Structural and metamorphic evolution during rapid exhumation in

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Structuraland metamorphicevolutionduring rapid exhumationin the
Lepontinedome (southernSimanoand Adula nappes,CentralAlps,
Switzerland)
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ry of thc Adula and Similno nappcs cluring cleconrpression.
'fhesc
1$o Lorver Pcnninic nappcs (Fig. l) arc well cxposcd in
lhe southern Moesano (Val Mcsolcina and Val ('illanc in
southc! n C;raubünden/Switzerland:Fig. 2). Thc earlv slagesof
lhc evolution of tl'rcsctwo nappcs ar-everv contrasting. l he
Adula nappe uDdcr$ent an Alpine ccl()gitc lircics nlctamor
phism undel P-T conditions of up ltl lJ5{)"Cantl 30 kbar (Hein'l
rich l9S6: Nimis & rcnrmsdorfl 1001). l lris [iIst mcl|norphic
ovcrpriDt pr-cdatesnappc stacking. R{icts- ol such cxtrcnrc
high plcssurc are absent in thc undcrlving Sinrano nappc and
a l l o t h c r l o w c r - P e n n i n i cn i r p p e s .a s r v c l l a s i n l h e o v e r l v i n g
middlc and uppcr Pcnninic nappcs. Thc cxact agc ol this highptessurc event in llrc AdLrlr napPc is still a nrattel ol dcbale
l)ul an EoccDc agc is indicatcd by fädiomctric cl|ting in thc littcrallv adjaccllt Cina Lungir unit ((;ebauer 1996) as \\'cll rs l]\
slr'ucturrl considerati(ms(Schmid et ai. l9t)6). Subscquent13arrovian lvpe nrctamo|phisnr of Lltc Eoccne lo Oligocenc agc
(c.9. Niggli .t Niggli 1965). referrcd 1o as ..Lcponlinc nletirnlorphism-. postdatcs nappe slacking. lt is one of the linrs ol
this slud) to unralcl lhe e)ihumltion hislor') ol the eclogilc llcies Aclula nappe lncl thc neight)oring tectooic units of thc
l - e p o n t i n cd o n r e .
C)n a mcsoscopic and nricloscopic sc|le rvc delinc "dclirl
matioD plrascs'primraril! otr the l)asisol overprinting tclationships. Mapping and corrclation ol lllgc scalc stluctLrfcswithin
a lrigh grade gnciss complc\. ho\\'cver.is morc clilficr.rltthan in
3 { ) 2 t . N l g e tc r , i l .
l o t ( J g l x t ) h l cr c l . r c n c c n r x p 1 ) l r h f s r u d ! i i r c r $ i t h l l l l o c l l l i l i c \n r c n ,
liLrrcd in lh. tc\t. ('ll: S\ilrer|rnd: L lirl!:circl!\r tosns \ill.rg']\: lfirngi(\:
|erk\:{ (\rdinrilc\ nr! lr,)|n lhc S$i\\ rrli,)rrrl k,tfugfafhic rrlp Srid.
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lower gradc tcgions rvhcre Mesoz()icscclimcntsat leirst partlv
prcservc their oliginal chatacterislicsand Inay servc as struclural nritrket horizons. Such nalkers ale not availablc rvithin
lhc complc\ gncisssclics. lhc existcnccol disrncmbcr-edsliccs
ol Mcsozoic nretilscdiments can onlv rarelv bc inlcrlcd on
purelr lithological arguments.Hcncc. thc llrgc-scale geomelrr
ol this nrultiply lbl(iccl napPe sl ck can oltcn bc dcciphctccl
with onlv limitcdcertirinl\.
Slrain nragnituclcsilssociir{cdwilh thc threc main clcfornrirtion phlscs !lr'\'slr'onglv in dillelerrt parls ol lhe studv arcil.
'l
lris r aliltion litcilitit(e! thc establishmcnl of rclalionships i'rctNecn nriner|l g.rowth and dcfornrltion phascs. Horvc\'et. a
pilrticulilr dcli)rnralion phase nrar displar diffelenl P-'l' conclitions lr'om plilcc to placc anclthis shoulr.lbe takcn into rccouIl
\ \ h e n c ( n n p a r i n tr c s u l t ! o b l i r i n c dl l o n t d i l l c r c n t l o c a l i t i c sW
. c
cnrphasizethitl hiqh nretaDr)rphiclield e|adients in P or T ntav
o l l c n b c i r r t i l i c i l l i n t h a t t h c c q u i l i b r i l t i o no f l h c n r e t a m o r p h i c
assenlTlagesml\ not havc occur'rcclsimullancouslv at diffor'cn1 locllitics ( lirdcl & Enri 1997).Wc har.e used nrctirpelites
1()con-eliltedcli)rn'Lrlionstructutcs wilh nrctantoaphisDr.
Fili\t,
11.thcil Isscnrblagesilrc palticulallv scnsili\,e to P-'l changcs
under irrrphibolite lacies condilions ancl. sccondlr'. abundant
nrica plovides pooclc()ntr-olli)f relirling lnicrostructulcs 1opilt
licular deli)rnlalion phasesirnd associaleclP T conditions.
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^N. Adul0nrppeiBA. Borgo!rtilinDr BG.BNsrlgmelssi
CA. Crtsim rnriformiCSZ.Crt\rre\e-Sorzazonci
GPZ.(innan-Prliiscr zoneiCZ.Gn)len2onc:ll-. In{rbric1in.:LA. Lcve.rirndnritnrmr
N1Z.Misoxerro ei
P AP
. . r g l iar n t i i b n n i S G A
S.i s o d e l Lgr u r i r n n i l b m i S ^ " S
. n n r i on l t p c : Z B D .z o n c o f B . l l i n z o nD. a s c n )
tly
ucrin
les
on
1ry
'ed
inteoscfbldingnra),confusethecor|e1alion(scc1cxt)'(1):CimadiGagnonc(ät1clGrondcta1'
casto|V.CalancaLretweenA'Trcsco|DentlndSclma(Frischkncch11923:Kundigl926)'(1):V'McsoIciDtltlroundsoazza(wcbcrl966|Be|lin92
a r o u n dP a s s od e l l äF o r c o l ( l { l i n n y 1 9 7 2W
: cbcr 1966).
Previouswork
1ale,a
dirnt
üy'e
lay
hic
ertes
ges
tnr
ar-
Theearliestworkersin the LepontineAlps (e.g.Studer& Escher1853)alreadydistinguished
three tectonicdomains.later
detinedby Milnes (1974)as Northern SteepBelt. Flat Belt.
andSouthernStecpBelt. The Northem SteepBelt is situated
soulhof the Gotthardmassiland separatedfront the southern
steepbelt adiacertto the InsubricLine (.,rootzone") by the
flatlyingpart of the Penninicnappcstack(Milnes 1974).Pionceringwork by Rolle (1881)and Heim (1ltgl) led to the interpr-elation
of the Adula gneisscomplexasa northwardsclos
ing.hugerecumbentanticlinc(a fold nappeor.,Deckfalte")by
Schaidt(1898)and Lugeon(1901).However.Wilckens(1907)
andHeydweilcr'(l9lll) alreadvshowedthat the bulk of the
Adulanappedoesnot represcnta coherentpre Alpinc gneiss
corebut rather consistsof severalthiD sljces(,.Teildecken").
sepalaled
fiom eachother by sedinlents
of inferredMesozoic
age.Preiswerk(1921)and Kopp (1923a)corelated particular
marble horizonsfound within the SouthernSteeDBelt with
correspondingsedimentaryzones.separatingindividualflatlying Lepontincnappesfurther north. From 1923onwardsthe
Swisspart of the Adula nappewascompletelymappedwithin
a short time span.mostlyby studentsof Schardt(Jenny1923;
Kopp i923b:Frischknecht1923;KüDdig 1926;Strasser1928;
Bcllin 1929;Knoblauchet al. 1939).A secondperiod of detailed researchtook place between1960and 1980under the
guidanceof A. Gansserand E. Wenk and mostof the southerD
Adula was remapped(Hänny 1972;Bruggmann1965:Fumasoli 1974;Blattner1965;Codoni 1982;Weber 1966).
Milnes (1974,197it)publishedthe first modern structural
analysisof the entire Lepontincareaand introducedthe conceptof napperefolding.He demonstrated
that the evolutionof
the SouthernSteepBelt is not geneticallyrelatedto nappeformationbut ratherpostdatcsit (Milnes1974).At the sametime
petrologicalinvestigationsfocussedon the extremely high
c \ , , l u r r ^I I r h . | . p r r i n r J , , m . . 1 0 3
\ r r u c l l r r i ,l r n Jn , r . L , ' r p l r i <
f ' i g .L S l r u c l u r r l n p s o l l h c \ t u d \ a r c r . l h ! d r l r i l r e c { ) r n t i l ! d l | l ' m H l i n n \
( 1 9 7 1 ) .\ \ r c b c r ( 1 e 6 6 ) .( i { l o r r i ( l ( r f i l ) . K n o l ) l r r l c he l r l ( 1 9 1 7 ) .l l r u g g r ) r x r r n
( l t ) 6 5 ) .K i i n d i g ( 1 t ) 1 6 )l l e l l i n ( 1 ( ) l r ) ) . . l e k c( r: 0 1 ) 0 )N. i e d e r b c r g .(t l l ) o l r ) .
F f i { c h b u l l r r( l l ) 0 ( l ) .D . r ) r ( )( l ( l 0 o )r n d l h i \ i r \ e s t i s u l i o r .l - f ! c n d i \ r h c \ u r r e u \
l i , r F i g .I
I ' i g .J a . S c h e m r t i cl c c l o n l cn r a l )o i l h e s l u ( l \ r f ( i r . l t s i t i r i n \ o l c r { ) s s( c c l r { ) n \
{ l r i g .5 i r 5 c ) r n d t r r c r s ( ) t \ i r l t l r ) . \ n r h r g . s c i l l r D : l i ) l d \ ( rh r n l i n . \ ) r n d
D l l i ) l r l s( l h i c k l i n e \ ) a r e i n d i c r l e i l .B L r c l s l r u sd e f o r c ( ' c c u r f c n c ! \o l c r l o g
i l e \ . $ h i l c ( l r e so . . u r r . r r c . s o f u l l
r.riic\.
l : i S . . 1 h .\ l r t ( ) l n r r i n i o l i r t i ( r ( S l . l o r i ) S l . r . ( ' l r k n ' , \ I ( \ u h i r ü \ ! i \ r r h \
i n \ c l ) | { ' l ! \ ( ) l , ) l i i r i o l il n
. l c r \ r lb c l s r c n! o n l ( ' L Il i n ! \ i . I 5
lrl Eurl)pcan colrtinental nlrrg.in itnd \\'erc sulrductccltowlrlds
thc south. bcncrth the APulirn nricroPlateand prc!iouslv accr etcclnriddle irnd uPper I'erninic unils cluring.thc llle EoceDe
( S c h n r i ( cl t u l . 1 9 9 6 ) .T h c A d u l u n a p p c d o c s n o t r c p r e s c n tr
c o h e r c n lt h r u s t u n i l o r n p p e l i k c n r o s lo f t h c o l h c r P c n n i n i c
l ) n s e m e n tn a P p c s .l t c o n s i s t so l l i t h o l o g i c a l l vh e l c f o g e n c o u s
{
lrnd inlcDscl\ clcfornted inrbricatcs. Horr'crcr. rrc colleclircl\
rclcr lo thesc iInbricirles irs thc Adulil nrppc. fhc irrLrricilles
r n c l a m o l p h i c l i e l d g f u d i e n t o b s c f v c d i n o u r s l L l d vl t c a ( c . 9 .
arc nraclc up (Jl nunlcrou\ tlrir slices of Vilriscan nrctagrlniNiggli & Niggli 1965) and on thc Possibilitl l() sludl isosr.irds
t o i d s . p a r a g n c i s s c ss.c a r c c o c c L l r - r e i c cos1 - n ] l l l i c si r r d u l l r a
in threc tlimcnsions (Klcin 197(r;Thorupson 1976). Van cler'
nrafics.and probablv Mcso,/oic nrctase(linrcnls.Lense\ of plrlP l a s ( 1 9 5 9 ) .H c i n r i c h ( 1 9 S 6 )a n d L i j \ \ ( 1 9 8 7 ) s h o \ e c lt h a t t h c
11'presclved n:ilic cclogilcs ar-ccomnonly cnrbeclclcclrvilhin
Adula nappe undcrwcnl r'egional high-plcssLn-cc()nditions
mctapelilcs ol unknown bul probabl! Mcsozoic agc. In conc l u r i n g t h e A l p i n e o r o g c n i c c ! c l c . F i D i r l l \ .s c v e l a l w o r k c r s
l r a s l . l h c S i m n o n r r p p ei s r r c l i l l i v c l ! c o h c r e n t l h r u s t s h c c l
slirrted to conrbine slluclural ancl pelrological mclhocls in
lnd prcdominilnll! consistsol thick prc-Nlcsoroic nretagrilDiorclcr to unr:rvcl the complex histor\' ol lhc Adulil DapPe
loids. In ils ufper pitr'l p|c Nlcsozoic nrclacluslicslnd aDrphi(l,itw I987: I'Lrs 1992: l-luber 1993: C;rond e1 lll. 199-5:
l T o l i t e su r e l r c q u e n l ( . l e n n Yc t a l . 1 9 2 3 ) .l n t h c i l l i ) n t a l p i l r t s
Partzsch I 99fi).
lhe AdLrla ancl Sinrano nal)pes are scparltcd l'l the iVlesozoic
c o v e r o l t h e S i m a n o n a p p c .[ e l c r f e d t o a s t h c . . S o j as y n c l i n c 'l'hc
(Fig. I ). To\yilrds thc soLrlhthcsc sedinlcnts\ycdgc oul itnd the
nappc edilicc *ithin thc rvorking areu
nappc bountlaty bccorlcs lmbiguous.
Ottterul rL'nturksantl rcgiorurl scttinl4
To\\'ilrclsthc norlhcast the Adula nappe is orcrlain bv lhc
-l'hc
lowcr Peuninic SimaD()lnd Adula nilppcs constilutc mosl
Misox zone. rvlrich is llso il zonc ol iDrl)ricalcs(Fig. l. Fig. J).
'l
h e s c i m b r i c a t c sl i r r g e h c o n s i s to f c l | s l i c r r i t r i n e s c d i m c n l s
ol the stLrdvIrca (Fig. -1.Fig..l). Thcv arc tlttr.ibuted1o the dis-
30.1 T. Nrgclcr ll.
F
(
b
S
in
al
B
s(
(F
ol
AI
na
as
Sc
is
al
tn
la(
cie
l9
Tr
do
re(
(8
Litltolr4ictrl srrtcL'.t.tit)ns
t illtin tlt( A(lulu ntlp( ltkl tttttppittg
ol rtultltc hotttttlttic,; itt Iltc sttttlt trtt
The Aclulir nappc pledonrinantlY consists ol pre-Mesozoic
melilllrirniloids anci Alunriniunr pool Inetaclaslics.lhesc donr
i n a t i n g l i t h o l o g i e sa l c l o c a l l , vi n t c f l n y e r e d w i t h n r c l . r p e l i t c s .
partlv cckrgitic anrphibolitesanclscalce Lrltranralicswhose pr()tolilh lgcs ilre unkn()\\n. as \\'cll ls *ith Mesozoic quarlzilcs
and nrarhlcs. In lhc lirll*ving rvc will discussthcse lithological
scqueDccsin conjunclion with thc (lucstion ol thc position ()l'
the nilppc l)oundarv l)clween thc Aclula änd thc Sinrnno nappc
south ol thc Soja slncline (Fig. -j & Fig.-l).
Thc promiDcnt ancl up 1() l5 m thick marblc h()I-izolrc\poseclut thc lop r)l l)izzo Clar-ois gcnerallf ilcccl)lcclto rcfrc
senl lhc nlppc bounclall- rvith thc undcrlvinll Sinrano nappc
(e.g. Spichcr l9fi{)). Wc havc sonrc objections 1() this view.
T h c r c n r i l r b l e sa r e e n r b e d d c du i l l r i n a s t r o n t l l l o l i a t c d s c qucncc ol palaqneisscsirnd lar,ersol Kfs-augengncissesand all
unils irtc irllensclv lol(led logcthcr dulins our sccond dcfol mation ph sc D2 (see Strrsser l92ll: ('ocloni l9ll2). Amphibolitcs
ilr-u frcqucnt ancl uplto l0 metels thick lenses of ultramalics
( e - g .i l b ( ) \ c A l p c S i n r i d i )n r a l a l s o b c l o u n d i n t h i s s e q u c n c e
rvhich overlics a sevcral hundreds ol metels thick unit donriniltccl b! lcss intcl]sclv lbliatcd K ls-" orthoqn cisses' (Codoni
rds
ac
tne
Lla
DiC
JUS
!- ly
Ltcs
lni.l-alrt
hin
oneel
lni
)hi-
uts
roic
he
he
l).
lls
It)82). Seleral aclclitionallavcrs ol nnrble. oltcn associated
lr ith cllcsilicates.arc prcsenl abo\.c rnd belorv this ptontincnt
F r ! .1 . : \ l i t , o f n r . i n . l r ! l c h i n : l i n , : . r t i o n ' t l l . l o ' : ) . S l ( r e ( ' | l ( n . A . 1
l\uhirf
m a r b l c ( K o p p l 9 2 l : ( i r d o n i l 9 f i l ) . J c n n l e 1 r l . ( 1 9 2 - 1 )a n d
eir !r\rn h\ rn\.1) li|rrr!,f\.
inte rl l,.l$!.n üo l()ur lir.' i' Li.
Strasscr (lt)2S) traceclthe sediDrcntsol lhc Sojl svnclinc into
another nritfble horizon li)trnd in a higher strLlclurillpositioll ilt
P i z T c r m i n ( s e e S t a u b 1 9 3 0 :H e i n r i c h 1 9 8 6 ) . A d d i t i o n r l l v .
nrarblcs fc comnronl\ li)und furthcr a\\r! fion1 thc suspeclcd
nappc conlact within thc stronglv sliccd Adulil nilppe. so lh t
{ B ü n c l n c r s c h i e f e r ) c l c p o siint ct dh c N o l t h P c n n i n i c( o r V l l i r i s )
b a s i nl o c a t c ds o u l h o l l h e E u r ( ) P c a nn r i l r - g i n( S t c i n n t a D n&
thc sig.nilicanccof tlrc nrarblc.lt l)irzo Clalo as il nrarker bcSlillc l99t)). Also gneissic slices intlistinguishlblc hom thosc
tween thc Adula uncl Simlro nappc is hiehlv c;uestionatrlc.As
i n t h . A d u l a n a p p c o c c u r ( P a r l r s c hl t l 9 l t ) .S c h n r i cel t a l . 1 1 9 9 6 ) depiclcd in Fig.3. lhc scquence in tlrc Claro iucil resemblcs
a l s o l t l r i b u t e t h c l i t h o l o g i c a l l r h e t e r o g c n c o u sZ o n c o l
rer! nruch thal lound irt Cina di (iaqnonc. \\cst ol lhc studY
I l e l l i n z o n a - D I s c i oi u. r l i l p o s e d \ \ ' i l h l h e A d u l I n a p p e i n t h c
areü. \!llclc various gnL:isses.
conlaining ultranralics and nar
soulhcfp
n a f t o l l h c \ \ o f k i n q i l r c l . t o t h e N o r t h l ) e D n i n i ch a s i
l-rles.lic on top ol ir nronotonoLrs Kls-gnciss. the so callcd
(Fig.l.l-ig..la)- li)\t'lrcls the sorrllleiisl.thc Nlisox /onc is cut
..Vcrzasca-Gnciss"((;rond ct al. 1995).Llltranrllic Lrodiesancl
ofl hr the l\'lioccnc lirlcola nolnrirl lault (NIc\fc cl al. lt)991)
eclogilcs lirund irrncclialelv abo\c the top ()l-lhc Vcrzascil
lnd thc Adula naPPe is directlr jurtaposed l() thc nc\t hi{hct
Gne-iss clisplal high plcssulc asselnblaqes trpical for thc
nappe.lhe midcllc I'enninic Ianrbo nappe. rvhich is regalclccl A d u l a n i r p p e( e . 9 .H c i n r i c h 1 9 3 6 ) .H e n c c .a t C i r n a c l i G a g n o n c
asil pirrl of thc Bliiruconnais nricroconliDcDt(Schrculs l9(.)--l: t h e o u p l ) c b o u n d l l y i s g e n e r i r l l vd c f i n e d a t t h c t o p o l t h c
Schnricla
e lt . 1 9 9 6 :I l a u d i o e t . r l . 1 9 9 - 1 ) .
V e r z a s c a( i n e i s s ( G l r ) n d e t a l . I 9 9 5 ) . I n a n a l o g v w c s c t t h e
R c s i o l a l h i g h l r c \ s u re m c l r m o ! p h i s m o l t h e A d u l a n a p p c
nappc' lrounclarr ilt I)irr(r Claro in u clceper p()silion thlrn the
predomid1lnl marlrlc h(n izorl and in'rInediatclv ilb()\ e the le ss
isallfihLrtcd1o Paleocencto Eoccnc subduclion ( Froitzhcinr et
a l .1 9 9 6 )l.- r o l n n ( ) r ' l l 1
l ( )s o u l h p c i r k I ' T c o n c l i l i o n sI e l a t c d 1 0
intcnscll li)liatcd Kli- 'ofthog.neisses"of Cocloni ( 1982).Howthishigh plessu|c sllgc progrcssi!clv incleasc li!nr blueschist ever-.nl) relicts ol high pressurc havc vet bccn li)und in thc
iacirsconclitions(ll kbar. -500 ( ) in thc Doflh lo eclositc l o v c r l v i n g s l f o n q l v l i ) l i i r t c db a s e o l t h c A d u l u n p p e i n t h c
. r s c o n t l i t i o n s( S { X l ( 1 > - 1 0 k l ' r r f ) i n t h e s ( ) u l h( \ / r n d e r I ) l | s
Claroarcir.
l 9 5 t ) :I l c i n r i c h I 9 ä 6 i I . i i \ \ l 9 f l 7 : \ , l c v r c c t r l . I t ) 9 7 :N i m i s . t
IJascrlon lithokuicirl clifferenccsthc successionlbuncl cirsl
Tfonrnlsdorff 2{X}l). lhis high-p|cssule trrelirorl)r'phisnr
is ltol
o l V a l ( i r l i r n c t ar r c q r o u p c d i n l o l i v c s r L b L r n i t( sF i g . 4 a ) a n t l
'littnbo
d o c u n l e n l c di n l h c S i m i l n o n a | p c r v h i l e t h c
n i l P p c c o f l c l i t l c d i n F i g . . i . ' l ' h e . . G r o v c n - z o n e "( ( ; Z l . . G r o v e n o rccorcls nrorc nroclclalc peak prcssulcs arouncl l2 kblrl
n a p p e s - i n t h e s c n s c o l K ü r d i g . 1 9 2 6 ){ n d t l l e . . ( ' i l l \ ä r c s e
(lhudin c1 rl. I 9t).1
Soazzazonc (CSZ) (l'r'ischknecht It)2-j:Wcl)cr 1966:HäDD\
).
S r r u e t ur lr r . ( l n r . r r u o r p h i ( . \ { ) l u r r or rn r h c I e 1 l n r r n c . l o m t1 0 5
1972)displaysimilaritiesto the nriscellaneorLs
gncisscsat thc towards the erlst (northcln part of FiS,.,1a ancl Fig. 3). lhe
bascoI thc Adula nappeat PizzoCllaro.The stronglyhclcro
mapping proposed in figure,la and bascd on thc correlation
geneousCSZ consistsof mclapclitcsrvhichcontainlersesof
given in ligurc 3. implies the existence ol r winclow of lhc
partly cclogiticamphibolites.senipelitesand augcngDcisscs. Simano nappe in the nridcllc Val Mcsolcina. thc Loslallo wirand alsoincludesnrarblesat its bascwhichreacha thickness
of
clow (Kündig 1926).Accoldine to our str.uctulalInappiDq the
20 nr irt PassoCalvarese.
The Groven7.one(GZ) do irlatrtly easl$ard cxtcnsion of this winclow nust be much largcr than
consistsof well tblirteclattsengncisscs
and g,arnct-plagiocl.lsc-pr.oposeclin previous studics (Bcllin 192t):Brussmann 1965).
nricaschists(scmipclitcs).
locallyinterlayerecl
with bandedanl
Thc colc of this window. exposeclin upper Val Boclcngo. is
phibolites.It alsocontainsar Lrltrarnafic
bocly.300m in size.at nritdc up bv thick. massivc Kli-gneisses rvhile its rvestcrn anci
Piz Gloven.This GZ is lessabunclant
in Al rich pclitcsand nir norther-n rnargins domiDantl! consist of senripelitic schists
mlrbles or eclogitcshavcbccn foundvet.
( H i i n n y 1 9 7 2 ) .H o w e v e r . t h e s o u l h $ e s t e r nb o u n d a r v o [ l h c
Easl of Val Calancaa 2(X)300 rnetersthick band oi palc. winclow remllins highl\ ilmbisLLoLts.
Thc krwcl l3asalgreiss.
massivetwo nlicaorthogneiss.
partlvdcvclopcdasaugengneiss which slill dcfincs the basc of thc Aclula nappe rvest ol Val
(..Basalgnciss'.
Kündig 1926:Rüti 2(X)l)r.epr.cscnts
thc basc Mcsolcinir. crn be traced eastwardsinlo moDotonous gneisses
of the Adula nappe(Fig.3) and is locallyundcrlainby amphi- in Val Cama and graduall,'-looscs its chalacterislicsin ter-lrrso[
(e.9.at the top ol Pizzdi Rüss)rvhich a mal-ker horizon lbr the basc o[ thc Adula nappc. The Lostal,
L.tolitcs
and calcsilicates
rrark the nappcboundarybetweenthe Simanoand thc Adr.Lla lo-rvinclorvprimatily results fron a huge D2 antiiblm. as uill
nappe.However.this Basalsnciss
canDotbc traccdwcstwards be discussecllIter.
crossVal Calancaand is abscntat PizzoC'laro.(bnversely.thc
The cxistence of the Loslallo rvindou,is additionally suplhick ..orthogneisses"
which deline thc top of thc Simano portecl bv the Llistr-illrLtion
o[ ]righ-pIcssuIc assemblages.Ret
nappewest ol Val Calancacannotbe tracedeastwardacross rogrcsscd cclogitcs (Fig..1a) are present in the CSZ closc to
l l r i \ \ i r l l L \ . f h e n r p p eh n u n r l a r rJ. . t i o I ] g l rt r ' l L l elrrlr D 2 t . r l d . Passodella For-colit(Wcbcr 1966:HciDlich 19fi6)norlh ol thc
in many placcsand no originzrlstruciuresuchas a distilct nty
supposeclwindorv ancl again sr-rrLth
ol this u,indolv at Piz Duria
lonitehorizorl.asfound at thc bascof the Aclulanappefurther (e.g. Hcinrich lt)ä6). Adclitional localities with high prcssulc
in lhc north (Partzsch199i.]).
is prescntin our studyarca.I1 is a s s e m b h g e sh a v e b e e n d o c L r n r c n t c di n o u r s t u d v ( F i g . , l i t ) .
possiblethat thc complications
clcscribecl
aboveoriginatefrorr
Garncl-amphibole-svrnpleclitesi11Vll C;rol1o.first dcsclibcd
isoclinallargcscalefoldingof the baseol the AdLLla
nappcdur'- b v l l r u g g m a n i ( 1 9 6 5 ) .t u r n c c l o u t t o c o n l a i n f r c s h d o n : r i n s
ing D2 in Val Calancr.
showiig thc cclogitc lacics asscmblageOmp + C;rl + Rt.
Howcvcr.the Basalgneis
is a valuablemarkerhorizoncast
of Val Calanca.Therc. Frischbultcr(2000)was able to trace
The strrctural hrildup
tho Simano-Adulat]appelloultdäryinlo thc castcrnflank of
Val Mcsolcinaand back westwar-ds
into nrirr-blc
lal,crswhich Rocks in the study arel. particularlt in thc Adula nappe. expedefine the base ol thc Adula nappc in thc lolvernrostVrl
r-ienceclextrcrrcdclormation and commonlv tlisplal'a wcll clc
Cirlanca(scc Fig.,1a).A major D3 antiform. the Pägliaan
vcloped foliation ancl slrctching lincation. Intcnsc and rcpeattilorm. is responsible
tbr thisliu ge scalccxcursionof thc nappe ed t'olclinudevelopcd almost c\clusivcly uoder amphiboiite lit
col)tact.Thc nrarblchorizonin the lower-nrost
Virl Calancais cics conditions. We found thr-ee rlrljo'duclilc dcformation
alreadvparl of the SouthcrDSlccp Bcl\(sco Fig. .1a)and cor- phases in our workinq arca rvhich mav corresponcl to thosc
rcspondsto thc so-called..Algaletta arble-..defincd in thc first described bv Ayrton ct Ramsay ( 197,1).
V a l L e v e n t i n as c c t i o n( C o d o n i1 9 8 2S
: t a u b1 9 1 6K
1opp 1922:
Strasser1921i).
l. I he first clelo.nratiolrphasc Dl is associateclwitll isoclinal
Across Val Lcvcntina the Aclula (= ClirnaLunga) nappe
folding ancl tire ibrmation ol the nrain foliation Sl ancl a
bccomcsextren]elvthin.The AlgalettaaDdthe Caslioncsmarstretching lineiltion I-l in ntosl parts of thc study area. Duble deline thc uppcl and lower boundaryof the Aclulanappc.
ring this phasc the Adula nappe was tl[LLslcd towards
rcspectively(e.g.Kopp 1922).Eastwardsthc Castionc-marblc
oorth onto the Siiniio nlppc. Simultancously. substantial
which dcfincslhc top of the Adula nappe renains in a steep
cxhumation flom eclogite to arnphibolite facics conclition
orientation and continucsstraight into the ..Paina-marble
occurrcd in thc Adula nappc.
lound cast of Val Mesolcina.The PainamarLrlcrvasmvloni- 2. During the second clelorrnation phasc D2 the establishecl
lizeclunderglccnschistlacicsconditions.lndmarksr latedex
nappe pilc was affccted b]' tight southwesl vergins lolds at
lral strikc slip fault (Fumasoli 1.97,1:
Heitzmann 1974.1975.
cliffelent scales. l'his delbrmation inlcnsilics towards the
1987)defining the southerDboundary of the Aclula nappe
soulh whcrc a ncw slrcchiDg lincation L2 and a new axial
(Fin.4a) all thc way 1o
againstthc Zone of Bellinzona-Dascio
planar foliation 52 developecl.Top SE shcaring palalJelto
Valle dellaMera (Funrasoli1974:Hcitzmann197.1).
the olienlätion o1 iblcl axcs acconrpaniedI)2. We proposc
The subunitsformingthe llat lyiDgpart of the Adula nappe
thal lhe Soulhclri Stccp Bclt u,as activc as a south dippinq
bctwccnVal Calancaand Val Mesolcinain thc no thcn parl
ductilc she.lr zone \!ith a r1onnal sensc ollsct during this
of the studyareacan be lbllowcd wilh somcccrlaintyfurthcf
stige of clelornratioll.
306
L Nagclcral.
3.
eat
tipl
elc
hib
hin
witl
ally
and
(Dl
are
maI
line
The
gen
mall
L2a
n
e
tn
)
is
d
ts
te
SJ
al
]S
rf
lill
S i m a n on a p p e
B (Nre)
rCZ
t
B' (ssw)
GPZ
BT
t
t;
Simanonappe
ptto
te
la
re
').
l
S mano nappe
.^]:"
.i,:"
)d
NS
Fig.5. Schematiccrosssectionsthrough srudtrarea.Thc posirionsofcross sccrions(A-A.. B B..C-C.,D-D,) are indicatedin Fig.4ä. Legend is the sameasfor Fig_3.
e-
ä
)n
se
lal
,uqs
ial
on
ed
at
he
ial
to
)se
his
3. Foldsof the third deformationphaseD3 relatethe flat belt
in the north with the SteepBelt in the south.In the soutl]
easternstudy area. where tight D3 folds are folmed, a new
strechinglineationL3 is observed.The so called"paglia(Bruggmann1965)resultstiom D2-D3
Schlingenkomplex"
interferenceol large scaletblds.
At first sight it may appearodd to presentfoliation and lineationmaps(Figs.4b and4c) in an areawhichunderwentmultipledeformationwithout atlributingthe displayedstructural
elementsto particular deformation phases.However, rocks exhibitingmore than one foliation can only be found in fold
hingesoI D2 folds and, generally,no foliation is associated
with D3 folding. Rocks with morc than one lineation are vifluallyabsentin the study area and it turned out that all fold axes
and/orstretchinglineationsol the three delbrmationphases
(D1to D3) are commonlycoaxial.Fold interferencepatterns
areof type 3 (Ramsay& Huber 1987).Hence.the lineation
mapsimultaneouslyillustratesthe orientation oI all stretching
lineations
and fold axes(Wcnk 1955)tbrmcdduringD1 ro D3.
Thestereoplotsin figures4b and 4c illustratethat foliations
gencrallydefine great circleswith an axis subparallelto the
mainstretchinglineation(L1 or L2) in any givenarca.Ll and
L2 aregenerallyassociated
with a cousiderable
stretchparallel
to the D1 or D2 tbld axes. We suppose that this linear
anisotropyforced D3 fold axesto form in a sub-parallelorient a l i o n( C o h b o l d& W a l k i n s o nI 9 8 l ) .
The foliation rnap (Fig. 4b) map displays the main foliation, commonly subparallelto layering,and the compositeD1D2 foliation. The gentle dips towardsnortheastin the northern
pafl are reoriented into steep to overtumed positions charac
teristic for the Southern Steep Belt by backfolds whose fold
axescloselyfollow the pre-existingtrend of the D1-D2 lineations(comparewith Fig. 4c). East of Val Mesolcinaa series
of large scalebackfoldsof the third generation(D3), rather
than a single backlbld, are seen to affect the foliations - and
hencethe entire nappepile north of the Painamarble (see
Cressim-Paglia- and Guardia-antiformsdepicted in the cross
sectionsof Fig. 5). At least one of theseantiforms seemsto be
cut by the post-D3 Painamarble strike slip fault (seesouthem
end of plofile C-C' in Fig.5). West of Val Mesolcina,however,
one single antiform, whose axial trace dies out eastward.connectsthe llat lying nappesto the Southerll SteepBelt.
All lineations shown in the map of Fig. 4c are defined by
elongatedmineral aggregates(e.g. qtz or pl) or aligned acicular minerals(e.g. am), while the fold axeswhich follow the
sametrend are not included.The strike of the lineationsDrog r r s s i r e l lr o t a t e rl r o m N - S o r e r N W - S E t o E - W . T h e N W
Struclural and metamorphic evolution in rhe Lepontine done 307
We ]1owdesclibethe mrclo- and mesoscopic
aspects
of the
thrce maior dcfornlationphascsDl to D3 in morc dclail. Mjcroslruclurcs
anclpreciseP T coDditions
relatedto thesepenc
trative ductilestructureswill be discussecl
later. In this wor-k
we coDcentlate
on the anrphibolitegi ade delolnrationlristory
of the Simanoand Adula nappes.The Dl of this studvpostclatesearlier-highpressurecleformationphasessuch as the
Sorrcdaphascof Löw (l9ll7) and/ol thc Trescolmcnphascof
Partzsch(1998)ar,)dMeyreet al. (1997).Post-D3defolmation.
e.g. dextral strike slip along the Paina marble and related
IitLLlts.
took placc at considcrablylorvcr gradc n]ctanorphic
conditions.
[re-D] unLlDl slnt(! tcs
F i g . 6 . P h o t o s r a p h s i l l u s t r a t i nDgl s t r u c l u r c s i
( r ) I s o c l i n ad
l i s m e m b e r e dD l l o l d s i n m e t a p e l i r e(sA l p C a l t l l r e s c C
/ ahnca).
r c t ( ) l d i n gt l p r c D l f o l i a t n ) n .
( b ) l s o c l i D a lD l f d d i . , e i b l d e d b v a t i s h r D 2 f o l d . l . o w c , A u , i g l i r g o r s c
( S c l n r a(.l a l a n c a ) .
( c ) S h l r r b l n d ! n d r $ o c i a l c d o b l i q u cb o u d i D ä g ci ü K l s g n c i s s c i\n d i c a l i n ga
s i n i s t r nsl h e a rs e r s e( = t o p N : I ' a s sd e G a n a n .C a l a r c r ) .
plungechanges
into a SE plungealonga culminationsituateda
[ew kilometersnorlh oI the SoulhernSteepBelt.This general
featureof progressiveanticlockwisclotation of lhc prcdomi
par.t
nant strelchinglineationsis typicalfor the entiresouther.n
of the Lepontine dome (Wenk 1955).Note. howevcr. that
thcscprcdominantlincationsarc not attributcdto oDesingle
deformationphase.
308 T. Nageler al.
In a purcly slructuralscnscthc D1 structurcscorrcspondto
the Zapport phnseol Löw (19f17).
They are best preservedin
the northernpart of the stuclyarea (Alp de ltescolmen.Alp
dc Gallan)whcrc thc Sl sc]listosily
is I1otslroDglyovcrprinlcd
by subsequent
deformationasis the casefurthel south.In this
nolthern alea. the donrinllntlbliirtioi is lelated to isoclinal.
D1. similarfolds (Fig.6a.b).Thc stretching,
lineationtypically
pnrallelto the N S
dips N to NNE anclis consislerltly
or-ieDted
strikingD I fold axes.Dismemberetlfolds(Fig.6a) indicateintcnscdclornation duringDl and no largcscalcDl foldshave
(shearbancls.
beenfound.Abundantshearsenseindicator-s
o
clasts,asymmctricboudins)on a mcsoscopic
and microscopic
scaleindicatetop-to N shearing(Fig.6c). relatecito nappe
stackiig duliig Dl. The Ll stretchiDg
lineationis delinedby
elongatcdquartz and feldspar atr,glegates.
amphibolesand
stringsof bouclinagecl
cornpeteDlrraterial.In rnetasedinreDts
and amphibolitesfound in the northernpart of the studyarea
all mincralswith a platy aDd acicularshapc are commonlv
alignedparallelto the S1-foliationand even within Dl lbld
hingcsno pre Dl mincralsarc disccrniblc.(lnly mclaclastics
occasionallycontain white micas forming discoldant microlilhonspredatingSl.
Bendingof the S1foliationaroundeclogiticboudinsdocumcntslhat Sl posldatcshigh-prcssurc
conditionsin thc Adula
nappe( PartzschI 998).Alons their rirnssuchboudins!rrecom
monlv retrogressed
to flarnet-bearing
amphibolitesduringD1
(Heinrich19ti6).Gnr.nel-olnphacite-benring
with
assemblages
in cclogiticboudinssomctimcsdcfinc an oldcr planar labric
(pre-Dl I l escolmen-phase
of Partzsch1998).completelvdis
memberedfiom Dl and only found in isolatcdtroudins.In
conclusion.Dl is relaled1()nappestackirlgin the lower Lep
ontine area.lnd postdatesan earlier eclogiticevent in the
Adula rlappe.The subsequent
phases(D2 and D3) describcd
below ovelprint the nappeboundariesestablished
during D1
(seealsoAyrton & Rlrnrsay1974:Grujic & MancktelowJ996).
D2 stt'!t(tur(s
Structures
of this phascarc dominantiD thc ccntralpart oI thc
studyareawhere subsequentD3 overprintis weak.This sec-
OI
lar
of
(1
D'
SO
th(
su
of
&
dis
ter
sol
wir
col
th€
1a,
19
su
ma
arc
ea
Fio
me
tifc
mo
elo
phu
&
wh
hin
tatl
con
sou
ma
Eve
StIC
dev
199
cat(
mel
clea
pre
met
the
tion
doIr
the
part
pos
the
Mineork
ory
rstthe
)of
LOn,
ted
rhic
lro
lin
{lp
ted
this
nal,
ally
{-s
inave
rpic
2pe
by
rnd
)nts
19a
'dy
bld
tics
mirculula
)mD1
lm)nc
d1sIn
epthe
)ed
D1
)6).
the
iec-
ond phase refolds the Simano-Adula nappe boundary on a
largescale.In particular,we confirm the existenceof a window
of the Simano nappe around Lostallo proposed by Kündig
(1926).The window results from an antiform formed during
D2.The northern limb of this antiform is affectedby a seriesof
southwest-verginglarge scale folds (Kündig 1926). One of
themis exposedright at Lostallo (seeFig.4), where it causesa
subverticalto overturned (= steeply NE-dipping) o entation
oftheD1 foliationon the eastemsideof Val Mesolcina(Fig.4
& Fig. 5a). Further south, at Sorte in Val Mesolcina,foliations
displaysubvertical dip over an approximately 3 kilometres
widezone (Fig. 4b). This steep zone, situated severalkilometers north of the Southern Steep Belt, is interpreted as the
southemlimb of the huge D2 antiform forming the Lostallo
window and an adjacent isoclinal synform south of it. The
Adula nappe is folded down and below the valley floor in the
coreof this tight D2 synform. This leads to the separationof
the Lostallo-window ftom the rest of the Simano nappe (Fig.
4a).The so called,,Paglia-Schlingenkomplex"
(Bruggmann
1965)in the southeasten part of the study area is formed by a
superpositionof D2 and D3 folds. The ,,Duria-synform" (Fumasoli1974) also representsa large scale D2 fold, folded
arounda D3 antiform (,,Borgo antiform"), representing the
eastwardcontinuation of the D3 ,,Paglia-antiform" (Fig. 4a;
Fig.5c). Hence, the ,,Du a-synform" in fact representsa former D2 antiform exposedon the southern limb of a D3 antitbrm.
D2 fold style strongly varies on a mesoscopicscale,from
moreopen to tight isoclinallolds, as a result of lithologicalheterogeneities.In the Adula nappe D2 is not the main folding
phasein contrastto other parts of the Lepontine area (Ayrton
& Ramsay 1974;Milnes 1978;Grujic & Manckelow 1996).
While a new axial planar foliation 52 clearly is presentin the
hingesof open to narrow D2 folds, 51 is rotated into an orientation parallel to 52 in the limbs and the overall schistosityis
consideredto be the result of D1 and D2 deformation.
North of the SouthernSteepBelt D2 folds are consistently
southweslvergent(Fig. 6b, 7b). The 52 axial plane foliation is
mainlydefined by synkinematicbiotite in leucocraticgneisses.
Even relatively open D2 folds often display a pronounced
Fig. 7. Photographsilluslrating D2 structures:
stretchinglineation L2, suggestingthat D2 fold axes initially
(a) View towards SW in the Claro area: At Torrone Rossothe marble exposed
developedparallel to the stretching lineation (see Stünitz
at the top of Pizzo Claro is doubled due to D2 folding by the tight D2 north1991).L2 is easilydistinguishedfrom Ll sinceshearsenseindiward closing synform north of Pizzo Claro (axial plane indicated) already
catorsrelated to L2 consistentlyshow top-SE directed move- m e n t i o n e db y K o p p ( 1 9 2 2 ) .
ment (Fig. 7c). Since SE-directed shear senseindicators are (b) Typical SW verging. narrow D2 fold in a semipelitic gneiss(Borcerta d€l
Lago, Calanca:view towards north; nole hammer for scale).Srch folds display
clearlypresenton both limbs of D2 folds, this folding is intera dislinct axial plane foliation and a pronouncedstretchinglineation pärallel to
preted to be coeval with top to SE sheadng. Within
the fold axis.associaledwith top-SE direcred shearing.
metapelitesthese shear-indicatorsare clearly associatedwith
(c) o'clasls in Kfs-augengneiss
indicating dextralshearing during formarion of
the 52 schistosity52 ( = top SE: Mottone, Calanca).
the S2-foliationand its characte stic mineral assemblages.
Interestingly,the locusof the onset of strong D2 deformation coincideswith that of the anticlockwiserotation of the
dominant stretching lineation fiom N-S to NW- SE. Because
the stretchinglineationstrend NW-SE (Fig. 4c) in the central concludethat top-N and N-S oriented Ll stretchinglineations
pa of the working area where D2 is best developed,we probecome progressively overprinted by top-Sw and NW-SE
Dosethat this bendins of the lineations results tiom D2. We
trendins L2 lineations.
StructDraland metanrorphicevolutjon in the Lepontine dome 309
ductionin strain intcDsit\':D-3li)ldsat all scalcsbeconreprogressivcly
morc opeDitndccascto existnorlhwards.
Thc CrcssimaDtili)rmis thc nrostfarnousof thescD3 folcls
PizCressim
(Kopp 192-1b
) and rvcproposethc tcrm C ressimphaselor this
stageol dcli)rmati(m.At Piz Clcssimthis li)ld is rilthcr open
(Fig. tta). thc lold axisdips 1()the NW anclthe axial phne is
vcrtical.In the lowcr Val d'Arbola the antilirlm is huldll visible anv nrore anciceasesto cxisl acrossthe Val Mesolcina.
Conversclv.the anlili)nr tighlcnstorvardssoutheastin Ital!'
ilnd the axiirlplaneprogrcssively
rotatesfrom a NW-SE strike
i n t o a w - E s t r i k c ( F l i i n n ] l t ) 7 1 :B l a t t n c r 1 9 6 5 :H c i t z m a n n
l97J:Bergel ct al. 1996).The Pnglia-antitilrm
situatcdIurthcr
west(Kopp 1923b:Bruggmann1965)exhibilsexactlvthc same
charactelistics
anclcan lrc traccd ovcr a clistanccol 25 km
throughthc studvi]r'cil.Westol Val Calancaone largcscaleEW-strikingbackfold.rclcrredto ls..Lcvcntina Antilortn'. rclirtcstlrc llitt bclt in lhc Dorth to the stccp bclt iD tlrc south
(Codoni l9fi2;Fi-q.;l).Thc Leverltinabacklirlcldisplavsconsiderablegeomctr-ic
dillclenccsto llnd is disconnectcdlr1)mthc
otherD3 lirlclssituatcdfurtherc.sl. In spitcof thisdisharmonv
we rcgardall ol thc abovedcscribedfolds10havelornlcd co]l
tcmporancouslyduring D3 becaLlsc
thev itll rcpreser)1
backlirldsu hich rcoricnt the gcntlcdips iü thc nolth to the Southcrn SteepBclt. Eastol the rvorkingareaD3 foldingis synnag
n)aticwith thc Bergcllinlrusionanclfoldsits basc(Dlvidson et
itl. 1996).Sincethe Uergell bittholith intrudesa prccxisting
slccp zonc. Bcrgerct dl. (1996)algucd thlt lhc forDrirtionof
partsof thc SouthernSteepBclt prcdateslhc llerscll inlrusion
and hencelhc abovc nrcntionedD3 folds. l'his indic|tcs that
the stecpcningof tl'rcsouthernpafts ol thc SouthernSteep
-l'onalc
scticsadj;rccntto thc lnsubric
llelt. in palticulartl'rc
linc.pre-datcsD3 folding(conrprrcwith thc prc--i2Ma old..2.
phase' ol Spillnrann1993).
birckfoJding
While I)3 foldsdo not sho\\'apronouncedaxialplanefoliirtionthey cxhibit a disliDctlincationparallclto F3 wilhin the
Paglia-Schlingcnkornplcx.
This lineationis dclincdby synkincrnaticbiotite flakes.qui,rrtzfibc|s and qu ttz-sillim.rnitcrods
(so called..Fascrkiescl). It hasbecn interpretcdas a crcnulatiotl oI intcrsectionlinertionb1-plevious uthors(Hubcr 1993:
(irond et al. 1995).However.clualtz-sillimanite
rocls.clearlv
F i g u . P h o t o g r : r p hisl l u s t f r t i n gD : l s t r u c t u r c s
postd.rtingI)2. fornr elongatcdptcssurcshadou'sparallelto
( , r ) L a r g es c r l c .o l ) c nD l r n r i l i n n a t P i z( r c \ \ i l r l( u f i r c r v r ' l d A r 1 ) l i rU. . r \ o l
(Fig.8c).indiclling a considerable
D3 fold arcs in metapelites
c i n r i \ i c \ r ( ) l h e ! ) u r h ) . a i c s s i m a n r i l i n r nr n d r r a c c so l p f c - D - if ( t i r l r ( J n( t h i
d a s h e dl i n e s )r r . i n d i c a r € d .
with constrictioDal
stretchparallelto D3 lirld axcsassociatccl
( l ) ) O p c n D : l s n r r l l s c a l ei ( t d s ( V a l d A r l ) o l r . M e s o l c i r ) r ) .
part ol thc studvarca(secalsoSteck
strain
in
thc
southeastcfn
( c ) S i l Q t z r r x l s ( . . F r s e r k i l j s c)l i n p r e s s u t c\ h ä d o $ s o l g r n r c r \ d ! l i n i r r g D l
lr)t)g).Grlnitoid r'ocksexpericnccdmignrittistrtion
during Di
s l r c c h i n gl i n c a t i o ni n m c t a p c l i t c sD. - l s m t | l l s c l l e l d i n g i s t i S h t . p f l l l l c l l o L - ' l
(
;
r
o
n
o
.
pockets
par|llel
bv
(
u
p
l
)
!
r
Iolding.
as
documeDtcd
nrelt
oriented
tcr
Vrl
vrl l\'1.!)lcin!).
r n d s ) n m i s D r t i l iicn l h i \ a r c r
D 3 a x i a lp l a n c s( H u b c r 1 9 9 3 ) .
ID tlrc centrirlpaft of the studyareiLthc open D3 lold axes
occasionallvdisplav a small but disccrrrableanglc with the
D,l structrrrcs
dominail lincation.l-his indicalcsthat D3 rcfolds Ll and/or
piltt of the studyareaD3 foldsstr.ikcE-W
L2. cven thoughthe l)ll fold axcsare contntonlvcoaxill wilh
In the soutl]castern
(13r'uee Ll and/orL2 . At Piz Ctessin.lor examplc.dominantlirlding
and lbrm tight foldsin the ..Paglia-Schlingcnkonrplex"
nrann1965).l'owardsnorth thcl gradualll'changetheir orien- visibleon thc outclop scaleis rclalcd to D2 \\,hilethcsc D2
an'
talion towardsa NW-SE and. Iinally. a N-S orienteclstrike axial plancsiu-ebenl around thc large scalcD3 Cressir'n
(Fig. 4). This rotationof the lbld axesis associated
with a re'
tili)rm which formeclcoaxiallvrvith F2 (Dunro 200()).Hcnce.
E-W
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S l r u c l u r aal n d ü l c t a n o r p h i cc v o l u t i o ni n t h e L e p o n t i n ed o m e 3 1 1
Corrclation ofthe rnciamorphic ert)hrtion nith the
dclorüation lristorJ
I - i ! . 9 . P h o r o m i c r o c f i ropfl r\ l n r l ) l c l \ l l l . I ' r e k i n . m r r i Icl ) e n g i r (( 1 ' l r . l ) F
\ r r l h . d d . d i n l m r r i \ o l n r ( r r .( n l . s s f e c r \ s l n l l i / c df h c n g i l c ( l ' h c l ) . K \ . P S .
( i r t . r n d Q / r . w i t h i f t h c d c \ l r r l s h e l t r h i r n d( = T o t ) N N E ) h L o r t cg r r ) w si r r k
i n e n r . l l i c i r l l \l .l o \ e \ . f . D r o \ r( ' l r h . b i o l i r ! t o \ l d i r l ! s t h t l i ) l i r l i ( n ri n l h ! \ e c
ri o n .\ \ i d t h o l \ c . r l c b r r : 5 m n r .
li)lded bl trvo plrases (D2 and Di) thc mirin lblialions in this ar-ea Iin-m u greal circle. (sle rcopll)l F in Fig. 'lh).
lllhough
'lhis
clcar'lvindicatcs that open l)3'lolds developcclsubpatallcl
1() a prccxisting D2 planar antl lincar sllrLctulc. Cohl)olal &
W a t k i n s o n ( 1 9 8 1 )p r c s e n t c da p o s s i b l ce x p l a n i t t i o lfto t . s u c ha
behaviol bY proposing lhirt an c\istiDg arial itnisotlof\ ol'
rocks nllv control thc oricntatioD of subscqucnl litlcling phascs. Hencc rve belicve thirl it is thc pr-e-cxistingNW-SE striking
L 2 a n d t h c N - S s t l i k i n g L l s t r c c h i n g l i n e a t i o n s\ \ ' h i c h m a )
h a v e i n d u c e d t h c c l e f l c c l i o no f t h e D 3 l i r l d a r c s ( s e e F i g . . l c ) .
'Ihis
hvpothcsis is in accordlnce \rilh lhe obscrlalion thitl
nraior D3 lblds open to\fards north bcciluse lhc D3 li)ld itxis
oricntatiorls bccome pr-ollrcssivelvless suitahlc lin acc()rnm()clating N-S-dilectcd sholtcning associatcdwith thc fornration
o l t h e S o u t h e r nS t e e p B c 1 1 .
\\'e n()\\' corrcliitc nliDcral irssenrlrlilgcsilrrd llssocilltcd It''l
conclitionsrvilh micr'oslluctnrcslbnncd clufing thc lhlce nritiot'
d c f o r n r a l i o n p h a s e so u l l i o c ( l a b o r e . F o r c i t c h d c l i ) r l l r a l i o r l
phllsc I)l-D--i onc t\Pical sanplc is p|csenlcrl in dct.til inclr.rcli n s g c o c h e r l r i c i r el s u l l s ( l u l ) l c l ) . [ ] i l c h s c c l i o n s t l r l s w i l h i r
appcilfancc ota pilr
descril)ti()n()l lhe ()\cr ll nricr'()slr'ucltltal
'l
(
)
h
s
c
r \ ' u 1 i 1 ) inl rsc d e r i \ e d
p
h
a
s
c
.
hcse
licultr clefornration
(Nllcl llX)0: Nirgcl
sanrples
ol
metilpclitcs
llon nrorc lhan 2{)0
\anrple\
Ii)r
thrce
sclcctcd
crluilil'tlitrnrphusc
ct al. l00l).
lhc
cliaglunrs(Dc ( apitani & Illown l9fi7: De ( lpitrni I99'1) irrr
'l
usecllo discus\ P crrnditioos and l)llasc rcliltions. Such diir
granrs plovidc stllblc irssenrblages.
nrinel1ll nr()ales-urld conrposilions ol soliclsoluliors li)r a fixeLl bulk chcmicrl corlrposi
lion in l)-T \pilcc. \\'c uscd thc corlrposilions()f rcfrcscnlali\c
\ l " r r r i I I \ I n l h r r r\ c ( l r , , r rl\r , ( l L r i \ . l l l ( i r l l , L (r ,l ) r r l l r , r . r l r ,lr\rrl.\s e n t c r li n T a i r l e I ( N i t g e l e l a l . l 0 0 l ) . W c l i ) c u s s c do n s u c h
p h a s ct l i a g r i r n r sr .\ t h c ) ä l l o \ \ b o t h t h c q u i l n ( i t i l t i \ ct r c a l n r e l l
o l l s i n g l cs l l n l p l ei t n d t h e c l i s c u s s i oor lr- m o r ' cg e n c l l l a s p c c l s
of phit\c relIlioDs ancl theit significitncc.Thc thernrod\.nIrtlic
pr-ol)crties ol nrinerals \\cIc takerl lrcnr the diltirbasc ol
Bernrirn ( I 9SS.upgl1rrle19t)l) anclslightlv morlifiecl s plescnt
e c l i n N a g . c lc t a l . ( 1 0 0 1 ) . , \ l l p h a s c sp r e s . r l i n t h c d a t i t b l \ c
wcr-cconsiclclcdin lllc cirlculiltions.
I:irst rh litrrtutirut pl,ast
Thc SI foliation lirirnccl *hilc grrnet. quaflj/- phcngitc- pirras
o n i 1 c .p l a t i o c l a s cb i o t i t c . l n d k l i r n i t e w c r c s t a l ) l c r s r o c k
. llurolite irnd
l b r m i n g m i n c l a l s i o p c l i t c s a n d s c n r i p e l i t c sS
c h l o r i l c c t i n r r r r o n l lo l c r g r o u ' S l . I ' h c n g i t e sa l i g n c c li r t S l a l $als shorv highcl Si-conlenl\ \\lren c()Inpareclto p()stkinonllltIn Sl. srnkinemirlic
ic oncs (scc 1|lso Plrl:/sch l 99N:Lij\\ IL.)87).
gr'owlll of biotitc ancl plagioclaseil lhc e\pcnse ol {ilrnct lnd
\!lli1c rrticlr is t'rc(lLleoll! obseNcd. HoNc\cr. lhe \\hi1e
n r i c a / b i o t i t er l t i o i s g c n e r l l l \ h i s h i n S l a n c l l h c t c i s n o c r i I)t)st D-1.\ttuclut(s
c l e r c c l o r - b i o t i l eo r p l l g i o c l a s ct o c o c x i \ l w i l h k y | n i t e \ \ , i 1 h i n
Sl 1l'atzsch lt)t)S:l\lc\ie l99t)h. Nrllcl l(l0l). Nlclirhusicrocks
S u l i s e q u ( . nl lo D . l l , r l . l i r Sl l l L \ r , u l l r ( i f nS l ( c l \ l l . l t \ \ i r s i r l l ( c l c q L r i l i b l a t e lcol g i r r n c l t r e r f i n { a m p h i b o l i t c sd u r i n t I ) l
ccl bv considcrablc dexlrll sttike slip orovenrcrts llhich took
w e s e l c c ls a m p l c ' l N l l 2 l t r r n ri l ] o c a l i 1 "i n t h c l l e s c o l r r e n
pl ce uDdcr gr-ccnschisllaciesconditions. Nor-1hol the Insubric
line thcsc dextrirl moYenrcnts Produccd clislinct ma.ior shcat' z o n e .c l o s e1 o C i n r a d c G a g c l r r f. o r c l i s c u s s i nDgl c l u a n t i l a t i r c
l y . ' l h i s s p c c i r n e nc o n l a i n \g i r f n e t .c l u i t r t zp. h c n g i t e .p a l a g o n i t e .
zoncs irDclassociirleclRicclel laults. ol which thc Plinil lirult is
(Funl
soli 197-l: Heitzmann 197-1. k r n D i l e r n d . L l t i l e\ \ h i c h n ) i t k eu p n r o r - ct h i r n 9 5 ' 1 1( ,) l l h c t h i n
lhc most pr-onlincrrt onc
I
n
S
o
u
t
h
e
r
n
S
t
c
c
p
l
l
c
l t t h c s c d e r l r ' a l m o v c n r e n t s s c c t i o ! r( F i g . 9 ) . I n r d d i t i o n i r i c r t i t en. l i r g i o c l a s es.t i i u t o l i t c .i l 1975). the
clcarlv overprinl callicr steel)lv plunging lincittioDs li)rutecl nlel]ilc itn.l zircon occut. Thc lirlialion is delincd b-,-(luilr-tzrib
b o n s a n d u l i g n e c ll a r u c p h c n u i l e l n d k \ i l n i l e g l r r i n s .S n u l l
Since thc lilttcr (lc\eloDe(l uDdcI.condiclLlringbitckthI.Llsting.
a n r ( ) L r l t s( ) l P h e n l i t e a r e a l s ( )p r c s c n t i l s l ) ( ) s t k i n c n r a t iIci n c
tiorls of the highcst anrphibolite llcies. irs indiclled b\ synkinegnrircd agglcgatcs. K\,anilc displlvs slighllv cornxlcd gririns
\\e consider
nrrtic K-lcldspirl sillimanile-beilring llsserDblrges.
* i t h r a g g e cgi l a i n b r r u n c l a t i clsn t l i s c l e a r l r d c f o f n r c d d u t i n g
hackthrusting lcross thc Insubric Drvlonite bclt to bc coeral
D l . i r s i s i n ( l i c i l t e ctl) v k i n k i n e . S \ ! i l n r l so l s I r r a l lg i r n r e l si l f e
with D3. Howcvcl. \!c correlatc thc afrovc clcscriLre.l
l)ost-DJ
nt()stl! ssl)ciirled\\ ilh borrtlirrlgetlcluarlz(lonlains. I'alagonile
s t r i k e s l i p \ \ , i l h b r i t t l e d c x t r - r lo \ e r p r i n l o f t h c I n s u b l i c n \
is scrr|ceanclaluaYs ilssociillcd\\i1h aligncclphcrlgitc. Thc nrrlonites along thc ..-l'onalcfault illrd rel lcd Ricdcl iuults (Fujolitv ol biotitc ancl plagioclirscposldatesS I . but lhcv mrv ulso
nrusoli 197'1:Schmid ct al. l9SC)).
-l ll
T. \r!.r er rr.
-I
rLl-
.ll
c(l
lcl
iit
-
l
rch
,ltI
cls
nic
()l
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irs_
rck
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rt i c
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rilc
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cks
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rin
itll)
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ine
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lltt
i!c
rit.]llt-
rl\()
r u p p e rrrlIu r i n gs h e a l b a n c l i r r n r a t i o ni l t i t l i t t c s t i t g eo l I ) l ( l r i g .
9 ) . Ä l c * ' s m a l l s l u u r o l i l cc r \ s t a l so \ ' c I s r ( ) ws \ l ] D l l h c n g i l e .
'lhc
c h c n r i c a lc o m p o s i l i o r t0 l p h c n g i l c s \ ' r f i c s b c t \ \ ' c c l t6 . 2 0
luncl(r.()0Si ir.p.f.u.1 I rhlc I ) \\ ith prck incorirlic pl)rlh\ roblu\l\
s h o r r i n gt h c h i g h c s tS i c o n t e n t .E r c n i n d i r c c t c o n t a c ll ( ) k \ i l r l
r l a S i - c ( ) n t c n tusp l ( ) 6 . 7 0 S i l r . p . l . u t. r c r c n t c i r s u l c d .P c l l e c t l r
l l i t n c c lg l i r i n sd i s p l a r k r u c l S i - c o n l c r l s( ) l ( r . 5 j ( r . 7 0S i a . p . l . L r .
-l
I
I
\ t j l c i n c o n l a c t1 0 b i ( ) l i l ct h e S i c o n l c n t{ ) l P h e n g i t ci s t h e l o w _o
c \ l ( 6 . 1 0 6 . . 1 5S i a . p . l . u . )(. i r r n c t z o n r t i ( ) r i s c o o r p l e \ .I n n r l ) s l
5
c)
g r r i n sl \ o d i s t i n c ts h e l l s\ \ i l l l i r r e l i l l i \ c l \ h i ! h C i t c o n l c n t i t r c
f
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(L
r ' c c r r r c l cbcr i g r a i n l r o u n d l l I i c sd i s c o r L h r ttt( ) l h e i n l e l n r l , / o n i l
lion l)irtlcfn and bv ir r'iscin lrbunclanccr)I Mn-coltlcnl 1()\\'ilr(ls
t h c S f i l i n b o u n d a r \ ' .1 l l i s l c i l t L l e i s b c s l c l c v c l o p e cul , h c l c p l i r ! i o c l l l \ c l l n d b i o t i l c i l r c p r ' e s c n t\.\ ' h i c h( ) b v i { ) u \ l \ ' 9 r e \ i t t l h c
. \ f c l l s c ( ) l g a l n e t . - l h t t s .t h c e n t i r c , / ( ) r l l r t i ( )Pnr l l l e r np r c ( l l l l c \
r L- r , , ' . \ t l ln. l L 1 i , , t r.t (' L ll ' l . r : , i , \ l i r \ ( .
I h c p h r r s cd i a ! . r i r n lro r s l r l r p l e I N l l l ( l : i g . l 0 ) p r e ( l i c l \i r n
o l d c \ l r \ s e n l b l i l g cC i r l r ( ) 1 , /+ P h c + I ' g r K \ ' ( l ) l o h e s l i l h l c
Temperature
i r b o \ , cl c m p c r a t u r c s( ) l 5 N 1() r n d p r c s s u r c so l l 7 k b l t . I ' h c n I Cl
(
r
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7
0
g i l ! s$ i t h S i c o l r l c n l \o l
u . p . 1 . ui n
. t h i s a s s c n r b l i r gi ne e l i c i r l c
Iii!. 10. f(tri ihriunrt)htN.dir!rrnrcrl!ullIdli)r
r.pfcs$rtllit!don]ai ol
| r . \ \ u f c \ o l i l r o u n dl l k h u r ( s c . S i c o n l o t r l ri n F i g . l 0 ) . ( ; u r n e l - ' r ü \ r l . l \ : l l ( l . r l , l r l ) T h c ( l i u ! f r r ( l j \ t [ r \ \ t h .
Ir'.(li.rrJ (lFriburi(m {)l'
(
(
i
f
c
c
n
I ) h e n s i l ct h e r m o m c t r \
& I l c l l n r r r n l 9 S l ) i l l g r i t i n rrirhld r*f1lrhlr!(' rdcordinc l() lhe rhf'rnr \ü.rnric
trot!rlie\ ()l phrtse\df
b o u n c l i u i cbsc l \ \ e e r rt r r r n u l u n c lp r c k i n c n r a l i ch i s h S i , I h c n t i t c
l r n . L l i l h . ( l i r t r h r \ . ( l l . r ü r r n - l ( ) f i f i .u t ! ' i r d e ( . r : : i d c l l l s i n L r t i { ) nf r o d . l s l i n b i
o r i r ! - c h l o r i l ! . r L n ( 1c h o r i l o i c l : I l ( n i ( l e i r Lr o l u l i o n n r o c l . l s l ( i r g r f i r ! r ( ß f r m l t n
\ i c l ( l \ l c D r p e r i r l u r ei \r r o l r n ( 6l - 5 0C . I h c s c c r r n d i t i o r ](s6 5 0 ( /
( ) 0 ) .p h . f g r l . ( U i r s s l n r r r .
r.(l S/furkIt/i).
pl.rgiochse (l1rhfl r.t Lindslev
> l 0 k b a r ' ) u g | e ew e l l w i l h l ) | c s l i m a t c so l t h c 1 ) r c - D lh i g h p r c s
I { I N S ) . n r u r o l r l ( ( N i r ! . l . l a l l o i l l ) l r r ( h l L ( l c l . n c k ) s . sr h . l , I s | r c c \ \ h r r . l
\ L r f cs l r t e i n t h i s i f c r ( N l c \ r c c t r l - l t ) 9 7 :l V l e r i ce t a l . 1 9 9 9 b ) . d i \ l r r r c l r \ \ . r r r l J i r g . L \ \ l l b l . . D r ' h r ( L l l r . . r f t r ! \ r n t
contouf( {)l Si contcnl rn
l J L r f i r )L! l . c o I n f r c \ s i o n p
. h e n g i t c i n a s s c n r h l u q cI s h o u l c lb e
I r h r ( S i r t l L r I l h e i r r ( t r \ i n d i ü r t c \r h . \ u r o \ . d P T | r r l r .
r o n r ü/ \ l r i c h c f t h r ( J u ! hk \ l l n i l e c o i l \ ü n r l ) l i ( ) nI .r ( ) rt h c l ) r c \ c n l
l r u l kc o n r I o s i l i o nk \ l n i t c i : r s c d u p r h c n I r h e n g i t cr e a c h c sl l S i c ( n r l ü r r\ l i g h l l \ ' l c s s t h r r n 7 . ( rS i a . p . l . u .i r l p l c s s u i e sb c L r u l 7
k b u r ' .l h c | c s u l t i n si l s s c | ] r b l i l gi sc C i l l + l , h c r P q + Q t z ( l ) . I n
t a n r p l c l N 2 l 2 k \ N r i t e o l t h c h i g h p r c s s u r ei l s s c m b l i l g c| \ l s
Assul]ring locill cquilibliunr rvith kvanite. thc Poslkinematcor'roclcclbul il consi(lcfllblc rnlount \till rcrrainerl lrs ir
ic assemtrlagc(i|t = Qlz + Phc + llt + Pl + Kr coulcl bc used to
m t l l \ l i r b l c p h a s ei n t h c l t r c k . - f h i sp t c \ c l t l c d c o m p l c t cc q L l i l i - i n l e r - p o s t k i n c n l i l l i cP - T c o n t l i t i o n s * i t h t h c r n r o b a r o m e t r r ' .
h r a l i o no l f h c n s i t c ( l u r i n ! d e c o m p r e s s i ( )\n\ .c i n l c r l h i l t c c l ( u
I N V E Q - t h , : r ' n r o b a r o m e l r -(\( i ( ) r d o n l 9 9 l ) o n s u c h a s s e m i l c I i r c i c \c o r d i t i o l ] s .P r c s c l \ c c li n p r c S l P h e n g i l ep o r f h \ r o l ) b l a g e s \ i e l ( l s c l ) n d i t i o l r so l i t p p r o \ i l n a t c I v 6 5 0 ( / 1 0 k b t r .
lllsLs.
{rfrrc1.tncl kvilnitc Ir'cclirleS l. I hc Si-contcnlsin lirr'gcr'c
Howcvcr. ull rc\ul1s hlvc unsllisfying larqc LrI]celtiantics
c f ! \ l i r l l i / c ( pl h e D q i t cd c l i i r r { S l a r c s c n c t i l l l \ l o \ \ ' c r( 6 . 5 0 6 . 7 0 \ h i c h r n i r ! i o d i c i r t e t h t n o l e v c n l o c a l c c l u i l i b | i u m r v a s
S i i r . p . l . u) .a n d i n c l i c u t cl c c n s t a l l i s l l i ( ) nd u f i r l t c l c c o n r p l c s s i o n . a c h i e v c cll i t h k v i l n i t ea t ä n r p h i b o l i t cf a c i e sc o n d i t i ( n r s .
l l i o t i l e i l n ( l p l r g i o c l i t \ co n l \ o c c u r i n r h c a r b a n c l sc l u r i l g l l t c
\\1e concludc that although lhis sample erhibits sisnificrnt
l i n i r \l l l g e \ o l D l d c l i ) r n r i r t i o rl t P T c ( ) n r i i t i r ) nosl 6 ( ) ( )6 5 0 (
disecluilibliunr. thc cquilibriunr ;Thascdiagranr prcclictsthc obi t n c ll l k b l r ( s c e i r \ \ c n r b l i r ! e \- l a n d l i n l : i l . I 0 ) . I l o r r c r c r ' . s e r \ c d n r i n c r i r ls e c l u c n c ei r i r c ( ) r - r e col l d e r . H e n c c . i 1 c a n b e
l h c s cI ' l c s t i m a t c sr c ! . u r d i n gl h e l i n ä l s t r r g c rsr l l ) l r r c o n l \ i r p
u r e d t o d c r i v c i r p p l o x i l n a t cI ) - l c o n d i t i o i s i n t c l a l i o i t o t h c
grcw
(icli)fnr:ltion sttuclurcs. In thc norlhcrn sludv area
bccause
l)iolilc
ill
lhc
e\pcDsc
ol
il
n()t
observecl
ln)\rnrillc
I)rohablv
l i t l l r c c l u i l i b r a t c df h c n ! i t c u i l h i l S i - c ( ) n t c nhl i g h e r t- h a n p l c
lhe foliiltion Sl lirlDrcclcluline clcconlpressiol,r
ill lcmpelatures
d i c l r di n l i g u r e 1 ( 1\.\ ' c c n t p h i r z i stch a t t h c o h s e r v l i t i o nisl \ l n t i n e \ c e s so l 6 ( ) ( () . I n m c t a f c l i l c s t h i s i s i n d i c a t e db r t $ o o b
p l c l \ 1 l l i l f c r ( ) 1i n c o n l l i c l \ \ i 1 h o t r r \ t i t t c n l c D lt h a t k \ . i r n i l e scrvatioi\. Iiirsll\ . in k\ anite beaiin{ assentblascsAl-contcDts
L l o c Isr ) t c o e \ i \ l \ i t h b i ( ) t i l co f I ) l a g i o c l a si cn S I s i n c ek r a n i t c i s
i n p h e n g i l c i n c r c a s c csl l n k i n e n r i r t i c a l l vt h r - o u g hk v l n i t e d e
intarl)fctca
r ls a I n c l i r \ l l l ) l ch i g h p r c \ s u f ct e l i c l . P r c t s u f c sn t U s l cooDosili()L Sccordlv. thc onsct ()l c()lltinuousrlhile ntica clec c r l I i n l ! h r v e e \ c c c r l c dI 0 k h a r c l u r i n g I ) L I h i s i s i n . l i c a t c db !
c o p o s i l i o ns l I r ' l ed d u r i n s l ) I ( c . g . M s + ( i r . 1= l l l + A l : O ] +
q
1
1
)
$
l
h
(
)
l
s
l
a
u
r
(
)
l
i
t
c
r
1
t
h
c
p
a
r
i
l
g
o
n
i
l
c
c\l)cl]cc
Q t z ) l c u d i n { l o t h e h i g h e s tA l - c o n t . r t s i n t h c r c n r i l i I ) i n gw h i l e
lo\tkincnrillic
i l r r ls r t r n c t{ \ r g c l c l u l . l 0 0 l ) . i l n d a d r l i t i o n r r l l rb.\ t h e s \ n k i n e - micr. Thc rcsulling s\rkincnrlrlic \ucccssion ol ilssembhges is
n r i r l i cl ) r c \ e n c üo f g l l - | r e li I u r r p h i b o l i l c r .
Q l z + ( ; r 1 - I ) h c+ P s 1 K \ + ( ) r z + C ; r l + P h c + l ' { + Q l z +
S r r ! . r r L r x l . L r dm e l r n r o r I h l e ! \ ( ' L r l j ( ) n
if lh.l-.tr)rrlin! d,rnre jl-l
thc high I'-T siclc of the stirurolilc stitbilit! licld (NIgcl ct ill.
1002).
seleclcd li)r a qulntitlilivc cliscussion.conSanrplc-l N--\.19.
t i l i n s t h e n r i n c l i r l sg . a r n e l .k v a n i l c . ( l u a r t z . l ) h c D g i t e .b i o t i l e .
plagioclasc.rutilc. ilnrenilc. nronazilc. anclzilcon. Thc S2 foli()l hi()tite.
alion is clclinecl bv phengitc arlcl br 4ggrcg11195
A b u n ( l l n 1 p o i k i k r b l a s t i ck l , a n i t e i s a s s o c i l t c d w i t h l ) i o l i l c .
'fhcse
ilg.srcgillesrcplacc phcngilc in garnel rich domlins.
prefercntiallv in shcar lranclsand ptcssurc shadoss ol garncl
( l - - i g I. I ) . C i a r n c l sd i s p l a vs i g m o i d i r li n c l u s i o nt r a i l s o l q u a r t / .
l o u n d a l i c s t h i s i n l e r n N ls c h i s t o s i l l i s d i s c ( ) r d l n l l !
A1 gr-uiIb
cut b\ Sl. Althouglr the sanrple comcs llurl thc C'lilfo arcir
( B o c c h c l t ad e l L i r g o ) l o c a t c ds o u t h o l t h c s i l l i m a n i t cm i n e r i r l
z o n c b o u n d a r v .l h c r o c k c o n l a i n sP l e n t ] ' o l k v a n i t c l ) u l l a c k s
s i l l i n r a n i t c .a c o l r ) r 1 r o n
lcatute in lhis parl ol thc Lcponlinc
F r g . 1 1 . S l k i n . n l . r t i cg r ( t r \ l ho f l o i k i l o H . r s t i ck \ r n i r c r r r d b i o l i l c l l l h . r \ (
s
e
c
T
o
c
k
l
&
E
n
s
i
1
9
9
7
;N l g , c l c t l l . 2 0 0 2 ) . l l o t h r u t i l c a n d i l
p . r n s co i p h c n g i l oa n d g l r n c l d u ri n g l ) 2 . W i d l h o l \ c r l f b l r l s 1 n r n r .
r1'rcniteirre pr-escnlin thc n'riltr-iri*'hile inclusions in kvanilc
a n c l p l a g i o c l a s ci r r c d o m i D r n t h r u t i l c . h c n c e i n l h e n r a l r i \
contirlLr()lrsrulilc breakclown ((;.1 + Rt = Kv + llnr + Qtz)
started. Whilc phcngilc irnd bi()tilc ilrc chcruicall."-horuogeGtt + Phc + Pg a llt 1 Pl. At lhe timc D I dclirrmationccasecl. neous. pllgioclilse sho\\s increäsing('a-conlcnts froDl core 1o
P-'f conclitionsol lpproximltclv 6()0 650 C antl ll l..l kbal
r i m . C ; i l r n c t si n t h i s s a n r p l cc i i s p l a l ' a l s oc l t c n r i c a el v i c l c n c eo l
wcrc reacl'rcd.Sl clearly postdatespcak eclositeflcics P-T c o n s i d c r a l T lree s o r b t i o n .l h i s i s i n d i c a t e db v s l r - o n g l vi n c l c i l s conditionsof 650 ('/ >20 kbar. Thc exactconditionslt thc i n q M n - c o n t c n t s i l D d i n c r e a s i n gF c / ( F e + M g ) - r a t i o sr i g h t a l
o n s c to f I ) l d e l o r n r a t i o nh.o l v e v e rc' .o u l dD o l b e i d c n l i l i e d . thc gr|in bounclirrics(Tal'tlc l). i conrmon leature ()l garnels
Top-N shcarbandshirveevolveddurir'rglatc slagesol l)l de- I r ' o ml h i s a l e ä .
Thc conlplelc equilil)riunr phasc dilglanr calculilted for
formation.
'I'N-l-lt)
(Fig. l2) is similal to thirt calculated fol TN2l2 (Fig.
l0). Thc svnkincnralic asscrlrblallc( irl + Qtz + Phu + Ill + Pl +
SeLondlr:.litnutiut pltas( D2
part
l)2 microstructures
are bestprcservccl
in the southrvestcrn
ol the studyilrea.There.Crl + Qtz + l'hc + Bl + Pl t Ky is thc
stablcassemblage
in metapelitesduring thc dcvelopncnt of
thc 52 foliltion. No paragonitelvaslirund anv morc and plagioclaseappealsirs the onlv Na-bcaringphasc in all pclitic
samples.Howevcr.furthcr north-at Alp Calvalesc.lhc conrplctc paragonitebrcakdown seemste postdatcD2 bccrusc
glowing atlhe cxpcnscol palagostirurolitcanclplagioclase.
nitc and garnet-postdalcthc composilcDli D2 foliationlirund
in that ir.e (Nagelct a|.2002).Biotitc al]dplrgioclasctrc pre()1rock-conrposition.'l
sontregar-dless
he biolilc/phcngitcratio
is higherthan thal lirundin S L Phengilc.thouShrecrvstltllized.
outlines D2 folds in scctionsperpencliculirr
to D2 fold axes.
Plagioclasc
often containsplcnty ol slronglycorrodcd!drnct
lragmcntsas inclusions.
Bi()tilcis c(nntrtonl!alignedin 52. A
svnkinemlticmodlrl increaseo[ biotitc and plagioclascis accompanictlb1'dccompositionof earnct and rvhitc mica.The
Alunriniunr-releasc
throughthis wlrilc nricabr-cakdo$nolten
lcadsro rlregrowthof kvanitcin 52 (e.9.NIs+ (irt = B1+ K] +
to Sl. kylrlile cocxistswith lTiotitcantl plaQtz). In contr-ast
gioclasc( Fig. I I ). Stlurolilc and silliDraDite
posldate52 in this
positionol stausouthweslcrn
area.thoughthc microslructural
'l
rolite in rcspectto 52 is locullyambiguous. hc rclation bc
lNccn ky nitc (=syn-D2)rnd stau.()lilc(=posl D24ros1-k!ani t c ) i n t h c s o u t h c r ns t u d v r c a i n d i c i r l ctsh a t l ) 2 t o o k p l a c co n
.311 I. Nlgtler al.
Kr (liclcl l-3in Fig. l2) lirund in sarrplc TNi-19 is slablc at pres
sures ilrouna l0 kblr ancl lcmpctltures in c\cess o1 650 C .
IrrevioLrs therDrol)alonrclric invcstig.ations vicld conclitions
ar-ouncl650 (' and 5 6 kbar i|l thc Claro ilfcil. i.e. \!illriD thc
s i l l i m a n i t cs t a b i l i t v f i c l d ( ' l i r c l d . t E n g i I 9 9 7 ) . A c c o f d i n g t o
thesei[ltho]-s.thc cquililrnrtiou ol lhc sanrplcspostdillcsthe 52
l o l i a l i o n . H c D c c t h c i [ ] c s u l l sa r e n o l i n c o n l l i c t N i l h o u r P I
cstimillcs lbr Dl. fhe calclllrted nroclal rrrounls ol pheneitc
(Fig. lla). biolile (Fig. l2b). carnct(Fig. l2c) indic lc dcconrdccomposilioD ol'
Ircssion associilledNitll l)l as the obser-\'ecl
gatnet ancl phcngite in asscn'rblagcI-i is illnrost solcl\ pressllre
dcpeiclcnt. Duc to the chcnricll rpl)clll-lrnccol gar-nel.g|metinvolvinq thernronretcrs should Dot bc apPlicd to this samplc
( S p e r r . t P l n i s h 1 9 9 6 )r n d \ \ e a l ) a n d o nd c l c r n r i n a t i o no f P - - l
condilions lvit h l hcfmoblromctry.
We conclude lhat P l coildilions ol rpproxinrirlcl\' 651)
7(X) (- rnd l() kbirr can bc interrccl lirr D2 in the south$estcrn
parl ol lhc slLrclyitfca. Svnkinenraticgro$1h ol biotilc. pliigio'
cl:rsernd k\,anilc a1 the c\pensc ol phentilc ilnd gi|lnct indicatc dcconrplessioD relirlcd 1() I)2 dclornratioD. Sul)sequcnt
growth ol staurolitc and sillimanitc postdirtcs D2. ( onclitions
al the onsel ol l)l det'olDralioDcould not bc detelnrined clilecll\. l)ut th. Dril\imunr prcssurc is linliled b! lhc \\ell-cons l r a i n e ccl n d o l I ) l d c f o l n r a t i o na 1l f o u n c l l f k l r a r i n t h c n o h
ol thc sludv alcl. Howcvcr'. pressules could have bccn higheI
i | l t h \ \ , L r t l l l t l l r c . t l l rl , ) l D : J r ' l o | | D l l i \ ' r .
F-j
li(
al.
)ll-
te.
)llte.
te.
ns.
let
-l/..
u)'
'ca
lal
rks
ine
il
lte
Ii\
t7)
1
!
5
5l
0-
9
640
660
720
680 700
Temperature
I C]
740
1 r ! Lt . \ r ! l l ü r t , L ' i r l l . ll o 1 ) . 1 \ l r f l c h i r r gi n e i r l ( ) ni | l r i l1 o l ( l r i \ . S r n k i n e n r : r t i c
Q l / . 5 i 1 i r s c f . g r r ( ' I n d i c : r l e( l . l ( ' r r n . u i ( nIrn l h c \ i l l i r i r n i l ef i . l d . l ' h ü n g i l . i s r l '
n r r N l f ( ) r n f l . l . l \ d . c L n n t { ) s . r tl o h i , ) l i l . i r r L h i \ \ u n r t ) 1 .( u | ] r e r V r l C ; r o n ( ) ) .
\lillh ol scrlchiU
i\ 5 mm.
)
I t.,
'of
Tltirtl tlclöntutiott plutt
at
ets
lor
'rg.
'l +
(.
640
660
680
700
720
740
720
740
Temperature
I C]
ons
the
ll()
's2
P-'f
lilc
Jnllot
Lü-C
ret
Ple
PT
50
at-n
lio
ldl-
640
660
680
700
Temperature
I C]
D-1
\licrostructulcs llpical lirr D3 are lbund in thc soulhealtcrn
p a r l { ) l t h c s l u d v a r e i l ( c . 9 .i o t h e u p p e r V a l a i r o n o ) w h e l e I ) 3
deli)r'nration is Drosl inlensc lnd associilted rvith the occur'r-encc ol millnratiles in orlhogneisscs. NIajor phases in
D r c l N p e l i t cls1 1 ) n trh i r l i r r e aa r c q u a r t z . b i o t i t e . p h e n e i t e .p l a gioclusc. sillinranite. rrrrclgarncl. Norlh ol the Paina marblc
p h c n g i t e i s s t i l l r r i d c l v p r e s e n l . O n c s a n r p l ec o n t a i n i n g K fclclspar ancl sillirnanitc has l-rccn tbuncl in the uppel Vll
Cilono (Jcker' 2000) lnci litrthcl cxlnrplcs lrc rcporled fronl
-lhompsen
thc litcraturc (Hännr 1972:
1976).Within thc
S o u t h c r nS l c c f B c l t s o u l h o f t h c l ) a i n an r a r b l cp e l i l i c o r s e m i p c l i t i c l n v h n i t c s c o n l D r o n l vs h ( ) w s i l l i n r i i n i t e+ K I c l d s p l
Lrearingasscnrblages(:ca Fumasoli 197-1).Exccpt lirr one srnrplc slaurolilc \\'ils r,)ol li)und iD 1hc malair of r-ocksIron1 lhis
a r c a . K v a n i l c i s s t i l l w i c l c l vp r c s c r v c d .H o w e v c r . i n r o c k s a l fectcd bv intcDsc D3 dclorm:rtion kvanitc almost con)pletel\
r r a n s l i [ m e c l ( ) l i b r o l i l c { F i g . l - i ) . F i b r o l i t ei s c o n r m o n l ! i n r c r g r o w n w i t h q u i r r l zo r - b i o l i t e .r - i l r c l ya l s o w i t h p h e r g i l c . I n s c c
tions oricntdd parallcl to the strctclrin:: lincation and D3 fold
lxis nricasancl cspeciallr quarlr sillimlnilc rods rccrvstallirccl
svnkincnraticallyduring I)-3(Fig. l-3).Thc alunrosilicrtc associalc(l with Dl is kvanite thloughoul the sludv area. Sillimar]iter i c h s a n r p l c su i t h o n l r r r c l k D - l d e l b r t l l a t i o n .e . Sa l l ) i r C r e s sinr. sho\\' conrpletelr slatic cquilibrirlir)r). No significanl
gfowth ol adrlilional phlscs poslditlinq I)3 tlcfo|nralion was
c tll
dl
onIlh
hcr
F r { l l E q u i l i h r i u rf h r \ . r l i r L ! r r . rc\ r l . I l . r L e ldr r r h . r o n t ( \ r r i o n o l , r \ .
e r r i , l t r t r r oilr r h i n s r c l i o I o l\ u p l e I N l . l t ) ( l l l r l ! l ) I h r ' \ | L i | l ! m l l l r r \
! n h l i ' . r . l . l r \ \ h i r ( L e dD. i i r ! n r \ l . 1 r L . l c( | \ I ) l x \ 1 h ( f r o l . r f ! l , u r r ( h n r c1 , 1l l r !
n r l [ ' r n r i n !l l r ] r . r ! l \I , h . r r !r . ( r l b i , , l r r (r h ) r n ( l ! , r r I l . rl . ) l o r r e L n n | ( \ i
1 r , ! lro r D r r l i / r ( lr ( r l l r ( rc . r 1 r ( i n \1.h ! \ e c ( i n l L r u r\rh ( ^ \ r h l h . , ' 1 \ e ' \ e d . \ 1 r l
l n . r ) l 1 i r! r o \ r l r , ' l b l o r j l c i \ r l ü o \ 1 t ) r L r . l \f f e \ \ l | r ! ! l . t . l l r l . I l r \ h i . h i l l ( l j .
ü r \ d e c o m t r r \ ! { n L l u irr r . .rrl r l i n . r i r l i o n
S i r n r p l eI N 1 - 3 6t.l k e n l l o m l h e u p p c r ! a l C r o n o . c l i s p l a r s
rrral lnicr()slrllctur'csdcscribcd ab()vc.
lhc t\pical asscr]]l-tltges
I n c ( ) n t r i r st(( ) o l h e r r o c k s i n t h e i | l e i t t h c s i t n r p l cc o n t i r i n sl l r g c
garnels up l() I cm in sizc although phcngitc is irlnlosl corllp l c l c l ] ,l r a n s l o l n c d 1 o b i o t i t e .C i c n c r a l l ) .n r i n e r a l so l l h i s t h i n s e c t i o ni l r e ( ) n l vw e r k h . z o n e c l( l a b l e r 1 .
\ r r . r r ' , J , , . r . , r ' , " r t ' r' \r .. ' l . I r ' r ,r r '
I f'.rrr".l'r'
lli
tr'f
Peakp.ess!re 140Vlal
D e h y d r a t o nm € r r . q o t w h r e m c a
( P a t r n oD o u c e& H a ( s I 9 9 8 )
D 1 ( n a p p es l a c kn g )
[40 35 l\,1a]
ffi\
m
sl
(l'
D2 (back shearingi
I35 30 N.4al
't
D 3 ( b a c k l od n g ) :
1 3 02 5 M a l
Il
o
i|l
q)
Lt
IL
(2
clt
!^r
til
l9
700
750
Temperature
[C]
Temperature
[C]
F i g . l l . l q u i l i h r i u n r p h r s e d i i r g r r D r c r l c ull. d l i , i r h f c ( n t ) ( \ r r i ( n r o i . t o lr \ e l . ( r . d p r f l r r h i n \ e c r i ( l l ro I \ u r f l c l N l . r 6 ( l r b l c l ) . l ) o r l ! ( 1 l l n . n r l r t \ r h e
\ r e t s o l i d u \o l g rr n i t . \ ( J ( ' h r n n . s& l l ) l r l l t ) 9 6 ) .c h \ h . d l r r . s i n d r c r r c. \ p t r i
D r c n r a l l vL l c l e f r r r i l l c c l wm
e le l t i n go i p h c g j t c ( l ' . r l i n ol ) o u c c . \ l l l ] l i s 1 t ) r ) s ) .
rnlh. le\l xrrl irrlr!(dl' 1
I is. 15.l' 1 tulhsli)rlhelhrccl().rlrti.'LlNcu.'.(l
conrlirr(n\
trs\)crrl.(l$irh r l)rrlicuLr(lelorrrrll,,ll
fht|\. rl rrch locirlil\.
l'r!\\urcsrcllrcrfr('grr\.i\| r\humrtionJuriIs I) I Dl. s hilein.rer\ifgl.nrl()rlhelhrrü
rre rlprfenl lr)Llrcllccllilj.rcrrl\lirlrnglcnrprr,rlrLres
tr.rirlLrrcs
sP
gii
('i
lri
ph
int
nil
(c.
P-T estinratesrelatcd to I)-j clclirlmatiorl can hc dcr i\ e.l accurntelt li)m llre irbunclanlassen]blageCft + Qtz + Bt + Pl +
Phe + Sil (asserlblagc l'1 ol Fig. 1,1)and lrtnr lhe lollowing
licld obsclvatious: p:esencc ol sillinrlnite ancl whitc mica. absence ol st urolile in mclaPclilcs. lind cutcclic Drclting in or'
'l'hcse
'l'coDditions
to 650thogDciss.
conslraints Icsllict the P
7 5 0C a n d - l s k b a r ( F i g . l l ) .
Todd & Engi (1997) cleriveclcondition\ ol > 650 (' antl 5
r crmobarunetr\
k b a r f o r - t h i s a r c a u s i n g n r u l t i - c c l u i l i b l i u Dt h
and wc obtilincd thc samc rcsLrltwith our srnrPlcs. It seems
lhat chen]icll cquilibr.ation look place {uring I)-.1in lhc soullr
eastern sludv irrea-Elseshcrc. it can onlv tre saicllhal lhe thcrmobaronrctric lcsults postdatc D2. It is gcncr-alh stated thllt
the peak ol anlphibolite lacics crYstallizationin thc Leporrlinc
occurud bctwcen D2 and I)3 (A)rton & Rrn)srv 197.1:Gruiic
& Mancktclow 1996).Thc soulhcustcrn p rt ol oul slucly atcl
leproscnts irn cxccption llnrl llris observrlion sitrcc D3 deformation alld cr!stallizalioD is intcnse at a nlicr'oscoficscale irnd
sincc high lcnrperaturc concliliortsstill prerailccl clttt-ingD-l defolnration. l-odd and Engi ( I997) irlso suggcstcdthat chcl]lical
ecluilibration in this spccilic ilrca is younller thirn in the maiot
part ol thc Lcpontine donre l)ccausethev obtirinccllowct Ptcs
sules conrpitrcd to m()l-en(nlhcrlv arcns.
We cr.)ncludclhal thc nrclamolphic conclilions lclated to
Di in lhe s()uthcastcl-npitr-t()l thc studY ilrea irr'cirr()und6-i()
700 C and -l 6 kbar. Equilibtitlier'r of rDincrll coDrpositionis
concurrcnt wilh D3 sincc l lrcrnrobrr omctlic \lLrdiesvicld ide -
3 1 6 l . N a r : eel r a l .
l i c i r l P - l c o n d i t i o n s .I h i s r c c q L r i l i b r i t l i o n
of micr()slruclurcs
ancl nrineral chcrrrislrvcJuringD-i posldlles thc estublishnrcnt
ol pcirk nrctilnrorphic conditions hclu'ccn D2 itncl I).1 as ob
scrvcd in the ccnlfill and notthcfn pillts of thc l-cpoutine
ill r
Li)
ll()
pn
tlonte.
( )r L,rulI cr olrrt irttt o.l t t tL,tuntr
trplt it .qntrlc rl trri ttg tlt' li tru tttt i ott
'I
h c c v o l u t i o no l l h c m e t a n r o r p h i cc o n d i t i o n sd u r i n g t h c l h l o c
dcli)nnalion philscs is sumnrrrizccl irt Fig. 15. Decreilsiog lltessLrrcsIl1d incrcirsinq tenrperalutcs irrc iDdicatcd bt thc thrcc
snrlll portions ol thc P-T loop!. oblaincd (ir D l. I)l irrtl I).1in
lhrcc dificrent slrbitfcas.Note thrt thcsc partial loops. irrd irss ( ) c i a l e dP - l c o r d i l i o n s .n e L c n o l ( ) l r s e f \ c d\ \ i l h i n i r s i r r g l cr ' i
{ i o n o f t h e s t u d , ' i l r c a . M o r e o v c t . p o r t i c r r r os f t h c I ' - l l o o p s
cillcLllatedt'ol (hd l)irrliculal spccinlcns cliscussecl
earlicI incli
c u t c d i f l c l c n t I ' I c l o l u l i o n s f o t l h c s cd i l l e l e n t r c g i o n s( N i l g c l
c l a l . l ( X l 2 ) .C i ) n s c q u c D t l vt h
. e s el ) ' l c s t i n r a t c sc i l n n l ) 1b c c o n l l)incd into a singlc P T l,-rop\alitl lin lhe enlir-eur)Iking urea.
In sIi1e ol this conrnlicalion.thc dall prcsentcclabove inrlicatc
thirt thc prc\\urc clccrcascd clrtlirrg all deli)rnr1llion stirges.
| c c o [ d i n g p r o g r ' c s s i v c } i h u n r i l l i ( ) no l t l l c c n t i r c a l c i r d u r i n g
l ) 1 . D l : r n . lf ) . i . l l r i I r r r r p r ; r t r r [ . l ] , r \ü \ c f . . ' . r n I , ' l l n ü , l i \ , callr be inlerrccl 1(r harc incrersc(l or- dccrcaseclciuring cr
h u m a t i o n r t a n l g i v c n l o c a l i l l . l s t c d . l h e s l ' r i l to l t h c t h r e e
clccompressiooltxrps lorrards hi!.hcr tcmp.ratures (liig. l5) is
i n t e I p r e t e dl o f c s u l t l t o m t h e l a c l t h i l l t h e i n i t i a lc q l o g i l el i r c i c s
Sc
l9
lirl
ill (
sht
()u
Il'tr
cIl
n()
dir
scf
N\\'il
tltc
I'iII
tilll
( l(j
bcl
S,r
l e n r p e r a l L r rheas r c b c c n h i g h c l i n t h e s o u l h ( H e i n r i c h l 9 f i 6 ) .
'lhis
i n t c r ' P l e t l t i o oi s b a s c do n l h c ( ) b s cvl i t l i ( ) nt h r l i n d i v i d u l l l
sltntplcsrecord isothelnllrl dcconrp|cssion flither-lhlrn heirtinl.l
( \ . r g c le l i l l . l 0 0 l ) .
'fimc
conslraints:rn(lconrprrrison ilh thc lcrtonrF
[r01amr)rphic
cvollltion ol surrounding arc{s
.
\\'c nor cliscusslinrc col]slrilirls hr conrplrIin9 lhc slrllclutill
l l n dn r e l i l r r r o r p h ci c\ o l u t i o r l i n t h c \ l u d \ i l l e i t \ \ i 1 h l h i t t o l s r l r r r u n d i n 1| lc g i o n s :( 1 ) t h e r l e c p e iI - o r v c rP c n I ] i n i cn i r l ' r p eosl l l t c
l - ! p o n l i n r d o m c s i l u i l l c ( ll i r r t h c r t ( J t h c \ \ c s l ( c . g . , \ \ ' r - t o n&
R i l n r s i r lv9 7 J l ( j r - o r t l e 1 i r l - 1 9 9 - 5( :; r u i i c ( t M i l n c k l c l o u l 9 9 ( r ) i
( l ) 1 h c n o r l h c f n i r n d c a s t c l n l l l o s pt i r r t so l t h c A c l u l au a p p c .i o cluclingthc 13ergcllpluton (c.s. I.il\\ l9S7: I'lr1/sch lgt)i'l:BerS
c f c l a l . l 9 t ) 6 ) .a n r l ( l ) . t h c n r i c L l l cl ' c n n i n i c ' l a r n b ou n c lS u r - c l ll uufpcs (c.g. Schrcurs lt)9-i:llaurlil] el ill. 199i. ivlirrquercl ul
t99l).
'Ihc
PI
rl)
ras
crll
rbine
Iee
iin
il\
)Ps
dlgcl
rlll-
lllc
ing
a\)is
'ics
c h i l r i r c l c r i s l i cosl l ) i t o I ) . 1 i D t h c s t u d y i r r c u c o r r c r p o n c l r c | r ' $ e l lt ( ) ( l a f o n n u t i o np h r r s c rse f o r l c d l - l r ) ntrh e N l l l g
g i l ll n d l . e b e n d u l rn i l p p c s( ( i r u j i c & \ l a n c k t c l o r 1 9 9 6 ) o r l h c
( i n r a L u r g i l u n i t ( ( i r o n c l c t a l . I ( ) 9 5 )I u i l h c I r v c s l .I ' r o b l c n t s
l l r i s ec o r l c e r n i n gl h c c o r r c l i r t i o n\ \ i l h \ o n r a ( ) l t h e ( l c l i r f m a t i o n
p h a s c sl i r u n c li n t h c r c s t o l A c l u l r rI ] a p p e .u r o u n c ll h c B e l { c l l
i n t r u s i o nl.r n d i n l h e s t n r c t L n i l l l vh i g l r e l l u m b o r n ( l S u r c l l i l
n l l p p e s$ h c f e h c l t r l t h s ( ) l u t e l i n 1 e c o n s l l i t i n l sa | c a v a i l l r l r l c
r r i J i . i r r . . i u rirI \ . l l I ] ] | ( cl r . r l .l ' ) " r . r .
N o r l h w l r c l sa n c lr v i t h i n l h c A d u l i l n u p p c D l o l o u l - s l u d l
lrrir corrcs|oncls in all |csPccts 1() lhe Z:rpport phirsc (Dl in
l . ( i N l 9 f i 7 : D i i n P n r l r s r h l t ) 9 f i ) .r r r i g i n a l l r d c l i n c c l i n t h e
n o f t h c r ni l n d n r i d c l l cA c l u l i rn a p p c . f h c ( ) o s c to l t h c Z a p p ( ) r t
f h r s c ( o u r D l ) l ) o \ t d t c \ p c a k c c l o g i t c c o n c l i t i o n si n t h e
,\dull nu||c a1 rbout J0 l\la (llcckcr I9()i: C;cbiluer lt)96:
S o h n i dc t i r l . 1 9 9 6 ) T
. hc nc\t vounscrLcis Ihase (l)-l of l.iiw
l 9 S 7 :I ) l o l P r r l r s c h l 9 9 f i ) i \ i t s s ( ) c i i t t c\(\li t h D o r t h \ c r s c n l
I t r l c l i n ae n c l l h [ r s l i n g - \ \ h i c h a f l c c l l h e n ( ) r l h c r n p i r r t so l l h c
Aclularrlrppc. l'his phasc is ilbsent in rlr()stl)ilrts ()l ()ur sludl
r r c x ä s i t i \ c o n r p l c t e h d i s s i r n i l a lt o ( h c \ o u t h - c l s t ( l i f e c l c d
o l l h c A ( l r r l l ln a p l ) co \ e r t h c S i n a n o n a p p c . r \ c c o l c l i n t t o o u I
l i n r l i n g ss u c h a l r l c n o r t h w l r ( l d i r c c t c c tl h r u s l i n go l t h c A c l u l a
naltpc durirtl 1hc l-eis plrirsc ntust hirvc locrrllr rcrvolkccl an
o c I n n p p c c o n l i l c l l ) e c a u s ct h e s l i t c k i D go l t h c A ( l u l i l o v c r
S i n r i r n on a p p c i s s v n - D 1 i n o u r r v o l k i n g a t c a ( i . c . s y r r - Z a p p o r l
phrrsc).
As \\c irssocillc thc li)rnration of thc Lower I'cnninic
nlPPc strck rvith I)l (=Zrrpport phasc). rvc conclrLdcthat this
p h i r \ e p r c r l i l t e st h c o n s e t o l l h c l i ) f D a t i o n o f t h e S o u t h e r n
S t c c p l l c l l ( M i l n c s I 9 7 , 1 ) .I h c B e r g c l l b a l h o l i l h . \ \ , h i c hi s d c
lirlnrcrl bl severallargc scalesvnnragnraticlirkls cottcsponding
l ( ) t h r D l l i ) l d so l l h i s s t L r d l .s t a r t c d i l \ a s c c n li n l o a n l r c a d \
c \ i s l i D l ts l c c l )z o n c i r l a l o u n ( l - i 5 M a ( l 3 e r g c rc t a l . 1 9 9 6 .t h c i r
F i g . l 3 : s c e a l s oc l i s c u s s i oinn S t c c k & H u n z i k e l 1 9 9 - 1 ) . ' f h iisn d i c i r l c st h l t s r n - D l n a p p c s t u c k i n gi n o u r r r c a p r c - ( l a l e s- 1 5
l\lir.
I n t h c h i g h c r ' I u m L r o a n t l S u r c t t i l n a p P c st h e s o c r l l c d
N i c n r c l B c \ e r i D p h a s e i s i n l e r c c lt o h a v i D g b e e n i l c t i r c b c lwccn .15 rrrr.l .10)Ma (c.g. Schnricl et ll. lt)t)(ri Weh &
F r o i l z h c i n r1 0 0 1 ) .l l d c f i n i t c l v t c n ) r i n l t e d b c l i r f e l 0 M r . - l ' h i s
i s i d i c a l e d l ) \ t h c o b s e r \ i r l i o nt h I l t h e B c r s e l l g r a n o d i o r i t c
t [ r n c a t c s N i e m c t - l ] c v c l i n s l r u c t u r a s( T u r b i r n o r n r a l l a u l l o l '
N i c | c r s e l t c t r l . l 9 ( ) 6 ) .T h c N i e m c t l l c Y e r i n p h a s e( l o c i r lD 3 )
dirplars intcnse tol) SE shcaling. I)ostdalint top-N nappc
s l i r c k i n gd u f i n g t h c l o c r l D I ( S c l r r c u l s1 9 9 3 :I l i r u d i nc t a l . l 9 9 - l ;
I : c r r l r r p h r s e o l S c h m i d c t a l . l t ) 9 6 ) -O n l h c b a s i s o l t h e s c
k i n c n r a l i cs i n i l a l i l r ( l o p S E c \ t c n s i o n i l ls h c u l i n g ) .u c s u g g c s t
thirt L)2 obscfvecliD oul working lictr cr)rrcspondsto thc:]-5 30
\ l a o l d N i c n r c t B c r c r i n p h a s c .a s c l o e \t h c { e o m e t l i c a l l \ s i m i lat l)2 phlsc obsctlccl in thc deepel lower Penninic nlppcs.
Such ir corfclillion con cspon(lslo 1hc nrodel alrcaclv Ir'oposed
br (ilujic & \lrrrcktclo\\ (1996).
Wc poilrt out thul prc---15
N4anaPPc stacking in thc Surellil
a n d - l r n r b o n a p p c s( l ' e r r c r a p h a s c )n r i r \ . h a v cp r c d a t e dn a p p c
\ t l c k i n g i n l h c L ( ) \ \ c l P c n n i n i c n i r p P e s .s i n c c t h c s c n i d d l c
P c n i i n i c u n i t s u , e r cr r c c r c l e ct lo t h c A u s l r o i t l p i n cu p P e r p l a l c
c u r l i c r ' ( S c h n r i dc t u l . 1 9 9 6 ) .R c c e n t i s o t o p i cs t u d i c ss c e m t ( r
c o n ' i r l h i s c o n c c l ) 1\.\ ' h i l c n r i c a sc l e l i n i n gt h e n r r k r n i t i c S l
shclrring
( l - c r r e l a p h i r s e )l i ) l i l l i o n i r i r s a m P l c l l o m t h c S u r c l l i r D a p p c
o l r s c r r e t ld u r i n ! o u r D l . l h i s i s i r a c c o r ' c l l r n cne' i l l r
o u r o t r s c t v i r l i o nt h i l l D l o \ c f p r i n t b c c o n r c sq c a k c r ' l o s a r c l s ! i c l c l e da n i r g co l J ( r t 5 N l a ( ( ' h a l l a n d c s2 0 0 0 ) .I n c o n l | i r s t .t h c
t h c| o r 1 h \ i 1 h i n t h ü \ o u l h c r n A c l u l i rn a p | e . O n l r a t t h c n o l t h Zirpl)ott fhlsc in 1)urslud\ lü cil nrusl bc consiclerabl\\ ()!Lngcr
(
r
u
r
c r n m o s tr i n r o f
s t u d \ i r r e r s ( ) r r 1 h - \ ' e r g c In)ll l o l c l si l n ( i
iln(l cerlitinly pos( .11)
Ma as cliscusscrlplcviouslv.
n o f t hv c r i l c r r lI - c i s l o l d s l ( ) c i r l l !c r ) e \ i s l .b u l u D l i ) r l u n i l t c l \l ] ( )
Rclial-rlcconstraintson lllc rbsolulc lirlrins of deli)r'nralion
c l i r t c to r c r p r i n t i n l \ t l - u c l l r c \ a n d l h u s f c l a l i ( J n sc o L r l db c o h e \ c D l sä r c i r \ i r i l a b l cl e s 2 i r d i n sl h e D - 3b a c k f o l c l i n p
s h a s c( C r c s '
s e f v c c lI.l l c L e i s l ) h r l s e( ) l l l ) c n 1 ) r ' l h c r A
n r l u l i r n a p p c i n d i c a t c s s i n r p h a s c ) .F o l d s o l l h i s g c n e f a t i o r r l f c c t t h c b a s c o l t h e 3 { )
\-S contplcssion irnd is intcrplctc(l t() bc c(rntenrl)(rrlincoLls N l r r r r l c lg r a n o c l i o l i t co f t h c l l c r g e l l i n t r u s i o n ( v o n l J l a n c k c n '
r u i t hb u c l l o l c l i n gr r r c lb i t c k l l r r L l s l i ni inl t h c s ( ) u l h ent L e p o n t i n c b u f q l 9 9 l : l ) u r i c l s o nc t r l . 1 9 9 6 :I l c r g e I c l i r l . 1 9 9 6 )l ) u 1 i r r c
arca (c.g. Schmiclct al. lt)9(l Prrlrsch lgt)S). hencc conteDrl)o
l f u n c i r l c ( lh v l h c 2 - 1 . {r): 1 . 2l V l uo l c l N o v a l c g r r n i t e ( L i i r l i c t n l .
f u l c o u s$ i t h t h c l ) - l d e l i n c c ll o r o u f \ l u d \ i r r c i l -S u c h a c o r f c l0{){)). I-h!- D-l dclirlrnalioo corrcsPonds l() thc Pcsclticlil
h l r o n i l ] r P l i c st h r l t h e L e i s P h l s e p ( ) s l d r l c \I ) l i n l h c \ o u l h c rr l
u h a s cu r d c f i n c d t r ! I l c f g c r e l r l . ( 1 9 9 6 )
f h l \ e . t h c b r r c k l o l d i l rp
A d u l an a p p c .
li)r lhc llerllcll ilr-ell.
Base(l()n st[rctufal lntl pctIological ()l]scr\ati()nsPrrlrsch
I n t h e s t u c l \l r c | . u n d e l i ) r m c dp c g n r a t i t i c< l v k c sd i r t c c 2
l 5.1
( 1 9 9 Sp) r o p o s e ctlh r r ta d i s l i n c lm ! l o n i l e h o r i r o n a t l h e c o l l t i l c t 10.() l\la ((;cl)iluer Itx)6) inlrudecl 11()r'orll
1()l)--\folcl it\cs iurd
b c t \ \ , c c nt h e n o r l h c f n A d u l a n l p p c a u c l l h c s e c l i l 1 r c l ]ot sl t h c
Ioslclirlc D.-l. l'hc cllccls ol l)ost-25Nla defolnration irrc mioof
S r r j iSt v n c l i n ci \ r e l r l e d t o l - c i sp h l s c n o f t h d i r c c t c d l h r u s t i r t g i n l h e s o r k i r t g a r c a i l l ) i l l l l r ( ) n rl h c F r ) f c o l an ( ) f m l l f i l u l l a t t h c
40 35 Ma
50 km
A d ! r l i l T a n b o n a p p c l T o u n c l a l (r M
' c \ ' r c c l i r l . l 9 9 9 i l ) i r n ( ld c \ l r i r l s h e a r i D ! \t \ i t h i D l h c P a i n r n r i l l h l c n r \ l o n i l e ( l l c i t r n r a n D
l 9 f i 7 ) . H o \ \ e \ c r . h a c k t h r u s t i n g\ \ i t h i n l h c I n s u h r i c n r \ l ( ) n i l e
h r l l ( S c h I n i de l u l . l 9 S 9 ) .r l t h o u g h a s s o c i u l c t\l\ i t h g r c c n s c h i s t
irnd sul)grcenschi\lIaciesconcliliors. is svn Di (see cliscussion
i l ] l l c r g e r e t a l . 1 9 9 6 )u n d h c n c c d i r c c l l \ f c l i l t c d l o s \ n l ) . 1c x
hunriltion. Posl I).1 (lost 25 ivll) dcli)rnrirlion is rcslriclccl 1o
d c \ l r a l s t r - i k cs l i I n r o \ c n l e n t su 1l l r e I n : u b I i c l i n e .
t'lr
sl
t.
in
lo
(l
lir
hl
li
Conclusions
1 0 0k m
3 5-30 Ma
50 km
50 km
F j e . l 6 S k f r c h e . i l l u s l r . t i n { l h r n r i r j ( ) rn r ! . s o i . \ h l r r r r r l i , ) r r l ( ! l h . . \ d u l r
n r t p t ( N ) d i l i . r l : r l l r r S c h m i L I . l x l . l ( ) ( ) 6 ) .S t ! r s i n d i c r l . l h ( t , ) s i l i o n o I l h .
ba!. ol lhe /\(luh nrfp. \ilhii ouf $orkirlg ar.r llr.f !r!h \lct) dL'ringfro
g!üssi!c e\hunrrrion SI: Sinrtlno firt)|(: A: Adulr
unil\ ('lr rbo rnil Surertr lrrtN).
(r) D1 dcl(rr rrl(n) (Zxppoll fhr\c)nnd c\hurrrthn
.rpt).:
Il: Ilrianqon.!is
r1 101(' r: N|r rgo. Dur
()i lhe ,\Juh Drl)tr.
i n g l h e c r r e f i r r d r ) r r i n s t : r g ci J l l h e l r l ) | ( ) (
fhl\c rst.l
\ilhin lhü \uh(hr.li(nr (hrnncl c\hunr(\ lhe \dulr n,,ttr Ir(nn ll lo Il kb
(stipplcil oullin.\ ,)l ,\dula Drfp. ). \()re lhrl r()p S \herr inr rl lh. l,)f ol lhf
' \ d u h n r p t e r r r u s rh r \ c o c c u r r ! d b ( l $ ( e n l h c A d u l N n r l ) | . r n r l l i , r n r . r l o $ ü '
.runrl rn(l rrirnlle urrdcfpinning. ()i lhe Surrtta rnLl Ii[rrbo nrfp.\ (l()f.S
s h e L r r/ o n . I r b ! l l e d l ) . 1 ) u r i n g l h ( . l ( \ i n ! s t ! g ! s o l Z x t ) t r i r 1 I ) h r s . l h e \ . r ' n
d e f p i n n i n g s h f c u n r ! c ( i n r p l . r . l ! s u h d ü ( 1 e r l( - l l l i n l c l c \ r c f \ i { ) n i r l r L l l { ) r h t h o n r e
cording lo l\li(hrrd ct rl. lt)91). Nol. lhirr rhis r)rechrri\llr rc\ull\ if a .ubslrn
r i r l a D r ) u n t ( ) l \ . r l i ( r l \ h o f l . l r i n ! . , \ l l h e s ! n ) c l i n r c l h e I r L r r r h ou n c t S u r r t l . '
uftrr cr u\lrl ll.k.\ \.rr .rrrlh.üd .nt( ) Ih. .\Llul.rnutN (\ti rle(l oullint\ (t
I u n r h o r D r l S u r e l t . n r p p e \ ) . , t r ü l ) r i r r l i r r !t h . I u r
c f l , , t ) - S . h f n r, , o . t i n r h e
r o ( r io l t h . , \ d u l r r r f p e b \ t o l ) - N s h . : r n , r ( l o t - N r h t l l r / { ) f ( l r L h ! l l ! ( t l ) .
( h ) S i r u r l i o n o l l h e g e ( n n c I r !r r r h e e n d e r l e n s i o n l l u n r ! ' l r n g ( i r r n l : l { ) i \
kb) b\ gfr!irirri{ rlcolLrpse (:15 .r0 Nlr i,l(l Nicnrcl ltc\ern phirs.). r\\oc'xt.d
\ \ i 1 h i o t S L \ h u n f i n r f c r r r h c S i n r r n { ) , \ r l u 1 rn a p p c l r ( ) ! ( l i r \ ( o u r D l ) r f ( l
neif lhc brse {)l lh! o'ogcnic lid ( 1!rhir rrn nral lrull ).
( d ) S ; t u r l i ( ) n i r l r r r l h r l h i r d \ t r S . ( ) l . \ h u n ü t i o n ( l 1 1 , r rür l t ) . 1 k b l h \
b . l N . ü n . 1 1r)n ( l l 5 \ l r r ! ( )
crustd h\ l)rckli)lding rDd I'r.kthr lr'lir!
-i lfi L \r,rürfr rr.
cr\i,in.
el
I)cfvasivc aluclilc tlclirr'nalion ir lhc slLlclyarcr bcc(Jnlcsl)rog l c s s i \ ' c l lv o u n g c r l r ' { ) n ln o l h 1 ( )s ( ) u t h .M i c r o s t r t l c t u r i rilr n d
l)ctr'()logicalc!idcncc sho\\'s thlll I)enclfativc s(r'ucluIcs thill
c l c r c l o p c dd u r i n g o u r I ) l ( Z a p p o r ' l ) p h i r s ea r e a s s o c i l l c d\ \ i l h
c l c c o m p r e s s i oL
n r n d c rr c l l t i v d l \ h i g h p r c s s u r c s( l l l l k b a r .
\ c c i i l s o P a r l r s c h l 9 ( ) 8 ) .S h e r r s c o s c s( 1 o p N s h c i l r i s ) i r n d
s t r u c l u r a le \ i c i c d c ci n c l i c | t et h a t t h c Z i r p p o r l p h s c i s l c l l l e d
t o D i r l ) l ) cs t a c k i n g .l l c n c c . c \ h u n r a l i ( ) nb v c ) i l c n s i ( ) n i u
r ln f o o l
ing in thc sensc oi orrr'nralIaulling irncl/oro|er-all cluslal thinn i n g ( g r a r i t a t i o n asl f r c a d i D g ) i sr L l l c c(l) u l l i n t h i s f i r s l r n L l \ c r \
l r s l s l l g e o f e \ h u n l a l i o n o f t h c A d u l u n a p p c t r e t \ e c n - 1 1a) n d
--i5Nla (7 mn/ir. co|r'cspondin1l1() dcconrprcssionb! l{) kbiir
w i l h i n - 5M a ) . S i n c ce r o s i o ni n c o m b i n i r l i o rw i t h l h r u s l i n gc a n rot cxplain thc junlp to lowcr pcak prcssurcsacrossthc (oP ol'
l h c A d u l a n a p p e ( l i | | r h o S u r c l l u n a P p c s )\ \ e c a n o n l \ c n v i s i r g c c \ h u m a t i o n \ \ i t h i n l h c s u b d u c t i o nc h l n n e l b ! u c l i \ c . . c \
l r l l s i o n - o r b u o \ l n l a s c c n to f t h c A d u l a n a p p c u i t h i n t h c s u b (lLrctionch nncl (fcluln ol a ..pi1'r"rrr ..c(mtinentrl shcct acc o r d i n gt o W h e c l c l l 9 9 l . h i s F i g u l c l - 3 1a l s o s e c C h c n r e n ( l icl t
a l . I 9 t ) 5) .
_fhis
inter-plcllrli(ü is in accolclanccwith 1he olrscrration
t h i r t u n c l e r t h r u \ t i n go l t h c A d L r l i ln a P p c \ i l h l h e d { ) \ \ n s o i D e
plirlc prednles Zlplx)rl phrse nrppc \1itcking(scc prc-ZaPport
phascs discusseelbv Lörv l9S7: I)irllzsclr 1998: Nlc\,rc c1 irl.
1 9 9 7 .N l e ! ' r c 1 9 9 ä ) O n s o i n q t o p - N u n d c r t h r u s l i D so l t h c E u l r p c a n f o r c l a n c li n l h c d e e p e r l o w c r P c n n i n i c a n d I l c l v e t i c
n a p p c s ( i . e . S i n r a n o n a p p e ) . a s p l o p o s e d L r v S c h n r i r lc 1 a l .
( 1 9 9 6 ) d u r i n s D I / / - a p p o | . tp h a s e n i r P p cs l a c k i n g l c i r r l sl o i n
c r c \ i n g p r e s s u r c si l n c l l e D l p e t i l l u r c s$ i l h i n t h o s c l o \ \ c t l c c 1()nic units. C on tc nrpotancous clcconrplcssion in lhc AdLllii
nappc is causeclbv lhe clillereolill lsccnt of this nappc within
thc subduction chirnncl. Scr-iousploblcnrcs ilrisc in fcsirrd to
thc lop N shcllirs rlso obserlcd irl the top ol lhc Adula
nll)Pe (Par'lzschI99S: I\,lc\re lt)98: llcuc el ä1.l9t)91)irnd o\\r1
o b s c r v a l i c u s ) -l h c t o p S s h e l l i r 1 ] . o c c c s s a r !t i r r c l i l l c t c n t i a l
asccnl of thc A(lulir napPe in rcspcct lo thc Tambo nirpl)c in its
hllng.ing\\'all.has ncithcl yet hccrr ()bscrveclleirr thc rr)ol ol
thc r\clulao Pl)c l]()rwithin thc Misox zonc. This liscs thc
_l
q u c s t i o n a l t o L l ll h c c x c t n a t L l r e( ) l l h c I ) e v o l u t i ( ) r d u r i n !
thc Zirplor'1 fhir\c t(rl)-N sllcarinil obscrved neilr the lop ol lhe
r\clula nl;rpe. Lacking a r iirble lllcrnrlire modcl lirl crhunrat i ( ) n h v a s c e n l\ \ i 1 h i n l h c s u b d u c l i o nc h a n n c l i n o r c l c r ' 1 oc r '
plain rlccomprcssionduring llre ZitplioIt fhilse wc proposc lhe
I o l k r r v i n gs c c u a l i r ri l l L l s t r ä t e di n l i g u r c l 6 a . T o p - N s h c a l i n g
sLl
ltl
M
l0
ol
si
()l
slr
itl
Ni
tt(
ul1
slr
jac
pir
laf
e\l
(( l
Il i
()l I
cta
a\a
thc
1oI
c\|l
ric
siot
l().
s()c
D3
'I
he
sl a.!
l:iu.
)rg!
lat
nearthe top ol the Adula nappeis only relatedto the closing
stages
o[ Zapport phasedefonnation(top-N shearzone 2 in
Fig.16a)and is associatcd
with latestagenorth directcdthrustingof the Tambo nappe.This latc stagetop-N thrustiDgfollows earlier decompressionassociatedwith top-S shearing
(top-Sshealzone I iD Fig. 16a).and it completelyoverprints
fornrertop-S shcar senseindicators.This carlier stagecom
bincsascentof the Adula nappewithin the subductionzone
withverticalthinningdue to the completesubductionof the
lithosphcric
mantleof the Tambo and Surettanappes("blind
extensional
allochlhon"of Michardet al. 1993).Interestingly,
subslantial
decon]pressioD
duringtop-N to top W Dappcstacklng has also been reportedfrom othcr cclogiticunits (Dora
Maira.e.g. Wheeler 1991:M. Rosa. e.g. Keller & Schmid
Ith
200r).
ar,
nd
ed
StrainintensitvduringD2. conespondingto the 35-30Ma
old Niemet Beverinphase.increases
southwaldand progressivelvoverprintsS1.This D2 is accompanied
by the lbrmation
ol a new axial planar foliation 52, a Iotation of the finite
stretching
lineationfrom a N-S into a NW SE oricntation.and
a reversalof the senseol shearingflom top-N to top SE. This
Niemet-Beverin
phaserepresentsthe oDly stagcof exhumaIion(lioln 12 to 3 kb) which has to bc rclatedto exrensional
unroofingby gravitationalspreadingand/or ologen-oblique
stretch.
We proposethat, between35 and 30 Ma. the areaad
jacentto the SouthemStcep Belt was activeas a south dippitrgfault zone with a normal scnseof shearduring D2. Collapseof the ove hickenednappepile most likoly causedthis
(Fig. 16b).
extension
The synmagmatic
and synmigmatitic
D3 backlbldingphase
(Cressim
phase)is activeduringin the 30 25 Ma time interval.
It is particularlywell developcdin the southeasternmost
part
ofthestudyarca.whereE-W-trending.tight D3 foldsare asso
ciatedwith a stretchinglineationL3. orientedparallelto fold
axes.Further towardsthe N strain intensitydecreases
whilo
lheaxesof major irndminor D3 foldsswingtowardsa NW-SE
to N S oricntation.pre-delermincdby the orientatioDof prcexistingL2 and Ll lineations.BackthrustingwithiDthe Insubric r'Dylonite
bclt (Schmidet al. 1989)couplcdwith rapid ero
sionseemsto be the dolninantcxhumationmechanisur
(Irom 8
to 4 5 kb) duringD3 (Fig. l6c).
Finally.we concludethat.althoughrapid exhumationis associated
with the three major ductilcdeformationphasesD1D3.the locusof pcnctrativedefolmationmigratcdsouthwards.
The mechanismsof exhunrationchangcdduring thesethree
slages
of the exhumationhistory.
nn
ite
ist
on
)xto
rond
in
nd
ecula
hin
Lto
ula
üal
Ll l s
ot
the
ing
the
na
exthe
ing
Acknowledgemenls
W et h r n k M l l 1 h i . r sD a n r o .A n d r e a sF r i s c h b u t t c rO. l i r c r J c k c r .r n d t s e a rN i e d . . h c r g c rr v h op r o v i d € dd a t al r o n r t h c i r d i p l o n l r h e l c sl v h i c hi s p r e s e n r c di n
F i g . l r n d 5 . I n t e n s cd i s c u s s i o nwsi l h N e i l [ , l a D c k t e l o w
ä r c g r a r c l u l l ] -c k D o w ledgcdR
. c\ic$s ol Pctcr lropper. Alerrn.lcr Prorcr. and Kurr Krenr arc
g f c a l l v. r c k n o w l c d g c dI.h i s s t u d ! i s r p r r t o l t h e P h D t h e s i so f T h o r s r c n
N a g c lA
. t t h e s a m et i n 1 ci l i s t h c r e . , u l ot l p r o i e c ts p o n s c r c db y t h c S w i s sN a
'l'his
l i o n a lS c i c n c cF o u n d a t i o n( g r a n t s2 ( 1 . 1 5 2 7 0 . ä
9n
5d 2 0 5 3 6 3 a r . 9 8 ) . n u d y
r o u l d n o l h r v e b c e np o s s i b l c\ t i r h { ) u t h ! l u p p o r t o f t h e l a l e M a r t i l ] F r c v .
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D F C a p rr A N r .C . & B R o w N T
. . H . 1 9 8 7 : T h ec o n r p u t a t i o o
n f c h c m i c a lc q u i l i b r i
u n l i n c o m p l e r s v s l c n r sc o n l a i D i n gn o n i d e a l s o l u t b n s . C c o c h i m . C o s ,
m o c h i m i .A c r a 5 l . 2 6 3 9 2 6 5 2 .
F R r s c r i i r r if rE R .A . 2 0 0 0 :S t r u k t u r g e o l o g i $ c hAcD a l y s ei I n B e r e i c hd c r s ü d l i
c h e n ( ; r c n z T o n c/ w i \ c h e n S i m a n o -u n d A d u l a D e c k e ( s ü d l i c h e sV a l l c
M c s o l c i n ä .G r a u b ü n d e n C
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