835
The CanadianM irc ralogist
Vol. 33,pp. 835-848(1995)
TOURMALINE
IN GRANITICPEGMATITES
ROCKS,
AND THEIRGOUNTRY
FREGENEDA
AREA,SALAMANCA.SPAIN
ENCARNACI6N ROpa, ALFONSO PESQIIERA ANDFRANCISCOVELASCO
y Petrolagfa,Universidad
Departamento
d.eMineralagta
Aptdo,644,848080,Bilbao,Spain
delPatsVascolEHU,
ABSTRACT
In the northwestempart of the province of Salamanca(Spain),many Li-, Sn-bearingand barrengranitic pegmatitesoccur.
Thesebodiesdisplay 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 tourmalinebelongsto the schorl-dravitesolid-solutionseries.Tourmalineshowstexfiral and
conpositional variations in relation with pegmatitetype. Subhedralto euhedralprismatic, very fine- to medium-grained
(<6 mm - 10 cn), zonedgrains are most common.In the country rock, tourmalineapp€anas prismatic-euhedral,very finegrained(<6 mm) crystals.Their Fe/lVIgvalue cha:rgesconsiderablyamongthe different pegmatitetype.s,providing insigbt into
the degreeof evolutionof the associatedpegmarites:thoserichestin Fe andpoorestin Mg areassociatedvrith the mostevolved
bodies.Tourmalinefrom the countryrocks showscompositionalcharacteristicsinheritedfrom 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-ouestde la provincede Salamanca,en Espagne,setrouventplu$ieursmassifsde granit€p€gmatitique,
soit lithinifdres, stannifbresou st6riles.Cesdiff6rentsfacidssontdispos6sd'unefagonzonairei partir du granitede Lumbrales
vers le nord et monhent un degr6d'6volutionprogressivementplus avanc6en s'6loignantdu contact.La tourmaline est un
min6ral accessoiredansles pegmatitesst6riles,de m6mequedansles rochesencaissantes.
Densles deuxcas,la tourmalinefait
partie de la s6rieschorl-dravite.l,a tourmalinemontre desdiff6rencestexturaleset chimiquesselonle facibsde la pegmatite.
lrs prismessubidiomorphesi 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 valeurFe/Mg varie consid6rablement
d'un facibsi I'autre,de fagonh indiquerle degr6d'6volutionde la pegmatite
h6te. l,a tourmalinela plus riche en Fe et la plus pauwe en Mg estassocideavecla pegmatitela plus 6volude,Ia composition
de la tourmaline des roches h6tes reprend les traits compositionnelsde celles-ci, par exemple une ressemblancedans
I'enrichissement
relatif desterresrareset une teneur6lev6een Cr, I{f, Th et U.
(Iraduit par la R6daction)
Mots-cl6s:toummline,pegmatitegranitique,schorl-dravite,Fregeneda"
Espagne.
INTRoDUciloN
In the Fregenedaaxeaof Spain, different types of
granitic pegmatitescan be establishedon the grounds
of mineralogical and geological criteria and spatial
disnibution arcundthe Lumbralesgranite(Fig. 1). The
most commontype correspondsto simple pegmatites
without internal zonation. Zoned, Li-bearing
pegmatitesalso are relatively coulmon, as are pegmatitic veins containing quartz, muscovite,feldspars,
and cassiterite.Tourmalineappearsas an accessoryor
major mineral in many of thesepegmatites,and it is
also common in the country rock, near the contacts
with pegmatitebodies.
The compositionof the tourrnalinereflects the bulk
chemisty of the systemin which it forms, and some
studies have establishedits value as a petrogenetic
indicator(e.9.,Sheareret al.1984, Henry & Guidotti
1985, Jolliff et al. L986, Kassoli-Foumaraki 1990,
Pirajno & Smithies 1992, Kassoli-Fournaraki&
Michailidis 1994. Michailidis & Kassoli-Foummaki
1994, Hellingwetf et al. 1994). In this study, petrographicandchemicaldataon representativesamplesof
tourmaline selected from the various groups of
pegmatitesin the Fregenedaareaand their extensively
tourmalinized county-rock are given. The chemical
yariationsare discussedin order to determinewhethfr
thesedifferent types of pegmatitel) are relatedby a
836
TI{E CANADIAN MINERALOGIST
PORTUGAL
N
A
0
Duero !$1{
1Kn
TT
(f) a
(2) tr
(3) O
(4) I
(9 A
(O
(4 a
(8) o
slnxpleintraCraniticpep.
qpa&+afilalusitecodomable dykes
simpledyke.sandapophyses
sinplscodomablepoeltr
K-fetdspardiscodandykes
siEplediscorda$psgpr,
U-beadngdtscorderpeg4.
Sn-bearing<liscordantpegs.
+ + + ++ + + + + + + + + + + + + .
+++*++++++++++++++'
+++ti++++++++++++++'
+{'+++++++++++++++
+#+++++++++++++++.
eiinit'e'I i I:
if, iSau'cdtlle
+ + + + ++ .
+ + ++ + + + +
+++++++++++++*
++++++++++++++,
+++++++++++++++'
+++++++++++++++.
+++++++++++++.
ts+++++++++++++.
++++++++++|\+++.
++{L+A+
+++
+
++
Ar
^dp***
+++++++
+++.f+++++
+++++++++++
+++++++++
+++++++++++
+ + + + * + + + ++ +
Fn
++++++++++++++++++++
+ . f+ + * + + + + f + + + + + + + + + + + + .
+++++
++++++++++++++++++++++.
.+++++
+ + + + + * +x t+ + + + + a\' \s|.l.irlt + + + + + + + + + + + + + + + + + + + + + + '
V + + + + + + + :F++ + + + + +\4l + + + + + + + + + + + + + + + + + + + + + + + + + +'
+.7++
+ + +a+t"+-l
*+++++++
++++++
++
ii IIIIIIii :
crl'lte,:
t I i+ I+ i+I+i+I+i+l+I+I+I+i +I +I +I +i +l!,rrlPlq
+++r++++++++++++++++++++'
B,LBiotiteisograd
E
ar. Andalusileisograd .o
sJ. Si[imanite isograd
Schist-Metagraywacke-Complex
Fracturecontainingquartzsegregations
Ftc. 1. Distribution ofthe pegmatitegroupsrecognizedin the Fregenedaarea The pegmatitetypesarelabeledas in Table l.
commonpath of fractionation,and2) arerelatedto the
nearbyLumbralesgranite.
Gsot,octcAr,Srrrwc
The pegmatitesof the Fregenedaareaappearin the
HespericMassif, in tbe westernpart of a trarrowmetamorphicbelt, with an E-W strike.This belt, situatedin
northwesternSalamanca,is borderedby the Lumbrales
pluton to the south,and by the Saucellepluton to the
northeast(Fig. 1). Both granites and pegmatitesare
intrusive into pre-Ordovician metasedimentsof the
Schist-MetagraywackeComplex. In this area, this
Complex comprises a sequenceof quartzites,graywackes,schistsand pelites, with abundantfhin hysrs
of calcsilicate. These materials have undergonetwo
main phasesof Hercyniandeformation,with the later
event of lower intensity (Martfnez Fem{adez L974).
The earlierphasegaverise to a regionalmetamorphism
that in the Fregenedaarea shows a distribution of
isograds parallel to the Lumbrales granite, locally
lsnshing the sillimanite zone,whereasthe biotite zone
is the most extensive (Frg. 1). The regional metamorphism,of mediumfe high grade,and interrnediate
pressures,determinedby the sillimanite - K-feldspar
isograd, led to incipient partial melting of the metasedimentary units at approximately 650'C and
3.5 kbars, coinciding, in general,with the appearance
of cordierite- K-feldsparin the migmatitic leucosome
(GarciaLuis 1991). The episodeof regional metamorphism precededthe secondphase of Hercynian
deformation(Carnicero1982),and it is superimposed
by a contact metamorphismthat may be due to the
presenceof a hidden granitic pluton, which has been
detectedat depthby clrilling Q.6pezPlazaet al. L982).
One of the mdn characteristicsof this area is the
greatdiversity of granitesthat outcropthere.The most
common group is that of the peraluminousleucogranites,to which the Lumbralesand Saucelleplutons
belong @g. 1). The former is part of the MedaPenedono-Lumbralesgranitic complex (Bea et al.
1988), and consists of a parautochthonous,heterogeneous,fine- to medium-grainedtwo-mica granite
(Carnicero1981).With regardto the Hercyniandeformation, this pluton is included in the group of
syntectonicmassifsthat havebeen deformedduring a
third phaseof HercyniandeformationQ-6pezPlaza&
Carnicero 1988, I-6pez Plaza & Martlnez Catal{r
1988),with a Rb-Sr isochron age of 284 t 8 Ma
(Garcia Gan6n & Locutura 1981). In spite of its
837
TOURMALINE IN GRANITIC PEGMATITES.SPAIN
(t)
2
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o *'E o F.B.,
THE CANADIAN MINERALOGIST
evident petrological continuity, the Lumbralespluton
showsa cleartectoniccontol westward,whereasto the
east the deformationdecreases,and the emplacement
ofthe graniteseemsto havebeenfree ofexternal sffess
(Gonzalo Conal 1981, L6pez Plaza et al. 1982).
Another characteristicof this body is the presenceof a
migmatitic facies in the border as well as in the inner
zones,mainly to the eastofthe Fregenedaarea.As is
the casefor the Lumbralespluton, the Saucellepluton
is a peraluminous,fine-grained,two-mica granite,and
it belongsto the group of syntectonicmassifsthat were
deformedduring the third phaseof Hercynian deformation (L6pez Plaza & Camicero 1988).With regard
to their degree of rare-element enrichmsfi, ftsy
contain170-230ppm Li, 343 ppm Rb and218 ppm Ba
(Garcfa Gam6n & Locutura 1981, Bea & Ugidos
1976).The high contentsin Li andRb arenoreworthy,
as are the low contentsof Ba in both series.The K/Rb
ratioalsois low, with valuesbelow 160@ea1976,Bea
& Ugidos 1976), characteristicof granitic pegmatite
andhigtrly differentiatedgranites(Ahrenset al. L952).
PecMArnETVpEs
On the basisof mineralogy,morphology,and internal structure, several groups of granitic pegmatites
have beenrecognized.Thesegroups display a degree
of differentiation that increases awav from the
Lumbrales granite. With increasing distance from
the contact the groupsare @oda et al. 1991,Roda &
Pesquera,
inpress)(Fig. I, Table 1):
(1) Infagranitic bodies of pegmatite consisting of
quartz, K-feldspar (-icrocline and orthoclase),
muscovite,albite and schorl;thesebodiesare relatively abundantin the borderzonesofLumbrales pluton.
(2) Dykes composedmainly of quartz, andalusiteand
minor muscovite, schorl and K-feldspar (microcline
and orthoclase),of pegmatitic grain-size. They are
concordantto the coun!ry-rockfabric, showingrelated
deformation,witl a boudinagesfiucture.Thesebodies
appearin the andalusite--cordierite
zone, close to the
Lumbralesgranite.
(3) Dykes and apophyses showing aplitic and
pegmatitic facies, consisting of quartz, K-feldspar
(microcline and orthoclase), muscovite sad minel
albite, schorl, and biotite. Their grain size changes
abruptlyfrom an aplitic to a pegmatiticfacies,andtheir
shapesvary geatly. Thesebodies are localed to the
southeastof the area studie4 near the Lumbrates
granite,associatedwith the sillimanite, andalusite,and
biotite zones.
(4) Conformablebodiesof pegmatiteof narrow width
(<1.5 m), locally showing internal zoning. They are
composedmainly of quartz, muscovite, K-feldspar
(microcline and orthoclase),schorl, albite, and minor
andalusite,chlorite, game! and biotite. Host rocks
commonly display strong tourmalinization near
the contacts.These bodies are located close to ttre
Lumbrales granite. They are associaledmainly with
the andalusitezone and to a lesser extent with the
sillimanite andbiotite zones.
(5) Pegmatitebo'diesmainly composedof K-feldspar
(microcline and orthoclase).Other phasesthat may be
present are quartz, muscovite and pyrile. They are
discordant to the country rock, appearingnear the
contact with the Lumbrales granite, associatedwith
the biotite zone.
(6) Discordantbodiesof pegmatitethal in somecases,
show a layered internal structure. They consist of
quartz, K-feldspar (microcline and orthoclase),
muscovile,and albiie. In the bodies farthestfrom the
Lumbralesgranite, amblgonite may appear,whereas
close to the granite, phosphatesof Fe-Mn t Li are
common, as well as tourmaline as an accessory
mineral. Moreover.the host rock can show a variable
degreeof tourmalinization.Situatedin an areabetween
I and4 km to the north of the Lumbralespluton, group
6 is the most abundant.The host rocks exhibit lowgrade regional metamorphism(biotite and cblorite
zones).
(7) Discordant bodies of Li-mica-bearing pegmatite.
Thesebodiesusually displaya zonedinternalstructure.
They are composedof quartz,Li-bearing mica, albfte,
K-feldspar(microcline and orthoclase),muscoviteand
minor amblygonite, spodumene,cassiterite, apatite,
and columbite-tantalite. f6urmaline has not been
found in thesepegmatites,althoughtourmalinizationis
variably developedaroundthepegmatites.Thesedykes
crop out along a narow ban4 4 6 km north of the
Lumbrales granite. As is the case with the previous
ca0egory,thesebodiesof pegmatiteareassociatedwith
the biotile aud chlorite zones.
(8) Bodiesof pegmatiteconsist"rg of quartzand minor
fine-grained muscovite, albite, microcline and
cassiterile. Their county rock exhibits a variable
degreeof tourmalinization;as in the previous group,
tourmalinehas not beenfound as a constifirentofthe
pegmatites. These dykes locally show internal
zonation, being folded, with the axial plane neady
horizontal.They appearin the norflem zoneofthe area
studie4 being cut by some bodies of the previous
category. These dykes are only associa0edwith the
chlorite zone.
PsrRocRAPnY
Textural and parageneticdifferences among the
tourmaline samples from the various fypes of
pegmatilehavebeenobserved(Table 2). Threemodes
of occurrencecan be established.The first one is a
medium to very fine-grained (5 cm - <6 -m),
prismatic tourmaline, that appears homogeneously
distributed in the intragranitic pegmatites(1), in the
quartz-andalusitedykes(2) nd in the apophyseswith
aplitic and pegmatiticfacies (3). Commonly,this type
of tourmalinegrowswith quarczin the corezonein the
839
SPAIN
TOI]RMALINE
IN GRANITICPEGMATITES.
TABLE 2. TOURMALINE DISTRIBUTION IN TIIE FRECENEDAPEGMATTTES
AND TI]EIR TOTIRMAUNTZEDCOI.INTRY-ROCI(
TEXTURE GRAIN SIZE'I
PEGM.TOURMAL.OCCURRENCE MINBNAL ASSOCIATION
TYPE'
TYPE
1
mainly in the
intEmediate
z&e
qu8%K-Feldspfr,
albite, muscovie
sub-oeuhedral
prismatic, aned
gains
fiIEto
medium
quar%K-Ibldspar,albib'
muscovite,Fe-Mn pho
$tbh€dral
veryfine
qutr%andalusiB,
muscovir,K-Feldspar
ohedral,stender,
pdsmaticgrains
veryfine
lofrne
I
withln the
pegmatitos
I
2
widfn &s
dYftes
|
wittrintheapttic
$aE,K-Foldspar,mu8covile,
albite,biotilo
aDdpegnalildbodi€s
qomz,K-f€bspar,mucovite,
wfthinrheaplit'rc
albfue,biotie
annpegmatitiiUaies
mainly in
thecdg zone
ln rhoaplitic facies
ofsonepogmadt€s
comtsyrock
I
nainly in tle nall
zoeandaplitic&cies
of somep€gmatites
euMnl
srbbedral
interstithl
fineto
medirm
fire
ouaft,. K-FeldsDd.alhire, sub-to qhedral
*osco"ie,ao-Oatusite, prismaticgrEins
garn€f,apatite
fine to
medium
quar%K-Rldspq,albiq
muscovir,biotiE
veryfine
t()fine
an-to$bhedral
intsstitid
muscovitc,biolits,quaar piscratic+uhe&al veryfino
K-Fel&p,a,albie
qrlartz,albilx K-Feldspr,
musc.oviio,
Fe-ft{ni:Li phosphatss
sibhednl
firc !o
mediutrl
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
K-Fsp,albitB
veryfine
r numberof lhe pegmatiterypesasin Table l; ttgrain size:v€ry fine =< 6 mm; frne= 6 mm to 2'5 cm;
medlum= 2"5 cm to 10 cm.
simple conformablepegmatites(4); less commonly,
the crystals are perpendiculaxto the contactwith the
cormtry rock in the border zones of the simple
discordant pegmatites (6). This type of tourmaline
usually showsan internal concentriczonation,with a
variable, occasionally intense pleochroism" ranging
from yellow to brown-orangein the border zones,and
from bluish greento blue or colorlessnearthg core of
the prism"
The secondtype of tourmalineis interstitial andfine
to very fine grained(2 cm - <6 --). It occursin the
apophyseswith aplitic andpegmatiticfacies(3) andin
the simpleconformablepegmatites(4). Generally,this
type of tourmalineshowsa pleochroismranging from
yellow to brown-orange.
The third type is very fine grained(<6 mm) and is
found in the countryrock, at somepegmatite- county
rock contacts. Crystals are euhedral and show a
variablepleochroism,ranglngfrom brown to greenish
yellow in the border zonesand from bluish green to
deepblue in the inner zones.
Dera CoLLesfloNANDANALYS$
The tourmalinesamplesstudiedhave beenselected
from the mostrepresentativebodiesof pegmatiteof the
area,as weUas from their tourmalinizedcountry-rock
Tourmalinecrystalsftom at leastfour different bodies
of each type of pegpatite have been analyzed.The
sampleswere preparedby magnetic separationand
840
TIIE CANADIAN
MINERAIOGIST
Frc. 2. FeO in tourmaline measuredby electronmicroprobe
ansneutron-activationanalysis.The latter methodshows
the "boron shielding effect" (King et al. 1988), and the
results so obtainedare between24 and 49Volower than
thoseproducedwith an electron microprobe.The traceelement concentrations were corrected bv the ratio
Fe6a/Fepa.
O
.o
z
hand-picking,and the separateswere examinedwith a
binocular microscopeto remove contaminatedgrains.
They were ground by hand in an agate mortar and
analyzed for major elementsusing a Camebax SX
50 electron microprobe. Operating conditions were:
voltage 15 kV and beamcurrent 10 nA. Wollastonite,
conmdum,hematite,graftonite, albite, orthoclaseand
MgO were used as internal staadards.Finally, the
concentrationsof Li and Sn was determinedby atomic
absorptionspectrometry(AA); concentrationsof Sc,
Co,7n, As, Se,Rb, Sr, Mo, Ag, Cs, Ba, REE,Ta W,
I'
24681012
FeO(wr7o)by ElectronMicroprobe
TABLB 3. AVERAGE COMPOSMON OF TOURMALINE FROM TTIEDIFERENT
TYPESOF PEGMATITE AND THEIR TOURMALINZED COIINTRY-ROCX(
'Peg.type
(Tl)
{r,
(r3)
(T4)
(T4)CR
(16)
sio2
Tio2
41203
FeO
MnO
MgO
CaO
Na2O
K20
Total
9.72
0.48
33.05
1224.
0.U
1.56
0.O7
l,6l
0.05
83.95
35.47
0.90
33.99
8.42
0.05
3.&
4.49
L,49
0.04
u.49
34.67
0.40
34.11
rL03
0.13
2,45
0.09
t.75
0.M
85.67
v.99
0.58
92A
10.14
0.r1
3n
o.?A
1.68
0.05
85.30
34.98
0.40
32.47
13.82
0.12
L23
0.06
r.69
0.04
84.81
35.45
0.16
U.t3
12.89
022
0.87
0.11
1.58
0.03
85.43
(T6)CR (T7)CR (TE)CR
36.17
0.70
32:75
9.n
0,08
4.18
0.38
2.V2
0.05
8620
36.t4
0.99
31.43
9.80
0.03
s.A1
0.3r
22r
0.08
86.06
35,4
0.84
31.59
ll.0l
0.r3
3.90
a.&
2.05
0.05
85.86
481461513
Strucural fomula on thebasisof 24.5aromsof oxygeo
si
AI
AIT
5.949
6.675
0,051
5.913
6.683
0.087
5.9n, 5.841 5.985 5.973
6.753 6.739 6.549 6.719
0.r7E 0.159 0.015 0.v27
N z
6.@0
6.000
6.000
6.000
Al Y
Ti
si Y
Fe2+
Mn
Mg
Y lotal
4.624
a.62
0.000
L.7s4
O.V25
0.398
2"860
0.596
0.113
0.000
1.1?j
0.003
0.906
2396
0.575
0.050
0.000
1.689
0.018
0.613
2.946
0534
0.u72 0.051
0.000 0.@0
t.4t6
L.978
0.016 0.018
0.813 0.374
2.8n
2.894
Ca
Na
K
X total
a.al2
0.533
0.011
0.557
0.088
0.483
0.008
0.579
0.016 0.M2
0.569 0.545
0.fir
0.011
4.5v2 0.598
6.m0
0.580
0.012
0.560
0.008
0.580
s.n8
6.000
6.381 6.148
0.a2 0.m0
5.970
6240
0.030
6.M
6.000 6.000
6.000
0.751
0.020
0.000
1.816
0.032
0.217
2.837
0.359
0.086
0.000
1.3&
0.011
1.M9
2.U9
0.148
o.Lu
0.0n
1360
0.0M
r.29
2.912
0.210
0.105
0.0m
1.542
0.018
0.975
2.850
0.020
0.516
0.007
0.542
0.067
0.il9
0.011
o.1n
0.056
oiw
0.016
aJa
0.116
0.666
o.ou
w93
tpegmadtetype as in Table l; N: numberof analyseqCR: toumaline ftom the cormtryrock- All Fe is
calculaedasFeO.
841
TOURMALINE IN GRANITIC PEGMATITES.SPAIN
Th and U were determined by neufron activation
@,IAA). Trace-elementanalyseswere performed by
X-Ray AssayLabs of Don Mlls, Ontario.
According to King et aL (1988), the determination
of trace-elementandREE concentationsin tourmaline
by neufton activation is hamperedby the problem of
the incident neufron-flux suppressionin the sample,
arising from the large neufton-capturecross section
of B. This effect has been checked using the Fe
concentrationsobtained by neutron activation and
electron-microprobeanalyses(Frg. 2). The concentrations obtained by neutron activation seem to be
between 24 and 49Volower than those measuredby
electronmicroprobe.Thesedeviationscanbe corrected
with the factor Fes1alFeNa,
to permil comparisons
amongthe various samplesof tourmaline.
Tourmaline sampleswere analyzedwith an X-ray
diffractometerusing silica as the internal standardby
scanning over the interval 5-:70" 2g using CuKcx,
radiation.Unit-cell dimensionswereobtainedusingthe
progrrm of Appleman& Evans(1973).
Mnw.nal CtmvflsrRY
All of the tourmalinesamplesanalyzedbelongto the
schorl-dravileseries,mainly the Fe2+-richendmember
(Tables 3, 4, Fig. 3). Nevertheless,the data show
compositionalvariationsthat correlatewith pegmatite
type (Figs.3o4, 5,6). It is alsoremarkablethat in no
casewas a differencefound betweenthe composition
of tourmalinefrom the core and that from the wall of
the samebody of pegmatite.
ln general, tourmaline crystals from pegmatites
showhigher concenfrationsofFe andlower concentrations of Mg than those growing in the country rock
(Frg. 3). Tourmalinetaken from the simple discordant
pegmatites(6) has the highestFe/IVIgvalue, whereas
tourmalinefrom the quartzand andalusitedykesshow
the lowest Fe/Mg value (Fig. 3a). Among samplesof
tourrnalinetakenfrom the countryrock @ig. 3b), those
found in schist near bodies of Li-rich pegmatite
(7) have the lowest Fe/IvIgvalue, whereasthosefrom
the host rock of the simple concordantpegmatites
(4) shows the lowest concentrationsof Mg and the
highestconcentrationsof Fe.
The total number of cations in the Y site implies
vacancies,with a deficiency in R+ (Na++ 2C*+ + K)
and R2+ (Fe2*+ Mg2* + Mn2+) and an excess of
p3+ 14f3++ 48 Ti4\ Clable 3, Fig. 4). Thesemay be
due to the effect of two coupled substitutions@oit
& Rosenberg 1977) involvinC (1) alkali defect:
(OID- + R2+= l?3++ O2-,and (2) proton loss:l?++ R2+
= ft3+* vacancies.
In general,the (R*+RlyR3* value in the tourmaline
from the country rock is higher than that of the tourmaline from the pegmatiticbodies(Figs. 4a"b), which
reflectsthe higher Al contentsofthe latler. In contrast
to the suggestionsof Foit & Rosenberg(1977),
substitutions involving alkali deficiency zue more
common than those implying proton loss. Such
substitutionsare partly contolled by bulk chemical
environmen! H2O-rich systemsfavoring alkali-defect
substitution (Gallagher 1988). Tourmaline from
pegmatites(2), (3) and (4) shows a higher degreeof
TABLB 4. TRACE-ELEMENTCONCENTR.ATIONOF TOIJRMALINE FROM TIIE DIFFERENT
TYPESOF PEGMATITEAND THEIR TOIJRMALINZED COWTRY.ROCK
rPes. rrpe
LI
Sc
Cr
Co
ZD
AE
Se
Bb
Mo
ag
SB
Cg
sf
Ta
w
Tb
U
Ls
Ce
Nd
Sm
EE
Tb
Yb
h
La.lrYb.!
(T1)
(Tl)
(T3) (T3)
52
10.71
10
8
1700 986
4.4
4.4
<5
<5
34
25
8.5
8.5
E.5
E.5
0.5
0.4
1.7
<5
0.42
o.42
o.42
1.1
0,4
<5
0.42
0.42
r.4
6.E
0,08
0.r7
<0.85 <0.85
0,1
0.04 0.04
1.6
6.8
0.08
42
(T4)
(T4)
(T4)CR (T4)CR
(T6)
29
29
460
3
3
112
12r
1n9
4.4
<5
25
12
8.5
26
3.4
0.4
5
<5
0.85
0.42
561
5
<5
68
8.5
8.5
32
29
5
1.7
<5
10.14
1.7
351
3.4
<5
68
8.5
8.5
92
c9
4.9
<1.'1
12
10'71
2.4
0.85
3.4
6.8
0.08
1.O2
<0.85
0,1
0.04
t.2
57.8
34
15.3
4.2s
1.19
<0.85
0,5
0.15
23.0
61.2
36
20.4
+.93
1.19
<0,85
0;8
0.29
r1.2
11?3
4.4
<5
25
8.5
8.5
15
13
0.4
<1.?
<J
0.42
0.42
41.5
74.8
28.9
5.U
0.85
<0.85
0,5
0.12
31.6
0.42
3.4
6.8
0.08
0.17
<0.85
0,1
0.04
1.6
1.02 1.02
3.4
3,4
6.8
6.8
0.34 0.17
0.17 0,t7
<0.85 <0.85
0,1
o,7
0.29
0.04
0.5
3,9
45.2
E6,7
6,46
0.85
0.85
0,5
0.85
34.4
(T7)cR (T7)CR
(T6)
22
54
50
95
16564.8555.48.8
109
131
3
3
12251512141920
1581
663
1258 lO54
4.4
4.4
<3.4
4-4
<5
<5
<5
<5
34
51
25
25
8.5
8.5
8.5
8.5
8.5
8.5
8.5
8.5
96
20
12
51
8.5
3.4
3.4
0.8
2.7
5.8
0.4
0.4
s
1.7
<1.1 <1.7
<5
<5
<5
<5
17
18,1
0.42
0.42
2.9
7
1.2
0.42
valqsiappoLaq/Ybcrarioofchodrit+amlizedocdttali@*numb4oflheleg@dIiq
CR:couty-toc.k
md Sa"hwoba
wted
with theFe,g6/F411fctor'
Table 1. AUdata scel|tu
380
842
THE CANADIAN MINERALOGIST
%
s0
0.0 L
0.8
lo
o0
0.0 L
0.t
Z-1r
1.5
1.4
Fe
. M (1) simpleintraEronilic pegrn.
E @ (2)quare+andal. cofonnpegrn
c Nl €)simptedykes ardapophysos
I
El
1.6
1.4
Fe
r @ (4) simple confoun. pegn, (CR)
A @ (Osinplediscordottpegtn(CR)
a Nl
(s)simpteconform.pegm.
o !
En (O simplediscordantp,gn
O Li-dchdiscordaotpegm. (CR)
(8) Sn-richdisco'daatpegrn, (CR)
Frc. 3. Plot of concentrationof Fe versasthat of Mg in tourmalinefrom someof the different types of pegmatite(a) and their
tourmalinizedcountry-rock(CR) (b). Valuesare expressedin atomsper formula unit (numbersasin Table 1).
-N
h*'
to
62
64
66
R3+
ae-
Lo
o Ml (l)dnpleinragnrddcpegm.
tr W (2)qudlz+mdal. confonn,pgm
o E! (3)cindedy&es drd spophysss
I El (4) simplecofornr.pegm.
1 @ (6) eimplediscordartpogn.
72
uui
62
6,4
66
6.t
7.0
72
ill+
r ffil (4) sinpleconform. pogm.(CR)
A @l (6)*nplediscudatpegn (CR)
. N
o I
(DLt-ddtdbcodaatpm.
(CR)
(8)Sn-richdscordantpeen (CR)
Iric. 4. (/?++ R2+)versusR* variation in tourmalinefrom someof the different typesof pegmatite(a) and thet tourmalinized
country-rock(CR) O). The variation can be relaJedto alkatidefect and ploton-losssubstitutionsin tourmaline.The lines
representcompositionsbetween unsubstinrtedschorl-dravite and the fully substitutedend-members(proton-loss and
alkali-defectend-members).
Diagrammodified from Manning (1982) (numben in rhe legendasin Table l),
843
TOURMALINE IN GRAN]TIC PECIMATITES.SPAIN
schorl
*rf"("0s0
schorl
Alsil&soAls#'e(tot)s0
f (1)simpleinragaoiticpep.
tr (2) quartz.ilndal.conform.pegm
O (3) sinplEdykesandapophyses
pegma (4) simpleconform.
A (6) sinplediscordantpegm-
Alsd&so
(CR)
x (4)sinplecooform-pegn
a (6) siryle discordantpeep.(CR)
(CR)
a C/)U-richdicorda-otpeCn
O (8) Sn-richdiscordantpef.(CR)
Ftc. 5. Al-Fe(totFMg diagram (in molar proportions) for tourmaline from a) some of the pegmatitetype.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 associatedpegmatiresand aplite,s,3: Fe-rich quartz-tourmaline(hydrothermatlyaltered
not
granite,s),4:metapelit€sandmetapsammites
so'existingwith an Al-saturatingphase,5: metapelitesandmetapsammites
coexistingwith an Al-sannatingphase,6: Fe-rich quartz-tourmalinerocks, calc-silicaterocts, and metapelites,7: low-Ca
and metapyroxenites(numbersin the legend
meta-ultamafic and Cr,V-rich metasedimentary
rocks, and 8: metacarbonates
asin Table l).
proton-losssubstitutions,suggestingthat its development was mainly buffered by alkalis insteadof H2O.
On the contraqt, tourmaline from pegrnatites(1) and
(6) presents a greater degree of alkali-deficient
substitutions,which would indicate a higher availability of water in the system.Tourmaline from the
country rock shows a greater degreeof alkali-defect
substitutions, likewise reflecting growth of these
crystals of tourmaline in a H2O-rich environment
during metasomatismof the wallrock schist.
Nevertheless.in calculationson the basis of %L5
oxygenatoms,the relative
of "lkali-defect
A way to allow for protonsubstitutionis exaggerated.
loss substitutionis to normalizecation contentsto 6Si,
but then the degree of proton-loss substitution is
exaggerated.Normalizationsbasedon 24.5 atoms of
oxygen and to 6 atoms of Si represent extreme
positions not found in natural tourmalines(Ga[agher
1988).On the other han4 the contentof ferric iron in
the tourmaline would not changethe disftibution in
Figure 4, as accordingto Henry & Guidotti (1985),
where tourmaline compositionsplot above the line
schorHravite in the Al-Fe-Mg diagram (Fig. 5), the
amountof Fe$ is very low.
In the Al-Fe-Mg and Ca-Fe-Mg diagrams(Henry
& Guidotti 1985),most of the tourmalinesamplesplot
in field 2 (Figs. 5, 6), which correspondsto tourmaline
from Li-poor granitic rocks andtheir associatedaplites
andpegmatites,whereasthe rest of the suiteplot in the
metapeliteand metapsammitefields.
The total concentations of.REE in all tourmaline
samplesoparticularly those within the bodies of pegmatite,arelow Clable4). In termsof REE distribution,
the tourmaline of the country rock has a moderately
fractionated pattern (chondrite-normalized La./Yb
between L4,2 ard 34.4), with a monotonic decrease
from Ia to Yb, followed by an uptum to Lu; the
tourmaline taken from pegmatitic samplesshows a
highly fractionated pattern (chondrite-normalized
IalYb between 0.6 and 3.9), with a scatter of the
values.
The tourmaline from pegmatitic samplesis also
so that tourmalinefrom
poorerin otherfraceelementso
the country rock showshigher contentsin Cr, Rb, IIf,
Th and U Clable 4). It is also notable that the
tourmalinein the country rock adjacentto the Li-rich
pegmatites (7) shows a relative enrichment in Li
(38H60 ppm), Rb (68 ppm) and Cs (29-39 ppm).
Most of the tourmalineprisms are zonedconcentrically aboutthe c axis. This zoning andthe shapeof the
crystals reflect the easeof growth in the c direction
(Iolliff et al. 1986).The zoning is cbromaticandcom-
8M
TTIE CANADIAN
MINERALOGIST
(1) simpleintsaganftic pogm.
(2) quare+mdal @nfom pegm
(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. ((})
a
lI
C
:
O (8) Sn-rich discordantpep. ((b)
\2s
a
\25
b
Mg
Ftc. 6. Ca-Fe(tot)-Mg (in molar proportions)for tourmalinefrom a) someof the peg@aritetypes and b) their tourmalinized
country-rock(CR), with fields after Henry & Guidotti (1985).1: Li-rich graniticpegmatitesandaplites,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
in the core relative to the rim, observedin all groups
(Frg. 7). A relation betweencompositionand color has
not beenestablished,as there are zoneswith the same
color and different composition,whereascrystalswith
similar contents show different colorations. These
differencescould reflect small variations in the ratio
Fe2+/Iie3+,
Finally, results of the unit-cell determinationsare
listed in Table 5. Values of a versw c are plotted in
Figure 8. The tourmaline samples plot near the
schorl-dravitereferenceline @onnay&Barton 7972),
near the schorl end-member,in agreementwith the
chemicaldata.
Drscussron
The observedsom.positionalvariationsindicate the
importanceof coupledsubstitutions(alkali-defectand
proton-losssubstitutions),which aremore extensivein
lsumaline from pegmatitesthan from the country
rocks @g. 4). This variationcould be explainedby the
greateravailability of Fe and Mg in the county-rock
envtonment. Manning (1982) found that the extentof
such coupled substitutions becomes greater with
decreasingtemperature,i.e., ldrth an increasein the
degreeof fractionation. However, all the tourmaline
samplestaken from pegmatitebodies show a similar
extent of these coupled substitutionsGig. 4a); their
845
TOT]RMALINEIN GRANITIC,PEGMATITES.SPAIN
6.50
E
x
6
o
R
t 6.00
3
Es.:o
3
I
EZ@
?
tt<
q
P
Erso
E
1.25
l.@
+st
1.00
+Al(bt)
+Tl
+F9
0J0
035
+Mg
+Ca
+Na
0.00
0.9
0.25
0.m
Ftc. 7. Detailed compositionalvariation of zoned crystals of tourmaline occurring in or near a) enclosedpegnatits (1),
b) apophyseswithin aplitic andpegmatiticfacies(3), and c) simplediscordantpegmatite(6) (CR: countryrock).
extentis thusnot a usefirltool to monitor differencesin
degree of fractionation. Moreover, the tourmaline
occurringin the county rock nearsimpleconformable
pegmatiles(4) showsa gre,,tetexlent of suchsubstitutions relative to that in the schists near the simple
discordantpegmatite$(6), the Li-rich pegmatites(7),
andthe Sn-richdykes(8) (Fie. 4b). Thusodifferencesin
the conditions of crystallization, such as the rate of
crystallization and in the compositionof the original
melts, also could affect the exlent of these substitutions.
Tourmaline in the pegmatiteshas, in general, a
higher Fe/IMgvaluethanthat found in the county rock
(Fig. 3). Among the tourmaline samples from
pegmatites@ig. 3a), the richest in Fe and the poorest
in Mg occursin g[e simFle discordantpegmatit€s(6),
followed by the intragranitic pegmatites(1) and the
apophyseswith aplitic and pegmatitic facies (3).
Tourmaline from the simple comformablepegmatites
(4) showsa lower contentin Fe; finally, the richestin
Mg is that associatedto the quartz-andalusitedykes
Q). At a particular set ofpressure-temperatureconditions, the compositionalevolution of the pegmatiteforrning melt-fluid system is closely related to the
stability of a given compositionof tourmaline.Thus,
basedon ionic sizeandcharge(fauson 1965),hthiumbearing tourmaline would be expectedto be more
stable at lower temperaturesthan Fe-rich tourmaline,
which in turn will be more stable than Mg-rich
tourmaline. Previous investigators (Neiva 1974,
Manning 1982,Jolliff et al. 1986)agreewith the fact
that tourmaline associatedto the earliest stages of
differentiationis richer in Mg thanthat crystalizing in
the later stages.In addition,zonedcrystalsin our suite
tend to show a rim emiched in Fe relative to Mg,
compaxedto the core. It thus seemsthat the sequence
obtained for the Fe/I4g value in tourmaline from
pegmatitescould be used as a tool to establishthe
86
TIIE CANADIAN MINERAL@IST
TABLE 5. IJNIT.CFI I - DIMENSIONS OF
REPRESENTATIVETOURMALINE SAMPLES FROM
T}ilE PEGMATTTESOFTIIEFREGENEDA AREA AND
THEIR TOURMALINZED COI]NTRY.ROCK
Ttpo peg.* a(A)
c(A)
rs,992Q)
15,957(4)
(r2)
15,950(1)
(r3)
15,960(1)
15,956(2)
Cr3)
15,957(1)
G3)
15,961(r)
G3)
(I3)
15,971(1)
r5,959(r)
CT4)
(r4)
rs,954(1)
15,959(1)
CT4)
(r4)
15,968(1)
(r4)
15,954(1)
158s3(1)
CI4)
(r4)
r5.958(r)
04xcR) rJ,967(1)
CI?X(R') 15,955(3)
G1)
Gl)
cla
Y(43)
0,44E
7,166(l) rs87A$)
7,156(3) 1578,2(9) 0,449
7,r69(1) 1s79,7(3) 0,449
7,154(0) ts78,3(2) 0,448
7,L57(r) 1578,0(4) 0,449
7,r52(t) Ls77,3(2'., 0,448
7,r7o(2) 1582,2(5) 0.449
7,153(1) 1580,4(2) 0,448
7,r58(0) 1s79,1(2) o,449
7,r5r(1) r5?6,6(3) 0,448
?,15s(0) 1578,3(2) a.448
?,r56(1) 1580,3(4) 0,448
?,1s2(0) t576,6(2) 0,44E
0,450
7,178(r) rs82'2Q)
7,161(1)
7,rs3(0)
7.r7s(2)
GD(CR) rs,976(2' 7,t75(2)
crO(cR) 15,958(2) 7,r7s(r)
(nxcn)
7,167(2)
?,t52(L)
WXCR)
Ls79,4(3)
L579,5(2)
1582,0(6)
1586,r(5)
1582,5(4)
1s?9,8(7)
(* numbemof pegmatitcqpes as in Table I
rock) .
0,M9
0,448
0,450
0,M9
0,450
o,M9
0,448
: cotulEy
sequenceof crystallization for the pegmatitebodies.
According to this ratio, the most evolved tourmalinebearing pegmatiteswould be 66s simple discordant
pegmatites (6), followed by tlte intragranitic
pegmatites(l) and the apophyseswith aplitic and pegmatitic facies (3). Finally, d[e simple comform.able
pegmatites (4) and the quartz-andalusitedykes (2)
seemto be the leastevolvedpegmatites.This sequence
agreeswith that obtainedfrom the K/Rb ratio in micas
and K-feldspar from these pegmatites(Roda et al.
1993).In the pegmatitesofthe Fregenedaarea,therefore, tourmaline associatedwith the early stagesof
crystallizationis richer in Mg than that growing later,
which is richer in Fe.
Concentrationsof REE are uniformly lower for
tourmalinein thepegmatitescomparedtotourmalinein
the country rocks. This rnay mean that the .REE
abundancesand disfributions in tourmaline are predominantly confolled by the parageneticconditions,
that is. the REE contentin tourmalinereflects theREE
conlent of the medium where the tourrnalinecrystallized (Jolliff et al. 1987,King e/ aL 1988).Therefore,
the high concentrationsof REE n tourmalinefrom the
country roctrs may be inherited from the schists in
which they grew. This inheriunce could cause the
similarity in shapebetweenthe patternsfor tourmaline
of the county rock and thoseof the metasedimentary
rocks of the Schist-MetagraywackeComplex.
Tourrnalinefrom the country rock near the Li-rich
pegmatitesshowsevidenceof enricbmentin Li, Rb and
Cs, asa result of the interactionof a fluid derivedfrom
l9(., z.l
7.
elbaite
16.060
15.780 15.820 15.8@ 15.90015.940 15.980 16.020
"
a(A)
Ftc. 8. Unit-cell dimensionsof tourmalinesamplesrepresentativeof the different typesof
pegmatite and their tourmalinized country-rock Referencelines from Donnay &
Barton (1972),modified from Epprecht(1953).
TOTJRMALINEIN GRAMTIC PECiMATITES.SPAIN
the crystallizing melt and the country rock.
Tourmalinizationof the schistsis strongonly in a halo
approximately 20 cm vdde around these pegmatite
bodies; beyond 50 cm, tourmalinization is not
developed.
Finally, the tourmalinecompositionsplot in the field
of Li-poor granitic and associated rocks, on the
Al-Fe-Mg and Ca-Fe-Mg diagrams. Note that
the pegmatitesthat contain tourmaline are spatially
relatedto the Li-rich Lumbralesgranite,which contain
from 170to 230 ppm of U (GarcfaGa:z6n& Locutura
1981). This apparentconffadiction suggeststhat, on
one hand, the composition of tourmaline may be
influenced by the chemical environmenq achieving
mixed peffogeneticaffinities, an4 on the other hand,
the geochemicalconditionsexisting during the formation of the granite and its assosiatedpegmatitesare
complexandnot completelyunderstood.
ACKNowllDGg\dENTs
847
(1982): Estudio del metamorfismo existente en
torno al granito de Lumbrales (Salamanca). .Srvdla
Geolo gica Salmanticensia 17, 7 -20.
DoNNA! G. & BARroN,R., Jn. (1972): Refinementof the
crystal structureof elbaiteand the mechanismof tourmaMineral. Petrogr.Mitt. lE,
line solid solution. Tschermalcs
n3-286.
EppREctrr,W. (1953): Die Gifierkonstantender Tirmaline.
SchweizMineraL Petrogr. Mitt. 33, 48l-505.
Fon, F.F., JR.& Ross{BRG,P.E. (1977): Coupledsubstitutions in the tourmaline group. Contrib. Mincral. Petrol,
62.109-tn.
GALLAcIIER.,V. (1988): Coupled substitutions in
schorl-dravitetourmaline:new evidencefrom SE Ireland.
Mineral. Mag. 52, 637-650.
GARcfAGARZON,
J. & LocuruR4 J. (1981): Dataci6npor el
m6todoRb-Sr de los granitosde Lumbrales-Sobradilloy
Villar de Ciervo-PuertoSeguro.Bol. Geol.y Min- dz Esp.
9L1,68-72.
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Received July 5, 1994, revised manuscript accepted
Janunry 11, 1995.