Geochemistry and U-Pb geochronology of columbite of the Cachoeirinha Deposit, Rondônia Tin Province, Brazil
| Autor: | Raquel Guimarães da Silva, Valmir da Silva Souza, Guilherme de Oliveira Gonçalves, Luiza dos Santos Ferreira, Paulo Sérgio Mendes dos Santos Júnior |
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| Jazyk: | English<br />Spanish; Castilian<br />French<br />Portuguese |
| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Brazilian Journal of Geology, Vol 54, Iss 1 (2024) |
| Druh dokumentu: | article |
| ISSN: | 2317-4692 2317-4889 |
| DOI: | 10.1590/2317-4889202420230054 |
| Popis: | Abstract The Cachoeirinha Sn ± (Nb-Ta) deposit is an important producer of the Rondônia Tin Province. It is inserted in the regional unit named Rondônia Intrusive Suite (995–956 Ma) and hosts granular accumulations of columbite group minerals (CGM) embedded in thick Cenozoic colluvial-alluvial covers. Cachoeirinha CGM have subrounded to angular grains, with irregular to regular internal zoning, micro-inclusion, and exsolution features. They have columbite-(Fe) as the dominant mineral phase, with variation in the Ta/(Ta+Nb) ratio and with Sn, Ti, W, U, Ba, Cr, REE, and V as chemical impurities. It has high total REE content (LREEN depleted, HREEN enriched, Ce and Eu anomalies), δ18O = 2.78‰, and with two U-Pb age groups: 1052 ± 6 and 909 ± 7 Ma. This information indicates that physicochemical oscillations favored the ionic substitutions and resorption mechanisms between Nb ↔ Ta, as well as coupled substitutions with the entry of geochemical impurities, according to the equation: 3(Sn, Ti, U, Si)4+ + (W, Cr)6+ ↔ 2(V, Nb, Ta)5+ + 2(Al, REE)3+ + (Fe, Mn, Ba)2+, at the temperature range between 400° and 500°C. Finally, the Cachoeirinha Sn ± (Nb-Ta) alluvial deposit host ore is related to at least two Neo-Mesoproterozoic magmatic pulses. |
| Databáze: | Directory of Open Access Journals |
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