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| Sunsás orogeny | |
|---|---|
| Name | Sunsás orogeny |
| Period | Neoproterozoic–Early Cambrian |
| Region | Amazonian Craton, São Francisco Craton, Andean margin |
| Type | Orogenic event |
Sunsás orogeny
The Sunsás orogeny is a major Neoproterozoic–Early Cambrian mountain-building episode that affected large parts of the Amazon Basin, Central Brazil Shield, and adjacent parts of the western margin of Gondwana. It involved collision, accretion, and shear between Precambrian cratonic blocks including the Amazonian Craton, São Francisco Craton, and exotic terranes recognized in the Andean Cordillera. The event is recorded by widespread deformation, metamorphism, and magmatism preserved in shield exposures, basement inliers, and sedimentary basins such as the Paraná Basin and Solimões Basin.
The Sunsás orogeny marks a pivotal phase in the assembly of West Gondwana and the reorganization of Neoproterozoic plate margins adjacent to the Pan-African orogeny and the Brasiliano orogeny. It is temporally associated with global tectonic reorganizations that include the breakup of the supercontinent Rodinia and the assembly of Pannotia. Iconic geological localities documenting the event include the Sunsás Belt exposures, the Cangas terranes, and basement windows in the Cerrado and Amazonas regions.
The tectonic framework for the Sunsás interval juxtaposes the Amazonian Craton with the São Francisco Craton along suture zones that link to the broader Brasiliano-Pan-African orogenic system. The orogeny developed on the western Gondwanan margin adjacent to foreland units preserved in the Parnaíba Basin and hinterland domains now incorporated into the Andean orogen. Major structural domains include the Chapada dos Guimarães fold-thrust belt, the Serranía de Chiribiquete in Colombia, and correlations to the Guyana Shield and Shield of Guiana. Plate reconstructions often invoke margin-parallel shear zones comparable to the Transbrasiliano Lineament and collision geometries resembling those in the East African Orogen.
Sedimentary and volcanic successions that record Sunsás deformation include Neoproterozoic sequences of the Araçuaí Belt, siliciclastic piles in the Paraná Basin, and glaciogenic units correlated with the Marinoan glaciation. Stratigraphic architectures show synorogenic flysch, molasse deposits, and unconformities that separate pre-orogenic cratonic cover from synorogenic basins, with comparable sequences documented in the Sutured terranes of Colombia and the Ouachita-Marathon fold belt analogues. Tectonic evolution models describe initial rifting linked to Rodinia breakup, followed by passive margin sedimentation, subduction initiation, terrane translation, and final collision-driven crustal shortening and exhumation.
High-resolution geochronology constrains deformation and magmatism to an interval centered on ~620–520 Ma, with some early events as old as ~800–700 Ma recorded in detrital zircon populations and inherited cores. U–Pb zircon ages from plutons, metavolcanic units, and detrital suites correlate with SHRIMP and LA-ICP-MS datasets from the São Francisco Craton, Río Negro-Juruena province, and the Cuddapah Basin comparisons. Thermochronologic signals from ^40Ar/^39Ar mica cooling and U–Pb titanite tie metamorphic peaks to Cambrian exhumation synchronously with widespread Brasiliano–Pan-African timing.
Metamorphic grades range from low-grade greenschist to medium-pressure amphibolite facies with localized high-pressure assemblages in syntectonic metamorphic complexes akin to those of the Serranía del Perijá and the Mantiqueira Complex. Structural fabrics include regional foliation, tight recumbent folds, metamorphic core complexes, and large-scale thrust systems comparable to the Alto Paraguay fold belt. Shear sense indicators and mylonite zones link to major transcurrent systems such as the Transamazonian and Transbrasiliano networks and record both contractional and transpressional kinematics.
Sunsás-related magmatism comprises a spectrum from calc-alkaline batholiths and volcanic arcs to A-type granites and extensional mafic dikes. Plutonic suites show I-type and S-type affinities with isotope signatures (Nd, Sr, Pb) indicating mixtures of juvenile mantle-derived melts and reworked continental crust similar to magmatic records in the Sierra de la Ventana and Sierras Pampeanas. Mafic to intermediate volcanic rocks preserve arc-like geochemical fingerprints while late-stage anatectic granites carry high-K, peraluminous signatures paralleling those in the Araçuaí-Ossa-Morena belts.
The Sunsás orogeny is integral to reconstructions that place the Amazonian Craton adjacent to the West African Craton, Baltica, and other Gondwanan fragments during Neoproterozoic assembly. Detrital zircon populations, paleomagnetic poles, and lithologic affinities enable correlations between Sunsás domains and the Llanoria and Gondwanan ribbon continents recognized in global syntheses. Proposed suture links extend into northwestern South America, tying Sunsás structures to the evolution of the proto-Andean margin and to terranes now identified in the Guiana Shield, Colombian Massif, and Peruvian Shield.
Mineral deposits associated with Sunsás-related magmatism and hydrothermal systems include orogenic gold in metamorphic belts, tin-tantalum pegmatites in anatectic provinces, and base-metal skarn and polymetallic veins analogous to mineralization in the Carajás Mineral Province and Zacatecas District comparators. Magmatic-hydrothermal systems related to A-type granites host rare-element pegmatites and greisenized zones exploited in artisanal and industrial operations across the Cerrado and Amazonas shield sectors. Exploration models target suture zones, shear corridors, and synorogenic basin margins for prospective deposits.
Category:Orogenies Category:Neoproterozoic geology Category:Geology of South America