georefid:2012-069480SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2013-07-08T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1016/j.lithos.2012.04.014Geochemistry of basalts from IODP Site U1365; implications for magmatism and mantle source signatures of the mid-Cretaceous Osbourn Trough2012-01-01publicationgeorefid:2012-069480
doi:10.1016/j.lithos.2012.04.014
Zhang GuoliangChinese Academy of Sciences, Institute of Oceanology, Laboratory of Marine Geology and Environment, Qingdao, ChinaauthorSmith-Duque, ChristopherUniversity of Southampton, United KingdomauthorTang SuohanChinese Academy of Geological Sciences, Institute of Geology, ChinaauthorLi HeChinese Academy of Sciences, Institute of Geology and Geophysics, ChinaauthorZarikian, CarlosIntegrated Ocean Drilling Program Management International, United StatesauthorD'Hondt, StevenauthorInagaki, FumioauthorElsevier, Amsterdam, NetherlandspublisherdocumentHardcopyLithos (Oslo)144-14573-87The Integrated Ocean Drilling Program site U1365 drilled into the basement of the southwest Pacific crust formed from the mid-Cretaceous Osbourn Trough that rifted apart the Manihiki and Hikurangi Plateaus (the Greater Manihiki). The basalt geochemistry at this site is crucial for understanding the magmatic processes and mantle source of the mid-Cretaceous Osbourn Trough. The recovered fresh basalts were low-K tholeiitic normal (N) and depleted (D) mid-ocean ridge basalt (MORB). Their trace element and Sr-Nd isotope compositions indicate a Pacific-type mantle source rather than any significant influences from the nearby Louisville Seamount Chain or from the Greater Manihiki Plateau. Despite the presence of a plume head underneath the Osbourn Trough at its initial stage, the insignificance of a plume head could be explained by the long-distance (>1000 km) southward migration of the Osbourn Trough. Lavas at site U1365 vary from low-MgO (<6.9 wt.%) N-MORB at the bottom to high-MgO (8 wt.% to 9.5 wt.%) D-MORB and, then, to medium-MgO (7.3 wt.% to 8.2 wt.%) N-MORB according to their eruption sequences, which was accompanied by magma mixing in the magma reservoir. The D-MORB group lavas have higher melting degrees than those of N-MORB group based on their concentrations of TiO (sub 2) , Na (sub 2) O and CaO corrected for crystallization relative to MgO=7.8 wt.%. The major element compositions of the high-MgO D-MORB lavas were consistent with partial melting in the spinel-peridotite zone over a pressure interval from approximately 3.1 GPa to 2 GPa in the mantle. The significant overlap of N-MORB and D-MORB in Sr-Nd isotopes suggests that chemical differences between the two groups were derived from the mantle melting processes. Based on comparison with lavas from the East Pacific Rise where a positive correlation of mantle melting degree vs. spreading rate is shown, we suggest that the Osbourn Trough might have a full spreading rate of approximately 140 mm/yr. Thus, the slow ridge-like axial morphology of the Osbourn Trough should be a character of an extinct fast ridge. Abstract Copyright (2012) Elsevier, B.V.completedIsotope geochemistryIgneous and metamorphic petrologyalkaline earth metalsassemblagesbasaltschemical compositionCretaceousEast PacificExpedition 329geochemistryHikurangi TroughICP mass spectraigneous rocksIntegrated Ocean Drilling ProgramInvertebrataIODP Site U1365isotope ratiosisotopesmagmatismmajor elementsManihiki Plateaumantlemass spectraMesozoicmetalsmicrofossilsmid-ocean ridge basaltsmid-ocean ridgesMiddle CretaceousNd-144/Nd-143neodymiumocean floorsOsbourn TroughPacific OceanProtistaRadiolariarare earthssea-floor spreadingSouth PacificSoutheast PacificSouthwest PacificspectraSr-87/Sr-86stable isotopesstrontiumtrace elementsvolcanic rocksWest PacificX-ray fluorescence spectraurn:org.iodp:exp:329
urnlargerWorkCitationcampaignurn:org.iodp:exp:329:site:U1365
urnlargerWorkCitationstudyurn:org.iodp:exp:329
urnlargerWorkCitationcampaignEnglishgeoscientificInformation174.0000180.0000-43.0000-38.0000Hikurangi Trough
Includes appendices