The Mesoarchean plutonic complex from the Carajás province, Amazonian craton: Petrogenesis, zircon U[sbnd]Pb SHRIMP geochronology and tectonic implications

Abstract

This study investigates the origin of the different Mesoarchean granitoids of the Ourilândia plutonic complex from the Carajás province (northern Brazil), as well as their geodynamic significance. This complex integrates interdigitated plutons of 2.88 Ga biotite granite (BG) and sanukitoid (SNK), with subordinate high-K calc-alkaline (HKCA) granodiorite-granite and tonalite-trondhjemite-granodiorite (TTG). (i) The BG is represented by equigranular monzogranite, which can be formed by 18% melting from TGG-type trondhjemite. (ii) The SNKs are composed of granodiorites (equigranular, heterogranular and porphyritic), with subordinate tonalite, quartz monzodiorite and quartz diorite, all with mafic microgranular enclaves. The different SNK-type granitoids and quartz monzodiorite were generated by 18–33% melting from mantle previously enriched by 20–40% TTG-type melt in the garnet stability zone. On the other hand, quartz diorite and mafic enclaves formed from fluid-metasomatized mantle at lower depths. (iii) The HKCA granodiorite-granite group (also called high-Ti SNK) is composed of porphyritic granodiorite and heterogranular monzogranite. The granodiorite can be formed by 30% melting from mantle enriched by 40% TTG-type melt under oxidizing conditions, with the participation of a component enriched in HFSEs. The heterogranular monzogranite is a hybridization product between 60% metasomatized mantle-derived magmas (high-Ti granodiorite) and 40% crust-derived magmas (equigranular monzogranite). (iv) The TTG-type tonalitic xenolith and porphyritic trondhjemite were formed by partial melting of hydrous metabasalts; however, the trondhjemite petrogenesis involves hybridization with enriched mantle-derived magmas. The BG and SNK provided coeval crystallization ages of 2881 ± 10 Ma and 2886 ± 14 Ma, respectively. In addition, in the BG, three more crystal populations were identified with ages of 3040 ± 40 Ma, 2976 ± 09 Ma and 2934 ± 21 Ma. The first two are interpreted as xenocrystals, and the latter is interpreted as inherited crystals. ∼2.88 Ga represents the main period of crustal growth in the Ourilândia do Norte area, with emplacement of juvenile magmas and crustal reworking. The studied rocks were formed in a post-subduction collision setting with coeval mantle and crust-derived magma generation over a short time span (∼2.88 Ga), where shear zones conditioned the ascent and emplacement of the Ourilândia magmas.