1
Time lag be ween me amo phism and c ys alliza ion o ana ec ic
g ani es (Có doba, A gen ina)
F.J. D’E amo1, 2 J.J. Es eban3* M. Dema is1, 2 E. A agón4 J.E. Coniglio1, 2 L.P. Pino i1,2
1Ins i u o de Ciencias de la Tie a, Biodi e sidad y Ambien e (ICBIA) CONICET-UNRC
Ru a Nac. nº 36 km 601, Río Cua o, A gen ina
2Uni e sidad Nacional de Río Cua o, Depa amen o de Geología
Ru a Nac. n° 36 km 601, Río Cua o, A gen ina. D’E amo e-mail: [email p o ec ed]; Dema is e-mail: mdemas is@exa.
un c.edu.a ; Pino i e-mail: [email p o ec ed]; Coniglio e-mail: [email p o ec ed]
3Depa amen o de Geología, Facul ad de Ciencia y Tecnología,
Uni e sidad del País Vasco UPV/EHU
Apa ado 644, 48080 Bilbao, Spain. Es eban e-mail: [email p o ec ed]
4Uni e sidad Nacional de la Pla a, CIG-CONICET
Diagonal 113 64, 1900. La Pla a, A gen ina. A agón e-mail: [email p o ec ed]
*Co esponding au ho
SHRIMP and LA-ICP-MS analyses ca ied ou on zi cons om he Río de los Sauces g ani e e ealed hei
me amo phic and igneous na u e. The me amo phic zi cons yielded an age o 537±4.8 (2σ)Ma ha p obably
p eda es he onse o he ana exis du ing he Pampean o ogeny. By con as , he igneous zi cons yielded a younge
age o 529±6 (2σ)Ma and e lec ed i s c ys alliza ion age. These da a poin o a sho ime lag o ca. 8My be ween
he High Tempe a u e (HT) me amo phic peak and he subsequen c ys alliza ion age o he g ani e. Conco dia age
o 534±3.8 (2σ)Ma, o bo h ypes o zi con popula ions, can be conside ed as he mean age o he Pampean HT
me amo phism in he Sie as de Có doba.
Pampean O ogeny. Pampean Me amo phism. Río de los Sauces g ani e. U-Pb SHRIMP da ing. LA-ICP-MS analyses.
KEYWORDS
ABSTRACT
Ci a ion:
D’E amo, F.J. Es eban, J.J., Dema is, M., A agón, E., Coniglio, J.E., Pino i, L.P., 2020. Time lag be ween
me amo phism and c ys alliza ion o ana ec ic g ani es (Có doba, A gen ina). Geologica Ac a, 18.17, 1-14.
DOI: 10.1344/GeologicaAc a2020.18.17
F.J. D’E amo, J.J. Es eban, M. Dema is, E. A agón, J.E. Coniglio, L.P. Pino i, 2020 CC BY-SA
INTRODUCTION
The Neop o e ozoic o middle Camb ian Pampean
o ogen (Aceñolaza and Toselli, 2009), loca ed a he
no h-cen al pa o A gen ina (Fig. 1), was pa o he
Te a Aus alis o ogen a he wes e n ma gin o Gondwana
(Cawood, 2005). I was de ined as a pai ed bel , wi h calc-
alkaline magma ic ocks in he eas e n bel and medium- o
high-g ade me amo phic ocks wi h pe aluminous g ani es
in he wes e n bel (Rapela e al., 1998; Schwa z e al.,
2008). This calc-alkaline magma ism is widely exposed in
he Sie a No e de Có doba and is usually e e ed o as
he Sie a No e-Amba gas a ba holi h (Iannizzo o e al.,
2013; Li a e al., 1997; Schwa z e al., 2008; Von Gosen
and P ozzi, 2010). The U-Th-Pb da ing in g ani oids om
he Sie a No e-Amba gas a ba holi h ga e c ys alliza ion
ages be ween 530 and 537Ma and we e linked o he
de elopmen o a con inen al magma ic a c in an eas wa d
subduc ion o oceanic li hosphe e down o he wes e n
D’E amo e al.
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
Me amo phism and magma ism ime lag
2
S udied a ea
FIGURE 1. Schema ic geological map o NW A gen ina showing he Sie as Pampeanas geological p o ince, he main moun ain anges, he geological
subdi isions, and he ex en o he Pampean o ogeny ( om Weinbe g e al., 2018). The loca ion o Figu e 2 is shown. Moun ain anges: Sie a de
Aconquija (Ac), Sie a de Fiambala (Fi), Sie a de Amba o (Am), Sie a de Ancas i (An), Sie a de Cachi (Ca), Sie a de Velasco (Ve), Sie a de
Fama ina (Fa), Sie a de Maz-Espinal (SME), Sie a de Valle Fé il (VF), Sie a de Chepes (Ch), Sie a de Ulapes (SU), Sie a de Pie de Palo (PP),
Sie as de Có doba (SC), Sie a de Quilmes (SQ), Sie a No e de Có doba (SNC), Sie a de San Luis (SSL), Sie a de To o Neg o (STN), Sie a de
Umango (Um), Wes e n Sie as Pampeanas (WSP), Eas e n Sie as Pampeanas (ESP).
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
D’E amo e al. Me amo phism and magma ism ime lag
3
ma gin o Gondwana (Casque e al., 2018; Dahlquis e
al., 2016; Iannizzo o e al., 2013; Rapela e al., 1998;
Schwa z and G ome , 2004; Schwa z e al., 2008;
Weinbe g e al., 2018).
The wes e n bel o he Pampean o ogen is o med
mainly o sedimen a y and me asedimen a y ocks
deposi ed du ing Neop o e ozoic imes. These sequences
a e ep esen ed by he low-g ade me amo phosed
u bidi es o he Punco iscana Fo ma ion, and hei highe
me amo phic g ade coun e pa s (schis s, gneisses and
migma i es) loca ed a he Sie as de Ancas i and Có doba
(Aceñolaza and Aceñolaza, 2007; Oma ini, 1999; Rapela
e al., 1998; Rapela e al., 2007; Schwa z and G ome ,
2004; Toselli, 1990; Tu ne , 1960). The e is a lack o
consensus ega ding he ec onic se ing o deposi ion o
he Punco iscana Basin (Casque e al., 2018). This has
been in e p e ed as ei he a 1,000km long passi e ma gin
along he wes e n ma gin o Gondwana (Ježek e al., 1985;
Schwa z and G ome , 2004) o a o e-a c basin (Hause
e al., 2011; Rapela e al., 2007). The onse o subduc ion
u ned hese sequences in o an acc e iona y p ism leading
o medium o high-g ade schis s, gneisses, and migma i es
(Weinbe g e al., 2018 and e e ences he ein).
The Sie as de Có doba a e loca ed a he sou he nmos
pa o he Eas e n Sie as Pampeanas, cen al A gen ina
(Fig. 1). They a e cons i u ed by N-S ending moun ain
anges mos ly composed o Neop o e ozoic o De onian
me asedimen a y and igneous ocks. The main ec ono-
he mal e en egis e ed in he Sie as de Có doba, du ing
he Pampean o ogeny, is he so called M2 (Casque e al.,
2018; Gue eschi and Ma ino, 2014; Rapela e al., 1998).
This e en was linked o an inc ease in he P-T condi ions,
due o c us al sho ening wi h h us s p opaga ing in o
he o e-a c (Weinbe g e al., 2018), leading o an uppe
amphiboli e o g anuli e acies me amo phism and
ana exis. The ana exis ans o med he p o oli hs (gneisses
and schis s) in o me a exi es and dia exi es, wi h associa ed
pe aluminous magma ism. The M2 e en eached
empe a u es abo e 800ºC a mid-c us al p essu es o
8–9kb (Fagiano, 2007; O amendi e al., 2004; Rapela e al.,
1998; Weinbe g e al., 2018). This c us al hickening was
ollowed by adiaba ic decomp ession leading o massi e
c ys alliza ion o co die i e in ocks ha expe ienced
subsequen pa ial mel ing a e he i s onse o ana exis
(Casque e al., 2018; O amendi e al., 2004; Weinbe g
e al., 2018). The iming o hese me amo phic e en s
(c us al hickening and adiaba ic decomp ession) has been
b acke ed be ween 550 and 515Ma, acco ding o U-Pb
SHRIMP da ing in zi cons and monazi es om di e en
gneisses and migma i es o he Sie as de Có doba (Rapela
e al., 1998; Siegesmund e al., 2010; Sims e al., 1998;
Weinbe g e al., 2018), hus concluding ha he Pampean
o ogeny las ed o a leas 35My .
Geological and geoch onological s udies dealing wi h
egional me amo phism (M2) and pe aluminous g ani es
de i ed om he ana ec ic e en s o he Pampean o ogeny,
in he Sie as de Có doba, a e concen a ed in he no h,
mainly in El Pilón complex (Rapela e al., 1998; Rapela e
al., 2002; S ua -Smi h e al., 1999). The HT me amo phism
and he p obably coe al magma ism, we e da ed in
522Ma (Rapela e al., 1998). S udies on o he Pampean
pe aluminous g ani oids gene a ed du ing high-g ade
me amo phism in o he pa s o he Sie as de Có doba,
a e sca ce (Escayola e al., 2007; Tibaldi e al., 2008). The
lack o geoch onological da a limi s ou knowledge on he
age o he me amo phic climax, he ana exis, and hei
empo al ela ionships wi h he syn ec onic g ani es o he
s udied egion.
The empo al ela ionship be ween me amo phism and
g ani e c ys alliza ion di e om o ogen o o ogen (Es eban
e al., 2015; Keay e al., 2001; Vande haeghe e al., 1999;
Whi ney e al., 2003). Al hough he age o each o hese
p ocesses can be ob ained sepa a ely om migma i es
and ana ec ic g ani es, Es eban e al. (2015) demons a ed
ha zi cons ex ac ed om one plu on may be enough o
de ec he ime lag be ween he me amo phic peak and he
magma ic ac i i y in in e nal domains o o ogenic bel s.
They ound a ime span o 7My be ween he me amo phic
climax and he emplacemen o he Lys-Caillaous plu on
in he Axial Zone o he Py enees (sou he n F ance), by
ecognizing wo popula ions o zi cons, one wi h igneous
and he o he one wi h me amo phic a ini ies.
He e, we epo a a he simila case in he Río de los
Sauces g ani e, Sie a de Comechingones (A gen ina),
whe e wo dis inc zi con popula ions iden i ied by LA-
ICP-MS geochemis y and da ed by U-Th-Pb SHRIMP
analyses, allowed us o es ablish he ime lag be ween he
me amo phic climax and he c ys alliza ion o he g ani e.
FIELD RELATIONSHIPS AND PETROGRAPHY
OF THE RÍO DE LOS SAUCES GRANITE
In his wo k, we de ined a new g ani ic body, he Río
de los Sauces g ani e, loca ed wo kilome e s o he no h
o Río de los Sauces illage (Fig. 2A, B). The coun y
ocks a e ga ne - ich gneisses and me a exi e migma i es
o he Calamuchi a Me amo phic complex (O amendi
e al., 2004). These ocks show an ENE–WSW- ending
olia ion (S2) wi h high angle dips (gene ally >70º) bo h
o he sou h and he no h. This olia ion is pa allel o he
axial plane o he igh , isoclinal olds and is associa ed
wi h cons ic ional non-coaxial s ain (Ma ino and
Gue eschi, 2014 and e e ences he ein). The mine al
assemblage o he gneisses is bio i e+plagioclase+qua
z+ga ne , whe eas he me a exi es a e mainly s oma i es
D’E amo e al.
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
Me amo phism and magma ism ime lag
4
ha con ain leucosomes composed o qua z+plagioclase+
K- eldspa ±bio i e±ga ne and melanosomes composed o
bio i e+ga ne +qua z+plagioclase+sillimani e.
The e a e a ew examples o leucosomes o s oma i es
ha o m phacoli hs o pa ches wi hin boudin necks,
e idencing ha mel ing ook place du ing olding. Folded,
laye -pa allel leucosomes also me ge con inuously wi h
leucosomes pa allel o axial-plane olia ion. O amendi e
al. (2004) desc ibed simila s uc u es and in e p e ed hem
in he same way. Magma ans e h ough his old-assis ed
leucosomes ne wo k has been desc ibed in o he pa s o
he wo ld (Weinbe g and Ma k, 2008). Finally, leucosomes
coalesced gi ing ise o leucog ani e and pegma i e shee s,
and small plu ons. Because o he con inuous link om
leucosomes o la ge shee s and plu ons (Fig. 2C), we
in e p e ha leucog ani es a e au och honous g ani es.
The Río de los Sauces g ani e was o med by he
coalescence o nume ous leucog ani e shee s, which in uded
conco dan ly he gneisses, close o he gneiss-me a exi e
bounda y (Fig. 2A, B). The esul ing g ani e body is 1.2km
long and 100–150m wide. The egional me amo phic olia ion
end de lec s a ound he Río de los Sauces g ani e, implying
ha a e solidi ica ion, i also beha ed as a compe en body
du ing con inued de o ma ion. This is a hypidiomo phic
coa se-g ained leucog ani e wi h a mine al associa ion o mi-
c ocline+qua z+plagioclase+bio i e+musco i e+ga ne ±silli-
mani e, and accesso ies such as zi con, i ani e and apa i e. The
modal p opo ion o main mine als is: mic ocline (35-50%)
qua z (35-45%) and plagioclase (20-30%). I also shows la e
pa ches and pegma i e shee s. The Río de los Sauces g ani e is
weakly olia ed. The olia ion is de ined by o ien ed bio i e and
elonga ed qua z (Fig. 2D, E), and is pa allel o he con ac s
and he gneiss s uc u es.
0200 m
87
86 55
73
89
80
72
60
88
76
8
8
5
5
51
89
72
70 67
7
7
0
0
5
5
0
0
8
8
3
3
83
8
8
0
0
8
8
0
0
83
Me a exi es
Gneisses
Leucog ani es
Leucog ani e olia ion
me amo phic olia ion
Qua e na y sedimen s
N
N
RSLG
R
R
o
o
a
a
d
d
64 34 50
32 30 50
2
2
0
0
k
k
m
m
33ºS
65º 64º
32ºS
31ºS
CÓRDOBA
N
Río de los Sauces
Río Cua o
S udied
a ea
SIERRAS DE
CÓRDOBA
6
6
0
0
º
º
W
W
N
N
T
T
I
I
N
N
A
A
E
E
G
G
R
R
A
A
7
7
0
0
º
º
W
W
3
3
5
5
º
º
2
2
5
5
º
º
S
S
A
A
A
A
A
A
5
5
0
0
m
m
D
D
A
A
C
C
E
E
B
B
3 mm
B
B
G
G
FIGURE 2. A) Geological map o he shee - shaped Río de los Sauces Leucog ani e (RSLG). Inse shows i s loca ion in he Sie as de Có doba,
cen al A gen ina. B) C oss-sec ion along p o ile A-A´. C) Field pic u e showing ela ionships be ween leucosomes and plu on. D) RSLG on
ou c op and E) on mic opho og aph, showing he olia ion de ined by o ien ed bio i e. G : ga ne ; B : bio i e.
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
D’E amo e al. Me amo phism and magma ism ime lag
5
U-Th-Pb SHRIMP GEOCHRONOLOGY
One sample om he Río de los Sauces g ani e
(32º30’37.7’’S/64º34’18.8’W) was p ocessed acco ding
o ou ine zi con mine al sepa a ion (c ushing, g inding,
sie ing unde 250 µm, Wil ley able and me hylene iodide)
a he Uni e si y o Río Cua o (A gen ina), in o de o
da e he emplacemen o he plu on. The selec ed zi cons
we e moun ed in epoxy esin oge he wi h he TEMORA 2
e e ence zi con (416.78Ma; Black e al., 2004), sec ioned,
polished and analyzed on a SHRIMP-IIe/MC a he Cen o
de Pesquisas Geoc onologicas o he Uni e si y o São
Paulo (GeoLab-IGc-USP; B azil). The ob ained U-Pb
ion mic op obe da a we e p ocessed wi h he SQUID and
Isoplo /Ex 3.00 (Ludwig, 2003) so wa e p og ams and
a e p esen ed in Table 1. In o de o selec a ge a eas,
ca hodoluminescence (CL) images we e ob ained by a FEI
Quan a 250 Scanning Elec on Mic oscope and XMAX
CL de ec o , in he same labo a o y. Fu he de ails on he
sample p epa a ion, analy ical se up, acquisi ion and da a
p ocessing a e gi en in Sa o e al. (2014).
Acco ding o CL images (Fig. 3) he zi cons e eal a
complex zoned pa e n cha ac e ized by da k luminescen
ims de eloped mainly o e xenomo phic co es, and da k
luminescen idiomo phic zi cons wi h weak oscilla o y
zoning and ex emely low Th/U a ios (<0.02) (Table 1:
spo s 9.1; 3.1; 4.1; 16.1; 11.1; 6.1; 8.1; 1.1; 2.1). These
zi cons con as wi h hose zi cons showing euhed al
mo phology (p isma ic o bipy amidal), concen ic
undis u bed oscilla o y g ow h zoning, some imes wi h
p og essi ely U- ich low luminescen ims, lack o
inhe i ed xenomo phic co es and high Th/U a ios (0.22-
0.57) (Table 1: spo s 1.2; 2.2; 5.1; 12.1; 7.1; 15.1; 14.1;
13.1: 10.1). All hese di e en ea u es poin o wo disc e e
zi con popula ions, ZP1 and ZP2.
Nine and eigh spo analyses we e ca ied ou (Table
1) yielding 206Pb-238U Conco dia ages o 537±4.8 (2σ)
(Fig. 4A) and 529±6 (2σ)Ma (Fig. 4B) o ZP1 and ZP2,
espec i ely. Al hough he Conco dia age o ZP2 displays a
high Mean Squa ed Weigh ed De ia ion (MSWD) and low
p obabili y o conco dance (Fig. 4B), he less disco dance
analyses (<10 %) yield a weigh ed mean age o 530±8
(2σ)Ma. A high p obabili y o age cohe ence in bo h
zi con popula ions is indica ed by he o e lapping o he
conco dan da a as hey de ine a Conco dia 206Pb-238U age
o 534±3.8 (2σ)Ma (Fig. 4C).
TRACE AND RARE EARTH ELEMENT
ANALYSES BY LA-ICP-MS
T ace and Ra e Ea h Elemen s (REE) on bo h zi con
popula ions we e analyzed by LA-Q-ICP-MS (Lase
Abla ion Quad upole Induc i ely Coupled Plasma Mass
Spec ome y) a he Uni e si y o he Basque Coun y
(SGIke ) using a 213nm New Wa e Nd:YAG lase , wi h
a ~3.65J/cm2 ene gy densi y a a epe i ion a e o 10Hz,
coupled o a The mo iCAP Qc quad upole ICP-MS. The
analy ical spo size was 40µm in diame e , and in mos
cases, he zi cons we e comple ely pie ced h ough du ing
he 60 seconds o acquisi ion ime. Ex e nal calib a ion
was pe o med o he NIST SRM 612 (Jochum e al.,
2011). The in e nal s anda d was he s oichiome y-
calcula ed 90Z , and da a educ ion was ca ied ou by he
FIGURE 3. Ca hodoluminescence images o he analyzed zi cons om he Río de los Sauces g ani e. Labels indica e spo numbe s (in bold),
co esponding 206Pb/238U ages and Th/U a ios (in pa en heses).
D’E amo e al.
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
Me amo phism and magma ism ime lag
6
labo a o y s a using Ioli e 3.32 so wa e (Pa on e al.,
2011; Paul e al., 2012).
Six y-eigh zi con c ys als om sample GRS-
215, a e SHRIMP acquisi ion, we e analyzed by
LA-ICP-MS. Some o hem (nine) we e ejec ed due
o he p esence o inclusions o apa i e, ac u es o
composi ional zoning. The selec ed zi con da a a e
p esen ed in Table 2 and 3, acco ding o hei Th/U a io.
This a io, wi h disc epancies (Ha ley e al., 2007), is
used o disc imina e be ween magma ic (Th/U>0.1)
and me amo phic (Th/U<0.1) zi cons (e.g. Hoskin and
Schal egge , 2003). Howe e , examples o me amo phic
zi con o e g ow hs wi h Th/U alues highe han 0.1
(e.g. Ca son e al., 2002; Ha ley e al., 2001; Hokada
and Ha ley, 2004; Hu e al., 2004; Kelly and Ha ley,
2005; K öne e al., 2000; Molle e al., 2003; Pidgeon,
1992; Schal egge e al., 1999; Va a e al., 1999) o
e en igneous zi cons wi h alues lowe han 0.1 ha e
been e e enced (Ladenbe ge e al., 2014; Schä e ,
1984; Sláma e al., 2008; Zeck and Whi ehouse, 1999).
The ex emely low Th/U a io (≈0.01) in zi cons is s ill
conside ed a common disc imina o o me amo phic
zi cons bu he wo k o López-Sánchez e al. (2016),
which desc ibes magma ic zi con o e g ow hs wi h
Th/U a ios (<0.02), ques ions i s alidi y.
In his wo k, he Th/U a io and he obse ed
composi ional zi con zonings can be appa en ly co ela ed
wi h ZP1 (low Th/U a ios om 0.01 o 0.1) and ZP2 (high
Th/U a ios, om 0.1 o 1) (Fig. 5A; Table 1), allowing
o link hem o a me amo phic o an igneous o igin,
espec i ely. Howe e , due o i s ques ionable alidi y,
ano he geochemical pa ame e should be aken in o
accoun o link he zi cons wi h hei o igin.
The Nb and Ta can also be used as disc imina ing
elemen s be ween hese wo zi con popula ions, as ZP2 ha e
almos in a iably highe Nb/Ta a ios han ZP1 (Table 2, 3;
Fig. 5B). When plo ed in he Nb+Ta s. Th+U diag am
1
Table 1.
Spo 206Pbc (%) U (ppm) Th (ppm) Th/U
*
206Pb
238U
Age (Ma)
*
207Pb
206Pb
Age (Ma)
Dis. (%)
*
207Pb*
206Pb*
± (%)
*
206 Pb*
238 U
± (%) e . co .
GRS215-9.1 0,05 530 7 0,01 540 ± 8 533 ± 28 -1 0,05809 1,3 0,0874 1,5 0,8
GRS215-8.1 0,27 319 4 0,01 537 ± 8 521 ± 45 -3 0,05777 2,1 0,0868 1,5 0,6
GRS215-2.1 0,26 481 7 0,01 534 ± 8 534 ± 25 +0 0,05811 1,1 0,0864 1,6 0,8
GRS215-4.1 0,13 535 8 0,02 528 ± 7 519 ± 19 -2 0,05770 0,9 0,0854 1,4 0,9
GRS215-11.1 0,06 535 8 0,02 538 ± 9 512 ± 18 -5 0,05753 0,8 0,0870 1,7 0,9
GRS215-1.1 0,47 460 7 0,02 554 ± 8 553 ± 31 -0 0,05862 1,4 0,0897 1,6 0,7
GRS215-6.1 0,04 684 12 0,02 541 ± 7 532 ± 14 -2 0,05805 0,7 0,0876 1,4 0,9
GRS215-16.1 0,11 598 10 0,02 536 ± 7 550 ± 18 +3 0,05854 0,8 0,0867 1,4 0,9
GRS215-3.1 0,19 593 10 0,02 535 ± 7 546 ± 20 +2 0,05843 0,9 0,0865 1,4 0,8
GRS215-7.1 2,43 359 39 0,11 500 ± 7 515 ± 7 +3 0,05761 3,4 0,0806 1,5 0,4
GRS215-13.1 0,99 245 53 0,22 521 ± 7 660 ± 61 +22 0,06160 2,9 0,0842 1,5 0,5
GRS215-15.1 0,41 238 52 0,22 530 ± 9 580 ± 41 +9 0,05934 1,9 0,0857 1,8 0,7
GRS215-10.1 0,89 212 59 0,28 527 ± 8 614 ± 61 +15 0,06029 2,8 0,0852 1,5 0,5
GRS215-12.1 0,07 178 58 0,33 527 ± 8 639 ± 46 +18 0,06101 2,1 0,0852 1,5 0,6
GRS215-5.1 0,20 196 75 0,38 531 ± 8 585 ± 37 +10 0,05948 1,7 0,0859 1,5 0,7
GRS215-1.2 0,94 62 31 0,50 542 ± 9 550 ± 186 +1 0,05854 8,5 0,0877 1,8 0,2
GRS215-14.1 0,60 247 133 0,54 509 ± 14 481 ± 49 -6 0,05672 2,2 0,0821 2,8 0,8
GRS215-2.2 0,76 73 42 0,57 528 ± 9 512 ± 118 -3 0,05753 5,4 0,0854 1,7 0,3
E o s a e 1-sigma; Pbc and Pb* indica e he common and adiogenic po ions, espec i ely.
E o in S anda d calib a ion was 0.46% (no included in abo e e o s bu equi ed when compa ing da a om di e en moun s).
* Common Pb co ec ed using measu ed 204Pb.
TABLE 1. SHRIMP U-Pb iso opic da a o analyzed zi con popula ions om he Río de Los Sauces G ani e. Da a a e a anged acco ding o Th/U alue
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
D’E amo e al. Me amo phism and magma ism ime lag
7
(Fig. 5C), a clea di e en ia ion can be obse ed be ween
he wo zi con g oups. ZP2 zi cons end o plo owa ds
highe Nb+Ta and lowe Th+U alues compa ed o ZP1.
In gene al, i is assumed ha zi cons wi h a me amo phic
o igin ha e highe U and H and lowe Ce concen a ions
han he igneous ones (e.g. Hoskin and Schal egge , 2003).
Mo eo e , he me amo phically g own zi cons usually
ha e la e HREE (Hea y Ra e Ea h Elemen s) pa e ns,
ela i ely low con en s o HREE (and Y), and MREE
(Middle Ra e Ea h Elemen s), low (Lu/Gd)N, Nb/Ta, Y/Ho
and Ce/Ce* a ios and high Eu/Eu* a ios han he igneous
ones (e.g. Chen e al., 2010).
The chond i e-no malized REE pa e ns (Sun and
McDonough, 1989) o he analyzed zi cons (Fig. 6) a e
s ongly en iched in HREE compa ed o LREE (Ligh
Ra e Ea h Elemen s) and show p ominen anomalies
in Ce (posi i e) and Eu (nega i e). The anges o
no malized REE pa e ns o bo h zi con popula ions
o e lap (Fig. 6), bu di e om no malized ends o
he HREE. The ZP1 zi cons ha e la HREE pa e ns
[(Lu/Gd)N a ios up o 10] whe eas ZP2 shows s eepe
pa e ns [(Lu/Gd) N a ios up o 46]. In he LREE, MREE
o HREE s. Th/U plo s (Fig. 5D-F) he REE con en s
do no show signi ican a ia ions bu inc eases sligh ly
as he Th/U inc eases in ZP2.
In he Th/U s. H plo (Fig. 5G), he H
concen a ion dec eases om ZP1 o ZP2. The U/Ce
s. Th/U o Th plo s can be conside ed as po en ial
indica o s o me amo phic and igneous zi cons since
FIGURE 4. We he ill Conco dia plo s o A) ZP1 (me amo phic low Th/U zi cons), B) ZP2 (igneous high Th/U zi cons) and C) bo h zi cons popula ions
oge he .
D’E amo e al.
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
Me amo phism and magma ism ime lag
8
he magma ic zi cons show li le a ia ion in U/Ce
while he me amo phic ones a e en iched in U due o
inc ease in wa e con en du ing dehyd a ion eac ions
(Cas iñei as e al., 2011). In ou s udy, he analyzed
zi cons a e again spli in o wo main popula ions: ZP2
is cha ac e ized by high Th and li le a ia ion in he U/
Ce con en , and he ZP1 by low Th and highly a iable
U/Ce con en s (Fig. 5H). The applica ion o G imes e
al. (2007) diag ams ag ees wi h zi cons e ol ed om a
con inen al c us (Fig. 7).
Ti-IN-ZIRCON GEOTERMOMETRY
The Ti-in-zi con con en was used o calcula e
he app oxima e c ys alliza ion empe a u es o he
me amo phic and igneous zi cons using he equa ion o
Fe y and Wa son (2007). As he s udied samples a e
sa u a ed in SiO2 (aSiO2= 1), u ile is absen (aTiO2< 1) bu
i ani e is p esen (aTiO2> 0.5), we ha e applied alues
o aSiO2= 1 and aTiO2= 0.5 o calcula e he c ys alliza ion
empe a u es (Table 2; 3). Mean empe a u es o 735±17
and 750±22ºC we e ob ained o he me amo phic
(4.5ppm Ti) and igneous (5.5ppm Ti) zi cons, espec i ely.
The calcula ed empe a u es a e wi hin he unce ain y o
each o he , al hough a sligh inc ease owa ds he igneous
zi cons is p edic ed (Fig. 5I).
DISCUSSION
The zi cons om he Río de los Sauces g ani e yielded
uncommon geochemical signa u es and SHRIMP esul s.
The ollowing esul s s and ou wo old as i) wo zi con
popula ions (ZP1 and ZP2) wi h di e en ex u es and
geochemical signa u es and ii) a bimodal age dis ibu ion
in he geochemical wo end-membe s, 537±4.8 and
529±6Ma, ha e been iden i ied. Acco ding o p esen ed
geochemical ea u es, zi con ex u al analysis and Ti-in-
zi con geo he mome y we p oposed ha he iden i ied ZP1
and ZP2 can be co ela ed wi h me amo phic and igneous
zi cons popula ions espec i ely, and do con i m he u ili y
o he Th/U, U/Ce and Nb/Ta as po en ial a ios o zi con
na u e indica o . These new da a aid in he unde s anding
o he me amo phic e olu ion o he Calamuchi a complex
migma i es and help o cons ain he ime gap be ween he
Pampean HT me amo phism and he c ys alliza ion o
ana ec ic g ani es.
Mel ing p oduc s o ming leucosomes in migma i es
a e commonly ela ed o he o ma ion o shee s like
bodies o leucog ani es and la ge accumula ions o
magma ic ocks along he Sie a de Comechingones as
leucosomes a e ex u ally and composi ionally simila o
he leucog ani ic bodies (Ba zola e al., 2019). The Río
de los Sauces g ani e is a shee ed in usion emplaced in o
Sample
GRS_215
Sou ce ile
59
36
64
24
50
11
43
55
34
62
30
57
14
28
67
12
10
8
66
21
51
20
P
742
698
1060
1096
836
909
1004
785
716
1016
813
1113
921
1097
927
1041
1568
760
707
923
681
679
Sc
380
389
511
519
430
455
455
412
430
484
453
510
446
491
446
477
740
433
372
458
380
418
Ti
3.6
4.3
3.6
4.3
3.9
4.1
3.8
3.8
4.4
3.7
4.4
4.2
4.2
6.3
3.9
4.7
6.0
4.8
4.0
5.0
3.7
4.4
V
8.3
3.1
0.5
0.5
3.2
0.2
0.4
1.1
7.9
< dl
1.4
1.2
1.9
11.7
3.4
5.7
27.5
3.3
2.2
7.2
< dl
2.4
Mn
4.3
3.2
0.4
2.9
3.3
< dl
0.5
2.8
33.0
0.5
39.0
1.6
0.9
16.7
1.8
2.3
26.7
21.3
2.8
4.2
< dl
5.3
Fe
44.0
250
< dl
23.0
31.2
5.5
< dl
14.0
520
< dl
39.1
47.0
6.6
1120
22.0
30.0
515
374.0
250
107
4.8
11.0
Ga
< dl
0.27
< dl
0.22
< dl
< dl
< dl
< dl
0.56
< dl
0.34
< dl
< dl
0.54
0.17
0.32
1.46
0.59
0.44
0.40
< dl
0.18
S
0.90
1.20
0.21
1.65
1.14
0.22
0.25
1.13
2.02
0.25
1.89
0.87
0.57
2.29
0.79
1.32
7.62
1.41
0.81
2.04
< dl
0.77
Y
859
849
1405
1465
1146
1247
1430
1059
923
1421
1020
1633
1264
1475
1237
1378
1941
961
801
1220
917
1123
Nb
1.4
1.6
2.2
2.1
1.9
2.4
2.5
1.7
1.7
2.2
1.9
2.3
2.6
2.6
1.9
2.7
2.9
2.0
1.4
2.2
1.9
1.8
Sn
0.6
0.5
0.5
0.7
0.6
0.6
0.6
0.5
0.5
0.6
0.5
0.7
0.7
0.8
0.5
0.7
1.1
0.7
0.7
0.7
0.5
0.6
Ba
3.7
2.2
0.1
1.7
3.4
< dl
0.2
1.6
6.0
0.3
6.3
2.1
1.0
8.3
2.4
3.2
21.8
8.1
2.6
5.5
< dl
2.0
La
1.3
0.8
0.1
0.9
1.6
< dl
0.1
0.7
1.3
0.2
1.5
1.0
0.6
2.1
1.1
1.8
8.0
1.0
0.9
1.9
< dl
0.8
Ce
10.7
6.1
0.7
8.2
7.3
0.9
1.5
4.4
7.5
1.9
14.1
8.2
4.3
14.6
7.2
11.7
41.7
6.1
7.8
14.4
3.2
7.8
P
1.0
1.2
0.1
1.5
1.0
< dl
0.1
0.7
1.4
0.2
3.2
1.2
0.7
2.4
1.1
1.5
6.1
1.1
1.2
2.5
< dl
0.9
Nd
5.1
7.8
0.9
10.8
5.8
0.9
1.3
4.5
8.0
1.9
22.9
7.3
4.4
14.1
6.0
9.1
32.4
6.6
6.0
15.9
1.0
5.5
Sm
4.1
5.7
4.6
10.3
5.4
4.5
4.9
4.7
5.6
5.2
20.2
8.4
5.7
10.1
6.2
7.9
18.5
4.9
5.7
12.6
3.7
5.8
Eu
1.6
2.0
0.4
2.4
1.7
0.4
0.5
1.6
2.1
0.5
4.3
2.6
1.4
4.0
1.7
3.2
8.0
1.6
1.3
3.7
0.4
2.0
Gd
25.9
23.5
43.9
51.3
35.8
38.4
43.9
30.9
26.8
44.9
50.3
54.4
40.4
49.8
39.5
44.6
57.8
26.0
26.4
44.3
27.9
32.6
Tb
11.3
10.7
19.9
20.7
15.8
17.7
20.0
13.8
12.1
20.2
16.9
23.7
18.9
20.8
16.9
20.3
24.6
11.6
11.0
17.4
11.6
13.3
Dy
123
116
213
220
172
191
222
151
137
213
162
251
199
224
180
211
290
139
120
180
122
147
Ho
29
29
49
51
40
44
49
37
33
48
36
59
45
52
42
48
74
33
27
42
30
38
E
88
94
144
156
122
131
147
117
110
144
107
179
137
162
131
147
265
110
83
130
95
135
Tm
15
17
25
27
21
23
25
22
22
25
18
31
24
28
23
26
53
20
15
23
17
25
Yb
119
133
190
195
162
175
183
186
179
193
139
239
189
210
175
203
462
157
108
175
132
196
Lu
18
20
31
32
27
26
29
29
26
31
22
37
27
34
28
29
71
24
18
27
20
31
H
12130
13130
11820
11740
12120
11310
11590
11850
12290
11550
12680
11700
11970
11740
12040
11700
12520
12620
12700
12090
11520
12070
Ta
1.4
1.5
1.8
1.8
1.9
2.1
2.0
1.9
1.6
2.0
1.6
2.2
2.2
2.1
1.8
2.4
3.3
1.7
1.3
1.9
1.5
1.4
Pb
238
234
275
296
244
318
374
244
211
285
270
318
342
321
248
359
297
231
204
271
213
176
Th
8.5
9.0
11.7
12.1
11.1
14.7
16.6
11.0
11.1
12.9
11.1
15.8
18.4
17.2
13.2
21.8
22.3
17.5
16.9
37.8
34.4
31.1
U
571
537
655
681
615
782
880
572
576
650
541
766
870
772
589
905
877
588
459
686
493
425
REE
453
467
722
785
618
652
728
603
571
729
618
903
697
826
660
764
1412
541
430
689
464
641
Th/U
-
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.04
0.06
0.07
0.07
Nb/Ta
1.0
1.1
1.2
1.2
1.0
1.1
1.2
0.9
1.1
1.1
1.1
1.0
1.2
1.3
1.1
1.1
0.9
1.2
1.1
1.1
1.3
1.3
T (ºC)
715
731
716
731
724
727
720
721
733
719
735
729
729
768
723
741
762
741
725
745
719
735
TABLE 2. Lase abla ion ace, REE, and calcula ed empe a u e da a o analyzed me amo phic zi cons (ZP1) om Río de los Sauces. In ppm. <dl:
unde de ec ion limi
Geologica Ac a, 18.17, 1-14 (2020)
DOI: 10.1344/GeologicaAc a2020.18.17
D’E amo e al. Me amo phism and magma ism ime lag
9
gneisses ela ed o ana ec ic mel du ing he migma iza ion
and can be conside ed as a syn- o he la e-M2 body. In
his ega d, he age o 529±6Ma ob ained om high
Th/U (ZP2) zi cons is in e p e ed as he c ys alliza ion
age o he Río de los Sauces g ani e, and he e o e i
da es he anishing s ages o M2. Meanwhile, he age o
537±5Ma, ob ained om low Th/U (ZP1) me amo phic
zi cons, could ep esen he age o he Pampean HT
me amo phism p io o he ana exis. This me amo phic
e en migh be he o igin o he solid-s a e g ow h o
me amo phic zi cons, which we e u he inco po a ed
in he mel s wi hou dissol ing un il newly c ys alliza ion
o igneous ones a he age o 529±6Ma. This age ag ees
well wi h he p e iously published ages o he Pampean
me amo phism in o he pa s o he Sie as de Có doba
(Gue eschi and Ma ino, 2014; and e e ences he ein).
Al hough he empo al ela ionship be ween he
me amo phism and he ana exis di e om o ogen
o o ogen, ime gaps o less han 10My be ween he
syn ec onic g ani es and egional me amo phism ha e
been epo ed in o he o ogenic domains. Fo example, in
he island o Naxos (G eece), a ime lag o a leas 5My
be ween he peak o he Miocene me amo phism and he
main pe iod o magma ism was epo ed by Keay e al.
(2001). While, a ime span o 7My , has been es ablished
by Es eban e al. (2015) be ween he me amo phic
climax o he HT/LP Va iscan me amo phism (La e
Ca boni e ous) and he inal emplacemen o he Lys-
Caillouas plu on (La e Ca boni e ous–Ea ly Pe mian)
a middle c us al le els. The la e geoch onological
s udy p esen s many simila i ies wi h ou s udy because
in bo h cases zi cons om only one g ani e body ha e
been su icien o de ec he ime gap be ween he wo
p ocesses.
The p esence o zi cons wi h me amo phic
a ini y in he Río de los Sauces g ani e sugges s he
incomple e assimila ion o he zi cons de i ed om
he me amo phic p o oli hs and opens an oppo uni y
o s udy he iming o he me amo phism p io o he
emplacemen o he plu on. The mean empe a u es
o 735±17 and 750±22ºC de e mined by Ti-in-zi con
in me amo phic and igneous zi cons, espec i ely, a e,
al hough sligh ly lowe , cohe en o he calcula ed
me amo phic condi ions in he Sie as de Có doba
(Fagiano, 2007; O amendi e al., 2004; Rapela e
al., 1998). Since he c ys alliza ion empe a u es
calcula ed o igneous and me amo phic zi cons a e
wi hin he unce ain y o each o he , a u he inc ease
in he egional empe a u e du ing ana exis canno be
in e ed. Finally, he age o he climax o he Pampean
me amo phism has been cons ained be ween 537
and 529Ma, and he Conco dia age o 534±4 (2σ)Ma,
Sample
GRS_215
Sou ce ile
32
29
25
60
68
63
17
52
40
56
6
37
46
35
49
61
31
58
23
48
9
19
P
1174
1510
612
642
866
1390
469
830
822
920
396
342
980
402
1070
490
630
958
772
920
875
434
Sc
508
576
392.1
382
423
473
366
519
387
419
362.5
328.1
393
337.6
423
358
386.5
404
406
382.5
432
356.6
Ti
4.8
6.6
3.9
4.5
4.8
5.7
4.6
4.6
5.1
4.2
4.8
4.0
4.5
4.4
5.0
4.3
5.1
6.0
5.3
5.0
5.4
6.4
V
24.3
37.4
< dl
14.4
4.8
58.0
2.1
11.5
15.2
8.3
0.9
< dl
6.2
< dl
11.0
0.5
1.4
3.3
3.6
3.3
10.4
< dl
Mn
49.0
27.1
< dl
4.9
2.3
17.6
1.8
8.6
3.6
6.1
0.7
< dl
2.7
< dl
7.2
2.7
1.5
3.8
5.4
15.9
3.8
4.2
Fe
84.4
269.0
< dl
376.0
23.5
200.0
38.0
660.0
65.0
48.0
52.0
< dl
22.9
< dl
391.0
129.0
20.9
28.4
73.0
940.0
173.0
126.0
Ga
0.60
1.76
< dl
0.36
0.34
0.85
0.32
0.62
0.36
0.44
0.28
< dl
< dl
< dl
0.75
0.60
0.35
0.45
0.55
0.69
0.73
0.53
S
2.64
8.20
0.22
1.90
1.81
6.10
0.86
2.50
1.74
1.65
0.51
0.16
0.83
0.12
3.27
0.38
0.34
1.99
1.76
0.51
1.45
0.97
Y
1402
1960
906
860
1286
2223
697
1200
1141
1337
523
493
1820
489.5
1690
637
1043
1377
1190
1510
1650
544
Nb
2.9
2.7
2.7
2.8
3.1
3.5
2.1
2.4
2.3
2.8
2.1
2.0
2.5
2.0
2.5
1.8
2.3
2.0
2.5
1.9
3.3
2.0
Sn
0.8
0.9
0.7
< dl
0.8
1.0
0.8
1.0
0.5
0.7
0.7
0.5
0.4
0.5
0.7
0.7
0.7
0.7
0.8
0.4
0.5
0.8
Ba
11.7
32.7
< dl
6.7
6.3
23.3
2.7
7.2
7.4
5.9
1.1
< dl
2.2
< dl
11.4
0.8
1.4
5.7
17.0
0.6
6.0
0.4
La
5.3
14.3
< dl
3.0
2.5
13.8
0.8
4.0
4.6
3.8
0.4
< dl
1.6
< dl
5.2
0.1
0.4
2.7
1.4
0.3
4.1
< dl
Ce
20.6
88.0
6.2
23.0
25.5
47.2
15.7
29.0
25.0
29.7
11.8
10.1
12.7
8.8
40.0
11.2
11.9
23.1
18.6
9.8
27.6
12.0
P
2.8
12.4
0.1
2.0
2.8
6.5
1.1
3.0
2.6
2.9
0.6
0.1
1.1
0.1
4.2
0.2
0.6
2.7
1.6
0.4
2.5
0.2
Nd
16.6
67.0
1.4
10.8
17.6
36.8
7.2
19.1
15.9
16.6
5.4
1.7
10.5
1.6
22.7
3.0
7.0
18.0
12.3
5.9
14.7
5.0
Sm
12.5
33.2
4.9
8.8
13.8
26.2
7.7
18.6
10.8
13.4
6.2
4.8
14.2
4.4
19.6
6.2
13.1
17.0
13.3
11.6
14.8
12.5
Eu
6.1
16.2
0.7
4.8
4.8
9.3
2.2
6.0
5.6
4.9
1.4
0.7
3.5
0.6
6.5
1.4
2.2
5.4
3.7
2.0
5.2
1.7
Gd
48.3
78.0
29.2
33.9
52.1
93.5
30.7
66.4
41.3
52.4
25.7
24.9
68.0
23.8
74.7
28.1
57.2
62.2
47.7
55.9
58.0
48.9
Tb
16.0
26.2
9.5
10.3
15.7
27.7
9.3
18.6
12.5
16.0
7.6
7.2
21.0
7.0
20.7
7.9
15.6
17.8
13.5
16.6
17.7
12.0
Dy
175
284
106
110
163
287
90
180
142
169
73
69
237
65
218
79
144
183
145
184
204
93
Ho
51
74
31
29
45
81
23
44
44
52
18
17
71
17
64
23
36
53
44
56
64
19
E
204
256
121
100
171
314
82
145
176
203
59
51
263
57
255
87
121
193
173
223
267
51
Tm
42
48
24
18
32
64
15
25
36
41
10
8
49
10
51
18
20
35
33
43
53
7
Yb
361
376
186
144
242
519
112
192
297
339
73
60
365
74
417
150
149
272
266
342
445
51
Lu
55
55
31
22
40
81
17
25
48
54
10
8
62
11
69
27
22
43
46
59
73
7
H
12620
12410
12140
12260
11590
11680
11370
10870
10680
11960
11520
11430
11630
11110
10210
11170
10490
10010
10060
9820
10780
11400
Ta
1.8
1.7
1.8
1.9
1.9
2.3
1.3
1.3
1.5
1.8
1.3
1.3
2.0
1.2
3.2
1.1
1.2
1.0
1.3
1.1
1.7
1.0
Pb
215
275
146
150
144
216
95
143
82
138
79
88
165
75
106
62
90
56
63
73
119
57
Th
80
166
64
87
95
166
83
148
69
117
71
82
154
71
154
72
109
77
87
95
192
82
U
489
920
336
354
367
624
243
433
199
331
198
210
392
163
339
149
214
148
165
160
320
136
REE
1017
1429
551
520
827
1606
413
775
862
998
302
262
1179
281
1268
442
600
927
818
1010
1251
320
Th/U
0.16
0.18
0.19
0.25
0.26
0.27
0.34
0.34
0.35
0.35
0.36
0.39
0.39
0.44
0.45
0.48
0.51
0.52
0.53
0.59
0.60
0.60
Nb/Ta
1.60
1.57
1.50
1.48
1.64
1.52
1.59
1.85
1.48
1.56
1.64
1.51
1.26
1.65
0.78
1.61
1.92
2.03
1.93
1.65
1.89
2.05
T (ºC)
742
773
724
736
742
758
739
737
748
731
742
726
735
734
745
732
747
762
752
746
752
770
TABLE 3. Lase abla ion ace, REE and calcula ed empe a u e da a o analyzed igneous zi cons (ZP2) om Río de los Sauces. In ppm. <dl: unde
de ec ion limi
