The relationship between granites and copper occurrence in the Águas Belas pluton, PEAL domain, Borborema province: footprints of an intrusion-related mineral system?
DOI:
https://doi.org/10.51359/1980-8208.2025.268918Keywords:
intrusion-related deposit, copper, hydrothermal alteration, Borborema provinceAbstract
The study area is located northeast of the city of Águas Belas/PE, within the PEAL Terrain of the Borborema Province. It is characterized by an occurrence of copper minerals (mainly malachite) on medium- to coarse-grained igneous rocks, such as syenites, quartz-syenites, and syenogranites, composed of K-feldspar (orthoclase/microcline), plagioclase, quartz, titanite, rutile, magnetite, and biotite. Data obtained from the literature classify these rocks as metaluminous to slightly peraluminous, post-collisional, and calc-alkaline, with high-K to alkaline trace element geochemical characteristics showing high Ba, medium Sr, low Rb and HFSE, negative εNd, and Paleoproterozoic age TDM, indicating a source with a mixture of mantle and crustal components. These rocks form the Águas Belas pluton and have undergone metasomatic processes that led to the formation of veinlets and stockworks, generating a new characteristic hydrothermal mineral paragenesis. The petrographic study focused on subcentimeter veinlets (of varying compositions) and their centimeter alteration halos. The hydrothermal alterations described were propylitization, silicification, potassicization, sericitization, and sulfidation. These alterations corroborate the establishment of a metasomatic system, with mineralogy compatible with medium to low temperatures (350°C - 200°C) and a neutral to slightly acidic pH environment (4-7). The presence of chalcopyrite (primary copper mineral) and pyrite in the veinlets and alteration halos suggests that copper was carried and precipitated by the hydrothermal fluid. The lithogeochemical analysis compared unaltered rocks from the literature with rocks containing altered matrices and hydrothermally altered veinlets. Binary diagrams (Harker type) and statistical cluster analysis indicated the mobility of some chemical elements during hydrothermal alteration, with depletion in Si, Ti, and Al and enrichment in Fe, Mn, Mg, Ca, K, and P. Principal component analysis (PCA) corroborated the mobility, with hydrothermal activity (PC2) showing a positive correlation in Ca-Mn-Mg-K-Fe-P. The geological-geochemical-metallogenic context of the copper occurrence in the Águas Belas pluton, PEAL Terrain of the Borborema Province, is interpreted as similar to Intrusion-Related mineral systems associated with magmatic-hydrothermal fluids
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