THE GEOCHEMISTRY AND PETROGRAPHY OF THE COASTAL BATHOLITH OF PERU, LIMA SEGMENT

Summary: The Coastal Batholith of Peru, Lima segment, is a composite batholith made up of at least 8 time-separated magmatic events. The evolution of the batholith is such that the amount of granitic magma apparently increases with decreasing age, which is reflected in an overall basic to acid sequence of intrusion. High-level differentiation, involving plagioclase and hornblende as the major precipitating phases, is the prime cause of the chemical variation within each suite of rocks, all of which are distinguished by strong calc-alkaline character. The geochemical and petrographical evidence suggests that the batholith magmas were undersaturated with respect to water throughout most of their crystallization histories. Preliminary isotopic studies indicate that the parent magmas to individual super-units originated by partial melting, either in the mantle or in a crustal underplate zone. © 1981 The Geological Society.