A general view of the Chilean-Argentinian Andes, With Emphasis on Their Early History

HERVE, F; GODOY, E.; PARADA, M.A.; RAMOS, V.A.; RAPELA, C.W.; MPODOZIS, C.; DAVIDSON, J.

Circum-Pacific Orogenic Belts and Evolution of the Pacific Ocean Basins

American Geophysical Union

Año: 1987; p. 97 - 113

The Andes are generally thought of as a young mountain belt associated with eastward subduction of the Nazca, or preexisting oceanic plates, beneath the South American plate. However, the Meso-Cenozoic Andes are built over a highly complex basement which spans Precambrian to Triassic time. Collision of continental blocks seems to have occurred in the early Paleozoic in northern and central Argentina and Chile. A well defined late Paleozoic subduction complex is present along the Coastal Range south of latitude 3O°S This is associated with a Carboniferous to Permian magmatic belt and related marine basins constructed inboard of the southwest Gondwana continental margin. Paired metamorphic belts with local blueschists were developed during the accretion processes. The Meso - Cenozoic history is mainly one of plutovolcanic  “accretion” via episodic buildups of narrow, linear, north—south trending, calc—alkaline magmatic belts. Those of Jurassic to Early Cretaceous age are related to tack-arc ensialic basins which, in the southernmost Andes, evolved into short lived, marginal basins floored by oceanic-type crust. Longitudinal changes in stratigraphy and tectonism along the belt appear to reflect complex interactions of the converging palaeo-plates which have present day expression .n the volcanic and tectonic segmentation of the Andes. The huge late Tertiary to Recent volcanic deposits testify to the widespread partial melting of subcontinental mantle associated with subduction of the Nazca plate. The latter may have tectonically eroded parts of the Paleozoic complexes and Meso- Cenozoic tore-arc assemblages. The existence of major faults roughly parallel with the continental margin, one of which is associated with the subducting Chile Rise, suggests that other rises or ridges have been consumed earlier in the geological history of the Andean chain.