Geochemical and isotopic constraints on the host rocks of the magmatic-hydrothermal Coringa gold-silver (Cu–Pb–Zn) deposit of the Tapajós mineral province, amazonian craton, Brazil

Abstract

The Coringa gold-silver (Cu–Pb–Zn) deposit, in southeastern Tapajós Mineral Province, is hosted in felsic volcanic rocks of the Vila Riozinho Formation and the Serra Alkali Feldspar Granite (hereafter Serra Granite). Field, petrographic, geochemical, and U–Pb, Lu–Hf, Sm–Nd data allowed us to constrain the magmatic evolution and tectonic setting of these units and surrounding volcano-plutonic sequences, with bearing in the tectonic evolution of the Tapajós Province, and the Amazonian Craton.The granites of the Creporizão Intrusive Suite (1956–2002 Ma) are high-K, calc-alkalic to alkali-calcic (subalkaline), metaluminous, and magnesian. The Serra Granite (1968–2020 Ma) is alkali-calcic and ferroan, with moderate to strongly negative εNd values (−8.0 to + 0.1), and model ages of 2.27–3.15 Ga, the same range of those presented by the intrusions of the Creporizão Suite, with Serra Granite being interpreted as a differentiated variety of the Creporizão Suite. Volcanic and pyroclastic rocks of the Vila Riozinho Formation (1996–2033 Ma) are high-K, calc-alkaline and magnesian, whereas the predominant “magnetic pyroclastic facies” of this formation is mostly ferroan alkalic (relatively reduced crystallization conditions). Despite the chemical difference, the magnetic pyroclastic facies, dated at 2024 to 1968 Ma, is similar in age to the “normal” Vila Riozinho Formation. The Nd–Hf isotopes reveal model ages between 2.38 and 2.42 Ga, and εHf and εNd values ranging from −2.1 to −3.2, which are very similar to those of the “normal” Vila Riozinho Formation (Sm–Nd TDM = 2.49–2.25 Ga, epsilon values of −3.71 to −1.03). The Maloquinha Intrusive Suite, which intruded older units, shows alkali-calcic to alkali and ferroan signature, along with trace-element distribution typical of silica saturated alkaline granites and was dated at 1883 ± 17 Ma.The geochemical and isotopic signature of the coeval Creporizão Suite and Vila Riozinho Formation indicate that they belong to the same Orosirian magmatic event. Considering the age relationships with precedent magmatic events in the Tapajós Mineral Province, attributed to arc setting, we interpret this event as post-collisional, with the collision assemblages occurring outside the Tapajós Province, in the Guiana Shield, as part of a large Orosirian orogenic belt. The Maloquinha Suite is associated with the Uatumã silicious large igneous province (~1.89–1.86 Ga), which was established in a craton-wide extensional event that followed the Orosirian orogeny.