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A review of geochemical evolution and mineralization events in A-type granites of the Rondônia tin province, Amazonian Craton

2023; Elsevier BV; Volume: 133; Linguagem: Inglês

10.1016/j.jsames.2023.104732

1873-0647

Eduarda Carvalho de Almeida, Marcelo Garcia Galé, M.V.N. De Souza, Marize Muniz da Silva,

Geochemistry and Elemental Analysis

The Rondônia Tin Province, situated in the southwestern part of the Amazonian Craton in Brazil, is renowned for hosting the country's largest cassiterite deposits and substantial mineral reserves of Sn, Nb, Ta, and W, primarily found in A-type rapakivi granites. Despite its significance, this area lacks comprehensive regional studies. Over time, the province has undergone a series of post-tectonic to anorogenic magmatic events, resulting in the formation of several intrusive suites: Serra da Providência (1.60–1.53 Ga), Santo Antônio (1.40 Ga), Teotônio (1.39 Ga), Alto Candeias (1.35–1.34 Ga), São Lourenço-Caripunas (1.31 Ga), Santa Clara (1.08–1.07 Ga), and Rondônia (1.00–0.97 Ga). These suites typically exhibit high-K calc-alkaline to alkaline affinity, often leaning towards shoshonitic compositions. They are primarily ferroan, varying from metaluminous to peraluminous, and weakly peralkaline. Notably, they display enrichments in large ion lithophile elements and light rare earth elements (LREE), along with depletion of heavy rare earth elements, marked by a strong negative Eu anomaly. Based on Rb–Ba–Sr content, the older suites—Serra da Providência, Santo Antônio, Teotônio, and Alto Candeias—show normal granite signatures. In contrast, the younger tin-bearing rocks—Santa Clara, São Lourenço-Caripunas, and Rondônia—demonstrate highly evolved geochemical characteristics. Tectonic discrimination diagrams position the older suites within the post-collisional field, while the younger, mineralized suites exhibit intraplate characteristics. This study integrates compiled geochemical, geochronological, and isotope data from various studies to comprehensively delineate the regional tectono-magmatic framework evolution of the Rondônia Tin Province. Notably, it suggests a potential equivalence between the Santo Antônio and Teotônio suites, highlighting their geochemical similarities, overlapping ages, and geographical proximity. The analysis uncovers that tin mineralization in this province arose from at least two distinct tectonic events linked to intrusions of alkaline granites displaying intraplate affinity. These granites crystallized post the cessation of compressive forces from the Rondonian-San Ignacio (ca. 1.3 Ga) and Sunsás (ca. 1.0 Ga) orogenies. The São Lourenço-Caripunas Suite marks the initial mineralizing event, while the mineralized Santa Clara and Rondônia suites align with a subsequent tectonic cycle. Hydrothermal activities in greisen deposits within the Rondônia Tin Province intricately link to younger evolved suites characterized by heightened Sr ratios, implying unique potential for ore formation during anorogenic stages. Tectonic events significantly drive tin mineralization, recurring during anorogenic episodes at the conclusion of each orogenic cycle. These mineralizations reflect the phases of anorogenic magmatism, notably in the closing stages of the Rondonian-San Ignacio (∼1.3 Ga) and Sunsás (∼1.0 Ga) orogenies. This study offers crucial insights into the geological evolution and tin mineralization processes within the Rondônia Tin Province, contributing to the global understanding of similar geological settings and guiding effective exploration strategies for the region. The dataset provides a robust foundation for future research and underscores the province's potential for further discoveries.