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| South Patagonia Superterrane | |
|---|---|
| Name | South Patagonia Superterrane |
| Type | Terrane/Superterrane |
| Region | Patagonia |
| Country | Argentina; Chile |
| Era | Paleozoic–Mesozoic |
| Lithology | Metasedimentary rocks; metavolcanic rocks; granitoids; ophiolites |
| Orogeny | Gondwana accretion; Andean orogeny overprint |
South Patagonia Superterrane
The South Patagonia Superterrane is a composite tectonostratigraphic assemblage in southern Patagonia spanning portions of Santa Cruz and Magallanes Region in Chile. It comprises juxtaposed exotic blocks that record Paleozoic and Mesozoic episodes of subduction, arc magmatism, and continental collision linked to the growth of Gondwana and later modification during the Andean orogeny. Interpretations of its origin and amalgamation draw on comparisons with terranes along the Western Cordillera, correlations with Falkland Islands geology, and paleomagnetic, geochronological, and structural datasets employing analogs from the Caledonides, Variscan belt, and Cordilleran orogeny.
The South Patagonia Superterrane is recognized through mapping of discontinuous belts of Paleozoic metasedimentary successions, Ordovician–Devonian volcanic arcs, and Mesozoic granitoids that rest upon or incorporate fragments of ophiolitic and parautochthonous basement; this architecture has been investigated by researchers from institutions such as the Servicio Geológico Minero Argentino, Servicio Nacional de Geología y Minería (SERNAGEOMIN), and international teams collaborating with universities including University of Buenos Aires, University of Chile, and University of Oxford. Key field localities include the Deseado Massif, the Magallanes Basin, and the Tierra del Fuego periphery, which preserve fossils, detrital zircon populations, and structural records used to test models invoking transport from peri-Gondwanan margins, intra-oceanic arcs, or microcontinental slivers like the proposed Río de la Plata Craton fragments.
The superterrane occupies the southernmost sector of the South American Plate and is bounded to the north by the North Patagonian Massif and to the west by the Andes magmatic arc; its eastern limit intersects the South Atlantic Ocean margin and the continental shelf off Argentine Patagonia. Major tectonic contacts include suture zones interpreted beneath the Magallanes fold-and-thrust belt and the Beagle Channel region, where lithotectonic domains abut the Fuegian Andes, ophiolitic remnants correlate with the Famatinian and Sierra de la Ventana systems, and paleogeographic links to the Precordillera Terrane and Chilean Coastal Complex have been proposed.
Stratigraphic assemblages consist of Cambrian–Ordovician metasediments, Silurian–Devonian volcanic and volcaniclastic successions, Carboniferous to Permian flysch, and Mesozoic continental to marine sediments of the Jurassic–Cretaceous age. Lithologies include schists, quartzites, turbiditic sandstones, basaltic to andesitic metavolcanic suites, island-arc tholeiites, and high-Mg ophiolitic peridotites; plutonic rocks range from Paleozoic tonalites to Mesozoic granodiorites and batholiths analogous to the Patagonian Batholith. Fossil assemblages with trilobites, brachiopods, and graptolites provide biostratigraphic ties to the East Gondwana provinces and correlate with sections in Antarctica and the Cape Fold Belt.
Models for the superterrane invoke multiple accretionary events: Early Paleozoic rifting and arc formation during the Cambrian explosion-age cycles, Ordovician subduction-related magmatism synchronous with the Famatinian orogeny, Devonian collision and arc-continent interactions, and Permo-Triassic rearrangements related to the Gondwanide Orogeny. Mesozoic breakup of Pangea and opening of the South Atlantic Ocean initiated transtensional reconfiguration and emplacement of widespread plutonism associated with the proto-Andean margin; subsequent convergence during the Cenozoic Andean orogeny imposed crustal shortening, exhumation, and foreland basin development exemplified by the Magallanes Basin evolution.
Reconstructed paleogeographies place terrane fragments adjacent to the southwestern margin of Gondwana, with intermittent isolation as microcontinents or island arcs connected to Baltica and Laurentia via oceanic gateways like the Iapetus Ocean analogs. Depositional environments ranged from shallow-marine carbonate platforms to deep-marine turbidites and forearc basins; climate signals preserved in sedimentary facies reflect transitions from Cambro-Ordovician greenhouse conditions through Devonian reefal systems to Permian glacially influenced intervals synchronous with records in eastern Australia and South Africa.
The superterrane preserves polyphase metamorphism from low-grade greenschist to medium-pressure amphibolite facies associated with subduction and collisional events; metamorphic mineral assemblages include garnet, staurolite, and kyanite in metapelites. Structural fabrics comprise regional foliations, upright folds, thrust faults, and extensional detachments mirrored in the Southern Patagonian Ice Field hinterland and the Beagle Channel shear zones. Metamorphic ages from U-Pb zircon and 40Ar/39Ar systems constrain orogenic pulses contemporaneous with the Caledonian-to-Variscan time window in Gondwanan reconstructions.
The terrane hosts metallogenic provinces with hydrothermal vein systems, volcanogenic massive sulfide (VMS) prospects, orogenic gold occurrences, and porphyry-related copper–gold mineralization tied to Jurassic–Cretaceous magmatism; exploration targets have been evaluated by companies working in the Deseado Massif and the Aysen Region. Additional resources include industrial minerals in metamorphosed carbonate units and placer deposits derived from glacial and fluvial reworking, with regional economic geology influenced by infrastructure in Punta Arenas and port access at Puerto Madryn.
Category:Geology of Patagonia Category:Terranes