Field and petrographic data of 1.90 to 1.88 Ga I- and A-type granitoids from the central region of the Amazonian Craton, NE Amazonas State, Brazil

Abstract

The SW Presidente Figueiredo district, which is located in the northeastern Amazonas State of the central Amazonian Craton, Brazil, consists of 1890 to 1898 Ma I-type granitoids (Terra Preta Granite, Água Branca Suite), A-type hornblende-bearing syenogranites (Canoas Syenogranite, Mapuera Suite), felsic to intermediate volcanic rocks (Iricoumé Group), and 1883 to 1889 Ma rapakivi granites (São Gabriel Granite, Mapuera Suite) and related rocks (quartz-gabbroanorthosite and diorite), in addition to Castanhal quartz-monzonite, mylonites, and hornfels. The quartz-diorite facies of Terra Preta Granite were formed by mingling processes between a synplutonic quartz-gabbro dike and a hornblende granodiorite. Partially assimilated globules of Canoas hornblende-bearing syenogranite and their clear contacts with Terra Preta hornblende granodiorite suggest that Canoas Syenogranite is slightly younger than Terra Preta Granite. Canoas Syenogranite xenoliths inside São Gabriel Granite show that the granite is younger than the Canoas Syenogranite. New geologic and petrographic evidence improve the petrological understanding of these rocks and suggest that, in addition to fractional crystallization, assimilation and magma mingling played a role, at least at the local scale, in the evolution and compositional variation of the plutons. Such evidence is found in Terra Preta Granite mingled quartz-diorite, felsic material associated with the Canoas Syenogranite and in the intermediate microgranular enclaves, which exhibit primary biotite in hornblende-bearing rocks, plagioclase dissolution, corrosion of feldspars rims, alkali feldspar mantles, second apatite generation, and high xenocrystal contents in intermediate enclaves formed from the fragmentation of mafic intrusions. Petrographic analyses show that a deformational event recorded in the western part of the study area (with progressive deformation from E to W) is dated between the 1.90 Ga postcollisional magmatism and the intrusions of the São Gabriel Granite and related mafic/intermediate rocks (intra-plate). However, it is extremely necessary to obtain absolute ages for this metamorphic event.Keywords: field data; petrography; I-and A-type granitoids; lithostratigraphy; NE Amazonas State. RESUMO Dados de campo e petrográficos de granitoides dos tipos I e A de 1,90 a 1,88 Ga da região central do Cráton amazônico, NE do Estado do Amazonas, Brasil. O SW do município de Presidente Figueiredo, localizado noEstado do Amazonas, Nordeste do Cráton Amazônico Central, Brasil, hospeda granitoides do tipo I de idade entre 1890 a 1898 Ma (Terra Preta Granito, Suíte Água Branca), hornblenda-sienogranitos do tipo A (Sienogranito Canoas da Suíte Mapuera), rochas vulcânicas ácidas à intermediárias (Grupo Iricoumé) e granitos rapakivi de idades entre 1883 a 1889 Ma (Granito São Gabriel da Suíte Mapuera), e rochas afins (quartzo-gabro-anortosito e diorito), além de quartzo-monzonito Castanhal, milonitos e hornfels. A fácies quartzo-diorito do granito Terra Preta foi formada por proces...

Paleoproterozoic evolution of the Guiana Shield in Suriname: A revised model

“…The source of the ash-fall tuffs is unknown, but in view of the very large area in which they are dispersed they must represent tremendous eruptions. Along the southern border of the Guiana Shield in Brazil the Iricoumé volcanics and associated granitic intrusions of 1.89-1.81 Ga (Valério et al, 2012;Marques et al, 2014;Barreto et al, 2013; Fig. 2) have the right age and composition to produce the Roraima ash layers, and caldera-like structures have been documented from the Pitinga mining district (Pierosan et al, 2011).…”

K'Mudku A-type magmatism in the southernmost Guyana Shield, central-north Amazon Craton (Brazil): the case of Pedra do Gavião syenogranite

“…In general, these K´Mudku A-type granites have texture, petrographic and geochemical features similar to those of the Paleopreoterozoic Mapuera and Madeira A-type (Pearce et al 1984). granites suites, which are exposed also in the southernmost portion of the Guyana shield, but in the Tapajós-Parima province (according to model suggested by Santos et al 2000Santos et al , 2006a, and mainly located within of the WaimiriAtroari indigenous reserve area (Costi et al 2000, CPRM 2006, Valério et al 2009, Ferron et al 2010. Due to the poor geological/geochronological knowledge of this region, it is likely that some granite, previously considered being Paleoproterozoic intrusions are in fact chronologically related to the Mesoproterozoic K'Mudku event (e.g.…”

https://jgsb.cprm.gov.br/index.php/journal/issue/view/24

“…The calc-alkalic granitic types which occur within the Uatumã SLIP are considered by several authors to be formed as magmatic arcs within orogenic environments (Santos 2003, Tassinari and Macambira 2004, Cordani and Teixeira 2007, Valério et al 2012 and shall be distinguished from anorogenic types associated to intraplate episodes. However, several other authors (Almeida 2006, Vasquez and Rosa-Costa 2008, Klein et al 2012, Fraga et al 2017, Roverato et al 2019) argued that calc-alkaline magmatism may be generated in processes not associated with subduction, but linked with intracontinental environments, with more stable tectonic conditions, where A-type granites can also be formed.…”