摘要
The late Miocene–early Pliocene Taitao ophiolite is exposed~30 km southeast of the Chile triple junction,where a spreading center of the Chile ridge system is subducting underneath the South America plate.This unique tectonic setting provides an excellent opportunity to study the emplacement mechanism of a ridge-trench intersection ophiolite and the complex magmatic interactions between the subducting ridge,overlying crust and sediments,and the mantle wedge.As a result of these interactions,several granitic plutons were formed contemporaneously with emplacement of the ophiolite.We review previous studies of the Taitao ophiolite and use new geochemical data to discuss the mechanism that formed juvenile magma of calc-alkaline I-type granites during ridge subduction.Our model implies that the magmas of the Taitao granites formed due to partial melting of hot oceanic crust adjacent to the subducting mid-oceanic ridge that has been contami-nated by deep crustal material and/or metasomatized sub-arc mantle.The partial melting took place under garnet-free amphibolite conditions.The juvenile magmas then incorporated different amounts of subducted sediments and/or continental material to form the I-type granites with various compositions.Subduction of fracture zones played an important role in these processes.
基金
supported by grant-in-aid for Science Research 13373004 and 15H02630 by the Ministry of Education,Culture,Sports,Science and Technology of Japan.
