otlprint NGU Butterin 423. 19 39
OYSTEIN NOBOGULEN & BJORN SUNOVOLL
Strontium isotope composition
of the Bindal Batholith,
Central Norwegian Caledonides
Trondheim 1992
,
Strontium isotope composition of the Bindal
Batholith, Central Norwegian Caledonides
OYSTE N NORDGULEN
& BJORN SIJNDVOLL
NordAul€n@ & sundvo
Notuoc a^
B
1992 Slronrufr sotopo composion or lhe Bnda Balholrh C€nra
Ca 6don des
study or th6 B'nda Ballro itlr has been daftiod oul The dala qeneraly do
not pormit pr€c se and accuraro aqe cacuatons rrowevet, qood eslmaies ror ndia sr ratos
are commony obrainsd Low nita ratios (c 0 704 0 705) w lh Litl o interna vanaton are prss€nt
n Orantuds n rhe sourh€astarn parl ol lhe ba|ro ith Rocks wth rnle.modiare niialratos (0705_
0710) or€dominalo and aro presont ihrouqhout nost ol rhe balhorlh, whereas very h'arr ratos
1:'0715) ars round rn lourmallne granitss and analocic aranitords n the w€st. consdern9 a
subducrion ro ar€d sen n9 ro, i6 pluronism ln€ g€ograph ca d st buton ol sr n[ar ratos wou d
ppir! subdlci on zone
Contamnalon or tho maqmas at lhe levd or emplaGment is ihougrri to be or mnor imponance
and dsrurbance ol tlr6 solop€ systEm by socondary arteraton appeare 1o be realvely uncom
sotop'c var arion wirhin p utons are probab y a resur ollsotopc heteroqenery
as not boen obnarated by nagnaric procosses The range n Sr
in rar rarios rn tho B ndal Baiho lh r€l acts lhal tlre lran to'ds were d6rv6d n var able propon'ons
iion rerauvely non radogenc uppd manlre io lower crusr as wel as sotopca y rreierogeneous
laysteh Notdgutgn, Na9es geotag6k6 undetsoketse Baks3aa6 Latte N 7AA2 fondhein, Naqay
Btatn Sunlvotl Minetah)gtsk Geotogtsk ltluseun, sa,59t t,0562 osto 5 Naqay
lntroduction
Regional context
The caledonian B ndalBatholith, which is loca_
The Bindal Batho ith (BA)occurs in the Helgeand Nappe Compex (HNC), which belongs
lo ihe Uppermost Allochthon in the Scand navi
an Caledonides (Gee et al. 1985). As outineC
by Thorsnes (1S87), Nordgulen & Schouenborg (1990) and Thorsnes & Loseth (1991), two
series of metasupracrustal rocks are intruded
led in the Helgeland Nappe compLex in no(h'
centra Norway, consists of a variety oi rock
lypes ranging in composition lrom malic olvi
ne gabbro to leucogranite. ln this paper, we
reporl the results oi a sr sotope nv€sligation
of the batholirh. A1 preseni, a tota of c. 250
analyses are available, incLud ng 45 samples
analysed by Priem et al. (1975), Nissen (1986,
1988) and Torudbakken & Mickelson (1386)
Pa(y as a consequence oi th€ overal low
Rb/Sr ralios, acceptabl€ isochrons and age
determinatons are rarely obtained. However,
the analyses allow roasonably precise estima
tes to be made for the niual
(Sn) ior most plutons and rock types The
resulls are therefore of consderable interest
by the granltoids. One of these consists oi
migmatuc gneisses, calc silcate rocks and
marbes. Earlier work n the norlhern parts
oi rhe HNC suggests thal these rocks are
Precambran in age (Biis & Ramberg 1981,
Toftrdbakken & Ramberg 1982, Bratrli et al.
1982). The other metaslpracrusta seres,
wh ch compris€s mafic and calcareous cong omeraies, calc'silcate rocks, marbles, psammi
tes and schists, is thoughi to represent
a
for c assilicalion and comparative stud es, and
are useful when trying to constrain possible
source regions for the graniioids.
lsotope analyses ar€ not availabe irom th€
norlhweslern part of the batholith, .e. the area
belween velsnfjord and Ranaljord, and lrom
cover sequence to ophio il€ fragmenls in the
rocks along the eastern boundary ol th€ Helge_
and Nappe Compex (Fg. 1).
or younger in age (Nordgulen & Schouenborg
1990, Thorsnes & Loseth 1991). The ophioliie
HNC (Banq 1985, Loseth 1985, Thorsnes 1S85,
Hedal 1987). Correlatinq the opholite lraqmenrs n the HNc with ihe Eary ordovician
Leka Ophiolte Complex, il is inl€rred thal the
cover sequences musl be Early Ordovician
20
Oystein Nordgulen & BtornSundvall
{t"
!' tt
F
i.i
--r
'j'l i',,i i
I
J l:4.
N,: l.
rr'l
I
l=i
",{
"
: !----',
.jt.
i: i. -
ffir',i'
.r:.
.,
-!
" lrt
-7'.: .:
./.:'.:i
.......|'N
..'. . ...\
coFr roN!F
GFsoo
oF
Fic. 1. Geolosical map ol lhe
B
i-
1 r.@
o/ r
nda Batho ith
'n-i
'i
Ei
rri
jt
Sttanl)un isatape comqasilian
iragments as we I as th€ir cover rocks were
delormed and metamorphosed pror to being
cut by Laie Ordovc an granitolds. Juxtapositi
on ol the opholite relatod rocks with the ol
der metasupracrustals musl also have occur.
red in lhe Ordovician.
The Bindal Balhoilh consisis 01 rnore than
50 pluions and occupies a substantial part
ot the HNc (Fg. 1). Descriptions ot parts ol
rhe batholith were provlded by Kollung 11967),
[4yrland (1972), Nordgu€n (1984), Theissen
(1986), Gustavson (1988), Nordgulen & Mit
chel (1988) and Nordgulen & Schouenborg
(r990).
The rocks are qen€rally equigranu ar or
porphyritic, mediurn- or medium'to coarse'
grained and pr€dominanny granodiorilic to
granitic in composiiion. A lew plutons are tona-
lilic, and gabbros, diorites and monzonitc
rocks are present in som€ areas. Tourmaline
granltes and analeclic granltes are iairly abun
dant in the western parl oi the batholith (Fg.
1). Perrographc and chemica data show thal
the majorily oi the rocks are l-type accord ng
ro lhe classiJication ol Chappell & white (1974)
However, some plutons show transitionaL be_
havour towards A{ype gran tes, and the ana
tectic rocks in the west may bo regarded as
Srype granii€s (Nordgulen et a. 1988).
Only a imiled numb€r ol age del€rminauons
are avaiable from the 88. Bb-Sr whole_rock
and mineral data ndicate a fairly wide age
span ranging trorn the Late cambrian lo the
Midde Slurian (Pr€m et al. 1975, Glstavson
21
ppm) Bb or sr, however, were slblecled to
isotope diluiion (lD) determination. Sr isotope
ratios and lD-d€lerminations by mass speclroscopy, and Rb/sr ratio determination by
xBF-spectroscopy were carried out at ihe
Laboralory ior geochronology and isotope
geology at the L4 ineralogica -Geolog ical Museum, University ol Oslo. The analyUcal procedures used have been published e s€where (Ja-
& Heier 1978). For some sampes,
Rb/Sr ratios were del€rmined by XRF-spec
troscopy at the Nculaboratories (Table 1).
cobsen
The rnass-spectrometer, a VG 354 tive colec-
ror instrumeni, yieded a vaue for the NBS
987 Sr standard ol 0.71025 ! 3 durng the
perod ol analysis. ihe error ol the xRFl%, and
determinalions were esumated lo
=
.5%.
thal 0l the lD method
= and age dala quo_
All isochron calculatons
ted have been performed or recalculated using
the decay constanls recommended by steger
& Jeger (1977). All errors are quoted al the
2o level. Eemental and isotopic data are lisled
in Table 1 loqether with (!'Srvsr)0 ralios caculated with respect to an age of 440 Ma. For
less than 1, a
samples wrth
20 lra shilt in the assumed age w ll cause a
very small change (<0.0003) in the calcu aled
initial ratio, whereas samples wilh I'Rb/N6sr
ratos of c. 10 w ll have a change of c. 0 003
& Presrvik 1979. Nissen 1986, 1988, Torudbak-
ken & Mickelson 1986). Recently, a number
oi U-Pb age determinations on zircons have
yelded Late Ordovician io Early 10 [,'liddle
Sluran ages lor different rock types in ihe
bathoiih (Nordgulsn & Schouenborg 1990
Nordgulen €l al., n pr€p). The U'Pb data thus
suggests a relaiively narrow age range for the
plutonism and indicales ihat lhe dates obtai
ned by lhe Rb-Sr m€lhod must be confirmed
by more pr€cise dating lechniquos.
Analytical methods
A lsample preparalions and chemical prepara'
lions were performed at the NGUlaboratories
Bb/Sr ratios were generally determined by
xRF-speclroscopyi sampes having low (<60
Strontium isotope data
The southwestern parl of the batholith
to iniermediate sze plutons
spanning a wide compositional range are pre
seni in this area. Analyses are available for
the Krakfjellel, Terrekfjellet and Heilhornet Plu
tons ln Bindal, and the porphyrtc sklinna Pluton, which is located solthwest of Leka (Fig.
1). From the Holm p€ninsula, north oi the
Heilhornet Puton, data are presenled trorn
Several large
tourmalino granite, anatectic granilo and a
delormec megacryslic granite west of Bindalsijord. lncluded with the data lor the tourmalne
grantes are two anayses ol chemicaly and
Sttun\un Batape c.npasnDn 23
PdDhyritic s6nite, Sklinna
2922
16252
3332
r09
5
16252
Porphyroclsstic qranho, Bindals€id, Hdlm p.ninsula
555
r3253
Andalsh.non Pluron, Vav6lstad
vst
2
r3263
13263
14263
r3263
r493
39r50
Gaupen Pluron, ursijord
Pophy.itic araniies associared wiih rhe velliord pluion3
ECOORD
14252
33705
39035
NCOOFD
725430
725225
Pophyritic sranirB sourhwest ot volfiord
23r 0
1931
24
Oystetn NatdgDleh & Blatn SLndvoll
Maric to inrormodiats olulo.s in Voltiord and Urstiord
Sr
33320
972
.220
.335
725124
135
N37
50
14254
N37
56
14254
725575
7033
a2
21
Anarecric qranitoids at V€oa
36315
113
139
vG23
vG25
r26
17262
17262
1 316
.7195
Granites in the vistsn Lomsdal area
14262
14262
13251
1251
725230
TA53
1.247
r52.3
N36 64
14252
13251
StrantiLn isotop," canPasnion 25
Granires in the 6r6a Kolsvik Fuqlstadtj6ll6t
33215
't11.2
15
N37121
N37
Tonalates
14252
14252
{Fustatnet Pluron and Reinfjellot Massii
''srr.*
r65
535
Gran'ro'ds south or MGj6€n
1 593
42254
GBnnoids in the Kalwainet area
559
3
351
14252
Iwo
mica sraniroid dykes
261 5
13.292
vsr3
r3251
39360
1251
r3253
8300
r
3253
1121
561
13252
N37 125
r3253
14252
33325
721560
722445
2305
2333
fsn"sr).
26
Oystetn No.dguten & Blam Sun.lvotl
Metasodimontarv rock, Holqoland Nappe ComDlax
1931
N33
6l
722565
113 9
17252
N33.63
2.692
155.9
36525
110.3
17252
213.3
N33 69
17252
36325
r
721545
3253
I3253
33335
1325r
339
14251
725365
lsotopically simrlar rocks from a large body
of tourmaline granite solthwest of Veljord.
Dykes of leucocratic 2 mca grantes are
comrnon ln the Bindal area. lsolope data for
these rocks are presenl€d logether with those
from other similar granites (see below).
The Heilhornet Pluton
Th€ results from the Heithornet ptuton (Fg.
1) have been
published by Nordgu en & Schou-
enborg (1990), but are shown in Fig. 3 for
comparative purposes. tn contrast to the Krak
tjellet and Terraklje let Ptutons, the Heithornel
Pluton has a tendency towards alkatine compo
sitions with higher alkali/lime and FelMg rai!
os. consid€ring the traco etements, lhe Hei!
The KrAkfje et and Teftakfjellet Plutons
These plutons are cherniealy very simlar,
however. there are consislenl srnal diierences in both major and trace element contents
(Nordgulen, in prep). There are marked con
irasls n the abundance oi Bb and Sr. and
at simiar leveLs of si,, the Krakljellei Puron
has higher Sr and lower Rb than the Terrekfjellel P uton. On the sotope d agram (Fig. 2),
the plulons pot n two distinct tields with lhe
ces oJ LBEE and HFSE, and also higher Rb/
Sr ratios. Nordgul€n & Schouenborg (1990)
described the Sr isotope data and catculated
an isochron for samples lrom the central part
of the puton. This gave a date ol 428 1 I
exception of one sample lrom the TerraklelLel
P uton wh ch pois on the trend def ned by the
borq, 1990).
hornet Pluton has significantty higher abundan
Ma (Srl = 0.70699 I 0.00028i [4SWD = 2.32),
a result which ovorlaps with the U,Pb zircon
date 01 444
):
11
I/a
(Nordgu €n & Schouen-
KrAkljellet PLuton.
The Sr data ior the Krakljellet Pluton plot on
a wel defined trend (Fig. 2)w th an in tia ralio
of c 0.7055. Regression of al daia do not
yield a satisfactory isochron, however, a geoLo
gcally reasonable date oi 464 1 30 Ma (Srl
= 0.70549 1 0.00005; MSWD = 3.74) was
obtained for six samples in ihe ceniral part
ol the
p uton. Th
s resull is within error oi
U-Pb zircon dale of 443
1
a
7 Ma for the plu-
ton (Nordguen ei al., in prep).
The data from the Terrdkliellel Pluton have
a comparatively larqe scalier which prevents
the calcu ation ol an sochron for ihe p uton.
However, assurning an age of 440 Ma, lhe
Srl values ior ihe Terdkliellet Plulon have an
approximate range between 0.7075 ard 0.709.
Tourmaline granites occur as small stocks and
dykes at the Holm peninsuta north of the
Hellhornet Pluton (Nordgulen & Bering 1987,
Nordgulon ei al. 1989). They cut marbte, catcsilicate schist and semi-pelitic schist and are
cl€ary younger than the strong 52lotiation in
th€ hosl rocks. The tourmaline grantes have
high Ab/Sr ratios, and athough ihere is consi
derable scattor in the Sr sotope ratios (Fig.
3), most of the samples deline a lrend tndicating an initial ratio oi c. 0.717. Assuming an
age ot 440 Ma, lnitial ratios are €ssenriaity
b€tween 0.715 and 0.725 with two samptes
showing values as high as 0.735. The granires
al Holm contain abundant lractur€s and shear
F
Sttonttum lsatape canposnton 27
Fig.2. sotope
d aOram
0.715
lortheKrak
ler6l and r6trAkfl6r3r Prurons. rh6
slippod rof€Gnco lne shown n
Fgs 2 9 coirespo^ds lo an age ol
0 710
3
0.705
TERRIIOJXII.f,T PIUTON
KRiKFJFJ,I,F]T PI,INON
0.700
0.4
0.6
o
0.82
0.80
1.
3
lsolopo diagram lor som€
o.7n
T
0.76
0.74
TOURMAUNE GBANITD
ANATICTIC GRANITB
PORPE, GR-ANTTE
o.72
o70
BIIIIIORNET
PLUTON
I
ol which have quartz and/or
sulphide fillings. Therelore, s€condary processes rnay have conlributed to the spread in
initial ralios.
A large body of tourma ine granite, which
occurs soulhwest oi veltjord (Fig. 1), s represented by two samples in this study (vF60
and N88-108; Table 1).Ih€ grante is geoche
mically simllar 10 and plois close to lhe mosl
svolved tourrnal ne granites at Holm.
Anatectic granite occurs as an elongate NE-Sw
trending body at the Holrn peninsula n Bindal
(Fiq. 1). Ihe qranile contains variable amounis
of xenoliths of metased mentary rocks. ln p aces it has transilional contacts lowards diatex
itic metasedimentary rocks, whch are aso
common at the Hom peninsula The pulon
consisis ot med um'grained graniie and ocally conlains varable amounts ol euhedral Kfedspar megacrysts. Four samples lrom the
area immediately north ol the Heilhornel Plulon have been anaysed, Compared with the
iourmalne granite, wilh which it is spalially
associated, the anaiectc granile has lower
Bb/Sr raiios ('"Rb/rsr < 3; Fg.3). The data
indicate an initial ratio of c. 0.718. which ls
2A
Orctein Nordauten A Bian Sundvott
close to ihe inilial ratio 10r most oJ the lourmaline granites. This suggests that these rock
typesmay have partly similarsource reqions.
flc plutons ln the
Ve ijord-Ursfjord ar€a, and
anatectic granites from Vega (Fig. 1).
Mafic ta internediate intusions in Velfjord and
The Skhlna Plutan
The Sklinna Plulon is located on a smal group
of islands c. 30 km norlhwest ol Leka (Fig. 1).
It cons sts o1 coarse-grained megacrystic granite with 70-74 % SiO,. Four samples with a
range
in Bb/Sr between 1.0 and 2.5
have
been analysed and delin€ a trend with an lni_
tial ralio of 0.710 (Fig. 3). Two svongly lractonaled sarnples o1 a line-grained gran te sheel
in lhe pluton have very high Bb/Sr ratos (Tab_
le 1) and plot on ihe exlension of the trend
for the megacrystic granite (not shown on Fig.
3). The Srl values lor S120A and 51208, with
respect to 440 Ma, are very ow (Table 1)and
g[i:
J;:Efl : :::J:::Ti',J, ""ijJ""l,{:1,:r
sron ol dll lhe samples yrelds ar appa'Fnl
oale o' c. 396 I/a. T'ris date rs the youngesl
which have been lou'rd ror dny tock 11 lhe
BB However. textL r al evroence shows lhal lhe
ol lhe Shln'la Pulor has pdnly
sullered extensive sericiticaUon which may
have caused disturbance in th€ nb Sr isotope
system. The indication ol a l\,4iddle Devonian
age obla neo ror lhe pluton ll^erero'o needs
to be confinned by more reliable data.
plagroclase
The Bindalseid Pluton
The Bndalsed Pluton is located irnmediatelv
norll' of lhe Heil'rorrel PlJIon (Frg 1\' lt con
srsis ol strongly torrdteo granrtF rsro. s .
73%) with ori€nted microcline megacrysts in
a m€dium-grained matrx. The two analysed
samples have high Rb/Sr ratios, and the Srl
vaues are 0.717-0.719, assuming an age ol
440 l',ia (Table 1).
IJrsfjotd, Veltjord, Visten and Vega
Several ditlerenl rock types hom a nLnbbr
ot pl]tons have been analysed. This includes
mafic lo intermediate intrusions in the velfjord
and Urs'toro drsnrct. ine porphyrilic Anddlshal
ten Pluron. a porphyrilic g.anodrorle n Urs
fjord called the Gaupen Pllton, small bodios
oJ porphyritic granite associated wilh the ma'
The Sr daia from these rocks are shown n
Fig 4. For ihe majority of lhe samples, which
have "Rb/"Sr ratios < 0.5, the data plot in a
narrow band with Srl values between 0.7057
and 0.7071. These samples include those trom
the three intrusions oJ the Velfjord Massit (Koll-
ung 1967) and a mafic gabbro north ol Ursfjord. Fve sampes trom dioritic to gabbroic
p utons ln the area between ursfjord and vel
lord have, with one exception, I'Rb/6Sr ralios
> 0.5 wiih a range in Srl between 0.708 and
0.710. The plutons are spatially associaied
with anatectic metasedim€ntary rocks and
porphyritic granites wiih hqh Srl vaues (see
below). The common presence of pink garnet
in some oi ihe rocks would indicate thal lhey
may have experienced some contam naton
from m€tasedimentary rocks orthatsuch rocks
were present in the source region lor the
magmas. This could expla n ihe elevated Srl
values compared to other maiic intrusions in
the Velfjord Ursljord area.
The An d al sh atten Plulon
Th€ megacrystic Andalshatten Pllton is a lar-
ge inlrusion located between Velfjord and Vis-
ten (Fig. 1). The pluton is characterised by
e!hedral megacrysts (2-5 cm)of greyish white
m crocline which occur in a medium- io coars€grained granodioritic matrix. lvfaf c enciaves
are common, and the granile is cut by a number of granitic and basic dykes. ln the south'
western part of the puton, m€dium lo line
grained toliated dioritic rocks are enclosed in
the pluton logether with smaller bodies ol
peridotile and maiic gabbro. Xenolilhs ot migmatitic mica gneiss are presenl in lhe easlern
part oi the pluton, whereas in lhe west the
xenoliths consist of banded calc-silicale rocks
and polymict, cacareous conglomerates. Large
rafis ol banded marble and small bodies oi
serpentinte occur in the cenlral parl ol the
The Anda shatlen Pluton displays a considerable chemica variaton (58 70 % S|OJ which
is reflected n a wide rang€ in Bb/Sr ratios.
Of lhe seven anaysed samples, al bul one
(N88-05) pot on a fairly well defined trend
(Fig. 4). Regression
oi sx
sarnples y€lds a
Strantiun isotope
Fq
hyr
I
rsolope
dagramlor
re porp
enpasnbn
29
o./25
!c gran iods oftrre Gaupen and
Andarsrratlei Pul.ns and
mal.
to
the Andarshaien Pu'on
(N33
01
nramedaie rocks n the verlJord
an.l LrrslJord a,ea F led t,n0es
reF,esed n,.roporprryrtc dykes n
0.720
0.7t5
GATIPEN PI,UTON
ANDAI,SHATTEN PLIJ'TON
0.705
MAFIC TO INTf,RMEDIATE ROCKS
0.700
0,0
date
ol 448 1 48 Ma (Srl =
0.70855 1
0.00031; MSWO = 29.52), which is in aqreement with a dare oJ 447 a 7 Ma oblained by
the U-Pb method on zircons (Nordgulen et
a.,
n prep).
The megacrystic qrante is cul by a set of
line'grained microporphyrilic dykes which ar€
chemically relat€d to ther host. Sr data for
two oi these are also shown on Fig. 4, and
they plot sliqhtly below the trend defined by
the porphyritic qranite.
0.5
1.0
1.5
rocks indicale lhat the granites were genera
ied by in situ mehing oi metasedimentary rocks
during emplacement ol the Velfjord plutons
(Barnos ei al., 1992). The pres€nce of garnet,
muscovite, silimanile and monazil€ is in accor
dance with this inierprelaiion. Chemically, lhe
rocks have a kallne affinity with hiqh alkali/lme
and FelMg ralios, and high abundances ol
LREE and HFSE (Y, Nb, 24. Sr isotope data
are availabl€ for lhree samples. The resulls
show a large scaiter (Fig.5), which may indica
h ghly heterogeneous crusialsource reglons
le
The Gaupen Pluton
The Gaupen Pluton, wh ch cons sts of megacrystic granodiorite, s located in Urstjord north
of B ndalsljord (Fig. 1). 11 contains abundant
malic encaves and
ls cut by a
variety ol
mafic and acid dykes. The pluton is chemical'
ly and mineralogically quile similar to the An-
dashatten Pluton. Four samples have been
analysed and ploi in a small cluster sliqhtly
below the trend defned by the Andalshatlen
Porphyrtc graniles afe also presenl as
small, irregular bodies associated with mafic
intrusions betw€on Ursfjord and Velfjord. The
rocks are texiuraly simiar to lhose in Vel'
ljord, however, they do not posess the alkali
ne chemical characteristics exhibited by ihe
Veijord samples. Assuming an age ol 440
lva, the Srl vaues are between 0.717 and
0.720. which is in accordance with a crustal
origin lor the rocks (Fig.5i Table 1).
Pluton (Fig. 4). The dala indicale an lnitial ra-
tio oi c. 0.708 for the Gaupen Pllton
The granitoids on Vega are grey, mediumPoryhyritic granites
Severa small bodies oJ porphyrtc granile
occur adjacenl to the mafic to intermediale
p utons oi the v€lflord Nlassif (Myrland 1972).
The granltes are gensrally quile strongly foliated wilh whiie to grey porphyroclasts ofrnicroc
ine in avariably recrystallised matrix. Transilio
nal contacts towards diatexitic, sem-peitic
grained and extremely heterogeneous rocks.
They are rlch in metasedinentary xenolths
and commonly conlain maiic clots cons sting
essentialLy of botte and qarnei. The Sr data
show a large scatter (Fig. 5i Table 1), and
apa( from a diorite (VG 10), the initial ratos
are between 0.714 and 0.736 {based on 440
Ma). A het€rogenoous metasedirnentary sour
30
Oystein Nord.iuten A Biarn Srndvoll
Fg
r.
5
sotopedaqram lorporphyn
sranres,n rrre velord reqon
aiatecl. aranrods ar voga and
va,ous melasedmentary rocks n
the
He qe
and NdpFe comprei
0.?6
p
0.74
o.72
!
PoRPH. GRAMTES (sr !.ELFJoRD)
iA PORFH.
(YELT
GPIAMTES (\TLTJORO)
GRANITES
,INATF'TIC GRANITOTDS
CRANITdIDS ((V'EGA)
ITEGA
' AIATECTIC
METASEDIMENIAiY ROCI(.S
0_70
o'Rb/'sr
ce, or possibly exlreme contaminaiion ol an
l-type magma, would be consisteni with the
Sr data.
Metasedimenlary rocks
Sr isotope data for metas€dimentary rocks
coLlected in a number oJ localiues in the south
ern parts of the HNc are aLso shown in Flg
5. The isotop€ ratios, al an age oi 440 l',|a,
are belween 0.706 and 0.744 and scatter in
a range similar to anatectic granitoids at vega
and in Bindal as well as the tourrnaline granit€s and the porphyritic rocks associated with
lhe mafic to interrnediate rocks in velljord and
Ursfjord. Judging from lhe Sr isolopes, the
metas€dimentary rocks would therefore provi_
de a suitable crustal sourc€ tor the granitoids
with elevaled inilial rauos. This is in agreem€nl with Nd and Pb'isotope data (Birkeland
et al., in press), which indicate a realively
strong upper cruslal influence lor thes€ grani-
Granites in the central part
Bindal Batholith
ol
the
of Tosbotn a large body (c. 50 x 25 km) of
this granits is located in th€ mouniains b€tw6envistsn and V€lfjord in thewestand Eit€radalen in the €ast- ln this aroa, lhe granii€s intmde migmatitic paragneissos. N€ar Tosboin th€
granito also intrud€s monzonilic and monzodioritic rocks, and east of Tosen it occurs
between migmatitic gn€isses in th€ w6st and
the Kalwatn Pluton iquartz monzonite) in th€
east. To th€ south, similar granit€s occur in
the oksdal l4assif and al Fuglstadti€ll€t, and
ihey also intrud6 porphyrilic granodiorito northeast ol Kongsmo€n. Thus, th€ granitos can
be Jollowed for at l6ast 100 km along slrike.
A small granil€ pluton, which rntr.ides metas6dim€ntary rocks on the island Oksninga south
of th€ Krakfj6ll6t Pluton (Fig. 1), is also included in this group.
Although ihsro is some variaiion in grain
size and textur€, th€ granit€s have b€sn lr€ated as on6 unil. They havo c. 70 % SiO,, and
gensrally display litrl€ variatron in chemistry
althouqh tonalitic lo granitic rocks occur ln the
Oksdal [4assif south of Kolsvik.
ln Fig. 6 the Sr data Jor the gianites
hav€
plotted wilh three dill€reni symbols represenl-
ing diflereni geographica areas. From no(h
A b6lt of lin€- to msdium-grainod 2-mica grani
t6 is present along a N-S trondjng zone close
to the central axis of ths BB (Fig. 1). North
to south these are: 1, the Visten-Lomsdalarea;
2. lhe Tosen-Buadal€n (Ko svik) areai and 3.
the area south ot Buadalsn including a small
qranite plulon situated on the island oksninga
Strontiun isotope cDn1osttion
rsorope daqrani t.r granlc
lock5...utrnqaonqrheNStren
Fo 6
d
iq.exra pailol
rhe
31
o.725
E'ida Balrro
llr N3333 lrabe 1) has a verv
hah rsrrls alo and s nor srrown
o.720
o.715
0.705
11STXN IOMSDAL
TOSSN BUA-DATEN
BIJADAI,'N FUCI.sTADFJXLLET
o.?00
0.75
rh; nodhai, oan
.r
'he
ba'rro th
o.74
0.73
o.? 1
LUKTVAIN G&INTTE
FUSTVATNEI TONAI,ITE
TIfO MICA CRANITOI}S
0.?0
1
in Bindalslord, south of the Krakfjellet Plulon
(Fig. 1)
It s cear irom Fiq.6 thal the gran(es show
a consislent isotopic pattern with "Bb/$Sr rati
os between 0.5 and 2.0. However, lhe scattor
n'rSr/M Sr ralios within the groups s substan
tal, and any calculanon of lsochrons would
vreld rneanrnoless results Th€re rs no obvious
;d cat,on oi;econdarv processes which wo!ld
affect the isotope system and the obssrved
sotopic scalt€r probably r€tlects a prrnary
ieature of the rocks
Rocks in the visten Lornsdal area have
less than l and initial ratios
are aeneraly bstween 0.7056 and 0 7077 Two
samples have very high trsr!6sr (VF37 and
N88-38i Table 1) and are not part of the sam€
maomatic unii. The rocks south of Tosbotn
exnloit arqer variation in rRb/6Sr ralios' and
the Srl values are beiween 0.705 and 0.708
Two sarnpLes from near Kolsvik (N87-121 and
N87-127i Table 1) are tonalitic in composition
and have fairly ow intlal ratios o1 c 0705Otherwise ihe rocks in the Oksdal Massil and
at FuglstadljeLlet are grantc with nitial ralios
between 0.706 and 0.708
The gran tes included ln this group are probably somewhatvaried expressions ofth€ same
32
qystetn Nardguten 3 Blarn Sun.lva
o.725
Fg
3
solope dagram ror rocks
i
s.u reasrern pa o{ rhe batlro.
r Data lor the Kawatnet Mon
rrre
zonle. 9ranodo,re. ioiaire tond
hlemte and porphyrlc lrante are
lrom N ssen 0936. 1933) nala ro,
|re K.ngsm.en Massr kon Pri€m
er er 11975) dala ror undrrerenla
0.720
ted g,anre ir.m rh's srudy
0.715
GRANITE
XONCSMOEN MASSIF
KAIWATNET MONZ,
GRANODIORITE
0.?05
TONAUTE
,
i
o,?ooffi
0.0
0.5
1,0
TRONDHJEMI'TE
pORpE. GRANITE
1.5
2.O
magmatc evenl. In Tos€n, a monzodiorite
which has yielded a U'Pb zircon date of 428
a 3 [4a (Nordgulon el al., in prep) is cui by
the gran te. Although ihere may be some variaiion in lhe age of the granites, this implies
that a substantial part of the 8B, including the
?.1
3.0
ihe western margin of the Reinljel lVassif disp-
lay a wide scatter n isotope ratios (Fg. 7)
wilh ntal ratos between 0.709 and 0.719
(Table 1).
granites descrbed above, is Silurian in age.
The Mosjsen area
Only a few samples hav€ b€en analysed irom
the plutons in ih s ar€a (Fig. 7). Torldbakken
& M ckelson (1986) reported a Rb-Sr date of
433 J 11 Ma (Srl = 0.7075 a 0.0002i MSWO
= 1.22) from a Sranite dyks north of Luktvatn.
The dala trom lhal study are plotr€d in Fig. 7
togeiher wilh data lrom a tonalite at Fusivatnet (northeast ol lvlosioen), and qranitoids
sampled a ong the Vefsn valley soulh ol [4osj@en (Table 1).
Although there are lew data, some f6alures
can be pointed out. Two samples from the
tonalite al Fustvatnel (N87-139 and N87-141)
ndicate an initial ratio of c. 0.705 lor this pluton. Anolher sample irorn the same pluton
(N87'140) has a very low 8'Str'Sr rato (Fig.
7) corresponding to an exvemely low intial
rauo (c. 0.701), whlch may be due to analyti
cal error. A single sample of lonalite ol the
Beinliellet Massif (N87-144) has an Srl value
ol c.0.706, and three samp es ol ioliated granite (N87 145, 146 and 147) collected aong
The southeastern part
Batholith
of the Bindal
in the southeasl part of the BB, th€re are
varlous porphyritic rocks and a fairly large
plulon of quartz monzonile (Fig- 1)- The eas
lern parl ol the area, north of Namsskogan,
is characterised by NE-SW trending, steepty
d pping bells ol variably loliated tonalites and
granodioriles separaled by zones oJ meiasupracrustal rocks. Granite and aplite dykes are
Data irom this area have previolsly been
reported by Priem ei al. (1975) and Nissen
(1986, 1988). For cornparison, the results lrom
these slud es are shown in Figs.8 and g togeth
er with some new data,
Priem el al. (1975) anatysed four samptes of
porphyrilic granodiorite from th€ Kongsmoen
Massil. Three samples referred to as aplites
were also anaysed, but there is no evidence
that the aplites are r€laied to the porphyrilic
granite. Data ior a sample ol granodiorite lrom
Stroniuh Batope canposnton 33
0.42
I ls.looedLa'lram roriwo mca
11hE srud?r and !.u'maLra
;-' h ; ,he so,i,heade n p.i or
ih. h,h.ilh rNssen 1933)
FL.
.';nLc
0.80
0.70
0.76
5
0.71
0.72
0_?0
Bindalsed was aso p!blish€d, however, lhe
Bb and Sr conlents as well as the isotope
characteristics ol this rock show lhai it be
longs to the HeiLhornet Pluton. Consequently,
ihe dale of 415 I 15 lra reported by Priem
et al. (1975) is based on dala from different
plutons and must be regarded as ncorrecl.
ln Fig. 8, the porphyritic granodiorite ol th€
Kongsmoen Massit analysed by Priem €t al.
{1975) has been plotted. An inilial ralio ol c.
0.7075 is indicai€d by the data. The analyses
publish€d by Niss€n (1986, 1988) have also
be6n compiled and plott€d on Fig.8. The rocks
termgd granodiorite, tonalite and trondhjemite
plot on a welld€finsd trend with an inilial raiio
ol c. 0.704, which is the lowesl obtained for
rocks in th€ BB. Trondhiemit€ and tonalite
span a similar range in Rb/Sr valu€s, whereas
the granodiorit€s aro gsnerally more evolved
Th6 porphyritic granit€, which occurs south
ot th6 Kalwatnst Monzonite (Fig l) has higher "Sr/"Sr ralios and yield an initial ratio of
c. 0.706- The Kalwalnst lllonzonite has even
higher ,15r/65r ratios with an initial ratio ol c.
0.7065. Throo samples of porphyritic io equi_
on the isotope diagram th€y overlap
with lhe rocks which in this study are reJerred
to as 2-mica qranile dykes (see below) The
area.
iourmaline granites from th€ western part of
ihe BB have similar Bb/Sr ratios, but significanlly higher I'Srt6Sr ratios ihan those repor
red by Nissen (1988).
Age calculations perforrned by N ssen (1986.
1988) gave the following results:
Aoo(Ma)
Fin6.$ qranodiorit€ 526
Ionaliio
Trondhiomrs
503
i
:
1o
23
493125
Porphydcgranlo 563123
Tourdalin6granlo 449151
Field re alions indicate ihat the tonalite is
the older of these (Nissen 1986) A U Pb zLrcon date oJ 437 a 4 l\,la for the lonalite (Nordoulen el al., in prepi probably represenls rhe
arvstallzanon age ol the rock. This result and
lh; substantial uncertarntres for mosl ot lhe
Rb-Sr dates, show that precise U'Pb zircon
dates are required to understand the plutonic
history ot the bathoLith.
granular granites pres€nt adjac€nl to the Kalv_
vatn€t Monzonite (data from this study) are
also plotted on Fig. 8. Two of these plot close
to th6 monzonitic rocks, whersas th€ third has
higher .rsrir6sr ratios than olher rocks in the
Two-mica granite dYkes
Nisson (1988)also published results fortou.
maline granites (Fig. 9) which have substantial
These rocks are widespread in the BB and
are generally among lhe younqest intr'rslve
phase within any aroa. They us!ally occur as
ly higher Rb/Sr ratios than other rocks in the
34
Oystetn NardgLten & Bjo.n Sundval
r€gular sheeis, and the most prominent ones
may be more lhan 100 motres wide. Locally,
the dykes are v€ry abundant, and in some
small areas lhey are the dominant rock type.
Discussion
The granites clearly cut ihe strong fabrcs
related lo D,, as defined by Thorsnes & L@
The source of the granitoids
seth (1991), but some of the dykes are lolded
by open D, structur€s. Chemical data show
thai ihe dykes ranqe n composition lrom tonalites and granodiorites wilh r€latively low Rb
and K:O, to slrong y svolved ap itic rocks with
high Rb and KIO (Nordgulen, in prep).
The Srl values, which have been catcutated
or estimated for various rock types and ptu
The rocks analysed in this study have been
collected from widely separate areas, and the
dyk€s ntrude diJferent types of plutonic and
metasedimentary rocks. Dyk€s lntruding the
TerrAkfjellet Pluion have the lowesl Bb/Sr rati
os, and these samples also show signiticani
scatler n rrsr/e Sr ratios (Fig. 9). Ono sample
(8805; Table 1) clearly plots above the vend.
The rnajorty of lhe samples yied a surprising'
ly well delin€d irend on the sotope diagram
(Fig. 9). The s ope of a line drawn through th€
poinls would correspond to an age ot c. 430
Ma with an inilial ratio of c.0.710. The granites have lower !'Sr/bsr than other rocks with
slmilar "rRb/bsr such as the tourmaline granites and the anatectc granites.
The re ativeiy coherent isotopic paflern
shown by rocks from widely scatter€d loca ilies (Fig. 9) suggests lhal an event of widespread dyke inlruslon took place at a comparative
ly late stage n the development o1 the BB.
However, desple the evolved nature ol the
granites, there are diflerences in chemistry
whch ndicate that the rocks represent the
end products oi more lhan one lractionation
seres, lt musl also be pointed out that smal
variations in age (e.9. 10-20 Ma) wou d cause
relaiiveiy minor shifts in ths'StftSr ratios.
Thus, there may be variaiions in aqe and/or
iniiial ratio wilhin the group, which are not
possible 1o resolve by the isolope data.
tons in the BB, are summarised tn Fig. 10. A
range of initial raUos wlthin a plulon is a cornmon featlre oi the bathollth. This is cornmon
in granitoids and indicates ihat processes
such as melt production, aggregation, transport, emplacement and solidiflcaton of the
magma do nol result ln an isolopically homogen€ous ntruson (Hill & Silver 1988). Each ptu
lon may thereJore preserve a record of initial
rrstbsr variation in the source, and this may
allow an assessment of the sources trom
whlch the mells were produced. Usinq this
approach, various explanalions have been
propos€d 10 explain isolopic heterogeneily in
plutons. [,1afic magmas from an upper mantte
or lower crlstal source may mix wilh
metts
from crustal rocks (€.9. DePaolo 1981, Kisiter
et a. 1986, Arakawa 1990). ll is atso ptaus b e
to explain lhe dala as a resut of rnagrnas
being produced lrom isotopicatly heterogen€ous source rocks ol crustal origin (e.9. Deniet
ei al. 1987, Hill & Silver 1988). ln addition,
high-level contam nation from partiatty metred
xenoiiths as well as interaction with ftuids
during and/or after solidification ol the p uton
may disturb the isotope sysiem.
A number of plulons in the BB contain
metas€dimentary xonolilhs in variable
amountsi however! wilh the exception ol th6
anatectic graniloids, there is no li€ld €vid€nce
to suggest significant contamination ot intrusi-
ve rocks by melts derivod lrom
x€noliths.
Generally, lhere appears to b€ no corr€latlon
bstw€en the amount of xsnoliths and isotopic
heterogen6ity.
Ths Krekfiellei Pluton is
an
oxample of an intrusion which in larg€ parts
contains abundant metas€dimentary xsnoliths
{Nordgulsn 1984, Nordgulen 6t al. 1990)_ The
relatively low and conslant Srl values (Fig. 2),
compared with rhe unitormly high ,rsrfsr ratF
os of ihe melasedimentary rocks, support th€
int€rpretation that the Sr isotops sysi€m has
not b6en significantly disturbed by incorporati-
on ot wallrock compon€nts in the magma.
Dislurbance ofthe isotope systern by s€condary ali€ration is difficult to assess- Howev€r,
th€ overallfairly fr€sh minoralogy ofthe granii-
sto n, un Eata pe canpa snian
35
ir,
r'''
/l
)./'
r
a
t.
,ll 'l
Fml
I
rl
tr1
F rTn-r7n21
I
aidl
/'"vl
Fo r0 schdmatc outlin€
rh; s[ nna Pruron rho n
or rh€
'a
p utons and rock rvpes F r
iho niria ral os aro cacu ared w lh r€sp6'rro
Bnda aaholrh (.r Fo r)showna sl.onlium inria ralos tor
ral o cotrosponds ro an aqe
orc
oids do€s not sugqesi that such procsssos
have b€en widespread. Th€ Sklinna Pluton
may provide an exception to this rul6. Sttong
sericitisation in the pluton and the indication
that the Sr isotop€ system clos€d aft€r 400
395 Ma olhsrwiso
Ma may indicai€ that the rocks have been
sub@cled lo some allerallon al a lale slage
L;w b rntermedlale initial raios (0704_
0.710) predomrnate and ar€ presont in a wrds
vanety of rock types throuqhoul lh€ balholith
36
Ovstetn Nardqute^ & Bja.n Sundval
0
o-75
o,7
4
TOURMALINE GRANITES
PONPII, GRANITES
ANATECTIC QRANITOIDS
METASEDIMENTATY ROCKS
TTO-MICA GRANITOIDS
IIEILHORNET PLUTON
SKIJNNA PI,UTON
0.?3
gA
o.72
o.7l
0.?0
VARIOUS GRANITOIDS
0.69
o.ooo
0.005
o.ol5
0.010
o.o20
0.025
1/sr
FQlrSlronlumniarraiosbasedonanageor!40MaplouedaqanrrIS,Sampe5komFUronsandro.lrypeswh.h
a,anolspecred nrhe eoend pol nrherenbbered vanous o,ai
(1936 1933) but not lhose or P,em el
a.
rod. rhsarso'n.ludesih€datapub
(1975)
(Fig. 10). Most of lhes€ rocks have rslativoly
high Sr contents, and th€y plot within a small
field in Fig. 11. Within this group, some plutons have constant or narrow ranges in Srl
values- Thess have comparatively low Srl (0.
704-0.705), and some oi them exhibit considerable chsmical and p€trographic variation. The
chernical and isotopic characteristics Jor the
plutons would be compalible wilh diflerentiali
on ol isotopically lairly homogeneous magmas
derived from a mafic to intermediate upper
mantl€ to lower crustal source.
The plutons with Srl values b€twe€n 0.705
and 0.710 (Fig. 11) comprise several rock types which exhibit variable d€grees of isotopic
heterogeneity. R€presentativ€ samples from a
numbor of plutons have €Nd < -2 and fairly
radiog€nic feldspar Pb (Birkeland el al-, in
press). The source r€gions lor lhsse rocks
ar€ difficult to assess and may include upper
mantl€ and various crustals sourcss Lower
crusial materials with relatively short crustal
residence times are also a potenlial sourcei
lherefore, an entirely crustal origin
lor
the
rocks cannot be ruled oul. A similar argument
can also be mad€ for the lonalit€s and granodiorites that have low Srl values. However, a
signficant sub-crustal inpul may appsar more
likely in such cases.
The gabbros and dioritss in the Velfiord
Ursfjord area generally have lowto interm€dia
ts Srl (0-7057 - 0.7071), whersas higher valu€s
(Srl
>
0.708)are present in soms rocks occuF
ring west ol Velfiord (Fig 4). Generally, the
geochemistry ol these rocks would r€quire
an upper manlls or lower crustal mafic source
with a variable crustal contribution.
The late granitoid dykes constitute a diverse
Slronttun tsotope canposnion 37
group of rocks with highly variable ab/Sr ratios {Fig.9). They intrude differ€nt types ol
granitoid and metasedimentary rocks, but, the
re s no clear relalionship between the isotope
composition of the dykes and the r host. Thus,
it would seem that the genoration of these
dykes is nol generally relaied to the pevogene-
sis of the granitoid in which they occur. The
dykes hav€ clearly lower rrsr/bsr ratios than
the metasedimentary rocks, and although ol
h€r isolope data are not availabe there is no
indication that they were generaied by upper
crustal melting. The sources for ihe rocks are
probably varied and sinrilar to those ol other
tonaltic to granitic rocks in the BB.
F€latively non-radlogenic sources are aso
suggesl€d tor lhe Heilhornst and sklinna Plutons (Fig- 1l ). The apparenl negaiive trend lor
the Sklinna Pluton indlcates that the age used
to ca culate the initialratios may be too young.
ln ih6 BB, a wide range ln Srl is especially
pronounced in the anateciic granitoids and the
tourmaine granites (Fig 11). Fi€ld evidence
suggests thai at least some of lhe anatectic
rocks are a resull of local mellinq of melasedi
mentary rocks. The rocks have overall high
Srl and low €Nd values which are cons stent
with a predominantLy crustal origin (B rkeland
et al. in press). ln Fig. 11, varable
mixing
between two components with d iierenl initial
ratios will produce inear trends between the
end menbers. Anatectic granitoids overlap
with most of the samples of metasedinleniary
rocks, suggestng that they were generated
by mixing ofcomponents from a highly radioge_
nic crusta source and a less radiogenic, pos
siby lower
crustal/manlle source (Fig. 11).
Some sampies of the metasedimenlary rocks
overlap with a broad array defined by the lour
maline granites. Again, the lr€nd may be explained by mixing a radiogenic and a nonendradlogenic source. The rad ogen
member for the tourmaline granites, however,
ls distinct from and less radiogenic than that
of the anatoctic rocks. The porphyrilic graniles
(Fig. 11), which occur togethor wilh maiic to
c
lntermediate plutons in the Velfjord disvct,
also have a high Srl indicativ€ of a strong
iniluence from radiogenic sources. Metasedi_
mentary rocks within the HNc, or equiva ent
rocks at depth, which have Rb/Sr and !'Sr/ksr
ralios similar to the granitoids, would provide
a poteniial source lithology lor the graniloids
with high Srl.
lsotope daia (Rb Sr, Sm-Nd and Pb Pb in
feldspars) lrom
a
series
of
representative
samples oi the BB show thatthe rocks originated lrom multiple sources including fairly deple
ted mantle to lower cruslal rocks, enriched
upper crust, and two lypes of Th enrched,
probably ower crustal rocks (Birkeland et al.,
in press). The Sr isolope data presented here
show that most of ihe batholith has Srl
<0.71; however, a number of putons have
hiqher Srl values relleciing a slrong inlluence
from radogenlc crustal rocks. Of parlicular
inl€rest is the heterogeneous nature of lhe
radiogenic sor.rrce (Fig. 11). Th s leature was
not apparent from the sludy by Birkeland el
al. (in press). Thus, the comprehensive study
of the Si isolope variaton has led to an improved undersiandjng ol the complexily involved
in the petrogenesis o1 the BB.
To summariso, mslling ol h6t6rog6neous
source rsgions and/or mixing oJ m€lts d€rived
in variable proportions trom isotopically difterent crusial and sub-crustal sources may accounl for th€ variability in Sr isotopes of ihe
BB, Contamination at the l€v€l ol emplac€m€nl as w6ll as s€condary alteration appears
to b€otlimii€d imponanc€, and isotopic h€t€ro'
gen€ity within and b€iweon plutons and rock
types is thought lo rell€cl the varied natur€
of tho source rocks.
Geographic variation in initial osr/ssr
ratios
Most of ihs granitoids in th€ Eindal Batholiih
hav€ Rb/Sr ratios < 1.0- The excoptions ar€
the tourmalin€-granites in Bindal, the Sklinna
Pluton, mosl of the H€ilhornet Pluton, and th€
majority of the 2-mica granii€ dykes. Mosl of
lhes6 also hav€ high or Jairly high initial Sr
ratios. The anatectic granit€s may have Rb/Sr
< 1.0 though th€ initial ratios are high. Som6
intrusions (€.9. ths Krekfjollet Pluton) have
very low Bb/Sr ratios, but most of th€ rocks
have ratios in the rang€ 0-2 - 1-0.
Fig. 10 shows how variation in Srl valu€s
r6latoto g€ographic positjon. Most ot the rocks
wilh low Srl
(<
0.705) occur in the €astern
part of the batholith. Rocks with intermodiate
!nilial ratios {0.705 ' 0.708) are common through'
out the batholith and includ€ the mafic to inter-
mediate plltons in the V€lfjord and Ursfjord
areas. The hiqhesi valuss (Srl > 0.715) are
3A
Oystetn No.dguten & Blatn Sun.tvolt
repr€sented by tourmalin€-granil€s and analectic graniles in lhe w€st.
These resulls may constrain the models Jor
Calsdonian magmatisrn in Norway. lsotopic
polarily is a {eature of some, but not allexamples of documented Phanerozoic subduction/
volcanic arc r€lal€d plutonism. Where polarily
€xists, it g€nsrally shows an increase lrom low
valu€s
at th€ conlinenlal margin to
higher
values in th€ continental hintsfland (Kistler &
generally low in tial rsr/ssr ralios. lntermedia-
t€ and
variable iniiia ratios are present in
severa plutons occurring in most parts oJ the
balhoilh. Tourmaline graniles and anatectic
granites with th€ high€st initial ratios are located in the westorn pa of the batholith. lnterpreling the daia in terms of a subduction related sefiing, the geographic distrbution of initial ,Sr/rsr ratios would ndicate that the conli
nent lay to the west during the tim€ of pluto'
Peterman 1973. Farmer & D€Paolo 1983, Liew
& Hofmann 1988. Arakawa 1990). Assumlnq
a destructive plate margin setting, th€ pattern
oi initial sr values now eslabllshed lor the
8B would indicate that th€ continental hinler_
land lay to the wesl at ths time oi plutonism.
uppod rron rhe Goorogica
ol Nomay and lrom prolecl MT002020343 (Oi€s
gdoniai
aled
willi
Balholrhs)
runded by lho Nor
assod
Ca
w6aancounc rorsci€nrilicandrndustria R6s6arch(NrNF)
we are ndebled to B€nle Kiosn€s (Trondhem)lor prepa
Surv€y
Engd (oso)lor xFF.analys€s, and to
Conclusions
The stront um sotope chemislry
Acknowledgements
Ast
Hemmne and
Bjors svendgerd (rrondhe m) ro. dran n9 somo ol lh€ lisu
r6s critca commonis lrom John cobbing. P6r6r h€n.
Davd Rob€ns anli Brian Slun sgnilicanty improved tho
oflhe
Bindal
Batholith has be6n invesligated. The maflc
intrusions must have a mafic source ln ths
and Forr
B Pedorsenlorllreirr€view comments and suAqes
upper mantl€ lo lower crust, allhough the initial ratos oJ the invesligated rocks (0.7050.707) indicai€ significant influ€nce from isoto
picaly €volved mal€rial in th€ source region.
For some plutons having more evolv€d compo-
sitions and fairly low inilial rlstssr ratios (c.
0.704), the upper mantle io lower crusl would
bs the most likely sourco region. Graniloids
with hgher inilial ratios (0.705'0.710) would
require an increasingly stronger crustal inJluence- The lourmaline granites and anatectic
graniles with high or very high initial ratios (>
0.715) may be oJ enlir€ly cruslal origin, and
the data suqgest that two lypos ol radiogenic
crustal rocks contributed 10 the magmas. There is lilllo evidence oJ high_level contamination, and signilicant s€condary alleration oi the
granitoids is obsetued in very few cases. The
varied nalure of the Sr isotops data are gene_
raLly lnterpret€d lo r€flect differ€nces in relali
ve input from source rocks with variable Rb/Sr-
ratios and isotope composton.
Due io the isotopic heteroqeneity generally
observed in lhe BB, lt is vi(ually impossibe
ro obtain meaningiul dales using Rb_Sr wholerock isochrons. This emphasizes the need lor
precise u Pb dates in the study of the granito'
ds.
lntrusions in the southeastern part oJ the
batholith have conslani or narrow ranges ol
References
ArakawaY r990: Srronnuh solop c compositon or Meso
zo. lran r c rocks n the H da lrell cenlra Japan d ver
sles ol magma sources and processes or magma
ma.gtn area Lnhos 21
261.273
Ban! N. 1935 the slratrgraphy and stuctuat devetapnent
ot the Raday H1ttay arca att6t vqtsntad onpoht
Un
versrY or B€rq€n Norway.
Banes CG.. Prosrvk,T. Nordguon O & Barnes M A 1992:
Goo ogy or three d oritc p ulons n ve rlord Nord and
Nat geat untterc Brtt. 123, 41 54
BrkerandA NordguonO CummiigGC & BlorykkeA
0n press) Pb-Nd.sr sotopic constants on lhe orgn
ceita
Norway. Lnhos
Branl.B Torudbakken B & Ramb€rq.r.e 1932r Feseting
or a Fb.sr lotaL rock syst6m n ih€ Bo!ii9srrsl€r Nap
ps
Compex. Nordand. Norlrr Notuay Nor Geo,
rrtsskt 62
219.22a
ChapF€lBw & Whie.AJ R 1974: Twocont,astng grante
tYpe. Pac Geat 3, 173-114
oener.c vida P:Fernand€z,A LeFod.P & PeucatJJ
rssT: lsoiopc srudy ot ihe rianasu qranire (Hmaaya,
N6Da) nr€rences on rhe aqe aid sourc€ ol N malayan
er.agtantes cantib. Minetat Petot 96 7492
D€Paoo.DJ 193r A neodymufl and stronium sotopc
siudy oi lh€ Mesozoic da c a ka ino qraniic batho ths
orlh€ Sera Nevada and P€nnsuar ranges cailorn'a
J. Geophys Bes 36 1047010433
Sttantun isata1e con1asttan 39
L & DePaoo.DJ 1933 Ongn or Mesozo'c and
Teddry grante n wesl€rn Unned srares and mp'cal'
on r.r pre Mesosoic crustal stuctur€ 1 Nd and sr
sorooc sludl€s n th€ qooclne or nortlrern Great Ba
sn J G€oPhYs F6s aA $79 340r'
Farme,.G
Gee.DG Kumpulanon.F. Robarts.D
Stephsns M B
1935 Tecronostal oraph c
Map. scare 12 000 000 /, Gee,oG & StudBA
leds): Ihe CaletJanide Orcgen Scandlnavia and Fata
red /
J W'ey a
o33
/aas
...,"..o.v
Sons
Lid
Chch€ster
o - ,0000
bedrockgeoogLcalmap No, geat unde6 skt 1'42
Guslavson.M & Preslv'kT 1979: The gneous comper ol
Honaver Nord Trondeag. centra Norwav No. geo'
F,q & La'-l ro33 d d o
3 Coistants on ciusra maqma chambe'
1 1gA7: Statigtah og stttktuQit
tao\ \.. ta. B aafa) \. no
Ne da
L
utwktrhg
'
process€s
saurchan'
,, 257 275
dpp4Bw o6-D 3adP1.nolo3q
Norwav L/hos
hr setra
Nevada.
cailorna cantib Mtneftt Pet.t
K'sler.FW a Peleman.zE 1973 Vdalons n Sr'
Fb.
'rSrr'"Sr in Mesozo c aranrc rocks and
n centra Calrorna Gdor Soc /4n
B,/r 3r 3439.3512
l<o unq s. 1967 Geo oc'ske undersoke sel dei 5or a€
llerlerand o! nord'96 Namda Not geat undets 254
K. Na and
'he
92111 ltn PFr)
N dreno Ande6enTB sGaulnebH 1933 G'anrads
O, no rn' n ih€ Norweqan Ca odondes
'n-.o.po
"
4sso. at canada Mrctdt asso'
A re!ew 6e.r
Annuat Meeting: Ptagran nh absta'tsl
StJahn s. Ne||louhdtand Mav 19AA F A91
N.rdaulen.O & Be,'nq D 1937 AUSTFA b€rql unnsra'r
ot canada
r;25
2 I 50 oo0
lo,cop'q uiqale Naoe'qeatastste
Nodaueno 3 M(Lh€ JG lq33 [enrarl€nfe loNne
B.da cenra
;--nFl
Noroeqan caedon'dcs
"
BDtt 413 5160
Not geot urderc
Nor.louen O
l1-,:l tromer
&
Schooenboro
Pl,bn no
h
B
1990:
cenlralNoMav georogicals€r
rno radofl6tcaqeand mp carions lor rha Scand'iavr
an caedond€s J qeat so. London 147 439 450
No'douipnO Thocne\T 3 HusmoT 1939 TEFBAI
b;rqq'unnsrari r325 r r to ooo iorcropq urgaJe
N.tses aeaiaeske uhdarcaketse
pub cand.scienl tlresis universitvoraergon 293pp
rano
.b,en s B & Fpd \. rc 3. Fb t o opd )
rocks, Konasbers sector soulh
h5re'P\^
N.rdoul6no 1992 A summarv ol the pstographv and
Bnd? Balholrh No' qeor !'
g-"o"n"..nr ot
nia
H.N A Boarrjk N A M. Hebeda E H verdurmen E.
AIh & VerschureRH 197s: Lsoropic daln9 or rhe
Prem
caLedonan Brndal and Svennngdal Orant'c mass{s
centra NoMaY No, geat Mderc 319 2936
Rns F & Fambe.g.lB 1931 ltre iJppemost A och|ron
ihe Rod'nqs{ielet and HeLg€and NapFe conpeies 'n
a seAmenr souih or Ranallorden Norwav leu, Cogn!
sleoer.F H & J:iqer E. r977: SubcommssLon on qe.chro
tt" use or decav 'onstants 'n
"""qv -*orc" Eadh Ptanet sct Le 36
g€o and cosmochronoogv
Thessen.FJ 1936: En petrctagsk .g stLktuQeataa'sk
lndersaketse av Betnrell ahta.tet Nadtand 0^pr6t
oslo. Norwav. 279pp
Thorsnes.T 1935r fhe tectanostangraphtcat devetapnent
the Natdrettna* atea. s Naldlard lipub cand
scem rhesLs universrty ol Berqen. Norwav 223pp
ot
Mrds nt Petat 93 129 13a
tectanasttatio,aphl and stLctutai
deveiapnlent at the Nevemes a,ea vettiatd rnprr
a
Nd;id srsruiy co,rrrb
ros.ihn 1935 Ihe
Un'versity
v,,cdF
N'ssen A
9
L
ve{p'o
'3
or Berqei. NoNaY
00000
1936 RbiSr age dei6rm nat.n
\o'
ve10,d.Tosen r€son 50ulrrwPsrern par or !he N€9e
oP'
ot nlrusrvs rocks
pad ot ih€ Bindai massl Nord
Trondeag.No&ay Nd. geo' undets BDn 406 A3 92
Nssei A L 1933: Aldersbgslemmelse av dvpb€roar1er en'r
Rbisr meroden den sor 9e der av Bndasmassvet
\o
o
T'o oodq 09 No'oc
Thorsn€sT 1937 Tecronom€lamorprric and rgclonostat0
raphc devoopmenr ot the soulhwesrern pad or rhe
H6rceandNappecompre c6nl a Norw€qDncar€don
d.s ceor Fo.€n Sta.th Fath 109 f64 J61
rh.rsnes T & Loserh H 1991 leclonoslrat qraphv n rhe
d
Rappad nt $ aas
N6'..uenO 1934 1. ocabl\ d-a erptd P." at
trP
N.t .c.t h11e6 But 121,114
B & Ranberq B 1e32
rorudbakien
dersokelse
'
En Fb sr sotopun
VeldaqrupFen Beiarn Nord and Georog
r",uio,xt"n eo. &
Mckeson
M
1936 A Rbisr srudv
Nappe compex and
'dnomeranorPh c evenis
udrm Lhe LrppsmG' Ar(rrihon Ccnka S.andnavan
.ipdondps N.rlav Nor ced/ 7)dssrt 06 263 270
lrom re
Moslo€n untr. Helaea
rpD dd
s,;".r%J^d{",
rea ;66 lirerew or Bdlrei Norway.433PP
Manuscript rcceivad April 1992; revised typescript June 1992; accepted June 1992'