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| Calama-Olacapato-El Toro fault system | |
|---|---|
| Name | Calama-Olacapato-El Toro fault system |
| Location | Antofagasta Region, Salta Province, Jujuy Province, Catamarca Province |
| Length | ~500 km |
| Type | Strike-slip, normal, reverse |
Calama-Olacapato-El Toro fault system is a major trans-Andean structural corridor that trends north–south across the southern Atacama Desert and northern Argentina, linking lithospheric deformation between the Central Volcanic Zone and the Puna Plateau. The system juxtaposes crustal domains related to the Nazca Plate subduction beneath the South American Plate, and it connects volcanic, geothermal and mining districts including El Tatio, Salar de Atacama, and the Lithium triangle. It has been a focus of multidisciplinary studies involving stratigraphy, structural geology, geochronology and geophysics conducted by groups from institutions such as the Servicio Nacional de Geología y Minería de Chile, Instituto de Geología y Recursos Minerales (Argentina), and international teams.
The fault system comprises a linked array of major strike-slip and oblique structures that extend from near Calama in northern Chile through the Puna de Atacama into northwestern Argentina, influencing sedimentary basins like the Salar de Uyuni basin and volcanic chains such as the Altiplano-Puna volcanic complex. Its paleotectonic role ties to episodes recorded in regional units including the Tertiary volcanic successions, Miocene ignimbrites, and the uplift history of the Andes. The corridor interacts with economic provinces exploited by Antofagasta PLC, Yamana Gold, and other mining operators for metals and lithium resources.
The fault system occupies the eastern margin of the Atacama Plateaus and western fringes of the Puna Plateau, within the tectonic framework produced by convergence between the Nazca Plate and the South American Plate. It transects crustal terranes such as the Arequipa-Antofalla and Cuyania blocks and crosses major lithologies including Permian to Cenozoic volcanosedimentary sequences like the Choiyoi Group and Paleozoic basement. Regional shortening related to the Andean orogeny, slab flattening events tied to the Nazca Ridge and the Juan Fernández Ridge, and back-arc extension produce conditions that localize deformation along this corridor, comparable to other trans-Andean features like the Mendoza lineament and the Liquiñe-Ofqui Fault Zone.
The system is segmented into discrete fault strands and geometric features: major N–S trending strike-slip segments, oblique-normal splays, pull-apart basins, and restraining bends that control the distribution of basins like the Antofagasta Basin and Coipasa Basin. Prominent segments include the Calama, Olacapato and El Toro strands, which link via transfer zones and stepovers that accommodate variable slip partitioning between dextral strike-slip motion and normal faulting. Structural studies integrate field mapping of fault gouge and slickensides, correlations with regional markers such as the Purico Complex ignimbrites, and aeromagnetic lineaments matched to crustal models from the Seismological Society of America datasets.
Evolution of the corridor reflects Mesozoic to Cenozoic deformation: Mesozoic extension related to the Gondwana breakup provided basement inheritance, while Cenozoic continental-scale shortening and later Miocene-Pliocene extension produced reactivation and strike-slip localization. Key pulses correspond to regional events such as the Incaic orogeny and the Altiplano uplift during the Neogene, with timing constrained by radiometric methods applied to volcanic and sedimentary units like 40Ar/39Ar and U-Pb zircon ages. Thermochronology, including fission track and (U-Th)/He studies, documents exhumation related to fault-controlled uplift and basin subsidence.
The fault corridor spatially correlates with volcanic centers of the Central Volcanic Zone including stratovolcanoes and extensive ignimbrite sheets from the Altiplano-Puna volcanic complex. Fault-controlled magma ascent produced alignments of centers such as Licancabur, Sairecabur, and other Andean edifices, and it influences geothermal manifestations at fields like El Tatio and Termas de Pujsa. Geochemical signatures from volcanic rocks reflect mantle and crustal components studied by laboratories at Universidad de Chile and CONICET, linking magmatism to slab dynamics and crustal thickness variations.
Although the corridor is less seismically active than the volcanic arc itself, it has produced significant earthquakes and aseismic creep recorded by GPS networks, paleoseismology trenching, and historical catalogs maintained by Instituto Geográfico Nacional (Argentina) and Servicio Sismológico de la Universidad de Chile. Fault-related surface rupture, ground subsidence in salt pans like the Salar de Atacama, and geothermal hazards pose risks to infrastructure including mining operations, high-voltage transmission lines, and road corridors such as the Pan-American Highway. Hazard assessments combine seismotectonic models, probabilistic seismic hazard analysis, and remote sensing from platforms like Landsat and Sentinel-1.
Investigation of the system dates to regional geological surveys in the mid-20th century by institutions such as the Servicio Nacional de Geología y Minería de Chile and Argentine geological services, followed by integrated academic work from universities including Universidad Nacional de Salta, Universidad Nacional de San Juan, and international collaborations with the Smithsonian Institution and the US Geological Survey. Modern approaches employ field structural mapping, geochronology, geochemistry, seismic reflection and refraction, magnetotellurics, aeromagnetics, satellite geodesy, and numerical modeling. Ongoing research addresses strike-slip kinematics, crustal rheology, geothermal potential, and implications for resource distribution in the Lithium triangle and associated mining districts.
Category:Geology of Chile Category:Geology of Argentina Category:Seismic faults