TY - JOUR
T1 - Lead isotope signatures of Kerguelen plume-derived olivine-hosted melt inclusions
T2 - Constraints on the ocean island basalt petrogenesis
AU - Borisova, Anastassia Y.
AU - Faure, François
AU - Deloule, Etienne
AU - Grégoire, Michel
AU - Béjina, Frédéric
AU - de Parseval, Philippe
AU - Devidal, Jean Luc
PY - 2014/6
Y1 - 2014/6
N2 - The nature of magmatic sources reflected by isotopic composition of the ocean island basalt (OIB) remains an on-going question in igneous geochemistry. To constrain the magmatic sources for OIB related to the Kerguelen plume activity, we performed detailed microanalytical investigation of the 21.4Ma picritic basalt (MD109-D6-87) dredged during the "Marion Dufresne" cruise on a seamount between Kerguelen Archipelago and Heard Island. Lead isotope compositions of olivine-hosted melt inclusions and matrix glasses were measured by Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS). We also performed major and trace element microanalyses and mapping of the inclusions and the host olivine phenocrysts by electron microprobe (wavelength-dispersive X-ray spectroscopy, WDS). The observed significant major element (K2O/P2O5, Al2O3/TiO2) and Pb isotope (207Pb/206Pb and 208Pb/206Pb) heterogeneities of parental melts (MgO=7-10wt.%) during early high pressure crystallisation stage (200-300MPa, Fo82-86mol%), and relative homogeneity at later lower-pressure crystallisation stage (<100MPa, Fo75-80mol%) are interpreted by mixing between "Plume" and "Assimilant" melts during magma residence and transport. Lead isotope composition of the parental basaltic melts was inherited from both heterogeneous mantle and the Kerguelen Plateau crust. High K2O/P2O5 (>4), Al2O3/TiO2 (>4) ratios are attributed to assimilation of the plateau basaltic crust (≥50wt.%) by the melts in the magma chamber at palaeodepths from 6 to 9km. The crustal assimilation may have happened through plagioclase dissolution. The large chemical and isotopic heterogeneity of the parental OIB melts found by in situ microanalyses in this study suggests that the bulk rock chemistry alone cannot provide enough information to constrain the nature of the magmatic sources.
AB - The nature of magmatic sources reflected by isotopic composition of the ocean island basalt (OIB) remains an on-going question in igneous geochemistry. To constrain the magmatic sources for OIB related to the Kerguelen plume activity, we performed detailed microanalytical investigation of the 21.4Ma picritic basalt (MD109-D6-87) dredged during the "Marion Dufresne" cruise on a seamount between Kerguelen Archipelago and Heard Island. Lead isotope compositions of olivine-hosted melt inclusions and matrix glasses were measured by Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS). We also performed major and trace element microanalyses and mapping of the inclusions and the host olivine phenocrysts by electron microprobe (wavelength-dispersive X-ray spectroscopy, WDS). The observed significant major element (K2O/P2O5, Al2O3/TiO2) and Pb isotope (207Pb/206Pb and 208Pb/206Pb) heterogeneities of parental melts (MgO=7-10wt.%) during early high pressure crystallisation stage (200-300MPa, Fo82-86mol%), and relative homogeneity at later lower-pressure crystallisation stage (<100MPa, Fo75-80mol%) are interpreted by mixing between "Plume" and "Assimilant" melts during magma residence and transport. Lead isotope composition of the parental basaltic melts was inherited from both heterogeneous mantle and the Kerguelen Plateau crust. High K2O/P2O5 (>4), Al2O3/TiO2 (>4) ratios are attributed to assimilation of the plateau basaltic crust (≥50wt.%) by the melts in the magma chamber at palaeodepths from 6 to 9km. The crustal assimilation may have happened through plagioclase dissolution. The large chemical and isotopic heterogeneity of the parental OIB melts found by in situ microanalyses in this study suggests that the bulk rock chemistry alone cannot provide enough information to constrain the nature of the magmatic sources.
KW - Crustal assimilation
KW - DUPAL isotope anomaly
KW - Kerguelen plume
KW - Melt inclusions
KW - Melt mixing
KW - Ocean island basalt
UR - http://www.scopus.com/inward/record.url?scp=84899073083&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2014.03.022
DO - 10.1016/j.lithos.2014.03.022
M3 - Article
AN - SCOPUS:84899073083
SN - 0024-4937
VL - 198-199
SP - 153
EP - 171
JO - Lithos
JF - Lithos
IS - 1
ER -