The Graciosa Province includes some of the most expressive Neoproterozoic occurrences of A-types granites and syenites in southern Brazil formed in extensional post-collisional tectonic environments during the final stages of the Brasiliano/Pan- American Cycle. Plutons from this region are characterized by the coexistence of alkaline and aluminous petrographic associations, which makes this region interesting for a better understanding of the genetic relationships between these two petrographic associations. Petrographic evidences for hydrothermal alteration are locally found in two occurrences of the province, it is the case of Mandira and Guaraú plutons. The petrographic varieties known in these plutons show special mineralogy characteristics when compared to other occurrences in the province. Some of them are the significant occurrences of metasomatized rocks, including albitised granites and greisens, which are interesting examples for the study of accessory minerals behavior.

1. Review of the geotectonic setting of the
Graciosa Province SE-Brazil, and geological
characterization of the Mandira and Guaraú plutons.
Astrid Siachoque Velandia
Phd. Student Research
Docente Responsável: Silvio RF Vlach
NOVEMBRO, 2016
SEMINÁRIOS GERAIS II

2. INTRODUCTION
The Mantiqueira Province
“Brasiliano Orogenic Cycle”
Brasiliano I: 880 Ma and 730-700 Ma
Brasiliano II: 640-620 Ma and 600 Ma
Brasiliano III: 595-560 Ma and 520-500 Ma
Dom Feliciano belt (south domain)
Ribeira belt (central domain)
Araçuaí belt (north domain)

3. THE GRACIOSA PROVINCE
(from Heilbron et al., 2004; Prazeres Filho et al., 2003)

4. PETROGRAPHIC ASSOCIATIONS
ALKALINE
Metaluminous alkali-feldspar syenites to
typically peralkaline hypersolvus granites.
Biotite, Ca and Na-Ca pyroxenes, as well
as, Na and Na-Ca amphiboles represent
the major mafic phases. Zircon, apatite,
allanite, sphene, magnetite and ilmenite
as accesory minerals.
Alkaline series I, II and II
ALUMINOUS
Has a subalkaline character and is composed
of metaluminous to moderately peraluminous
subsolvus biotite syeno- and monzogranites.
Biotite and Ca-amphibole are the typical mafic
minerals. Chevkinita, magnetite, ilmenite,
sphene and sphalerite as accesory minerals.
Astrophyllite, narsarsukite, britholite and
nacarenobsite occur in the most evolved
varieties.
Aluminous series I and II
(Gualda and Vlach, 2007b)

5. GEOCHEMISTRY
Data sources: Kaul and Cordani (2000),
Gualda and Vlach (2007b) and Garin
and Vlach (unpublished data)
Alkaline association
Aluminous association +

6. THE MANDIRA PLUTON
NEO
PROTEROZOIC
CENOZOIC
MESO
PROTEROZOIC
Cover sediments
Mandira 1 Acaraú
Foliated Granites
Mica schist
Migmatites
PALEO
PROTEROZOIC
ARCHEAN
Mandira
Mandira Pluton
(From IPT, 1989; Oliveira, 1989).

7. MANDIRA
• Peralkaline alkaline-feldspar granites, hypersolvus, leuco- to hololeucocratic with
massive structures or locally orientated by brittle deformation and equi- to
inequigranular texture. i) Riebeckite alkaline feldspar granites, ii) Biotite mesoperthite
granites, iii) Alkali-feldspar granites.
(Oliveira, 1989).

8. MANDIRA Riebeckite, brown biotite and green-white micas as mafic phases. Accessory minerals
include zircon, fluorite, allanite, astrophyllite, stilpnomelane and sphalerite.

9. MANDIRA I
Sieno- and alkaline-feldspar granites, subsolvus, leuco- to hololeucocratic with massive structures
(sometimes orientated). Rocks from this unit present medium to fine-grained and inequigranular to
porphyritic textures, commonly rapakivi. i) Biotite mesoperthite granites, ii) Porphyritic and/or
Rapakivi granites .
(Oliveira, 1989).

10. MANDIRAI Green biotite and subordinated hornblende are the main mafic phases. Allanite, opaques,
fluorite, zircon, apatite and stilpnomelane as accessory minerals.

11. ACARAÚ Alkaline feldspar, hypersolvus with coarse to medium-grained xenomorphic, local
hipidiomorphic, inequigranular with occasionally granophyric textures. These granites
presented cataclastic textures associated with local fault zones. i) Alkali-(Fe)hastingsite
granites, ii) Biotite mesoperthite granites
(Oliveira, 1989).

12. Hornblende (Fe-hastingsite) as the characteristic mafic phase, accompanied by biotite,
allanite, opaques, fluorite, titanite, zircon and stilpnomelane. Rarely riebeckite,
carbonates and apatite.
ACARAÚ

13. ALBITISEDGRANITES
Leucocratic granites with medium-grained inequigranular, hypidiomorphic granular texture and local
granophyre intergrowths. The replacement of perthitic alkali feldspar and plagioclase by late albite
forming typical chessboard pattern, albite swapped rims albite-mantled in plagioclase crystals are
common features in these granites.
(Oliveira, 1989).

14. GREISENS
• Altered rocks with massive structure, medium to fine-grained heterogranoblastic texture. The main
constituents of these rocks are quartz and sericite. Green biotite, sphalerite,albite. Zircon,
fluorite, allanite, magnetite, ilmenita, galena, pyrite and chalcopyrite as accessory minerals.
Rarely, garnet, cassiterite and carbonates. i) Quartz and sericite, ii) Quartz, iii) Sphalerite, sericite
and quartz, iv) Chlorite topaz and quartz.
(Oliveira, 1989).

15. THE GUARAÚ PLUTON
Turvo Formation
Açungui Supergruop
Atuba Complex
Itapeuna Intrusive Suite
Guaraú Granite
Alluvian deposits
Banded gneiss Augen gneiss
Marble Phyllite Micaschist
Paragneiss Micaschist Phyllite
Granite
Desemborque Azeite NEO
PROTEROZOIC
CENOZOIC
MESO
PROTEROZOIC
PALEO
PROTEROZOIC
(From CPRM, 2014).

16. DESEMBOQUE Comprises grayish, massive structure, metaluminous to moderately peraluminous biotite sienogranites and
alkali-feldspar granites. i) Biotite granites, ii) Porphyritic biotite granites, iii) Porphyry granites, iv)
Microgranites, v) Pegmatites, vi) lamprophyric and vii) diabasic dykes.
(Garcia, 2015)

17. DESEMBOQUE Rocks from this unit are composed predominantly by alkali feldspar, plagioclase and quartz accompanied by
biotite, muscovite, ilmenite, magnetite and hematite. Zircon, fluorite, allanite, cassiterite, pyrite,
columbite and topaz as accessory minerals.
(Garcia, 2015)

18. • Garcia, R.P., 2015. Evolução magmática e hidrotermal de granitos de “ tipo-A ” reduzidos : o exemplo
do Pluton Desemborque , Maciço Programa de Pós-Graduação em Mineralogia e Petrologia. Thesis.
Universidade de São Paulo.
• Gualda, G.., Vlach, S.R.F., 2007b. The Serra da Graciosa A-type Granites and Syenites, southern
Brazil. Part 2: Petrographic and mineralogical evolution of the alkaline and aluminous associations.
Lithos 93, 310–327.
• IPT, 1989. Indicação preliminar de áreas prioritárias para recomposição da cobertura vegetal na
Serra do Mar afetadas por poluição na área de Cubatão., in: Relatório N°.24.293. Instituto de
pesquisas tecnológicas do estado de São Paulo, São Paulo.
• Heilbron, M., Pedrosa-Soares, A.C., Campos Neto, M. da C., Silva, L.C. da, Trouw, R.A.J., Janasi, V.
de A., Mantesso-Neto, V., Bartorelli, A., Carneiro, C.D.R., Brito-Neves, B.B. de, 2004. Província
Mantiqueira. Geologia do continente sul-americano: evolução da obra de Fernando Flávio Marques
de Almeida 203–235.
• Oliveira, M.C.., 1989. Petrologia do Maciço Granítico Mandira. Thesis. Universidade de São paulo.
• Prazeres Filho, H.J. dos, Harara, O.M., Basei, M.A.S., Passarelli, C.R., Siga Jr, O., 2003.
Litoquímica, geocronologia U-Pb e geologia isotópica (Sr-Nd-Pb) das rochas graníticas dos batólitos
Cunhaporanga e Três Córregos na porção sul do Cinturão Ribeira, Estado do Paraná. Geologia
USP. Série Científica 3, 51–70.
REFERENCES