Shallow forearc mantle dynamics and geochemistry: New insights from IODP Expedition 366

Autor: Roy E. Price, Baptiste Debret, Helen M. Williams, Elmar Albers, Jaime D. Barnes, B. Walter, David P. Gillikin, Hugues Beunon, Nadine Mattielli, Sébastien P. Facq
Přispěvatelé: Apollo - University of Cambridge Repository, Laboratoire Géochimie, Traçage Isotopique, Minéral et élémentaire - G-Time (Bruxelles, Belgium), Department of Earth Sciences [Cambridge, UK], University of Cambridge [UK] (CAM), Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, GeoRessources, Institut national des sciences de l'Univers (INSU - CNRS)-Centre de recherches sur la géologie des matières premières minérales et énergétiques (CREGU)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), School of Marine and Atmospheric Sciences [Stony Brook] (SoMAS), Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), Jackson School of Geosciences (JSG), University of Texas at Austin [Austin], Union College, UK Research & Innovation (UKRI)Natural Environment Research Council (NERC), National Science Foundation (NSF), U.S. Science Support Program (USSSP) post-expedition activity (PEA), IODP-France, German Research Foundation, Special Priority Program 527 (IODP/ODP), Fonds de la Recherche Scientifique - FNRS, Fondation Wiener Anspach, European Project: 306655,EC:FP7:ERC,ERC-2012-StG_20111012,HABITABLEPLANET(2013)
Rok vydání: 2019
Předmět:
Zdroj: Lithos, 326-327
Lithos
Lithos, 2019, 326, pp.230-245. ⟨10.1016/j.lithos.2018.10.038⟩
ISSN: 0024-4937
DOI: 10.1016/j.lithos.2018.10.038
Popis: The Mariana forearc is a unique setting on Earth where serpentinite mud volcanoes exhume clasts originating from depths of 15 km and more from the forearc mantle. These peridotite clasts are variably serpentinized by interaction with slab derived fluid, and provide a record of forearc mantle dynamics and changes in geochemistry with depth. During International Oceanic Discovery Program (IODP) Expedition 366, we recovered serpentinized ultramafic clasts contained within serpentinite muds of three different mud volcanoes located at increasing distance from the Mariana trench and at increasing depth to the slab/mantle interface: Yinazao (distance to the trench: 55 km / depth to the slab/mantle interface: 13 km), Fantangisña (62 km / 14 km) and Asùt Tesoru (72 km / 18 km). Four different types of ultramafic clasts were recovered: blue serpentinites, lizardite-serpentinites, antigorite/lizardite- and antigorite-serpentinites. Lizardite-serpentinites are primarily composed of orange serpentine, forming mesh and bastite textures. Raman and microprobe analyses revealed that these textures contain a mixture of Fe-rich brucite (XMg ~ 0.84) and lizardite/chrysotile. Antigorite/lizardite- and antigorite-serpentinites record the progressive recrystallization of mesh and bastite textures to antigorite, magnetite and pure Fe-poor brucite (XMg ~ 0.92). Oxygen isotope compositions of clasts and pore fluids showed that the transition from lizardite to antigorite is due to the increase in temperature from 200 °C to about 400 °C within the forearc area above the slab/mantle interface. Lizardite-, antigorite/lizardite- and antigorite-serpentinites displayed U-shaped chondrite normalized Rare Earth Element (REE) patterns and are characterized by high fluid mobile element concentrations (Cs, Li, Sr, As, Sb, B, Li) relative to abyssal peridotites and/or primitive mantle. The recrystallization of lizardite to antigorite is accompanied by a decrease in Cs, Li and Sr, and an increase in As and Sb concentrations in the bulk clasts, whereas B concentrations are relatively constant. Some clasts are overprinted by blue serpentine, often in association with sulfides. Most of these blue serpentinites were recovered at Yinazao and the uppermost units of Fantangisña and Asùt Tesoru suggesting alteration in the shallower portions of the forearc, possibly during exhumation of the clasts. This episode of alteration resulted in a flattening of REE spectra and an increase of Zn concentrations in serpentinites. Otherwise, no systematic changes of ultramafic clasts chemistry or mineralogy were observed with increasing depth to the slab. The samples document previously undescribed prograde metamorphic events in the shallow portions of the Mariana subduction zone, consistent with a continuous burial of the serpentinized forearc mantle during subduction. Similar processes, induced by the interaction with fluids released from the downgoing slab, likely occur in subduction zones worldwide. At greater depth, breakdown of brucite and antigorite will result in the massive transfer of fluids and fluid mobile elements, such as As, Sb and B, to the source of arc magmas.
SCOPUS: ar.j
info:eu-repo/semantics/published
Databáze: OpenAIRE
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