Abstract

Eight shallow-level intrusions and an ophiolite complex have recently been discovered in a remote region along the Pacific coast of southern Chile known as the Taitao Peninsula. The magmatic rocks are found only 10 to 15 km from the buried extension of the Peru-Chile Trench. The ophiolite body includes serpentinized ultramaflc rocks, gabbro, dikes, and an interbedded sequence of volcanic and marine sedimentary rocks. More regionally distributed granodiorite plutons and porphyritic stocks and sills intrude pre-Late Jurassic basement as well as Tertiary marine sequences of the South American forearc. K-Ar ages of 3.5 to 4.0 Ma of the ophiolite and other intrusions suggest that these rocks represent a short-lived pulse of Pliocene magmatism. Directly seaward of the Taitao Peninsula a segment of the Chile Rise bounded by the Tres Monies and Taitao fracture zones collided with the Chilean forearc and was subducted about 2.5 to 4.0 Ma. Because of this good spatial and temporal correlation, the magmatic activity of the Taitao Peninsula is likely to be a direct result of ridge subduction.

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