Geological mapping performed in the eastern portion of the Transition Subdomain,
Carajás Province, southern of Canaã dos Carajás and the northern of Sapucaia cities, allowed
the identification, individualization and characterization of a variety of Archean rocks,
previously encompassed in the Xingu Complex. The oldest unit identified in this area is a
hornblende tonalite, correlated to São Carlos Tonalite (~2.93 Ga), which is exposed as blocks
or outcrop and commonly present foliation (NW-SE to E-W) or homogeneous aspect. Its
geochemical signatures differ from the typical Archean tonalite-trondhjemite-granodiorite
(TTG) associations due to show enrichment in TiO2, MgO and CaO, low contents of Sr, and
Rb contents similar to samples with lower concentrations of silica, which are reflected in
higher Rb/Sr ratios and lower Sr/Ba ratios. The REE patterns reveal low to moderate
fractionation of HREE compared to LREE, and discrete or moderate negative Eu anomalies. It
is stratigraphycally followed by TTG association correlated to Colorado Trondhjemite (~2.87
Ga) which displays gray color, medium-grained, and commonly a NW-SE to E-W foliation.
In the southern of area, outcrops a body of 40 km 2, which comprises a small mountain of
porphyritic leucogranodioritic rocks named Pantanal Leucogranodiorite . It is emplaced at
TTG association and crosscutted, on its western portion, by deformed leucogranites. The
Pantanal Leucogranodiorite shows peraluminous character and calc-alkaline affinity, with
high contents of Ba and Sr. The REE patterns show nosignificant Eu anomalies and HREE are
strongly fractionated, which is geochemically similar to Guarantã Suite (~2.87 Ga) from the
Rio Maria Domain. Its origin may be related to low degrees of melting of TTG, probably
accompanied by interaction with fluids enriched in K, Ba and Sr, derived from a
metasomatized mantle. The leucogranites exhibit A-type geochemical signature and reduced
character, and may have originated from the melt of dehydrated peraluminous calcic-alkaline
rocks, during the Neoarchean. In the eastern portion of the Pantanal Leucogranodiorite was
also identified ahornblende-biotite monzogranite which is geochemically similar to oxidized
A-type granites, correlated to Neoarchean Vila Jussara Suite. Also, it correlated to
Neoarchean subalkaline magmatism in the northern area, occur two granitic stocks. They
comprise (i) tonalite to granodiorite with geochemical signature similar to oxidized A-type
granites and show affinity with Vila Jussara Suite; and (ii) monzogranites which show
reduced A-type granites signature and could be compared to Planalto Suite. At northern of the
study area was identified an association of mafic-enderbitic rocks which comprises intensely
deformed and recrystallized hornblende norite, pyroxene-hornblende gabbros, pyroxeneix
hornblende monzonite, hornblende gabbros, amphibolites and enderbites, which are
represented in the geological map as a WNW-ESE small elongated body , and a semicircular
body controlled by shear zones. The textures observed in these rocks indicate that
recrystallization occurs under relatively high temperatures, 6000C or above, and those rocks
show metamorphic features. The geochemical behavior of these rocks suggests that the
hornblende-norite, hornblende-gabbros and amphibolites are tholeiitic subalkalines, whereas
enderbites, pyroxene-hornblende gabbro and pyroxene-hornblende monzonite exhibit calcalkaline
signature. The low La/Yb ratios for mafic rocks indicate low degree of fractionation,
whereas the high La/Yb ratios for enderbites reveal significant fractionation of HREE during
formation and differentiation of its magmas, and the concavity of HREE pattern indicates
probably influence of amphibole fractionation during its evolution. In the central and northcentral
of area was recognized biotite-monzogranites with peraluminous and calc-alkaline
signature and distinct REE patterns, which allowed us to distinguish two groups. The first
shows higher REE enrichment, weak enrichment in LREE relative to HREE, and exhibit
moderate negative Eu anomalies, indicating no significant fractionation of phases enriched in
HREE and show possibly affinity with Bom Jesus Granite from Canaã dos Carajás area. The
second group shows a sharp fractionation of HREE relative to LREE, with discrete or absent
Eu anomalies, and concave HREE patterns indicating that amphibole was important phase
during the fractionation of these rocks, like Serra Dourada and Cruzadão granites, also located
in the Canaã dos Carajás area. This comparison should be enhanced as soon as further
geochemical and geochronological data are available in order to a correlation can be
evaluated.
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