Chemical and isotopic evolution of the Coastal Batholith of southern Peru

Southeast of Arequipa, the Coastal Batholith of southern Peru is composed of two segments (Arequipa and Toquepala) including five superunits which were emplaced in discrete magmatic pulses from the Jurassic to the Paleocene eras (190-61 Ma). Most superunits intruded a Precambrian basement dominated by granulitic and amphibolitic rocks. Major and trace element analyses reveal that each superunit is formed by distinct suites of calc-alkaline plutons (i.e., "I' type) that range in composition from quartz gabbro to monzogranite. For the whole plutonic suite located in southern Peru, the evolution toward negative ε_{nd i} and positive ε_{Sr i} values is followed by a significant decrease in ²⁰⁶Pb/²⁰⁴Pb_i ratios but is also related to the density of Precambrian outcrops. This led us to classify the intrusives into three groups. There are several petrogenetic models which can explain the trace element, isotopic, and geographic correlations observed within the Coastal Batholith of southern Peru. -from Authors