Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago

Bibliographic Details
Main Author: Madureira, Pedro
Publication Date: 2008
Other Authors: Mata, João, Mattielli, Nadine, Queiroz, Gabriela
Format: Article
Language: eng
Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Download full: http://hdl.handle.net/10174/2445
Summary: Terceira Island mafic lavas (< 30 ka), erupted from two main active volcanic systems, were analysed in this study: Fissural zone (F), interpreted as the sub aerial expression of the Terceira Rift, and Sta Bárbara central volcano (SB), which dominates the western topography of the island. These mafic lavas present a significant elemental range, with SB (Mg# <50) being generally more evolved than F (typically Mg# >50). However, if fractional crystallization explains the intra-system variability, it cannot be considered responsible for some chemical differences between those 2 volcanic systems. This is clearly demonstrated by distinct Ba/Th (200 vs. 80), Ce/Th (35 vs. 25) and 206Pb/204Pb ratios (19.93 – 19.99 vs. 19.34 -19.85), which clearly point to a heterogeneous mantle source. Terceira magmas formed from sources characterized by time-integrated depletion (εNd: 5.4 to 6.4; εHf: 7.7 to 10.7) significantly more marked than the observed for coeval lavas outcropping in the neighbouring islands of Pico and S. Miguel, the later also formed in relation with the Terceira Rift. In opposition Terceira is characterized by more radiogenic Pb isotopic ratios indicating a stronger HIMU presence at its source. From elemental reasoning, SB magmas were generated by lower % of partial melting being also characterized by higher 206Pb/204Pb ratios. This indicates that the HIMU domains of mantle source were preferentially sampled during the lower degree melting events. Considering the positioning of Terceira samples below the NHRL and the negative correlation between Nb/U and 206Pb/204Pb, the development of HIMU signatures is a relatively recent event. Our data strengthen the heterogeneous character of the sub-Azores mantle, which is evident even when mantle is sampled along the same structure (Terceira Rift) and, also, at the scale of an individual island.
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spelling Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores ArchipelagoMantle heterogeneityTerceira IslandTerceira Island mafic lavas (< 30 ka), erupted from two main active volcanic systems, were analysed in this study: Fissural zone (F), interpreted as the sub aerial expression of the Terceira Rift, and Sta Bárbara central volcano (SB), which dominates the western topography of the island. These mafic lavas present a significant elemental range, with SB (Mg# <50) being generally more evolved than F (typically Mg# >50). However, if fractional crystallization explains the intra-system variability, it cannot be considered responsible for some chemical differences between those 2 volcanic systems. This is clearly demonstrated by distinct Ba/Th (200 vs. 80), Ce/Th (35 vs. 25) and 206Pb/204Pb ratios (19.93 – 19.99 vs. 19.34 -19.85), which clearly point to a heterogeneous mantle source. Terceira magmas formed from sources characterized by time-integrated depletion (εNd: 5.4 to 6.4; εHf: 7.7 to 10.7) significantly more marked than the observed for coeval lavas outcropping in the neighbouring islands of Pico and S. Miguel, the later also formed in relation with the Terceira Rift. In opposition Terceira is characterized by more radiogenic Pb isotopic ratios indicating a stronger HIMU presence at its source. From elemental reasoning, SB magmas were generated by lower % of partial melting being also characterized by higher 206Pb/204Pb ratios. This indicates that the HIMU domains of mantle source were preferentially sampled during the lower degree melting events. Considering the positioning of Terceira samples below the NHRL and the negative correlation between Nb/U and 206Pb/204Pb, the development of HIMU signatures is a relatively recent event. Our data strengthen the heterogeneous character of the sub-Azores mantle, which is evident even when mantle is sampled along the same structure (Terceira Rift) and, also, at the scale of an individual island.Elsevier2011-01-13T16:29:55Z2011-01-132008-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/article2258945 bytesapplication/pdfhttp://hdl.handle.net/10174/2445http://hdl.handle.net/10174/2445engGeochimica et Cosmochimica ActalivreDepartamento de Geociênciaspedro@uevora.ptjmata@fc.ul.ptnmattiel@ulb.ac.bemaria.gp.queiroz@azores.gov.pt396Madureira, PedroMata, JoãoMattielli, NadineQueiroz, Gabrielainfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-01-03T18:38:49Zoai:dspace.uevora.pt:10174/2445Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T00:58:05.828165Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
title Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
spellingShingle Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
Madureira, Pedro
Mantle heterogeneity
Terceira Island
title_short Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
title_full Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
title_fullStr Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
title_full_unstemmed Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
title_sort Terceira lavas isotopic sigantures and multi-scale mantle heterogeneity at the Azores Archipelago
author Madureira, Pedro
author_facet Madureira, Pedro
Mata, João
Mattielli, Nadine
Queiroz, Gabriela
author_role author
author2 Mata, João
Mattielli, Nadine
Queiroz, Gabriela
author2_role author
author
author
dc.contributor.author.fl_str_mv Madureira, Pedro
Mata, João
Mattielli, Nadine
Queiroz, Gabriela
dc.subject.por.fl_str_mv Mantle heterogeneity
Terceira Island
topic Mantle heterogeneity
Terceira Island
description Terceira Island mafic lavas (< 30 ka), erupted from two main active volcanic systems, were analysed in this study: Fissural zone (F), interpreted as the sub aerial expression of the Terceira Rift, and Sta Bárbara central volcano (SB), which dominates the western topography of the island. These mafic lavas present a significant elemental range, with SB (Mg# <50) being generally more evolved than F (typically Mg# >50). However, if fractional crystallization explains the intra-system variability, it cannot be considered responsible for some chemical differences between those 2 volcanic systems. This is clearly demonstrated by distinct Ba/Th (200 vs. 80), Ce/Th (35 vs. 25) and 206Pb/204Pb ratios (19.93 – 19.99 vs. 19.34 -19.85), which clearly point to a heterogeneous mantle source. Terceira magmas formed from sources characterized by time-integrated depletion (εNd: 5.4 to 6.4; εHf: 7.7 to 10.7) significantly more marked than the observed for coeval lavas outcropping in the neighbouring islands of Pico and S. Miguel, the later also formed in relation with the Terceira Rift. In opposition Terceira is characterized by more radiogenic Pb isotopic ratios indicating a stronger HIMU presence at its source. From elemental reasoning, SB magmas were generated by lower % of partial melting being also characterized by higher 206Pb/204Pb ratios. This indicates that the HIMU domains of mantle source were preferentially sampled during the lower degree melting events. Considering the positioning of Terceira samples below the NHRL and the negative correlation between Nb/U and 206Pb/204Pb, the development of HIMU signatures is a relatively recent event. Our data strengthen the heterogeneous character of the sub-Azores mantle, which is evident even when mantle is sampled along the same structure (Terceira Rift) and, also, at the scale of an individual island.
publishDate 2008
dc.date.none.fl_str_mv 2008-01-01T00:00:00Z
2011-01-13T16:29:55Z
2011-01-13
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dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv Geochimica et Cosmochimica Acta
livre
Departamento de Geociências
pedro@uevora.pt
jmata@fc.ul.pt
nmattiel@ulb.ac.be
maria.gp.queiroz@azores.gov.pt
396
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