PETROGRAPHICAL ANp CHEMICAL INVESTIGATIONS OF A PRECAMBRIAN GABBRO ...

26 Pages·2011·2.11 MB·English

PETROGRAPHAINCpAC LH EMICAL
INVESTIGATOIFAO NPSR ECAMBRIAN GABBRO
INTRUSIHOINÅ,S EBNA,M BLAER EA,
SOUTNHO RWAY
SVEIFNR ODESEN
InstiftourtG te ologUin,i versiitO estleot
FRODESESNv,e inP.e:t rographiacnadl c hemicianlv estigaotfia o ns
Precambriagna bbrion trusiHioåns,e Bna,m blea reaS,o uthN orway.
NorsGke ologTiisdks skrVifto,l 4.8 ,p p.2 81-30O6s.l o1 968.
A smalgla bbrion trushiaosnb eens tudipeedt rographiacnadlc lhye m­
icalTlhye.g abbrhoa sb eena lterbeyda chloripnnee umatol(ysscias­
politizaatnidob nyr) e gionmaelt amorphiTshme.c hemictarla nsforma­
tiondsu et ot hesper oceshseasv eb eenm appeda,n dt hep rimar(ym ag­
maticc)h emicvaalr iatiooftn hsei ntrusfioounn d.
Abstra.c t. 281
Forewor.d 281
Introduction 282
Fielodb servatainodnp se trography 284
Thec ountrroyc k.s . 284
Theg abbro. . 284
Theu nalterroecdk. 285
Secondarayl terations 286
Coronfao rmations 287
Cloudionfgp lagioc.la se 288
Scapolitization 288
Furthreerg ionmaelt amorphi.s m 290
Modala nalyses 290
Pegmatiatnedsv eins. . 292
Discussoifoc nh emicdaalt a. 293
Analytimceatlh od.s . . 293
Chemicvaalr iations 293
Chemictarla nsformaotfit ohness c apolitization 295
Chemictarla nsformaotfit ohners e gionmaelta morphism 301
Primarcyh emicvaalr iati.o ns 302
Magmatidci fferentiation 303
Summary. 304
References 305
FOREWORD
Thipsa peirsb asictahltelh ye ssiusb mteidtf omry c andr.e aelx.a mination
Decemb1e9r6 U6n,i verosfOi stlyHo o. wevepra,ro tfst hteh eshiasvb ee en
rewriatntdce onn denssoemdhe,a veev ebne ecno mpleotmeiltyt ed.
Thew orkw asc ompleutneddet rh es uperviosfPi roonf esTs.Fo .rW .
Bartahn dP rofeHss.No eru måntnow, homI a mi ndebIt aelds.wo i stho
5
282 SVEINF RODESEN
thanDkr O.. H .J .C hrisftoivrea luadbilsec usasnidao dnvsi acnedt, h ree st
oft hes tasfcfi,e natnidft iecc hniocfMa iln,e ralogisk-MGuesoeluomg,i sk
UniverosfiO tsyl of,o arl tlh ehierl p.
INTRODUCTION
Gabbrion trusfioornams c haractgerroiusoptfr i occ kisnt heKo ngsberg­
Bamblaer eaan,dt hehya vbee etnh orousgthuldybi yem da nyw orkeSrcsa.n ­
dinaviaaunt hhoarvsce a lltehde rsocek 'sh yperites'.
AccordtionJ g.A .W .B ugg(e1 94t3h)'e,h yperiatreeis n't ruidnet dh e
latsetra ogfet hoer ogepenrei odt,o s omeex tednutr inag t imoef t ension.
Thew holceo mplheaxbs e edne foramfetdte hrie n truasnidot nh,e 'hyperites'
havbee emno roer l esasltebryem de tamorpThhiesf mi.ra sltt ertaotoc icounr
ist hefo rmatoifco onr onaarso und certain mineralsa;r e further alterations
recrystallainzdaa mtpihoinb olitlitiz spa otsisointb.ofl oel lsotweb py s tep
thet ransforfmraottmih oecn o rosntaa tgher ouhgohrn ble'nhdyep ertiot e'
moroer l esssc hisatmopuhsi boBleictaeuo.sf te h lea tdeerf ormatcioonn­s,
formittoty h ceo untrroyci ksg enerfaolulnybd u,tt ransgrsetsrsuicvteu res
arneo utn common.
Them aipnu rpoosfte h iwso rhka sb eetno s tudtyhc eh emivcaarli ations
withoinneo ft hegsaeb binrtor usiTohness e.l ecitnetdr uissil oocna tiend
S0ndelienad n,a reeaar limearp perlb yB uggaen,d i tca n bes eeinn t he
fanro retnhd o fh imsa po ft hSeö ndeDliesdt (r1ic9t4p 3.1, 3 ).
Thei ntrufsoiromans d omes hapheidcl all lHeidå se1nti. sh ardll kym
acrossosn ,o m apso fa suitasbclaewl eer aev ailaabnldte h,em appiinsg
basedo no nea eripahlo togrWaipdhe,r9 ö65e D 25, origalilniny thes cale
-
-
/ f1� -
l
10t- -+- t-
-
-� · \F- -.
�
t-- IB�
:; -t- t- v
l (j '
r-- l
C4 556-1H 4·bH4·a
oE4-l v
" /
\ / Figl..T heo utlionfet heH iåsegna bbro
G�-/1 bodyw itthh eg riadn dt he3 5s ampltehsa t
1'--------- arem entionientd h et exTth.e s ampltehsa t
aret akeonf ft heg riadr en arnedi nt he
o G Figure.
PRECAMBRGIAABNB RINOT RUS,IH OINÅSBEANM,B LAERE A 281
ITJ
Gabbro
!\-��Me�ta�ga bbro
� Amphibolitgince iss
�(with anthophyllite)
[:::.-·Qu.ar:tz.tie]
Q
100m Covered
Fig2.. G eologimcaapJo fH iåseann di tssu rroundi(nPgesg.m atiatreees x cludaendd s hown
separatienFl iyg 7.. )
284 SVEINF RODESEN
1:15 1:7
000,e nlargteoda pproximate5l0y0 .O n thipsh otograwpahs l aid
35
a quadratgircig di vings amplewsi thitnh eg abbrbood y (approximately
80m betweetnh es ampleTsh)e.o utlionfet heb ody andt heg riwdi tht he
sampleasr es howni nF igl. .B ecausoeft hes malslc aloef t hem aps,th e
pegmatiatreens ots howno n theg eologimcaapl,F ig2., b uto n a separate
7.
map,F ig.
FIELDO BSERVA TIONSA ND PETROGRAPHY
Thec ountrrocyk s
Theg abbrios i ntrudienda mphibolaintded sa rkgn eisseasn,d e xcepfto r
a faulitnt hew esti,ti sc ompleteenlvye lopebdy t hesWee.s to ft hef ault
theriesa nothgearb brsot,r ongalmyp hibolitbiuztae sdt ,h iiss n otb elieved
toh avea nyd irercetl atitootn h eH iåsegna bbroi,th asn otb eenf urther
studied.
To then ortthh ei mmediactoeu ntrrocyk sa ref ine-graaimnpehdi bolites,
tot hee asantd soutthh eayr es omewhacto arsaemrp,h ibolgnietiiscs ewsi th
narrobwa ndosf I ightocecars,i onallayl mosqtu artzignteiics,s .
Thef emimci neriaslu sualcloym monh omblenadned o/r b iotibtute m ,a y
bed iopsiodrte r emoldietpee ndionngt hec hemiccaolm positPiloang.i oclase
isu sualtlhye o nlysa licm ineraqlu;a rtizs n otc ommon.I n placetsh,e
countrryo ckasr es capolitAisz eadc.c essomriyn eraalrse f ounda patite.
sphenreu,t itloeu,r maliannedi, r oonr es.
In onec aseo rthopyroxiesf noeu ndi,n dicatgirnagn ulfiatcei eofs t he
areaH.o wevears,t hissa mpliest akevne rcyl osteot heb ordeorft heg abbro,
iti sp robabrlayt hreerp resenctoinntgam cett amorphiIsfam n.e xtrapolation
(1943.
ism adeo n Buggem'sa p ofm etamorpfhiacc ioefst heB amblaer ea
p.1 34)H,i åsefna lwlesi iln sitdheea reoaf a mphibolfiatcei es.
Anthophyllite-rboecakrasri enc go mmoni nt heB amblear eaTh.e y are
formebdy a Mg-metasomatwihsemr,et heM g iss upposteodc omef rom
1943).
theb asirco ck(sB ugge
As can bes eenf romt hem ap,t hen arrolwa yeorfsa nthophylrloictkes
area lwayast a distancfer omt heb ordeorf the gabbroT.h erefoirtei. s
diffictuoal ctc eptth ei deao fa dirercetl atbieotnw eetnh et wo rockass,,
fori nstance, loefam cahginnegs iufmr omt heg abbrtoo t hec ountrroyc k,
ande asiteori magian em oreg eneraMlg -metasomatiints hme a rea.
In somep lacetsh er ock consisatlsm osetx clusiovfea l yl ustropuasl,e
greyibsrho wna nthophylwlhiitleis,nto theprl aceist c ontaibnlsu ceo rdierite
andfogrr eetnr emoliintc eo nsideraamboluen ts.
Theg abbro
Int hef ielidtc anb e seent hatth eg abbrios h ighlayl terbeyd s econdary
processes.
Durintgh el aterre gionmaelt amorphitshmeg abbrhoa sr ecrystaltloi zed
PRECAMBRGIAABNB RION TRUSHJJOÅNS,BE ANM,B LAER EA 285
a !aregxet eIntti .sf oliaatltelhd r ouagnhd, tthyepi ocpahli tteixct iusr e
onllyoc alplrye serTvheefd o.l iaitsai lomno vsetr tiacnadl ,o nlsyt riiktes,
varyifnrgoN m8 � toN 130igsr ecorodnet dh mea pI.t f olltohwgese neral
treonfdt haer eaan di sd iscoridnEa anntdW .
Anothaelrt eratthiacotan ne asibleys eeinn t hef ieilsdt hes capoliti­
zatiwohni cihsa vercyo mmofne atiunrt eh idsi st(rWi.Cc .tB rögg1e9r3 4,
Bugg1e9 43T)h.eu naltegraebdb ruossu ahlalvyae c haractberroiwsntiisch
burguncdoyl oduure t ot hed arpkl agiocTlhaess eec.o ndsacrayp oilsi te
usuamlillykw yh iatned g ivtehsre o cakp atclhoyo Tkh.i csa no ftbee ns een
alonfgi ssuirnue nsa ltegraedb brIno t.h ef ietlhdeH iåsgean bbsreoe ms
strongslcya po1aitsti hzbeer do wncioslho iusar n e xception.
Itp rovetdob ev erdyi ffitcoum latp t hesael teraitnit ohnefs i eld.
Firsittil syi mposstiodb eltee rmfinreo hma nsdp ecimwehnest hae sro me­
whaatm phibolrioctkih zaesmd u chl,i ttolrae n,y a ta llp,y roxelneef t.
Secondallyt,ep rleadg ioccalnaa lssebeo whiteev ewnh etnh eirsel itotrl e
no scapolpirtees eMnatp.p ionfgt heaslet eraitsti hoenrse bfaosreeod n
petrogrsatpuhdiipce. 2s 9,2 I.tw ash,o wevoebrv,i ofurso tmh ev erfyi rst
fieolbds ervatthiatothn Hesi åsgeanb bmraos shiafd n o' frecsohr'pe r e­
servferdo aml terations.
Ins piotfet hes troanlgt eratthieoarnresef eatuirnae lsm oesvte rtyh in
sectsihoonw itnhgme a gmatoirci goiftn h reo cfko,ir n stalnacregh ei,g hly
alteprleadg iolcaltaohsfset heo rigionpahli tteixct uBrueto. n lay f ewo f
thes amplceasnb es aid t obe altelrietdpt .l2 e9I,.
Theu nalterreodc k
SamplFe2i sb yf atrh eo ne! eaasltt ebryer de giomneatla morphsios m,
itt elmlusc ha boutth eo rigirnocakl,a ndw ilble r efertroef dr equye.n tl
Itpsl agioacnlcda lsien opyraoroxene lnsyel igahlttleytr heoedr ;i ginal olivine,
howeviesrc ,o mplerteepllya bcyeo dr thopyrsoeex beenleo,Cw o livhians e
beenf ounndo wheirnte h Hei åsgeanb bro).
Ther ochka sa subophtietxitcuI rnhe a.n sdpe cimietnw oulbde c harac­
teriazsem de dium-grbauitin net dh,i sne ctiiotcn a nbe seetnh atth e
intersptyirtoixaealnr esese vecrmaa lc ross.
Notbicnagn b es aiadb outth ec hemiccoam1p osiotfit ohneo riginal
olivbiunatec ,c ordtioBn rgö gg(e1r9 3t4h)oe l iviincn oe rrespo'nhdyipnegr ­
iteuss'u ahlalsty h ceo mposiFto6i0o•n
Thep lagioicslh aisgehz loyn eodf,t sehno wisnegv eorsacli llaTthieo ns.
zonimnagy h,o wevteors ,o me exbtede unett oN a-metasomdautriisnmg
ther egiomneatla morphpi.3s 0m1,M. o stz oneadr et hef eJdsopfaG r6s
(An62-A6n)3a ndD 4( An57-3A2n).
Thec linopyriosxa enn aeu giAt =e ,0 .0225V,z:: ::5::0:° Z, AC = 43°
Its howvse rnya rreoxws olultaimoenlw liatleho wb irefri.n gence
..
Thei roonr mea yb em agnetoirit lem enite.
Primaorryt hopyriosax besneen t.
286 SVEFIRNO DESEN
Theo rthopyroofxt ehneoe l ivpisneeu domoirspb hosu nwdi thtihne
bordeorfts h oer iginoalli vgirnaein asn,dt haem phibaonldge a rneotft he
earonraesp lpalcaeg ioscelbeae sleo,Tw h.ea utgeii so nlsyl iguhrtallyi tized,
scapoilsfi otrem ferdo pml agioclltah saest.h erebfeoerpneo ssitbool beta in
ana ccurmaotdea aln alyosfti hseu nalterroecfdko rt woo ft hes amples
counttihnefg o llowwaiyn:g
OlivineO:r thopyrionxt ehnoeel ivpisenued omorphs.
AugitAeu:g i+t eu ralite.
PlagiocPllaasgei:o +c laamspeh ibaonldge a rneotft heea ron+a ssc apolite.
Ther esualrtess h owinn T ablle.
Tablle. M odala nalysoefts h eu nalterroecdk
SamplNeo . F2 s 56-1
Olivine 8 16
Augite 24 14
Plagioclase 67 67
Accessories 2 3
Sum 101 100
Thes amplHe3sa ndE 7a rteo ao ltefroeardc curmaotdeaa ln alytsobe es
doneH.o weveHr3, h ash adm anyb,u tv ersym aloll ivgirnåei wnhsi,li et
looakssi fE 7h adn oo livaitna elA l .c onsidevraarbilaeit nit ohnoe l ivine
contoefnt th ien trusseieorutnsh eresfuobrset antiated.
Theraer set roinngd icaotfip olnasg iobceliantsghef e i rmsitn ertaocl r y­
stalflrioztmeh mea gmaF.r equeonltilvyhi anspe a rtsluyr rounpdleadg io­
claIsaet hasn,dt hoel ivpisneeu domoarrpgehe sn erfaolulnytd a getwhietrh
thel ataeurg ibteet wetehnel at(hsse Fei g4.) A.p atiitsfe o unadss mall,
anhedrgarla iinnse ,a ralysw eials l atpel agioacnldaa sueg iatned,h as
probacbrlyys taulnltilizaleti den t hec rystallhiizsattoTirhoyecn. o urosfe
crystalliisdz iastpiloiannyF eidg3 ..
Thiissd iffefrreontmth eg enecroaulr osfec rystallsiuzgagteisbotyne d
Brögg(e1r9 3p4.2, 0 w)h eroel iviistn hefe i rmsitn etroacl r ystallize.
Reynold&s F rederi(c1k9s6op2nr) o vae d ifferenotfit ahtepi aornen t
gabb'rboay s eparaotfoi loinv firnoeam m ixtuorfde i aHaagnedl abradorite'.
Froml aboraetxpeorriym enittss e eruassi fp lagioccolualbsdeet hfei rst
minertaocl r ystaflrloiamz bea salmteilbcty l oww ateprr essuarleosn e
(Yo de&r T ill1e9y6,2( )T.h wiisl olfc ouraslesbe o d ependoentn htce h emi­
caclo mposiotfti homene lt.)
Plagioclase
Olivine
•
Augite
Fig3.. C oursoef c rystallization Iroonr e
oft heH iåsegna bbrmoa gma. Apatite
PRECAMBRGIAABNB RION TRUSIHOINÅ,S EBNA,M BLAER EA 287
Secondaalrtye rations
As theg abbrion trudiendt hel atesrt agoef t heo rogenpeer iodi,t w as
subjetcot a retrogrmaedtea morphissomo na ftetrh ec onsolidaAtsi on.
pointoeudt b y Reynol&ds F rederick(s1o9n6 t2h)ew ater conotfte hnet
rock plaanyi sm portarnotl ien t hem etamorphailct eratwiiotnshi; n suffi­
cienwta teprr esetnhte r eacticoannsn optr oceedI,e avitnhge r ockw itha
granulfiatcei meisn eraasls emblawghei,l meo rew aterm ay givea rock
ofl owefra cieAss. w atehra sa cceaslso nmgi nutfer actuirnet sh eg abbro,
transitions rbocektswo efd einf ferfeancti ceosm monloyc cuirn a matter
ofc entimetTrheesv .a ryidnegg reoef a lteratoifot nh eH iåsegna bbrios
showb elowp,.2 92.
Coronfao rmatTihoenf si.rms itn erraela ctitoont sa kpel acien t heg abbro
yielcdo ronaasr ouncde rtain mianseo rlailvsi anned i rono resC.o ronas
haveb eens tudibeydm anyw orkewrhso h aver eportae gdr eavta rieatnyd
suggesdtiefdf ereexnptl anattioot nhse ifro rmatiBoenc.a usoef theg reat
varieittiy s u nliketlhayct o ronaasss ucha ref ormebdy o nep roceosnsl y;
undoubtetdhleyym ay beo fd tmteroirc ( regionaanld c ontactm)e tamor­
phico rigin. Magrmeaatcitci roinm ss houlndo tb e resignatceodr onas.
(Sederho1l9m1 6V,og t1 921B,r ögge1r9 34S,h and1 945G,j elsv1i9k5 2,
Murth1y 958Re,y nol&d sF rederic1ks9o6n2F r,od ese1n9 6a8. )
Fig4.. O livipnsee udomorpAh c.o reo fo rtho­
pyroxewniet hi roonr ei ss urroundbeyda rimo f
orthopyroxeanned a doublaem phibole corona
(thoeu tepra rcto ntainvienrgm icuslpairn eNlo)t.e
thea ugitTeh.e c oronaasr ef ormeodn lyw here
oliviwnaes a djacetnotp lagioclTahseep .y roxene
rima ndt hei nnearm phiborliemf ollotwh eo utline
oft heo rigionlailv ignrea inD.r awinagn dr epro­
ductiaonf p hotomicrogfrraopmhF 2. x14
288 SVEINF RODESEN
As mentionaebdo vteh eries n o olivilneef itn t heH iåsegna bbroT.h e
generfaela turoefts h eo livipnsee udomoraprhesa sf ollowasr:o unad c ore
ofg ranuloarrt hophyrowxietnlhea rgaem ountosfi roonr e( magnetiista e r)i m
ofo rthopyrox(weinteh oourte a)n da doublrei mo farn phibolet,h eo uter
containing vermicuIltia srb elsipeivnteehdla .tt h er imso fp ureo rthopy­
roxenaen dp urea mphibowleer ef ormesdi multaneoduusrliyna gn auto­
metamorphiasnmd,t hatth ec oreosf o rthopyropxleunoser ea ndt hes ym­
plectairtees imil'acro ronfaosr'm eda tt hef irsstt agoef ther egional
metarnorphi(sFmr odese1n9 68a).
Gametd eveloipnst hec oronaatsa latesrt agoef t her egionmaelt amor­
phismu,s ualalsys malglr ainfso rminag m ored iscontinruiomub se tween
amphiboalned p lagioclase, replacing both.
Them ineralosf t hec oronaasr ed iffictuoli td entitfhyem, i neraglra ins
ares malaln di na preferred oriaenndtn aetiitohne,r orthopnyorro xene
amphiboslheo wn ormacll eavaTghee.p yroxeonfet hec oreiss a bronzite,
En82( lar2gVe, o pticanlelgya ti6.v e=, 0.010T)h.e p yroxeonfet hec oro­
nash asa pproximattehlesy a meb irefringaenndci es,p robabl(yn early)
thes ameB.r öggecra lltsh ea mphiboalcet inolite.
Cloudionfpg l agiocTlhaesp el.a giocolfac soer oniitsef sr equenhtilgyh ly
cloudeSdt.r oncgl oudionfgp lagiocilsab seel ievteodbe eausebdy finely
distribiurtoendo xidien troduceda ftetrh ec rystalliz(aPtoilodne rv&a art
Gilke1y9 54a)n,d s eemtso d ependo nt hec ompositoifot nh ep lagiclaansde
coolihnigs toorfyt he gab(bCraor st1e9n5s7 )T.h ec loudimnagy alsboe
duet os pinegla,m etb,i otirtuet,i loerh, o mblende.
InH iåsetnh ec loudiinsgd uet os pineTlh.e cloudepdl agiocllaatshes
alwayhsa vea narrorwe crystalbloirzdeezdro new iths malbll ebosf a m­
phibol(e? )W.h en thec loudepdl agiocliasss ec apolittihzeec dl,o udiinsg
transforimnetdvo e rmicuolreb sl ebosf g reesnp inienlt hes capolite.
Thec loudionfgp lagiocilsaa s es ignof s ligmhett amorphailct eration.
inc aseisti sp riotrot hec oronfao rmati(oMnu rth1y9 58T)w.o thisne ctions
fromF 2s howd ifferednetg reeosf a lteratoino hna;st hed oublaem phibole
coronadses criabbeodv ea,n dt hec loudiinsvg e ryf ainwth,i lien t heo ther
thec oronaarse a lmosotb literia.te e.td h,i issm orea lteraendd t hec oluding
isi ntensSea.m plSe5 6-1w,h ichb,e causoef t heg ameti nt hec oronaiss,
believetdo b e stial ll ittmloer ea lterheads,o nlys lighctlloyu depdl agio­
clasTeh.i sm ayo fc oursbee duet op rimaryd ifferebnectewse etnh et wo
rocks,b uti ti sc ertatihna tth ec loudirnagp iddliys appedaurrsi nfgu rther
metamorphilstmd .o esh ardlpeyr sisbte yontdh ec oronsat age.
ScapolitiTzhaetH iiåosne.gn a bbrios e xtensively scampoosltoi ftt ihzee d;
samplecso ntamionr eo r lesssc apoliTthee. s capolitihzaasti inop nl aces
PRECAMBRIGAANB BRION TRUSIHOINÅ,S EBNA,M BLAER EA 289
Fig5..T hes capolitiozfat thiepo lna giocilsaa csceo mpanbiyer de placemoefhn eta vicllyo uded
augibtyegr anulaorr thopyroixdeennet itcota hle o nei nt heo livipnsee udomorpDhrsa.w ing
andr eproducotfip ahno tomicrogfrraopmFh 2 . x9
beenv eryin tenasses ,o meo ft hes ampleisnf achta ven o plagioclleafste.
Thes capolitiizsaa t hiiognht emperatpurroec esisnF, 2 itc anbe seen
thaitti sa ccompanbiyea dn a lteraotfia oung iitnet oor thopyroFxiegn5.e, ,
whichc annobte seen tob e anyd ifferfernotmt heo rthopyroixnet nhee
olivipnsee udomorpBhust.,a s alreamdeyn tionetdh,es capolitiziast ion
latetrh ant hec loudionfgt hep lagioclaansdec ana tm ostbe simultaneous
witthh el atesrt agoef t hec oronfao rmation.
When scapoliitsef ormebdy a moderatceh loripnnee umatolyistii ss ,
usualsllyi ghmtolrye c alctihca nt hep lagioclfarsoem w hicih ti sf ormed
(Shaw1 960M,a rakush1e9v6 4)H.o weveri,n s tudyisncga politiizna tion
theU ralsM,a rakush(e1v9 64f)o undth aitn h ighlsyc apolitrioczkestd h e
compositoifot nh es capolwiatse M e20i ndependoefn tth ec omposition
oft heo rigirnoaclk .
Ina ccordawnicteth h itsh,e c ompositoifot nh es capolviatrei ceosn sider­
ablyt hroughtohuetH iåsegna bbrWoh.e n presenitn s malalm ounttsh,e
scapoliista e m izzoni(t.6.e = 0.02I3t)i .st henl yinagl ontgh eb orders
290 SVEJNF RODESEN
oft hep lagiocllaatsheBs u.tw hent her ociks m ores capolittihzese cda,p olite
isa dipyr(e6. = 0.014T)h.e p lagiocliasst eh esnt rongrleyc rystalolri zed
hasc ompletedliys appeaarneddt ,h ea ugitiesu sualcloyp letreelpyl aced
by homblendTeh.e res eemst ob e transitbieotnwse etnh et wot ypeosf
scapolite.
Fiveo ft hes amplefsr omH iåsehna ven o plagioclleafsTteh. e ser ocks
arev erys imilwairt,ah charactegrriasntoicb latsetxitcu croen,s istailnmgo st
entireolfys capolaintdeh omblendwei,t hoc casioniarlo no ne,s phene,
rutiolerb, i otiTthee.y s eemt ob e thee ndp roducotft hes capolitization
proceswsh erteh ec onditiwoenrses ucht haat s capolaiptper oximaMtee3l5y
wasf ormed.
Furthreerg iomneatla morphBiys fmu.rt hmeert amorphitshmec orona
structurraepsi ddliys appeaarn,d t heo livipnsee udomorpahrser eplaced
by aggregaotfe gsr anulgarree nish-browcnoimsmho nh omblendTeh.i s
horobieinsdi ed entitcota hle o ner eplacaiunggi tseo,e vertyr acoef o livine
soonv anishes.
Thea ugimtaey s tiblell ittallet ersetdi,hl ela vicllyo udeadn,dw itho nly
a narrorwi mo fh orobieanldoen tgh eb ordetrop lagioclIanss oem.e c ases
them ineraalrsec rushehdu,tg eneratlhlepy y roxenies j usmto rea ndm ore
replacedb y homblende.
Thep lagioclwaisleal l sroe crystadlulriizntegh er egionmaelt amorphism.
hutu sualtlhye raer es omeo rigipnlaalg iocllaastehl se fatf tearl tlh ea ugite
isg oneA. d istianlckta mleit asornatiisis nmd icabtyes dt rosnegr icitaantdi on
albitizoaftt ihoepn l agioclase.
A fews ampleasr ec ompletreelcyr ystalsloit zheedra er en o traceosf
them agmatoirci goifnt her ock.
Modala nalyses
Fromm odal analys(eTsa bl2e) ,f igurceasn b e givetno designatthee
varyidnegg reoef a lteraotfito hne g abbro.
Thed egreoef sc apolitizcaatnib oeni llustrbaytd eidr ecptlloyt toinn ag
map thea mounotf s capoliintt eh em odel.t i sh,o wevemro,r ec omplicated
toi llusttrhaetr ee gionmaelta morphisHmo.r obienidsef ormeidn l arge
amountbsy t hipsr oceasnsd m ighhta veb eenu sehdu tf ort hef actth ahto rn­
blendiesf ormebdy t hes capolitiazsaw teiiolBn.e sideasst, h ea mphiboliti­
zatihoans g eneraglolnyes of art,h ev ariateiaounsse bdy i ncomplreetpel ace­
mento fp yroxebnye h orobieanrdees malclo mparetdo t hev ariatiionn s
colouirn deaxn dm ighbte m askebdy thesel.tw ast herefdoercei dteod
illusttroaw thei cehx tentth er ocki su nalterepdl obtyt tihnega mounotf
pyroxelneef itn t hes amplFei.g 6. showiss oplmeatphs o fm odals capolite
andp yroxene.
1ti sg enerablellyi evtehda gta bbrion trusiaorneas m phibolimtaiizneldy
alontgh eb ordearnsd h avea n unaltecroerde A.s alreamdeyn tioniedn,