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| Famatinian orogeny | |
|---|---|
| Name | Famatinian orogeny |
| Period | Ordovician–Silurian |
| Region | Cordillera Oriental, Sierras Pampeanas, Argentina |
| Type | Orogeny |
| Orogenic belt | Andean orogen |
Famatinian orogeny The Famatinian orogeny was a major Paleozoic mountain-building event that affected western Gondwana during the Ordovician–Silurian, producing the Sierras Pampeanas and contributing to the evolution of the Andean margin. It involved subduction-related accretion, magmatism, and crustal thickening that linked tectonic histories recorded in the Western Gondwana margin, the Cuyania terrane, and neighboring cratons.
The orogeny developed along the western margin of Gondwana adjacent to the Paleo-Pacific Ocean, with key exposures in the Sierras Pampeanas, Cordillera Oriental (Argentina), and the Famatina Range. It is contemporaneous with margin events recorded in the Arequipa-Antofalla craton and shares temporal overlap with tectonism affecting the Amazonian Craton and the Río de la Plata Craton. Regional comparisons invoke correlations with terranes such as Cuyania (also called the Precordillera), links to the Chilenia Terrane, and broader interactions with the Iapetus Ocean-age systems. Paleogeographic reconstructions commonly reference work tied to Alexander du Toit, Alfred Wegener-inspired Gondwana configurations, and later syntheses by researchers associated with institutions like the Geological Society of America and the International Union of Geological Sciences.
Tectonic models interpret the orogeny as a sequence of subduction, arc accretion, collision, and post-collisional extension. Early arc-building stages are compared to modern examples like the Andes and ancient systems such as the Taconic orogeny of Laurentia. Middle Ordovician to Silurian phases record emplacement of batholiths, slab rollback, and terrane docking that are analogous to processes described in studies from the Sierra Nevada and the Caledonian orogeny. Kinematic reconstructions use paleomagnetic datasets from the Punta del Agua Formation and structural studies linked to researchers from the Universidad de Buenos Aires and the Smithsonian Institution. Proposed collisional events involve interaction between the Cuyania terrane and the western Gondwana margin, invoking analogues to the Variscan orogeny and timings constrained by graptolite biostratigraphy and radiometric ages from laboratories such as Los Alamos National Laboratory.
Stratigraphic successions include Ordovician shallow-marine carbonates, flysch-like sequences, and siliciclastic turbidites exposed in the Sierras de Córdoba and the Puna Plateau. Lithologies range from limestones and shales to continental volcaniclastic units and andesitic to rhyolitic volcanics, with key formations correlated to units described in papers affiliated with the Universidad Nacional de Córdoba and the Servicio Geológico Minero Argentino (SEGEMAR). Fossil assemblages include graptolites, conodonts, and trilobites that allow correlation with biostratigraphic zonations from the Ordovician standard charts produced by the International Commission on Stratigraphy.
Metamorphic grades vary from greenschist to amphibolite facies across metamorphic complexes such as the Famatina Complex and the Achala Batholith region. Magmatism produced widespread calc-alkaline and high-K plutons, documented by U-Pb zircon geochronology from laboratories including Geoscience Australia-partnered studies and isotope work comparable to records from U-Pb dating centers. Metamorphic P-T paths reflect crustal thickening and subsequent exhumation comparable to models developed for the Himalaya and the Alps in comparative tectonics literature authored by institutions like the University of Oxford and the Massachusetts Institute of Technology.
Deformation is characterized by crustal-scale thrusting, fold-thrust belts, regional nappes, and steep strike-slip shear zones; notable structures include major thrust ramps in the Sierras Pampeanas and transpressional features in the Famatina Range. Kinematic indicators, cleavage patterns, and isoclinal folds have been analyzed in field programs affiliated with the Consejo Nacional de Investigaciones Científicas y Técnicas and published in journals associated with the American Geophysical Union. Structural comparisons cite analogues in the Andean orogen and fault systems like the San Andreas Fault for conceptual frameworks of oblique convergence.
Reconstruction models place the orogenic belt at tropical to subtropical latitudes on the margin of Gondwana, with terrane translations inferred from paleomagnetic poles generated by research groups at the Instituto de Geociencias (UNAM) and the British Geological Survey. Competing hypotheses include autochthonous margin evolution versus outboard terrane accretion (e.g., Cuyania as an exotic microcontinent), with syntheses drawing on comparisons to the displacement histories of the Avalonia and Armorica terranes. Global plate models incorporate data from the Pangea-precursor configurations and use software developed at centers like the Paleomap Project.
The orogeny is linked to major mineral provinces including epithermal and porphyry-related systems, with significant occurrences of tin, tungsten, gold, silver, lead, and zinc hosted in skarn, vein, and breccia deposits. Prominent mining districts in the region have histories tied to companies such as Barrick Gold and national mining agencies like Yacimientos Mineros de Agua de Dionisio-style state initiatives. Exploration strategies reference metallogenic models comparable to those used for the Belt-Purcell Supergroup and the Carlin Trend, and involve geochemical programs led by institutions including the International Mineralogical Association-affiliated research groups.
Category:Orogenies Category:Geology of Argentina Category:Paleozoic orogenies