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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

A 100-m.y.-long window onto mass-flow processes in the Patagonian Mesozoic subduction zone (Diego de Almagro Island, Chile)

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Angiboust, Samuel [1] ; Cambeses, Aitor [1, 2] ; Hyppolito, Thais [3] ; Glodny, Johannes [4] ; Monie, Patrick [5] ; Calderon, Mauricio [6] ; Juliani, Caetano [3]
Total Authors: 7
[1] Univ Paris Diderot, Inst Phys Globe Paris, Sorbonne Paris Cite, CNRS, F-75005 Paris - France
[2] Univ Granada, Dept Mineral & Petrol, Fac Sci, Campus Fuentenueva S-N, Granada 18002 - Spain
[3] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05505080 Sao Paulo - Brazil
[4] German Res Ctr Geosci GFZ, D-14473 Potsdam - Germany
[5] Geosci Montpellier UMR CNRS 5243, Pl E Bataillon, F-34090 Montpellier - France
[6] Univ Andres Bello, Carrera Geol, Sazie 2119, Santiago - Chile
Total Affiliations: 6
Document type: Journal article
Source: GEOLOGICAL SOCIETY OF AMERICA BULLETIN; v. 130, n. 9-10, p. 1439-1456, SEP 2018.
Web of Science Citations: 5

Diego de Almagro Island was formed by the subduction and accretion of several seafloor-derived tectonic slices with very heterogeneous ages and pressure-temperature-time (P-T-t) paths. The highest element of the pile (the Lazaro unit) evidences subduction in the high-P granulite field (similar to 1.3 GPa, 750 degrees C) at ca. 163 Ma. Below it, a thin tectonic sliver (the Garnet Amphibolite unit) preserves eclogite-facies remnants (-570 degrees C and similar to 1.7 GPa) formed at ca. 131 Ma (in situ U-Pb zircon rim ages). Peak assemblages were nearly fully amphibolitized during decompression down to similar to 1.2 GPa and similar to 600 degrees C at 125-120 Ma (Rb-Sr multimineral dating). The underlying Blueschist unit has similar to 50 m.y. younger metamorphic ages and exhibits slightly cooler peak burial conditions (similar to 520 degrees C, 1.7 GPa; ca. 80 Ma, in situ white mica Ar-Ar ages and multimineral Rb-Sr dating) and is devoid of amphibolitization. The mylonites from the sinistral strike-slip Seno Arcabuz shear zone bounding Diego de Almagro Island to the east also exhibit amphibolite-facies (similar to 620 degrees C and similar to 0.9 GPa) deformation at ca. 117 Ma (multimineral Rb-Sr ages). In situ white mica Ar-Ar dating and multimineral Rb-Sr dating of low- T mylonites (similar to 450 degrees C) along the base of the Lazaro unit reveal partial resetting of high-T assemblages during tectonic displacement between 115 and 72 Ma and exhumation of the slice stack. Detrital zircon U-Th-Pb ages indicate that the material accreted on Diego de Almagro Island has been mostly recycled from a Permian-Triassic accretionary wedge (Madre de Dios accretionary complex) exposed along the subduction buttress. Geological and geochronological constraints suggest that the rocks of the Seno Arcabuz shear zone and the Lazaro unit were tectonically eroded from the buttress, while the underlying Garnet Amphibolite and Blueschist units instead derive from the subducted oceanic basin, with increasingly younger maximum depositional ages. The very long residence time of the rocks (similar to 90 m.y. for the Lazaro unit) along the hanging wall of the subduction interface recorded long-term cooling along the Patagonian subduction zone during the Mesozoic. Diego de Almagro Island therefore represents a unique window onto long-term tectonic processes such as subduction interface down-stepping, tectonic erosion, and episodic underplating near the base of an accretionary wedge (40-50 km). (AU)

FAPESP's process: 12/01191-1 - Evolution of the paired metamorphic belt in the coastal cordillera of Central Chile: metamorphism and tectonics of the proto-andean margin in South American Continent
Grantee:Caetano Juliani
Support Opportunities: Regular Research Grants
FAPESP's process: 14/23422-0 - Unraveling the Dynamics of Paleo Subduction Complexes from Metamorphic Studies: The case of the Cretaceous High Pressure Accretionary Complex of Diego de Almagro (Chilean Patagonia)
Grantee:Thaís Nogueira Hyppolito
Support Opportunities: Scholarships in Brazil - Post-Doctoral