Magnetic Susceptibility and Strain Mechanism of Albite-enriched facies of Madeira A-type Granite, Pitinga Mineral Province, Amazon Craton, Brazil

1. Spectrum EDS
Fe
Fe
2.00 4.00 6.00 8.00 keV
O
Ca
Ca
F
Fe
Si
MMAAGGNNEETTIICC MMIINNEERRAALLOOGGYY
400
k(n)
350
300
250
200
150
100
50
0
-200 -100 0 100 200 300 400 500 600 700 T°C
k = 15,7 mSI
-200 -100 0 100 200 300 400 500 600 700 T°C
300
250
200
150
100
50
0
k(n)
k = 2,62 mSI
0
10
20
30
40
50
60
-200 -100 0 100 200 300 400 500 600 700 T°C
k(n)
k = 0,22 mSI
-200 -100 0 100 200 300 400 500 600 700 T°C
100
90
80
70
60
50
40
30
20
10
0
k(n)
k = 1,29 mSI
330000µµmm
MMtt
KKffss
QQzz
550000µµmm
MMtt
QQzz
ZZrr
CCsstt
AAnnnn
2.00 4.00 6.00 8.00
Spectrum EDS
O
Fe
Fe
Fe
keV
220000µµmm
KKffss
QQzz
HHmmtt
Spectrum EDS
Fe
Fe
Fe
2.00 4.00 6.00 8.00 keV
O
CCoorree aallbbiittee--eennrriicchheedd ggrraanniittee
BBoorrddeerr aallbbiittee--eennrriicchheedd ggrraanniittee
30
25
20
15
10
5
0
0 500 1000 1500 2000 2500
IRM(A/m)
H (mT)
GM5
GM1
GM19
60
0 500 1000 1500 2000 2500
50
40
30
20
10
0
H (mT)
IRM(A/m)
5
2
1
0
IRM(A/m)
H (mT)
0 500 1000 1500 2000 2500
3
4
6
7
8
9
0 500 1000 1500 2000 2500
H (mT)
IRM(A/m)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
GM24
550000µµmm
HHmmtt
QQzz
KKffss
FIGURE 3. The isothermal remanent magnetisation (IRM) acquisition and temperature dependence of the
magnetic susceptibility for four selected specimens of the albite-enriched granite.
Verwey
transition
magnetite Curie
temperature
hematite Néel
temperature
Morin
transiton in
hematite
heating curve cooling curve
heating curve cooling curve
heating curve cooling curve
heating curve cooling curve
Hopkinson effect
in magnetite
2.00 4.00 6.00 8.00keV
Spectrum EDS
Fe
Fe
Si
Al
O
Specimens with low
remanent coercivity
Specimens with high
remanent coercivity
High Susceptibility magnitudes / Ferromagnetic minerals
Low Susceptibility magnitudes / Paramagnetic minerals
SSTTRRAAIINN MMEECCHHAANNIISSMMSS
FIGURE 2. Microestrutures in the albite-enriched granite developed in feldspars and quartz.
Strain
rate
High T °C
Low T °C
KKffss
AAbb II
A
00,,11 mmmm
KKffss
D
00,,55 mmmm
AAbb II
QQzz IIII
KKffss
KKffss
Stress
C
QQzz II
QQzz IIAAbb II
AAbb II
00,,11 mmmm
11 mmmm
H
QQzz IIII
QQzz II
QQzz II
KKffss
AAbb
CChhll
11 mmmm
G
PPoollyy
QQzz II
QQzz II
AAbb
QQzz IIII
QQzz IIII CChhll
QQzz II
QQzz
QQzz II
KKffss
CChhllZZ
XX11 mmmm
F
QQzz II
QQzz II
CChhll CChhll
AAbb
AAbb
EEpp
E
11 mmmm
AAbb II
CChhll
EEpp
QQzz II
EEpp
AAbb
KKffss
Deformation lamellae
Grain Boundary Migration
Bulging recrystallisation
Chessboard subgrains
Undoluse extinction
Subgrain Rotation
Growth twins with steps
Feldspars
Quartz
AAbb II
B
KKffss
00,,11 mmmm
KKffss
Progressive deformation
CCoorree aallbbiittee--eennrriicchheedd ggrraanniittee
BBoorrddeerr aallbbiittee--eennrriicchheedd ggrraanniittee
Monzogranite
Acknowledgements
Astrid Siachoque Velandia1, Carlos Alejandro Salazar1, Martha Edith Velasquez1
1Dpto. Geology, Federal University of Amazon
FFlloorriiaannóóppoolliiss -- BBrraazziill
2200--2255 SSeepptteemmbbeerr 22001155
MMAAGGNNEETTIICC SSUUSSCCEEPPTTIIBBIILLIITTYYAANNDD SSTTRRAAIINN MMEECCHHAANNIISSMM OOFF
AALLBBIITTEE--EENNRRIICCHHEEDD FFAACCIIEESS OOFF MMAADDEEIIRRAAAA--TTYYPPEE GGRRAANNIITTEE,,
PPIITTIINNGGAA MMIINNEERRAALL PPRROOVVIINNCCEE,, AAMMAAZZOONN CCRRAATTOONN..
GGEEOOLLOOGGIICCAALL SSEETTTTIINNGG
0 4 km
60°07'30'‘W
0°45'S
Brazil
AM
FIGURE 1. A) Localization of the study area, NE Amazonas State of Brazil. B) Lithological Map Madeira
Granite taken from Costi et al., (2000)
Regional Lineaments
A) B)
Pitinga Mining district
NThe Pitinga Mine is the largest Sn producer in Brazil (Figura 1A). The Madeira deposit is associated with
albite-enriched granite facies of A-type Madeira granite (~1820 Ma, Bastos Neto et al. 2014).
The Pitinga region is located in the southern portion of the Guyana Shield (Almeida et al. 1981), is locat-
ed in the Uatumã-Anauá Domain (Reis et al. 2003) of te Tapajós-Parima Province (2.03-1.88 Ga) accord-
ing to the tectono-geochronological model given by Santos et al. (2000).
The Madeira granite (Figura 1B) contains four facies (Costi et al. 2000). The amphibole-biotite
syenogranite facies (1824 ±2 Ma); the biotite-alkali-feldspar granite facies (1822 ±2 Ma); the albite-
enriched granite facies intruded the older facies, it is subdivided in two subfacies: the core albite-enriched
granite and the border-enriched granite (1820 ±2 Ma); the hypersolvus alkali feldspar porphyritic granite
facies (1818 ±2 Ma).
Amphibole-biotite
syenogranite
Biotite-alkali-feldspar
granite
Core albite-enriched
granite
Porphyritic hypersolvus
alkali feldspar granite
Border albite-enriched
granite
PALEOPROTEROZOIC
MADEIRA GRANITE
AAMMSS AANNDD SSPPOO DDAATTAA
Pj
SSPPOO
Mafic
T
Pj Pj
T
GM19 GM6GM1GM3 Mafic Quartz Quartz
Mineral Lineation
Intermediate axes
Mineral Foliation
T T
Pj Pj
CCoorree aallbbiittee--eennrriicchheedd ggrraanniittee BBoorrddeerr aallbbiittee--eennrriicchheedd ggrraanniittee
Oblate - Prolate SPO
ellipsoids (0 > T < 0)
FIGURE 4. The ASM and SPO fabric ellipsoids in the albite-enriched granite.
Oblate - Prolate SPO
ellipsoids (0 > T < 0)
Lowest anisotropy
degrees (Pj ~ 1.2)
Highest anisotropy
degrees (Pj ~ 1.4)
1,115
-1
1
T
0 Pj
-1
1
T
0
1,086
Pj
Magnetic Lineation
Intermediate axes
Magnetic Foliation
T
1
0
-1
1,110
Pj
T
1
0
-1
1,069
Pj
AAMMSS
GM5
n = 20
GM1
n = 17
GM19
n = 18
GM24
n = 15
CCoorree aallbbiittee--eennrriicchheedd ggrraanniittee BBoorrddeerr aallbbiittee--eennrriicchheedd ggrraanniittee
Prolates AMS ellipsoids
(T < 0)
Oblates AMS ellipsoids
(T > 0)
Highest anisotropy
degrees (Pj > 1.04)
Lowest anisotropy
degrees (Pj < 1.02)
References
- Almeida, F.F.M., Hasui, Y., Brito Neves, B.b., Fuck, R.A., 1981. Brazilian structural Provinces: an introduction. Earth-Sciences Reviews 17, 1-29.
- Bastos Neto, A.C., Ferron, J.T.M.M., Chauvet, A., Chemale, F.Jr., Lima, E.F., Barbanson, L., Costa, C.F.M. 2014. U-Pb dating of the Madeira Suite and structural control of the albite-enriched granite at Pitinga (Amazonia, Brazil):
Evolution of the A-type magmatism and implications for the genesis of the Madeira Sn–Ta–Nb (REE, cryolite) world-class deposit, Precambrian Res., 243 (2014), pp. 181–196
- Costi, H.T. (2000): Petrology of Rare Metals-, High-F-Alkaline Granites: the Example of the Albite Granite from the Pitinga mine, Amazonas State, Brazil. Doctoral thesis, Federal Univ. of Pará, Belém, Brazil (in Portuguese).
- Santos, J.O.S., Hartmann, L.A., Gaudette, H,E., Groves, D.I., Mcnaughton, N.J., Fletcher, I.R. 2000. A new understanding of the Amazon Craton Provinces based on integration of field mapping and U-Pb and Sm-Nd geochronolo-
gy. Gondwana Research 3 (4), 453-488.
- Reis, N.J., Fraga, L.M., Faria, M.S.G., Almeida, M.E., 2003. Geologia do Estado de Roraima, Brasil. In: Rossi, F., Jean-Michel, L., Vasquez, M.L. (Eds.), Geology of France and Surrounding Areas, vols. 2–4. Ed. Brgm. Paris,
França, pp. 121–134.
CCOONNCCLLUUSSIIOONNSS
SSPPOOAAMMSS
S0
S0
N
1 3
3 1
NE-SW trending
strike-slip system
FIGURE 5. Emplacement model for the
albite-enriched granite.
2. The magnetic fabric was registered during crystallization
processes in the core albite-enriched granite
3. Hydrothermal alteration is responsible by the
hematization of magnetite and oxidation of the albite-
enriched granite observed in the lowest magnetic suscepti-
bility magnitudes in the border albite-enriched granite
1. The strains mechanisms of silicates are related with weak
solid-state deformation. These microestrutures in granitic
rocks indicate strain rates of ~400°C T.
4. The measured AMS and SPO was interpreted as
magmatic foliation (S0) like results of primary deformation.
Both petrofabrics are predominantly subcoaxial.
5. The plutonic emplacement in the upper crust of these
granite was result of nested pluton process controlled by
NE-SW trending strike-slip system and predominantly
dextral kinematics, which is an expression of regional
deformation (Figure 5).
Brittle fault with
cataclastic deformation