Taapaca Volcanic Complex is a large dacitic volcano (35 km 3 ) located in the western border of the active zone of the Central Andes of Northern Chile. Apart from early poorly preserved silicic andesites, Taapaca Volcanic Complex has generated remarkably similar porphyritic hornblende-biotite dacites with distinctive sanidine megacrysts for at least 1.5 Ma. The main products of the volcano are dacite lavas and domes with associated block-and-ash flow deposits. There have also been several sector collapses to generate debris avalanches, which are closely associated with volcanic blasts and episodes of dome growth. Four stages of evolution are recognized with volcanism occurring in short bursts between much longer periods of dormancy. Volcanism has built a substantial stratovolcano and has migrated 4-5 km towards the SW with time. Late Pleistocene to Holocene activity has involved at least three sector collapses of the hydrothermally altered flanks and domes. Volcanic blasts, block-and-ash flows, debris avalanches and lahars have been distributed down the southwestern flanks. These areas are the main populated part of the Chilean Altiplano and the location of the main road between Bolivia and the Pacific Ocean coast. A future eruption will threaten these areas and the regional economy.
Environmental contextExplosive volcanic eruptions may have significant environmental repercussions for many Earth system cycles, particularly the water cycle. We investigate the potential contribution to local geochemical fluxes through water of five historical eruptions that occurred over a 20-year period in the Southern Andes. In all five cases, the major potentially toxic trace elements were arsenic, copper, fluoride, molybdenum, nickel, lead and zinc.
AbstractThe potential contribution to the local geochemical balance of five historical eruptions that occurred during the 20th Century has been investigated in the Southern Volcanic Zone (SVZ) of the Andean volcanic arc of South America (Lonquimay 1988, Hudson 1991, Copahue 2000, Llaima 2008, Chaitén 2008). These ashes were characterised by SEMEDX and XRD, and their potential released geochemical fluxes were examined using water and nitric acid batch leaching tests. Leachates were analysed by ICP-OES, ICP-MS and ISE. The major contents removed correspond to SO42– and Cl–. The potential toxic trace element (PTTE) content was highly variable among the ash samples following this order: Chaitén > Copahue > Hudson > Llaima > Lonquimay. The trace elements with significant load in water batch leaching tests include Fe > F > B > P > Zn > As > Mn > Sr > Ba > Ti > Cu > Ni > Li > Rb > Co > Cr > Cd > Sb. Some of these elements (As, Cu, F, Mo, Ni, Pb and Zn) are included in the drinking water guidelines due to their potential toxicity and must be especially monitored in the environmental assessment of these ashfall deposits.
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