INVESTIGADORES
COIRA Beatriz Lidia Luisa
artículos
Título:
Tectonic and magmatic evolution of the Andes Northern Argentina and Chile.
Autor/es:
COIRA, B.; J.,DAVIDSON; C.,MPODOZIS Y V.,RAMOS
Revista:
EARTH-SCIENCE REVIEWS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 1982 vol. 18 p. 303 - 332
ISSN:
0012-8252
Resumen:
Two orogenic cycles, both with different evolution, are developed in the western margin of
the South American continent in northern Argentina and Chile: the Paleozoic "Hercynic"
cycle and the Meso-Cenozoic "Andean" cycle.
The Hercynic cycle. A wide marine basin extending westward of the Cordillera Oriental
which developed in Cambrian-Ordovician times marks the beginning of this cycle. In
contrast to Peru and Bolivia where this basin developed between two Precambrian blocks, the
western margin of this basin in northern Argentina and Chile is still unknown. The
Ordovician sedimentation and accompanied volcanism ends with the Ocloyic deformation
phase and its synkinematic granitic plutonism. Two basins were developed in the Silurian-
Devonian separated by the Puna arc, uplifted during this ocloyic phase. The shallow-water
marine terrigeneous sediments which were deposited in them were deformed by a new
tectono-magmatic associated phase (Chanic phase).
Carboniferous to Lower Permian marine carbonates were deposited west of the Puna arc
and red beds east of it. Later on, during the Permian to Triassic, a magmatic belt was
developed along the Cordillera Occidental. The rhyolites, ignimbrites and the granitic to
granodioritic related intrusives are well represented in Chile. Although the overall geologic
history of this period is known, many problems concerning its origin and relations to plate
tectonics are still unsolved.
The Andean cycle. During this cycle, a series of magmatic-arc systems related to the
subduction of the Pacific crust was built up along the western margin of South America.
Huge volumes of calc-alkaline lavas and related plutons were emplaced since the Jurassic,
along belts parallel to the present coastline, showing a general eastward migration trend. Up
to the Lower Cretaceous, an ensialic back-arc basin was formed east of this magmatic arc.
Thousands of meters of marine and continental sediments were deposited in it. This basin
disappeared during the Middle Cretaceous, probably as a result of the final opening of the
Atlantic and the active westward movement of the South American Plate.
Since Middle Cretaceous times, the magmatic-arc has been the fundamental paleogeographic element. The arc progressively migrated stepwise eastward, each step marked by a tectonic phase. Subduction-related crustal erosion could explain the lack of fore-arc petrotectonic assemblages. The eastward magmatic polarity which characterizes this section of the Andes, could also be explained by such a mechanism.