631

Geochemical Journal, Vol. 40, pp. 631 to 638, 2006

*Corresponding author (e-mail: Horst.Marschall@bristol.ac.uk)*Present address: Department of Earth Sciences, Wills Memorial Build-

ing, Queen’s Road, University of Bristol, Bristol BS8 1RJ, U.K.

Copyright © 2006 by The Geochemical Society of Japan.

Re-examination of the boron isotopic composition of tourmaline fromthe Lavicky granite, Czech Republic, by secondary ion mass spectrometry:

back to normal.Critical comment on “Chemical and boron isotopic compositions of tourmaline

from the Lavicky leucogranite, Czech Republic” by S.-Y. Jiang et al.,Geochemical Journal, 37, 545–556, 2003

HORST R. MARSCHALL* and THOMAS LUDWIG

Mineralogisches Institut, Universität Heidelberg, Im Neuenheimer Feld 236, D-69120 Heidelberg, Germany

(Received December 2, 2005; Accepted July 14, 2006)

A re-examination of tourmaline from the Lavicky leucogranite by secondary ion mass spectrometry revealed a veryhomogeneous boron isotopic composition both on grain scale and on the outcrop scale. Tourmaline from tourmaline-quartz-feldspar orbicules and from tourmaline-quartz-feldspar veins show identical boron isotopic compositions of δ11B =–10.77 ± 1.24‰. This value is similar to the value for average continental crust. A comparison of the Lavicky tourmalinewith δ11B values of magmatic tourmaline available in the literature additionally demonstrates its rather ordinary character.The extremely negative δ11B values and the boron isotopic fractionation during the magmatic-hydrothermal transitionproposed in an earlier study (Jiang et al., 2003) are not supported by our data. The source region of the Lavicky graniteand its geochemical evolution did probably not involve any evaporitic material.

Keywords: Boron isotopes, tourmaline, Lavicky granite, SIMS

A detailed study on the boron isotopic evolution oftourmaline in a granitic system was completed by Jianget al. (2003) on the Lavicky granite (Czech Republic).This granite displays a succession of three generations oftourmaline in three different petrographic settings withina well-exposed outcrop: (i) Minor tourmaline occurs incoarse quartz-feldspar pegmatite dikes; (ii) egg-sized tour-maline-quartz-feldspar orbicules (Fig. 1a) formed at 550–650°C from the last portion of melt at its transition frommagmatic to hydrothermal processes (Jiang et al., 2003);(iii) 1–2 cm wide tourmaline-quartz-feldspar veins cross-cutting the leucocratic granite (Fig. 1b) formed at 350–440°C from hydrothermal fluids that exsolved from thelast residual melt (Jiang et al., 2003).

Jiang et al. (2003) reported extremely negative δ11Bvalues of down to –37.3‰ and observed a boron isotopicevolution from the earlier formed orbicules to the laterformed veins with δ11B values rising up to –21.3‰. Thesevalues are significantly below the previously reportedrange of boron isotopic compositions of magmatic tour-maline, and the measured range is untypically large for asimple magmatic-hydrothermal system. Other studies re-vealed only limited variations of <5‰ within single mag-matic bodies (Swihart and Moore, 1989; Chaussidon and

INTRODUCTION

Tourmaline is the most wide-spread boro-silicate min-eral in natural rocks. It contains ~3 wt.% B, an elementwhich is of very low abundance in most crustal and man-tle rocks, but which is commonly enriched in highly dif-ferentiated magmatic rocks. The boron isotopic compo-sition of tourmaline in granitoid rocks is a potentiallypowerful tracer for the source and the geochemical evo-lution of granitic systems (Swihart and Moore, 1989;Chaussidon and Albarède, 1992; Palmer and Swihart,2002) and of tourmalinites and ore deposits, i.e., basemetal deposits (Slack et al., 1989; Palmer and Slack, 1989;Slack, 2002). Chaussidon and Albarède (1992) also specu-lated on granitic tourmaline as a potential monitor for theevolution of the boron isotopic composition of seawaterthroughout the Earth’s history.

CRITICAL COMMENT

632 H. R. Marschall and T. Ludwig

Albarède, 1992; Tonarini et al., 1998). The uniquely lightisotopic compositions and the unusual large range withina single magmatic body aroused our curiosity. Therefore,we sampled the tourmaline orbicules and the tourmalineveins of the Lavicky granite at the same outcrop as Jianget al. (2003) and completed in-situ boron isotope analy-ses by secondary ion mass spectrometry (SIMS) atUniversität Heidelberg, Germany. In addition to the large-scale isotopic evolution, our study was intended to moni-tor possible δ11B variations during growth of individualtourmaline grains.

ANALYTICAL METHODS

Major element compositions of tourmaline were de-termined using a Cameca SX 51 electron microprobeequipped with five wavelength-dispersive spectrometers(Mineralogisches Institut, Heidelberg). Operating condi-tions were 20 nA beam current and 15 kV accelerationvoltage. The electron beam was defocused to 5 µm in or-

der to avoid loss of alkalis, F and Cl. Details on countingtimes, crystals, standards and detection limits are givenin Marschall (2005). PAP correction was applied to theraw data (Pouchou and Pichoir, 1984, 1985). A modifiedmatrix correction was applied assuming stoichiometricoxygen and all non-measured components to be B2O3. Theaccuracy of the electron microprobe analyses of tourma-line and the correction procedure was checked by meas-uring three samples of reference tourmalines (98144:elbaite, 108796: dravite, 112566: schorl; Dyar et al., 1998,2001). Under the described conditions, analytical errorson all analyses are ±1% relative for major elements and±5% relative for minor elements. A detailed descriptionof the electron microprobe techniques for tourmalineanalysis is given in Kalt et al. (2001). Concentrations ofB2O3 were calculated stoichiometrically to 3 B per for-mula unit; H2O contents were calculated to 4 (H + F +Cl) per formula unit. All Fe was assumed to be divalent.

B isotope ratios were measured by secondary ion massspectrometry (SIMS) with a modified Cameca IMS 3f ion

Fig. 1. (a) Field image of tourmaline-quartz-feldspar orbicules in Lavicky granite. (b) Field image of tourmaline-quartz-feld-spar vein in Lavicky granite. (c) Micro photograph of thin section of sample LAV1, taken from a tourmaline orbicule (width ofview ≈4 cm). (d) Micro photograph of thin section of sample LAV2, taken from a tourmaline vein (width of view ≈4 cm).

Boron isotopic composition of tourmaline 633

microprobe (equipped with a primary beam mass filter)at the Mineralogisches Institut, Heidelberg. Both softwareand hardware of the SIMS have been changed in order toallow for the precise and accurate analysis of boron iso-tope ratios. Most important were changes in the electroniccontrol device of the magnet, which allow for fasterswitching between different masses and better stabilityof the magnet. The changes are described in detail inMarschall (2005).

Primary ion beam was 16O– accelerated to 10 keV witha beam current of 1 nA, resulting in count rates for 11B of~2 × 105 s–1 and ~5 × 104 s–1 for 10B on tourmaline, col-

lected by a single electron multiplier. The diameter of the1 nA spot was ≤5 µm. The energy window was set to 100eV and no offset was applied. 50 cycles were measuredon each analysis spot with counting times of 3.307 s and1.660 s on 10B and 11B, respectively. Presputtering lastedfor 5 min and settling time between two different masseswas 200 ms, resulting in total analysis time for one spotof approximately 10 min. Internal precision of a singleanalysis was ≤1‰ (2σ). Boron isotopic compositions ofsamples are reported in delta notation (δ11B in ‰) rela-tive to the SRM 951 accepted value (Catanzaro et al.,1970). Instrumental mass fractionation was corrected by

Sample LAV1 LAV2

Type orbicule vein

SiO2 34.52 34.33 34.49 35.24 35.07 34.76TiO2 0.61 0.51 0.41 0.81 1.10 0.51B2O3* 10.36 10.35 10.41 10.38 10.40 10.41Al2O3 34.18 33.97 34.39 29.94 29.33 33.88Cr2O3 0.02 0.01 0.03 0.04 0.01 0.04FeOt 11.91 12.42 11.82 8.66 8.28 9.15MnO 0.21 0.16 0.19 0.07 0.03 0.03MgO 2.25 2.46 2.72 7.02 8.11 4.39CaO 0.21 0.23 0.23 1.95 1.98 0.30ZnO 0.07 0.03 0.00 0.04 0.06 0.06Na2O 1.93 2.02 1.94 1.73 1.63 1.92K2O 0.06 0.05 0.05 0.07 0.06 0.04H2O* 3.29 3.26 3.29 3.33 3.29 3.28F 0.60 0.66 0.63 0.53 0.61 0.65Cl 0.00 0.01 0.00 0.00 0.01 0.00-(F + Cl) = O 0.25 0.28 0.27 0.22 0.26 0.27Total 99.97 100.21 100.31 99.59 99.72 99.15

Formulas calculated to 31 oxygens, Fe2+ = Fe t

Si 5.79 5.76 5.76 5.90 5.87 5.81Ti 0.08 0.06 0.05 0.10 0.14 0.07Al 6.76 6.72 6.77 5.91 5.78 6.67Cr 0.00 0.00 0.00 0.01 0.00 0.01Fe2+ 1.67 1.74 1.65 1.21 1.16 1.28Mn 0.03 0.02 0.03 0.01 0.01 0.01Mg 0.56 0.62 0.68 1.75 2.02 1.09Ca 0.04 0.04 0.04 0.35 0.36 0.05Zn 0.01 0.00 0.00 0.01 0.01 0.01Na 0.63 0.66 0.63 0.56 0.53 0.62K 0.01 0.01 0.01 0.02 0.01 0.01Total** 18.57 18.65 18.62 18.83 18.88 18.61

Fe/(Fe + Mg) 0.75 0.74 0.71 0.41 0.36 0.54Na/(Na + Ca) 0.94 0.94 0.94 0.62 0.60 0.92

OH 3.68 3.65 3.67 3.72 3.67 3.66F 0.32 0.35 0.34 0.28 0.33 0.34Cl 0.00 0.00 0.00 0.00 0.00 0.00

Table 1. Representative chemical analyses of tourmaline from Lavicky

*H2O and B2O3 contents calculated stoichiometrically.**Including 3 B per formula unit.

634 H. R. Marschall and T. Ludwig

using three samples of proposed reference tourmaline(98114: elbaite, 108796: dravite, 112566: schorl; Dyar etal., 1998; Leeman and Tonarini, 2001), which range from–12.5‰ to –6.6‰ (Leeman and Tonarini, 2001). Repro-ducibility of measured isotope ratios during an eight daysanalytical session was ±0.5‰. In order to ensure accu-racy of our SIMS lab, intercomparison with positive ther-mal ion mass spectrometry (P-TIMS) has been performedearlier for a wide range of tourmalines and other materi-als. Instrumental mass fractionation of SIMS has beenproven to be independent from tourmaline chemistry (i.e.,no matrix effects) and from 11B/10B ratios in the range ofδ11B between –12.5‰ and +22.9‰ (Marschall et al.,2006).

CHEMICAL COMPOSITION OF LAVICKY TOURMALINE

Electron microprobe analyses of tourmaline fromorbicules and veins (Table 1) revealed similar composi-tions to those reported by Jiang et al. (2003) for orbiculeand vein tourmaline from Lavicky, respectively. Orbiculetourmaline (sample LAV1) is schorl with Fe/(Fe + Mg)ratios between 0.71 and 0.75 and Na/(Na + Ca) ratiosbetween 0.92 and 0.96. In contrast, vein tourmaline (sam-ple LAV2) shows a larger spread in compositions with apatchy zonation. Some domains show much higher Caand Mg concentrations, with Fe/(Fe + Mg) ratios between0.36 and 0.54 and Na/(Na + Ca) ratios of ~0.60. How-ever, other domains within the same grains are similar incomposition to tourmaline from the orbicules, with Fe/(Fe + Mg) ratios of ~0.75 and Na/(Na + Ca) ratios ~0.92.Ca-Mg-rich domains also show Al contents below 6 performula unit (Table 1 and Jiang et al., 2003).

BORON ISOTOPIC COMPOSITION OF LAVICKY

TOURMALINE DETERMINED BY SIMS

Analyses of inclusion-free parts of tourmaline grainsfrom a tourmaline orbicule sample (LAV1, Fig. 1c) and atourmaline vein sample (LAV2, Fig. 1d) revealed entirelyhomogeneous boron isotopic compositions of all investi-gated tourmaline grains with a mean value of δ11B =–10.77 ± 1.24‰ (Table 2). δ11B values in LAV1 rangefrom –11.4‰ to –9.8‰ with an average of –10.75 ±1.09‰ (Table 2). δ11B values in LAV2 range from –11.5‰to –9.8‰ 1 with an average of –10.78 ± 1.42‰ (Table 2).No difference was found between tourmaline core andrim regions, i .e., grains from both samples wereisotopically homogeneous. Altogether, both samples showidentical boron isotopic compositions, which is in strongcontrast to the apparent evolution observed by Jiang etal. (2003). Furthermore, the composition is entirely dif-ferent from the extreme values determined by these au-thors.

POSSIBLE SOURCES OF DISCREPANCY BETWEEN

JIANG ET AL. (2003) AND OUR DATA

The strong discrepancy between our data and the dataof Jiang et al. (2003) is highly unlikely to result frominhomogeneities within the Lavicky granite, as our sam-ples were taken from the very same outcrop within a fewmeters distance from each other, and our SIMS data dem-onstrate that the granite seems to be isotopically homo-geneous on that scale. In addition, electron microprobeanalyses of orbicule and vein tourmaline show that ma-jor element composition of samples investigated in ourstudy are very similar to the samples analysed by Jiang etal. (2003). Therefore, it must be concluded that problemshave occurred during boron isotope analysis in one lab.SIMS today is a standard technique for the analysis ofboron isotope ratios in tourmaline (Chaussidon andAlbarède, 1992; Smith and Yardley, 1996; Trumbull andChaussidon, 1999; Matthews et al., 2003; Altherr et al.,2004; Marschall et al., 2006). Tourmaline can be analysedwith suitable precision (typically ±1‰, 2σ) in a short to-tal analysis time with high spatial resolution. The estab-lishment of widely distributed proposed reference tour-maline samples for boron isotope analysis (Leeman andTonarini, 2001) allows for a direct calibration of instru-mental mass fractionation and possible matrix effectsduring analyses of any tourmaline sample. The SIMSanalyses of boron isotope ratios of tourmaline at theUniversität Heidelberg were repeatedly verified by meas-urements of reference tourmaline and by the analysis of

Table 2. Boron isotope values of tourmaline from theLavicky granite

Analysis No. Type δ 11B (‰) 2 RSDmean (‰)

LAV1 (orbicule)LAV1-1 rim –10.71 0.91LAV1-2 rim –10.97 0.88LAV1-3 core –10.99 0.93LAV1-4 core –10.61 0.85LAV1-5 rim –11.43 0.82LAV1-6 rim –9.81 1.07Average LAV1 –10.75 1.09

LAV2 (vein)LAV2-1 rim –11.46 0.99LAV2-2 rim –11.54 0.91LAV2-3 rim –11.48 0.85LAV2-4 rim –11.12 0.99LAV2-5 rim –10.45 0.88LAV2-6 rim –10.01 0.76LAV2-7 core –10.43 0.91LAV2-8 core –9.76 0.79Average LAV2 –10.78 1.42Average all analyses –10.77 1.24

Boron isotopic composition of tourmaline 635

homogeneous tourmaline that are well-characterised byindependent measurements performed by Sonia Tonarini(Pisa) using P-TIMS (Marschall et al., 2006). Hence, theSIMS analysis are highly reliable.

Boron isotope analysis of tourmaline has always beenan analytical challenge, as has been demonstrated by labo-ratory intercomparison studies (Tonarini et al., 2003;Gonfiantini et al., 2003). Erroneous results from analy-ses using bulk methods may be caused by difficultiesduring sample preparation, rather than during the actualmass spectrometry. On one hand, tourmaline is not read-ily soluble in acids, requiring strong and enduring treat-ment, on the other hand, boron is a highly fugitive ele-ment, with its isotopes being fractionated during evapo-ration from solutions or melts. Therefore, sophisticatedpreparation methods have been developed, usingpyrohydrolysis of solid tourmaline (Palmer and Slack,1989; Aggarwal and Palmer, 1995), boron complexationby mannitol in solutions in closed containers (Ishikawaand Nakamura, 1990; Nakamura et al., 1992) and alkalicarbonate fusion of tourmaline in closed containers(Tonarini et al., 1997). In general, accuracy during massspectrometry is controlled by measuring standard boricacid, which is easily dissolved in pure water and intro-duced into the spectrometers. However, it is crucial foranalytical quality to also keep control of the sample prepa-ration procedure, by preparing tourmaline standard ma-terial parallel to the samples.

In earlier studies of boron isotope analyses of tour-maline, Jiang et al. used the pyrohydrolysis method forsample preparation (Jiang, 1998, 2001; Jiang et al., 1999,2002), whereas they employed an acid digestion methodin their study on the Lavicky tourmaline (Jiang et al.,2003). Unfortunately, no reference tourmalines were ana-lysed during the latter study.

THE LAVICKY SAMPLES IN COMPARISON TO

OTHER MAGMATIC TOURMALINE

The establishment of a broad data base of boron iso-tope data of magmatic tourmaline is restricted by the dif-ficulty of obtaining accurate and precise boron isotopeanalyses, as well as the lack of an appropriate range ofwell-characterised samples. The second point might besurprising, as tourmaline appears frequently in graniticand pegmatitic outcrops. However, it is crucial for anunambiguous interpretation of the boron isotopic com-position to carefully select the samples after a detailedpetrographic investigation of the granite-pegmatite-hy-drothermal system. For some of the published data a criti-cal evaluation is hampered by the lack of a detailed de-scription of the investigated samples, as was already criti-cised by Palmer and Swihart (2002).

Tourmaline is a typical accessory phase in leucocratic

peraluminous granites and starts to crystallise when thealuminium saturation index (ASI) reaches a value of 1.3to 1.4, the B2O3 concentration is reaching a value of ~2wt.%, and a certain amount of Fe and Mg is available inthe melt (London and Manning, 1995; Wolf and London,1997; London et al., 2002). Tourmaline is unstable inperalkaline, metaluminous and slightly peraluminousmelts with an ASI <1.2 (Wolf and London, 1997). Tour-maline in “S-type granite” (Chappell and White, 1974)has been subdivided into several different types on thebasis of its petrographic appearance by London et al.(2002): (i) Disseminated tourmaline occurs as isolated,relatively unzoned prisms or interstitial grains as a minoror accessory phase in granites or the fine-grained units ofpegmatites. This tourmaline-type has in most cases di-rectly crystallised from the magma, and is referred to asprimary tourmaline, representing the primary boron iso-topic composition of the melt. (ii) Tourmaline at the bor-der of granites and pegmatites to the surrounding coun-try rock forms continuous comb-like layers, which seemto have grown from the contact perpendicular into theleucocratic magma. The essential chemical componentsof this tourmaline-type are probably provided by the wallrock (Fe, Mg) and the magma (B, Na, Al). The boron iso-topic composition of this tourmaline type in most casesshould be governed by B from the melt. (iii) Tourmalinein miarolitic cavities has grown from a fluid phase in thefinal stage of granitic consolidation. Its chemistry tendsto shift towards an Fe-Mg-poor, Li-rich elbaitic compo-sition, while the B-isotopic composition is representingan exsolved fluid phase rather than the granitic melt. (iv)Tourmaline in breccias and veins within the country rockor in the pegmatitic dikes are formed by the hydrother-mal activity in the outer parts of intrusions and the coun-try rocks. This tourmaline-type may form massivetourmalinites or may be related to ore deposits in skarnsor greisen. Its chemical and boron isotopic compositionrepresents a mixture of magmatic boron and boron leachedfrom the country rocks.

The literature data base on δ11B values of magmatictourmaline is limited not only by the number of investi-gated samples, but also by the fact that in many cases it isnot obvious which type of tourmaline has been investi-gated by the authors. For several published values it istherefore unclear whether they represent primary, dissemi-nated tourmaline, or any of the other types that may rep-resent a boron signal, influenced by the country rocks,by degassing or by mixing with meteoric water. How-ever, a compilation of virtually all literature data avail-able on (more or less) primary tourmaline is presented inFig. 2. Most analyses revealed δ11B values in the rangeof –15 to –5‰. Strong deviation from this range is gen-erally seen as evidence for the assimilation of marineborates (Jiang, 1998) or continental evaporates (Slack et

636 H. R. Marschall and T. Ludwig

al., 1989) into the granitic magmas. The average of allinvestigated tourmaline samples of –11.3 ± 5.4‰ (exclud-ing the samples influenced by continental or marineevaporates) represents a value close to the average conti-nental crust of –10 ± 3‰, which was determined byChaussidon and Albarède (1992) and by Kasemann et al.(2000) on the basis of a selection of granitic and meta-morphic tourmaline. The apparent extreme δ11B valuesat Lavicky are explained by Jiang et al. (2003) by as-similation of continental evaporates into the graniticmagma, similar to the explanation given by Slack et al.

Fig. 2. Compilation of literature data on δ11B values of tourmaline from various pegmatites, granites and aplites. Open symbolsrepresent SIMS analyses; filled symbols represent TIMS analyses; half-filled symbol represents a study that applied variousmethods. Different symbols represent data from different authors. Data are from 1Matthews et al. (2003), 2Smith and Yardley(1996), 3Jiang et al. (2002), 4Jiang (1998), 5Chaussidon and Albarède (1992), 6Tonarini et al. (1998), 7Gonfiantini et al. (2003),8Leeman and Tonarini (2001), 9Swihart and Moore (1989), 10Jiang (2001), 11Kasemann et al. (2000), 12Chaussidon and Albarède(1992) and Trumbull and Chaussidon (1999), 13Slack et al. (1993, pegmatite tourmaline only), 14Marschall (unpubl. data fromtourmaline in pegmatites). Stars represent SIMS data from Lavicky granite tourmaline obtained in this study. The range of aver-age continental crust (–10 ± 3‰, Chaussidon and Albarède, 1992; Kasemann et al., 2000) is represented by the grey area.

δ11 B of tourmaline

+10 0 −10 −20 −30

Naxos, Greece1

Lavicky granite orbicules(this study)

Lavicky granite veins(this study)

SW England2

Big Bell, Australia3

Hellroaring creek, Canada4

China4

Tanco, Manitoba5

Bouaflé, Ivory Coast5

Soublaké, Ivory Coast5

Niger5

China5

Himalayan leucogranite5

Elba, Italy5

Elba, Italy6

Elba, Italy7

Zambesi, Mosambique8

Foot mine, North Carolina9

Harvard and Dunton, Maine9

China10

Puna Plateau, Central Andes11

Broken Hill, Australia(Boron from continental

evaporites)13Karibib, Namibia14

Ronda, Spain14

Sinceni pluton, Swaziland12

Minas Gerais, Brasil8

Madagascar8

Sar-el-Sang, Afghanistan9

China, crosscuttingmarine borates4

Sigma mine, Abitibi5

Massif Central5

Cornubian batholith5

Algeria5

(1989) for samples from Broken Hill, Australia. However,in the case of Lavicky, no geochemical evidence, such ashigh sulphur contents, Cl/Br or Cl/I ratios are supportingthis hypothesis. The large variation and the strong increasein the measured δ11B values is explained by boron iso-topic fractionation during fluid-melt exsolution (Jiang etal., 2003).

Our results demonstrate that the boron isotopic com-position of tourmaline from the Lavicky leucogranite(δ11B ≈ –10.8‰) is similar to the average continental crustand to the average composition of all magmatic tourma-

Boron isotopic composition of tourmaline 637

line reported so far. The Lavicky granite therefore seemsto be quite ordinary and shows no evidence for a contri-bution of evaporitic material to the granitic magma. Ad-ditionally, no evidence for boron isotopic fractionationduring late stage magmatic-hydrothermal processes hasbeen found in the succession from the tourmalineorbicules to the tourmaline veins.

CONCLUSIONS

SIMS in-situ analyses of tourmaline from the Lavickyleucogranite revealed a very homogeneous boron isotopiccomposition both on grain scale and on the outcrop scale.Tourmaline from orbicules (sample LAV1) and from veins(sample LAV2) both showed identical boron isotopic com-positions of δ11B ≈ –10.8‰. This value is similar to thevalue for average continental crust of –10 ± 3‰(Chaussidon and Albarède, 1992; Kasemann et al., 2000).Therefore, the source region of the Lavicky granite andits geochemical evolution did probably not involve anyevaporitic material. Our data do not support the boronisotopic fractionation during the magmatic-hydrothermaltransition proposed by Jiang et al. (2003) for the Lavickygranite. It must be considered that problems during sam-ple preparation have influenced the analysis of Jiang etal. (2003). B isotope data published so far and summa-rised in this paper demonstrates that δ11B values of mostgranitic-pegmatitic tourmaline range from ≈–15 to –5‰.Strong outliers are found, where the granitic magma as-similated marine (positive δ11B) or continental (stronglynegative δ11B) evaporates. B isotopic composition of tour-maline, therefore, seems to be a powerful tool for thedetection of such a reservoir involved in the evolution ofits host granite. However, because of the rather small database available so far, this tool more than others is endan-gered to be weakened by sporadic erroneous data.

Acknowledgments—Milan Novak is thanked for guiding usin the field during the “Light Elements in Rock-forming Min-erals (LERM)” conference field trip in 2003. Ilona Fin andOliver Wienand are thanked for preparing high-quality thin sec-tions for SIMS investigations. Rainer Altherr and StefanProwatke are thanked for helpful comments on an earlier ver-sion of this manuscript. We are also thankful to SimoneKasemann and Marc Chaussidon for helpful and constructivereviews, and to Torsten Vennemann for editorial handling.

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