Regional metal zonation in the Central Andes: tin versus copper

AUTHORS: Bernd Lehmann

ABSTRACT : The Central Andes is a textbook example of ore formation at an active continental margin. Base-metal porphyry systems mark short-lived regional episodes of change in subduction style/stress regime on a general background of quasi-continuous subduction. The transition from normal to flat subduction, i.e., lithospheric hydration at low magmatic activity, is favorable for the formation of large copper porphyry systems in the outer arc. The oxidized mantle-ominated fluid reservoir with recycled seawater is tapped by deep strike-slip structures which develop in response to changes in plate convergence. Tin porphyries occur during transition from flat to normal subduction, and/or during delamination of thickened continental crust, in the inner arc when flow of hot asthenospheric mantle into the expanding mantle wedge leads to large-scale melting of the continental crust and subsequent fractional crystallization under reducing conditions of a mostly continental fluid reservoir.

KEYWORDS: Andes, copper, tin, porphyry systems

EAN: SGA_2011_A006
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