Genesis of the Gentio Metagranitoid: Post-Collisional High-K Plutonism within the Mineiro Belt, São Francisco Craton, Brazil

Abstract

The Gentio metagranitoid presents equigranular and porphyritic facies, modal composition ranging from tonalite to monzogranite with calculated T _Zr<800 °C for most samples. Its mineralogy is dominated by quartz and feldspar (77% to 95%), biotite is the only mafic mineral present (2% to 18%) and, titanite, zircon, apatite, allanite are important accessory phases. These rocks range from metaluminous to weakly peraluminous, and have large variation in major and trace elements, and high alkali contents (>6 wt.%). Zircon analyses by LA-ICP-MS and SHRIMP yielded a concordia age of 2 119±10 Ma for the porphyritic facies and an upper intercept age of 2 111±15 Ma for the equigranular facies. The whole-rock Sm-Nd T _DM ages vary from 2.4 to 2.8 Ga with ε _Nd(2.1) values between −0.7 and −5.3, indicating crustal derivation from distinct and/or heterogeneous protoliths. Field observations indicate that the Gentio metagranitoid was formed through different pulses of magma. Individual batches were subject to little or even no fractionation process after its emplacement. Although the Gentio metagranitoid crosscuts metamafic and metaultramafic rocks akin to an oceanic arc setting, this pluton is likely originated by partial melting of a more evolved quartz-feldspathic crustal igneous rock in a post-collisional environment, after the accretion of the arcs from the Mineiro belt and rocks of the Mantiqueira Complex.

Keywords

high-K granites / Mineiro belt / post-collisional / São Francisco Craton / U-Pb geochronology

References

[1] Abdel-Rahman A F M. Nature of Biotites from Alkaline, Calc-Alkaline, and Peraluminous Magmas. Journal of Petrology, 1994, 35(2): 525-541.

[2] Alkmim, F. F., Teixeira, W., 2017. The Paleoproterozoic Mineiro Belt and the Cuadrilátero Ferrífero. In: Heilbron, M., Cordani, U., Alkmim, F., eds., São Francisco Craton, Eastern Brazil: Tectonic Genealogy of a Miniature Continent (Regional Geology Reviews). Springer. 45–62. https://doi.org/10.1007/978-3-319-01715-0_5

[3] Annen C. Implications of Incremental Emplacement of Magma Bodies for Magma Differentiation, Thermal Aureole Dimensions, and Plutonism-Volcanism Relationships. Tectonophysics, 2011, 500(1–4): 3-10.

[4] Ávila, C. A., Bezerra Filho, A. P., Oliveira, N. D. B., et al., 2006a. Resultados Preliminares da Geologia do Quartzo Diorito Dores do Campo, Região de Tiradentes—Dores do Campo, Estado de Minas Gerais. In: XLIII Congresso Brasileiro de Geologia, Aracaju. 1: 183 (in Portuguese)

[5] Ávila C A, Teixeira W, Cordani U G, . The Glória Quartz-Monzodiorite: Isotopic and Chemical Evidence of Arc-Related Magmatism in the Central Part of the Paleoproterozoic Mineiro Belt, Minas Gerais State, Brazil. Anais da Academia Brasileira de Ciencias, 2006, 78(3): 543-556.

[6] Ávila, C. A., Teixeira, W., Cordani, U. G., et al., 2010. Rhyacian (2.23–2.20 Ga) Juvenile Accretion in the Southern São Francisco Craton, Brazil

[7] Geochemical and Isotopic Evidence from the Serrinha Magmatic Suite, Mineiro Belt. Journal of South America Earth Sciences, 29(2): 464–482. https://doi.org/10.1016/j.jsames.2009.07.009

[8] Ávila C A, Teixeira W, Vasques F S G, . Geoquímica e Idade U-Pb (LA-ICPMS) da Crosta Oceânica Riaciana do Cinturão Mineiro, Borda Meridional do Cráton São Francisco. Anais do Congresso Brasileiro de Geologia, 2012, 46: 4-5.

[9] Ávila C A, Teixeira W, Bongiolo E M, . Rhyacian Evolution of Subvolcanic and Metasedimentary Rocks of the Southern Segment of the Mineiro Belt, São Francisco Craton, Brazil. Precambrian Research, 2014, 243(4): 221-251.

[10] Barbosa N S, Teixeira W, Ávila C A, . 2.17–2.10 Ga Plutonic Episodes in the Mineiro Belt, São Francisco Craton, Brazil: U-Pb Ages, Geochemical Constraints and Tectonics. Precambrian Research, 2015, 270: 204-225.

[11] Barbosa N T, Teixeira W, Ávila C A, . U-Pb Geochronology and Coupled Hf-Nd-Sr Isotopic-Chemical Constraints on the Cassiterita Orthogneiss (2.47 to 2.41 Ga) in the Mineiro Belt, São Francisco Craton: Geodynamic Fingerprints beyond the Archean-Paleoproterozoic Transition. Precambrian Research, 2019, 326: 399-416.

[12] Bea F. Controls on the Trace Element Composition of Crustal Melts. Special Paper of the Geological Society of America, 1996, 315: 33-41.

[13] Beard J S, Lofgren G E. Dehydration Melting and Water-Saturated Melting of Basaltic and Andesitic Greenstones and Amphibolites at 1, 3, and 6.9 kb. Journal of Petrology, 1991, 32(2): 365-401.

[14] Black L P, Kamo S L, Allen C M, . TEMORA 1: A New Zircon Standard for Phanerozoic U-Pb Geochronology. Chemical Geology, 2003, 200(1/2): 155-170.

[15] Boehnke P, Watson E B, Trail D, . Zircon Saturation Re-Revisited. Chemical Geology, 2013, 351: 324-334.

[16] Cardoso C D, Ávila C A, Neumann R, . A Rhyacian Continental Arc during the Evolution of the Mineiro Belt, Brazil: Constraints from the Rio Grande and Brumado Metadiorites. Lithos, 2019, 326/327: 246-264.

[17] Clemens J D, Wall V J. Origin and Crystallization of some Peraluminous (S-Type) Granitic Magmas. Canadian Mineralogist, 1981, 19(1): 111-131

[18] Clemens J D, Vielzeuf D. Constraints on Melting and Magma Production in the Crust. Earth and Planetary Science Letters, 1987, 86(2–4): 287-306.

[19] Clemens J D, Helps P A, Stevens G. Chemical Structure in Granitic Magmas—A Signal from the Source?. Special Paper of the Geological Society of America, 2009, 472: 159-172.

[20] Condie K. Changing Tectonic Settings through Time: Indiscriminate Use of Geochemical Discriminant Diagrams. Precambrian Research, 2015, 266: 587-591.

[21] Conrad W K, Nicholls I A, Wall V J. Water-Saturated and -Undersaturated Melting of Metaluminous and Peraluminous Crustal Compositions at 10 kb: Evidence for the Origin of Silicic Magmas in the Taupo Volcanic Zone, New Zealand, and Other Occurrences. Journal of Petrology, 1988, 29(4): 765-803.

[22] DePaolo D J. A Neodymium and Strontium Isotopic Study of the Mesozoic Calc-Alkaline Granitic Batholiths of the Sierra Nevada and Peninsular Ranges, California. Journal of Geophysical Research, 1981, 86(B11): 10470-10488.

[23] Duarte B P, Valente S C, Heilbron M, . Petrogenesis of the Orthogneisses of the Mantiqueira Complex, Central Ribeira Belt, SE Brazil: An Archaean to Palaeoproterozoic Basement Unit Reworked During the Pan-African Orogeny. Gondwana Research, 2004, 7(2): 437-450.

[24] Ebadi A, Johannes W. Beginning of Melting and Composition of First Melts in the System Qz-Ab-Or-H₂O-CO2. Contributions to Mineralogy and Petrology, 1991, 106(3): 286-295.

[25] Elhlou S, Belousova E, Griffin W L, . Trace Element and Isotopic Composition of GJ-Red Zircon Standard by Laser Ablation. Geochimica et Cosmochimica Acta, 2006, 70(18): A158

[26] Farina F, Stevens G, Villaros A. Multi-Batch, Incremental Assembly of a Dynamic Magma Chamber: The Case of the Peninsula Pluton Granite (Cape Granite Suite, South Africa). Mineralogy and Petrology, 2012, 106 3/4 193-216.

[27] Frost B R, Barnes C G, Collins W J, . A Geochemical Classification for Granitic Rocks. Journal of Petrology, 2001, 42(11): 2033-2048.

[28] Heilbron M, Duarte B P, Valeriano C M, . Evolution of Reworked Paleoproterozoic Basement Rocks within the Ribeira Belt (Neoproterozoic), SE-Brazil, Based on U-Pb Geochronology: Implications for Paleogeographic Reconstructions of the São Francisco-Congo Paleocontinent. Precambrian Research, 2010, 178(1–4): 136-148.

[29] Heilbron, M., Ribeiro, A., Valeriano, C. M., et al., 2017. The Ribeira Belt. In: Heilbron, M., Cordani, U., Alkmim, F., eds., São Francisco Craton, Eastern Brazil: Tectonic Genealogy of a Miniature Continent (Regional Geology Reviews). Springer. 277–302

[30] Higgins, M. D., 1999. Origin of Megacrysts in Granitoids by Textural Coarsening; A Crystal Size Distribution (CSD) Study of Microcline in the Cathedral Peak Granodiorite, Sierra Nevada, California. In: Fernandez, C., Castro, A., Vigneresse, J. L., eds., Understanding Granites: Integrating Modern and Classical Techniques. Geological Society Special, 168: 207–219

[31] Holtz F, Barbey P, Johannes W, . Composition and Temperature at the Minimum Point in the Qz-Ab-Or System for H₂O-Undersaturated Conditions: Experimental Investigation. Terra Cognita, 1989, 1: 271-272.

[32] Holtz F, Johannes W. Genesis of Peraluminous Granites: I. Experimental Investigation of Melt Composition at 3 and 5 kb and Various H₂O Activities. Journal of Petrology, 1991, 32(5): 935-958.

[33] Holtz F, Johannes W, Tamic N, . Maximum and Minimum Water Contents of Granitic Melts Generated in the Crust: A Reevaluation and Implications. Lithos, 2001, 56(1): 1-14.

[34] Johannes W, Holtz F. Petrogenesis and Experimental Petrology of Granitic Rocks, 1996, Berlin: Springer, 335

[35] Johnson B R, Glazner A F. Formation of K-Feldspar Megacrysts in Granodioritic Plutons by Thermal Cycling and Late-Stage Textural Coarsening. Contributions to Mineralogy and Petrology, 2010, 159(5): 599-619.

[36] Kösler J, Fonneland H, Sylvester P, . U-Pb Dating of Detrital Zircons for Sediment Provenance Studies—A Comparison of Laser Ablation ICPMS and SIMS Techniques. Chemical Geology, 2002, 182(2): 605-618.

[37] Ludwig K R. Squid (1.13b): A User’s Manual, 2001, Berkeley: Berkeley Geochronology Center Special Publication, 2

[38] Ludwig K R. User’s Manual for ISOPLOT 3.00: A Geochronological Toolkit for Microsoft Excel, 2003, Berkeley: Berkeley Geochronological Center Special Publication, 70 4

[39] Luth W C, Jahns R H, Tuttle O F. The Granite System at Pressure of 4 to 10 Kilobars. Journal of Geophysical Research, 1964, 69: 759-773.

[40] Maalöe S, Wyllie P J. Water Content of a Granite Magma Deduced from the Sequence of Crystallization Determined Experimentally with Water-Undersaturated Conditions. Contributions to Mineralogy and Petrology, 1975, 52(3): 175-191.

[41] Middlemost E A K. Magmas and Magmatic Rocks, 1985, London: Logman, 87-88

[42] Miller C F, Furbish D J, Walker B A, . Growth of Plutons by Incremental Emplacement of Sheets in Crystal-Rich Host: Evidence from Miocene Intrusions of the Colorado River Region, Nevada, USA. Tectonophysics, 2011, 500(1): 65-77.

[43] Mills R D, Glazner A F. Experimental Study on the Effects of Temperature Cycling on Coarsening of Plagioclase and Olivine in an Alkali Basalt. Contributions to Mineralogy and Petrology, 2013, 166(1): 97-111.

[44] Moreira H, Seixas L, Storey C, . Evolution of Siderian Juvenile Crust to Rhyacian High Ba-Sr Magmatism in the Mineiro Belt, Southern São Francisco Craton. Geoscience Frontiers, 2018, 9(4): 977-995.

[45] Moyen J-F, Laurent O. Archaean Tectonic Systems: A View from Igneous Rocks. Lithos, 2018, 302/303: 99-125.

[46] Nakamura N. Determination of REE, Ba, Fe, Mg, Na and K in Carbonaceous and Ordinary Chondrites. Geochimica et Cosmochimica Acta, 1974, 38(5): 757-775.

[47] Noce C M, Pedrosa-Soares A C, Silva L C, . Evolution of Polycyclic Basement Complexes in the Araçuaí orogen, Based on U-Pb SHRIMP Data: Implication of Brazil-Africa Links in Paleoproterozoic Time. Precambrian Research, 2007, 159(1/2): 60-78.

[48] Nockolds S R. The Relation between Chemical Composition and Paragenesis in the Biotite Micas of Igneous Rocks. American Journal of Science, 1947, 245: 401-420.

[49] Patiño Douce A E, Beard J S. Dehydration Melting of Biotite Gneiss and Quartz Amphibolite from 3 to 15 kbar. Journal of Petrology, 1995, 36(3): 707-738.

[50] Patiño Douce A E, McCarthy T C. Hacker B, Liou J G. Melting of Continental Rocks During Continental Collision and Subduction. When Continents Collides: Geodynamics and Geochemistry of Ultra-High Pressure Rocks, 1998, Dordrecht: Kluwer Academic Publisher, 27-55.

[51] Pearce J A, Harris N B W, Tindle A G. Trace Elements Discrimination Diagrams for the Tectonic Interpretation of Granite Rocks. Journal of Petrology, 1984, 25(4): 956-983.

[52] Pearce J. Sources and Settings of Granitic Rocks. Episodes, 1996, 19(4): 120-125.

[53] Peccerillo A, Taylor S R. Geochemistry of Eocene Calc-Alkaline Volcanic Rocks from the Kastamonu Area, Northern Turkey. Contributions to Mineralogy and Petrology, 1976, 58(1): 63-81.

[54] Petronilho, L. A., 2009. O Método Sm-Nd no CPGeo-IGc-USP: Procedimentos Analíticos Atualmente em Rotina. Simpósio 45 anos de Geocronologia no Brasil, Instituto de Geociências, USP. Boletim de Resumos Expandidos, São Paulo. 116–2118 (in Portuguese)

[55] Pimentel M M, Charnley N. Intracrustal REE Fractionation and Implications for SMND Model Age Calculations in Late-Stage Granitic Rocks: An Example from Central Brazil. Chemical Geology: Isotope Geoscience Section, 1991, 86(2): 123-138

[56] Ribeiro A, Teixeira W, Dussin I A, . U-Pb LA-ICP-MS Detrital Zircon Ages of the São João del Rei and Carandaí Basins: New Evidence of Intermittent Proterozoic Rifting in the São Francisco Paleocontinent. Gondwana Research, 2013, 24(2): 713-726.

[57] Roberts M P, Clemens J D. Origin of High-Potassium, Talc-Alkaline, I-Type Granitoids. Geology, 1993, 21(9): 825-828.

[58] Sato K, Tassinari C C G, Kawashita K, . O Método Geocronológico Sm-Nd no IG/USP e Suas Aplicações. Anais da Academia Brasileira de Ciências, 1995, 67: 313-336.

[59] Sato, K., Basei, M. A. S., Siga Junior, O., et al., 2010. In situ U-Th-Pb Isotopic Analyses by Excimer Laser Ablation/ICP-MS on Brazilian Megacrystal Xenotime: First Results on U-Pb Isoptes at CPGeo-IGC-USP. VII SSAGI-South American Simposium on Isotope Geology, Brasília. 349–352

[60] Sato K, Tassinari C C G, Basei M A S, . Sensitive High Resolution Ion Microprobe (SHRIMP IIe/MC) of the Institute of Geosciences of the University of São Paulo, Brazil: Analytical Method and First Results. Geologia USP, Série Científica, 2014, 14(3): 3-18.

[61] Sawyer E W, Cesare B, Brown M. When the Continental Crust Melts. Elements, 2011, 7(4): 229-234.

[62] Seixas L A R, David J, Stevenson R. Geochemistry, Nd Isotopes and U-Pb Geochronology of a 2 350 Ma TTG Suite, Minas Gerais, Brazil: Implications for the Crustal Evolution of the Southern São Francisco Craton. Precambrian Research, 2012, 196/197: 61-80.

[63] Seixas L A R, Bardintzeff J M, Stevenson R, . Petrology of the High-Mg Tonalites and Dioritic Enclaves of the ca. 2 130 Ma Alto Maranhão Suite: Evidence for a Major Juvenile Crustal Addition Event during the Rhyacian Orogenesis, Mineiro Belt, Southeast Brazil. Precambrian Research, 2013, 238: 18-41.

[64] Silva M M, Holtz F, Namur O. Crystallization Experiments in Rhyolitic Systems: The Effect of Temperature Cycling and Starting Material on Crystal Size Distribution. American Mineralogist, 2017, 102(11): 2284-2294.

[65] Silva M M, Ávila C A, Barbosa N S, . Caracterização do Ortognaisse Brejo Alegre e sua Inserção no Contexto Evolutivo do Cinturão Mineiro, Cráton do São Francisco. Anuário do Instituto de Geociências—UFRJ, 2020, 43(2): 252-269

[66] Stacey J S, Kramers J D. Approximation of Terrestrial Lead Isotope Evolutionby a Two Stage Model. Earth and Planetary Science Letters, 1975, 26(2): 207-221.

[67] Teixeira W, Ávila C A, Nunes L C. Nd-Sr Isotopic Geochemistry and Geochronology of the Fé Granitic Gneiss and Lajedo Granodirite: Implications for Paleoproterozoic Evolution of the Mineiro Belt, Southern São Francisco Craton, Brazil. Revista do Instituto de Geociências, 2008, 8: 53-74.

[68] Teixeira W, Ávila C A, Dussin I A, . A Juvenile Accretion Episode (2.35–2.32 Ga) in the Mineiro Belt and Its Role to the Minas Accretionary Orogeny: Zircon U-Pb-Hf and Geochemical Evidences. Precambrian Research, 2015, 256(4): 148-169.

[69] Thompson A B, Connolly J A D. Melting of the Continental Crust: Some Thermal and Petrological Constraints on Anatexis in Continental Collision Zones and Other Tectonic Settings. Journal of Geophysical Research, 1995, 100(B8): 15565-15579.

[70] Tuttle O F, Bowen N L. Origin of Granite in the Light of Experimental Studies in the System NaAlSi₃O₈-KA1Si₃O₈-SiO₂-H₂O. Geological Society of America Memoir, 1958, 74: 1-154.

[71] Vasconcelos F F, Ávila C A, Neumann R, . Ortognaisse Morro do Resende: Mineralogia, Petrografia, Geoquímica e Geocronologia. Geologia USP. Série Científica, 2017, 17: 143-164.

[72] Vernon R H, Paterson S R. How Late are K-Feldspar Megacrysts in Granites?. Lithos, 2008, 104(1–4): 327-336.

[73] Villaseca C, Barbero L, Herreros V. A Re-Examination of the Typology of Peraluminous Granite Types in Intracontinental Orogenic Belts. Transactions of the Royal Society of Edinburgh, Earth Sciences, 1998, 89(2): 113-119.

[74] Watson E B, Harrison T M. Zircon Saturation Revisited: Temperature and Composition Effects in a Variety of Crustal Magma Types. Earth Planetary Science Letters, 1983, 64(3): 295-304.

[75] Weaver B L, Tarney J. Empirical Approach to Estimating the Composition of the Continental Crust. Nature, 1984, 310(5978): 575-577.

[76] Weinberg R F, Hasalová P. Water-Fluxed Melting of the Continental Crust: A Review. Lithos, 2015, 212–215: 158-188.

[77] Whitney J A. The Origin of Granite: The Role and Source of Water in the Evolution of Granitic Magmas. Geological Society of America Bulletin, 1988, 100(12): 1886-1897.