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| Ziem A. Bidias, Luc Achille; Chazot, Gilles; Moundi, Amidou; Nonnotte, Philippe. |
| We investigated mafic and felsic volcanic rocks from the Bamoun plateau, a magmatic province located north of Mount Cameroon, in the continental part of the Cameroon Volcanic Line (CVL). Basalts and dacites were probably emplaced more than 40 Ma ago, while basanites represent very young volcanic eruptions. Among the basalts, some of them have suffered crustal contamination during their uprise through the continental crust, and their primary trace element and isotopic compositions have been slightly modified. The formation of the dacites was also accompanied by some crustal contamination. Non-contaminated rocks show that the oldest magmas are transitional basalts formed by relatively high degrees of partial melting of a moderately enriched mantle source,... |
| Tipo: Text |
Palavras-chave: Cameroon Volcanic Line; Geochemistry; Mantle source; Crustal contamination; Basalt. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00638/74996/75730.pdf |
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| Beaumais, Aurelien; Bertrand, Herve; Chazot, Gilles; Dosso, Laure; Robin, Claude. |
| Gaua Island (also called Santa Maria), from the central part of the Vanuatu arc, consists of a large volcano marked by a caldera that hosts the active Mount Garet summit cone. In this paper, a geochemical study including Sr, Nd, Pb and Hf isotopic compositions of 25 lavas emitted since 1.8 Ma is presented, with a focus on the volcanic products that preceded (old volcanics, main cone and pyroclastic series) and followed (Mount Garet) the caldera forming event. All lavas show an island arc signature with enrichment in LILE and depletion in HFSE. Post-caldera lavas define a medium-K calc-alkaline trend, whereas lavas from the former main cone have high-K calc-alkaline compositions. Compared to the pre-caldera volcanic suite, the Mount Garet lavas have... |
| Tipo: Text |
Palavras-chave: Gaua; Vanuatu; Geochemistry; Isotopes; Subduction; Mantle source. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00319/43052/42557.pdf |
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| Beaumais, Aurelien; Chazot, Gilles; Dosso, Laure; Bertrand, Herve. |
| Here we present a new geochemical study of Lopevi volcano, one the most active volcanoes in the Vanuatu island arc. We focus on the temporally well-defined sequence of lava flows emitted since 1960, and for the first time, on pre-1960 volcanic products, including high-MgO basalts and felsic andesites, the most evolved lavas sampled so far on this island. This work reports the first Pb and Hf isotopic study of lavas from Lopevi island. These lavas display correlations between differentiation indexes such as SiO2 content and isotopic ratios. The felsic andesites extend the known correlations with both the least (Sr-Pb) and the most (Nd-Hf) radiogenic isotopic compositions on the island. Our results confirm that the rising magma interacted with the sub-arc... |
| Tipo: Text |
Palavras-chave: Lopevi; Vanuatu; Geochemistry; Isotopes; Subduction; Mantle source. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00167/27801/26223.pdf |
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