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Boron isotope varia...
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Godoy, BenignoUniv Chile, Fac Ciencias Fis & Matemat, Dept Geol, Ctr Excelencia Geotermia Andes CEGA, Plaza Ercilla 803, Santiago, Chile.
(författare)
Boron isotope variations in a single monogenetic cone : La Poruña (21°53′S, 68°30′W), Central Andes, Chile
- Artikel/kapitelEngelska2023
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Elsevier,2023
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LIBRIS-ID:oai:DiVA.org:uu-498438
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https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-498438URI
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https://doi.org/10.1016/j.lithos.2023.107030DOI
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Språk:engelska
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Sammanfattning på:engelska
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La Poruña is a monogenetic volcano located within the Altiplano-Puna Volcanic Complex (21°-24°S) in the Central Andean subduction zone. Since crustal contamination of Andean magmas is ubiquitous, and because extensive geochemical data exist for La Poruña, we employ this volcano as a case study to examine the behavior of boron isotopes during crustal assimilation. We present whole-rock boron concentration and 11B/10B ratios (as δ11B values) for La Poruña lava samples that were prepared as nano-particulate pressed pellets. La Poruña B contents range from 14 to 20 μg/g and δ11B values range from −1.39 ± 0.54 ‰ (2σ) to +0.94 ± 0.30 ‰ (2σ), which overlap with the range of available whole-rock data for Central Andean lavas. Moreover, La Poruña δ11B values correlate negatively with 87Sr/86Sr ratios from the same samples. Since 87Sr/86Sr is a proxy for crustal contamination at La Poruña, the data lead us to suggest that La Poruña magmas assimilated a low-δ11B, high 87Sr/86Sr component such as Andean continental crust. Mixing models based on B and Sr isotopes support a broadly two-step magma evolution for La Poruña. In step 1, mantle-derived primary melts interacted with boron-rich slab-derived fluids with high δ11B values, which yielded subduction-modified parental magmas with ca. 3 μg/g B and relatively high δ11B values. In step 2, the high δ11B parental magmas ascended through the crust where they assimilated up to 20% crustal material, which further modified their δ11B values and 87Sr/86Sr ratios. In comparison to available regional values for B and δ11B, it appears that La Poruña and nearby volcanic centers shared a similar source and magmatic history, whereas volcanoes south of 23°S differ. We stress, however, that deconvolving the roles of various subduction and crustal inputs in the Central Andes would require further studies on individual volcanoes along the arc.
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Deegan, Frances M.Uppsala universitet,Naturresurser och hållbar utveckling(Swepub:uu)frade877
(författare)
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González-Maurel, OsvaldoUniv Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
(författare)
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le Roux, PetrusUniv Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
(författare)
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Garbe-Schönberg, DieterUniv Kiel, Inst Geosci, D-24118 Kiel, Germany.;Jacobs Univ Bremen, Dept Phys & Earth Sci, D-28759 Bremen, Germany.
(författare)
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Rodríguez, InésUniv Catolica Temuco, Fac Ingn, Dept Obras Civiles & Geol, Rudecindo Ortega 02950, Temuco, Chile.;Univ Catolica Temuco, Fac Ingn, Ctr Invest Evaluac Riesgos & Mitigac Peligros Geo, Geokimun, Rudecindo Ortega 02950, Temuco, Chile.
(författare)
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Guzmán-Marusic, GabrielaUniv Catolica Temuco, Fac Ingn, Ctr Invest Evaluac Riesgos & Mitigac Peligros Geo, Geokimun, Rudecindo Ortega 02950, Temuco, Chile.
(författare)
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Marín, CarolinaTeck Resources Chile Limitada, Alonso Cordova 4580,Piso 10, Santiago, Chile.
(författare)
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Univ Chile, Fac Ciencias Fis & Matemat, Dept Geol, Ctr Excelencia Geotermia Andes CEGA, Plaza Ercilla 803, Santiago, Chile.Naturresurser och hållbar utveckling
(creator_code:org_t)
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Ingår i:Lithos: Elsevier4400024-49371872-6143
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