A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction

Jacques Bourgois (1) , Yves Lagabrielle (2) , Hervé Martin (3) , Jérôme Dyment (4) , Jose Frutos (5) , Maria Eugenia Cisternas (6)

1 iSTeP - Institut des Sciences de la Terre de Paris
2 GR - Géosciences Rennes
3 LMV - Laboratoire Magmas et Volcans
4 IPGP - Institut de Physique du Globe de Paris
5 San Juan de Luz 4060
6 Instituto de Geologia Economica Aplicada (GEA)

This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°–48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature–pressure (P–T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at*6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin

Domaines: Sciences de la Terre

Jacques Bourgois, Yves Lagabrielle, Hervé Martin, Jérôme Dyment, Jose Frutos, et al.. A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction. Pure and Applied Geophysics, 2016, 173 (10-11), pp.3217-3246. ⟨10.1007/s00024-016-1317-9⟩. ⟨hal-01326121⟩