Origin of native copper in the Paraná volcanic province, Brazil, integrating Cu stable isotopes in a multi-analytical approach

Different hypotheses exist on the origin of native copper mineralization in the Parana volcanic province that invoke magmatic, late magmatic, or hydrothermal events. The average copper content in the host basalts is ~200 ppm. Native copper occurs as dendrites in cooling joints, fractures, and cavities within amygdaloidal crusts. Cuprite, tenorite, chrysocolla, malachite, and azurite occur in breccias at the top of the lava flows. Chemical analyses, X-ray diffraction, Raman spectrometry, electron microprobe analyses, LA-ICP-MS, and Cu isotope analyses were used to evaluate the origin of native copper in the volcanic province. Copper contents in magnetite of the host basalt are close to 1 wt.%, whereas clinopyroxene contains up to 0.04 wt.% Cu. Cretaceous hydrothermal alteration of magnetite and clinopyroxene released copper to generate hydrothermal copper mineralization. The isotopic composition of the native copper in the Parana volcanic province varies from −0.9‰ in the southeastern portion (Rio Grande do Sul state) to 1.9‰ in the central portion (Parana state) of the province. This study supports a hydrothermal origin followed by supergene enrichment for native copper in the Parana volcanic province.