Paleogene arc-related volcanism in the Southern Central Andes and North Patagonia (39°-41°S).

LUCIA FERNANDEZ; MIGUEL RAMOS; VANESA LITVAK; ANDRES FOLGUERA; SOFIA IANNELLI; ROSEMARY JONES; VICTOR RAMOS

The evolution of the Chilean-Argentinean Andes

Springer

Año: 2018; p. 331 - 347

The influence of tectonic processes in evolution of magmatic suites7 evaluated through their geochemical signature has always been a subject of debate.8 Late Paleocene arc volcanism in the Southern Central Andes, particularly in North9 Patagonia, can be used to infer a direct relationship between magmatic episodes and10 tectonic changes along the Andean margin. Eocene arc-related volcanism11 (*44 Ma) in the North Patagonian Andes shows evidence for limited influence of12 the subducting slab on the composition of arc magmas and they exhibit an alkaline13 tendency. By Oligocene times (*29 Ma), arc volcanic sequences in the Auca Pan14 depocenter show predominantly arc-like geochemical signatures and have been15 derived from a calc-alkaline source. However, a comparison with younger arc16 sequences (<28 Ma) in the region suggests that the magmatic source turned more17 tholeiitic in composition with a remarkable increase in the influence of slab-derived18 fluids, as seen in volcanic rocks from Cura Mallín and Abanico retro and intra-arc19 basins. It is proposed that the marked geochemical variations between these mag-20 matic periods are related to the tectonic changes associated with the breakup of the21 Farallon plate at *28?26 Ma. The geochemical data from Eocene and Oligocene