Tocorpuri
Cerros de Tocorpuri is a volcanic complex located along the border between Bolivia and Chile.
Volcan Tocorpuri is constructed by andesitic lava flows with some pyroclastics, which form a high pile with a wide summit crater. After this edifice was built, several vents developed on its northwestern flank and south of the summit crater. These vents produced dominantly andesitic lava flows. The southeastern flank of the main Tocorpuri volcano shows evidence of a sector collapse.
On its west side lies a rhyolite lava dome called Cerro La Torta. Its steep sides are surrounded with talus and its top surface has flow structures.
The complex is located at about 30 km. from the El Tatio geothermal energy field.
Volcanism along the Andes occurs in four separate belts, the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone. Tocorpuri is part of the Central Volcanic Zone, which in this region is characterized by an ignimbrite formation and individual volcanoes, with compositions ranging from andesite over dacite to rhyolite. Both these formations are emplaced on a Cretaceous-Miocene basement formed by sediments and volcanic rocks, which overlay Precambrian-Paleozoic layers. Aside from stratovolcanoes which are lined up in the Western Cordillera, the Altiplano-Puna volcanic complex is also a component of the Central Volcanic Zone and is formed by large calderas and lava domes such as La Torta.
Of those units of Tocorpuri that have been sampled, most are andesitic with phenocrysts of amphibole, biotite, pyroxene and quartz. La Torta also has phenocrysts of sanidine and additional apatite and titanite.
The main Tocorpuri volcano is partly covered by the Tatio ignimbrite, which is about 800,000 years old. The Torta lava dome was erupted within the last 100,000 years. The Tocorpuri complex has been affected by glaciation during the Pleistocene.
The area north of La Torta is also the site of a hydrothermal system at an elevation of which emit calcium sulfate rich water. These hot springs and associated gases are principally low temperature atmospheric systems, with the average temperature not exceeding and a high proportion of atmospheric gases. Presumably, ascending hydrothermal fluids interact with a thick precipitation-fed aquifer before emerging.
