Figure 1:
Location map and distribution of the Piriá Basin in relation to the tectonic domains of the study region.
Figure 2:
Simplified geological map of the study area (adapted from Lopes & Klein 2014Lopes E.C.S., Klein E.L. 2014. Folha Santa Luzia do Pará, SA.23-V-C-VI . Estado do Pará. Programa Geologia do Brasil - PGB, Carta Geológica. Belém: CPRM, escala 1:100.000. and Klein & Sousa 2012Klein E.L., Sousa C.S.S. 2012. Geologia e recursos minerais do Estado do Maranhão: texto explicativo. Escala 1:750.000 . Sistema de Informações Geográficas - SIG; Programa Geologia do Brasil - PGB. Belém, CPRM - Serviço Geológico do Brasil, 150 p.), with location of samples used in geochronological and Nd analyses.
Figure 3:
Schematic block diagram depicting the spatial relationships of the Piriá Basin, structural features and lithofacies subdivision.
Figure 4:
Field and microscopic aspects of rocks of the Piriá Formation. (A) Arkose of the Ap lithofacies with plane-parallel lamination. (B) Photomicrograph (crossed polarizers) of the arkose showing epidote crystals around detrital quartz. (C) Laminated siltstone of the Sp lithofacies. (D) Arkose of the Ah lithofacies with hummocky stratification. (E) Convolute structures in arkose. (F) Conglomerate with quartz pebbles.
Figure 5:
Chemical classification of the rocks of the Piriá Formation (Herron 1988Herron M.M. 1988. Geochemical classification of terrigenous sands and shales from core or log data. Journal of Sedimentary Petrology , 58:820-829.).
Figure 6:
(A, B) Chondrite-normalized rare earth elements and (C, D) primitive mantle-normalized diagrams for the rocks of the Piriá Formation. Normalization is according to Boynton (1984Boynton W.V. 1984. Cosmochemistry of the rare-earth elements: meteorite studies. : Henderson P. (ed.). Rare-Earth Elements geochemistry . Elsevier, Amsterdam, pp. 63-114.) and Sun & McDonough (1989Sun S.S., McDonough W.F. 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle compositions and processes. In: Saunders A.D., Norry M.J. (eds.). Magmatism in ocean basins. Geological Society of London Special Publications , 42:313-345.),respectively. The thick dashed line stands for the Upper Continental Crust (data from Rudnick & Gao 2005Rudnick R.L., Gao S. 2005 Composition of the continental crust. In: Holland H.D.,Turekian K.K. (eds.). The Crust 3 . Treatise on Geochemistry. Elsevier-Pergamon, Oxford, England, p. 1-64.). Samples are separated into two sets for each normalization (A - C and B - D) for clarity (see text for discussion).
Figure 7:
(A) Ternary plot of the chemical index of alteration and A-CN-K (Al2O3 - CaO + Na2O - K2O) diagram (Nesbitt 2003Nesbitt H.W. 2003. Petrogenesis of siliciclastic sediments and sedimentary rocks. : Lentz D.R. (ed.). Geochemistry of sediments and sedimentary rocks: evolutionary considerations to mineral deposit-forming environments. Geological Association of Canada GeoText, vol. 4, pp. 39e51. ), for the sedimentary rocks of the Piriá Formation. Average rock and mineral values are from McLennan et al. (1993McLennan S.M., Hemming S., McDanial D.K., Hanson G.N. 1993. Geochemical approaches to sedimentation, provenance, and tectonics. : Johnsson M.J., Basu A. (eds.). Processes controlling the composition of clastic sediments. Geological Society of America Special Paper , 284:21-40.) and Pettijohn (1975Pettijohn F.J. 1975. Sedimentary Rocks . Harper and Row, New York.). (B) Plot of chemical index of alteration versus the index of chemical variability, after Cox et al. (1995Cox R., Lowe D.R., Cullers R.L. 1995. The influence of sediment recycling and basement composition of evolution of mudrock geochemistry in the southwestern United States. Geochimica et Cosmochimica Acta , 59:2919-2940.) and Potter et al. (2005Potter P.E., Maynard J.B., Depetris P.J. 2005. Mud and Mudstones: Introduction and Overview . Heidelberg, Springer-Verlag, 297 p.). Average rock values according to LaMaskin et al. (2008LaMaskin T.A., Dorsey R.J., Vervoort J.D. 2008. Tectonic controls on mudrock geochemistry, Mesozoic rocks of eastern Oregon and Western Idaho, U.S.A.: implications for cordilleran tectonics. Journal of Sedimentary Research , 78:765-783., and references therein). PAAS is post-Archean Australian average shale (Taylor & McLennan 1985Taylor S.R., McLennan S.M. 1985. The Continental Crust: Its Composition and Evolution . Blackwell Scientific Publications, Oxford, UK, pp. 312.).
Figure 8:
Cathodoluminescence (EL37) and backscattering electron (EK31) images of typical detrital zircon crystals from the Piriá Formation. Scale bars are 300 mm in A, and 200 mm in B, and the spots are numbered as in
Table 2.
Figure 9:
Cumulative age probability plots for detrital zircon of the Piriá Formation. The grey bars show the time interval of known magmatic activity in the São Luís cratonic fragment (2240 - 2009 Ma) and Gurupi Belt (732 - 549 Ma).
Figure 10:
Chemical plots for sedimentary rocks of the Piriá Formation, for evaluation of single or multiple sources and hydraulic sorting (see Fralick et al. 2009Fralick P.W., Hollings P., Metsaranta R., Heaman L.M. 2009. Using sediment geochemistry and detrital zircon geochronology to categorize eroded igneous units: An example from the Mesoarchean Birch-Uchi Greenstone Belt, Superior Province. Precambrian Research , 168:106-122.). (A) Zr-Nb, (B) Ce-Th, and (C) V-TiO2 diagrams.
Figure 11:
Zr-Sc versus Th/Sc plot (McLennan et al. 1993McLennan S.M., Hemming S., McDanial D.K., Hanson G.N. 1993. Geochemical approaches to sedimentation, provenance, and tectonics. : Johnsson M.J., Basu A. (eds.). Processes controlling the composition of clastic sediments. Geological Society of America Special Paper , 284:21-40.). The fields of potential Rhyacian source rocks from the Gurupi Belt and São Luís cratonic fragment were drawn with data from Klein et al. (2008bKlein E.L., Luzardo R., Moura C.A.V., Armstrong R. 2008b. Geochemistry and zircon geochronology of paleoproterozoic granitoids: further evidence on the magmatic and crustal evolution of the São Luís cratonic fragment, Brazil. Precambrian Research , 165:221-242., 2009Klein E.L., Luzardo R., Moura C.A.V., Lobato D.C., Brito R.S.C., Armstrong R. 2009. Geochronology, Nd isotopes and reconnaissance geochemistry of volcanic and metavolcanic rocks of the São Luís Craton, northern Brazil: implications for tectonic setting and crustal evolution. Journal of South American Earth Sciences , 27:129-145., 2012Klein E.L., Rodrigues J.B., Lopes E.C.S., Soledade G.L. 2012. Diversity of Rhyacian granitoids in the basement of the Neoproterozoic-Early Cambrian Gurupi Belt, northern Brazil: geochemistry, U-Pb zircon geochronology, and Nd isotope constraints on the Paleoproterozoic magmatic and crustal evolution. Precambrian Research , 220-221:192-216.).
Figure 12:
Bivariate plots for provenance evaluation. (A) Zr versus TiO2, (B) Al2O3 versus TiO2, (C) La/Sc versus Co/Th, (D) discriminant function 1 and 2, from Roser & Korsch (1988Roser B.P., Korsch R.J. 1988. Provenance signatures of sandstone mudstone suites determined using discriminant function analysis of major-element data. Chemical Geology , 67:119-139.), (E) Hf versus La/Th (after Floyd & Leveridge 1987Floyd P.A., Leveridge B.E. 1987. Tectonic environment of the Devonian Gramscatho basin, south Cornwall; framework mode and geochemical evidence from turbidite sandstones. Journal of the Geological Society , 144:531-532); the cross stands for the Upper Continental Crust of Rudnick & Gao (2004Rudnick R., Gao S. 2004. The composition of the continental crust. In: Rudnick R. (ed.). Treatise on Geochemistry: The Crust. Elsevier, Amsterdam , pp. 1-64.).
Figure 13:
εNd(0) versus f(Sm/Nd) diagram for the Piriá Formation in comparison with the composition of potential sources from the São Luís cratonic fragment and Gurupi Belt. Source of data: Klein et al. (2005Klein E.L., Moura C.A.V., Krymsky R., Griffin W.L. 2005. The Gurupi belt in northern Brazil: lithostratigraphy, geochronology, and geodynamic evolution. Precambrian Research , 141:83-105., 2008bKlein E.L., Luzardo R., Moura C.A.V., Armstrong R. 2008b. Geochemistry and zircon geochronology of paleoproterozoic granitoids: further evidence on the magmatic and crustal evolution of the São Luís cratonic fragment, Brazil. Precambrian Research , 165:221-242., 2009Klein E.L., Luzardo R., Moura C.A.V., Lobato D.C., Brito R.S.C., Armstrong R. 2009. Geochronology, Nd isotopes and reconnaissance geochemistry of volcanic and metavolcanic rocks of the São Luís Craton, northern Brazil: implications for tectonic setting and crustal evolution. Journal of South American Earth Sciences , 27:129-145., 2012Klein E.L., Rodrigues J.B., Lopes E.C.S., Soledade G.L. 2012. Diversity of Rhyacian granitoids in the basement of the Neoproterozoic-Early Cambrian Gurupi Belt, northern Brazil: geochemistry, U-Pb zircon geochronology, and Nd isotope constraints on the Paleoproterozoic magmatic and crustal evolution. Precambrian Research , 220-221:192-216.), Palheta et al. (2009Palheta E.S., Abreu F.A.M., Moura C.A.V. 2009. Granitóides proterozoicos como marcadores da evolução geotectônica da região nordeste do Pará - Brasil. Revista Brasileira de Geociências , 39:647-657.), Klein & Lopes (2011Klein E.L., Lopes E.C.S. 2011. Geologia e recursos minerais da Folha Centro Novo do Maranhão - SA.23-Y-D-I, Estados do Maranhão e Pará, Escala 1:1.000.000 Belém, CPRM - Serviço Geológico do Brasil, CD-ROM.). The Precambrian upper crust and arc rocks boxes are from McLennan & Hemming (1992McLennan S.M., Hemming S. 1992. Samarium/neodymium elemental and isotopic systematics in sedimentary rocks. Geochimica et Cosmochimica Acta , 56:887-898.).
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