Modern analytical equipment such as the Multicollector-Inductively Coupled Plasma
Mass Spectrometer, connected to a Laser Ablation microprobe (LA-MC-ICP-MS), made U-Pb
geochronological analysis of zircon more accessible and allowed the collection of large amount
of data. As a result, the dating of detrital zircon grains has become an important tool in
sedimentary provenance studies, since it may provide direct information about the ages of the
igneous and/or metamorphic rocks of the source areas that contributed to the deposits of a
sedimentary basin. This tool, together with the morphological analyzes of the dated detrital
zircons, was applied to provenance studies on the sedimentary rocks of the Igarapé de Areia
and Piriá formations, that crop out in the northeast of Pará and northwest of Maranhão states.
These sedimentary successions occur in the midst of rocks of the São Luís Craton (SLC), and
Gurupi Belt (GB) geotectonic domains. The former is of Paleoproterozoic age and the GSB
incorporates significant portions of the SLC strongly reworked in the Neoproterozoic. The
Igarapé de Areia Formation is composed of medium grain arcosian sandstones with trough cross
stratification, marked by levels of opaque minerals, indicating deposition in medium to highenergy
fluvial systems. The maximum depositional age of this unit is 1940 ± 55 Ma, and the
sedimentary contribution is restricted to sources from the Rhyacian period (2052 - 2269 Ma),
which is consistent with the age of crustal growth of Saouth American Plataform. The Piriá
Formation occurs in both geotectonic domains. For the succession that lies over the GB, here
called the West Segment, detrital zircons from two sandstones of the arkose and greywacke
interbedded with pelitic layers lithofacies, and from one conglomerate of the conglomeratic
lithofacies were analyzed. The geochronological dates from the sandstones present subordinate
peaks of Neoproterozoic (509 - 951 Ma) and Mesoproterozoic ages (1243 - 1630 Ma), and a
main peak of Paleoproterozoic age, mostly Rhyacian (2050 - 2266 Ma). The conglomerate
facies is made up of ortho- and paraconglomerates whose constituents indicate igneous and
metamorphic sources. The ages of the detrital zircon grains are basically between 1950 and
2298 Ma, which suggest, from the geochronological point of view, that the sediments may have
come from a Paleoproterozoic source area, unlike the sandstones of this segment. On the other
hand, the Piriá Formation rocks that occur on the SLCF, East Segment, correspond to arkose
with plane-parallel stratification interlayered with siltites, and were probably deposited in
portions of lower energy of fluvial channels. The histogram of cumulative ages of the detrital
zircon from an arkose shows the predominance of younger source areas (525 - 824 Ma). The
maximum depositional age for the Piriá Formation is estimated at 509 ± 17 Ma. The discrepancy
in the distribution of zircon ages between the arkoses of the East and West segments of the Piriá
Formation indicates the contribution of different source areas, suggesting that these segments
could represent sub-basins or sedimentary successions deposited in different periods of time.
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