835

The Canadian M irc r alog is t Vol. 33,pp. 835-848(1995)

TOURMALINEIN GRANITICPEGMATITES AND THEIRGOUNTRY ROCKS, FREGENEDAAREA, .

ENCARNACI6N ROpa, ALFONSO PESQIIERA ANDFRANCISCO VELASCO Departamentod.e Mineralagta y Petrolagfa,Universidad del Pats VascolEHU, Aptdo, 644, 848080, Bilbao, Spain

ABSTRACT

In the northwestempart of the (Spain), many Li-, Sn-bearingand barrengranitic pegmatitesoccur. Thesebodies display a zonal distribution northwardfrom the Lumbralesgranite, with a degreeof evolution increasingwith distancefrom the granite contact.Tourmaline appearsas an accessorymineral in the barren pegmatites,as well as in their country rock In both cases,the tourmalinebelongs to the schorl-dravite solid-solutionseries. Tourmaline shows texfiral and conpositional variations in relation with pegmatite type. Subhedralto euhedralprismatic, very fine- to medium-grained (<6 mm - 10 cn), zonedgrains are most common.In the country rock, tourmalineapp€an as prismatic-euhedral,very fine- grained(<6 mm) crystals.Their Fe/lVIgvalue cha:rgesconsiderably among the different pegmatitetype.s, providing insigbt into the degreeof evolution of the associatedpegmarites: those richest in Fe andpoorest in Mg are associatedvrith the most evolved bodies.Tourmaline from the countryrocks showscompositional characteristics inherited from the host schists:similarity ofthe shapeofthe REE parerns for tourmalineand the schists,and a high contentin Cr, I{f, Th and U.

Keyword*: tourmaline,granitic pegmatite,schorl-dravite, Fregeneda" Spain.

Sotvfttens

Dansle secteurnord-ouest de la province de Salamanca,en Espagne,se trouvent plu$ieurs massifs de granit€p€gmatitique, soit lithinifdres, stannifbresou st6riles.Ces diff6rents facids sont dispos6sd'une fagon zonaire i partir du granite de vers le nord et monhent un degr6 d'6volution progressivementplus avanc6en s'6loignantdu contact.La tourmaline est un min6ral accessoiredans les pegmatitesst6riles, de m6meque dansles rochesencaissantes. Dens les deux cas,la tourmalinefait partie de la s6rieschorl-dravite. l,a tourmalinemontre des diff6rencestexturales et chimiquesselon le facibs de la pegmatite. lrs prismessubidiomorphes i idiomorphes,i granulom6frietrbs fine ou moyenne(<6 -- - 10 cm) et zon6ssont les plus courants.Dans les rochesencaissantes, la tourmaline est prismatiqueet idiomorphe, et possbdeune granulomdhietrbs fine (<6 mm). Ia valeur Fe/Mg varie consid6rablementd'un facibsi I'autre,de fagonh indiquer le degr6d'6volution de la pegmatite h6te. l,a tourmalinela plus riche en Fe et la plus pauwe en Mg estassocide avec la pegmatitela plus 6volude,Ia composition de la tourmaline des roches h6tes reprend les traits compositionnelsde celles-ci, par exemple une ressemblancedans I'enrichissementrelatif desterres rares et une teneur6lev6e en Cr, I{f, Th et U. (Iraduit par la R6daction)

Mots-cl6s:toummline, pegmatite granitique, schorl-dravite, Fregeneda" Espagne.

INTRoDUciloN The compositionof the tourrnalinereflects the bulk chemisty of the systemin which it forms, and some In the Fregenedaaxea of Spain, different types of studies have establishedits value as a petrogenetic granitic pegmatitescan be establishedon the grounds indicator(e.9., Shearer et al.1984, Henry & Guidotti of mineralogical and geological criteria and spatial 1985, Jolliff et al. L986, Kassoli-Foumaraki 1990, disnibution arcundthe Lumbralesgranite (Fig. 1). The Pirajno & Smithies 1992, Kassoli-Fournaraki& most common type correspondsto simple pegmatites Michailidis 1994. Michailidis & Kassoli-Foummaki without internal zonation. Zoned, Li-bearing 1994, Hellingwetf et al. 1994). In this study, petro- pegmatitesalso are relatively coulmon, as are peg- graphicand chemicaldata on representativesamples of matitic veins containing quartz, muscovite,feldspars, tourmaline selected from the various groups of and cassiterite.Tourmaline appears as an accessoryor pegmatitesin the Fregenedaarea and their extensively major mineral in many of thesepegmatites, and it is tourmalinized county-rock are given. The chemical also common in the country rock, near the contacts yariationsare discussedin order to determinewhethfr with pegmatitebodies. these different types of pegmatite l) are related by a 836 TI{E CANADIAN MINERALOGIST

+++++ + +++ +++ +++ ++. +++*++++++++++++++' PORTUGAL +++ti++++++++++++++' N +{'+++++++++++++++ +#+++++++++++++++. if, iSau'cdtlleeiinit'e' I i I: ++++++++ + ++++ +. Duero !$1{ +++++++++++++* ++++++++++++++, +++++++++++++++' +++++++++++++++. A +++++++++++++. ts+++++++++++++. ++++++++++|\+++. ++{L+A+ 0 1Kn + +++ TT ++

Ar (f) a slnxpleintraCraniticpep. (2) tr qpa&+afilalusitecodomable dykes ^dp*** (3) O simpledyke.sandapophyses (4) I sinplscodomablepoeltr +++++++ (9 A K-fetdspardiscodandykes +.7++ +++.f+++++ (O + + +a+t"+-l +++++++++++ siEplediscorda$psgpr, *+++++++ +++++++++ (4 a U-beadngdtscorderpeg4. ++++++ +++++++++++ ++ Fn ++++*+ +++++ (8) o Sn-bearing

B,LBiotiteisograd E Schist-Metagraywacke-Complex ar. Andalusileisograd .o Fracturecontaining quartz segregations sJ. Si[imanite isograd

Ftc. 1. Distribution ofthe pegmatitegroups recognized in the Fregenedaarea The pegmatitetypes are labeledas in Table l.

commonpath of fractionation,and 2) arerelated to the isograd, led to incipient partial melting of the meta- nearbyLumbrales granite. sedimentary units at approximately 650'C and 3.5 kbars, coinciding, in general,with the appearance Gsot,octcAr,Srrrwc of cordierite- K-feldsparin the migmatitic leucosome (Garcia Luis 1991). The episodeof regional meta- The pegmatitesof the Fregenedaarea appear in the morphism precededthe second phase of Hercynian HespericMassif, in tbe westernpart of a trarrow meta- deformation(Carnicero 1982), and it is superimposed morphicbelt, with an E-W strike. This belt, situatedin by a contact metamorphismthat may be due to the northwesternSalamanca, is borderedby the Lumbrales presenceof a hidden granitic pluton, which has been pluton to the south, and by the Saucellepluton to the detectedat depthby clrilling Q.6pezPlazaet al. L982). northeast(Fig. 1). Both granites and pegmatitesare One of the mdn characteristicsof this area is the intrusive into pre-Ordovician metasedimentsof the great diversity of granitesthat outcropthere. The most Schist-MetagraywackeComplex. In this area, this common group is that of the peraluminous leuco- Complex comprises a sequenceof quartzites, gray- granites,to which the Lumbralesand Saucelleplutons wackes,schists and pelites, with abundantfhin hysrs belong @g. 1). The former is part of the Meda- of calcsilicate. These materials have undergonetwo Penedono-Lumbralesgranitic complex (Bea et al. main phasesof Hercynian deformation,with the later 1988), and consists of a parautochthonous,hetero- event of lower intensity (Martfnez Fem{adez L974). geneous,fine- to medium-grainedtwo-mica granite The earlierphase gave rise to a regionalmetamorphism (Carnicero1981). With regardto the Hercyniandefor- that in the Fregenedaarea shows a distribution of mation, this pluton is included in the group of isograds parallel to the Lumbrales granite, locally syntectonicmassifs that have been deformedduring a lsnshing the sillimanite zone,whereas the biotite zone third phaseof Hercynian deformation Q-6pezPlaza& is the most extensive (Frg. 1). The regional meta- Carnicero 1988, I-6pez Plaza & Martlnez Catal{r morphism,of medium fe high grade,and interrnediate 1988),with a Rb-Sr isochron age of 284 t 8 Ma pressures,determined by the sillimanite - K-feldspar (Garcia Gan6n & Locutura 1981). In spite of its TOURMALINE IN GRANITIC PEGMATITES.SPAIN 837

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z c, E trF o*'E oF.B., F >€do sfls€ sEEsE3€ fl a$sEs€gEgs,E

}i F THE CANADIAN MINERALOGIST

evident petrological continuity, the Lumbralespluton Lumbrales granite. They are associaledmainly with showsa cleartectonic contol westward,whereas to the the andalusitezone and to a lesser extent with the east the deformationdecreases, and the emplacement sillimanite and biotite zones. ofthe graniteseems to havebeen free ofexternal sffess (5) Pegmatitebo'dies mainly composedof K-feldspar (Gonzalo Conal 1981, L6pez Plaza et al. 1982). (microcline and orthoclase).Other phasesthat may be Another characteristicof this body is the presenceof a present are quartz, muscovite and pyrile. They are migmatitic facies in the border as well as in the inner discordant to the country rock, appearing near the zones,mainly to the east ofthe Fregenedaarea. As is contact with the Lumbrales granite, associatedwith the casefor the Lumbralespluton, the Saucellepluton the biotite zone. is a peraluminous,fine-grained, two-mica granite,and (6) Discordantbodies of pegmatitethal in somecases, it belongsto the group of syntectonicmassifs that were show a layered internal structure. They consist of deformedduring the third phaseof Hercynian defor- quartz, K-feldspar (microcline and orthoclase), mation (L6pez Plaza & Camicero 1988).With regard muscovile,and albiie. In the bodies farthest from the to their degree of rare-element enrichmsfi, ftsy Lumbralesgranite, amblgonite may appear,whereas contain 170-230ppm Li, 343 ppm Rb and218 ppm Ba close to the granite, phosphatesof Fe-Mn t Li are (Garcfa Gam6n & Locutura 1981, Bea & Ugidos common, as well as tourmaline as an accessory 1976).The high contentsin Li and Rb are noreworthy, mineral. Moreover. the host rock can show a variable as are the low contentsof Ba in both series.The K/Rb degreeof tourmalinization.Situated in an areabetween ratio alsois low, with valuesbelow 160@ea 1976, Bea I and4 km to the north of the Lumbralespluton, group & Ugidos 1976), characteristicof granitic pegmatite 6 is the most abundant.The host rocks exhibit low- and higtrly differentiatedgranites (Ahrens et al. L952). grade regional metamorphism (biotite and cblorite zones). PecMArnETVpEs (7) Discordant bodies of Li-mica-bearing pegmatite. Thesebodies usually display a zonedinternal structure. On the basisof mineralogy,morphology, and inter- They are composedof quartz,Li-bearing mica, albfte, nal structure, several groups of granitic pegmatites K-feldspar (microcline and orthoclase),muscovite and have been recognized.These groups display a degree minor amblygonite, spodumene,cassiterite, apatite, of differentiation that increases awav from the and columbite-tantalite. f6urmaline has not been Lumbrales granite. With increasing distance from found in thesepegmatites, although tourmalinization is the contact the groupsare @oda et al. 1991,Roda & variably developedaround the pegmatites.These dykes Pesquera,inpress) (Fig. I, Table 1): crop out along a narow ban4 4 6 km north of the (1) Infagranitic bodies of pegmatite consisting of Lumbrales granite. As is the case with the previous quartz, K-feldspar (-icrocline and orthoclase), ca0egory,these bodies of pegmatiteare associatedwith muscovite,albite and schorl; thesebodies are relative- the biotile aud chlorite zones. ly abundantin the borderzones ofLumbrales pluton. (8) Bodies of pegmatiteconsis t"rg of quartzand minor (2) Dykes composedmainly of quartz, andalusiteand fine-grained muscovite, albite, microcline and minor muscovite, schorl and K-feldspar (microcline cassiterile. Their county rock exhibits a variable and orthoclase), of pegmatitic grain-size. They are degreeof tourmalinization;as in the previous group, concordantto the coun!ry-rockfabric, showingrelated tourmalinehas not been found as a constifirentofthe deformation,witl a boudinagesfiucture. These bodies pegmatites. These dykes locally show internal appearin the andalusite--cordieritezone, close to the zonation, being folded, with the axial plane neady Lumbralesgranite. horizontal.They appearin the norflem zoneofthe area (3) Dykes and apophyses showing aplitic and studie4 being cut by some bodies of the previous pegmatitic facies, consisting of quartz, K-feldspar category. These dykes are only associa0edwith the (microcline and orthoclase), muscovite sad minel chlorite zone. albite, schorl, and biotite. Their grain size changes abruptlyfrom an aplitic to a pegmatiticfacies, and their PsrRocRAPnY shapesvary geatly. These bodies are localed to the southeastof the area studie4 near the Lumbrates Textural and paragenetic differences among the granite,associated with the sillimanite, andalusite,and tourmaline samples from the various fypes of biotite zones. pegmatilehave beenobserved (Table 2). Three modes (4) Conformablebodies of pegmatiteof narrow width of occurrencecan be established.The first one is a (<1.5 m), locally showing internal zoning. They are medium to very fine-grained (5 cm - <6 -m), composed mainly of quartz, muscovite, K-feldspar prismatic tourmaline, that appears homogeneously (microcline and orthoclase),schorl, albite, and minor distributed in the intragranitic pegmatites(1), in the andalusite, chlorite, game! and biotite. Host rocks quartz-andalusitedykes (2) nd in the apophyseswith commonly display strong tourmalinization near aplitic and pegmatiticfacies (3). Commonly,this type the contacts. These bodies are located close to ttre of tourmalinegrows with quarczin the core zonein the TOI]RMALINEIN GRANITICPEGMATITES. SPAIN 839

TABLE 2. TOURMALINE DISTRIBUTION IN TIIE FRECENEDAPEGMATTTES AND TI]EIR TOTIRMAUNTZEDCOI.INTRY-ROCI(

PEGM.TOURMAL.OCCURRENCE MINBNAL ASSOCIATION TEXTURE GRAIN SIZE'I TYPE' TYPE

mainly in the qu8%K-Feldspfr, sub-oeuhedral fiIEto 1 intEmediate albite, muscovie prismatic, aned medium z&e gains I withln the quar%K-Ibldspar,albib' $tbh€dral veryfine I pegmatitos muscovite,Fe-Mn pho

2 | widfn &s qutr%andalusiB, ohedral,stender, veryfine dYftes muscovir,K-Feldspar pdsmaticgrains lofrne

wittrintheapttic $aE,K-Foldspar,mu8covile,- euMnl fineto aDdpegnalildbodi€s albite,biotilo medirm

wfthinrheaplit'rc qomz,K-f€bspar,mucovite, srbbedral fire annpegmatitiiUaies albfue,biotie interstithl

mainly in ouaft,. K-FeldsDd.alhire, sub-to qhedral fine to thecdg zone *osco"ie,ao-Oatusite, prismaticgrEins medium garn€f,apatite

ln rhoaplitic facies quar%K-Rldspq,albiq- an-to$bhedral veryfine ofsonepogmadt€s muscovir,biotiE intsstitid t()fine

comtsyrock muscovitc,biolits,quaar piscratic+uhe&al veryfino K-Fel&p,a,albie

I nainly in tle nall qrlartz,albilx K-Feldspr, firc !o zoeandaplitic&cies musc.oviio, sibhednl mediutrl of somep€gmatites Fe-ft{ni:Li phosphatss

colnttryrock muscovite,biotib,quartz, Eisnaticeohedral vayfine K-Feldspd,albiF

7 3 comtsyrcck muscovite,biotite,quaft4 pisnatic+uhedral veryfine K-Fsp,albite 8 3 courtsyrak muscovite,biotib,quafiz, pinnadccuMral veryfine K-Fsp,albitB ttgrain = r numberof lhe pegmatiterypes as in Table l; size: v€ry fine =< 6 mm; frne 6 mm to 2'5 cm; medlum= 2"5 cm to 10 cm.

simple conformable pegmatites(4); less commonly, The third type is very fine grained (<6 mm) and is the crystals are perpendiculaxto the contact with the found in the country rock, at somepegmatite - county cormtry rock in the border zones of the simple rock contacts. Crystals are euhedral and show a discordant pegmatites (6). This type of tourmaline variable pleochroism,ranglng from brown to greenish usually shows an internal concentriczonation, with a yellow in the border zones and from bluish green to variable, occasionally intense pleochroism" ranging deepblue in the inner zones. from yellow to brown-orangein the border zones,and from bluish greento blue or colorlessnear thg core of Dera CoLLesfloNAND ANALYS$ the prism" The secondtype of tourmalineis interstitial and fine The tourmalinesamples studied have been selected to very fine grained (2 cm - <6 --). It occursin the from the mostrepresentative bodies of pegmatiteof the apophyseswith aplitic and pegmatiticfacies (3) and in area,as weU as from their tourmalinizedcountry-rock the simple conformablepegmatites (4). Generally,this Tourmalinecrystals ftom at leastfour different bodies type of tourmalineshows a pleochroismranging from of each type of pegpatite have been analyzed.The yellow to brown-orange. samples were preparedby magnetic separationand 840 TIIE CANADIAN MINERAIOGIST

Frc. 2. FeO in tourmaline measuredby electron microprobe ans neutron-activationanalysis. The latter method shows the "boron shielding effect" (King et al. 1988), and the results so obtained are between24 and 49Volower than those produced with an electron microprobe.The trace- element concentrations were corrected bv the ratio O Fe6a/Fepa.

.o z hand-picking,and the separateswere examinedwith a binocular microscopeto remove contaminatedgrains. I They were ground by hand in an agate mortar and ' analyzed for major elements using a Camebax SX 50 electron microprobe. Operating conditions were: voltage 15 kV and beam current 10 nA. Wollastonite, conmdum,hematite, graftonite, albite, orthoclaseand MgO were used as internal staadards.Finally, the 24681012 concentrationsof Li and Sn was determinedby atomic FeO(wr7o) by ElectronMicroprobe absorption spectrometry(AA); concentrationsof Sc, Co,7n, As, Se,Rb, Sr, Mo, Ag, Cs, Ba, REE,Ta W,

TABLB 3. AVERAGE COMPOSMON OF TOURMALINE FROM TTIEDIFERENT TYPES OF PEGMATITE AND THEIR TOURMALINZED COIINTRY-ROCX(

'Peg.type (Tl) {r, (r3) (T4) (T4)CR (16) (T6)CR (T7)CR (TE)CR

sio2 9.72 35.47 34.67 v.99 34.98 35.45 36.17 36.t4 35,4 Tio2 0.48 0.90 0.40 0.58 0.40 0.16 0.70 0.99 0.84 41203 33.05 33.99 34.11 92A 32.47 U.t3 32:75 31.43 31.59 FeO 1224. 8.42 rL03 10.14 13.82 12.89 9.n 9.80 ll.0l MnO 0.U 0.05 0.13 0.r1 0.12 022 0,08 0.03 0.r3 MgO 1.56 3.& 2,45 3n L23 0.87 4.18 s.A1 3.90 CaO 0.O7 4.49 0.09 o.?A 0.06 0.11 0.38 0.3r a.& Na2O l,6l L,49 t.75 1.68 r.69 1.58 2.V2 22r 2.05 K20 0.05 0.04 0.M 0.05 0.04 0.03 0.05 0.08 0.05 Total 83.95 u.49 85.67 85.30 84.81 85.43 8620 86.06 85.86

481461513

Strucural fomula on the basisof 24.5 aromsof oxygeo si 5.949 5.913 5.9n, 5.841 5.985 5.973 s.n8 6.000 5.970 AI 6.675 6.683 6.753 6.739 6.549 6.719 6.381 6.148 6240 AIT 0,051 0.087 0.r7E 0.159 0.015 0.v27 0.a2 0.m0 0.030 N z 6.@0 6.000 6.000 6.000 6.m0 6.M 6.000 6.000 6.000 Al Y 4.624 0.596 0.575 0.580 0534 0.751 0.359 0.148 0.210 Ti a.62 0.113 0.050 0.u72 0.051 0.020 0.086 o.Lu 0.105 si Y 0.000 0.000 0.000 0.000 0.@0 0.000 0.000 0.0n 0.0m Fe2+ L.7s4 1.1?j 1.689 t.4t6 L.978 1.816 1.3& 1360 1.542 Mn O.V25 0.003 0.018 0.016 0.018 0.032 0.011 0.0M 0.018 Mg 0.398 0.906 0.613 0.813 0.374 0.217 1.M9 r.29 0.975 Y lotal 2"860 2396 2.946 2.8n 2.894 2.837 2.U9 2.912 2.850 Ca a.al2 0.088 0.016 0.M2 0.012 0.020 0.067 0.056 0.116 Na 0.533 0.483 0.569 0.545 0.560 0.516 0.il9 oiw 0.666 K 0.011 0.008 0.fir 0.011 0.008 0.007 0.011 0.016 o.ou X total 0.557 0.579 4.5v2 0.598 0.580 0.542 o.1n aJa w93

tpegmadte type as in Table l; N: numberof analyseqCR: toumaline ftom the cormtryrock- All Fe is calculaedasFeO. TOURMALINE IN GRANITIC PEGMATITES.SPAIN 841

Th and U were determined by neufron activation ln general, tourmaline crystals from pegmatites @,IAA). Trace-elementanalyses were performed by showhigher concenfrationsofFe and lower concentra- X-Ray AssayLabs of Don Mlls, Ontario. tions of Mg than those growing in the country rock According to King et aL (1988), the determination (Frg. 3). Tourmalinetaken from the simple discordant of trace-elementand REE concentationsin tourmaline pegmatites(6) has the highest Fe/IVIgvalue, whereas by neufton activation is hamperedby the problem of tourmalinefrom the quartz and andalusitedykes show the incident neufron-flux suppressionin the sample, the lowest Fe/Mg value (Fig. 3a). Among samplesof arising from the large neufton-capturecross section tourrnalinetaken from the countryrock @ig. 3b), those of B. This effect has been checked using the Fe found in schist near bodies of Li-rich pegmatite concentrations obtained by neutron activation and (7) have the lowest Fe/IvIgvalue, whereasthose from electron-microprobeanalyses (Frg. 2). The concentra- the host rock of the simple concordant pegmatites tions obtained by neutron activation seem to be (4) shows the lowest concentrationsof Mg and the between 24 and 49Volower than those measuredby highestconcentrations of Fe. electronmicroprobe. These deviations can be corrected The total number of cations in the Y site implies with the factor Fes1alFeNa,to permil comparisons vacancies,with a deficiency in R+ (Na++ 2C*+ + K) amongthe various samplesof tourmaline. and R2+ (Fe2* + Mg2* + Mn2+) and an excess of Tourmaline sampleswere analyzedwith an X-ray p3+ 14f3++ 48 Ti4\ Clable 3, Fig. 4). Thesemay be diffractometerusing silica as the internal standardby due to the effect of two coupled substitutions@oit scanning over the interval 5-:70" 2g using CuKcx, & Rosenberg 1977) involvinC (1) alkali defect: radiation.Unit-cell dimensionswere obtained using the (OID- + R2+= l?3++ O2-,and (2) proton loss: l?++ R2+ progrrm of Appleman& Evans(1973). = ft3+* vacancies. In general,the (R*+RlyR3* value in the tourmaline Mnw.nal CtmvflsrRY from the country rock is higher than that of the tour- maline from the pegmatiticbodies (Figs. 4a"b), which All of the tourmalinesamples analyzed belong to the reflects the higher Al contentsofthe latler. In contrast schorl-dravile series,mainly the Fe2+-richend member to the suggestionsof Foit & Rosenberg(1977), (Tables 3, 4, Fig. 3). Nevertheless,the data show substitutions involving alkali deficiency zue more compositionalvariations that correlatewith pegmatite common than those implying proton loss. Such type (Figs.3o 4, 5,6). It is alsoremarkable that in no substitutionsare partly contolled by bulk chemical casewas a differencefound betweenthe composition environmen! H2O-rich systemsfavoring alkali-defect of tourmalinefrom the core and that from the wall of substitution (Gallagher 1988). Tourmaline from the samebody of pegmatite. pegmatites(2), (3) and (4) shows a higher degreeof

TABLB 4. TRACE-ELEMENTCONCENTR.ATIONOF TOIJRMALINE FROM TIIE DIFFERENT TYPESOF PEGMATITE AND THEIR TOIJRMALINZED COWTRY.ROCK

rPes. rrpe (T1) (Tl) (T3) (T3) (T4) (T4) (T4)CR (T4)CR (T6) (T6) (T7)cR (T7)CR

LI 52 42 22 54 50 95 29 29 460 380 Sc 0.5 10.71 16564.8555.48.8 Cr 10 3 3 131 109 3 3 112 12r Co 8 12251512141920 ZD 1700 986 663 1258 lO54 1581 11?3 1n9 561 351 AE 4.4 4.4 4-4 4.4 <3.4 4.4 4.4 4.4 5 3.4 Se <5 <5 <5 <5 <5 <5 <5 <5 <5 <5 Bb 25 34 25 25 51 34 25 25 68 68 Mo 8.5 8.5 8.5 8.5 8.5 8.5 8.5 12 8.5 8.5 ag E.5 E.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 SB 12 51 20 96 15 26 32 92 Cg 1.1 0.8 3.4 8.5 3.4 13 3.4 29 c9 sf 0.4 0,4 0.4 0.4 5.8 2.7 0.4 0.4 5 4.9 Ta 1.7 <1.1 <1.7 s 1.7 <1.? 5 1.7 <1.'1 w <5 <5 <5 <5 <5 <5

CR:couty-toc.k valqsiappoLaq/Ybcrarioofchodrit+amlizedocdttali@*numb4oflheleg@dIiq Table 1. AUdata scel|tu md Sa"hwoba wted with theFe,g6/F411fctor' 842 THE CANADIAN MINERALOGIST

s0 % o0

0.0 L 0.0 L 0.8 lo 1.4 1.5 Z-1r 0.t 1.4 1.6 Fe Fe

. M (1) simpleintraEronilic pegrn. r @ (4) simple confoun. pegn, (CR) E @ (2)quare+andal. cofonnpegrn A @ (Osinplediscordottpegtn(CR) c Nl €)simptedykes ardapophysos a Nl O Li-dchdiscordaotpegm. (CR) I El (s)simpteconform.pegm. o ! (8) Sn-richdisco'daatpegrn, (CR) En (O simplediscordantp,gn Frc. 3. Plot of concentrationof Fe versasthat of Mg in tourmalinefrom someof the different types of pegmatite(a) and their tourmalinizedcountry-rock (CR) (b). Values are expressedin atomsper formula unit (numbersas in Table 1).

-N h*' to

uui 62 64 66 ae- Lo 72 62 6,4 66 6.t 7.0 72 R3+ ill+ o Ml (l)dnpleinragnrddcpegm. r ffil (4) sinpleconform. pogm.(CR) tr W (2)qudlz+mdal. confonn,pgm A @l (6)*nplediscudatpegn (CR) o E! (3)cindedy&es drd spophysss . N (DLt-ddtdbcodaatpm. (CR) I El (4) simplecofornr.pegm. o I (8)Sn-richdscordantpeen (CR) 1 @ (6) eimplediscordartpogn.

Iric. 4. (/?++ R2+)versus R* variation in tourmalinefrom someof the different types of pegmatite(a) and thet tourmalinized country-rock(CR) O). The variation can be relaJedto alkatidefect and ploton-loss substitutionsin tourmaline.The lines representcompositions between unsubstinrtedschorl-dravite and the fully substitutedend-members (proton-loss and alkali-defectend-members). Diagram modified from Manning (1982) (numben in rhe legendas in Table l), TOURMALINE IN GRAN]TIC PECIMATITES.SPAIN 843

schorl schorl

*rf"("0s0 Alsil&soAls#'e(tot)s0 Alsd&so f (1)simpleinragaoiticpep. x (4)sinplecooform-pegn(CR) tr (2) quartz.ilndal.conform. pegm (6) siryle discordantpeep.(CR) O (3) sinplEdykesand apophyses a C/)U-richdicorda-otpeCn(CR) a (4) simpleconform.pegm- a (8) Sn-richdiscordantpef.(CR) A (6) sinplediscordantpegm- O

Ftc. 5. Al-Fe(totFMg diagram (in molar proportions) for tourmaline from a) some of the pegmatite type.sand b) their tourmalinizedcountry-rock (CR), with fields after Henry & Guidotti (1985). l: Li-rich granitic pegnatites aod aplit€s, 2: Li-poor granitic rocks and associatedpegmatires and aplite,s,3: Fe-rich quartz-tourmaline (hydrothermatlyaltered granite,s),4:metapelit€s and metapsammitesso'existing with an Al-saturatingphase, 5: metapelitesand metapsammitesnot coexistingwith an Al-sannatingphase, 6: Fe-rich quartz-tourmalinerocks, calc-silicaterocts, and metapelites,7: low-Ca meta-ultamafic and Cr,V-rich metasedimentaryrocks, and 8: metacarbonatesand metapyroxenites(numbers in the legend as in Table l). proton-losssubstitutions, suggesting that its develop- in field 2 (Figs. 5, 6), which correspondsto tourmaline ment was mainly buffered by alkalis insteadof H2O. from Li-poor granitic rocks and their associatedaplites On the contraqt, tourmaline from pegrnatites(1) and andpegmatites, whereas the rest of the suiteplot in the (6) presents a greater degree of alkali-deficient metapeliteand metapsammitefields. substitutions, which would indicate a higher avail- The total concentations of. REE in all tourmaline ability of water in the system.Tourmaline from the samplesoparticularly those within the bodies of peg- country rock shows a greater degreeof alkali-defect matite, arelow Clable4). In termsof REE distribution, substitutions, likewise reflecting growth of these the tourmaline of the country rock has a moderately crystals of tourmaline in a H2O-rich environment fractionated pattern (chondrite-normalized La./Yb during metasomatismof the wallrock schist. between L4,2 ard 34.4), with a monotonic decrease Nevertheless.in calculations on the basis of %L5 from Ia to Yb, followed by an uptum to Lu; the oxygen atoms,the relative of "lkali-defect tourmaline taken from pegmatitic samples shows a substitutionis exaggerated.A way to allow for proton- highly fractionated pattern (chondrite-normalized loss substitutionis to normalizecation contentsto 6Si, IalYb between 0.6 and 3.9), with a scatter of the but then the degree of proton-loss substitution is values. exaggerated.Normalizations based on 24.5 atoms of The tourmaline from pegmatitic samples is also oxygen and to 6 atoms of Si represent extreme poorerin other fraceelementso so that tourmalinefrom positions not found in natural tourmalines(Ga[agher the country rock showshigher contentsin Cr, Rb, IIf, 1988).On the other han4 the content of ferric iron in Th and U Clable 4). It is also notable that the the tourmaline would not change the disftibution in tourmalinein the country rock adjacentto the Li-rich Figure 4, as according to Henry & Guidotti (1985), pegmatites (7) shows a relative enrichment in Li where tourmaline compositions plot above the line (38H60 ppm), Rb (68 ppm) and Cs (29-39 ppm). schorHravite in the Al-Fe-Mg diagram (Fig. 5), the Most of the tourmalineprisms are zonedconcentri- amountof Fe$ is very low. cally aboutthe c axis. This zoning and the shapeof the In the Al-Fe-Mg and Ca-Fe-Mg diagrams(Henry crystals reflect the easeof growth in the c direction & Guidotti 1985),most of the tourmalinesamples plot (Iolliff et al. 1986).The zoning is cbromaticand com- 8M TTIE CANADIAN MINERALOGIST

a (1) simpleintsaganftic pogm. lI (2) quare+mdal @nfom pegm C (3) simple dyks 8d apophys€s : (4) sinpls conlom.psgm, (Ct) I (a) simplo conbm. pegm. A (O dmple drscordantpegm" A (O simple discordantp€gn-(A) a CDU-rich dicodantpess. ((}) O (8) Sn-rich discordantpep. ((b)

\2s a

\25 b

Mg

Ftc. 6. Ca-Fe(tot)-Mg (in molar proportions)for tourmaline from a) someof the peg@aritetypes and b) their tourmalinized country-rock(CR), with fields after Henry & Guidotti (1985). 1: Li-rich granitic pegmatitesand aplites, 2: Li-poor granitoids and associatedpegmatites and aplites, 3: Ca-rich metapelites,metapsammites, and calc-silicate rocks, 4: Ca-poor metapelites,metapsammites, and quartz-tourmalinerocks, 5: metacarbonates,and 6: meta-ultramaficrocks (numbersin the legendasinTable1).

positional,with a slight tendencyto enrichmentin Mg Drscussron in the core relative to the rim, observedin all groups (Frg. 7). A relation betweencomposition and color has The observedsom.positional variations indicate the not beenestablished, as there are zoneswith the same importanceof coupled substitutions(alkali-defect and color and different composition,whereas crystals with proton-losssubstitutions), which are more extensivein similar contents show different colorations. These lsumaline from pegmatites than from the country differencescould reflect small variations in the ratio rocks @g. 4). This variation could be explainedby the Fe2+/Iie3+, greateravailability of Fe and Mg in the county-rock Finally, results of the unit-cell determinationsare envtonment. Manning (1982) found that the extent of listed in Table 5. Values of a versw c are plotted in such coupled substitutions becomes greater with Figure 8. The tourmaline samples plot near the decreasingtemperature, i.e., ldrth an increasein the schorl-dravitereference line @onnay&Barton 7972), degree of fractionation. However, all the tourmaline near the schorl end-member,in agreementwith the samplestaken from pegmatitebodies show a similar chemicaldata. extent of these coupled substitutionsGig. 4a); their TOT]RMALINEIN GRANITIC,PEGMATITES.SPAIN 845

6.50

E x 6 o R t 6.00 3 3

Es.:o I EZ@

? tt< q P Erso E

1.25 +st l.@ 1.00 +Al(bt) +Tl +F9 0J0 0.9 +Mg 035 +Ca 0.25 +Na 0.00 0.m

Ftc. 7. Detailed compositionalvariation of zoned crystals of tourmaline occurring in or near a) enclosedpegnatits (1), b) apophyseswithin aplitic andpegmatitic facies (3), and c) simple discordantpegmatite (6) (CR: country rock).

extentis thus not a usefirl tool to monitor differencesin (4) showsa lower contentin Fe; finally, the richest in degree of fractionation. Moreover, the tourmaline Mg is that associatedto the quartz-andalusitedykes occurringin the county rock near simple conformable Q). At a particular set ofpressure-temperaturecondi- pegmatiles(4) showsa gre,,tetexlent of suchsubstitu- tions, the compositional evolution of the pegmatite- tions relative to that in the schists near the simple forrning melt-fluid system is closely related to the discordantpegmatite$ (6), the Li-rich pegmatites(7), stability of a given compositionof tourmaline. Thus, andthe Sn-richdykes (8) (Fie. 4b). Thusodifferences in basedon ionic size and charge(fauson 1965),hthium- the conditions of crystallization, such as the rate of bearing tourmaline would be expected to be more crystallization and in the composition of the original stable at lower temperaturesthan Fe-rich tourmaline, melts, also could affect the exlent of these substi- which in turn will be more stable than Mg-rich tutions. tourmaline. Previous investigators (Neiva 1974, Tourmaline in the pegmatiteshas, in general, a Manning 1982,Jolliff et al. 1986) agreewith the fact higher Fe/IMgvalue than that found in the county rock that tourmaline associatedto the earliest stages of (Fig. 3). Among the tourmaline samples from differentiationis richer in Mg than that crystalizing in pegmatites@ig. 3a), the richest in Fe and the poorest the later stages.In addition, zonedcrystals in our suite in Mg occursin g[e simFle discordantpegmatit€s (6), tend to show a rim emiched in Fe relative to Mg, followed by the intragranitic pegmatites(1) and the compaxedto the core. It thus seemsthat the sequence apophyses with aplitic and pegmatitic facies (3). obtained for the Fe/I4g value in tourmaline from Tourmaline from the simple comformablepegmatites pegmatitescould be used as a tool to establish the 86 TIIE CANADIAN MINERAL@IST

TABLE 5. IJNIT.CFI I - DIMENSIONS OF sequenceof crystallization for the pegmatitebodies. REPRESENTATIVE TOURMALINE SAMPLES FROM According to this ratio, the most evolved tourmaline- T}ilE PEGMATTTESOFTIIEFREGENEDA AREA AND bearing pegmatiteswould be 66s simple discordant THEIR TOURMALINZED COI]NTRY.ROCK pegmatites (6), followed by tlte intragranitic pegmatites(l) and the apophyseswith aplitic and peg- matitic facies (3). Finally, d[e simple comform.able peg.* c(A) Y(43) cla Ttpo a(A) pegmatites (4) and the quartz-andalusitedykes (2) G1) rs,992Q) 7,166(l) rs87A$) 0,44E seemto be the leastevolved pegmatites. This sequence Gl) 15,957(4) 7,156(3) 1578,2(9) 0,449 agreeswith that obtainedfrom the K/Rb ratio in micas (r2) 15,950(1) 7,r69(1) 1s79,7(3) 0,449 and K-feldspar from these pegmatites (Roda et al. (r3) 7,154(0) ts78,3(2) 0,448 15,960(1) In the pegmatitesofthe Fregenedaarea, there- Cr3) 15,956(2) 7,L57(r) 1578,0(4) 0,449 1993). G3) 15,957(1) 7,r52(t) Ls77,3(2'., 0,448 fore, tourmaline associatedwith the early stagesof G3) 15,961(r) 7,r7o(2) 1582,2(5) 0.449 crystallizationis richer in Mg than that growing later, (I3) 15,971(1) 7,153(1) 1580,4(2) 0,448 which is richer in Fe. CT4) r5,959(r) 7,r58(0) 1s79,1(2) o,449 (r4) rs,954(1) 7,r5r(1) r5?6,6(3) 0,448 Concentrationsof REE are uniformly lower for CT4) 15,959(1) ?,15s(0) 1578,3(2) a.448 tourmalinein thepegmatitescomparedto tourmaline in (r4) 15,968(1) ?,r56(1) 1580,3(4) 0,448 the country rocks. This rnay mean that the .REE (r4) 15,954(1) ?,1s2(0) t576,6(2) 0,44E abundancesand disfributions in tourmaline are pre- CI4) 158s3(1) 7,178(r) rs82'2Q) 0,450 (r4) r5.958(r) 7,161(1) Ls79,4(3) 0,M9 dominantly confolled by the parageneticconditions, 04xcR) rJ,967(1) 7,rs3(0) L579,5(2) 0,448 that is. the REE contentin tourmalinereflects the REE CI?X(R') 15,955(3) 7.r7s(2) 1582,0(6) 0,450 conlent of the medium where the tourrnaline crystal- GD(CR) rs,976(2' 7,t75(2) 1586,r(5) 0,M9 lized (Jolliff et al. 1987,King e/ aL 1988).Therefore, crO(cR) 15,958(2) 7,r7s(r) 1582,5(4) 0,450 (nxcn) 7,167(2) 1s?9,8(7) o,M9 the high concentrationsof REE n tourmalinefrom the WXCR) ?,t52(L) 0,448 country roctrs may be inherited from the schists in which they grew. This inheriunce could cause the (* numbemof pegmatitc qpes as in Table I : cotulEy similarity in shapebetween the patternsfor tourmaline rock) . of the county rock and those of the metasedimentary rocks of the Schist-MetagraywackeComplex. Tourrnalinefrom the country rock near the Li-rich pegmatitesshows evidence of enricbmentin Li, Rb and Cs, as a result of the interactionof a fluid derivedfrom

l9(., z.l

7.

elbaite 15.780 15.820 15.8@ 15.90015.940 15.980 16.02016.060 a(A)"

Ftc. 8. Unit-cell dimensionsof tourmalinesamples representative of the different types of pegmatite and their tourmalinized country-rock Referencelines from Donnay & Barton (1972),modified from Epprecht(1953). TOTJRMALINEIN GRAMTIC PECiMATITES.SPAIN 847

the crystallizing melt and the country rock. (1982): Estudio del metamorfismo existente en Tourmalinizationof the schistsis strongonly in a halo torno al granito de Lumbrales (Salamanca). .Srvdla gic -20. approximately 20 cm vdde around these pegmatite Geolo a Salmantic e ns ia 17, 7 bodies; beyond 50 cm, tourmalinization is not DoNNA! G. & BARroN,R., Jn. (1972): Refinementof the developed. crystal structureof elbaite and the mechanismof tourma- Finally, the tourmalinecompositions plot in the field line solid solution. TschermalcsMineral. Petrogr.Mitt. lE, of Li-poor granitic and associated rocks, on the n3-286. Al-Fe-Mg and Ca-Fe-Mg diagrams. Note that the pegmatitesthat contain tourmaline are spatially EppREctrr,W. (1953): Die Gifierkonstantender Tirmaline. relatedto the Li-rich Lumbralesgranite, which contain SchweizMineraL Petrogr. Mitt. 33, 48l-505. from 170to 230 ppm of U (GarcfaGa:z6n & Locutura 1981). This apparentconffadiction suggeststhat, on Fon, F.F., JR. & Ross{BRG,P.E. (1977): Coupledsubstitu- one hand, the composition of tourmaline may be tions in the tourmaline group. Contrib. Mincral. Petrol, influenced by the chemical environmenq achieving 62.109-tn. mixed peffogeneticaffinities, an4 on the other hand, V. (1988): Coupled substitutions in the geochemicalconditions existing during the forma- GALLAcIIER., schorl-dravitetourmaline: new evidencefrom SE Ireland. granite pegmatites tion of the and its assosiated are Mineral. Mag. 52, 637-650. complexand not completelyunderstood. GARcfAGARZON, J. & LocuruR4 J. (1981): Dataci6npor el ACKNowllDGg\dENTs m6todoRb-Sr de los granitosde Lumbrales-Sobradilloy -PuertoSeguro. Bol. Geol.y Min- dz Esp. This work is part of a Ph.D. thesis,which has been 9L1,68-72. mainly supported by a grant from the Education, Universities and Investigation Deparment of the Gencfa Lus, A.I.(1991): Caracterizaci6ngeoqufmica de los Basque Country Govemmenl. We thank Dr. Brad leucogranitosde Lumbrales:influencia de la deformaci6n Jolliff for his suggestions,which have improved the en el modelo magmdtico.Definici6n de dos tendenciase procesospetrogendticos. Esa Geol, 4fl, manuscript. We also express our gratitude to Drs. implicaci6n en los t3-31. Robert F. Martin and J.T. O'Connor for their helpful criticism. GoNzAroConneq J.C. (1981): Estudio geol6gicodel campo filoniano de (Salamanca). Tesis Licenc., Rmmsvcrs Univ. SalamancaSalamanca Spain.

Atnws, L.H., PtrrsoN,W.H. & Kranns,M.M. (1952): Ilruncwr,nr, R.H., Garmar, K., GAu.AcIrR" V. & Bercn, Associationof rubidiumand potassium and their abun- J.H. (1994): Tourmaline in the central Swedishore dis- dance in igneous rocks and meteorites.Geochim, trict- Mbrcral. Deposita 29, 189-205. Co smo chim. Ac ta 2, 229-242. Ilqvnv, D.J. & Gutooru, C.V. (1985): Tourmaline as a Appr,s\4AN,D.E. & EvANs,H.T., Jn. (1973): Iob 9214; petrogenetic indicator mineral: an example from the indexingand least-squares refinement of powderdiftac- staurolite-grademetapelites of NW Maine. Am- Mineral. tion data U.S.Geol. Suw., Comput. Contrib.20 QVZ/S 70, l-15. Doc PB2.16IE$. Jorm, 8.L., Pem

Knvc, R.W., KERRTCH,R.W. & Deooan, R. (1988): REE Pnarxo, F. & Smrms, R.H. (1992):The FeO(FeO + MgO) distributionsin tourmaline:an INAA techniqueinvolving ratio of tourmaline:a useft.rlindicator of spatialvariations pretreatment by B volatilization, Am" Mineral. 73, in granite-related hydrothermal mineral deposits. 424431. Geochsn.Explor. 42, 37l-381.

I-6pw.Htze, M., Canmcrno,A. & Goxzerc, J.C. (1982): RoDA, E. & PEseuERA,A. (1995): Micas of the Estudio geol6gico del campofiloniano de La Fregeneda muscovite-lepidolite series from the Fregeneda peg- (Salamanca).Sndia GeolngicaSalmanticensia 17, 89-98. matites(Salamanc1 Spain). Mincral. Petrol. (in press).

& Canmcrno, M.A. (1988): El pluronismo & VH.Asco,F. (1991):The pegmatitesof Herclnico de la penillanurasalmantino-zamorana (centro- the Fregeneda area, Salamanca, Spain. /z Source, oestede Espa<0241>a):visi6n de conjuntoetr el contexto Transport and Deposition of Metals (M. Pagel & geol6gico regional. ^Iz Geologla de los Granitoides y J.L. l,eroy, eds.). Balkema RotterdanqThe Netherlands Rocas Asociadas del Macizo Hespdrico. EdiL Rueda (80r-806). Madrid,Spain (53-68). & -(1993): Mica andK-feldspar & ManrfNsz CATALAN,J.R. (1988): Slntesis as indicatorsof pegmatiteevolution in the Fregenedaarea, estructural de los granitoides Hercfnicos del macizo Salamanca, Spain. /n Cunent Research in Geology Hesp6rico. In Geologfa de los Granitoides y Rocas Applied to Ore Deposits @. Fenoll Hach-Alf, J. Torres- Asociadasdel Macizo Hespdrico.Erdit. Ruedq Madri{ Ruiz & F. Gervilla, eds.).l,a Guioconda Granada,Spain Spain(195-210). (653-6s6).

Marwnc, D.A.C. (1982): Chemical and morphological Snnanm, C.K., Papncq J.J., Snaox, S.B., Law, J.C. & variationin tourmalinesfrom the Hub Kapongbatholith of CmIsrIAN, R.P. (1984): Peematit€/walhockinteractions, peninsularThailand, Mineral. Mag. 45, 139-147. Black Hills, South Dakota: progressiveboron metaso- matism adjacent to the Tip Top peguatite. Geochim, Menrh{ez FrrurAr.Dsz, F.J. (1974): Estadio del drea Cosrutchim.Acta 4E,2563-2579. mznmlfica y gran{tica de los Anibes del Dwro (Prov. de Salamancay hmora). Ph.D. thesis,Univ. Salamanc4 TAUsoN,L.V. (1965): Factorsin the distribution ofthe trace Salamanc4Spain. elements during the crystallization of mapas. Phys. Chen.Eanh6,2L5-249. Mrctrarrors, K. & Kessolr-FonRNARAKr, A. (1994): Tourmaline concentrations in migmatitic metase- dimentary rocks of the Riziana and Kolchiko areas in Macedonia,northern Greece. Eur. J. Mineral.6,557-569.

Newe, A.M.R. (1974): Geochemistryof tourmaline (schor- Iite) from grulites, aplites and pegmatitesfrom northem Received July 5, 1994, revised manuscript accepted Portugal.Geochim, Cosmochim. Acta 38, L307-13L7. Janunry 11, 1995.