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http://hdl.handle.net/2122/14901
Authors: | Lages, Joao* Rizzo, Andrea Luca* Aiuppa, Alessandro* Robidoux, Philippe* Aguilar, R* Apaza, Fredy* Masias, Pablo* |
Title: | Crustal controls on light noble gas isotope variability along the Andean Volcanic Arc | Journal: | Geochemical Perspectives Letters | Series/Report no.: | /19 (2021) | Publisher: | EUROPEAN ASSOC GEOCHEMISTRY | Issue Date: | 2021 | DOI: | 10.7185/geochemlet.2134 | Keywords: | Noble gases Fluid inclusions Andean volcanic Arc crustal contamination |
Subject Classification: | 04.08. Volcanology 04.01. Earth Interior |
Abstract: | This study combines new noble gas data from fluid inclusions in minerals from Sabancaya, Ubinas, and El Misti (CVZ, Peru) and Villarica (South Chile, SVZ) with a revised noble gas compilation in the Andes, to identify systematic along arc variations in helium isotope compositions. We find 3He/4He ratios varying from 8.8 RA (Colombia) to 7.4 RA (Ecuador) within the NVZ, and only as high as 6.4 RA in the CVZ (RA is the atmospheric 3He/4He ratio of 1.39 × 10–6). These distinct isotope compositions cannot be explained by variable radiogenic 4He production via slab fluid transport of U and Th in the mantle wedge, since both NVZ and CVZ share similar slab sediment inputs (Th/La ≈ 0.08–0.13). Instead, the progressively more radiogenic 3He/4He signatures in Ecuador and Peru reflect 4He addition upon magma ascent/storage in the crust, this being especially thick in Peru (>70 km) and Ecuador (>50 km) relative to Colombia (∼30–45 km). The intermediate compositions in the North (8.0 RA) and South (7.9 RA) Chile, both high sediment flux margins, mostly reflect a more efficient delivery of radiogenic He in the wedge from the subducted (U-Th-rich) terrigenous sediments. Our results bring strong evidence for the major role played by crustal processes in governing noble gas compositions along continental arcs. |
Appears in Collections: | Article published / in press |
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Lages et al., 2021b.pdf | Open Access published article | 4.35 MB | Adobe PDF | View/Open |
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