Geochronology of Mesozoic-Cenozoic magmatism in central Chile, lat. 31° 36°S

Details Geochronology of Mesozoic-Cenozoic magmatism in central Chile, lat. 31° 36°S Geochronology of Mesozoic-Cenozoic magmatism in central Chile, lat. 31° 36°S

Nov 1982

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982esrv...18..353d&link_type=abstract

Earth Science Reviews, Volume 18, Issue 3-4, p. 353-363.

Physics

4

Scientific paper

Radioisotope dates indicate magmatism in central Chile (lat. 32° 36°S) has been episodic and migratory throughout Mesozoic and Cenozoic time. Dated plutonic and metaplutonic rocks appear to cluster into the following age groups: (1) 415-380 m.y., (2) 310-270 m.y., (3) 230-170 m.y., (4) 170-140 m.y., (5) 120-80 m.y., (6) 63-56 m.y., and (7) 24-7 m.y. Rocks of Meso- and Cenozoic age are distributed in remarkably well defined, parallel linear belts which trend N-S and are older away from the Central Andean Cordillera. This pattern suggests that the continental margin has increased in width by as much as 200 km in the last 200 m.y. by the emplacement of successive plutonic belts. Volcanic strata of Lower Middle Jurassic age (7000 m) and Early Cretaceous age (7000 13000 m) occur on the west side of the present Coastal Cordillera and on both flanks of the Andean Cordillera. These rocks, mainly andesites, rhyolites, and volcano-clastic sediments, are intercalated with fossil-bearing marine sediments which provide age control up until the final emergence of the Andean Cordillera in Late Cretaceous time. K-Ar dates indicate this continental volcanism continued through the Late Cretaceous, then ceased during the period between 60 and 30 m.y. This hiatus in volcanism coincides with the absence of plutonic rocks in this age range. In the central Andean Cordillera, volcanism began again about 25 m.y. ago and has persisted with variable intensity to the present. Post-Oligocene volcanic strata are generally nearly conformable above Late Cretaceous volcanic strata, and Miocene regional folding has deformed the entire stratigraphic sequence into broad N-S trending folds. Volcanic strata younger than 4 m.y. are undeformed. The presently active chain of strato-volcanoes appears to be less than 500 000 years old and west of older extinct volcanoes 1 2 m.y. old suggesting a westward shift of the volcanic are during the Pleistocene.

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