Indian MORB-type mantle beneath the Kuril Island arc: Isotopic investigation of the mafic lavas of Kunashir Island

Abstract

New data on the Hf, Pb, and Nd isotopes of the mafic rocks of various ages from Kunashir Island were used to address the nature of the sub arc mantle of the southern segment of the Kuril island arc. At least since Late Cenozoic, its isotopic characteristics have been the MORB type mantle of the Indian Ocean. Its boundary with the mantle reservoir of the Pacific MORB type coincided probably with the Kuril-Kam chatka Trench.

Missing western half of the Pacific Plate: Geochemical nature of the Izanagi‐Pacific Ridge interaction with a stationary boundary between the Indian and Pacific mantles

“…Geochemistry, Geophysics, Geosystems 10.1002/2015GC005911 et al, 2014M. Ban et al, JTABS project, unpublished data, 2015], Kurile [Martynov et al, 2012], and Japan Sea floor basalts [Hirahara et al, 2015] (Figure 6b). Additionally, DSDP/ODP sediment core sample data from southern Tonga [Pearce et al, 2007] and Izu [Chauvel et al, 2009] and basalt data from the Shatsky Rise [Heydolph et al, 2014] are plotted in Figure 6c.…”

“…[] reported that the radiogenic Pb was largely from the altered oceanic crust (AOC) of the Pacific Plate, and they proposed that the Pacific Plate younger than ∼125 Ma was generated from the previously subducted Izanagi‐Pacific Ridge (IPR) [ Nakanishi et al ., ], which produced MORBs of Indian mantle provenance (Indian‐type MORB or AOC) as young as 125 Ma. This proposal is contrary to previous models that relied on Pb‐Sr‐Nd isotopic geochemistry of the arc lavas to determine the provenance of the Indian mantle wedge [ Flower et al ., ; Hickey‐Vargas et al ., ; Kimura and Yoshida , ; Kimura and Nakajima , ; Kimura et al ., ; Martynov et al ., ; Pearce et al ., ].…”

“…The western Pacific is the hemispheric boundary of the Indian‐Pacific mantle domain, which has been examined by various combinations of Pb‐Nd‐Hf isotope systems such as the Kurile‐Japan‐Izu‐Mariana Trench [ Flower et al ., ; Hickey‐Vargas et al ., ; Hirahara et al ., ; Kimura and Yoshida , ; Kimura and Nakajima , ; Kimura et al ., ; Martynov et al ., ; Park et al ., ; Savov et al ., ; Woodhead et al ., ], Vitiaz‐Tonga Trench [ Pearce et al ., ], and Australia‐Antarctica Discordance [ Hanan et al ., ; Kempton et al ., ; Klein et al ., ; Pyle et al ., ]. The current global boundary of the two mantle domains is expected to be located along the N‐S‐trending Kurile‐Japan‐Izu and Mariana‐Vitiaz‐Tonga trenches and Australia‐Antarctica Discordance, rimming the western margins of the Pacific Ocean basin [ Machida et al ., ; Nebel et al ., ; Pearce et al ., ] (Figure a).…”

Comparison of petrology and isotope geochemistry of the Bulka peridotite–gabbro massif and granitoids of the Kyzykchadra complex (West Sayan)

“…The possible geochemical effects of subductionrelated processes on the composition of primary mantle material of suprasubduction zones have been discussed in detail in previous studies (Martynov et al, 2007(Martynov et al, , 2012Martynov and Kimura, 2009). These effects are reflected, in particular, in marked enrichment of the suprasubduction mantle wedge in LREE, LILE, Pb, and Sr.…”

“…At the same time, low-temperature aqueous fluids are less capable of mobilizing LREE, and depletion in LREE of island-arc rocks indicates the involvement of a subduction-related component in magma genesis (Martynov et al, 2012). Enrichment in Cs, Rb, Ba, U, Pb, and Sr and depletion in Nb, Ta, and LREE are typical of suprasubduction zone lavas generated with the involvement of a low-temperature aqueous fluid (Martynov and Kimura, 2009).…”