The Taitao ophiolite-granite complex, Chile: Emplacement of ridge-trench intersection oceanic lithosphere on land and the origin of calc-alkaline I-type granites

Abstract

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 contaminated 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.

Geochemical characterization and petrogenesis of intermediate to silicic rocks in ophiolites: A global synthesis

“…The ca. 6 Ma Taitao ophiolite formed by seafloor spreading at the Chile Ridge and was accreted into the fore-arc region of the South American Plate due to ridge-trench interaction (Veloso et al, 2005(Veloso et al, , 2009Dilek and Furnes, 2014;Shin et al, 2015). The 22 Ma Tihama Asir complex is an in-situ continental margin ophiolite, formed during the initial stages of rifting between the African and Arabian plates in the Miocene .…”

A cold seep triggered by a hot ridge subduction

“…The subduction of the CR leaves distinctive features in the geological records of the overriding South American plate, such as: (a) regional metamorphism and high thermal gradient 3 – 7 ; (b) a hiatus in arc magmatism 8 , 9 ; (c) near trench magmatism 10 – 18 ; (d) subduction erosion process 1 , 14 , 19 ; (e) hydrothermal circulation 7 , 20 , 21 ; (f) continuous tectonic uplift of the Andes 14 , 22 ; (g) wedge shortening 23 ; (h) slab window 2 , 24 – 26 ; (i) ophiolite obduction 10 , 27 – 31 ; and (l) a distinct continuous, shallow and strong bottom-simulating reflector (BSR) 6 . The latter marks the base of the gas hydrate stability zone, and exhibits a significant decrease in gas hydrate concentration (10% of the total volume) in the vicinity of the CTJ 32 .…”

Ophiolites, diamonds, and ultrahigh-pressure minerals: New discoveries and concepts on upper mantle petrogenesis

“…However, our knowledge of the occurrence of diamonds and UHP minerals in ophiolitic chromitites and peridotites is still limited because we do not know whether such minerals are also present in ophiolites that formed in nonsubduction-related tectonic environments, such as mid-ocean ridge, ocean-continent transition zone (or continental margin), and plume-related ophiolites Furnes, 2011, 2014). Future investigations of the upper mantle peridotites exposed in the mid-ocean ridge-type Taitao ophiolite in Chilean Patagonia (Shin et al, 2015), ocean-continent transition zone-type Jurassic ophiolites of the Western Alps (Festa et al, 2015), and the plume-type Colombian ophiolites in the northernmost Andes (Kerr et al, 1998;Dilek and Furnes, 2014) should help us answer this question.…”