georefid:2005-023613SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1180/0026461046860229<gco:CharacterString>Serpentine and brucite of ultramafic clasts from the South Chamorro Seamount (Ocean Drilling Program Leg 195, Site 1200); inferences for the serpentinization of the Mariana forearc mantle</gco:CharacterString>2004-01-01publicationgeorefid:2005-023613doi:10.1180/0026461046860229D'Antonio, M.Universita di Napoli Federico II, Dipartimento di Scienze della Terra, Naples, ItalyauthorKristensen, M. B.University of Aarhus, DenmarkauthorMineralogical Society, London, United KingdompublisherdocumentDigitalMineralogical Magazine68 (6)887-904Serpentine minerals and brucite in ultramafic rocks from the South Chamorro Seamount were characterized chemically to investigate the serpentinization of the Mariana forearc mantle. Relict primary minerals of the serpentinites are olivine, enstatite and minor Cr-spinel and diopside. The secondary minerals are mostly serpentine and brucite with minor magnetite. The serpentine minerals, mostly lizardite and chrysotile, display large compositional variations. Al (sub 2) O (sub 3) and Cr (sub 2) O (sub 3) contents depend generally upon the nature of the primary mineral from which the serpentine was derived. Both serpentine minerals and brucite exhibit wide Mg, Fe and Mn substitution: the Mg# ranges are 95.1-77.2 and 88.9-60.8, respectively. These mineralogical and chemical features allowed us to estimate an upper temperature limit for serpentinization of approximately 200-300 degrees C, in agreement with recent thermal models which suggest that the serpentinized mantle wedge of the Izu-Bonin-Mariana subduction zone is cold. The high degree of serpentinization (40-100%, average >75%), and the serpentine + brucite paragenesis of these ultramafics imply that the Mariana forearc mantle has a significantly reduced density and strength down to approximately 30 km, which provides a driving mechanism for serpentinite diapirism. Pervasive serpentinization of the forearc by fluids released from the decollement zone also explains the low seismicity of the Izu-Bonin-Mariana subduction zone.completedGeneral mineralogybruciteclastscrustLeg 195mantleMariana TrenchNorth PacificNorthwest PacificOcean Drilling Programoceanic crustODP Site 1200oxidesPacific Oceanpetrographyrelict materialssedimentary rocksserpentineserpentine groupsheet silicatessilicatesSouth Chamorro SeamountspinelvolcanoesWest Pacificurn:org.iodp:exp:195urnlargerWorkCitationcampaignurn:org.iodp:exp:195:site:1200urnlargerWorkCitationstudyurn:org.iodp:exp:195urnlargerWorkCitationcampaignEnglishgeoscientificInformation115.0000145.00005.000025.0000application/pdfunknownSEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContacthttp://www.minersoc.org/pages/e_journals/mm_authors.pdfdownload