2006 adakite

Serviço Geológico
do Brasil – CPRM
Paleoproterozoic accre-onary and collisional processes and the built-­‐up of the Borborema P r o v i n c e ( N E B r a z i l ) : g e o c h r o n o l o g i c a l a n d geochemical evidence from the Central Domain Geysson A.Lages Sérgio P.Neves Roberta G.Brasilino Alan W.A. Miranda Geological Setting
Geologic Map
Petrography
Group I
q  non-­‐migma))c; q  dominantly augen gneiss q  syeno to monzo grani)c composi)on q  Previous U-­‐Pb: 2137±21 Ma (Rodrigues et al., 2010); 2.3-­‐1.95 Ga (Santos et al., 2013) Group II
q  migma)zed amphibole-­‐bio)te bearing; q  grani)c composi)on q  syeno to monzo grani)c composi)on q  magne)te bearing pinkish leucossomes q parallel to truncate leucossomes Group II
q  amphiboli)c layers or rounded metagabbroic enclaves
q  three dis)nct chemical paMerns q  Previous U-­‐Pb: 2016±27 Ma (Santos et al., 2004)
Group III
q  Banded gneisses q  diori)c dominant composi)on q  fine-­‐grained leucossomes and metamafic rocks intercalated q  Previous U-­‐Pb: 1970±30 Ma (Sá et al., 2002); 2127±7 and 2044±5 (M1) Ma, 2103±11 Ma (Neves et al., 2006); 2110±7 Ma and 2096±7 Ma (Brito Neves et al., 2013) Group IV
q  equigranular felsic gneiss q  grani)c composi)on q  absence of amphiboles q  Previous U-­‐Pb: 1991±5 Ma (Neves et al., 2006); 2110±7 Ma and 2096±7 Ma (Brito Neves et al., 2013) U-Pb and Sm-Nd results
Group I
data-point error ellipses are 2
2084 +/- 11 Ma
0,46
0,42
50
a
2M
2300
m
2100
Pb/
238
U
0,38
206
São Joãozinho orthogneiss U-­‐Pb 2109 ± 15 Ma MSWD = 0.66 n = 20 Sm-­‐Nd TDM 3.03 Ga εNd(t) -­‐ 9.04 2
2112 +/- 17 Ma
1
+/0 91
1900
0,34
1700
0,30
Intercepts at
608 +110/-120 Ma & 2109 +17/ -15 Ma
MSWD = 0.66
0,26
0,22
3,5
4,5
5,5
6,5
207 Pb/ 235 U
7,5
8,5
Group II
data-point error ellipses are 2
0,42
2180
0,40
2140
206Pb/238U
Salgadinho migma--c orthogneiss U-­‐Pb 2057 ± 20 Ma MSWD = 2.4 n = 19 Sm-­‐Nd TDM 2.62 – 2.65 Ga εNd(t) <-­‐ 6.0 2100
0,38
2060
2020
1980
0,36
Intercepts at
496±670 & 2057±20 Ma
MSWD = 2.4
0,34
5,8
6,2
6,6
207Pb/235U
7,0
7,4
Group II
data-point error ellipses are 2
2003 +/- 10 Ma
/17
M
a
0M
Pb/
1900
20
75
+
2
20
0,32
/- 1
1+
238
U
0,36
200
0,28
m
1700
1500
206
Cabaceiras migma--c orthogneiss U-­‐Pb 2055 ± 23 Ma MSWD = 2.3 n = 21 Sm-­‐Nd TDM 2.74 Ga (2.74-­‐3.28) εNd(t) -­‐ 8.08 (-­‐2.35 to -­‐11.72) 2100
a
0,40
0,24
1300
0,20
1100
Intercepts at
590+ 100& 2055+23 [- 24] Ma
MSWD = 2.3
900
0,16
0,12
1
3
5
207
Pb/ U
235
7
0,42
RS-423
0,40
2140
2060
2020
206
Group II
Pb/238U
2100
0,38
1980
0,36
1940
Intercepts at
Upper = 2042+11Ma
Lower = 0+ 50Ma
MSWD = 0.68
0,34
0,32
0,56
0,64
0,60
207
0,40
0,38
0,72
0,68
Pb/235U
RS-423
small zircons
n=5
2100
2060
2020
1980
Pb/238U
0,36
1940
1900
0,34
1860
206
Cabaceiras orthoamphibolites U-­‐Pb 2042 ± 11 Ma MSWD = 0.68 n = 6 big zircons Th/U > 0.01 1996 ± 13 Ma MSWD = 0.75 n = 5 small zircons Th/U < 0.01 1820
1780
0,32
1740
Intercepts at
Upper = 1996+13Ma
Lower = 0+ 50Ma
MSWD = 0.75
0,30
0,28
0,26
4,4
4,8
5,6
5,2
207
235
Pb/ U
6,0
6,4
6,0
Group II
data-point error ellipses are 2
2181 +/- 11 Ma
Other migma--c orthogneiss U-­‐Pb 2183 ± 9 Ma MSWD = 0.55 n = 21 Z08# 612 ± 12 Ma 50
m
Intercepts at
604 +20/-19 Ma & 2183.3 +8.7/ -10 Ma
MSWD = 0.55
Group III
0,44
2200
0,40
206Pb/238U
(Vertentes/Floresta) Vertentes migma--c orthogneiss U-­‐Pb Cluster I: 2096 ± 23 Ma n = 5 {Cluster II: 2044 ± 23 Ma; Z24 # 2048±22 Ma Th/U<0.01 Metamorphic1?/minimun age {Cluster III: 1986 ± 38 Ma Th/U<0.01 Metamorphic2?/ Sm-­‐Nd TDM 2.13-­‐2.63 Ga εNd(t) 2.37 to -­‐5.66) data-point error ellipses are 2
2100
Intercept at
1986±38 Ma
MSWD = 1.4
0,36
2000
Intercept at
2044±27 Ma
MSWD = 15
1900
0,32
1800
0,28
4,5
5,5
6,5
7,5
8,5
207Pb/235U
point error ellipses are
Group IV
0,5
2200
0,4
206Pb/238U
Felsic grani-c gneiss U-­‐Pb (euhedral zircons) 1981 ± 23 Ma n = 5 (regression of all data) 1930 ± 49 Ma (MSWD = 11.8) metamorphic/magma)c event overprinted data-point error ellipses are 2
1800
Intercepts at
449±270 & 1930±49 Ma
0,3
1400
0,2
1000
0,1
1
3
5
207Pb/235U
7
9
Nd curve evolution
15
5
-5
2.05 Ga
-15
-25
-35
DePaolo
Cabaceiras Complex
São Joãozinho Orthogneiss
Vertentes/Floresta Complex
Salgadinho Complex
-45
0
0.5
1
1.5
2
2.5
3
3.5
7
7
Geochemistry
Peccerillo and Taylor (1976)
6
Metaluminous
Peraluminous
5
5
6
Shand (1943)
A/NK
3
3
K2O
4
High-K calc-alkaline
Series
4
Shoshonite Series
2
1
1
2
Calc-alkaline
Series
Peralkaline
0
0
Tholeiite Series
45
50
55
60
65
70
75
0.6
SiO
2
1.0
A/CNK
F
Tholeiite Series
Calc-alkaline Series
Irvine & Baragar (1971)
A
0.8
M
1.2
1.4
1000
Sample/ REE chondrite
1
10
100
1000
100
10
Sample/ Primitive Mantle
1
Cs
Ba
U
Th
K
Nb
Ce
La
Pr
Pb
P
Sr
Zr
Nd
Dy
Eu
Sm
Ti
Yb
Y
La
Pr
Ce
Lu
Pm
Nd
Eu
Sm
Tb
Gd
Ho
Dy
Tm
Er
Lu
Yb
1000
1000
Rb
Cabaceiras Complex
0.1
0.1
Cabaceiras Complex
U
K
Nb
Ce
La
Pr
Pb
P
Sr
Zr
Nd
Dy
Eu
Sm
Ti
10
100
Yb
Y
La
Pr
Ce
Lu
Pm
Nd
Eu
Sm
Tb
Gd
Tm
Lu
Er
Yb
100
1000
S a m p le / R E E c h o n d r ite
100
1
10
1
Salgadinho Complex
Cs
Ba
Rb
U
Th
K
Nb
Ce
La
Pr
Pb
P
Sr
Zr
Nd
Dy
Eu
Sm
Ti
Mcdonough and Sun (1995) Salgadinho Complex
Yb
Y
0.1
0.1
Ho
Dy
1000
Th
0.1
Ba
10
0.1
Cs
Rb
Sample/ Primitive Mantle
SU-515
1
Sample/ REE chondrite
10
SU-515
1
Sample/ Primitive Mantle
100
RS-234;RS-424
RS-234;RS-424
Lu
La
Pr
Ce
Pm
Nd
Eu
Sm
Tb
Gd
Ho
Dy
Boynton (1984) Tm
Er
Lu
Yb
1000
Sample/ REE chondrite
1
10
100
1000
100
10
Sample/ Primitive Mantle
1
São Joãozinho Orthogneiss
Ba
U
Th
K
Nb
Ce
La
Pr
Pb
P
Sr
Zr
Nd
Dy
Eu
Sm
Ti
Yb
Y
Pr
Ce
Pm
Eu
Sm
Tb
Gd
Ho
Dy
Tm
Er
Lu
Yb
1
1
10
Sample/ REE chondrite
100
100
1000
Nd
Vertentes/Floresta Complex
Cs
Ba
Rb
U
Th
K
Nb
Ce
La
Pr
Pb
P
Sr
Zr
Nd
Dy
Eu
Sm
Ti
Yb
Y
Vertentes/Floresta Complex
0.1
0.1
Sample/ Primitive Mantle
La
Lu
1000
Rb
0.1
Cs
10
0.1
São Joãozinho Orthogneiss
Lu
La
Pr
Ce
Pm
Nd
Eu
Sm
Tb
Gd
Ho
Dy
Tm
Er
Lu
Yb
1000
500
100
100
Nb
30
10
FG
3
10
VAG+
syn-COLG
A
ORG
OTG
Whalen et al. (1987) 50
Pearce et al. (1982) 1
1
FeOt/MgO
WPG
500
Zr+Nb+Ce+Y
5000
1
10
100
Y
1000
FeO*
Ultrabasic
Basic
Intermediate
Acid
Alkaline
ne
ph
el
in
ite
es
nd
y-a
ch
a
r
T
Ph
on
ol
i tic
Mugearite
Hawaiite
Tholeiitic Series
Basalt
ite
Rhyolite
Dacite
Basaltic
andesite
5
Trachyte
Benmoreite
te
ph
rit
e
Ne
ph
eli
nit
e
10
Ba
sa
ni
te
Na2O+K2O
Phonolite
Andesite
Calc-alkaline Series
Subalkaline/Tholeiitic
0
40
45
50
55
SiO2
60
65
70
Cox et al. (1979) Pearce (1982) Al2O3+K2O
MgO
Irvine and Baragar (1971) Boynton (1984) Ti/100
A = IAT
B = MORB, CAB, IAT
C = CAB
D = WPB
A
D
B
C
Zr
3Y
Pearce and Cann (1973) Pearce and Norry (1979) A
Eclogite
25% Garnet
amphibolite
Adakites and Archean TTG
A - MORB partial melting
curve with eclogite as a
restite
Adakite and Archean TTG
10% Garnet
amphibolite
Classical Island Arc
Amphibolite
Normal andesite
and dacite
B
MORB
MORB
Defant et al. (1991) Mar)n (1986) Geodynamic hypothesis
2.2 Ga
Sea level
2.2-2.18 Ga
~2.18 Ga
Back-arc extension
Slab retreat
2.18-2.13 Ga
Delamination of lower crust
Active continental margin
(RN Domain)
Archean microcontinental
fragment
Differentiated oceanic
arc crust
Primitive oceanic
arc crust
Oceanic crust
2.13-2.10 Ga
Continental crust
Delamination of lower crust
~2.10 Ga
2.06-2.04 Ga
Back-arc extension
Slab retreat
Active continental margin
(RN Domain)
Archean microcontinental
fragment
Oceanic crust
Evolved arc crust
(Vertentes Complex)
Differentiated oceanic
arc crust
Primitive oceanic
arc crust
Salgadinho Complex
2.0-1.98 Ga
Cabaceiras Complex
São Joaozinho orthogneiss
Serviço Geológico
do Brasil – CPRM
Available in DOI: 10.1016/j.jsames.2014.06.009