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Boron isotope varia...
Boron isotope variations in a single monogenetic cone : La Poruña (21°53′S, 68°30′W), Central Andes, Chile
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- Godoy, Benigno (author)
- Univ Chile, Fac Ciencias Fis & Matemat, Dept Geol, Ctr Excelencia Geotermia Andes CEGA, Plaza Ercilla 803, Santiago, Chile.
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- Deegan, Frances M. (author)
- Uppsala universitet,Naturresurser och hållbar utveckling
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- González-Maurel, Osvaldo (author)
- Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
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- le Roux, Petrus (author)
- Univ Cape Town, Dept Geol Sci, ZA-7700 Rondebosch, South Africa.
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- Garbe-Schönberg, Dieter (author)
- Univ Kiel, Inst Geosci, D-24118 Kiel, Germany.;Jacobs Univ Bremen, Dept Phys & Earth Sci, D-28759 Bremen, Germany.
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- Rodríguez, Inés (author)
- Univ 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.
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- Guzmán-Marusic, Gabriela (author)
- Univ Catolica Temuco, Fac Ingn, Ctr Invest Evaluac Riesgos & Mitigac Peligros Geo, Geokimun, Rudecindo Ortega 02950, Temuco, Chile.
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- Marín, Carolina (author)
- Teck Resources Chile Limitada, Alonso Cordova 4580,Piso 10, Santiago, Chile.
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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)
- Elsevier, 2023
- 2023
- English.
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In: Lithos. - : Elsevier. - 0024-4937 .- 1872-6143. ; 440
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Abstract
Subject headings
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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.
Subject headings
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
Keyword
- Central Andes
- La Poruna
- Boron isotopes
- Crustal assimilation
Publication and Content Type
- ref (subject category)
- art (subject category)
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