High-Mg andesites (HMA) from the Serra do Rabo region, Carajás province, Amazonian craton, Brazil: An Archean (2.92 Ga) eruptive sanukitoid

Mesoarchean (2.92 Ga) high-Mg andesites (HMA) are present in the Serra do Rabo region, eastern Carajás province, Amazonian craton, Brazil. Petrographic and geochemical studies revealed at least three magmatic groups: low-silica andesites, high-silica andesites, and crystal-rich mafic rocks. These rocks exhibit a marked mantle affinity, as evidenced by high Mg, Cr, and Ni contents. However, the trace element pattern reveals enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSEs), with a prominent negative niobium (Nb) anomaly. Nd isotope data demonstrate that these rocks represent juvenile magmas with short crustal residence times. Only two samples present negative Ɛ Nd (t), indicating interactions with older crust during magma ascent. These characteristics suggest a strong affinity with sanukitoid magmas originating from a mantle source metasomatized by fluids and silicic melts. Subsequent evolution occurred at shallow crustal levels driven by crystal melt segregation processes, resulting in a cogenetic sequence composed of crystal-rich mafic rocks, intermediate andesitic members, and, finally, a silica-rich melt.