High-Ca and low-Ca boninites from Chichijima, Bonin (Ogasawara) archipelago.

Yajima, Kazuhito; Fujimaki, Haruyuki

doi:10.2465/gkk.30.217

Cited by 16 publications

(16 citation statements)

References 36 publications

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“…; U mino & N akano ; original data), the J ohn B each V olcanics ( U mino & N akano ; I shizuka et al . ), low‐ S i boninite series of the M ikazukiyama F ormation ( Y ajima & F ujimaki ; U mino & N akano ; original data), tholeiite and calc‐alkaline rock series from H ahajima I sland G roup ( T aylor & N esbitt ; Y ajima et al . ; K anayama et al .…”

Section: Whole Rock Geochemistry Of Ogasawara Islandsmentioning

confidence: 99%

Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group, the Ogasawara Islands

2012

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The Ogasawara Islands mainly comprise Eocene volcanic strata formed when the Izu–Ogasawara–Mariana Arc began. We present the first detailed volcanic geology, petrography and geochemistry of the Mukojima Island Group, northernmost of the Ogasawara Islands, and show that the volcanic stratigraphy consists of arc tholeiitic rocks, ultra‐depleted boninite‐series rocks, and less‐depleted boninitic andesites, which are correlatable to the Maruberiwan, Asahiyama and Mikazukiyama Formations on the Chichijima Island Group to the south. On Chichijima, a short hiatus is identified between the Maruberiwan (boninite, bronzite andesite, and dacite) and Asahiyama Formation (quartz dacite and rhyolite). In contrast, these lithologies are interbedded on Nakodojima of the Mukojima Island Group. The stratigraphically lower portion of Mukojima is mainly composed of pillow lava, which is overlain by reworked volcaniclastic rocks in the middle, whereas the upper portion is dominated by pyroclastic rocks. This suggests that volcanic activity now preserved in the Mukojima Island Group records growth of one or more volcanoes, beginning with quiet extrusion of lava under relatively deep water followed by volcaniclastic deposition. These then changed into moderately explosive eruptions that took place in shallow water or above sea level. This is consistent with the uplift of the entire Ogasawara Ridge during the Eocene. Boninites from the Mukojima Island Group are divided into three types on the basis of geochemistry. Type 1 boninites have high SiO2 (>57.0 wt.%) and Zr/Ti (>0.022) and are the most abundant type in both Mukojima and Chichijima Island Groups. Type 2 boninites have low SiO2 (<57.1 wt.%) and Zr/Ti (<0.014). Type 3 boninites have 57.6–60.7 wt.% SiO2 and are characterized by high CaO/Al2O3 (0.9–1.1). Both type 2 and 3 boninites are common on Mukojima but are rare in the Chichijima Island Group.

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Section: Whole Rock Geochemistry Of Ogasawara Islandsmentioning

confidence: 99%

Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group, the Ogasawara Islands

2012

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“…Boninites are Mg‐rich (generally MgO >8 wt%), porphyritic (generally >20 vol.%) andesites with phenocrysts of olivine, clinoenstatite, bronzite, pigeonite and augite, set in a groundmass of glass and pyroxenes, but not plagioclase. Differentiated and primitive boninites (DBN and PBN in Table 1 after Yajima and Fujimaki [2001] and Umino and Kushiro [1989], respectively) are used here as a representative composition of the inferred IBM middle crust.…”

Section: Magma Compositions and Crystallization/melting Regimesmentioning

confidence: 99%

Structure and growth of the Izu‐Bonin‐Mariana arc crust: 2. Role of crust‐mantle transformation and the transparent Moho in arc crust evolution

Tatsumi¹,

Shukuno²,

Tani³

et al. 2008

J. Geophys. Res.

142

130

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Evolution of arc crust and subarc mantle in the Izu‐Bonin‐Mariana (IBM) intraoceanic arc‐trench system is examined by petrological modeling of arc magma generation and differentiation. Characteristic seismic structural features of the IBM arc highlighted in this modeling include the presence of (1) a middle crust with a P wave velocity (Vp) of 6.0–6.5 km/s, (2) a 6.5–6.8 km/s Vp layer at the top of the lower crust, (3) a high‐velocity (Vp = 6.8–7.2 km/s) lower crust, and (4) an uppermost mantle exhibiting rather low velocities (Vp = 7.4–7.7 km/s). The formation of the middle crust, which is considered to have an intermediate composition, is examined by (1) the mantle‐derived basalt model including anatexis of the initial mafic lower crust or mixing of mantle‐melting‐derived basaltic magma with crust‐melting‐derived felsic magma and (2) the mantle‐derived andesite model including differentiation of boninitic magma. The Vp calculated for the inferred compositions for each layer of the IBM crust on the basis of the basalt model is consistent with the observed values, whereas the andesite model cannot account for the characteristic Vp of the middle crust, the uppermost lower crust, and the uppermost mantle. The results further suggest that the volume of mafic restite and cumulates that are “crustal residues” resulting from the evolution of middle and upper arc crust is, at least, 3 to 9 times greater than that of the seismically defined IBM lower crust. One possible explanation to overcome this apparent dilemma is that the mafic to ultramafic crustal components are transformed to subarc mantle. During this process the subarc Moho is chemically transparent and permeable to the crustal components. This crust‐mantle transformation could play the major role in the creation of mature arc crust with intermediate compositions similar to continental crust.

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“…5. Olivine, orthopyroxene and spinel compositions of Zambales and Ogasawara boninite are almost identical except for a limited range of olivine Mg#, which is most likely due to a small number of samples analyzed (two for olivine and four for spinel), and lower spinel Cr# in Zambales boninite (Taylor et al, 1994;Umino, 1986;Yajima & Fujimaki, 2001). NiO contents of olivine range from 0.18-0.41 wt% and plot on fractionation trends from the mantle olivine array.…”

Section: Textures and Phase Chemistrymentioning

confidence: 99%

“…Figure 6 shows oxide vs. SiO2 variation diagrams of Zambales boninite and boninite series volcanics. Also shown are boninite and boninite series volcanics from Ogasawara (Kanayama et al, 2012;Nagaishi, 2008;Taylor et al, 1994;Umino & Nakano, 2007;Yajima & Fujimaki, 2001) and Holes U1439 and U1442 of IODP Expedition 352 (Haugen, 2017;Reagan et al, 2015). MgO, TiO2, CaO and Al2O3 contents of HSB and LSB 20 form subparallel trends suggesting distinct parental magma compositions and fractionation paths.…”

Section: Low-pressure Fractionation and Magma Mixingmentioning

confidence: 99%

Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins

Perez¹,

Umino²,

Yumul³

et al. 2018

Preprint

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Abstract.A key component of subduction initiation rock suites is boninite, a high-magnesium andesite that is uniquely predominant in Western Pacific forearc terranes and in select Tethyan ophiolites such as Oman and Troodos. We report the discovery of low-calcium, high-silica boninite in the middle Eocene Zambales ophiolite (Luzon island, Philippines). Olivine-15 orthopyroxene microphyric high-silica boninite, olivine-clinopyroxene-phyric low-silica boninite and boninitic basalt occur Paleolatitudes derived from tilt-corrected sites in the Acoje Block place the juvenile arc of northern Zambales ophiolite in 25 the western margin of the Philippine Sea Plate. In this scenario, the origin of Philippine Sea Plate boninites (IBM and Zambales) would be in a doubly-vergent subduction initiation setting.

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High-Ca and low-Ca boninites from Chichijima, Bonin (Ogasawara) archipelago.

Cited by 16 publications

References 36 publications

Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group, the Ogasawara Islands

Eocene volcanism during the incipient stage of Izu–Ogasawara Arc: Geology and petrology of the Mukojima Island Group, the Ogasawara Islands

Structure and growth of the Izu‐Bonin‐Mariana arc crust: 2. Role of crust‐mantle transformation and the transparent Moho in arc crust evolution

Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins

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