Resumen
Permian to Triassic igneous rocks cropping out in the Coastal and Frontal cordilleras in northern Chile
between 28º00?S and 30º15?S have long been interpreted to represent products of magmatism related to an extensional
tectonic setting, either as the result of crustal anatexis or asthenospheric mantle decompression melting, in a passive
continental margin. Eighty-six samples of plutonic (61) and volcanic (25) rocks from this region are characterized
petrographically and geochemically. They are Permian to Early Jurassic in age, but the majority of the studied rocks
correspond to the Lower to Middle Triassic Chollay Plutonic Complex, the volumetrically most important unit in the
area. The rock samples have features typical of magmas derived from flux-induced melting of a depleted mantle such
as: broad range of petrographic composition with predominance of intermediate to acid members, highly porphyrytic
volcanic rocks, magnetite as the Fe-Ti oxide mineral phase, enrichment in LILE over HFSE, marked depletion in Nb,
Ta, Ti, and P and moderate to no negative Eu anomalies. Few of the studied rock samples (<10%) have alkaline signature
and trace element contents representative of anorogenic magmatism. In this work, we propose that subduction of an
oceanic plate beneath the South American continent is responsible for the evolution of the margin from the Permian
to Early Jurassic, at the studied latitudes. A preliminary interpretation of the margin architecture of the Andean
margin from the Permian to the Triassic would be that the Chanchoquin and Chollay plutonic complexes represent
the roots of a magmatic arc developed from the Permian to the Middle or early Late Triassic, whereas the Guanaco
Sonso and Pastos Blancos formations would be the shallower parts of such arc. The La Totora Formation and some
volumetrically minor Upper Triassic intrusive units represent magmatic products with alkaline signatures, which
developed immediately before the