sulfur solubility and magmatic sulfides in

submarine basalt glass. J. Geophys. Res. 81, 4269–4276.

McCulloch, M.T., Gamble, A.J., 1991. Geochemical and geody-

namical constraints on subduction zone magmatism. Earth

Planet. Sci. Lett. 102 (3–4), 358–374.

McDonough, W.F., Sun, S.S., 1995. The composition of the Earth.

120 (3–4), 223–253.

McGoldrick, P.J., Keays, R.R., Scott, B.B., 1979. Thallium; a sen-

sitive indicator of rock/seawater interaction and of sulfur satu-

ration of silicate melts. Geochim. Cosmochim. Acta 43 (8),

1303–1312.

McInnes, B.I.A., McBride, J.S., Evans, N.J., Lambert, D.D., An-

drew, A.S., 1999. Osmium isotope constraints on ore metal

recycling in subduction zones. Science 286 (5439), 512–516.

Meisel, T., Walker, R.J., Irving, A.J., Lorand, J.P., 2001. Osmium

isotopic compositions of mantle xenoliths; a global perspective.

Geochim. Cosmochim. Acta 65 (8), 1311–1323.

Minster, J.F., Allegre, C.J., 1978. Systematic use of trace elements in

igneous processes: Part III. Inverse problem of batch partial melt-

ing in volcanic suites. Contrib. Mineral. Petrol. 68 (1), 37–52.

Mitchell, R.H., Keays, R.R., 1981. Abundance and distribution of

gold, palladium and iridium in some spinel and garnet lherzo-

lites; implications for the nature and origin of precious metal-

rich intergranular components in the upper mantle. Geochim.

Cosmochim. Acta 45 (12), 2425–2442.

Morgan, J.W., 1986. Ultramafic xenoliths: clues to Earth’s late

accretionary history. J. Geophys. Res. 91 (B12), 12375–12387.

Newsom, H.E., White, W.M., Jochum, K.P., Hofmann, A.W., 1986.

Siderophile and chalcophile element abundances in oceanic ba-

salts, Pb isotope evolution and growth of the Earth’s core. Earth

Planet. Sci. Lett. 80, 299–313.

Niu, Y., Batiza, R., 1997. Trace element evidence from seamounts

for recycled oceanic crust in the eastern Pacific mantle. Earth

Planet. Sci. Lett. 148 (3–4), 471–483.

Norman, M.D., 1998. Melting and metasomatism in the continental

lithosphere; laser ablation ICPMS analysis of minerals in spinel

lherzolites from eastern Australia. Contrib. Mineral. Petrol. 130

(3–4), 240–255.

O’Neill, H.S.C., Eggins, S.M., 2002. The effect of melt composi-

W. Sun et al. / Chemical Geology 196 (2003) 259–281 279

tion on trace element partitioning: an experimental investigation

of the activity coefficients of FeO, NiO, CoO, MoO2, and MoO3

in silicate melts. Chem. Geol. 186 (1–2), 151–181.

Parkinson, I.J., Arculus, R.J., 1999. The redox state of subduction

zones; insights from arc-peridotites. Chem. Geol. 160 (4),

409–423.

Pearce, N.J.G., Perkins, W.T., Westgate, J.A., Gorton, M.P., Jack-

son, S.E., Neal, C.R., Chenery, S.P., 1997. A compilation of new

and published major and trace element data for NIST SRM 610

and NIST SRM 612 glass reference materials. Geostand. Newsl.

21, 115–144.

Pelletier, B., Calmant, S., Pillet, R., 1998. Current tectonics of the

Tonga–New Hebrides region. Earth Planet. Sci. Lett. 164 (1–2),

263–276.

Perfit, M.R., Fornari, D.J., Malahoff, A., Embley, R.W., 1983. Geo-

chemical studies of abyssal lavas recovered by DSRV ALVIN

from the eastern Galapagos Rift– Inca Transform–Ecuador Rift:

III. Geophys. Res. (88), 10551–10572.

Perfit, M.R., Langmuir, C.H., Baekisapa, M., Chappell, B.W.,

Johnson, R.W., Staudigel, H., Taylor, S.R., 1987. Geochemistry

and petrology of volcanic rocks from the Woodlark Basin;

addressing questions of ridge subduction. In: Taylor, B., Exon,

N.F. (Eds.), Marine Geology, Geophysics and Geochemistry of

the Woodlark Basin–Solomon Islands. Circum-Pacific Council

for Energy and Mineral Resources, Earth Science Series, vol. 7,

pp. 113–154.

Perfit, M.R., Fornari, D.J., Smith, M.C., Bender, J.F., Langmuir,

C.H., Haymon, R.M., 1994. Small-scale spatial and temporal

variations in mid-ocean ridge crest magmatic processes. Geol-

ogy 22, 375–379.

Petterson, M.G., Babbs, T., Neal, C.R., Mahoney, J.J., Saunders,

A.D., Duncan, R.A., Tolia, D., Magu, R., Qopoto, C., Mahoa,

H., Natogga, D., 1999. Geological-tectonic framework of So-

lomon Islands, SW Pacific; crustal accretion and growth with-

in an intra-oceanic setting. Tectonophysics 301 (1–2), 35–60.

Peucker-Ehrenbrink, B., Jahn, B.M., 2001. Rhenium–osmium iso-

tope systematics and platinum group element concentrations;

loess and the upper continental crust. Geochem. Geophys. Geo-

systems-G 3 (2001GC000172).

Plank, T., Langmuir, C.H., 1998. The chemical composition of

subducting sediment and its consequences for the crust and

mantle. Chem. Geol. 145 (3–4), 325–394.

Poreda, R., 1985. Helium-3 and deuterium in back-arc basalts; Lau

Basin and the Mariana Trough. Earth Planet. Sci. Lett. 73 (2–4),

244–254.

Reisberg, L., Lorand, J.P., 1995. Longevity of sub-continental man-

tle lithosphere from osmium isotope systematics in orogenic

peridotite massifs. Nature (Lond.) 376 (6536), 159–162.

Reisberg, L.C., Allegre, C.J., Luck, J.M., 1991. The Re–Os sys-

tematics of the Ronda ultramafic complex of southern Spain.

Earth Planet. Sci. Lett. 105 (1–3), 196–213.

Reisberg, L., et al., 1993. Os isotope systematics in ocean island

basalts. Earth Planet. Sci. Lett. 120 (3–4), 149–167.

Righter, K., 1999. Experimental constraints on the behavior of

rhenium and osmium during mantle melting and magmatic dif-

ferentiation. Abstract Goldschmidt Conference.

Righter, K., Hauri, E.H., 1998. Compatibility of rhenium in garnet

during mantle melting and magma genesis. Science 280 (5370),

1737–1741.

Rubin, K.H., Smith, M.C., Bergmanis, E.C., Perfit, M.R., Sinton,

J.M., Batiza, R., 2001. Geochemical heterogeneity within mid-

ocean ridge lava flows; insights into eruption, emplacement

and global variations in magma generation. Earth Planet. Sci.

Lett. 188, 349–367.

Rudnick, R.L., Fountain, D.M., 1995. Nature and composition of

the continental crust; a lower crustal perspective. Rev. Geophys.

33 (3), 267–309.

Saal, A.E., Rudnick, R.L., Ravizza, G.E., Hart, S.R., 1998. Re–Os

isotope evidence for the composition, formation and age of the

lower continental crust. Nature (Lond.) 393 (6680), 58–61.

Sano, Y., Nakamura, Y., Wakita, H., 1986. Light noble gases in

basalt glasses from Mariana Trough. Geochim. Cosmochim.

Acta 50 (11), 2429–2432.

Schaefer, B.F., Parkinson, I.J., Hawkesworth, C.J., 2000. Deep

mantle plume osmium isotope signature from West Greenland

Tertiary picrites. Earth Planet. Sci. Lett. 175 (1–2), 105–118.

Schiano, P., Birck, J.L., Allegre, C.J., 1997. Osmium–strontium–

neodymium–lead isotopic covariations in mid-ocean ridge ba-

salt glasses and the heterogeneity of the upper mantle. Earth

Planet. Sci. Lett. 150 (3–4), 363–379.

Shirey, S.B., Walker, R.J., 1995. Carius tube digestion for low-

blank rhenium–osmium analysis. Anal. Chem. 34, 2136–2141.

Sims, K.W.W., Newsom, H.E., Gladney, E.S., 1990. Chemical frac-

tionation during formation of the Earth’s core and continental

crust: clues from As, Sb, W, and Mo. In: Newsom, H.E., Jones,

J.H. (Eds.), Origin of the Earth. Oxford Univ. Press, New York,

NY, pp. 291–317.

Smith, M.C., Perfit, M.R., Jonasson, I.R., 1994. Spatial and tem-

poral variations in the geochemistry of lavas from the S. Juan de

Fuca Ridge: implications for petrogenesis. J. Geophys. Res. 99,

4787–4812.

Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic system-

atics of oceanic basalts; implications for mantle composition and

processes. In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in

the Ocean Basins. Geological Society Special Publications.

Geological Society of London, London, United Kingdom, pp.

313–345.

Sylvester, P.J., Eggins, S.M., 1997. Analysis of Re, Au, Pd, Pt and

Rh in NIST glass certified reference materials and natural basalt

glasses by laser ablation ICP-MS. Geostand. Newsl. 21 (2),

215–229.

Taran, Y.A., Hedenquist, J.W., Korzhinsky, M.A., Tkachenko, S.I.,

Shmulovich, K.I., 1995. Geochemistry of magmatic gases from

Kudravy volcano, Iturup, Kuril Islands. Geochim. Cosmochim.

Acta 59 (9), 1749–1761.

Taylor, B., 1995. Backarc Basins, Tectonics and Magmatism. Ple-

num, New York. 524 pp.

Taylor, B., Zellmer, K., Martinez, F., Goodliffe, A.M., 1996. Sea-

floor spreading in the Lau back-arc basin. Earth Planet. Sci. Lett.

144 (1–2), 35–40.

Trull, T.W., Perfit, M.R., Kurz, M.D., 1990. He and Sr isotopic

constraints on subduction contributions to Woodlark Basin vol-

canism, Solomon Islands. Geochim. Cosmochim. Acta 54 (2),

441–453.

W. Sun et al. / Chemical Geology 196 (2003) 259–281280

Walker, R.J., Shirey, S.B., Hanson, G.N., Rajamani, V., Horan,

M.F., 1989. Re–Os, Rb–Sr and O isotopic systematics of the

Archean Lolar Schist belt, Karnataka, India. Geochim. Cosmo-

chim. Acta 53, 3005–3013.

Walker, R.J., Storey, M., Kerr, A.C., Tarney, J., Arndt, N.T., 1999.

Implications of (super 187) Os isotopic heterogeneities in a

mantle plume; evidence from Gorgona Island and Curacao.

Geochim. Cosmochim. Acta 63 (5), 713–728.

Wendlandt, R.F., 1982. Sulfide saturation of basalt and andesite

melts at high pressures and temperatures. Am. Mineral. 67

(9–10), 877–885.

Woodland, S.J., Pearson, D.G., Thirlwall, M.F., 2002. A platinum

group element and Re–Os isotope investigation of siderophile

element recycling in subduction zones: comparision of Grena-

da, Lesser Antilles Arc and the Izu–Bonin Arc. J. Petrol. 42,

171–198.

Xie, Q., Kerrich, R., Fan, J., 1993. HFSE/REE fractionations re-

corded in three komatiite –basalt sequences, Archean Abitibi

greenstone belt; implications for multiple plume sources and

depths. Geochim. Cosmochim. Acta 57 (16), 4111–4118.

Yi, W., Halliday, A.N., Alt, J.C., Lee, der C., Rehkamper, M.,

Garcia, M.O., Su, Y., 2000. Cadmium, indium, tin, tellurium,

and sulfur in oceanic basalts; implications for chalcophile ele-

ment fractionation in the Earth. J. Geophys. Res., B. Solid Earth

Planets 105 (8), 18927–18948.

W. Sun et al. / Chemical Geology 196 (2003) 259–281 281