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Fluid geochemistry of natural manifestations from the Southern Poroto-Rungwe hydrothermal system (Tanzania): Preliminary conceptual model. (Articolo in rivista)

Type

Prodotto della ricerca (Classe)
Articolo in rivista (Classe)

Label

Fluid geochemistry of natural manifestations from the Southern Poroto-Rungwe hydrothermal system (Tanzania): Preliminary conceptual model. (Articolo in rivista) (literal)

Anno

2011-01-01T00:00:00+01:00 (literal)

Alternative label

Delalande, M. (1); Bergonzini, L. (1); Gherardi, F. (2); Guidi, M. (2); Andre L. P. (3); Abdallah, I. (4); Williamson, D. (5,6); (2011)
Fluid geochemistry of natural manifestations from the Southern Poroto-Rungwe hydrothermal system (Tanzania): Preliminary conceptual model.
in Journal of volcanology and geothermal research; Elsevier BV, Amsterdam (Paesi Bassi)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Delalande, M. (1); Bergonzini, L. (1); Gherardi, F. (2); Guidi, M. (2); Andre L. P. (3); Abdallah, I. (4); Williamson, D. (5,6); (literal)

Pagina inizio

127 (literal)

Pagina fine

141 (literal)

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ID_PUMA: /cnr.igg/2011-A0-031.Area di valutazione04 - Scienze della Terra (literal)

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http://scienceserver.cilea.it/cgi-bin/sciserv.pl?collection=journals&journal=03770273 (literal)

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199 (literal)

Rivista

Journal of volcanology and geothermal research (Rivista)

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1-2 (literal)

Note

ISI Web of Science (WOS) (literal)

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(1) Univ Paris 11, IDES, CNRS, UMR 8148, F-91405 Orsay, France; (2) IGG, I-56124 Pisa, Italy ; (3) Royal Museum Cent Africa, Dept Geol & Mineral, B-3080 Tervuren, Belgium; (4) Univ Dar Es Salaam, IRA, Dar Es Salaam, Tanzania; (5) Univ Paul Cezanne, CNRS, UMR 6635, CEREGE, F-13545 Aix En Provence 04, France; (6) World Agroforestry Ctr ICRAF, LOCEAN, UMR 7159, IRD, Nairobi, Kenya (literal)

Titolo

Fluid geochemistry of natural manifestations from the Southern Poroto-Rungwe hydrothermal system (Tanzania): Preliminary conceptual model. (literal)

Abstract

The South Poroto-Rungwe geothermal field, in the northern part of the Malawi rift, Tanzania divides in two main areas. The relatively high altitude northern area around the main Ngozi, Rungwe, Tukuyu and Kyejo volcanoes, is characterised by cold and gas-rich springs. In contrast, hot springs occur in the southern and low-altitude area between the Kyela and Livingstone faults. The isotopic signature of the almost stagnant, cold springs of the Northern district is clearly influenced by H2O-CO2(g) exchange as evidenced from negative oxygen-shifts in the order of few deltas permil. In contrast, the isotopic signature of waters discharged from the hot springs of the Southern district is markedly less affected by the H2O-CO2(g) interaction. This evidence is interpreted as an effect of the large, permanent outflow of these springs, which supports the hypothesis of a regional-scale recharge of the major thermal springs. Measurements of carbon isotope variations of the dissolved inorganic carbon of waters and CO2(g) from the Northern and Southern springs support a model of CO2(g)-driven reactivity all over the investigated area. Our combined chemical and isotopic results show that the composition of hot springs is consistent with a mixing between (i) cold surface fresh (SFW) and (ii) Deep Hot Mineralised (DHMW) Water, indicating that the deep-originated fluids also supply most of the aqueous species dissolved in the surface waters used as local potable water. Based on geothermometric approaches, the temperature of the deep hydrothermal system has been estimated to be higher than 110°C up to 185°C, in agreement with the geological and thermal setting of the Malawi rift basin. Geochemical data point to (i) a major upflow zone of geothermal fluids mixed with shallow meteoric waters in the Southern part of the province, and (ii) gas absorption phenomena in the small, perched aquifers of the Northern volcanic highlands. (literal)

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