Sources of helium and associated heat in hydrothermal fluids from the central western branch of the East African Rift System (Democratic Republic of Congo and Burundi)
Notice bibliographique
Résumé
The area around Lake Kivu, situated in the western branch of the East African Rift System (WBEARS), which spans the Democratic Republic of Congo, Rwanda, and Burundi, is characterized in its southern part by numerous hot springs. Chemistry and isotopic signatures of hydrothermal fluids have been studied in the northern part of Lake Kivu due to the presence of one of the world's active volcanoes, Nyiragongo. However, the areas along the coast of Lake Kivu, extending south to the shores of Lake Tanganyika, where active volcanism is currently absent, have been largely overlooked, despite the presence of several tens of hydrothermal manifestations with temperatures ranging from 25 to 86 °C, located in a highly faulted region characterized by low to moderate seismicity. This study aimed to fill the gap by collecting samples from 15 hot springs, four lake waters, and one cold spring, located in the Democratic Republic of Congo and Burundi. Stable isotopes of water (δ 2 H and δ 18 O), noble gas isotopes of He, Ne, and Ar, Sr isotopic ratio ( 87 Sr/ 86 Sr), and major ions and trace elements were measured. Most water samples are classified as Na-K-HCO 3 or Ca-Mg-HCO 3 types. Stable isotopes indicate that the waters are of meteoric origin. The helium isotopic ratios ( 3 He/ 4 He or R), normalized to the atmospheric ratio (Ra = 1.384 × 10 −6 ), range from 0.058 to 1.304, indicating a dominant crustal helium source and a maximum of 13 % of mantle helium. The 87 Sr/ 86 Sr ratios range from 0.70362 in the Lac Vert sample, typical of mafic volcanic products, to 0.77520 in hot springs of the Ruzizi basin, a very radiogenic value possibly indicating water-rock interaction with the Proterozoic silicate basement of Central Africa. The 87 Sr/ 86 Sr shows a rough trend with the 40 Ar/ 36 Ar ratios, indicating a slightly detectable terrigenic 40 Ar* excess in hot spring water. These results contrast with those on the northern shore of Lake Kivu, which are characterized by magmatic helium, suggesting that moving further south, the heat is controlled by the local geothermal gradient, with fluids likely circulating deeper into the crust and warming up. This circulation is facilitated by the extensional faults of the African rift, where most of the hot springs are located. Calculated low crustal fluxes of helium in the Lake Kivu region are insufficient to create economically valuable helium reserves, as found in the southern termination of the WBEARS, in the Rukwa Rift Basin. • Thermal springs and crater lake water south of Lake Kivu were sampled for chemistry and isotopes. • Stable isotopes indicate a meteoric origin, and chemistry suggests immature waters. • The presence of little radiogenic 40 Ar* and radiogenic 87 Sr/ 86 Sr ratios suggests that fluids may circulate deep in basement rocks, heated by the local geothermal gradient. • Geothermal potential is likely restricted to low- to medium-enthalpy hydrothermal systems. • Low crustal helium fluxes in the region cannot create economically exploitable helium reserves, such as those found in the Tanzanian termination of the African Rift.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».