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| Arequipa-Antofalla Block | |
|---|---|
| Name | Arequipa-Antofalla Block |
| Type | Crustal block |
| Region | Central Andes |
| Countries | Peru, Bolivia, Argentina |
| Coordinates | 18°S 68°W |
| Age | Precambrian–Phanerozoic |
| Lithology | Metamorphic basement, granitoids, sedimentary cover |
| Notes | Tectonostratigraphic terrane within Andean orogen |
Arequipa-Antofalla Block is a continental crustal block in the central Andes situated beneath parts of Peru, Bolivia, and Argentina. It forms a key component of Andean tectonics influencing the Altiplano, Eastern Cordillera, and depositional basins such as the Puna Plateau and the Salta Basin. The block's interactions with the Nazca Plate, South American Plate, and surrounding terranes have controlled magmatism related to the Central Volcanic Zone, orogenic uplift exemplified by the Cordillera Occidental, and regional mineralization in districts like Cerro Rico and the Oruro Department.
The name derives from the cities and regions of Arequipa and the Antofagasta Department region historically linked to exploration by Pedro de Valdivia and later geological surveys by institutions including the Servicio Geológico del Perú and the Servicio Geológico Minero Argentino. Early mapping by geologists associated with the United States Geological Survey and the British Geological Survey adopted local toponyms similar to those used in reports by the Geological Society of London and publications in journals like the Geological Magazine. Nomenclature discussions referenced comparative frameworks from studies of the Grenville orogeny, Amazonian craton, and terranes such as the Famatinian belt and Pampean orogeny.
The block underlies part of the Altiplano-Puna volcanic complex and is bounded to the west by the subduction-related magmatic arc of the Peruvian Andes and to the east by the cratonic foreland linked to the Amazon Basin. Northern limits approach the Nazca Ridge-influenced margin near Tacna, while southern extension reaches toward the Sierras Pampeanas and the Sierra de Cachi. Lateral sutures are inferred with terranes such as the Arequipa Massif and the Arizaro Block and structural discontinuities correspond to major faults including the Santa Bárbara fault, Cuchoquere fault, and segments of the Transverse Andean Fault System. Geophysical signatures from seismic tomography, magnetotellurics, and gravity anomaly studies link the block to high-velocity lithosphere observed beneath the Central Andes.
Tectonic history records Mesoproterozoic to Neoproterozoic assembly during periods correlated with the Pan-African orogeny and reworking during the Neoproterozoic and Cambrian associated with Gondwana amalgamation. Paleozoic episodes reflect collision and subduction processes contemporaneous with the Famatinian orogeny and the Achalian orogeny, followed by Mesozoic extension tied to breakup of Pangea and initiation of the South Atlantic Ocean. Cenozoic reactivation corresponds with the Neogene uplift of the Andes Mountains, slab dynamics of the Nazca Plate, and crustal shortening evident in the Eastern Cordillera and Western Cordillera. Key events reference regional deformation seen across the Altiplano, Puna Plateau, and foreland basins such as the Rio Grande Rift-analog studies and correlations with the Carnegie Ridge-influenced subduction studies.
Basement lithologies include high-grade metamorphic assemblages comparable to units in the Arequipa Massif, with orthogneisses, paragneisses, and pelitic schists recording Precambrian protoliths similar to those described from the Cuyania terrane and Rio de la Plata craton. Intrusive suites comprise granitoids and batholiths analogous to the Coira Complex and Chivinar Complex with ages overlapping those of the Central Andean Batholith. Sedimentary cover includes Paleozoic sequences equivalent to the Puncoviscana Formation, Mesozoic marine and continental strata akin to the Paganzo Group, and Cenozoic deposits forming the Quechua and Mogollón-age successions preserved in the Salta Basin and Toconas Formation. Stratigraphic correlations utilize fossil assemblages comparable to those in the Gondwana-derived sequences and isotopic ages from U-Pb zircon studies.
Metamorphic facies range from greenschist to amphibolite and locally granulite facies as observed in high-pressure complexes similar to exposures in the Hualfín Complex and Sierra de los Cóndores. Structural features include pervasive fabric development, isoclinal folding, thrust imbrication comparable to structures in the Cordillera Real, and large-scale crustal-scale shear zones akin to the Norte Andino Fault System. Kinematic indicators show episodes of transpressional shortening and transtensional extension paralleling deformation patterns associated with the Incaic orogeny and Quechua phases recognized in Andean tectonostratigraphic syntheses.
Paleomagnetic data from granitoids and sedimentary units have been integrated with reconstructions involving the Amazonian craton, West African craton, and the Gondwana assembly, providing constraints on paleolatitudes through the Neoproterozoic–Paleozoic interval. Reconstructions compare to paleogeographic models developed for the Iapetus Ocean closure and the Rheic Ocean margins, and reference magnetostratigraphic ties with units in the Falkland Islands and the Kaapvaal craton. Paleoclimatic indicators in sedimentary successions show shifts analogous to glacial signals recorded in the Sturtian and Marinoan events and later shifts during the Paleogene greenhouse intervals.
The block hosts mineralization styles analogous to those in the Belt of Bolivian Tin and porphyry systems of the Central Volcanic Zone, producing resources including polymetallic deposits, tin–antimony veins similar to Potosí-type ores, and epithermal gold–silver mineralization akin to deposits in the Oruro Department. Exploration targets emphasize skarn, hydrothermal breccia, and replacement bodies comparable to those mined in the Cerro de Pasco District and Zacatecas District. Geochemical signatures, fluid inclusion studies, and isotopic systems such as Sr-Nd isotopes and Pb-Pb dating inform exploration analogous to protocols used by companies like Compañía Minera Milpo and the Bolivian Mining Corporation.