Modelos orogénicos de tectónica de placas en los Andes Colombianos

Los Andes Colombianos son el resultado de la superposición de varias orogenias que corresponden a distintos tipos de cadena. En la Cordillera Oriental una cadena caledoniana se desarrolla encima del zócalo precámbrico y no produce acrecimiento continental; algunas de sus características la aproximan a un tipo de cadena andina. En la Cordillera Central y en la Sierra Nevada un intenso metamorfismo Abukuma acompañado de pequeños plutones indica una fuerte orogenia herciniana. Esta cadena, que es en parte suprasímica y de tipo alpino, se formó aparentemente como consecuencia de la colisión entre Centroamérica septentrional y Suramérica. Estas dos placas se separaron durante el Triásico debido a la actividad de un rift que generó corteza oceánica entre ellas. Durante el Triásico-Jurásico en las márgenes del Valle del Río Magdalena se formó un cinturón magmático acompañado por un graben tensional supracratónico ; ambos fenómenos parecen estar asociados a una subducción activa localizada al occidente de la Cordillera Central. Durante este lapso de tiempo los Andes Colombianos tienen características típicamente andinas. Recientes determinaciones radiométricas han permitido conocer mejor la compleja historia del occidente durante el Cretáceo. Una corteza oceánica, datada en 131 m.a., se generó en un rift localizado a corta distancia del continente. A finales del Albiano parte de esta corteza fue obducida sobre el basamento de la Cordillera Central. Esta obducción produjo un metamorfismo de presión media datado entre 110 m.a. y 100 m.a. Durante el Cretáceo tardío una subducción situada al occidente de la Cordillera Occidental permitió la formación de un cinturón tonalítico en la parte septentrional de la Cordillera Central y de un arco básico en la Cordillera Occidental. Este arco parece estar acompañado de un metamorfismo de muy bajo grado. Durante el Cretáceo la cadena tiene características mixtas, ya que la incorporación de material oceánico, sea por obducción, sea por acrecimiento, es una característica alpina, mientras que el magmatismo en la Cordillera Occidental es de tipo arco, que pasa lateralmente en la Cordillera Central a uno de tipo andino. Fallas de rumbo, tales como las de Cauca-Romeral y Palestina, se producen a finales del Cretáceo o a principios del Terciario. Finalmente, durante el Cenozoico la Cordillera Occidental evoluciona como arco suprasímico en proceso de continentalización, mientras que la Cordillera Oriental se comporta como una cadena intracontinental.

The present Andes of Colombia are a complex mountain chain formed by the superposition of several orogenies. To understand this final result it is necessary to separate in space and time each orogenic event, determining when and were it took place and what orogenic model it followed. In the Eastern Cordillera a Caledonian chain was formed over Precambrian basement and without continental accretion; most of the characteristics belong to an Andean type of chain. In the Central Cordillera and the Sierra Nevada strong metamorphism and small plutons were formed during a late Hercynian orogeny. This chain, which is partially suprasimic and of Alpine type, was probably formed by the collision of northern Mesoamerica and northwestern South America. The two plates were separated during the Triassic by an active rift that generated oceanic crust between them. During the Late Triassic and Jurassic a magmatic belt and a supracratonic graben were formed in the margins of the Magdalena Valley.
Both features seem to be related to an active subduction zone located to the west of the Central Cordillera. During this event the modell is typically Andean. The Cretaceous history is very complex, but the major events have been dated by some recent radiometric ages. An oceanic crust was generated in an active rift located to the west of the Central Cordillera.
This crust, dated at 131 m.y., was obducted over the continental crust of the Central Cordillera at the end of the Early Cretaceous. The obduction produced dynamic effects, especially a Barrovian metamorphism dated at 110 and 100 m.y. During the Late Cretaceous a new subduction zone was formed at the western margin of the Western Cordillera, trapping Lower Cretaceous oceanic crust that was since then accreted to the continent.
The associated magmatism corresponds to tonalitic plutonism in the Central Cordillera and to a basic volcanic arc (92 m.y.) in the Western Cordillera; the inmature arc was affected by a very-low grade metamorphism. The Cretaceous evolution corresponds to several orogenic models, and in this sense it is a mixed or compound type of orogeny. The incorporation of the oceanic crust -by obduction and by accretion- and the associated metamorphism correspond to an Alpine model, while the basic magmatism of the Western Cordillera corresponds to a suprasimic volcanic arc that passes laterally to an Andean type of magmatism in the Central Cordillera. Strike - fault systems, such as the Cauca - Romeral and Palestina, were formed at the close of the Cretaceous or the beginning of the Tertiary. During the Tertiary a new subduction zone, probably located at the present continental margin, produced intermediate plutonism in the Western Cordillera. This plutonism is the beginning of the cratonisation of this chain and corresponds to a more mature volcanic arc. In the Eastern Cordillera the sediments deposited since the Late Paleozoic were deformed and uplifted according to an intracratonic model.