Hydrochemical controls on tufa deposition in drainages in Serra do André Lopes (SP, Brazil)
The André Lopes Mountain Range is located in a karst plateau composed of dolomites (Tapagem Marble) in the state of São Paulo, Brazil. On the surface, the water that flows over the carbonate rocks is rich in calcium carbonate, which enables the deposition of tufa. For tufa deposition to occur, the w...
| Autores: | , , |
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| Tipo de documento: | artigo |
| Estado: | Versão publicada |
| Data de publicação: | 2024 |
| País: | Brasil |
| Recursos: | Universidade de São Paulo (USP) |
| Repositório: | Geologia USP. Série Científica (Online) |
| Idioma: | português |
| OAI Identifier: | oai:revistas.usp.br:article/225300 |
| Acesso em linha: | https://revistas.usp.br/guspsc/article/view/225300 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Continental carbonates Tufa Karst Hydrochemistry Isotopes André Lopes Mountain Range Carbonatos continentais Carste Hidroquímica Isótopos Serra do André Lopes |
| Resumo: | The André Lopes Mountain Range is located in a karst plateau composed of dolomites (Tapagem Marble) in the state of São Paulo, Brazil. On the surface, the water that flows over the carbonate rocks is rich in calcium carbonate, which enables the deposition of tufa. For tufa deposition to occur, the water must be crystal clear, without suspended sediments that could inhibit the precipitation of carbonates, and have a high concentration of dissolved calcium carbonate. River water samples were collected in 14 locations in Serra do André Lopes and the region, for the analysis of various hydrochemical and isotopic parameters. Hydrochemical analysis showed that the waters have a high content of calcium carbonate (average of 179 mg/l), a high Mg/Ca ratio (average of 0.88) and high pH values (between 8.18 and 8.71) and saturation index values with respect to calcite (between 0.1 and 1.04). Most of the waters were classified as calcic-magnesian carbonated. Based on the results, it was possible to conclude that the waters from the drainages where tufa deposits occur are derived from autogenic recharge, with little or no influence from allogenic waters (from non-carbonate areas), being the predominant factor for tufa deposition in the region. The results of isotopic analysis of water d18O and calcium carbonate from tufa showed that the influence of evaporation is practically null in calcite precipitation. The observation of isotopically equilibrated tufa deposition shows that potential paleoclimatic records obtained from ancient deposits are relevant. |
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