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| Cerro Guacha | |
|---|---|
| Name | Cerro Guacha |
| Elevation m | 5939 |
| Range | Andes |
| Location | Potosí Department, Bolivia |
| Type | Caldera |
| Last eruption | Pleistocene |
Cerro Guacha is a large volcanic caldera in the Bolivian Altiplano known for one of the most voluminous ignimbrite eruptions of the Central Andes. The feature lies within a regional tectonic and magmatic province that includes numerous calderas, stratovolcanoes, and volcanic fields, and it has been the focus of volcanological, petrological, and geochemical studies. Cerro Guacha’s eruptions and associated hydrothermal systems have influenced mineralization, landscape evolution, and modern research into magmatic processes.
Cerro Guacha is situated in the southwestern Altiplano near the border of the Potosí Department and within the greater Andes mountain system, proximal to the Salar de Uyuni, Salar de Coipasa, and the Tatio geothermal region. The caldera is part of the Central Volcanic Zone of the Andean Volcanic Belt, lying north of the Lipez range and west of the city of Potosí. Nearby volcanic centers include Tunupa, Sajama, Licancabur, Salar de Uyuni volcanic field, and the Los Frailes complex, and it is connected by regional faults such as the Vilama fault and tectonic features related to the Nazca Plate subduction under the South American Plate. The setting is characterized by high plateau topography, salt flats, and sparse settlements including indigenous communities associated with Altiplano cultural regions.
Cerro Guacha lies within a complex of nested calderas, resurgent domes, and ring-fracture systems related to repeated large-volume silicic eruptions similar to other Central Andes calderas such as La Pacana and Vilama. The structural framework incorporates radial and concentric faulting, ignimbrite sheets, and welded tuffs deposited over a broad basin created during the Neogene and Pleistocene. The caldera’s margins interact with regional structures tied to the Altiplano–Puna plateau uplift and the magmatic arc influenced by the subduction of the Nazca Plate beneath the South American Plate, producing crustal thickening and ignimbrite flare-up episodes comparable to those at Cerro Panizos and Oruro volcanic centers.
Eruptive history includes at least two major ignimbrite-forming events in the Late Miocene to Pleistocene, generating extensive ash-flow sheets correlated with deposits across the Altiplano and into neighboring provinces. These eruptions produced voluminous welded tuffs and pumice falls that match stratigraphic sequences studied alongside units from La Pacana, Vilama, Socompa, and Galán calderas. Tephrochronological work links Cerro Guacha deposits with regional markers used in studies of Pleistocene stratigraphy, and radiometric dating by groups working with institutions such as the Smithsonian Institution, University of Buenos Aires, and Universidad Mayor de San Andrés has constrained eruption ages. Post-caldera volcanism includes rhyodacitic domes and lava flows analogous to extrusions at San Pedro and dome complexes at Purico Complex.
Rocks from Cerro Guacha range from high-silica rhyolites to dacites and andesites, with mineral assemblages including sanidine, biotite, amphibole, and zircon consistent with evolved magmas. Geochemical signatures show high-alkali and peraluminous trends typical of Central Andes ignimbrites, with trace-element ratios and isotopic compositions reflecting crustal assimilation and fractional crystallization processes similar to those documented at La Pacana, Galán, and Cerro Panizos. Studies incorporating whole-rock major-element, trace-element, and Sr–Nd–Pb isotope data conducted by collaborations between CONICET, Servicio Geológico Minero, and international laboratories indicate contributions from lower crustal melting and mantle-derived melts modified by continental crust, paralleling models proposed for the Altiplano–Puna magmatic complex.
Hydrothermal alteration around Cerro Guacha produced silicification, argillic alteration, and sulfide-bearing veins that have implications for epithermal and porphyry-style mineralization investigated in the context of Bolivian mining districts such as Potosí and Oruro. Geothermal manifestations and paleohydrothermal deposits show similarities to active systems at El Tatio, Ollagüe, and deposits studied at Cerro Rico and San Cristóbal mine, with hydrothermal fluids likely driven by residual magmatic heat following caldera-forming events. Exploration by mining entities and geological surveys has documented hydrothermal alteration halos, advanced argillic zones, and clay-rich cap rocks that are comparable to known precious- and base-metal systems in the Central Andes.
Cerro Guacha has been the subject of multidisciplinary research involving geological mapping, geochronology, geochemistry, and geophysics performed by institutions including Universidad Nacional de Salta, Universidad Mayor de San Andrés, Universidad de Chile, and international teams from USGS, CEFREM, and university research groups. Archaeological and ethnographic studies in the Altiplano intersect with research on human use of high-elevation landscapes near sites associated with Inca and pre-Inca cultures, trade routes connecting Tiwanaku, Pukara, and other highland centers, and colonial mining activities centered on Potosí (city). Geological field campaigns have contributed tephrostratigraphic markers applied in Quaternary studies and paleoclimate reconstructions used by researchers at Max Planck Institute for Chemistry and regional climatology groups.
The high-elevation environment around Cerro Guacha supports puna grasslands, salt flat ecosystems like the Salar de Uyuni habitat, and faunal assemblages including vicuña and Andean waterfowl studied by biologists from Universidad Mayor de San Andrés and conservation organizations active in the Altiplano. Volcanic deposits have influenced soil development, groundwater flow, and hydrology affecting wetlands and endorheic basins linked to Lake Poopó and the broader Altiplano hydrological network. Paleoclimatic impacts of eruptions are considered in regional records of Pleistocene glaciation and Holocene environmental change analyzed by teams at National Autonomous University of Mexico, University of Cambridge, and Smithsonian Tropical Research Institute.
Category:Volcanoes of Bolivia Category:Calderas