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The Andes and Hotspots: Mutual Evidence
  • Rex Herbert Pilger
Rex Herbert Pilger
Retired, Retired

Corresponding Author:rexpilger@gmail.com

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Improved plate-to-plate reconstructions in the southwest Pacific, South Atlantic, and southwest Indian Ocean, and plate-to-hotspot models for the Pacific plate, combined with published igneous dates of the South American Andes produce apparent correspondence of predicted with observed magmatic patterns in the mountain range. The inferred Easter-Nazca (EN) and Juan Fernandez (JF) hotspot traces, long inferred to control low-angle subduction and contemporary volcanic gaps along the Andean crest, when reconstructed match the traces’ present bathymetric expression and seismic clusters within the South American plate. Global reconstructions of the Nazca to the South American plate predict the subducted portions of the traces through time. Gaps in magmatism over the past 10-15 Ma correspond with the reconstructed position of the traces beneath Peru (EN) and Chile and Argentina (JF). The predicted JF trace also matches trends in magmatism, especially mafic rocks, including eastward shifts and gaps as early as 60 Ma in Bolivia, southern Peru, Chile, and Argentina from the 80-90 Ma segments of the trace. The magmatic pattern provides a kind of “image” of the hotspot traces projected onto the Cenozoic of the Andes. The correspondences also increase confidence in the existence of a stable hotspot reference frame beneath the plates of the Pacific over the past ~90 m. y.