Abstract

Supergene alteration (SA) and supergene copper mineralization (SCM) require climatic conditions that provide sufficient amounts of water for the leaching of sulfides exposed to surficial oxidized conditions, but not quantities of water that could promote erosion of the SCM. Thus, the SCM is the product of a delicate balance between uplift, denudation, and climate, factors that strongly control the geomorphology in the Atacama Desert. Geochronology of supergene minerals allows us to understand the period of SA activity, but they also can indicate changes in the landscape evolution that were critical for the development of the SCM along the Atacama Desert. We have collated 148 radiometric ages from previously published studies conducted between southern Peru and the southern segment of the desert in Chile (16° - 27° lat. S). New alunite and jarosite Ar/Ar ages from the southern high Precordillera (over 3000 m.a.s.l.) are also reported. The results of this compendium confirm how uplift and unroofing affect the conservation of the ages, and the influence of the climate for the ending of the SA and SCM along the Atacama Desert. The current hyperarid core of the desert is well-correlated with the stable period during the late Oligocene to middle Miocene that also facilitated the development of pediplains in the area. On the other hand, the northern and southern margins segments experienced different conditions, with ages notably younger, implying that the supergene processes are still active. Also, our radiometric ages reveal supergene alteration as old as ~42 Ma and young as ~3.5 Ma, which would confirm that the SA above 3000 m.a.s.l. in the Precordillera has different triggering factors than the supergene enrichment that was developed and conserved in the hyperarid core of the Atacama Desert.