Sodic pyroxene and sodic amphibole as potential micro-analytical reference material for Li isotopes

A secondary ion mass spectrometry (SIMS) re-evaluationof B and Li isotopic compositions of Cu-bearing elbaite fromthree global localities

T. LUDWIG1,*, H. R. MARSCHALL

2,3, P. A. E. POGGE VON STRANDMANN2, B. M. SHABAGA

4, M. FAYEK4

AND

F. C. HAWTHORNE4

1 Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234�36, 69120 Heidelberg, Germany2 Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK3 Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole,

Massachusetts 02543, USA4 Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada

[Received 18 March 2011; Accepted 13 June 2011]

ABSTRACT

Cu-bearing elbaite from Paraıba (Brazil) is a highly-prized gem tourmaline. Specimens of similarquality from localities in Mozambique and Nigeria are being sold, and reliable provenance tools arerequired to distinguish specimens from the original locality from ‘Paraıba-type’ tourmaline from Africa.Here we present Li and B isotope analyses of Cu-bearing elbaite from all three localities anddemonstrate the suitability of these isotope systems as a provenance tool. Isotopic profiles acrosschemically zoned grains revealed homogenous B and Li isotopic compositions, demonstrating a strongadvantage of their application as a provenance tool as opposed to major, minor or trace elementsignatures.

Li and B isotopes of all investigated samples of Cu-bearing elbaites from the three localities arewithin the range of previously published granitic and pegmatitic tourmaline. Anomalous isotopecompositions published previously for these samples are corrected by our results.

KEYWORDS: tourmaline, isotopes, Paraıba, lithium, boron, secondary ion mass spectrometry (SIMS), ion

probe, LA-ICP-MS

Introduction

TOURMALINE close to the elbaite endmember

composition typically occurs in pegmatite dykes

as comb-like layers or in miarolitic cavities and

veins. The rarest and most expensive varieties of

elbaite were discovered in the late 1980s in the

Batalha pegmatite mine of the Borborema

Province in the state of Paraıba, northeastern

Brazil. These elbaites display very impressive

colours of blue, blue-green, green and pink, with

Cu2+ and Mn3+ as chromophores (Rossman et al.,

1991). ‘Paraıba-type’ tourmaline is produced

today from three different pegmatite districts in

Brazil, Mozambique and Nigeria. Prices for gem

tourmaline vary by several orders of magnitude

depending not only on the quality, colour and

clarity, but also on the provenance, and gemmol-

ogists are challenged to develop effective

provenance tools. Elbaite major- and minor-

element compositions are variable, overlap

between the three localities and provide no

definite provenance criteria. Trace element

abundances (e.g. Ga, Bi, Pb) have been used

successfully to distinguish ‘Paraıba-type’ tourma-

line from Brazil and Nigeria, but the grains show* E-mail: [email protected]: 10.1180/minmag.2011.075.4.2485

Mineralogical Magazine, August 2011, Vol. 75(4), pp. 2485–2494

# 2011 The Mineralogical Society

significant zoning and some overlap between

localities (Rossman, 2009; Peretti et al., 2010).

Further provenance tools are required to

distinguish between the three localities. Shabaga

et al. (2010) studied elbaite samples from all three

localities using secondary ion mass spectrometry

(SIMS) to analyse B and Li isotopes. They

suggested using these isotope systems as prove-

nance indicators for ‘Paraıba-type’ tourmaline, as

the isotopic signatures they found were different

for the three localities. SIMS requires a minimum

of sample material with sputtered craters signifi-

cantly <1 mm deep and 5�10 mm in diameter and

therefore the requirement for an almost non-

destructive method, which is critical in

gemmology, is fulfilled by this technique.

Shabaga et al. (2010) reported d11B values

ranging from an extremely low �42.4% to

�19.1% and very high d7Li values in the range

from +24.5% to +46.8%. They identified their

d11B values as among the lowest values reported

for magmatic systems and compared them to

those of tourmalines from the Lavicky leuco-

granite published by Jiang et al. (2003), although

the latter (down to �37.3%) were corrected in a

comment by Marschall and Ludwig (2006) and a

reply by Jiang (2006). In their work, Shabaga et

al. (2010) state that ‘‘the values reported by Jiang

et al. (2003) may be correct’’ and speculate that

‘‘Marschall and Ludwig (2006) may have used

low mass-resolution during their SIMS analysis’’,

which ‘‘would produce elevated 11B counts and

result in higher d11B values’’.In this study we present more accurate and

precise d7Li and d11B SIMS data for the same

elbaites previously examined by Shabaga et al.

(2010) and we provide an estimate of the

deviation that may occur in d11B SIMS analyses

of tourmaline if typical molecular interferences

like 9BeH or 10BH are not resolved.

In addition to the samples analysed by Shabaga

et al. (2010), we also analysed traverses over

chemically zoned grains of Cu-bearing elbaite

from Paraıba, and demonstrate that grains with

pronounced chemical zonation show no variation

in B isotope ratios and (with one minor exception)

in Li isotopes.

Analytical procedure

Li and B isotopes are reported in delta notation. Li

isotopes are reported relative to NIST RM 8545

(LSVEC, Flesch et al., 1973). B isotopes are

reported relative to NIST SRM 951 (Catanzaro et

al., 1970).

Reference materialsFor the calibration of the SIMS d11B analyses,

three tourmalines were used as reference material:

elbaite #98144, dravite #108796 and schorl

#112566 (Dyar et al., 2001). Their d11B values

(see Table 1) were determined by Leeman and

TABLE 1. Compilation of SIMS calibration data. The samples Brazil 1�4, Mozambique 1�2 and Nigeria 1�2were analysed in October 2010 and the samples Brazil 5�6 in December 2010. Note that the d values arethe known values of the reference samples and ainst is the result of the SIMS calibrations; ainst issubsequently used to correct the measured isotope ratios of the unknown samples.

Reference ————— Li ————— ————— B —————Session sample N d7Li (%) ainst (1s) N d11B (%) ainst (1s)

Oct 2010 Elbaite #98144 5 +7.5 1.0146 (0.0008) 5 �10.4 0.9563 (0.0005)Dravite #108796 5 �6.6 0.9567 (0.0004)Schorl #112566 5 �12.5 0.9580 (0.0002)

Mean: 0.9570 (0.0009)

Dec 2010 Elbaite #98144 10 +7.5 1.0137 (0.0006) 5 �10.4 0.9551 (0.0003)Dravite #108796 5 �6.6 0.9557 (0.0003)Schorl #112566 6 �12.5 0.9572 (0.0002)

Mean: 0.9560 (0.0011)

N: number of analyses; ainst: instrumental mass fractionation; 1s: standard deviation of N analyses and of the threeainst values for B respectively

2486

T. LUDWIG ET AL.

Tonarini (2001) using positive thermal ion mass

spectrometry (P-TIMS).

The elbaite #98144 was used for the calibration

of d7Li SIMS analyses. Since no d7Li value had

been published for any of the three tourmalines, the

elbaite was analysed by multi-collector inductively

coupled plasma mass spectrometry (MC-ICP-MS)

at the University of Bristol. The sample was finely

powdered and dissolved in HF-HNO3-HClO4,

followed by HNO3 and then by HCl. The dissolved

sample was passed through two high aspect ratio

cation exchange columns (AG50W X12), using

dilute HCl as an eluant, based on the approach of

James and Palmer (2000), and described in

Marschall et al. (2007). Purified samples were

measured with a Thermo Finnigan Neptune MC-

ICP-MS, relative to the NIST LSVEC standard, as

described in Jeffcoate et al. (2004). Sample

analyses were repeated two to three times during

the run. Internal precision was typically

0.1�0.2%. Based on the analysis of international

silicate rock standards over a period of four years,

the long-term external reproducibility is S0.3%(BHVO-2: d7Li = 4.7S0.2% (N = 31); BCR-2:

d7Li = 2.6S0.3% (N = 18)). Two grains of elbaite

#98144 were analysed: grain 1 yielded d7Li =

+7.2S0.1%, grain 2 d7Li = +7.7S0.2% and we

used the mean value of 7.5% (all uncertainties

reported in this paragraph are 2s).

The NIST SRM610 glass, which was used as a

reference material by Shabaga et al. (2010), is not

a suitable reference material for SIMS analysis of

Li and B isotopes in elbaite. Compared to elbaite,

the B concentration (~350 mg/g) is lower by a

factor of ~100 and the Li concentration

(~480 mg/g) by a factor of ~25. Either the

secondary ion intensities would be very low

during calibration with the SRM610 (resulting in

poor precision) or the intensities of the more

abundant isotope would be very high (>106 ions/s)

during analysis of the tourmalines. In the latter

case, accuracy could be seriously affected by the

deadtime of the detector system and its subse-

quent correction. Furthermore, SRM610 was

shown to be affected by SIMS matrix effects for

Li isotopes (Kasemann et al., 2005) and B

isotopes (Rosner et al., 2008) compared to other

glasses with Li and B as trace elements.

Analytical setupLi and B isotope ratios were determined by

SIMS using a modified Cameca ims 3f ion probe at

the Institute of Earth Sciences, Heidelberg

University. The common parameters for both Li

and B isotope analyses were: 1 nA, 14.5 keV 16O�

primary ion beam, diameter typically 5 mm; 4.5 kV

secondary acceleration voltage; 0S50 eV energy

window; secondary ion detection by a single

electron multiplier (Balzers SEV217) in counting

mode (deadtime t = 16 ns); n = 50 cycles per

analysis; each cycle was an A�B�A sequence (e.g.6Li�7Li�6Li) which minimizes the influence of

slow changes in secondary ion intensity on the

measured isotope ratio. The integration times per

cycle were 3.5 s for 6Li, 1 s for 7Li, 3.3 s for 10B

and 1.65 s for 11B. For Li isotopes, the mass

resolution m/Dm was set to 970 at 10% intensity

ratio (860 at 0.1%) and for B isotopes it was 1200

at 10% (1000 at 0.1%). Prior to each analysis, a

mass calibration of the magnet was performed. The

pre-sputtering time (which includes the time needed

for mass calibration) was 250�285 s. The typical

internal precision of both the Li and B isotope

analyses was 0.5% (1s).

The measured isotope ratios were corrected for

the instrumental mass fractionation ainst which

was determined using the reference materials (see

Table 1). Because Li is a major element in elbaite

(and a trace element in schorl or dravite), only

elbaite #98144 was used to determine ainst for Li

isotopes. For the correction of B isotope data the

mean ainst of the three reference tourmalines was

used. The standard deviation (0.9% (1s) for the

first analytical session and 1.1% (1s) for the

second) of the mean ainst indicates that no

significant matrix effect exists for B isotope

SIMS analyses of tourmalines. The accuracy of

the d11B values of tourmalines obtained by the ion

probe in Heidelberg has also been demonstrated

in Marschall et al. (2006, 2009) by comparison

with independent TIMS data. From these

comparisons the accuracy of our d11B values is

expected to be better than 2%. Up to now neither

additional d7Li reference materials (tourmalines

and in particular elbaites) nor independent d7Li

analyses of the same samples (elbaites) using

different methods exist; it is therefore impossible

to make a comparable statement about the

accuracy of the d7Li data. Using the ims3f in

Heidelberg and synthetic basaltic glasses as

reference material, Marks et al. (2008) reported

deviations of �6% for an amphibole (arfvedso-

nite) and �3.9% for a pyroxene (aegirine) for

their d7Li SIMS analyses. In the present work,

unlike that of Marks et al. (2008), the reference

material (elbaite) and the unknown samples (also

elbaites) are well matched, and the accuracy of

the d7Li data can be expected to be much better.

B AND LI ISOTOPIC COMPOSITIONS OF CU-BEARING ELBAITE

2487

Molecular interferencesThere are two significant molecular interfer-

ences that must be suppressed in B isotope

analyses: these are 9BeH for 10B and 10BH for11B. The mass spectra at masses of 10 u and 11 u,

shown in Fig. 1, were recorded on elbaite #98144.

At a mass resolution of m/Dm = 1200 at 10% the10B peak and the 9BeH peak overlap, but at the

centre of the 10B peak, the 9BeH peak is

suppressed by a factor of >1000: the mass

difference between 10B and 9BeH is ~0.007 u

and with m/Dm = 1000 at 0.1% the half width of

the 9BeH peak at 0.1% is 10.02/2000 &0.005 < 0.007 u. Furthermore, as Be is a trace

element in tourmaline (typically B/Be >1000), the9BeH interference shown in Fig. 1a has a very

low intensity compared to 10B; the 9BeH/10B ratio

is ~2610�5 = 0.02%. Therefore, even at

insufficient mass resolution, the 9BeH interfer-

ence is irrelevant. The more important inter-

ference in B isotope analysis of tourmaline is10BH as both B and H are major components of

tourmaline. Figure 1b shows a mass spectrum at

mass 11 u. Again, the 10BH interference is

suppressed by at least a factor of 1000; the10BH/11B ratio is 2.46102/2.26105 &1.1610�3. Therefore, in a worst case scenario

(10BH not suppressed at all during analysis of the

reference material and fully suppressed during

analysis of the unknown sample or vice versa), the

error would be only ~1%. The speculation by

Shabaga et al. (2010) that the B isotope data in

Marschall and Ludwig (2006) may be in error by

>+20% due to 10BH interference is therefore not

correct. We spare the reader the same lengthy

considerations about the molecular interferences

of the Li isotopes: at a mass resolution of m/

Dm = 860 at 0.1%, the interferences are suffi-

ciently suppressed.

Results

A total of 10 samples of Cu-bearing elbaite were

analysed. Six samples (Brazil 1�6) are elbaites

from the Batalha mine in Paraıba, Brazil, two

elbaites (Mozambique 1�2) are from the Mavuco

mine in the Alto Ligonha district, Mozambique,

and the remaining two (Nigeria 1�2) are from an

undetermined pegmatite mine in Nigeria. The

samples Brazil 1�4, Mozambique 1�2 and

Nigeria 1�2 are the same samples analysed by

Shabaga et al. (2010). Li and B isotopes were

analysed in separate sessions. Since we did not

perform two analyses on the same spot, no pairs of

d7Li and d11B values at exactly the same location

were obtained. Typically, the distance between the

d7Li spots and the d11B spots was 50 mm. In

Table 2 and Fig. 3, we therefore do not present

single d7Li�d11B value pairs, but the mean values

for each sample. A table with the complete dataset

FIG. 1. Mass spectra (recorded with a mass resolution of 1200 at 10% and with elbaite #98144 as the sample) at

masses 10 u and 11 u. Note that, although the peaks overlap, the contribution of the 9BeH peak to the centre of the10B peak is negligible (<10�5).

2488

T. LUDWIG ET AL.

has been lodged as an electronic supplement.

Compared to the present work, in Shabaga et al.

(2010) for the same samples; (1) the d7Li values

were higher, on average by +22%; (2) the

maximum spread of d7Li values for a single

provenance was much larger (13.7% vs 2.9%);

(3) the d11B values were lower, on average by

�20%; and (4) the maximum spread of d11B

values for a single provenance was greater (9.5%vs 4.3%). Figure 2a shows the mean values of all

samples in a d11B vs d7Li plot. Each provenance

occupies its own well defined region in this plot.

In Fig. 2b, the mean values of all analyses for

each provenance are plotted. In order to have a

quantitative measure for the dissimilarity of the

three provenances in d7Li and d11B, we calculated

their separation distance in the d7Li�d11B plane.

This is symbolized by lines in Fig. 2b and the

values of the three distances are given. Their

uncertainties (2s) were calculated from the 2sstandard deviations of the mean values by error

propagation. Each distance is larger than its 2s(even 3s) standard deviation and thus signifi-

cantly different from zero. Therefore, for this set

of samples, the three provenances are clearly

distinguishable. This does not hold true for all

differences if only one of the isotope systems is

used. For example, the d7Li difference between

Brazil and Mozambique is 1.5S2% (2s) and

therefore not large enough for an unambiguous

identification of the provenance.

The tourmaline samples Brazil 5 and 6 are mm-

sized fragments of multi-coloured, chemically

zoned Paraıba tourmalines. These tourmalines

show chemical zonation in Ca, Cu, F and most

prominently in Mn. We recorded d7Li and d11B

profiles through these fragments, electron-probe

microanalysis (EPMA) mappings of Mn and

semi-quantitative Mn SIMS profiles as indicators

of the chemical zonation. These profiles are

shown in Fig. 3. Neither the Li nor B isotopes

show significant correlation with the chemical

zonation, with one exception: the outer rim of

sample Brazil 5 shows a slight increase in d7Li by

+2% which correlates with an increase in Mn.

Discussion

The Li and B isotope data presented in this study

replace the erroneous data of Shabaga et al.

(2010). Those data were compromised by the lack

of suitable reference materials. The accurate

analyses presented here demonstrate that d11B

values for Cu-bearing elbaite from the three

localities are not exceptionally low. The lowest

of 62 analyses of Cu-bearing elbaite produced a

d11B of �17.6%. Similarly, the exceptionally

high d7Li values reported earlier are superseded.

No analysis exceeds a d7Li value of +15.0%.

We also reject the unsubstantiated re-establish-

ment by Shabaga et al. (2010) of the very low

d11B values from the Lavicky tourmaline, which

TABLE 2. Li and B isotopic composition of tourmalines from Brazil, Nigeria and Mozambique.

———— d7Li (%) ———— ———— d11B (%) ————Sample N Mean Min Max 1s Mean Min Max 1s

Brazil 1 3 +9.0 +8.6 +9.4 0.4 �15.9 �16.3 �15.6 0.3Brazil 2 3 +9.6 +9.1 +10.1 0.5 �15.3 �15.5 �15.1 0.2Brazil 3 3 +10.1 +10.0 +10.3 0.2 �15.3 �15.8 �15.0 0.4Brazil 4 3 +10.7 +10.1 +11.5 0.7 �12.7 �13.5 �11.9 0.8Brazil 5 21 +10.0 +8.2 +11.9 0.9 �16.9 �17.6 �16.1 0.5Brazil 6 17 +10.4 +9.5 +11.2 0.5 �15.5 �16.6 �14.9 0.5

Brazil 1�6 50 +10.1 +8.2 +11.9 0.8 �15.9 �17.6 �11.9 1.2

Mozambique 1 3 +12.1 +11.6 +12.5 0.4 �0.9 �1.2 �0.7 0.3Mozambique 2 3 +11.2 +10.9 +11.7 0.5 �1.5 �1.6 �1.4 0.1

Mozambique 1�2 6 +11.6 +10.9 +12.5 0.6 �1.2 �1.6 �0.7 0.4

Nigeria 1 3 +14.4 +13.9 +15.0 0.5 �9.2 �10.2 �8.0 1.2Nigeria 2 3 +13.6 +13.5 +13.7 0.1 �10.3 �10.5 �10.2 0.1

Nigeria 1�2 6 +14.0 +13.5 +15.0 0.6 �9.8 �10.5 �8.0 1.0

1s: standard deviation of N analyses. Values of all analyses for one provenance are listed in bold.

B AND LI ISOTOPIC COMPOSITIONS OF CU-BEARING ELBAITE

2489

clearly have been traced back to analytical errors

(Marschall and Ludwig, 2006; Jiang, 2006). The

accurate d11B value for Lavicky tourmaline is

�10.8S1.2% (Fig. 4; Marschall and Ludwig,

2006).

The corrected Li and B isotope data presented

in this study emphasize their suitability as a

provenance tool for ‘Paraıba-type’ tourmaline.

The three localities fall in distinct groups in the

d11B�d7Li plane, and the spread within indivi-

dual localities is very limited. The isotope profiles

across chemically zoned grains show no signifi-

cant variation in d11B, and no significant variation

in d7Li (except for one high-Mn rim). This lack of

intra-grain variability makes B and Li isotopes a

superior provenance tool compared to major-,

minor- or trace-element signatures.

The B isotope values for the three elbaite

localities presented in this study show no

exceptionally light B and do not suggest non-

marine evaporites in the source of the tourmaline-

hosting pegmatites (Fig. 4). The Nigerian samples

are within the range of most tourmalines from

granites, pegmatites and granite-related veins, and

the best estimate for the average continental crust

(Fig. 4). The Brazilian samples overlap the

typical range of granitic and pegmatitic tourma-

line, but they also extend to slightly lower d11B

values as low as �17.6%. In a recent study,

published as an extended abstract, Beurlen et al.

(2011) analysed dravites, elbaites and schorls

from 14 different samples from five different

pegmatite localities and one S-type granite from

the Borborema Pegmatite Province. This province

includes the Batalha mine in the state of Paraıba,

as well as a number of pegmatite dykes (some

mined for ‘Paraıba-type’ gem tourmaline) in the

adjacent state of Rio Grande do Norte. Most of

their samples range in d11B values from �18 to

�9%. Only two samples from further north in the

pegmatite province contain schorls and elbaites

from the wall zone of the pegmatite, which

showed some higher d11B values up to +2%. It

seems, therefore, that the B isotope range

observed for the Batalha mine in our study may

extend over the entire Borborema province, with

the exception of some schorl that crystallized in

the wall zones of some pegmatite dykes. Note that

Beurlen et al. (2011) also analysed tourmaline

from an S-type granite in the province, which they

interpret as the source of the pegmatite dykes, and

found d11B values between �15.1 and �13.3%.

Melting of terrigenous metasedimentary

sequences in the deep crust is consistent with

the observed B isotope signatures in both the

Nigerian and the Brazilian samples, and no

evidence for evaporites is detected. The samples

from the Alto Ligonha pegmatite district in

Mozambique show a B isotope signature that is

significantly heavier than typical granites and

FIG. 2. (a) Mean isotopic compositions of all samples. (b) Mean values of all analyses for one provenance. The

distances between the provenances are larger than their uncertainties (2s) and the provenances are therefore clearly

distinguishable. Error bars are 2s.

2490

T. LUDWIG ET AL.

FIG. 3. Profiles through zoned tourmaline samples Brazil 5 (left) and Brazil 6 (right). From top to bottom: d11B, d7Li,

secondary ion intensity of 55Mn, EPMA element mapping of Mn and image of the samples in transmitted light. The

black arrows indicate the location of the SIMS profiles. Except for the first three d7Li data points of Brazil 5, no

correlation between the chemical zonation and Li or B isotopes is evident. Error bars are 2s internal precision.

B AND LI ISOTOPIC COMPOSITIONS OF CU-BEARING ELBAITE

2491

FIG. 4. (a) Compilation of B isotope data of tourmaline from granites, pegmatites and related veins, modified after

van Hinsberg et al. (2011). Cu-bearing elbaites: this study; Borborema Pegmatite Province: Beurlen et al. (2011);

Lavicky granite and all other data from: Trumbull et al., (2011); Marschall and Ludwig (2006), and references

therein. (b) Compilation of Li isotope data of tourmaline from pegmatites (black boxes) in comparison to S-type

granite and pegmatite whole rocks (=WR, white boxes), as well as other minerals from pegmatites (grey boxes)

including spodumene, muscovite (Ms), plagioclase (Pl) and quartz. Data from Tomascak (2004), Bryant et al.

(2004), Teng et al. (2006), Maloney et al. (2008), Magna et al. (2010) and Liu et al. (2010). Cu-bearing elbaite and

reference elbaite #98144 from this study.

2492

T. LUDWIG ET AL.

pegmatites (Fig. 4). In previous studies, elevated

d11B values have been traced to the involvement

of carbonates or marine evaporites in the source

of the pegmatites or entrainment of such marine

materials into the magma from which the

tourmaline crystallized (e.g. Jiang, 1998; van

Hinsberg et al., 2011). Hence, the sample from

Alto Ligonha district may have crystallized in a

pegmatite dyke that had assimilated carbonates or

marine evaporites. Note however, that the

Harvard reference schorl (#112566), which is

also a sample from the Alto Ligonha pegmatite

district (Dyar et al., 2001), has a typical

continental crustal B isotopic composition, with

d11B = �12.5% (Leeman and Tonarini, 2001).

The Li isotopic compositions of the three

different localities fall into a relatively small

range, with values that can be considered typical

for minerals crystallized in pegmatites. It should,

though, be noted that the database on granites and

pegmatites is still small and the number of

tourmaline samples analysed for Li isotopes is

smaller yet (Fig. 4). However, a general trend is

that Li- and B-rich granite-pegmatite systems

show the following general evolution: (1) the

main granite bodies with relatively low Li (whole

rock [Li] = 5�150 mg/g) and trace-element

concentrations show low d7Li values in the

range typical for the continental crust (Fig. 4);

(2) pegmatites show a general increase in trace

elements and Li concentrations with increasing

magmatic differentiation, accompanied by an

increase in d7Li values; (3) pegmatite dykes

show strong Li isotopic disequilibria among

coexisting minerals, such as spodumene, tourma-

line, feldspar, mica or quartz (Fig. 4; Teng et al.,

2006; Maloney et al., 2008; Liu et al., 2010). This

Li evolution has been explained by fluid–melt

separation processes in the granite-pegmatite

systems and by preferential diffusive loss of

light Li from the pegmatite dykes into the country

rocks (e.g. Teng et al., 2006; Maloney et al.,

2008). Tourmaline Li isotopes are, therefore, not

suitable to trace the sources of pegmatites, but are

useful to monitor the evolution of individual

dykes or even smaller subsystems.

Acknowledgements

Michael Wiedenbeck (GFZ Potsdam, Germany) is

thanked for providing grains of the three reference

tourmalines for the d7Li MC-ICP-MS analyses.

We are grateful to two anonymous reviewers for

their detailed and constructive reviews, and to

Edward S. Grew for editorial handling and further

comments on the manuscript. HRM acknowl-

edges support provided by the Charles D.

Hollister Fund for Assistant Scientist Support

and The Penzance Endowed Fund in Support of

Assistant Scientists at WHOI. PPvS and MC-ICP-

MS analyses were funded by NERC grant

NE/F016832/1.

References

Beurlen, H., Trumbull, R.B., Wiedenbeck, M. and

Soares, D.R. (2011) Boron-isotope variations in

tourmaline from granitic pegmatites of the

Borborema Pegmatite Province, NE-Brazil.

Asociacion Geologica Argentina , Serie D,

Publicacion Especial, 14, 37�39.

Bryant, C.J., Chappell, B.W., Bennett, V.C. and

McCulloch, M.T. (2004) Lithium isotopic composi-

tions of the New England Batholith: correlations

with inferred source rock compositions. Transactions

of the Royal Society of Edinburgh: Earth Sciences,

95, 199�214.

Catanzaro, E.J., Champion, C.E., Garner, E.L.,

Marinenko, G., Sappenfield, K.M. and Shields,

W.R. (1970) Boric acid: isotopic and assay standard

reference materials. National Bureau of Standards

(US) Special Publications, 260-17, 1�71.

Dyar, M.D., Wiedenbeck, M., Robertson, D., Cross,

L.R., Delaney, J.S., Ferguson, K., Francis, C.A.,

Grew, E.S., Guidotti, C.V., Hervig, R.L., Hughes,

J.M., Husler, J., Leeman, W.P., McGuire, A.V.,

Rhede, D., Rothe, H., Paul, R.L., Richard, I. and

Yates, M. (2001) Reference minerals for micro-

analysis of light elements. Geostandards Newsletter:

The Journal of Geostandards and Geoanalysis, 25,

441�463.

Flesch, G.D., Anderson, A.R. and Svec, H.J. (1973) A

secondary isotopic standard for 6Li/7Li determina-

tions. International Journal of Mass Spectrometry

and Ion Processes, 12, 265�272.

James, R.H. and Palmer, M.R. (2000) The lithium

isotope composition of international rock standards.

Chemical Geology, 166, 319�326.

Jeffcoate, A.B., Elliott, T., Thomas, A. and Bouman, C.

(2004) Precise, small sample size determinations of

lithium isotopic compositions of geological refer-

ence materials and modern seawater by MC-ICP-

MS. Geostandards and Geoanalytical Research, 28,

161�172.

Jiang, S.-Y. (1998) Stable and radiogenic isotope studies

of tourmaline: an overview. Journal of the Czech

Geological Society, 43, 75�90.

Jiang, S.-Y. (2006) Reply to ‘Re-examination of the

boron isotopic composition of tourmaline from the

Lavicky granite, Czech Republic, by secondary ion

B AND LI ISOTOPIC COMPOSITIONS OF CU-BEARING ELBAITE

2493

mass spectrometry: back to normal’ by H.R.

Marschall and T. Ludwig: Critical comment on

‘Chemical and boron isotopic compositions of

tourmaline from the Lavicky leucogranite, Czech

Republic.’ Geochemical Journal, 40, 639�641.

Jiang, S-Y., Yang, J-H., Novak, M. and Selway, J.

(2003) Chemical and boron isotopic compositions of

tourmaline from the Lavicky leucogranite, Czech

Republic. Geochemical Journal, 37, 545�556.

Kasemann, S.A., Jeffcoate, A.B. and Elliott, T. (2005)

Lithium isotope composition of basalt glass refer-

ence material. Analytical Chemistry, 77, 5251�5257.

Leeman, W.P. and Tonarini, S. (2001) Boron isotopic

analysis of proposed borosilicate mineral reference

samples. Geostandards Newsletter, 25, 399�403.

Liu, X.-M., Rudnick, R.L., Hier-Majumder, S. and

Sirbescu, M.-L.C. (2010) Processes controlling

lithium isotopic distribution in contact aureoles: A

case study of the Florence County pegmatites,

Wisconsin. Geochemistry Geophysics Geosystems,

11, DOI: 10.1029/2010GC003063.

Magna, T., Janousek, V., Kohut, M., Oberli, F. and

Wiechert, U. (2010) Fingerprinting sources of

orogenic plutonic rocks from Variscan belt with

lithium isotopes and possible link to subduction-

related origin of some A-type granites. Chemical

Geology, 274, 94�107.

Maloney, J.S., Nabelek, P.I., Sirbescu, M.-L. and

Halama, R. (2008) Lithium and its isotopes in

tourmaline as indicators of the crystallization process

in the San Diego County pegmatites, California,

USA. European Journal of Mineralogy, 20,

905�916.

Marks, M.A.W., Rudnick, R.L., Ludwig, T., Marschall,

H., Zack, T., Halama, R., McDonough, W.F., Rost,

D., Wenzel, T., Vicenzi, E.P., Savov, I.P., Altherr, R.

and Markl, G. (2008) Sodic pyroxene and sodic

amphibole as potential reference materials for in situ

l i thium isotope determinations by SIMS.

Geostandards and Geoanalytical Research, 32,

295�310.

Marschall, H.R. and Ludwig, T. (2006) Re-examination

of the boron isotopic composition of tourmaline from

the Lavicky granite, Czech Republic, by secondary

ion mass spectrometry: back to normal. Critical

comment on ‘‘Chemical and boron isotopic composi-

tions of tourmaline from the Lavicky leucogranite,

Czech Republic’’ by S.-Y. Jiang et al., Geochemical

Journal, 37, 545�556, 2003. Geochemical Journal,

40, 631�638.

Marschall, H. R., Ludwig, T., Altherr, R., Kalt, A. and

Tonarini, S. (2006) Syros metasomatic tourmaline:

evidence for very high-d11B fluids in subduction

zones. Journal of Petrology, 47, 1915�1942.

Marschall, H.R., Pogge von Strandmann, P.A.E., Seitz,

H.-M., Elliott, T. and Niu, Y. (2007) The lithium

isotopic composition of orogenic eclogites and deep

subducted slabs. Earth and Planetary Science

Letters, 262, 563�580.

Marschall, H.R., Meyer, C., Wunder, B., Ludwig, T. and

Heinrich, W. (2009) Experimental boron isotope

fractionation between tourmaline and fluid: con-

firmation from in situ analyses by secondary ion

mass spectrometry and from Rayleigh fractionation

modelling. Contributions to Mineralogy and

Petrology, 158, 675�681.

Peretti, A., Bieri, W.P., Reusser, E., Hametner, K. and

Gunther, D. (2010) Chemical variations in multi-

coloured ‘‘Paraıba’’-type tourmalines from Brazil

and Mozambique: Implications for origin and

authenticity determination. Contributions to

Gemology, 9, 1�77.

Rosner, M., Wiedenbeck, M. and Ludwig, T. (2008)

Composition-induced variations in SIMS instrumen-

tal mass fractionation during boron isotope ratio

measurements of silicate glasses. Geostandards and

Geoanalytical Research, 32, 27�38.

Rossman, G.R. (2009) The geochemistry of gems and its

relevance to gemology: different traces, different

prices. Elements, 5, 159�162.

Rossman, G.R., Fritsch, E. and Shigley, J.E. (1991)

Origin of color in cuprian elbaite from Sao Jose de

Batalha, Paraıba, Brazil. American Mineralogist, 76,

1479�1484.

Shabaga, B.M., Fayek, M. and Hawthorne, F.C. (2010)

Boron and lithium isotopic compositions as prove-

nance indicators of Cu-bearing tourmalines.

Mineralogical Magazine, 74, 241�255.

Teng, F.Z., McDonough, W.F., Rudnick, R.L., Walker,

R.J. and Sirbescu, M.L.C. (2006) Lithium isotopic

systematics of granites and pegmatites from the

Black Hills, South Dakota. American Mineralogist,

91, 1488�1498.

Tomascak, P.B. (2004) Developments in the under-

standing and application of lithium isotopes in the

Earth and planetary sciences. Pp. 153�195 in:

Geochemistry of Non-traditional Stable Isotopes

(C.M. Johnson, B.L. Beard and F. Albarede, editors).

Reviews in Mineralogy and Geochemistry, 55.

Mineralogical Society of America, Washington DC

and the Geochemical Society, St Louis, Missouri,

USA.

Trumbull, R.B., Slack, J.F., Krienitz, M.-S., Belkin, H.E.

and Wiedenbeck, M. (2011) Fluid sources and

metallogenesis in the Blackbird Co–Cu–Au–Bi–Y–

REE district, Idaho, U.S.A.: insights from major-

element and boron isotopic compositions of tourma-

line. The Canadian Mineralogist, 49, 225�244.

van Hinsberg, V.J., Henry, D.J. and Marschall, H.R.

(2011) Tourmaline: an ideal indicator of its host

environment. The Canadian Mineralogist, 49, 1�16.

2494

T. LUDWIG ET AL.