Abstract
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.