,
z
/ >./
ollprinr NGU Burletin 423, 41-54
CALVIN G. BARNES, TOFIE PRESryIK.
OYSTEIN NOBOGULEN & MELANIE A. BARNES
Geology of three dioritic plutons
in Velfjord, Nordland
Trondheim 1992
,
Geology of three dioritic plutons in Velfiord,
Nordland
CALV N
G
BARNES, TOBE PFESTVIK. OYSTE N NORDGULEN & MELANIE
A
BARNES
BarnosCG, Pr€stvik,T., Nordguen,o &Bah6s M.A 1992 Gooogv or three diorilic prutons 'n
V€lord. Nordrand Not g6ot und'rc Butt 423 4154
po ites or lrr0
Dionric p utons in th6 v€ flord at€a of Nordland intruds calc's lcatss and m gnarit c
\F\c, rh€ r'6€ ra qer pLon
." r"
h s
e to^a'd € p on'
r.
i-* -.*.
^h
"'
,.",-" o., rnd g anr' ooo'€< 4sr€ dpro _6d 4f' n 6'rr" ner o'€.ca do'o'rrr
ondton'Sr-'
a." q, -*q. q
t-*
..."
i"*"lo w-"."-pt*
s-i,--.-
ol dolormarion, and asymmorric zoning ol the pulons are conss
5,nEt,al shoar zon€
]m -m.".-r
vaiable majo.olen€nt
* rr"-"ni"*rc'r
*r"*"'-"'.'.."oi"arci
aio,irc. aru
Puoncon!'Fo
contonts and a vounqor unl thal s asvmmet'calv zoned iiom monzodon_
rhe e)ou'ast o!r<a' pav"rI
loiaron (loca
ter.s€r or6v )prulon is d slinsuishod bv profr n6nt I ow
aparilo h has
"en*
rv stonq y d€idm€d), cm{me paqlocaso phenocrvsts and abundanl oxdes and
loMrVorvor€rr
a€ o'dlv 5gh€ TO. ano roh'Ih'a'q'onar7€oCo'o_d 'lco(s
j*
' 7o-od F ro w or p! '€ o do'i6 ro
'"-'i"". -". ar,
",**
ror r ro rS - e ol ro ! o'e d<r4' o1
rne r... o'or pr'rcth€ ooralumnous anat€ctc qran i€s, whos€ Al,o, Na,o and REE abundances sugaosr an orqin bv
ho.' o.. ceo- €Trd.d16o €. b€rwe.n c!6 oo ouon
. , , . *",r .at* o ,
"n.
'uoou"i't''p.u't.'."q^o'orpo.'on'\a''6a.oTo.€p
,ni"pr,ro* n"0.." t"" -" parontalmagma. and thal6ach masma iolowed a d'slnct dilreren-
G. Bames & Metahie A Bahos Depatudt ol Geosden'es r6'as Iech Uhretsrv Lub
h.at Texas 7 A9. USA
f.G P@stvik. Debaftneot ot G6ato9Y a Mrnaal ResaLrcas Engineering Notwegao tnstt'ta at
Catvrn
TochhatagY, N 7034 frcndhem NaNaY
NaNar
Oyst6'n Nordguten Gealagtdi SuNey at NaNav P o B.x 3a06 N-7002 rtondhein,
lntroduction
Ihe Bindal Batholith
one ol
tc rocks ot the balho ilh, the tempo'
ral and petroloqic relations between them are
ry 1o gran
the
r€presents
laroest occurrenc€s of granitic magmatsm n
tne'ltorwegian Caledonides (Stephens et al
1985). Most plulons in the batholith are tonalitrc to oranitic rn composrtion; however, sparse
lo dioftc bodres are widespread
q,Torudbakl.en 8 N4ick€lson 1986) E amp
les ol dioritic magmatism in the province are
provided by plutons oi th€ Velljord massils
oabbr;rc
i;
(Kollung 1967), which occupy a central position
in the batholith (Fig. 1). These plutons range
fron olivine qabbro to biotite-quarlz mon
zoniie, but are predominanily dioritic to mon"
zodioritic in comoosltion. Although ihe relatively malic Velfjord pLutons are in close proxim -
not well known. For this reason, we have
undertaken a detailed study 01 the pelrogene
sis oi the three largest plutons in the aroa,
which are herein inlormally referred to as th€
Velljord putons, and their possible re ations
to the batho ilh as a whole.
ln th s contribulion, we reporl on lhe field
relations, zon ng pattorns, and petrographic
characlerisiics of the VelJjord plutons aong
with a reconnaissance geochomica study. Th€
dala suggest that oach oi the plutons is inter
naly complex, and thal each is peirogenetcal_
y distinct fron the oth€rs and lrom granilic
rocks 01 the aindal Balholiih.
I
42
CalvtnG Barnes,Tote Prestvik. Oystetn Nardgulen
A Barnes
& Melanie
Geologic setting
The plutons ar6 ntr!sive into metasedimentary rocks oi the Helgeland Nappe Complex
(HNC) of ihe Uppermost Alocthon (Stephens
et al 1985). They occupy a part of the HNc
where the regional strike is NNW-SSE. This
is dstncl frorn the Bindal area to the south
and the area north of Velsnljord (north of
Ve lord), where a NE SW slrike is more iypi
cal. A subhorizontal lineation is cornmon ln
granitic and rnelamorphic rocks n the zones
wilh NE SW sv k€ but is less pronounced in
the zone with NNW-SSE strike.
ln the Veltjord area, HNC rocks comprise
three thrusl sh€ets separated by east- to northeast-dippinq laults (Thorsnes & Loseih 1991)
x
The lowest sheel is host to the plutons and
cons sts ofvariably m gmatilic quartzofeldspal
hc schist and gne ss, cac si!icate schist, and
rnarble. These rocks are within the siliman te
zone ([,4yrand 1972). The middle sheei con
slslsoi basalmaf
c and ultrarnafic rocks t]ncon-
iormably overain by melamorphosed clastc
and ca c-silcaie rocks.The uppersheel is lthologicaly similar to the ower one (Thorsnes &
Loseth 1991).
irynand (1S72) and Kollunq (1967) inlerpreted the pluions to postdate 01 detormatlon
because or struclures n the wall rocks are
dellecred by the plutons and because the
wall rocks dspay a pronouncad increase in
metamorphic grade near the intrusions (see
be owi Myrland 1972). fi,4oreover, Thorsnes &
Loseth (1991) suggestod that thrustng wiihln
the HNC was related to D, and that ihrustinq
occlrred before ntrusion of ihe Velfjord plu_
rons (also see Bucher Nurmnen 1988) Ihis
conclusion is supportsd by ntrusive relations
of a srnal dlortic body nrmediately to the
easr of the sausfiellet p uton (the MarkaJjellet
n
.."". ..-
: :l 6'h @F <r@6E
d
[:-_t ,&4 6dn,,4
F
q1
Feg
re Varrord
c io
ona geo 09. set ig sh.w n! the o.aton or
pul.ns wrhn rhe Bnda eaihorrh The qabbro
9,anlc Purons or rhe ba ro
{io.mamenlloi ur€ uppermosi arochihon. whch
n lh6 regon comp,ses re H€qeaid Nappe compex
IHNCl aid rhe Fodngsirer6l Nappe comprei lRNc)
ry rocks
between th€ Velfjord plutons and graniiic rocks
of the Bindal Baiholth. such probems empha-
size the need for pr€cise radiometric dating
of the units (n progress).
pllton ol Kollung 1967) that cuts la!lts betwe_
en the lower, rniddle, and upper thrust sheels
(Thorsnes & Loseth 1991). li ths pluton be'
ongs io the same magmatic event as the
Velfiord plutons, then Velliord rnagmatism
The Velfjord plutons
occurred atler thrust ng.
General Contact Relations
The putons oi the Velfjord area have nol
been formaly named; therefore, for eas€ ol
d scusslon, the large plutons are referr€d lo
rnrruded by g.an tc orhes. Howev€r. manv o'
tne qrdn tc roc<s trat rrlrude lhe Velflord plL_
fjeler pluton, the Aks€lDrevli pluton, and the
Sausljelet pluton. A small monzonitic body
Kol ung (1967) inlerpreted the Ve ijord mas_
sif lo be older lhan granitic rocks of the Bin
da Batholith becalse the velfiord rocks are
tons are compositonally distinct lrom, and
rnay nor oe re ared lo the nearby Biloa glarr
tes (see below). Thus, we suspect that th€re
are 10 unFqu voca cross cud'ng realio4s
informa ly, from north to soulh, as the Hilstad-
that crops out near Aunel, easi ot Hommelsto
(Fig. 2), is called the Aunet monzoniie.
The contacts between the p utons and iheir
wa I rocks generally d splay sleep to moderate
I
Gealoay of thtee diontrc
dips. An exception to thrs is apparent along
the northern coniact ol th€ AkselDr€vli puton, where sil-like apophyses of the puton
inlrude wall rocks rn the Hommelsto area.
Contacts with marble and ca c silcate schists
are generaly rath€r sharp, allhough in many
localtes coniacls are marked by a seres of
diorilic dikes that become more abundani as
lhe pluton is approached. ln some loca ilies
the grain size of ihe p utonic rocks decreases
Conlacts
wth mgmatilic pelitic rocks
are
generally marked by zones of heterogeneous,
equ granular io porphyrilic, garnet- and sillimanite-bearng granite (Figs. 2 and 3). These
zones range lrom a t€w m€lers to as much
as 300 m wde, e.9., along the southorn con
tacl of the Akset-Drevli pluton (Fig. 2). ln genera, these granilic bod es are gradational outward inio dial€ciic rocks and then into migrnalilic gne ss. Where intrusive relalions were
observed, the coniaci granir€s ar€ inlrusive
into the Velfiord putons. N6ar Lsjsen, along
the eastern border ol the Hillstadfjellet pluton,
the graniles are separated lrom qlarlz monzonitic rocks of the pluton by a zone of garnet-bear ng quartz d oril€.
Dlutans 43
ocase, to gran-size reduction and recrystallizalion along grain boundaries and, ocally, 10
deleopment of protomylonitrc iabrics with
porphyroclaslic textures and rare ribbon quartz. Deformation s typically more pronounced
n the outer parls ol ihe plutons. Most late
felsic d kes are undeformed or weakly deformed, but some display stronger deiormauon
than their hosl dioritic rocks.
A wide range of rninerals were stable dunng
d€tormaton. ln some insiancos. d€formation
occurred in the stabiity field of plaqioclase,
c inopyroxene (cpx), and onhopyroxene (opx)i
with undeformed or weakly delormed late
magmatic biotite and amphibole, ln other cases, biotte and actinolitic amphibole (after
pyrox€ne) wero ths slable maJic phas€s. Defor'
mation also encompassed the lower-tempera-
t!re assemblage biolile, epidote, sodic p agiocase, and quartz. This p€lrographlc evidenc€
rndicaies lhat delormaton began when th€
pluions conlained a melt phase and cont nued
during cooling to g reen schisl-facies cond tions.
The granitic rocks at the rnargins ol the
putons record a similar history ot deformation. Their tectonic fabrics are lyplcally better
d€veloped thanthose in the adjacent plutons.
Contacl relations beiween the Fllllsradfjeller,
Akset Orevl , and Aunet bodies were observed
in the area east of Homnlelsto. Diorltc rocks
ol lhe Akset-Drevli plulon and ol the lirst intrusive sl3ge oJ the Hillstadfjellet pluton are intru
ded by porphyrtic diorii€ of lhe second stage
of the Hillstadfjelei p uton. Dikes of lhe Aunet
monzonite cut all lhree
!nts.
cross-cutling
re alions between the first stage olthe Hilstadfjellet p uton and ihe Aksei Drev i pluton were
not observed. The r€laiive timing of lntrusion
of the sausljellet pluion is unknown.
All three p utons and some contact granites
are cut by rnedium- to fine-grained felsic dikes
lhat range in composition from tonalitic to
graniiic. They average about one meter n
wdth and typicaly carry biotite or biotite +
rnuscovite. Malic d k€s (microgabbro lo coar
se grained gabbro and diorite) w€re observ€d
Zoning and lnternal Structures
Hilstadfjelet ptuton
Th€ rocks of lhis pluton are genera ly massive
or weakly loliated. The pluton contains seve
ral arge
metasedimenlary screens (Fig. 2),
metasedimeniary xeno iihs thal range trom cm
to s€v€ra tens ot meiers n size. and
rare
peridottc xenoliths. The frst ntrusve staqe
is represented by a gabbroic to diorilic body
exposed in the northeastern part of lhe pluton
(Fig. 2). The second stage ranges in composi
lion from monzodiorile (with rare diorte) to
quariz monzonite. This ufii is asymmetrically
zoned. wilh the most maiic rocks in the western and southern parisofthe intrusion, quarlzrich rocks in the easl (between the larqe meta-
Defomation
sedimentary screens and rocks ot the firsl
stage), and monzon tc rocks in the north and
between the mafic rocks and the quartz rich
ones (Fg. 2). BelaUve inlrusive relationships
are demonstrated by lhe inclusion of angu ar
All of the Velljord plulons show evidence of
xenoliihs of firsl-stage rocks in the second
delormation. The degree oi deiormation gra-
siage.
The primary malic minerals in the first-stage
rocks were cpx, opx, and hornblende. ln lhe
in althree plltons.
des trom minor bend ng of plagioclase, through
deveopment ol subgrains in quarlz and p agi
I
44
Catvin
Fq 2
G Barnes, fore P.estvik, Ovstein Notdautoh
& Melanie A. Bames
Geo oqy ot the H rrstadtj€ r€l and Aks€r Drevlip utons The numbe's 1 and 2
ndrate rhe ocatons or sraaes
1 and 2
or
a
Geolaqy althtee diatitic
plutons
45
N
.tt
tl
.;i
t
/..:.
Sausfjellet
.
-- i., , ./1--^' -'
Fq
3. Georoqy ol Ih€ Sauslerei pruron symbors as in FQ.2
second stage, primary cpx, opx, and biotite
3 cm ln maximum dimension) thal commonly
in lhe malic western rocks give way to the
east to cpx + opx + blotite + hornblende, lhen
botit€ + hornblende, then biotite. These relatons have been obscured by r€crysiallization
at lower temperatures, pa iculary in zones
def ne a welldeveloped loliation. This folialion
was originaly magmatic, bul has been warped
and lold€d in zones of high stran (Fig. 4d).
Some samples display high-temperature deformation n which plagioclase crystals have been
of high stran (compare Figs. 4a and 4b).
bent by up to 60".
Aksel-Drevli pluton
This pluton is predominantly dioritic, but conta,
ins mlnor rnonzodiorte and monzonite, especlally in its northern parts. The typical primary
localy abundanl in the pluton, and some of
the calc-silcate xenolths contain cr rich grossular garnet (Prestvik, 1974). Two peridotite
xenolths (< 250 m) crop out in the western
cally, especia ly in samples frorn the southeas
tern part ol lhe pluton (Fiq. 4c).
The Akset-Drevli p uton is characterized by
abundani, arge plagiocase phenocrysts (2 to
This plulon ls predominanlly dioritic, bulconiains sparse quartz diorite and quartz monzodiorite in ils southwesi€rn pa( (Fig. 3). A
[,1etas6d mentary screens and xenoliths are
matic assemblage is cpx, opx, and botte
(aamphiboe)t however, oivine ls presenl lo-
a
46
CalvnG Barnes, fore Prestwk, qystet. NadqLten 3 Metante A Bahes
_. ..1
,r'l,m:
i
,.,""",1
.,/
.
Yl:r:l.'l/
-r.
'..%r..
:,i.i
')
,:l:ll::.
1l:l:::l
i
o; D o€'o r.',
|re sausrerer puioi F Delormalon pateris n
pronounced asymmetric zonalion is d splayed
by the prmary matic assemblages (Fig. 4e),
whch range from cpx and opx in the east,
throuqh a central zone of cpx, opx, and bioii'
te, to cpx, opx, biolite, and amphibole n the
southwest. Samples colected near conlacts
are generally the only ones lo show appreciab
le deformaton (Fg. 4f) and they commonly
contain the subsolidus maJic assemblage ol
amph boe and biotte.
Magmatic foliation is cornmon Ln Sausilellet
samples, as is schileren bandinq. On Sausfjel
let, bocks of schlieren'banded diorite:'100 m
across are surrounded by weakly banded to
masslve diorte The presence of the blocks
suggests an early h story dunng whch the
bandinq formed alonq the plulon s margins by
flow segreqaton, fo owed by stoping ol the
blocks durnq ihe linal slages ol lniruson.
Petrography
Petrographic descriptons are based on inspeciion of over 450 thin sections. Where ciled,
rhe sausrle €r
Ltr.ar.cdp.o'
pul.n
plagocase, alkai ieldspar, and amphboe
compostons were deterrnined by eleclron
microprobe analysis (C. Barnes and T. Preslvk, unpubl. data).
Fkst stage gabbro and d orite of the Hi lstad
ljellet pluton display re ict hypidiomorph c gra
nular rexture thal is now partly to completely
recrystallzed by granulatjon and locai mylonili'
zation. Primary cpx, opx, polkilitic brown cal'
cic amphibole, and reddish brown botle are
variably altered 1o aclinolitic amphibole and
chlorile. Epidote has parlly replaced plag oc a
se. Apai'ie, ilmente, maqnetite, and chal
copyrte are accessory minerals.
Second-stage rocks have var ably delormed
hypdiomorph c granular texture. From soulhwest to norlheasl. the rocks become more
porphyrtic (plaqocase) and the grain size ol
th€ groundmass decreases s ightly. Plagiocla
se (An.-An,,) is normally zoned and is typical
y resorbed and nmmed by microclne. Quariz,
where presenl, is nterstitial. in lhe easl defor-
med monzodioritic samples, pyroxenes are
rrnmed by oive-qreen edentc amphibole. ln
,
Geolagy al thtee d@tittc
monzonitic rocks only relicl pyroxene is present and olive'green ed€nilic amphjbole is rim_
med by a blue-green ferro-edenile Accessory
minerals ar€ apatite, allanite, zircon, ilmenite,
magnetite, chalcopyrile, pyrit€, sphene, and
The large plagioclase phenocrysls (Ani
An") n the Akset Orev| pLuton nol only defrne
the iabric blt conlrol th€ textural relations
Some cpx and opx grains are euhedral and,
along with anhedral, pyroxene-rimmed olivine,
are best described as intergranular' The
pyroxenes are also present as rnlerst tial mine
rals alonq with reddish-brown biolile relalive
ly abundant o\des. and mm scale prlsmatic
apaiie. Pnmary pargasihc amphibole s rare
in this plLion; il occurs as rims on pyroxenes.
Microcline is pr€se nt interstitially and n resorpiion channeLs in plagioclasei quarlz is interstiti
al. Alonq with tho aforementjoned apatit€,
accessory mineras are ilmenite, magnetite,
plutons
47
Soms contain accessory amphibole {ferroan
parqasrtlc hornblende), allanile, aparjte zircon,
sphene, opaque m nerals. and epldote Olhers
contain assernb aqss typrcaloi slrongly peralu
mrnous granrtes, wrth muscovrle, garnet and
accessory prismatic slllimanite opaq'le mrnerals, apatrre, and zircon One sample also
coniains relatively abundanr opx (En36) and
Granitic dikes thal cut the contact granites
and the plulons are hypidiomorphic granular
to aplfrc ,lthough some dikes contarn calcic
amph bole, biolrle rs the most common mafc
mrncral wLth or withoul whlle mtca Allanile,
zircon, epidote, and opaque m nerals are typical accessory phases
and rare zircon, allanite, and pyrte
The texture
of rocks fiom the
SausJjellet
pluton ranges lroro suboph(rc to hypidiomorp
hrc granular. Plagroclase rs generally normally
7on6d lrom An.. lo An,^. lnlsrqranular lo rnler_
slrlial pyro'enes are partly replaced by
red_
drsh-brown broltle and olrve_green hornblende
OLartz and mlcrocline are intersliiial. Accesso
ry apalrre rs present n qranu ar' prrsmalrc, and
acrular habrls z rcon, a lanite, ilmonite ma9
nette, anhedralto poikililic sphene, and epido_
le aro lhe ot'ler a.cessory phases subsolidJs
aLteration of pyroxene has resulted in growth
ol
aclrrolitic a1o cJmmlrglo,rillc amphboe
quarlz, and rare greenrsh biolile
lhe A.rnel morzon le co'lla'ns abLnddnl
rabular phenocrysls ol perthllic alial reldspar
t O'*Ab,,Ar,, as fi'ucr' as In cn in d>mFie'
and plagioclase phenocrysts (:An:.) as nruch
as 1 cn lorq cel in a1 hvodomo ohic grdrular groundmass. The groundmass consisls ol
paqroclase, mc'ocl'ne porNlilic lo D'ismatiL
olive-green to blue-green l€rro edenile with
re'rcl pyroxene cores ano por\ lili' yelowbrown biolite. Ouarlz, apatile, sphene, z rcon'
lmenite, magnetile, chalcopyrte and epidote
ars accessory phases
'Ihc g.anrt,c ro.ls adiacenl lo lle velllo'd
pl.rlons a'e wroely vdl laore rr tetlurF dnd m ne
raloqv. Ihev a'e qeneral'y hvprdromorph c I ra _
,rula; and;anqF lrom porpnvnnc ralkalr feldspar - plagroclace pl^enocrysls) Io equigranu
lar. Plaqroclase { A135) Trcrocli'le qJa v
and brolile a'e commor lo all oi llese rocks
Geochemistry
Analytical Methods
Samples from the Bindal Balho ith and some
samples oJ the Velfjord plutons were anayzed
by X ray f uorescence (XBF) at IV d and Earlh
Science Associates, Nottingham. For the re'
malning samples, major and most trace'
elemenl analyses were done by XRF at NTH
or by induciively coupled atomic 6mission
spectrometry ai Texas Tech Universily The
rare earth elements (REE), Ta, Th, HJ and
u, were
analyzed
by instrumenlal
neutron
activation analysis at lmp€rial College, London
Resu/ts
Eepresentaiive resuts are presented n Tabl€
1. Samples ol granitic rocks irom the Bindal
batholilh are from localities wthin 5 km of the
Velfiord plutons.
The Hillsladfiellet pluton is alkali calcc, with
an alkali-lime index of about 53. The firsi sta
ge is disiincl from the second in its ower
SiO: and Na,O, its widely variabe TiO. and
Al,O., and its higher CaO contents (Fg 5)
The particulany wide range ol Al:O, , TiO: and
Sr contents (Table 1i Fig. 5) suggests that
compositions are controlled by variable accumu alion ol plag oclase and pyroxene. This is
slrpported by the slight posltve Eu anoma!ies
oi Alrich iirst stage samples (Fiq 7a)
I
4a
Calvin G. Batnes. Iare Prestvik, Oystern NardgLteh & Melanie
A Barnes
The second stage can be divided into three
groups on ihe basis of siol and K'o abundan
ces (Fig.5). Monzonilic samples frorn tho
western side of the pluton have the lowest
en these lwo groups have the highest K1O
values (at constanl SiO) in the ptulon. Sr
behaves as a compatible element in the se
rocks on the easiern slde have high S O) con-
cond stagej whereas Flb and Zr are ncornpa,
tible. The REE abundances ot second slage
SiO: conlentst whereas quartz monzoniUc
tenls. Monzonitic samples from the area betwe-
Cealogy of three diontc
ptLtons
49
.!
r
.
&^'. !.^
.rfar-Y
-
.i-^
r
br
..':i-fi'
-
'
{
:':^.^
{^
.
o
2
' i;. .'t
,o'r..1'f
|
,
I
r Lows,o
i
r
s'o ' second s'aqe
H'gb k,o ]
HEh
-i,
lE
.
13
| -9
:
^
akser - Drevli Pluton
Graniric rocks of the Bindal b.lholirh
=
dr"o
and
o
hopyroxene
B\"o
,
oo
o..b'
"l
loprl lrom a parenla magna
samples increase with increasing SiO, and the
(Ce/Yb)N ralio ls virtually constant (-14) Allhough negative Eu anonales are apparont,
they are slighl (Fiq.7a). The most evolved
samples from the second staqe ol ihis pluton
are composiuonally similar to the Aunet monzonte aLthough one sample of the Aunet
monzonite has a much arger negaiive Eu
anomaly (not shown rn Fig. 7).
The Aksel Drevi plulon is also alkali_calcic
(alkali ime index about 53). The analyses show
considerable scatter in Al,o,, cao, and Na,o,
as mighi be expected in such plagioclasephyric rocks. ln goneral, the pluton has ower
t\,49/(Mg+Fer) ratios and higher (but wdely
scattered) TiO) conlents than lhe H llsiadfjellet
and Sausfjellet p ulons (Fig. 5). REE abundan
ces and patlerns are similar to the Hilstad
fellet pluton but (Ce/Yb)N values are slightly
higher 09), with the exception of lwo dikes
One dike is a late'slage gabbro which has
tower lotal REE and lower lCe/Yb)N (=7.5)than
the rest of the pluton (Fig. 7b)i the pattern
also shows a downward concavity among the
ighl BEE. The other dike is a monzodiorite
wilh plagioclase phenocrysts and K feldspar
xenocrysts (?) that inlrudes a marble screen
near the northern contacl of the plulon. lt is
=
5Q
CalvrnG. Bames, fare Ptestvik Oystein Nordaulen & Metanie
A Ba.nes
dal Batholith serve to dislinguish them trom
the contact grantes (Tabte li Ftgs.5 and 6).
ln addrr on, rhe Bb Zr'ato ol the va rous types of g'dn tc ro.ks rn lhe dr€a cerve to drs
trngursl" lhem lrom ore another (Tig. 6'. The
conlacr qrantes have a ow, reaay constant
;;tr,'" ; i'"' ""'
Fiq
a
6
.;!r!
"
Rb/Zr (w€ghr rario)v6rsus Rb Therordencosodby
soid mo roprossnls over 90i, ol sampl€s lrom th6 V€-
ljord putonsitho i sld onc os€d by a dashed ne encosos
Bb rch sahples predomnanry lrom rho Nrrstadtjo 6r pru
rario. whereas th6 Bb Zr rar.os o'rhe grdnrc
dikes and the granites of the aindal Batho ilh
increase with increasing Rb conlent and are
dislinct fiom each other (Fig. 6).
REE abundances in the contact granites
display a wide range of concenvations (Fig.
7d), with the highest abundanc€s of the heavy
REE, the lowest (Ce/Yb)N ratios (=12), and the
only negative Eu anomalies in the garnel
bearing granites. A garnet-free, two micabearing granitic d k€ in the Sausfjettet ptuton
has the highest BEE slope ((Ce/Yb)N=40),
dle to the low concentrations
ot the heavy BEE.
which is largely
characterized by its high tola REE, pronoun
ced negative Eu anomaly, and lower (Ce/Yb)N
ratlo (=11i Fg 7b)
The Sausijellet pluion is distinct from the
other Velfjord plutons in its lower TiO, con_
tents (Fiq. 5) and higher alkali-lrne lndex (=56,
calc-alkaic). A.O,, Na,O, CaO, and TiO, show
agreaidea ol scaner. Sr behaves as an incompatible elernent jn the Sausfiellel p uton unlike
the second stage of lhe Hillsladfjellel pluton.
The REE abundances ol this pluton d splay a
re alively large range considerng th€ smal
range o1 SiO, values. The normalized patterns
of three sampes (73.65, S1.20, 91.224) have
relativeLy steep slopes ((Ce/Yb)N = 14'18). All
thr€e were collected near contacts and all are
quartz'bearng; sarnple 73.65 is a late-slago
quartz d oriie, The remaining samples aredioritic and have patterns with shallower slopeo
((CeiYb)N from 3 to 7). Among these samples,
the lncrease in (Ce/Yb)N is accompanied by
an incroaselnlotalREE abundances (Fig. 7c).
The granitic rocks oi the Bindal Batholith,
granites collocted near the marg ns ol the
Velfjord p utons {contact gran tes), and gran
tic dikes in the plulons are qenerally calc
alkalic and all but one are peraiuminous. Six
Discussion
Th€ close spalia relationship between the
Velfjord plutons and the contacl granites sug
gests thal the granites r€sutied from loca
anatexis caused by heat from the adlacent
dioriiic magmas. The volume ol the contact
granltes and th€ gradation from granile to
migmatite wilh disiance irom the dioritic ptu
tons suggests that the hosl petitic rocks wero
partially molten al the timo ot emplacement
01 the diorilic magmas. lf th s interpretation is
correct, the velfjord plutons must have been
ernplaced during orjust aflerthe peak oi regio
nai melamorph sm n the rsgion, which is con,
sistenl wiih Kollung s (1967)view thal the ptu,
tons were syntectontc. Accurnulation of grani-
tic m€lts near the dioriiic plltons may
have
been enhanced by disruption of the hosi m qmattes during intrusion and by contraction
ofthe dioritic magmas during cooling and crys,
lallization.
Petrographlc evidence suggests that deformation oi th€ dioritic rocks, granitic dikes, and
qreater than 1.1 (.e., strongly peralurninous)
as do four granitic dikes thai cut the plutons.
None of lhe granitic rocks of the Bindal Batho
contact grantes began when m€lt was pre
sent and continued, at leasl locally, through
cooling to greensch st facies conditions. The
contacl granites show ihe greatest degree of
strain because of this coniinu!m ol deJormaton from synmagmatic to submagmatc conditi
ilh are strongly peraluminous. The higher SiO,,
Rb, and Mg/(Mg+Fer) and generally lower Zr,
Sr, and TiO, oJ the granilic rocks ol the Bin-
ons and b€cause lhey have low solidus lempe
ratur€s and abundant, sasity-deformed q uartz.
Asymmetric zoning patterns simiar lo those
ol the
contact granites have Al/(Ca+Na+K)
5eolagy al
.) Ftr
riass qua z dior
<an €r
a
l9b3) BCE pcne n<
A Hi\lddrol6r
1
Fo 3. W6'qhi raro ol cao/A,o,
o aned aqa'nsr M!(Mg+Fori rh6
reld en.ro5ss dala lrom rhe E6.ond
sraoe oi tlre r1'Lsradlroll€r pluron
Ai ;rha svmbot as n F'a s rh€
anows nd :ale |re otr€cts or rract o
l.orr
1o ) ortropvro16na
'v'n€r nopyro^6n6 1.p!l
auql.
or o
maqnerio
dbt itic
Pl utons 51
e
i;;; .,-.r.i e ,1-e o'*td 6 o' q dn7 odo or q-a'u re
";.;,;;
Ji
. ;:'' r;;i;.
srmpos 0 "*o-"t""o'
Granr. ro.rs
z.b€a
'no
naioi
th rce
lmq and
Pa9o.laso
?
o.a
oluro_ The
'n€o
1'ld otulos'q lro pano'n(
t
.,-l._,
."'..........
.".
c
ril
. -:t'jt'
" .^"r.*
.'
-'.1
'
d?:.\ '
;/.!,
.-'h'(i't'^
^^
a
52
CatvhG. Batnes, TatePteslvik Oystein Nordgulen & Metante
obs€rved in the H llstadfjellet and Sausfjellet
pluions have been reported elsewhere (e.9.,
Bateman et al. 1363, Flood & Shaw 1979,
Barnes et al. 1986). Such asymn€|ry has been
ascribed either to tilt ng and erosion ol a v€rti
cally-zoned p uton (Flood & Shaw 1979, BaF
nes et a]. 1986) or to non coaxia! filling of an
expandinq pluton (Hutron 1988a). In lhe latter
case, the p utons have generally be€n shown
to have intruded in dilatant zones n a shoar
couple (Hutton, 1988a&b). Sirnilar models were
developed for the emplacem€ni ol gabbro and
granodloril€ in the sunnhordland Batholith ln
western Norway (Andersen et al. 1931). We
suggest thai the asymrnetric zoning palterns
olthe Hilstadiellet and Sausfjelet plutons may
have resulled from intrusion inlo a dilatant
zone of a sinistral shear couple. This idoa s
cons stent wiih the postion ol the velfjord
plulons in a weaklylineated NNw-ssE-trending zone (the dilatant zone) b€tween two
sirongly lineated NE-sw-trending zones. ln
such an inslance, elongate intrusions such as
the AksetDr€vli pluton and siage 1 of the
Hiilsradljellet pluion would have a NNW-ssE
orentalion, parallel to thal of the dilatant zone. This idea is cons stent wilh asymmetric
zoning n the Hillstadije let and Sausljellet plu
tons, with syniecion c emplacement of the
Velljord putons soon af(er peak metamorphism, D, deiormation, and thrusting wilh n the
HNC, and can explain the peridotite xeno iths
in the Akset Drev i p uton as having originated
in the middle ihrust sheet. lt also permts in
situ tormation of the contact grantes in a
ductile, high temperat!re envronment. The
high-temperalure, syn and post-emplacement
detormaiion of the plutons and coniaci grani
tes can thus be explained by delormalion
during the waning stages of O: tectonism.
The petrogenesis of the plutons and related
granilic rocks can only b€ d€termined with
detailed €lemental and isotopic mod€lling (in
progress). However, on the basis of currently
availabe data. we can make several d€ductions about th€ petrology of the velliord plutons. (1) The presence of olivine in the AksetDrevli pluton indicatos lhal al least some ol
th€ parental magmas had an ullramafic source
and originated in the lower crust or upper
mantle. Howover, the general lack of olivine
and the int€rmediale 1o low Mgi([49+Fer)valu€s n nearly all samples o1 the Akset-Drevli
pluton indicate that lhe par€nlal magmas had
und€rgone d llerentialion prior to emplace-
A
Barnes
menl- (2) The tact that lhe plulons are dislincl
and IiO,
ly difterent in terms of
^,49/([,49+Fer)
(in parlicular) suggests that
the parenlal magmas were composilionally dislinct. These dis
tinctons coLrld have arsen from different pri
mary magma compositions; but may also indi
cate difl€renc€s n evolulionary paths. For
example, th€ reatively F€-rich nalure of the
Akset-Drsvli pluton impli€s magmalic evolution
at low l(O:). ln contrast, the low TiO, in the
SausJjellet pluton could have resulted from
an in tially Tio,-poor parental magma or from
early removal of Fe-Ti oxid€s at relalively high
(O,), both of which are consistent with lhe
calc-alkalic nalure ofthe pluton. (3)Ihe conspi'
cuou6 scatter arnong the major-el€menl and
compatibe trace elemenl compositions ol ihe
Sausfjellet and Aks€tDrevli plulons and lhe
lirst stage of rhe HilLstadfj€llel plulon can be
€xplained in terrns ol accum!lation and/or
removal oJ varlable amounts
of
plagioclase,
pyroxene{especiallyclinopyroxene), and oxide
phases. ln Figs. 5c and 8, lhe effecls ol lrac
tionation ol these phases are schemalically
shown. The compositions of most samples
Jrom the Sausfjellet pluton can be explained
by clinopyrox€n€ + plagioclase accumulation
and the scatier shown by the AksetDrevi
pluton can be expained as the resull of cpx
a plagioclase I magnetile accumulation.
Schlieren banding, which s common in the
Sausflel€l plulon, is generally tholght to lorm
as ihe resulr of crystal segregaton dlring
magmatic flow. This mechanism can probaby
expla n much of the wide compositional scat
1€r among rocks in the pluton. (4) The alkalrich compositions oJ the two northern p utons
and the differences in composilion and inlens -
ve varables among and within plutons may
have been caused by assimialion oi crustal
rocks or mixinq with crustalmets. For exampl€, the lhree distinct composiiional groups of
the second stage o1 lhe Hillstadfjellet puron
probably do nol repr€senl the producls of
simple fractional cryslal izalion oraccumu ation
from a single parent. The pot oJ K)O against
SiO, (Fig. 5A) is suggestive that the S O, rich
group could be the result ot mixing ot mon
zonilic and grantc melts such as the conlact
granit6s.
The compositional distinctions between the
contact graniles, graniies typical ol lhe B ndal
Balho ilh, and gran tc dikes in rhe dioritic plu
tons lmpies distinct orqns for the three
groups. lt also indicates that the dikes n ihe
dbt itic
Geolaqy al t ht ee
plutons are probabiy not olishools 01 nearby
Eindal qranites, as suggested by Kollung
(1967), or of the conlacl granites. Theretore,
the fact thal granitic dikes cut ihe veltiord
putons should not be taken as evidence lor
the relative timing belween Bindalgraniles and
The contact graniles display mineraLassenr
blages and chemical composilions typical of
derivation by parliaL melting ot p€liUc source
rocks {whlte & Chappell, 1977), which is con_
sislenl with the idea that th€ contact granites
resulted iiom nearly compele n situ anatexis
of hosl rocks thal were party molten at the
t me of inlrus on. The pos tve correLation bet-
ween Bb/Zr and Rb !n the qran tic dikes (Fig.
6) is primarily a funclion of decreasing Zr
conlent with increasing Bb. ll these d k€s are
dillerentiales ol the dior tic magmas,lhis relali
onship may indicale that zirccn was
a
late
fractionating phase; however, t is aLso compatible with an origin by parlial melting wth zlrcon resdual n the source.
A similar
relationship belween Bb/Zr and
Rb among the granilic rocks of the Blndal
Batholith suggests similar conclusions may
be reached. In general however, lhe chemica
and isotopic cornpostions oi graniles ot the
pl uton
s
53
oi the compositional variations observed. The
deformalion of the plutons and lhe contact
oraniles and th€ zoninq patterns of the norl
;ern and southern p utons suggest that defor'
maiion accompanied inlrusion in a dilatanl
zone of a regional sinistral shear couplo This
interpretation has srgnrfcanl mplicalons not
only for lhe orgn and evolLrlron ol the Vel
fprd plutons but tor lhe enlrre B ndal Balho
hrh and d€serves detarled structural, aeochro_
nologrcal, and isotoprc invesligation Finaly
lhe composrlronal comple'rlres among lhe
Velfiord plutons as well as the variety of grani
tic rocks in lhe area emphasize the need lo
consider mutistage evolulionary paths n the
development of the Bindal Balholith.
Acknowledoemenls
Th's rasoarcrr-was como€led wh o c aarnos was ar the
NorwoaEn Lnsrtute oJ Tedhnooay n Irondh€m und€r $e
sds oi rh€ Fubi qhLHaYs Proqram
F,;anda d s.hoa'r
w;s suoooded bY N6nsenrondor rsld and anavt'a
wo'k ,n r99d and 1991 wsr6 tupponsd bv NAVF qranG
and 4!r 91rO1r ro Pro5rvr O
1e73
dao I'nancia suppon irom
No'wav and kom NTNF grani
Mr oororror43 Frnariv w6 wsh ro rhrnr I vor6s and I
Romm€ ror lh€ ass srinco wrh xRF analvsos
fha deobo'cal surv€v
oi
Bindal BathoLilh are not suggeslive ol derivati
on from pelilic souTce rocks typical ol
the
Uppermost A lochlhon (Table 1; O. Nordgulen,
unpubllshed data), bul indcate an origin by
processos lhat operated deeper in the crust.
However, our sampjing oJ these rocks in the
Velfjord area is too sparso to justity lurther
Relerences
And€rs€nIB N'esei.P FykkeldE. & SonaH.
1991
Melenhancod do{ormalion durinq emplacom€nr or
qabbro and qraiod orlo n rhe sunnlrord and Balholrh.
;esr Norway coo/ Mag 1n 2a1226
JM &Gnbbr€.FF 1936 Trl6d
Conclusions
Ihe Veijord putons
10ns
represent intrusion oi
mafic and intermediate magmas inlo the HNC
during the metamorphic peak or soon thereaf
l€r. At leasi two of the pLutons had more than
one parentalmagma and each parenta magma
lollowed dilierenl evolltionary palhs Much
ot the compositional variation in the Aksel-
Drevli and Sausljellet plutons can be ascr bed
to variable accumulation ol cpx, pagiociase,
and oxido minerals. Each pluton caused insitu anatexls of peltic migmalites n the hosl
rocks, which resulled in lenses of peralumi
nous granite adjacent to the dioritic bodies.
[/ixing oi these contact granitic nrelts wilh
magma of the plutons may have caused some
'd
plu
tlre Kramarh Mounians ol carrorna and or€
F6s. 9t, 60s9
6071
Baidan. PC. Cark LD Fubor. Nl( Moore JG
Rin.h3 cD 1963, Th6 Serc Navada Barho itlr
s rhe contra
6eal sutv Prcl Papet 41l D,46
PP
K
1933: M€ramorphism
/'
Ahrsns
or
pa
&
A
l-r's
uiramanc
,ocks n tlro c€ntra scandnavan caedondes Ndl
9ea1 Dndets sqeLtat Prbt 3,4695
s E 1979 I rch lumulale dorre ai
lhe base ol a ttred Aranodiorro pubu nom ro New
A6tata J Geat 37 417 425
MA FreY. FA & wideman TR
1963 Ferarv€ and absoldio torrestia abundances ot
rrre rare eaitrrs
lH,sd
origin and dtstribu
tan at the elenents, P€rgamon Oxrord.
Enqrand
H W 1943a: rqneous €mp acemsnl ln a shear
zone term naton: The b orit6 gran16 at stronian, scot
rand Geor soc ,4'6. 6!/1 100 13921399
Hunon. D
54
Calvin G. Barnes,
Io,e Prestvik, Oystern Nardguten
Nullon DH.w 1933b Grani€ empac€monl mochansms
ai! i€clonc conlrols, n16rences l.on d€lormaion slu.
des hahs
l(o ung.
S
Rayat
soc
Edinburyh: Eadh Sciances 79,
1967: Gsoogiske u^dersokes€r
N
Heqeand o9 nordrge Namda
My and
F
Prestoik
T
idot
sor 9€
geat unders 254,
1972 Vortjord. B€skrv€so lir d6r b8rsqrunns
georoolske gradloigskad r3 1:100 000. Nor gdor
'
1974, No&egan chromian ugrandre larnots
H.Robins.B &Srud.aA 1935
wrhn rh6 scandinavran ca€donrdes
srephens MB.Furnes
rqneous acrvry
& lvlelanie
A Bahes
/n:Gee DG & Srud BA l6dsl The Cat6dohid6 oto
oen . scandinaviz and rctat4d a/66s John wi€y add
sons Ltd chch€stor 623-656.
Thorsn€s. T. & Losolh. H. 1991 Toclonoslraliqraphy n tho
V€llord'Tos€n rogion sourhwosr€rn parl ol rh€ H6ra€
rand Nappo Complox C€nirar NoMoOran Caodonidss.
Not geot unde6 Butl 121,114.
BO & Mckelson M 1936: A Rb/$ study
rrom rrie Mosj66n un I, H€ q6 and Nappe cohper and
To,udbakkei.
is b6ar nq on rh€ timmg ol bclono-m€tamorph c €v6nrs
Mthin rh€ Lippomosl Aiochthon. c€nirar scand navEn
Cal€donid€s, NoNay Nor G6ol fidsskt 66 263-270.
White. AJ R. A Chappol. B.W 1977: U tramolamorphism
and qranitod aenesis factonophysics 43,7 22
Manuscript received l\4arch 1992: revised typescipt June 1992; accepted June 1992.