Geology, geochemistry and zircon SHRIMP U–Pb geochronology of Mesoarchean high-Mg granitoids: constraints on petrogenesis, emplacement timing and deformation of the Água Limpa suite in the Carajás Province, SE Amazonian Craton Available to Purchase

Determining the age, geochemical characteristics and conditions of deformation of Mesoarchean sanukitoids is crucial in unravelling the petrogenesis and tectonic significance of mantle-derived rocks. We report the whole-rock major and trace element contents, zircon U–Pb geochronology and geochemical modelling of samples from the Água Limpa sanukitoid suite in the Sapucaia subdomain (the Carajás Province, Amazonian Craton). This suite includes two plutons, named Água Limpa and Água Azul, which are exposed across east–west transpressive sinistral shear zones that act as boundaries between the Rio Maria and Carajás domains. These plutons are composed of porphyritic granodiorites, tonalites and subordinate monzogranites, with amphibole, biotite and epidote as the main mafic mineral components. They are characterized by high contents of Cr (102–383 ppm), Ni (32–117 ppm), MgO (2.50–4.78 wt%), Sr (477–912 ppm) and Ba (519–1966 ppm), with high Mg# values of 49–64. The rare earth element patterns show significant fractionation of the heavy rare earth elements, with high La_N/Yb_N (18–170) ratios and no or weak Eu anomalies (Eu/Eu* 0.66–1.21). The studied rocks are predominantly medium-K, calc-alkaline and metaluminous, and are geochemically distinct from tonalite–trondhjemite–granodiorites (TTGs) and Archean leucogranodiorites. The Água Limpa and Água Azul plutons yield coeval crystallization ages of 2870 ± 4 and 2872 ± 5 Ma, respectively, with other zircon population ages of 3063 ± 6, 2926 ± 12 and 2849 ± 12 Ma. The first of these other zircon populations is interpreted as xenocrysts, the second as crystals inherited from the modelled TTG-type source and the third as crystals reflecting the age of metamorphism. Most of the suite fractionated from a common mafic parent through 20% partial melting of a mantle previously enriched by 32% TTG-type melt in the garnet stability zone and under oxidized conditions. The combined dataset indicates that the studied sanukitoids are syntectonic intrusions, with distinct pulses of magma transfer facilitated by shear zone reactivation and subordinate small-scale dyking.