Publication Date:
2021-11-25
Description:
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.
Description:
Published
Description:
45-49
Description:
1V. Storia eruttiva
Description:
2V. Struttura e sistema di alimentazione dei vulcani
Description:
4V. Processi pre-eruttivi
Description:
JCR Journal
Keywords:
Noble gases
;
Fluid inclusions
;
Andean volcanic Arc
;
crustal contamination
;
04.08. Volcanology
;
04.01. Earth Interior
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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