Negra Muerta volcanic complex

These calderas include Aguas Calientes, Cerro Panizos, Galan, Negra Muerta and La Pacana.

Negra Muerta lies on the eastern margin of the Puna and is associated with the major Calama-Olacapato-El Toro fault, [2] which was active starting from the Paleozoic.

[3] Dilatation along this fault influenced the volcanic processes at Negra Muerta[2] and other volcanoes, by opening up paths for magma ascent.

[5][6] The region has an arid climate, thus geological features are often buried beneath uneroded rocks and difficult to access.

[3] The south Central Andes in the past were the site of large scale dacitic ignimbrite-forming eruptions and the formation of calderas, linked to the interaction between a subducting slab and the overlying crust.

These were often more diverse in chemical composition than the ignimbrite forming eruptions, a property attributed to various magma processes and the interaction between the mantle and the crust.

The northern and western margin reach elevations of 5,500 metres (18,000 ft); the southern and eastern margins were lowered by glacial erosion during the Pleistocene and fluvial erosion by the Calchaqui River [es],[3] which along with some tributaries originates in the caldera and has eroded about 1,300 metres (4,300 ft) of rock.

[9] Presently, acid mine drainage occurs in the caldera through natural processes and renders the water of the Calchaquí River unsuitable for drinking.

[16] The basement of the volcano is formed by the sedimentary Salta Group of Cretaceous-Tertiary age and the below lying Cambrian Puncoviscana Formation.

It is formed by a rhyolite glass matrix containing phenocrysts made of amphibole, biotite, magnetite, plagioclase and quartz.