Chang, Q.

Hanyu, T.

Hauff, Folkmar

Hirai, Y.

Hoernle, Kaj

Kimura, J.-I.

Miyazaki, T.

Tamura, Y.

Timm, Christian

Vaglarov, B.

Werner, Reinhard

OceanRep

Geophysical Research AbstractsVol. 21, EGU2019-6913, 2019EGU General Assembly 2019© Author(s) 2019. CC Attribution 4.0 license.Interaction between mafic magma and lithospheric mantle: Evidencefrom the geochemistry of olivines and olivine-hosted melt inclusions inlavas from Kibblewhite Volcano, Kermadec arcYasuhiro Hirai (1,2), Yoshihiko Tamura (2), Kaj Hoernle (3), Christian Timm (4), Folkmar Hauff (3), ReinhardWerner (3), Takeshi Hanyu (2), Bogdan Vaglarov (2), Qing Chang (2), Takashi Miyazaki (2), and Jun-Ichi Kimura(2)(1) Division of Natural System, Kanazawa University, Kanazawa, Ishikawa, Japan, (2) Japan Agency for Marine-EarthScience and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan, (3) GEOMAR Helmholtz Centre for Ocean Research,Kiel, Germany, (4) GNS Science, Lower Hutt, New ZealandDuring German R/V SONNE cruise (SO-255) mafic basaltic to magnesian andesitic lavas were recovered from theKermadec arc front volcano Kibblewhite (Hirai et al., EGU2018). Notably, these primitive lavas contain forsteriticolivines and olivine-hosted melt inclusions, which were re-homogenized using a heating stage. Here, we presentthe chemical variations of the melt inclusions and their host olivines and discuss the interaction between maficmelts and subarc lithospheric mantle.The olivines are divided into two groups based on their occurrence in different host rock and NiO contents. Olivines(Fo90.3−92.4) found as phenocrysts in ankaramites (olivine-clinopyroxene rich basalts; 50.4–50.6 wt.% SiO2; 13.1–13.5 wt.% MgO; Mg# = 71.8–72.1) show unusually low Ni contents (912–1462 ppm). Olivines (Fo91.0−92.2)occurring as xenocrysts in magnesian andesites (57.5–57.6 wt.% SiO2; 5.5–5.6 wt.% MgO; Mg# = 56.8–57.3)show higher Ni contents (1108–3057 ppm) than olivines in ankaramites.All re-homogenized melt inclusions have primitive basalt compositions (49.6–52.0 wt.% SiO2; 12.7–15.9 wt.%MgO, 0.36–0.58 wt.% TiO2, 1.2–2.0 wt.% Na2O+K2O, 0.06–0.37 wt.% SO3, and 0.05–0.20 wt.% Cl), whichcould represent parental melts for the ankaramites. However, melt inclusions hosted by olivines in ankaramites havelower Al2O3 and higher CaO contents than those hosted by olivine xenocrysts in magnesian andesites; CaO/Al2O3values are 1.2–1.6 and 0.9–1.3 respectively, indicating that there is a negative correlation between Ni contents inhost olivines and CaO/Al2O3 values in their melt inclusions.The variable Ni and constant Fo contents in the host olivines could be explained by an interaction of primarymafic melts with lithospheric mantle, which causes assimilation of pyroxenes in the lithosphere and simultaneousfractional crystallization of olivines (AFC; Kelemen, 1990; Tamura et al., 2018). Moreover, the high CaO/Al2O3values in the melt inclusions hosted by the ankaramite olivines cannot be produced by partial melting of lherzolite(e.g. as compilation by Médard et al., 2004). These melts have most likely extensively interacted with the subarclithospheric mantle. In addition, a negative correlation between Ni content in the host olivine and CaO/Al2O3 ratioin their melt inclusions supports the melt-mantle interaction. Conversely, xenocrystic olivines in the andesites withhigh Ni contents must have been crystallized from more primitive basaltic melts within lithospheric mantle priorto significant melt-mantle interaction. These olivines were then trapped by primary magnesian andesite magmasas xenocrysts.

Interaction between maﬁc magma and lithospheric mantle: Evidence from the geochemistry of olivines and olivine-hosted melt inclusions in lavas from Kibblewhite Volcano, Kermadec arc

http://oceanrep.geomar.de/46524/1/EGU2019-6913.pdf

Interaction between maﬁc magma and lithospheric mantle: Evidence from the geochemistry of olivines and olivine-hosted melt inclusions in lavas from Kibblewhite Volcano, Kermadec arc

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