Composite batholith assembly in a Paleoproterozoic continental arc – western Cauaburi Complex, northwestern Amazon Craton, Brazil

Abstract

The Cauaburi Complex, northwestern Amazon Craton, represents the plutonic record of an Orosirian-Statherian magmatic arc (1.81–1.76 Ga). Despite the subsequent metamorphic events, primary features have been preserved, maintaining the magmatic characteristics of typical supra-subduction batholiths in the western portion of the Cauaburi Arc. The petrological characterization, field data, petrography, and lithochemistry reveal distinct magmatic facies in western Cauaburi Complex rocks. In a concentric pattern, tonalites hosted granodioritic to monzogranitic magmas, both with mafic microgranular enclaves. The magmatic reservoir remains active for approximately 45 Myr, and the magma replenishment and differentiation processes occur during the batholith's assembling. High-silica granites emerge from the magmatic mushes and differ from them in petrological terms. However, the crystallization age of 1763 ± 21 Ma coincides with the geochronological record of the calc-alkaline rocks nearby. Based on the analysis of the field relations and petrological process, we discuss how alkaline high-silica granites differentiate from calc-alkaline plutonic chambers in the final stage of the magmatism. In parallel with field relations, zircon geochronological records provide mineral-scale evidence of these magmatic processes, reflecting the zircon temperatures saturation data and interpretation.