Rb/Sr ages of rocks from the Chilean metamorphic basement

Eleven whole rock Rb/Sr age determinations from the Chilean metamorphic basement — formerly considered as Precambrian — define two limiting reference isochrons of 342 and 273 my. Analized rocks are phyllites and schists of sedimentary origin with mineralogical assemblages mainly corresponding to the greenschist facies.Two metamorphic series characterize the Chilean metamorphic basement: an eastern low P/T series, and a western high P/T series. Four of the analyzed samples belong to the former and seven to the latter.The obtained age is interpreted as the age of a main metamorphic episode of the basement. This episode would have taken place in the Upper Paleozoic.