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Precambrian Research 155 (2007) 69–97
Geochemistry and zircon geochronology of the I-type high-K
calc-alkaline and S-type granitoid rocks from southeastern
Roraima, Brazil: Orosirian collisional magmatism evidence
(1.97–1.96 Ga) in central portion of Guyana Shield
Marcelo E. Almeida a,b,∗, Moacir J.B. Macambira b, Elma C. Oliveira b
a CPRM-Geological Survey of Brazil, Av. André Araújo 2160, Aleixo, CEP 69060-001, Manaus, Amazonas, Brazil
b Isotope Geology Laboratory, Center of Geosciences, Federal University of Pará, CP 8608, CEP 66075-110, Belém, Pará, Brazil
Received 13 August 2006; received in revised form 5 January 2007; accepted 16 January 2007
bstract
The understanding of the geological evolution of the Uatumã-Anauá Domain in southeastern Roraima, central region of Guyana
hield, is of major significance in the study of the Amazonian craton. This region lies between some major Paleoproterozoic
eological–geochronological provinces: Tapajós-Parima or Ventuari-Tapajos (dominant), Maroni-Itacaiúnas or Transamazon (north-
est) and Central Amazonian or Central Amazon (southeast and east). Geological mapping of the northern area of Uatumã-Anauá
omain, integrated with whole rock geochemistry data and previous and new Pb-evaporation and U–Pb zircon geochronology,
oint out for a plutonic collisional magmatic event (1975–1968 Ma) represented by I-type high-K calc-alkaline (Martins Pereira)
nd S-type (Serra Dourada) granitoid rocks. This magmatism was probably generated from crustal sources by partial melting during
malgamation of the TTG-like Anauá magmatic arc (2028 Ma) with Transamazonian (2.2–2.0 Ga) and Central Amazonian (older
han 2.3 Ga) terranes. Local cumulatic leucogranites fills planar structures of the Martins Pereira granites. These leucogranites show
ounger ages (1909 Ma) and several inherited zircons (2354, 2134, 1997 and 1959 Ma), suggesting origin from crustal sources.
2007 Elsevier B.V. All rights reserved.
geochreywords: Paleoproterozoic; Granitoid rocks; Guyana Shield; Zircon
. Introduction
The Guyana Shield, with a surface area of nearly
.5 million km2, represents the northernmost section of
he Amazonian craton. This shield was predominately
ormed during protracted periods of intense granitic
agmatism, bracketed between 2.1 and 1.9 Ga (Fig. 1a
∗ Corresponding author. Tel.: +55 92 2126 0301;
ax: +55 92 2126 0319.
E-mail address: marcelo almeida@ma.cprm.gov.br
M.E. Almeida).
301-9268/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.precamres.2007.01.004onology; Geochemistry
and b). Despite representing an intricate component of
the Amazonian craton, the Guyana Shield has seen only
limited attention among the scientific community. Geo-
logical maps of the region are scarce (e.g. CPRM, 1999,
2000a; Delor et al., 2003), and only few petrographi-
cal, geochemical and geophysical studies are available.
Comparison between previous studies from the Guyana
Shield has been hampered by a lack of dependable age
determinations, implying large errors (±50–100 Ma),
which preclude any attempt to establish a fine chronol-
ogy of the magmatic and metamorphic events.
The study area is concentrates on the central part
of the Guyana Shield, in southeastern Roraima State
70 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
h maps
00, 200Fig. 1. The studied area location in Roraima State, plotted on the sketc
to (a) Tassinari and Macambira (1999, 2004) and (b) Santos et al. (20
(2003) modified by CPRM (2006).
(Brazil). Recent zircon geochronology data demon-
strate that igneous rocks cropping out in this region
(c. 4970 km2, Fig. 2) show ages of 2.03 Ga (Faria et
al., 2002) and 1.97–1.96 Ga (Almeida et al., 1997;
CPRM, 2003), similar to the Tapajós Domain in Cen-
tral Brazil Shield (Santos et al., 2000; Lamarão et al.,
2002). However, the characteristics and significance of
these events and ages are not fully understood (CPRM,
2000a; Almeida and Macambira, 2003). An example of
this can be seen in the 2.03–1.96 Ga magmatic event
which, unlike the 1.90 Ga calc-alkaline magmatism, is
uncommon in other regions of the world. In addition
the Tapajós Domain in Central Brazil Shield (south-
ern Amazonian craton) and parts of the São Francisco
Craton, Paleoproterozoic tectonic and magmatic activ-
ity between c. 2.0 and 1.9 Ga is recorded in Western
Australia (Gascoigne Complex, Dalgaringa Supersuite,
2005–1970 Ma) by Sheppard et al. (2004) and south-
ern Australia (Gawler Craton, Miltalie Gneiss, ca.
2000 Ma) by Daly et al. (1998). The Taltson Magmatic
Zone of northern Canada (McDonough et al., 1993)
and Kora-Karelian orogen of northern of Baltic Shield
(Daly et al., 2001) also show 2.0–1.9 Ga magmatic
events.
The aim of this paper is to provide new geochem-
ical and geochronological constraints on the Martins
Pereira and Serra Dourada granitoid rocks (Almeida etof the Geochronological Provinces of the Amazonian craton according
6), and on (c) the map of the lithostructural domains after Reis et al.
al., 2002). It is hoped that such studies will contribute
to a better understanding of the lithostratigraphy, ori-
gin and geodynamic evolution of the northern part of
the Uatumã-Anauá Domain, in the central portion of the
Guyana Shield (Fig. 1). These data will be integrated
with previous geochemical and geochronological data
for other magmatic associations, mainly calc-alkaline
granitoids older than 1.90 Ga. Particular focus will be
placed on comparative geochemical and geochronology
data from previous studies in the same region and from
the southern part of the Amazonian craton.
2. Geological setting
Regional geological maps (CPRM, 2000a; Almeida
et al., 2002) and zircon geochronological data (Almeida
et al., 1997; Santos et al., 1997; Macambira et al., 2002;
CPRM, 2003) have shown that Paleoproterozoic grani-
toid and volcanic rocks (1.97–1.81 Ga) are widespread
in southeastern Roraima. These intrusive and extrusive
rocks are emplaced within poorly exposed basement
rocks that have maximum ages of around 2.03 Ga (Faria
et al., 2002).According to recent evolutionary models proposed
for the Amazonian craton, the study area can be
divided into several provinces. According to the work
of Tassinari and Macambira (1999,2004), the study area
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 71
Fig. 2. Simplified geological map of Southeastern Roraima State modified from Almeida et al. (2002) and CPRM (2000a, 2005): (1) Plio-Pleistocene
sedimentary covers; (2) Caracaraı́ Gabbro (1.52 Ga?); (3) Foliated granitoids (1.72 Ga), mylonitic granites (1.89 Ga), granulites, augen gneisses,
metagranitoids and orthogneisses from Rio Urubu Complex (1.96–1.93 Ga); (4) S-type Curuxuim (garnet) Granite (1.97 Ga?); (5) Metavolcano-
s oderna
c d minor
G al to (
M 2.03 Ga
i
A
s
S
c
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t
edimentary sequence (Cauarane Group > 1.97 Ga); (6) (a) A-type M
harno-enderbite (1.89 Ga); (7) Igarapé Azul and Caroebe Granites an
ranite (1.96 Ga); (9) High-K calc-alkaline granitoids with (a) norm
etavolcano-sedimentary sequence (Cauarane Group related rocks; <
s largely enclosed in the Ventuari-Tapajós and Central
mazonian provinces, with a subordinate northeastern
ection falling within the Maroni-Itacaiúnas province.
antos et al. (2000, 2006) argue that all provinces were
ollectively affected by the K’Mudku Shear Belt in this
ame region (Fig. 1a and b). These authors conclude
hat Paleoproterozoic orogenic belts or magmatic arcs(1.81 Ga) and Mapuera Granites (1.87 Ga), and minor enderbite and
volcanic rocks (1.90–1.89 Ga); (8) S-type Serra Dourada (cordierite)
b) high U, Th, K contents (Martins Pereira Granite, 1.97 Ga); (10)
?) and TTG calc-alkaline association (Anauá Complex, 2.03 Ga).
(e.g. Ventuari-Tapajós or Tapajós-Parima, and Maroni-
Itacaiúnas or Transamazon provinces) accreted to the
Archean craton with time and/or represent a set of rocks
produced from melting of Archean crust (Fig. 1a and
b; Cordani et al., 1979; Teixeira et al., 1989; Tassinari,
1996; Tassinari and Macambira, 1999, 2004; Santos et
al., 2000, 2004, 2006).
brian
obtained by water-mechanical and dense liquid concen-72 M.E. Almeida et al. / Precam
The Tapajós-Parima (or Ventuari-Tapajós) Province
is a Paleoproterozoic orogenic belt trends north–
northwest and includes geological units which range
from ∼2.10 to 1.87 Ga in age (Santos et al., 2000,
2006; Tassinari and Macambira, 1999, 2004). This
province was subdivided into four domains by Santos
et al. (2000): Parima and Uaimiri, to the north, and
Peixoto Azevedo and Tapajós, to the south. Southeastern
Roraima belongs to the Uaimiri Domain. The Central
Amazonian Province of the study area (Fig. 1a and
b) display granitoid and volcanic rocks (1.88–1.70 Ga)
lacking regional metamorphism and compressional fold-
ing (Santos et al., 2000; Tassinari and Macambira,
1999), and its basement is exposed scarcely. The age
for this basement has been estimated via Nd-model
ages at around 2.3–2.5 Ga (Tassinari and Macambira,
1999, 2004). According to these authors, the recorded
Archean rocks in the Amazonian craton are only exposed
in Imataca (Venezuela), Carajás and southern Amapá-
northwestern Pará (Brazil). The Maroni-Itacaiúnas (or
Transamazon) Province is also characterized by an oro-
genic belt with Rhyacian ages (2.25–2.00 Ga, Fig. 1a
and b) and is correlated to the Birimian belt in West
Africa (Tassinari and Macambira, 1999, 2004; Santos et
al., 2000; Delor et al., 2003). The K’Mudku Shear Belt is
characterized by low- to medium-grade mylonitic zones
with ca. 1.20 Ga ages and cross-cuts the Rio Negro,
Tapajós-Parima and Transamazon provinces, (Santos et
al., 2000).
Taking into account lithological associations and
geochronological data, Reis et al. (2003) and CPRM
(2006), divided Roraima into four major domains—
Surumu, Parima, Central Guyana and Uatumã-Anauá
(Fig. 1c). Each of these domains contains a wide range of
rock types and stratigraphic units. Southeastern Roraima
is composed of the Central Guyana and Uatumã-Anauá
lithostructural domains, that correspond to the K’Mudku
Shear Belt and Uaimiri Domain, respectively (north-
ern Tapajós-Parima Province) proposed by Santos et al.
(2000).
The Central Guyana Domain (CGD) consists
primarily of granulites, orthogneiss, mylonites and meta-
granitoids (Rio Urubu Metamorphic Suite) associated
with low to high metamorphic grade metavolcanosed-
imentary covers (Cauarane Group) and S-type granite
(Curuxuim Granite). The lineaments trend are strongly
NE–SW trends (Figs. 1c and 2). The Uatumã-Anauá
Domain (UAD) is characterized by E–W to NE–SW lin-
eaments and the northern part of the domain Northern
Uatumã-Anauá Domain shows an older metamorphic
basement (Figs. 1 and 2) formed in a presumed
island arc environment (Faria et al., 2002). This base-Research 155 (2007) 69–97
ment is composed of TTG-like metagranitoids to
orthogneisses (Anauá Complex), enclosing meta-mafic
to meta-ultramafic xenoliths, and is associated with some
inliers of metavolcano–sedimentary rocks (Cauarane-
like). The basement rocks are intruded by S-type (Serra
Dourada Granite) and high-K, I-type calc-alkaline (Mar-
tins Pereira) granite plutons of c. 1.97–1.96 Ga (see
zircon geochronology section).
In the southern area of the Uatumã-Anauá Domain,
intrusive younger granites (with no regional deforma-
tion and metamorphism) are very common. The most
prominent magmatism is related to the calc-alkaline
Caroebe and Igarapé Azul granitoids (Água Branca
Suite) with coeval Iricoumé volcanic rocks. Locally
igneous charnockitic (Igarapé Tamandaré) and ender-
bitic (Santa Maria) plutons were also recorded. Several
A-type granite bodies are widespread in the Uatumã-
Anauá Domain (Fig. 2) represented by Moderna-
Água Boa (1.81 Ga) and Mapuera-Abonari (1.87 Ga)
granites.
3. Analytical procedures
3.1. Whole-rock geochemistry analysis
Whole-rock chemical analyses of 11 samples (milled
under 200 mesh) were done at the Acme Analytical Lab-
oratories Ltd. in Vancouver, British Columbia, Canada.
The analytical package includes inductively coupled
plasma-atomic emission spectrometer (ICP-AES) anal-
yses after LiO2 fusion for all major oxides (SiO2, TiO2,
Al2O3, MnO, MgO, CaO, K2O, Na2O, P2O5) and LOI.
Total iron concentration is expressed as Fe2O3. The
trace elements were analyzed by inductively coupled
plasma-mass spectrometer (ICP-MS), with rare-earth
and incompatible elements determined from a LiBO2
fusion and precious and base metals determined from an
aqua regia digestion. Additional 16 samples were com-
piled (and partially reinterpreted) from CPRM (2000a).
These last whole-rock chemical analyses were done at
the Geosol Laboratories S.A., Belo Horizonte, Minas
Gerais, Brazil.
3.2. Zircon isotope analysis
For isotope analysis, the zircon crystals were obtained
from samples with 2–20 kg. After crushing (milled to
60–80 mesh) and sieving, heavy mineral fractions weretrations, and processed under hand magnet and Frantz
Isodynamic Separator. In order to remove impurities,
zircon concentrates were washed with HNO ◦3 at 100 C
brian R
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M.E. Almeida et al. / Precam
10 min), submitted to ultrasound cube (5 min) and
nally washed on bidistilled H2O. The less magnetic
ircon concentrates (from five magnetic fractions) were
referred for hand-picking. Whenever possible only zir-
on grains free of alteration, metamictization features,
nclusions and fractures were selected for analysis, how-
ver it was not always possible (see zircon descriptions
elow). All selected grains for analysis were photomi-
rographed via a conventional optical microscope.
Single-zircon dating by Pb-evaporation and U–Pb
sotopic dilution in thermal ionization mass spectrometry
ID-TIMS) methods was performed at the Isotope Geol-
gy Laboratory (Pará-Iso), Federal University of Pará
UFPA), Brazil. The U decay constants are those recom-
ended by Steiger and Jager (1977), and errors are given
t the 95% confidence level. Ages of five samples were
btained by the Pb-evaporation technique established by
ober (1986, 1987), and only one sample was analyzed
y U–Pb ID-TIMS. All isotope analyses were carried out
n a Finnigan MAT 262 mass spectrometer in dynamic
ode using the ion counting detector.
In the Pb-evaporation method on a single zircon, the
elected grains were tied in Re-“evaporation”-filament
nd introduced in the mass spectrometer. The Pb was
ormally extracted from the crystals by heating in three
vaporation steps at temperatures of 1450, 1500 and
550 ◦C. The evaporated Pb was loaded on an “ioniza-
ion” filament, which is heated for the isotope analyses.
n this technique, the data were dynamically acquired
sing the ion counting system of the instrument. Pb sig-
al was measured by peak hopping in the 206, 207,
08, 206, 207, 204 mass order along 10 scans, defin-
ng one block of data with 18 207Pb/206Pb ratios. The
07Pb/206Pb ratio average of each step was based on five
locks or less, till the intensity beam was sufficiently high
or a reliable analysis. Usually, the average 207Pb/206Pb
atio obtained in the highest temperature step was taken
or age calculation, but the other steps are also consid-
red. Outliers were eliminated using Dixon’s test. The
07Pb/206Pb ratios were corrected for a mass discrimi-
ation factor of 0.12%± 0.03 amu−1, and results with
04Pb/206Pb ratios higher than 0.0004 were, in general,
iscarded. The ages were calculated with 2 sigma error
nd common Pb correction was done using appropriate
ge values derived from the two-stage model of Stacey
nd Kramers (1975). The obtained data were processed
n shareware Zircon program (Scheller, 1998), DOS sys-
em version.The Pb-evaporation on a single zircon method yields
pparent 207Pb/206Pb ages and the degree of concor-
ance of the analytical points is not possible to assess.
urthermore, zircon grains exhibiting a complex his-esearch 155 (2007) 69–97 73
tory, often yield mixed ages with no geological meaning
(Dougherty-Page and Bartlett, 1999). With these uncer-
tainties in mind, the age obtained for a single grain
is considered as a minimum age. This being the case,
as has been proposed in several studies (Kober, 1986;
Andsell and Kyser, 1991; Macambira and Scheller, 1994;
Söderlund, 1996), if a set of magmatic grains from the
same sample yields similar ages, it is possible to suggest
that such similarities indicate the time of the magmatic
crystallization or episodic Pb loss.
The U–Pb ID-TIMS procedures undertaken in
the Pará-Iso Laboratory followed those presented by
Krymsky (2002). All zircon fractions selected for anal-
ysis were previously air abraded with pyrite crystals
(20 mg and 0.1–0.5 mm diameter) in 1.2–1.8 psi pres-
sure for 30–40 min. After abrasion the zircon grains
were washed with HNO3 and HCl (100 ◦C, 30 min) and
H2O-Millipore (3 times). The grains were then washed
with methanol, weighed, spiked with 235U–205Pb tracer
and dissolved with a mixture of HF and HCl in PTFE
Teflon® bombs. Uranium and lead were separated with
anion-exchange resin (Dowex® 1× 8 200–400 mesh) in
HCl medium in 50–70 l columns. Uranium and Lead
were loaded with Si-gel and H3PO4 (1N) onto the same
out-gassed Re-filament and analyzed at 1400–1600 ◦C.
For zircon analyses, blanks are <30 pg Pb and <1 pg U.
The obtained data were processed in ISOPLOT/Excel
program version 2 (Ludwig, 1999). The commom Pb
interference was corrected using also the Stacey and
Kramers (1975) model.
4. Whole-rock geochemical results
4.1. Major and minor oxides, and trace elements
geochemistry
Analytical results of representative samples from
Martins Pereira, Serra Dourada and Anauá granitoid
rocks of the Northern Uatumã-Anauá Domain, including
leucogranite blobs and lenses, are presented in Table 1
and plotted in diagrams in Figs. 3–7. Serra Dourada and
Anauá results are extracted form CPRM (2000a). Cre-
porizão (CPRM, 2000b) and Old São Jorge (Lamarão
et al., 2002) granitoid rocks data from Tapajós region
are also plotted in some diagrams for comparison with
Martins Pereira granitoid rocks.
The Martins Pereira Granite consists of a com-
positionally wide series of rocks with SiO contents2
between 49.3 and 74.6 wt.% (Table 1). The associated
leucogranite pods and lenses have high SiO2 contents
(72.9–73.9 wt.%), but in the Harker diagrams show
no correlation with the Martins Pereira Granite. For
74 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Table 1
Chemical compositions of main plutonic associations of Northern Uatumã-Anauá Domain, such as Martins Pereira (meta)granitoid rocks, lenses and blobs of leucogranites, Serra Dourada granite
and Anauá Complex
The geochemical data were obtained from this study1 and CPRM (2000a)2. Abbreviations: a, amphibole; b, biotite; e, epidote; m, muscovite; D, diorite; Gb, gabbro; Gd, granodiorite; Mgr,
monzogranite; N, norite; Sgr, syenogranite; Tn, tonalite; Gn, gneiss; Lc, leuco; Mt, meta; P, porphyritic; – , not available values.
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 75
Fig. 3. (a–h) Selected Harker variation diagrams for Martins Pereira and Serra Dourada Granites, leucogranites and Anauá Complex. For references
see Table 1. Fields representing Creporizão (CPRM, 2000b) and Old São Jorge granites (Lamarão et al., 2002) of the Tapajós Domain are plotted
for comparison. For the linear regression are used only the Martins Pereira Granite samples.
76 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Fig. 4. Geochemical diagrams showing results from Martins Pereira Granite, leucogranites and Anauá Complex rocks (for references see Table 1).
Fields representing Creporizão (CPRM, 2000b) and Old São Jorge granites (Lamarão et al., 2002) are plotted for comparison: (a) K2O vs. SiO2
elds (fr
es. (b) lcontents displaying the shoshonite, high-K, medium-K and low-K fi
the linear regression are used only the Martins Pereira Granite sampl
Symbols as in Fig. 3.
instance, leucogranites with the same SiO2 contents
as Martins Pereira granatoid rocks, have low Na2O
(Fig. 3g), MnO (Fig. 3d), Fe2O3 + FeO (Fig. 3c) and
very high K2O (Fig. 4a) values.
Rock samples from Martins Pereira Granite are also
characterized by linear trends in the all Harker diagrams
(Fig. 3a–h). In these diagrams, excluding Na2O versus
SiO2, the statistic parameters show negative linear cor-
relations with regression agreement between 99% and
99.9%. Linear trends can result from several petrogenetic
processes, such as contamination, mixing, crystal frac-
tionation with no crystallizing phases change and partial
melting (e.g. Cox et al., 1987; Wilson, 1991). The lack
of significant compositional gaps in Harker diagrams for
Martins Pereira samples suggests that the main petroge-
netic process is likely related to partial melting or crystal
fractionation with no change in the mineral assemblage
being fractionated. However this last one requires a great
volume of mafic parental magma, not detected in the
region. The same is true for fractional crystallization pro-
cess with change in the crystallizing mineral phases (e.g.
hornblende out and biotite in), but in this case the result
are usually results in curvelinear Harker-plot trends (e.g.
Cox et al., 1987; Wilson, 1991) that are not observed for
Martins Pereira samples.
In contrast to the Martins Pereira samples, the Anauá
Complex and related rocks show lower SiO2 contents
ranging from 41.3% to 59.8% (Table 1), and dispersion in
the Harker diagrams (e.g. TiO2, MnO, Al2O3, Na2O and
Fe2O3t). When compared to the Martins Pereira grani-
toid rocks, the Anauá samples are characterized by lower
K2O and P2O5 contents (Figs. 4a and 3h) while havingom Peccerillo and Taylor, 1976; modified by Rickwood, 1989). For
og[CaO/(Na2O + K2O)] vs. SiO2 contents (from Brown et al., 1984).
higher Na2O and MgO (Fig. 3e–g) contents. The Serra
Dourada Granite shows remarkable low Na2O (Fig. 3g)
and K2O contents (Table 1).
Compared to the Martins Pereira granitoid rocks, the
1.99–1.96 Ga Old São Jorge and Creporizão granites
from the Tapajós Domain have lower TiO2 (Fig. 3a),
MnO (Fig. 3d) and P2O5 (Fig. 3h), and higher Na2O
(Fig. 3g) contents. The corresponding Harker diagrams
demonstrate that the Creporizão granites have a shorter
range and higher contents of SiO2 (65.2–73.4%, Table 1),
as well as lower MnO (Fig. 3d), Al2O3 (Fig. 3b) and K2O
(Fig. 4a) contents.
In the log[CaO/(Na2O + K2O)] versus SiO2 diagram
(Fig. 4b), all the studied granitoid rocks (excluding
Serra Dourada Granite) indicate calc-alkaline affinity,
with the samples plotting in the normal calc-alkaline
andesitic field. Only the Old São Jorge Granite shows
exclusive transitional character between normal and
mature arc series. Most of the granitoid samples also
plot in the high-K field (K2O versus SiO2 diagram,
Fig. 4a), however, the Martins Pereira and Old São
Jorge granites have a transitional high-K to slightly
shoshonitic character. It is also apparent from the K2O
versus SiO2 diagram that samples from the Creporizão
Granite display a transitional high-K to locally medium-
K trend, whereas Anauá types are medium-K to slightly
low-K. The leucogranites show high K contents (>7%)
and a highly fractionated character.The Martins Pereira and Creporizão granite com-
positions are transitional between metaluminous to
peraluminous, while the Old São Jorge granite is met-
aluminous to slightly peraluminous (Fig. 5a). Almost
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 77
Fig. 5. Martins Pereira and Serra Dourada granites, leucogranites and Anauá Complex samples plotted in the diagrams (for references see Table 1):
(a) Molecular Al2O3/(Na2O + K2O) vs. molecular Al2O3/(CaO + Na2O + K2O) (Maniar and Piccoli, 1989; mod. Shand, 1927) and (b) Na2O vs.
K2O plots showing S-type and I-type granites compositional data from Lachlan Folded Belt (LFB); (c) Rb vs. (Y + Nb) and (d) (K2O + Na2O)/CaO
vs. (Zr + Nb + Ce + Y). Fields representing Creporizão (CPRM, 2000b) and Old São Jorge granites (Lamarão et al., 2002) are plotted for comparison.
(c) VAG, Volcanic Arc Granites; ORG, Ocean Ridge Granites; syn-COLG, syn-collisional Granites; WPG, Within-Plate Granites, fields are from
P Pearce
g en from
I
a
A
o
S
i
s
s
h
t
fi
fi
D
g
s
W
earce et al. (1984) and post-COLG (post-collisional granites) from
ranites; FG, Fractionated felsic I- and S-type granites, fields are tak
-type are also represented. Symbols as in Fig. 3.
ll these granites show A/NK molar ratios < 2. Only the
nauá Complex rocks (A/NK molar > 2) and the lenses
f leucogranite are metaluminous and peraluminous. The
erra Dourada Granite is broadly peraluminous, plotting
n the S-type granite compositions. This granite body
hows A/CNK molar ratios of 1.1 and 1.3, while some
amples of the Martins Pereira Granite also show locally
igh A/CNK values. In the Na2O versus K2O diagram,
he Martins Pereira granitoid rocks plot on the I-type
eld, but several samples also plot near to the S-type
eld boundary (Fig. 5b) showing, as well as the Serra
ourada Granite samples, the lowest Na O/K O ratios.2 2
In the Rb versus (Y + Nb) tectonic discriminator dia-
rams (Fig. 5c), the Martins Pereira granite samples
how transitional VAG (granites to granodiorites) to
PG (biotite-rich tonalites) trends. Anauá rock-types(1996). (d) OGT, Orogenic granite types: unfractioned I- and S-type
Whalen et al. (1987). Compositional average of A-, M-, I-, S- and
generally plot in the VAG field, with correspondingly low
Rb contents. The Creporizão and Old São Jorge granites
samples dominantly plot in the VAG field, falling near
to the WPG boundary. Thus, excluding Anauá rocks,
most of the analyzed samples fall in the postcollisional
field of Pearce (1996), which suggests an increasing in
arc maturity (Brown et al., 1984; see Fig. 4a) or the
beginning of the transition from calc-alkaline to alkaline
magmatic series in orogenic to post-orogenic tectonic
settings (Bonin, 1990; Barbarin, 1999).
In the (K2O + Na2O)/CaO versus (Zr + Nb + Ce + Y)
diagram (Fig. 5d), the calc-alkaline Martins Pereira,
Creporizão and Old São Jorge granites plot on the unfrac-
tionated S- and I-type granites to transitional A-type
fields. Concerning the Martins Pereira granitoid rocks,
the higher Zr, Y and Ce contents are probably related
78 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Martins
ata fromFig. 6. Primitive mantle-normalized spidergram (Wood, 1979) for (a)
(c) Pods and lenses of leucogranites, and (d) Serra Dourada Granite. D
are also plotted for comparison. Symbols as in Fig. 3.
to the presence of accessory minerals such as epidote,
allanite and zircon, mainly in biotite-rich tonalite types.
However, their metaluminous to peraluminous nature
(Fig. 5a) and VAG character (Fig. 5c) point to I-type
granite affinity. Samples from Anauá Complex plot in
the unfractionated S- and I-type granites field with low
(K2O + Na2O)/CaO ratios. Only the blobs of leucogran-
ites and few Creporizão Granite samples plot on the
fractionated felsic granites field (Fig. 5d).
In the primordial mantle-normalized spidergrams, the
Martins Pereira Granite (Fig. 6a) exhibits depleted trace
element patterns for some HFSE such as Ta, Nb, P and Ti,
and does not show significant LILE depletion (e.g.Sr and
Ba), as observed for alkali-calcic granitoid rocks of more
mature arcs (Brown et al., 1984). This pattern is some-
what similar to those of the calc-alkaline granitoid rocks
from normal arcs (cf. Brown et al., 1984), though some
samples of the Martins Pereira Granite show strong Ti
and P depletion, like the average of mature arc granitoid
rocks. This geochemical behavior suggests that Martins
Pereira Granite belongs to transitional granitic magma-
tism, from normal to mature continental arcs (see also
Fig. 4a).Pereira granitoids (tonalites to monzogranites); (b) Anauá Complex;
granitoids of primitive, normal and mature arcs (Brown et al., 1984)
The Anauá spidergram pattern (Fig. 6b) displays
coherent Rb, Ba and K contents with primitive arcs
(Brown et al., 1984), however, U, Ta, Zr, Sm, Ti and
Y are enriched in relation to the primitive arc pattern.
All other elements (Th, Nb, La, Ce, Sr and P) in the
Anauá rocks show primitive to mature arcs transitional
values. The spidergram pattern of the blobs and lenses
of leucogranite (Fig. 6c) displays the higher Nb, Ta, La,
Ce and Hf fractionated values and steeply negative P and
Ti anomalies. The leucogranites also show moderate to
high Rb, Ba, Th and K contents in relation to chondrite
values. The Serra Dourada Granite (Fig. 6d) has Rb, Ba,
Sr, P and Ti (locally Rb, Nb and P) pattern remarkably
similar to the normal S-type average and La, Ce and
Y display more enriched contents than normal S-type
granites (e.g. Chappell and White, 1992).
4.2. Rare earth element (REE) geochemistryThe total REE contents of the studied granitoid rocks
are relatively similar (Table 1), except in the Anauá Com-
plex (138–148 ppm) and leucogranites (100–153 ppm)
samples. Martins Pereira (97–624 ppm) and Creporizão
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 79
F artins P
2 omplex
a
g
p
d
t
(
t
t
a
A
(
ig. 7. REE chondrite-normalized diagrams (Boynton, 1984) for (a) M
000b) and old São Jorge (Lamarão et al., 2002) granites; (c) Anauá C
s in Fig. 3.
ranites (104–541 ppm) show some REE enriched sam-
les, contrasting with Old São Jorge Granite which
isplays moderate to low REE contents (52–244 ppm).
The REE chondrite-normalized pattern of the Mar-
ins Pereira Granite (Fig. 7a) is enriched in the LREE
e.g. La with 80× to 400× the chondrite values), but
he LREE fractionation [(La/Sm) ratios range from 3.4n
o 6.7, exceptionally 8.0] is similar to the Creporizão
nd Old São Jorge granites (Fig. 7b). By contrast, the
nauá Complex (Fig. 6c) shows lower LREE contents
e.g. La with 50× to 100× the chondrite values) and lowereira granitoids (tonalites to monzogranites); (b) Creporizão (CPRM,
; (d) lenses of leucogranites and (d) Serra Dourada Granite. Symbols
(La/Sm)n ratios (1.9–4.6). The Anauá REE pattern is
probably controlled by hornblende and allanite-epidote
fractionation.
The Martins Pereira Granite shows variable HREE
contents (e.g.Yb and Lu ranging 3× to 60× the chondrite
values) and the degree of HREE fractionation [(Gd/Yb)n]
is similar to the Creporizão, Old São Jorge and Anauá
granites (1.1–4.5). In the more HREE enriched gran-
ites, the HREE patterns are normally flat. The wide
HREE range in the Martins Pereira types is probably
associated to the variable residual zircon retention dur-
brian80 M.E. Almeida et al. / Precam
ing partial melting process and different Zr saturation
level of magma (Watson and Harrison, 1983). The same
is observed in the leucogranite samples, though these
samples have atypical REE patterns, including positive
to weakly negative Eu anomaly, which point out for
cumulatic plagioclase occurrence (Fig. 7d). These REE
patterns may be also related to high hydrothermal activity
in the final stages of crystallization or chemical hetero-
geneities related to source(s). The Old São Jorge (Fig. 7b)
and Anauá (Fig. 7c) granitoid rocks exhibit the most
HREE depleted patterns.
The Anauá types show discrete negative to positive
Eu anomaly, with Eu *n/Eu ratios ranging from 0.8 to 1.2
(Table 1; Fig. 7c), suggesting occurrence of cumulate
plagioclase and/or hornblende fractionation. Overall,
the REE and Eu anomaly patterns (Fig. 7a,b; Table 1)
are similar among Martins Pereira (Eun/Eu* = 0.4–0.7),
Creporizão (Eun/Eu* = 0.3–0.8) and Old São Jorge
(Eun/Eu* = 0.4–1.0) granites. In the case of Martins
Pereira, the moderate to discrete negative Eu anomaly
probably demonstrates variable residual plagioclase
retention in the residue.
The Serra Dourada S-type granite (Table 1;
Fig. 7e) shows moderate total REE content (205–
223 ppm) and moderate to high negative Eu
anomaly (Eun/Eu* = 0.5–0.3). The LREE fraction-
ation [(La/Sm)n = 3.2–2.8] and HREE fractionation are
moderate to high [(Gd/Yb)n = 3.6–3.8].
5. Martins Pereira and Serra Dourada granites:
petrogenetic considerations
The Martins Pereira Granite is one of the most
prominent examples of Orosirian high-K calc-alkaline
plutonism in southern Roraima, outcropping in the
Northern Uatumã-Anauá Domain. The geological liter-
ature (e.g. Roberts and Clemens, 1993; Barbarin, 1999)
shows that the high-K calc-alkaline granitoid rocks are
very common in orogenic belts since Proterozoic times,
corresponding to 35–40% of all post-Archean metalu-
minous granitoid rocks found around the world. The
two main tectonic environments envisaged for high-K
magma generation are (Roberts and Clemens, 1993): (a)
continental arc (Cordirellan- or Andean-type), and (b)
post-collisional (Caledonian-type) settings.
In general, the tectonic setting discrimination dia-
grams (e.g. Pearce et al., 1984) diagnose the settings
in which the protoliths were formed better than the envi-
ronment where the magma was generated (e.g. Barbarin,
1999). This implies that these diagrams could denote
geochemical (and isotopic) characteristics of the sources
(inheritance), irrespective of the residual mineral com-Research 155 (2007) 69–97
ponents. In the hornblende-free Martins Pereira high-K
calc-alkaline granitoid rocks, for instance, linear and
continuous trends in Harker diagrams and absence of
coeval and large mafic batholiths suggest that the rocks
were generated by partial melting processes. However,
the sources are not yet fully understood, despite a num-
ber of geochemical features (e.g. K, U, Th, Rb and REE
enrichment) pointing towards the importance of crustal
rocks in the magma source.
Experimental data on the potential sources for high-K
calc-alkaline granitoid rocks have suggested several pos-
sibilities of crustal sources (e.g. Roberts and Clemens,
1993). These partial melting hypotheses yield composi-
tional differences among magmas produced by partial
melting of common crustal rocks, such as amphibolites,
tonalitic gneisses, metagreywackes and metapelites
under variable melting conditions (e.g. Patiño-Douce,
1996, 1999). This compositional variation can be
visualized in terms of major oxides ratios (Fig. 8a–c) or
molar oxide ratios (Fig. 8d). It can be seen in these plots
that partial melts derived from mafic to intermediate
source rocks have lower Al2O3/(FeO + MgO + TiO2),
(Na2O + K2O)/(FeO + MgO + TiO2) and molar
Al2O3/(MgO + FeOtot) ratios relative to those originated
from metapelites and metagreywackes (Fig. 8a–d).
Most Martins Pereira Granite samples generally plot
in the amphibolite and metabasalt–metatonalite fields
(Fig. 8a–d), showing low Al2O3/(FeO + MgO + TiO2),
(Na2O + K2O)/(FeO + MgO + TiO2) and molar
Al2O3/(MgO + FeOtot) ratios, but exhibit relatively
high CaO/(FeO + MgO + TiO2). This feature, asso-
ciated with relatively high Mg# values (32.5–45.3),
precludes a derivation from felsic pelite and/or
metagreywacke for Martins Pereira Granite, partic-
ularly the low-SiO2 samples (<65%). The SiO2-rich
samples (>65%), however, have lower Mg# val-
ues (24.7–30.7), higher Al2O3/(FeO + MgO + TiO2)
and (Na2O + K2O)/(FeO + MgO + TiO2) ratios, and
lower Al2O3 + FeO + MgO + TiO2 (15–18%) and
Na2O + K2O + FeO + MgO + TiO2 (8–10%) contents.
These Martins Pereira SiO2-rich samples, as well as
the Serra Dourada Granite samples, also show low
CaO + FeO + MgO + TiO2 contents (2–4%) and plot
in the metagreywacke field (Fig. 8a–d), suggesting
metasedimentary source contribution (at least locally) in
the Martins Pereira magma genesis. The most suitable
metasedimentary source rocks available in the Northern
Uatumã-Anauá Domain are related to the Cauarane
Group.
By combining the above, mentioned geochemi-
cal features with petrographic and other geochemical
parameters, the Serra Dourada Granite is considered as
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 81
Fig. 8. Martins Pereira and Serra Dourada Granites samples plotted on the (a) Al2O3/(FeO + MgO + TiO2) vs. Al2O3 + FeO + MgO + TiO2; (b)
( iO2; (c
A tlined fi
s phibol
P , and re
d
p
t
t
i
i
h
1
S
i
w
a
G
6
D
Na2O + K2O)/(FeO + MgO + TiO2) vs. Na2O + K2O + FeO + MgO + T
l2O3/(MgO + FeOtot) vs. molar CaO/(MgO + FeOtot) diagrams. Ou
tudies by dehydration melting of felsic pelites, metagreywackes, am
atiño-Douce, 1999; Patiño-Douce and Beard, 1996; Thompson, 1996
ominantly derived from a metagreywacke source by a
artial melting. In contrast to the Serra Dourada Granite,
he Martins Pereira granitic magma could be linked with
he partial melting of amphibolite sources, and further
nput of metagreywacke sources, either by partial melt-
ng or contamination–assimilation processes. A similar
ybrid origin was proposed by Sardinha (1999) for the
.89 Ga Igarapé Azul Granite (Almeida et al., 2002).
imilarly, an origin for high-K, calc-alkaline I-type gran-
toid rocks by partial melting of metagreywacke-sources
as also proposed by Barker et al. (1992), Altherr et
l. (2000) and Thuy Nguyen et al. (2004), in Alaska,
ermany and Vietnam, respectively.. Zircon geochronology
Five fresh granitic rocks of Northern Uatumã-Anauá
omain were sampled and analyzed by Pb-evaporation) CaO/(FeO + MgO + TiO2) vs. CaO + FeO + MgO + TiO2; (d) molar
elds denote compositions of partial melts obtained in experimental
ites–metabasalts and metatonalites sources (Wolf and Wyllie, 1994;
ferences therein). Symbols as in Fig. 3. See text for discussion.
and U–Pb ID-TIMS methods (Table 2). Three samples
from Martins Pereira Granite and one form leucogranite
lenses were analyzed by zircon Pb-evaporation, whereas
the same sample from Serra Dourada Granite was ana-
lyzed by both methods.
6.1. Martins Pereira Granite (MA-172A, 061A and
007A samples)
In the general sense, hornblende-free Martins Pereira
(meta)granitoid rocks are composed of porphyritic
coarse- to medium-grained granodiorites, monzogran-
ites and rare fine- to medium-grained (epidote)-biotite-
rich tonalites (calc-alkaline granodioritic trend in QAP
diagram), locally associated with very small lenses and
blobs of leucogranites. Three samples from the Mar-
tins Pereira Granite were analyzed by the single-zircon
Pb evaporation method (Table 2): cataclastic porphyritic
82 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Table 2
Petrography summary and geographic coordinates of analyzed samples by the single-zircon Pb-evaporation and U–Pb ID-TIMS methods
Sample code Stratigraphic unit Geog coord N Geog coord W Sample description U–Pb ID TIMS MSWD Pb-evap USD
MA-172A Martins Pereira Granite 01◦02′49′′N 59◦55′51′′W Biotite porphyritic monzogranite with – – 1975 ± 6 (6) 2.9
abundant tabular and ovoid alkalifeldspar
megacrystals. The matrix is isotropic, coarse
grained with local cataclastic texture.
MA-061A Martins Pereira Granite 01◦01′43′′N 60◦01′29′′W Biotite mylonitic granodiorite, fine- to – – 1973 ± 2 (8) 1.4
medium grained matrix with protomylonitic
to mylonitic textures and NE-SW foliation
(granolepidoblstic). Titanite and epidote are
the main accessory minerals.
MA-007A Martins Pereira Granite 00◦59′39′′N 60◦24′21′′W Biotite porphyritic metamonzogranite, – – 1971 ± 2 (4) 1.1
medium to coarse grained matrix and
accessory minerals such as epidote,
magnetite and minor apatite, titanite, allanite
and zircon. ENE-WSW foliation locally
filled by subconcordant blobs and lenses of
leucogranite.
MF-156 Serra Dourada Granite 01◦18′03′′N 54◦00′20′′W Equigranular monzogranite coarse to Upper 1962± 6 1.7 1948 ± 11 (2) 2.0
medium-grained showing aluminous
minerals such as biotite, muscovite and
locally cordierite (pinitized) and sillimanite.
Dynamic recrystallization and planar fabrics
are subordinated.
Lower 156± 30 – 2138 ± 3 (2) 0.1
MA-246C2 Blobs and lenses of 01◦11′11′′N 60◦17′38′′W White grayish, equigranular, leucogranite in – – 2354 ± 6 (1) 2.2
leucogranites lenses and pods with isotropic fabrics,
locally showing dynamic recrystalization
and cataclasis. The mineral assemblage is
composed by alkalifedspar, quartz,
plagioclase, biotite, muscovite, epidote, and
rare opaque minerals, allanite, titanite,
apatite and zircon.
– – 2134 ± 15 (3) 5.3
– – 1997 ± 8 (2) 0.1
– – 1959 ± 5 (4) 2.1
– – 1909 ± 6 (5) 4.1
Notes: In parenthesis the number of zircon analyses used to calculate the age. Key: U–Pb ID TIMS. Conventional U–Pb results, Pb-evap, Pb-evaporation results.
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 83Table 3
Zircon single-crystal Pb-evaporation isotopic data from Martins Pereira Granite (MA-172A, 061A and 007A), Serra Dourada Granite (MF-156) and lense of leucogranite (MA-246C2) samples
Sample/zircon number Temperature Ratios 204Pb/206Pb 2σ 208Pb/206Pb 2σ 207Pb/206Pb 2σ (207Pb/206Pb)c 2σ Age 2σ Th/U
(◦C)
Martins Pereira Granite—porphyritic (ovoids) biotite monzogranite
MA-172A/1 1550 8/8 0.000110 14 0.17363 181 0.12186 15 0.12186 15 1984 2 0.49
MA-172A/2 1500 34/34 0.000019 2 0.12364 21 0.12141 26 0.12119 29 1974 4 0.35
MA-172A/3 1450 30/38 0.000402 3 0.12353 30 0.12674 60 0.12094 40 1971 6 0.35
MA-172A/4 1450 20/20 0.000155 16 0.11822 39 0.12336 39 0.12089 20 1970 3 0.33
1500 34/34 0.000068 5 0.15392 19 0.12260 15 0.12169 12 1981 2 0.44
MA-172A/5 1500 36/36 0.000120 2 0.12514 28 0.12290 14 0.12131 14 1976 2 0.35
1550 16/16 0.000000 0 0.11807 95 0.12070 19 0.12070 19 1967 3 0.33
MA-172A/6 1500 30/30 0.000116 0.17099 111 0.12372 16 0.12216 21 1988 3 0.48
208 (216) USD: 2.9 Mean age 1975 6
Martins Pereira Granite—mylonitic biotite monzogranite
MA-061A/02 1550 40/40 0.000251 3 0.10772 23 0.12506 17 0.12117 36 1974 11 0.30
MA-061A/03 1450 8/8 0.000000 1 0.09694 97 0.12028 73 0.12028 73 1961 22 0.27
MA-061A/04 1450# 0/24 0.000456 44 0.10745 26 0.12590 11 0.12590 11 2042 2 0.30
1500* 0/6 0.000000 1 0.10825 112 0.12591 72 0.12590 72 2042 10 0.31
MA-061A/05 1450# 0/30 0.000647 15 0.22820 963 0.12116 23 0.12116 23 1848 21 0.65
MA-061A/06 1450 8/8 0.000052 6 0.16154 101 0.12162 15 0.12162 15 1970 6 0.46
MA-061A/07 1450 32/32 0.000085 3 0.14130 56 0.12211 15 0.12119 9 1974 3 0.40
MA-061A/09 1450 26/26 0.000267 8 0.11054 20 0.12485 17 0.12123 25 1975 7 0.31
1500* 0/8 0.000115 4 0.13236 32 0.12406 26 0.12253 27 1994 4 0.37
MA-061A/10 1450 28/28 0.000191 5 0.13814 32 0.12331 26 0.12117 33 1978 5 0.39
MA-061A/11 1450* 0/28 0.000168 6 0.11267 89 0.12126 31 0.12126 31 1941 9 0.32
MA-061A/12 1450 8/8 0.000361 26 0.21707 24 0.12526 15 0.12526 15 1963 11 0.61
1500 8/8 0.000075 1 0.19636 48 0.12124 43 0.12124 43 1960 13 0.56
MA-061A/13 1450 36/36 0.000129 1 0.16711 105 0.12264 14 0.12088 15 1969 5 0.47
1500 40/40 0.000121 2 0.23122 489 0.12259 10 0.12109 12 1973 3 0.67
1550 30/30 0.000170 13 0.15605 181 0.12312 21 0.12094 13 1970 4 0.44
264 (360) USD: 2.9 Mean age 1973 2
Martins Pereira Granite—porphyritic biotite metamonzogranite
MA-007A/01 1540 38/38 0.000071 5 0.14894 18 0.12198 34 0.12107 34 1972 5 0.42
1550 36/36 0.000082 10 0.15636 141 0.12195 66 0.12074 57 1967 8 0.43
MA-007A/02 1450* 0/34 0.000102 27 0.16074 447 0.12040 54 0.11883 89 1939 13 0.46
MA-007A/04 1500 36/36 0.000081 4 0.24268 34 0.12158 43 0.12076 30 1968 4 0.69
84 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97Table 3 (Continued)
Sample/zircon number Temperature Ratios 204Pb/206Pb 2σ 208Pb/206Pb 2σ 207Pb/206Pb 2σ (207Pb/206Pb)c 2σ Age 2σ Th/U
(◦C)
MA-007A/05 1450* 0/28 0.000098 13 0.13021 20 0.11918 27 0.11773 32 1922 5 0.37
1500 32/32 0.000045 7 0.16279 18 0.12159 39 0.12099 48 1971 7 0.46
MA-007A/06 1500 38/38 0.000030 6 0.14321 283 0.12146 22 0.12110 22 1973 3 0.41
180 (242) USD: 0.1 Mean age 1971 2
Serra Dourada Granite—muscovite-biotite monzogranite with cordierite and sillimanite
MF156/12 1450 26/34 0.000000 0 0.12405 18 0.13301 23 0.13301 23 2138 3 0.35
MF156/15 1450 36/36 0.000037 2 0.08816 21 0.13360 13 0.13299 11 2138 1 0.25
62 (70) USD: 0.1 Mean age 2138 3
MF156/06 1550 4/8 0.000078 7 0.47918 1656 0.12012 17 0.11907 19 1943 3 0.14
MF156/11 1550 6/6 0.000073 28 0.54277 132 0.12102 24 0.12004 44 1957 7 0.15
10 (14) USD: 2.0 Mean age 1948 11
Pods and lenses—leucogranite
MA-246C2/01 1500 24/24 0.000038 2 0.04358 104 0.15111 46 0.15066 52 2354 6 0.12
1550* 0/8 0.000044 2 0.04139 58 0.14857 78 0.14800 78 2323 9 0.11
24 (32) USD: 2.2 Mean age (Group I) 2354 6
MA-246C2/10 1500 36/36 0.000233 13 0.06005 30 0.13863 40 0.13533 56 2169 7 0.17
1550 8/8 0.000246 106 0.05694 47 0.13545 143 0.13254 47 2132 6 0.16
MA-246C2/14 1450 8/8 0.000423 26 0.10097 44 0.13804 694 0.13248 699 2131 92 0.28
MA-246C2/16 1500 38/38 0.000464 12 0.06177 32 0.13868 42 0.13209 31 2126 4 0.17
1550 24/32 0.000515 28 0.06177 26 0.13899 29 0.13207 60 2126 8 0.17
114 (122) USD: 5.3 Mean age (Group II) 2134 15
MA-246C2/17 1500 20/20 0.000116 102 0.05330 396 0.12487 87 0.12280 93 1998 13 0.15
MA-246C2/21 1500 34/34 0.000119 28 0.03507 14 0.12453 31 0.12273 68 1997 10 0.10
1550* 0/6 0.000000 0 0.03531 29 0.12630 148 0.12630 148 2047 21 0.10
54 (60) USD: 0.1 Mean age (Group III) 1997 8
MA-246C2/07 1500 20/20 0.000270 15 0.05075 55 0.12369 53 0.12004 56 1957 8 0.14
MA-246C2/09 1500 22/22 0.000236 9 0.10952 280 0.12285 87 0.11972 57 1952 9 0.31
MA-246C2/13 1450 8/8 0.000099 4 0.04017 313 0.12051 117 0.11918 118 1944 18 0.11
MA-246C2/23 1450* 0/14 0.000551 22 0.04188 34 0.12441 74 0.11713 57 1913 9 0.12
1500 34/34 0.000408 4 0.11232 105 0.12535 27 0.12009 21 1958 3 0.32
1550 6/6 0.000392 18 0.10542 57 0.12604 30 0.12080 39 1968 6 0.30
90 (104) USD: 2.1 Mean age (Group IV) 1959 5
M.E. Almeida et al. / Precambrian R
MA-246C2/05 1500 36/36 0.000340 28 0.06289 153 0.12044 21 0.11578 29 1892 4 0.18
1550 36/36 0.000111 45 0.04114 280 0.11986 30 0.11842 49 1933 7 0.12
1580 8/8 0.000430 20 0.06177 158 0.12252 67 0.11674 72 1907 11 0.18
MA-246C2/06 1450# 0/16 0.001815 73 0.09369 108 0.13676 209 0.10994 108 1799 18 0.27
1500 38/38 0.000413 39 0.06081 62 0.12311 27 0.11721 45 1914 7 0.17
1550 36/36 0.000398 17 0.07336 570 0.12357 31 0.11822 33 1930 5 0.21
1580 32/32 0.000455 8 0.06004 19 0.12307 41 0.11703 50 1912 8 0.17
MA-246C2/08 1450 8/8 0.000579 40 0.04980 93 0.12373 66 0.11594 86 1895 13 0.14
1480 30/30 0.000147 4 0.05632 54 0.11870 22 0.11668 16 1906 3 0.17
1500 38/38 0.000164 11 0.06134 160 0.11910 24 0.11694 19 1910 3 0.19
1550 12/12 0.000179 2 0.05614 162 0.11889 100 0.11623 61 1899 9 0.17
MA-246C2/18 1450# 0/8 0.001175 176 0.07656 957 0.12798 513 0.11209 576 1834 93 0.24
1500 16/16 0.000368 148 0.05822 30 0.12204 143 0.11686 75 1909 12 0.18
MA-246C2/19 1500 8/8 0.000590 574 0.19248 833 0.12400 688 0.11607 1043 1897 162 0.60
262 (286) USD: 4.1 Mean age (Group V) 1909 6
Notes: Crystal numbers are indicated. The column number of ratios shows the total of isotopic ratios used to the age calculation and, in parenthesis, the total isotopic ratios mea-
sured. Evaporation steps in italics were not included in the age calculation of each grain due to: (*) too much higher or lower values of the 207Pb/206Pb ratio in relation to the
average of the zircon, and (#) 204Pb/206Pb > 0.0004 (and 204Pb/206Pb > 0.0006 for the leucogranite sample). Th/U ratios calculation: Th = [(208Pb/206Pb)/(lTh×T)−1 ] + (208Pb/206Pb);
U = [(208Pb/206Pb)/(lU×T)− 1] + (208Pb/206Pb); lTh = 4.94750× 10−12; lU = 1.55125× 10−11 (in Klötzli, 1999).esearch 155 (2007) 69–97 85
monzogranite (MA-172A), mylonitic granodiorite (MA-
61A) and porphyritic metamonzogranite (MA-007A).
The sample of cataclastic coarse-grained monzogran-
ite (MA-172A) shows translucent crystals with local
opaque portions, pale brown to pale yellow colours, pris-
matic (length/width ratios between 2.9:1 and 1.8:1) and
90–400 m in length, exhibiting well-defined faces and
vertices. Mineral inclusions (such as apatite and Fe–Ti
oxides) and fractures are common. A total of 6 crystals
were analyzed yielding a mean age of 1975± 6 Ma age
(USD: 2.9) from 162 isotopic ratios (Table 3; Fig. 9a).
Individual ages of these analyses vary from 1988 to
1962 Ma.
The MA-61A mylonitic biotite granodiorite was sam-
pled along an ENE-WSW mylonitic zone to the north
of São Luiz do Anauá town. Two different zircon pop-
ulations were described in this sample: (a) prismatic
(length/width ratios between 2.4:1 and 1.6:1), translu-
cent and brown to pale brown crystals showing fractures
and rounded vertices; (b) prismatic (length/width ratios
between 3.8:1 and 2:1), transparent, pale yellow crys-
tals showing few fractures and vertices, and well-defined
faces. Both zircon populations showed scarce mineral
inclusions, crystals with 140–360 m in length and
local irregular internal zoning, this last observation
suggesting igneous overgrowth and/or older inherited
cores. The mean age of analyses of 8 crystals (264
isotopic ratios) from both populations by the Pb-
evaporation method yielded 1973± 2 Ma (USD: 2.1)
(Table 3; Fig. 9b), exhibiting individual ages vary-
ing of 1978–1962 Ma. Anomalous ages were observed
in crystals #4 (2042± 20 Ma, 1450 and 1500 ◦C step-
heatings) and #9 (1994± 4 Ma, 1500 ◦C step-heating),
which could represent inherited components.
The sample of the porphyritic metamonzogranite
facies (MA-007A) selected for dating is locally foli-
ated and banded. The zircon crystals are pale brown,
transparent to translucent, prismatic and bypiramidal,
with 190–450 m in length (3.5:1 to 2.2:1 length/width
ratios). They show fractures, sometimes radial-like,
well-defined faces and rounded vertices. Inclusions are
very rare in these zircon samples. A total of four crys-
tals were analyzed yielding individual ages varying from
1973 Ma to 1967 Ma, and a mean age of 1971± 2 Ma
age (Table 3; Fig. 9c). The 25 blocks and 180 isotopic
ratios show a very homogeneous pattern, yielding a well-
defined mean age with good statistical level (USD: 1.1).
The results obtained from Martins Pereira Granite
show a small interval age (1980–1968 Ma) and local 1.99
and 2.04 Ga inheritances, these last probably related to
the Anauá Complex. Other granitoid rocks from Mar-
tins Pereira Granite area, and equivocally related to
86 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Fig. 9. Single-zircon Pb-evaporation ages for Martins Pereira Granite samples: (a) MA-172A (cataclastic porphyritic monzogranite), (b) MA-061A
monzog
207Pb/2
e scale(mylonitic granodiorite) and (c) MA-007A (foliated porphyritic meta
square—blocks not used due to their higher or lower values of the
204Pb/206Pb > 0.0004. Crystal numbers are indicated (see Table 3). Th
Água Branca Suite and Igarapé Azul Granite, were
dated by Almeida et al. (1997) and CPRM (2003) yield-
ing 1960± 21 and 1972± 8 Ma, respectively (Table 5).
These ages are in agreement with the results obtained
in this paper (see Fig. 9a–c) and mark an important
magmatic event in southeastern Roraima, here named
as Rorainópolis event. In general sense, these results are
uniform, homogeneous and establish a 1.97–1.96 Ga age
range, despite the observed heterogeneous textures (e.g.
igneous, mylonitic and cataclastic), different geograph-
ical site sampling, and different applied methodologies
(Tables 2 and 5; Fig. 2).
6.2. Serra dourada granite (MF-156 samples)
The S-type granitoid rocks in southeastern Roraima
State were initially described by Faria et al. (1999) and
incorporated into the Igarapé Azul Granite. However,
Almeida et al. (2002) subdivided the Igarapé Azul Gran-
ite into three different types: Serra Dourada Granite (trueranite). Symbols: filled circle—accepted blocks for age calculation;
06Pb ratio in relation to the mean; ×—rejected blocks due to show
bar is the same for all diagrams.
S-type), Martins Pereira Granite (I-type high-K calc-
alkaline) and the proper Igarapé Azul Granite (I-type
felsic high-K calc-alkaline).
A syenogranite sample of Serra Dourada Gran-
ite (MF-156) with biotite, muscovite and cordierite
(Table 2), including monazite and xenotime as accessory
minerals, was analyzed by single-zircon Pb-evaporation
method. This sample shows two zircon populations with
different features. The first group is scarce and shows
rounded vertices, irregular faces (corrosion?), light yel-
low colour, 310–500 m in length (length/width ratios
between 2.3:1 and 1.5:1), translucent to transparent
opacity, and is generally free of inclusions. The second
type of zircon shows crystals with slightly rounded ver-
tices, is light brown to brown, 170–340 m in length
(length/width ratios between 3.1:1 and 1.5:1), transpar-
ent and locally with few inclusions and fractures. This
second type of zircon is characterized by well-developed
{2 1 1} pyramid, similar to zircon crystallized from per-
aluminous melt (Pupin, 1980).
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 87
F 6) yield
m : filled
d .
y
a
T
b
w
t
a
w
e
p
i
a
s
i
m
t
(
D
U
a
S
l
(
m
(
c
O
C
b
d
ig. 10. Single-zircon ages for Serra Dourada Granite (sample MF-15
ethods. Crystal numbers are indicated (see Tables 3 and 4). Symbols
ue to too low value of the 207Pb/206Pb ratio in relation to the average
In the Pb-evaporation method, the zircon fractions
ielded two different age patterns, irrespective of the few
nalyzed grains and isotopic ratios obtained (Table 3).
he lower age (1948± 11 Ma) was obtained from two
locks from two crystals. The higher age (2138± 3 Ma)
as obtained from nine blocks of isotopic ratios from
wo zircon crystals (Fig. 10a), and is interpreted as an
ge of inherited origin.
U–Pb ID-TIMS was carried out on the same sample
ith the aim of interpreting the ages obtained by the Pb-
vaporation method. The regression of four experimental
oints yields a discordia line which indicates an upper
ntercept at 1962± 2 Ma (Table 4; Fig. 10b), interpreted
s the crystallization age of the analyzed crystals and,
imilarly, that of the Serra Dourada Granite. This age
s very close to the age yielded with the Pb-evaporation
ethod for the same sample which, taking into account
he errors, almost overlap one another.
The geological similarities between Serra Dourada
Uatumã-Anauá Domain) and Taiano (Central Guyana
omain) S-type granites are also pointed out by our
–Pb and Pb-evaporation zircon ages. The Taiano
natetic leucogranite yields 1969± 3.5 Ma (zircon U–Pb
HRIMP, CPRM, 2003) and the minimum crystal-
ization age yielded by single-zircon Pb-evaporation
1948± 11 Ma) and U–Pb ID-TIMS (1962 + 2/−6 Ma)
ethods for the Serra Dourada type are quite similar
Table 5), confirming an important anatetic process in the
entral-southern Roraima State occurred 1.97–1.96 Ga.
ther S-type granitoid rocks in the Roraima, such as
uruxuim and Amajari granites (CPRM, 1999), could
e related also to this same event, however they are not
ated yet.ed by (a) Pb-evaporation and (b) U–Pb ID-TIMS (concordia diagram)
circle—accepted blocks for age calculation; square—blocks not used
The inherited ages in both S-type granites also
show Eo- to Neo-Transamazonian ages, ranging from
2138± 3 Ma (Serra Dourada Granite) to 2047± 7 and
2072± 3 Ma (Taiano Granite), probably related to
sedimentary contribution. This hypothesis is partially
confirmed by Transamazonian detrital zircon crystals
detected in the metavolcanosedimentary rocks from the
Cauarane Group (Table 6), from which two paragneiss
samples were dated by U–Pb ID-TIMS (2223± 19 Ma,
Gaudette et al., 1996) and U–Pb SHRIMP (2038± 17
and 2093± 62 Ma, CPRM, 2003) methods.
6.3. Leucogranite (MA-246C2 sample)
Leucosyenogranite lens sample (MA-246C2) associ-
ated with Martins Pereira (meta)granitoid rocks showed
a complex set of results. All zircons were analysed based
on 2 sigma = 0.0006, because 2 sigm = 0.0004 yielded
ages with higher USD values and errors, although the
results are not so different. For instance, the younger
zircon population yielded by 2 sigma 0.0006 and
0.0004, 19094± 6 Ma (USD = 4.1) and 19094± 7 Ma
(USD = 4.7), respectively. Five groups of zircon occur in
this sample in decreasing age order (Table 5; Fig. 11a
and b).
Group I is represented by only one pale brown, trans-
parent to translucent zircon grain with 265 m in length
(length/width ratio 1.9:1), showing regular internal zon-
ing, well-defined faces and dark inclusions in the core.
It yielded an age of 2354± 6 Ma (crystal #1).
Group II exhibits pale yellow and transparent grains
(locally translucent to opaque) being 250-330 m in
length (length/width ratios between 3.2:1 and 2.5:1).
88 M.E. Almeida et al. / Precambrian
(
Table 4
U–Pb isotopic zircon data (ID-TIMS) from Serra Dourada granitoid (sample MF-156)
Sample Concentrations Atomic ratios Ages (Ma)
Zircon Weight ppm U ppm Pb 206Pb/04Pbc1 %err 207Pb*/235Uc2 %err 206Pb*/238Uc2 %err 207Pb*/206Pb*c2 %err 206Pb*/238U 207Pb*/235U 207Pb*/206Pb* Concordantd (%)
number (mg)
MF-156-1 0.144 35.20 12.33 129.714 1.040 543.181 0.225 0.328881 0.079 0.119786 0.204 1833 1890 1953 94
MF-156-2 0.304 12.16 4.42 818.679 0.459 547.834 0.152 0.331237 0.118 0.119952 0.088 1844 1897 1956 94
MF-156-4 0.213 18.01 5.29 683.428 0.366 436.517 0.324 0.266823 0.223 0.118652 0.234 1525 1706 1936 79
MF-156-5 0.166 34.19 12.01 233.930 0.793 553.956 0.354 0.334560 0.347 0.120088 0.068 1860 1907 1958 95
MF-156-6 0.770 5.51 1.90 816.957 0.700 536.251 0.457 0.326122 0.394 0.119258 0.231 1820 1879 1945 94
Notes:Maximum total blanks for zircon analyses are 10 pg for Pb and 2 pg for U. Stacey and Kramers (1975) values were used. c1: measure ratios corrected for mass fractionation; c2: ratios corrected
for spike, fractionation, blank and initial common Pb following Stacey and Kramers (1975) model. Erros are at 2 s; d: concordance in relation to concordia curve: 100t(206Pb/238U)/t(207Pb/206Pb).Research 155 (2007) 69–97
Cracks are common, but inclusions are rare. This group
comprises three zircon crystals with individual ages
varying from 2148 to 2126 Ma, and yielded a mean age
of 2134± 15 Ma (crystals #10, 14 and 16).
Group III encompasses colorless to pale yellow crys-
tals which are 166–180 m in length (length/width ratios
around 2.7:1), with crystals locally exhibiting inter-
nal zoning and cracks in the core. This group yielded
1997± 8 Ma as a mean age (crystals #17 and 21).
In general, zircon crystals of the group IV are
characterized by brown to pale brown and translu-
cent grains with well-defined faces (locally broken)
and 210–260 m in length (length/width ratios around
2.6:1). This group consists of four crystals with individ-
ual ages varying from 1968 to 1952 Ma, and yielded a
mean age of 1959± 5 Ma (crystals #7, 9, 13 and 23).
Zircon crystals of the group V are 164–330 m in
length (length/width ratios between 3.1:1 and 1.8:1), are
pale yellow to pale brown in colour, transparent and
show local cracks and inclusions. This group displays
a mean age of 1909± 6 Ma from five crystals (#5, 6,
8, 18 and 19), with individual ages varying from 1933
to 1892 Ma. This lowest age (group V) is interpreted as
the crystallization age, whereas the higher ages (groups
I–IV) probably represent inherited zircon of different ori-
gins. However, this crystallization age may have, at least
locally, grains with igneous border and older cores, sug-
gesting partial contribution of isotopic content of older
events (e.g. crystals #5 and 6).
Despite the wide variety of zircon populations from
sample MA246C2, including grains with internal com-
plexity or zoning (“mixing age”) or partial resetting,
the results obtained by the single-zircon Pb-evaporation
method allow for the following interpretation:
(a) The 1909± 6 Ma (group V) is interpreted as the
minimum crystallization age of leucosyenogranite.
Other ages, around 1.89–1.90 Ga, which are related
to Igarapé Azul and Água Branca granitoids (e.g.
CPRM, 2003; Almeida et al., 2002) are described in
this region, mainly in the southern Uatumã-Anauá
Domain. These leucogranitic lenses also show some
petrographic similarities with Igarapé Azul granitoid
rocks and were both likely generated in the same
magmatic event.
b) The 1997± 8 Ma (group III) and 1959± 5 Ma
(group IV) ages probably correspond to inher-
ited components from the Surumu volcanics and
Martins Pereira (meta)granitoid rocks (or Urubu
orthogneisses?), respectively, however the former
are not exposed in the Uatumã-Anauá Domain and
correlated igneous rocks are not found there.
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 89
Table 5
Summary of new and previous Pb–Pb and U–Pb (ID-TIMS and SHRIMP) ages yielded by zircon from volcano-plutonic rocks older than 1900 Ma
of the Ventuari-Tapajós (or Tapajós-Parima) Province
Symbol Reference Rock type Lithostratigraphic unit Age (Ma) Reference Method
number
Central Guyana Domain
CG1 1 Hornblende-biotite gneiss Rio Urubu “A-type” gneisses 1935 ± 5 Fraga (2002) B
with titanite (Miracélia
Gneiss)
2 Hornblende-biotite gneiss Rio Urubu “A-type” gneisses 1937 ± 5 Fraga (2002) B
with allanite (Igarapé Branco
Gneiss)
CG2 3 Quartz jotunite Serra da Prata C-type 1933 ± 2 Fraga et al. (2003) B
4 Clinopyroxene porphyrytic Serra da Prata C-type 1934 ± 1 Fraga et al. (2003) B
charnockite
5 Hypersthene quartz syenite Serra da Prata C-type 1934 ± 3 Fraga et al. (2003) B
6 Clinopyroxene porphyrytic Serra da Prata C-type 1936 ± 4 Fraga et al. (2003) B
charnockite
7 Charnockite Serra da Prata C-type 1943 ± 5 Fraga et al. (2003) B
hydrothermalized
8 Quartz jotunite gneiss Serra da Prata C-type 1966 ± 37 Fraga et al. (1997) A
CG3 9 Vilhena Mylonite Rio Urubu “I-type” gneisses 1932 ± 10 CPRM (2003) D
10 Mucajaı́ Metagranite Rio Urubu “I-type” gneisses 1938 ± 9 CPRM (2003) D
11 Granitic gneiss Rio Urubu “I-type” gneisses 1943 ± 7 Gaudette et al. (1996) C
12 Granitic gneiss Rio Urubu “I-type” gneisses 1944 ± 10 Santos and Olszewski C
(1988)
13 Tonalite orthogneiss Rio Urubu “I-type” gneisses 1951 ± 24 Fraga et al. (1997) A
CG4 14 S-type leucogranite Taiano S-type 1969 ± 4 CPRM (2003) D
Surumu Domain
S1 15 Tabaco Mountain Dacite Surumu Group 1966 ± 9 Schobbenhaus et al. C
(1994)
16 Tabaco Mountain Dacite Surumu Group 1977 ± 8 Schobbenhaus et al. C
(1994) mod. by
CPRM (2003)
17 Uraricáa Rhyodacite Surumu Group 1984 ± 7 Santos et al. (2003b) D
18 Cavalo Mountain Rhyodacite Surumu Group 2006 ± 4 Costa et al. (2001) B
S2 19 Orocaima Granodiorite Pedra Pintada Suite 1956 ± 5 CPRM (2003) D
20 Pedra Pintada Monzogranite Pedra Pintada Suite 2005 ± 45 Almeida et al. (1997) A
Parima Domain
P1 21 Prainha meta-andesite Parima Group 1948 ± 6 Santos et al. (2003c) D
Uatumã-Anauá Domain
UA1 22 Leucosyenogranite Blobs and lenses of 1909 ± 9 This paper B
(ma246c2) leucogranite
UA2 23 Monzogranite (mf156) S-type Serra Dourada 1948 ± 11 This paper B
24 Monzogranite (mf156) S-type Serra Dourada 1962 ± 6 This paper C
25 Metamonzogranite Martins Pereira Granite 1938 ± 17 Almeida et al. (1997) A
UA3 26 Metamonzogranite Martins Pereira Granite 1960 ± 21 Almeida et al. (1997) A
27 Metamonzogranite Martins Pereira Granite 1972 ± 7 CPRM (2003) C
28 Metamonzogranite (ma007a) Martins Pereira Granite 1971 ± 2 This paper B
29 Mylonitic monzogranite Martins Pereira Granite 1973 ± 2 This paper B
(ma061a)
30 Monzogranite (ma172a) Martins Pereira Granite 1975 ± 6 This paper B
UA4 31 Metatonalite Anauá Complex 2028 ± 9 Faria et al. (2002) D
90 M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97
Table 5 (Continued)
Symbol Reference Rock type Lithostratigraphic unit Age (Ma) Reference Method
number
Tapajós Domain
T1 32 Granite Creporizão Suite 1957 ± 6 Santos et al. (2000) C
33 Creporizão Monzogranite Creporizão Suite 1963 ± 6 Santos et al. (2001) D
34 JL Monzogranite Creporizão Suite 1966 ± 5 Santos et al. (2001) D
35 Joel Monzogranite Creporizão Suite 1968 ± 7 Santos et al. (2004) D
36 km130 Monzogranite Creporizão Suite 1968 ± 16 CPRM (2000b) B
37 Ouro Roxo Metandesite II Creporizão Suite 1974 ± 6 Santos et al. (2001) D
T2 38 Biotite leucomonzogranite Old São Jorge Granite 1981 ± 2 Lamarão et al. (2002) B
39 Hornblende-biotite Old São Jorge Granite 1983 ± 8 Lamarão et al. (2002) B
monzogranite
40 Granite Old São Jorge Granite 1984 ± 1 CPRM (2000b) B
T3 41 Trachyte Vila Riozinho Volcanics 1998 ± 3 Lamarão et al. (2002) B
42 Trachyte Vila Riozinho Volcanics 2000 ± 4 Lamarão et al. (2002) B
T4 43 Rio Claro Monzogranite – 1997 ± 3 CPRM (2000b) B
44 Jamanxim Rapakivi – 1997 ± 5 Santos et al. (1997) C
Monzogranite
T5 45 Cabruá Tonalite Cuiú-Cuiú Complex 2005 ± 7 Santos et al. (2001) D
46 Conceição Tonalite Cuiú-Cuiú Complex 2006 ± 3 Santos et al. (1997, C
2004)
47 Ouro Roxo Andesite Cuiú-Cuiú Complex 2012 ± 8 Santos et al. (2001) D
48 JL Tonalite Cuiú-Cuiú Complex 2015 ± 9 Santos et al. (2001) D
49 Amana Monzogranite Cuiú-Cuiú Complex 2020 ± 12 Santos et al. (2001) D
50 Cuiú-Cuiú Meta-tonalite Cuiú-Cuiú Complex 2033 ± 7 Santos et al. (2001) D
Notes: (A) Pb-evaporation on single filament; (B) Pb-evaporation on double filament; (C) U–Pb ID-TIMS; (D) U–Pb SHRIMP. Reference number
1–50 and symbols GC1-T5 are the same as in Fig. 12.
Fig. 11. Single-zircon Pb-evaporation ages of lenses of leucogranite in association with Martins Pereira Granite. (a) Inherited ages: (I) pre-
Transamazonian (Siderian); (II) Transamazonian; (III) Late-Transamazonian (Anauá Complex?); (IV) Martins Pereira, and (b) (V) minimum
crystallization age. Symbols: filled circle—accepted blocks for age calculation; square—blocks discarded due their higher or lower values of the
207Pb/206Pb ratio in relation to the mean; ×—rejected blocks due to 204Pb/206Pb > 0.0006. Crystal numbers are indicated (see Table 3). The scale
bar is the same for all diagrams.
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 91
Table 6
Summary of ages and possible sources of the inherited zircons from volcano-plutonic and (meta)sedimentary rocks older than 1900 Ma of the
Ventuari-Tapajós (or Tapajós-Parima) Province
Domain Reference Rock type Lithostratigraphic Age (Ma) Interpretation Reference Method
number Unit
Central Guyana Domain
CG4 14 Leucogranite S-type Taiano Granite 2047 ± 7 Late-Transamazonian CPRM (2003) D
2072 ± 3
– Taiano Paragneiss Cauarane Group 2038 ± 17 Late-Transamazonian CPRM (2003) D
2074 ± 15
2223 ± 19 Early-Transamanzonian Gaudette et al. C
(1996)
CG3 9 Vilhena Mylonite Rio Urubu “I-type” 2145 ± 5 Early-Transamanzonian CPRM (2003) D
gneisses
Surumu Domain
– Uiramutã Quartz Arai Formation 1958 ± 19 Pedra Pintada/Surumu Santos et al. D
sandstone (Roraima Supergroup) (2003b)
2123 ± 14 Early-Transamanzonian
2718 ± 18 Archean
S1 17 Uraricáa Rhyodacite Surumu Group 2027 ± 32 Late-Transamazonian Santos (2002) D
16 Surumu Rhyodacite Surumu Group 2163 ± 10 Early-Transamanzonian
Parima Domain
P – Uatatás Quartzite Parima Group 1971 ± 9 Pedra Pintada/Surumu Santos et al. D
(2003c)
2098 ± 16 Late-Transamazonian
2201 ± 10 Early-Transamanzonian
2781 ± 6 Archean
2872 ± 6 Archean
Uatumã-Anauá Domain
UA2 23 S-type monzogranite S-type Serra Dourada 2138 ± 11 Early-Transamanzonian This paper B
(mf156) Granite
UA1 22 Leucogranite Blobs and lenses of 1959 ± 5 Martins Pereira This paper B
(MA246C2) leucogranite
1997 ± 8 Anauá?
2128 ± 3 Early-Transamanzonian
2354 ± 6 Siderian
Tapajós Domain
T1 34 JL Monzogranite Creporizão Suite 2003 ± 5 Cuiú-Cuiú Santos et al. D
(2001)
T3 41 Trachyte Vila Riozinho 2852 ± 4 Archean Lamarão et al. B
Volcanic Rocks (2002)
2591 ± 3 Late Archean
T5 47 Ouro Roxo Andesite Cuiú-Cuiú Complex 2040 ± 5 Late-Transamazonian Santos et al. D
(2001)
50 Cuiú-Cuiú Cuiú-Cuiú Complex 2056 ± 7 Late-Transamazonian
Meta-tonalite
48 JL Tonalite Cuiú-Cuiú Complex 2046 ± 5 Late-Transamazonian
2100 ± 7 Early-Transamanzonian
2380 ± 8 Siderian
N ouble fi
1
(
otes: (A) Pb-evaporation on single filament; (B) Pb-evaporation on d
–50 and symbols GC1-T5 are the same as in Fig. 12.c) The 2354± 6 Ma (Siderian, group I) and
2134± 15 Ma (Sthaterian, group II) ages suggest
local inheritance from older crust (not outcropping),
respectively related to the pre-Transamazonian and2483 ± 19 Siderian
lament; (C) U–Pb ID-TIMS; (D) U–Pb SHRIMP. Reference numberTransamazonian magmatic events. Transamazonian
rocks with 2.26–2.01 Ga (Santos et al., 2003a)
have been described ∼600 km northeast from
the sampled site, in the Maroni-Itacaiúnas or
brian92 M.E. Almeida et al. / Precam
Transamazon Province (Fig. 1). Transamazonian
rocks mainly occur in Brazil (Amapá State; Avelar
et al., 2001; Rosa-Costa et al., 2003), French
Guyana (Vanderhaeghe et al., 1998; Delor et al.,
2003), São Luis Craton (Klein and Moura, 2001)
and (its extension) in the West Africa craton (Boher
et al., 1992; Milési et al., 1992; Gasquet et al.,
2003). In the last case, they are related to Birimian
(2185–2150 Ma) and Bandamian (2115–2100 Ma)
events.
In West Africa, pre-Birimian ages (Burkinian, accord-
ing to Lemoine et al., 1990) are described by Gasquet et
al. (2003) in Dabakala (Ivory Coast). The 2312± 17 Ma
age has seen two interpretations by the previously men-
tioned authors. The first interpretation considers this age
representing an Archean inheritance (and not Siderian)
based on the complex model of Pb loss in the ana-
lyzed zircon crystals. The second interpretation holds
that this age is related to the ca. 2.3 Ga pre-Birimian
crust. According to these authors, the second hypothesis
is more consistent due to the systematically well-defined
age patterns, around 2.2–2.3 Ga (without evidence of
older Archean ages). This second hypothesis gains addi-
tional support from the fact that these rocks are not
spatially close to the Archean nucleus.
The Siderian age in Uatumã-Anauá Domain (Tapajós-
Parima Province) is the first zircon data reported in any
section of the central-western Guyana Shield and suggest
probably contamination-assimilation of older country
rocks with pre-Transamazonian and post-Archean ages,
not exposed in surface. The proximity with Central
Amazonian Province (older than 2.3 Ga) is uncertain,
because provincial boundaries are not precise. Although
Siderian-Neoarchean Nd model ages are describe in the
central Guyana Shield (e.g. Faria et al., 2002; Costa,
2005), this province remains poorly investigated, while
U–Pb and Pb–Pb geochronological data are scarce,
showing ages systematically lower than 2.3 Ga.
Other Siderian ages have been found in the Amazo-
nian Craton, but not in the Guyana Shield. Additionally,
the Siderian age (2354 Ma) in Uatumã-Anauá is lower
than the Siderian inheritance (2380–2483 Ma) obtained
by Santos et al. (2001) in Cuiú-Cuiú rocks from the
Tapajós Domain (Brazil Central Shield). Other Side-
rian ages are reported in the Transamazonian terrane
(2.20–1.99 Ga, Vasquez et al., 2003) of Bacajá domain
(to north–northwest of Carajás Province) where zircon
dating from Vasquez et al. (2003), Santos et al. (in
Faraco et al., 2003), and Macambira et al. (2004) yielded
2.44–2.30, 2.47–2.31 and 2.36 Ga, respectively.Research 155 (2007) 69–97
7. Tapajós and Uatumã-Anauá domains:
chronostratigraphy and implications for
geological evolution of the Tapajós-Parima or
Ventuari-Tapajós provinces
Previous and new geochronological data have shown
several similarities among granitoid rocks from the
Northern Uatumã-Anauá Domain and Tapajós Domain
(orogenic subdomain, CPRM, 2000b) (Tables 5 and 6).
The Orosirian primitive arc inliers, for example, are rep-
resented by the Anauá Northern Uatumã-Anauá Domain
and Cuiú-Cuiú (Tapajós) TTG-like complexes and are
the oldest rocks outcropping in these regions.
In Northern Uatumã-Anauá Domain, the Anauá
Tonalite is 2028± 9 Ma old (Table 5; Fig. 12), but does
not have inheritance evidence and shows Nd of −0.20.
This is interpreted as being of juvenile origin (Faria
et al., 2002), although only one sample had been ana-
lyzed. The Cuiú–Cuiú Complex of the Tapajós Domain
shows an age range of 2033–2005 Ma and the older
types are coeval to the Anauá granitoid rocks from the
Northern Uatumã-Anauá Domain (Table 5; Fig. 12). In
contrast to Anauá types, the Cuiú–Cuiú Complex yields
several inherited zircon components (Table 6; Fig. 12),
in which, the main inheritance is from Transamazo-
nian (2040–2100 Ma), with minor Siderian to Archean
records (2380–2483 Ma).
The well-defined interval age of Martins Pereira
Granite (1980–1969 Ma) in the Northern Uatumã-Anauá
Domain is also very similar to that shown by the
Creporizão Suite (1980–1951 Ma) from the Tapajós
Domain (Table 5; Fig. 12; CPRM, 2000b; Santos et
al., 2000, 2001). Similarly, the Old São Jorge Granite
(Lamarão et al., 2002) of the Tapajós Domain is c. 10 Ma
older than the Creporizão Suite, but both high-K calc-
alkaline granites are related to the Creporizão Orogeny
(1.98–1.96 Ga), according to Santos et al. (2004). The
Pedra Pintada granitoid rocks (Fraga et al., 1996) in
the Surumu Domain (Orocaima event, Reis et al., 2000)
are also probably coeval (1958 Ma, CPRM, 2003) to the
calc-alkaline Martins Pereira Granite.
In Northern Uatumã-Anauá Domain, lenses of
leucosyenogranite are ∼70 m.y. younger than the Mar-
tins Pereira host-rock and show crystallization age
(1906± 4 Ma) similar to those of the Igarapé Azul-
Caroebe granitoid rocks (Água Branca magmatism:
1906–1885 Ma) describe in the Southern Uatumã-
Anauá Domain. Some similar inherited ages are also
observed in both granitic types, such as Martins Pereira
(meta)granitoid rocks and Transamazonian inheritances
(Table 6), whereas Siderian inheritance is restrict to the
leucogranites. The same 1.90–1.88 Ga age interval cor-
M.E. Almeida et al. / Precambrian Research 155 (2007) 69–97 93
F Ma of V
d nauá; T
r
t
g
g
t
T
n
s
(
v
m
w
8
a
(
t
ig. 12. Temporal distribution of main magmatic rocks older than 1900
omains: CG, Central Guyana; S, Surumu; P, Parima; UA, Uatumã-A
esponds also to the Tropas and Parauari magmatism, in
he Tapajós Domain (Table 5).
In contrast with Roraima region – where the S-type
ranites (e.g. Serra Dourada, Curuxuim and Amajari),
ranulites (e.g. Barauana) and charnockites are rela-
ively common – these rock types are scarce in the
apajós Domain. They are locally described as small gar-
et leucogranite bodies (not mapped on the 1:250,000
cale) associated with Cuiú-Cuiú metagranitoid rocks
Almeida et al., 2001) and have not been dated pre-
iously. The scarcity of S-type granites and granulite
etamorphism suggests that the collisional processes
ere less intense in the Tapajós Domain.
. ConclusionsGeological, geochronological and geochemical data (
vailable for granitoid rocks from southeastern Roraima
Brazil) suggest Paleoproterozoic evolution in at least
wo stages: the Anauá orogeny is related to 2.03 Gaentuari-Tapajós (or Parima-Tapajós) Province, grouped by geological
, Tapajós.
TTG granitoid rocks (accretionary phase generating the
Anauá granitoid rocks and Cauarane metavolcanosed-
imentary cover), followed by crustal thickening and
anatexis around 1.97–1.96 Ga (collisional phase gener-
ating Martins Pereira and Serra Dourada granites). A
juvenile origin is envisaged for Anauá rocks, but scarce
Nd isotopic data do not make this hypothesis conclusive.
The Northern Uatumã-Anauá Domain crust, character-
ized by Orosirian granitoid rocks, is mainly thought to
have been generated by reworking of older Transama-
zonian and minor Siderian crust, according to inherited
zircon records.
The following magmatic events can be listed as had
occurred for the Northern Uatumã-Anauá Domain:A) 2.03 Ga—Crystallization of Anauá Tonalite within
the TTG association, representing a primitive arc
(?) in southeastern Roraima with related back arc
basins.
brian
(
94 M.E. Almeida et al. / Precam
(B) 1.97–1.96 Ga—Martins Pereira high-K calc-
alkaline (meta)granitoid rocks and Serra Dourada
S-type granite showing similar crystallization
ages. These rocks are probably related to crustal
thickening and anatexis in the latest (or after) stage
of Anauá arc evolution.
(C) ca. 1.90 Ga—meter to centimeter scale leucogranite
blobs and lenses (low degree of partial melt-
ing?). It is thought that these pods in-filled
older, planar structures in the Martins Pereira
(meta)granitoid rocks. A regional-scale magmatic
event (1.90–1.89 Ga) is mentioned in the south-
ern Uatumã-Anauá Domain, and is believed to be
related to the Igarapé Azul and Água Branca gran-
itoid rocks and coeval volcanism (Almeida et al.,
2002; Almeida and Macambira, 2003).
Furthermore, possibly two main periods are also
recorded in inherited zircon:
A) Siderian (2.35 Ga)—only one zircon crystal with
this age was detected in the lenses of leucogran-
ite, but it represents the first indication of Siderian
crust (host-rock or material source) in the cen-
tral Guyana Shield. Alternatively, this Siderian age
could be the result of an isotopic mixing between
“Transamazonic” and “Archean” components of the
same zircon or partial resetting of an older grain.
On the other hand, similar ages are also recorded in
West Africa craton (2312 Ma, Gasquet et al., 2003),
Bacajá (2359± 3 Ma, Macambira et al., 2004) and
Tapajós domains (2483–2380 Ma, Santos et al.,
2001) in Amazonian craton.
(B) Rhyacian (2.14–2.13 Ga, Transamazonian event)—
this age interval is yielded by the oldest zircon
crystals from the Serra Dourada S-type granite
(two crystals) and group II from the lenses of
leucogranite (three crystals). Similar inheritance
(2163–2100 Ma) was observed in Surumu, Central
Guyana and Tapajós domains (CPRM, 2003; Santos
et al., 2001, 2003b).
Neoarchean inheritance is not recorded in the North-
ern Uatumã-Anauá Domain, but is recorded locally
in other domains of Tapajós-Parima Province, such as
Tapajós (2852–2591 Ma, Lamarão et al., 2002) and
Parima (2872–2781 Ma, Santos et al., 2003c) domains.
Previous studies have recognized three geochrono-
logical provinces in southeastern Roraima, but new
geological, geochronological and geochemical data pre-
sented here shows that this region is very similar to the
Tapajós Domain (Santos et al., 2004) and reinforce theResearch 155 (2007) 69–97
Ventuari-Tapajós or Parima-Tapajós provinces prolon-
gation in southeastern Roraima, taking into account that
rocks older than 2.03 Ga are not exposed in the studied
region. However, the Central Amazonian and Maroni-
Itacaiúnas provinces seem to be important crustal
sources for the rocks of the Northern Uatumã-Anauá
Domain, suggesting partial or total crustal recycling.
In summary, the I-type high-K calc-alkaline Martins
Pereira (meta)granitoid rocks and S-type Serra Dourada
granites were generated in the Northern Uatumã-
Anauá Domain (Ventuari-Tapajós or Tapajós-Parima
provinces), probably during amalgamation of TTG-
like Anauá magmatic arc (2028 Ma) with Transamazon
(2.2–2.0 Ga) and Central Amazonian (older than 2.3 Ga)
terranes.
Some authors argue that most collision orogenic sys-
tems have a prior accretion history (e.g. Van Staal et al.,
1998), so it is easy to confuse the accretion and collision
histories in ancient examples, such as the Ventuari-
Tapajós or Tapajós-Parima provinces. This makes it
difficult to rebuild the Anauá orogeny and the hypothe-
sis presented in this paper is only a first approach of the
tectonic evolution of the central portion of the Guyana
Shield.
Acknowledgments
Special thanks to the colleagues of CPRM (Geologi-
cal Survey of Brazil) and Sérgio C. Valente (UFRuRJ),
Claúdio M. Valeriano (UERJ), Cândido A.V. Moura
and Claúdio N. Lamarão (UFPA) for discussions and
Nicholas Tailby (Australian National University) for the
English review. The authors are also grateful to CPRM-
Geological Survey of Brazil for the research grants and
FINEP (CT-Mineral 01/2001 Project) and Isotope Geol-
ogy Laboratory of Federal University of Pará for support
of laboratorial work. Thanks also to the two anonymous
referees for suggestions to the manuscript.
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