0000000000731229
AUTHOR
P. Robidoux
Petrological and noble gas features of Lascar and Lastarria volcanoes (Chile): Inferences on plumbing systems and mantle characteristics
Lascar (5592 m a.s.l.) and Lastarria (5697 m a.s.l.) are Chilean active stratovolcanoes located in the Central Volcanic Zone (CVZ; 16°S to 28°S) that have developed on top of a 71 km thick continental crust. Independently of the similarities in their Plinian/Vulcanian eruptive styles, their complex magmatic feeding structures and the origins of their magmatic fluids still necessitate constraints in order to improve the reliability of geochemical monitoring. Here we investigate the petrography, bulk-rock chemistry, and mineral chemistry in products from the 1986–1993 explosive eruptive cycle at Lascar and from several Holocene eruptive sequences at Lastarria. These data are integrated with m…
Crustal controls on light noble gas isotope variability along the andean volcanic arc
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). Inst…