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Initial subduction-related boninitic magmatism occurred between 48 and 44 Ma in the Izu-Bonin-Mariana (IBM) arc. High-Mg adakites and low-Ca boninites have been dredged from the Bonin Ridge fore-arc seamount. Whole-rock 40Ar/39Ar ages suggest that the boninite (44·0±1·4Ma) and adakite (43·1±1·0 and 40·8± 0·8 Ma) magmatism overlapped, or that the ad...
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... sample D7-684, olivine occurs as euhedral to subhedral phenocrysts that are commonly 1^2 mm in diameter. The average Mg# [Mg/(Mg þ Fe 2þ ), atomic ratio] and Ni contents of the olivine phenocrysts are 0·89 and 0·29 wt %, respectively (Table 2). Bronzite orthopyr- oxene is the most abundant phenocryst mineral, occurring as both euhedral phenocrysts and microlites, usually sur- rounded by clinopyroxene rims. ...
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... orthopyr- oxene is the most abundant phenocryst mineral, occurring as both euhedral phenocrysts and microlites, usually sur- rounded by clinopyroxene rims. The average Mg# of the bronzite phenocrysts is 0·88 ( Table 2). The groundmass is hyalopilitic in texture. ...
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... groundmass is hyalopilitic in texture. Ca-rich clinopyroxene occurs as euhedral to subhedral microlites embedded in the ground- mass glass, with an average Mg# of 0·71 (Table 2). Sub- calcic augite and Mg-pigeonite microlites have an average Mg# of 0·82 and 0·85, respectively (Table 2). ...
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... clinopyroxene occurs as euhedral to subhedral microlites embedded in the ground- mass glass, with an average Mg# of 0·71 (Table 2). Sub- calcic augite and Mg-pigeonite microlites have an average Mg# of 0·82 and 0·85, respectively (Table 2). Spinels occur as discrete microlites in groundmass in addition to inclusions within bronzite phenocrysts; their average Cr# [Cr/(Cr þ Mg), atomic ratio] is 0·80 (Table 2). ...
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... calcic augite and Mg-pigeonite microlites have an average Mg# of 0·82 and 0·85, respectively (Table 2). Spinels occur as discrete microlites in groundmass in addition to inclusions within bronzite phenocrysts; their average Cr# [Cr/(Cr þ Mg), atomic ratio] is 0·80 (Table 2). In sample D20-14, the average Mg# and Ni contents of the olivine phenocrysts are 0·89 and 0·26 wt %, respectively. ...
Citations
... [51]). Date sources: intraoceanic adakite of Tibet is from [49]; adakite of modern intra-oceanic arc is from [52,53]; adakite in Linxi is from [8]. ...
The petrogenesis and geodynamic implications of the early Paleozoic adakitic rocks in the east of Inner Mongolia remain topics of debate. In this study, petrology, zircon U–Pb age and Lu–Hf isotopic composition, whole-rock geochemistry and Sr–Nd isotopes from adakitic rocks. Zircon U–Pb dating results demonstrate that the formation age is 242.8±1.0Ma, 247Ma，which is the product of Early Triassic magmatism. Petrology and geochemical study have shown that the granodiorite have high SiO2 (66.93% ~69.40%), Al2O3(15.37% ~ 15.43%), MgO (1.35% ~1.55%), with LREE enrichment and HREE deficit，and they have high Sr, low Y. and high Sr/Y ratios, showing typical signatures of adakitic rocks. The εHf(t) values of zircon vary between +11.3 and +13.8, with a low whole-rock (87Sr/86Sr)i ( 0.703382 )and positive εNd(t) values, the average Mg# of the rock is 56.14, suggesting that adakite derived from partial melting of MORB, and magma interaction with the mantle. Comprehensive analysis suggests that during the Late Permian to Early Triassic, the subducted slab of the Paleo-Asian Ocean broke off, and the residual oceanic slab preserved in the mantle beneath the subduction zone underwent partial melting, generating adakitic magma.
... The adakites dredged from the Bonin forearc, with extremely high Sr and low Y contents, are coeval with or slightly postdate the J. Yang, R.N. Mitchell, C.J. Spencer et al. Gondwana Research 122 (2023) 112-124 boninites (Li et al., 2013). Isotopic fingerprints provide robust evidence that slab melts of Pacific altered basaltic crust are involved in low-silica boninite genesis . ...
... The adakites dredged from the Bonin forearc, with extremely high Sr and low Y contents, are coeval with or slightly postdate the J. Yang, R.N. Mitchell, C.J. Spencer et al. Gondwana Research 122 (2023) 112-124 boninites (Li et al., 2013). Isotopic fingerprints provide robust evidence that slab melts of Pacific altered basaltic crust are involved in low-silica boninite genesis . ...
... Their distinctive characteristics, such as highly refractory compositions (high Mg#; trace element depletion; Figs. 4e, 5a) and disequilibrium with olivine ( Fig. 4a), are likely inherited from parental melts/fluids, such as boninitic melts as proposed in other studies (e.g., Golowin et al., 2017;Li et al., 2013;Shen et al., 2020). Because Ti and Cr are incompatible and compatible elements, respectively, in clinopyroxene (Adam and Green, 2006;Ayers et al., 1997), they should be negatively correlated during partial melting, whereas the Ti abundances in the Lycian clinopyroxene correlate positively with Cr 2 O 3 contents (Fig. 6b). ...
Mantle wedge peridotites are characterized by extraordinarily depleted compositions and their genesis is still controversial. In this study, we present microstructural observations and mineral chemical analyses of mantle harzburgites in the Lycian ophiolite of SW Turkey that reveal their formation in a suprasubduction zone mantle wedge. The textures of clinopyroxene in the harzburgites, particularly chromite-clinopyroxene symplectites and grains containing mineral inclusions, do not support a partial melting origin. Zoning textures and the presence of additional phases within the orthopyroxene porphyroclasts indicate that they underwent melt/fluid infiltration. Olivine crystals and interstitial grains are enclosed in orthopyroxene porphyroclasts, implying that the orthopyroxene grains crystallized by consuming olivine. Chromite grains in the harzburgites not only have zoned, but also contain a variety of mineral inclusions. Amphibole grains in some of the harzburgites also have compositions similar to those in the chromitites. Therefore, all mineral phases in the Lycian harzburgites have well-preserved metasomatic signatures that overprinted their partial melting features. The enrichment of fluid-mobile elements, such as Cs, Rb, U, and Pb in clinopyroxene and amphibole, coupled with their high Mg# values (92.8–95.6 and 93.7–96.4, respectively), suggest formation by Cr- and Mg-rich, hydrous metasomatic melts/fluids. The consistent compositions of clinopyroxene and chromite in the harzburgites and chromitites, together with the decreasing intensity of alteration and crystallization temperature of amphibole in the chromitite pods through dunites to harzburgites, imply that the hydrous melts/fluids were partially released from chromite surfaces during chromitite formation and/or from dehydration of the metamorphic sole, which likely attributed to metasomatism at different depths. Moreover, chromite-hosted inclusions in the harzburgites may reflect the reaction before solidification of an inclusion-rich zone possibly signifying a rapid increase of chromite-oversaturated melt. Positive correlations between Cr and Al in pyroxenes of ophiolites are widely preserved in metasomatic mantle peridotites from different tectonic settings and thus they provide a robust chemical proxy for the metasomatism.
... Common high-Mg andesites include boninites on Bonin islands of Japan (Kuroda et al., 1978;Li et al., 2013c), high-Mg adakites from Adak Island, Alaska, USA (Kay, 1978;Yogodzinski and Kelemen, 1998;Kelemen et al., 2003a), bajaites in Baja California, Mexico (Saunders et al., 1987;Calmus et al., 2003), and sanukitic high-Mg andesites in SW Japan (Tatsumi, 2001(Tatsumi, , 2006Tatsumi and Hanyu, 2003;Tatsumi et al., 2006). Except for their high MgO contents, high-Mg andesites show similar compositions to the bulk continental crust. ...
... An alternative model has been proposed for the origin of continental arc andesite. It assumes the chemical reaction of hydrous, felsic melts derived from subducting oceanic crust with the mantle wedge peridotite at subarc depths and subsequent partial melting of these metasomatic mantle domains (Yogodzinski et al., 1995;Tatsumi, 2001Tatsumi, , 2006Calmus et al., 2003;Tatsumi and Hanyu, 2003;Li et al., 2013c;Chen et al., 2014Chen et al., , 2016Chen et al., , 2021Chen and Zhao, 2017). This model has gained support from the occurrence of high-Ni olivines from high-Mg andesites, which is ascribed to the reactive formation of metasomatic pyroxenites during infiltration of subducting slab-derived hydrous felsic melts into the mantle wedge (Straub et al., 2008(Straub et al., , 2011(Straub et al., , 2014Nishizawa et al., 2017). ...
... Although some major elements and fluid-mobile elements (Rb, U, K, and Pb) can be produced by this melting mechanism, it is difficult to account for the high contents of melt-mobile elements such as REE and some HFSE (Figs. 5A and 5B). In addition, the studied high-Mg andesites are evidently distinct from boninites with striking concave (U-shaped) REE patterns (Fig. 5A), which can be derived from partial melting of depleted peridotite sources with the addition of abundant slab-derived aqueous solutions and/or small proportions of hydrous melts at shallow depths (0.3-1.7 GPa) (Crawford et al., 1989;König et al., 2010;Li et al., 2013c). ...
Although high-Mg andesites (HMA) have attracted increasing attention due to their unique geochemical composition and important geological significance, there is no consensus on their petrogenesis. The present study indicates that the subducting terrigenous sediment-derived hydrous melts were incorporated into the mantle source of Paleozoic HMA in northwestern Tianshan, western China. These HMA are composed of basaltic andesite and andesite. They generally exhibit arc-type trace element distribution patterns and weakly enriched Sr-Nd-Hf isotope compositions. Some of them show remarkably higher Ba/La, Ba/Th, Rb/Nb, and U/Th ratios than normal mid-ocean ridge basalts (MORB). Furthermore, most of them are characterized by higher Th/Nb, Th/Yb, and Th/Nd ratios but lower Nb/U ratios relative to normal MORB, similar to those of terrigenous sediments. Whole-rock Nd isotopes covary with Rb/Nb and Th/Yb ratios, indicating contributions from both oceanic crust-derived aqueous solutions and terrigenous sediment-derived hydrous melts. Together with their high zircon δ18O values, it appears that the mantle source of the target HMA contains terrigenous sediment-derived hydrous melts in addition to subducting oceanic crust-derived aqueous solutions. In the studied HMA, the andesite generally exhibits higher contents of large-ion lithophile elements and light rare earth elements and more enrichments in Sr-Nd-Hf isotopes than the basaltic andesite. These differences indicate that the mantle source of andesite would contain more subducting sediment-derived hydrous melts than that of basaltic andesite. As a consequence, relatively Si-rich and Si-poor pyroxenite sources were respectively generated as the mantle sources of the andesite and basaltic andesite. This qualitative interpretation is verified by quantitative modeling of the geochemical transfer from subducting oceanic crust into the mantle wedge. Model calculations indicate that the addition of ∼3% oceanic crust-derived aqueous solutions and 4%−12% terrigenous sediment-derived hydrous melts into the mantle wedge peridotite can account for the geochemical compositions of the target HMA. Therefore, the HMA in northwestern Tianshan provide the geochemical evidence for the crust-mantle interaction during the oceanic subduction in the Paleozoic. As such, the subducting terrigenous sediment-derived hydrous melts play a dominant role in the composition of the lithochemically fertile, geochemically enriched mantle sources and thus in the origin of HMA above oceanic subduction zones.
... Experimental studies have shown that their genesis requires a refractory mantle source that experienced melting past clinopyroxene exhaustion in presence of water (Falloon and Danyushevsky 2000). In addition, an important body of literature has also interpreted the genesis of boninitic magmas as related to the presence of a depleted mantle source modified by interaction with siliceous slab melts (Bénard and Ionov 2012;Li et al. 2013;Pearce and Reagan 2019). Likewise, for the New Caledonia CE-boninites, Cluzel and coauthors (2016) have recently invoked a derivation from a residual mantle source re-enriched by slab (i.e. ...
... Overall, taking into account also the heterogenous geochemical signatures of the pre-obduction dikes (Cluzel et al. 2006), the observed geochemical and compositional variability of the melts from the New Caledonia proto-arc sequence is consistent with that attested in the modern forearc regions, which may include a large variety of volcanic products, ranging from boninites, adakites, island-arc tholeiites (IAT) and forearc basalts (FAB) (e.g. Li et al. 2013;Patriat et al. 2019;Shervais et al. 2021). These features have been related to the spatial and temporal evolution of the forearc systems during the early stages of their development (e.g. ...
The New Caledonia ophiolite represents a rare example of proto-arc section originated during subduction infancy. The sequence is dominated by refractory harzburgites overlain by ultramafic (dunites and wehrlites) and mafic (gabbronorites) lithologies.
In this contribution, we report the first occurrence of amphibole-bearing intrusives in the New Caledonia forearc sequence. This study deals with a petrological and geochemical investigation of a pyroxenite intrusion cut by mafic-ultramafic dikes. The intrusion consists of medium grain websterites, composed of orthopyroxene (30-75 vol.%), clinopyroxene (20-50 vol.%) and amphibole (2-30 vol.%), which occurs as interstitial or poikilitic phase. Whole rocks display moderate Mg# (71-82) and concave downward REE patterns, bearing depleted to flat LREE (LaN/NdN = 0.5-1) and flat HREE segments (DyN/LuN = 0.8-1.1). Bulk rocks mirror clinopyroxene at higher absolute values. Fluid mobile element (FME) enrichments, coupled to Zr-Hf depletion, are observed for both clinopyroxene and bulk rock.
Mineral major element variations and textural relationships indicate that the investigated lithotypes derived from primitive hydrous magmas, which underwent extensive fractional crystallisation and post-cumulus processes. Geochemical modelling shows that the parental melts in equilibrium with the pyroxenites share remarkable similarities with the New Caledonia CE-boninite. However, they significantly differ from the equilibrium melts previously reported for the other intrusive rocks of the sequence. As a whole, our new results highlight a greater compositional variability for the liquids ascending into the Moho transition zone and lower crust. This may be also related to the involvement of a highly heterogeneous mantle source during subduction initiation.
... The cooling of the subduction interface likely precluded further crustal melting, but permitted the generation of hydrous fluids from subducting basaltic crust and sediments that further fluxed this melt-modified residual mantle, and resulted in HSB magmatism. As the forearc gradually cooled, the locus of HSB volcanism appears to have moved westward, away from the trench, after~50 Myr, consistent with younger radiometric dates on HSB from the Bonin Islands (~48-46 Myr) and other localities inboard of the Expedition 352 drillsites [59][60][61] . Increased sediment subduction combined with a relatively cooler subduction interface leads to the relatively higher Cs/La and lower εNd i signatures of Bonin Islands HSB (Fig. 6). ...
... Trace element analyses were performed at Guizhou Tongwei Analytical Technology Co., Ltd. on a Thermal X series 2 ICP-MS equipped with a Cetac ASX-510 AutoSampler. After digestion, samples were dissolved in 3 ml of a 2 M HNO 3 stock solution that was then diluted to 4000:1 in 2% HNO 3 , and spiked with 12ppb 6 Li, 6ppb 61 Ni, Rh, In and Re, and 4.5ppb 235 U internal standards. The USGS reference material W-2a was used as reference standard and BIR-1, BHVO-2 and several other reference samples were crosschecked. ...
How subduction-related magmatism starts at convergent plate margins is still poorly understood. Here we show that boron isotope variations in early-formed boninites from the Izu-Bonin arc, combined with radiogenic isotopes and elemental ratios document rapid (~0.5 to 1 Myr) changes in the sources and makeup of slab inputs as subduction begins. Heterogeneous hornblende-granulite facies melts from ocean crust gabbros ± basalts fluxed early melting to generate low silica boninites. Hydrous fluids from slab sediments and basalts later fluxed the low silica boninites mantle source to produce high silica boninites. Our results suggest that initially the uppermost parts of the slab were accreted near the nascent trench, perhaps related to early low-angle subduction. The rapid changes in slab inputs recorded in the boninites entail a steepening subduction angle and cooling of the plate interface, allowing for subduction of slab sediment and basalt, and generating hydrous fluids at lower slab temperatures. The geochemical record of subduction initiation is still not well understood, despite >50 years of study. Here, the authors use boron isotopes in Izu-Bonin boninites to document rapid changes in slab inputs to melting at the start of subduction, related to the steepening and cooling of the downgoing Pacific plate.
... Elemental systematics with affinity to both MORB-and arc-like components are commonly considered to be directly related to the tectonic settings of fore-arc and back-arc (e.g., Hawkins, 1995). The magmatic rocks from a fore-arc basin generally have compound rock associations varying from boninitic and high-Mg andesitic to andesitic and felsic components (e.g., the Bonin fore-arc basin; Li et al., 2013). However, the volcanic sequence in the north belt is dominated by basalts, dacites, and rhyolites, with rare andesites, and does not show the geochemical characteristics of boninite or high-Mg andesite. ...
The southern Lhasa subterrane is the leading edge of the Tibetan Plateau and preserves important records of the Neo-Tethyan oceanic subduction and India–Asia collision. However, the early tectonic evolutionary history of the Neo-Tethyan oceanic subduction remains unclear. Here we present results from a systematic study on the early Mesozoic (Middle Triassic–Late Jurassic) magmatic and sedimentary rocks in the southern Lhasa subterrane. These rocks are distributed zonally along the southern and northern parts of the subterrane, and have been classified into the north and south belts. The magmatic rocks in the north belt show a back-arc basin affinity, with accreted bimodal volcanic sequence and sediments from central and southern Lhasa subterranes, whereas the magmatic rocks in the south belt reveal typical magmatic arc characteristics. The sediments were derived from southern Lhasa subterrane, without the input of clastic components from the central Lhasa subterrane. Based on geochronological, geochemical, and sedimentary records from both belts, we conclude that the early Mesozoic magmatism was triggered by the northward subduction of the Neo-Tethyan oceanic slab, and its initial subduction likely occurred before the Middle Triassic (ca. 240 Ma). During the Early–Middle Jurassic (ca. 193–165 Ma), a short-lived episode of back-arc extension, we attribute to roll-back of the subducting Neo-Tethyan slab, resulted in the single magmatic arc that existed during the early stages (ca. 240–194 Ma) and evolved gradually into an arc–back-arc system. The north belt represents a back-arc basin setting associated with a continental arc, whereas an intra-oceanic and continental (island) arc simultaneously developed in the south belt, and both these belts were possibly generated under the same subduction system.
... Later convection in the mantle wedge brought less-depleted source rocks into the region fluxed by slab fluids to yield arc basalts (Umino et al., 2015). Beginning with the boninites, the magma products from the IBM record strong slab signals (Fig. 1c), high water contents and high f O 2 (Brounce et al., 2015Umino et al., 2015), with variable contributions of water-rich slab melt flux from altered Pacific oceanic crust and pelagic sediment in a hot subduction setting (e.g., Coulthard Jr. et al., 2021;Li et al., 2019aLi et al., , 2013bUmino et al., 2015). ...
... The samples studied here were dredged from the Hahajima Seamount in the Bonin Ridge forearc primarily during the KH84-1, KH03-3, and KT04-28 cruises (Fig. S1). Detailed locations of the dredged sites with latitude and longitude coordinates are presented in Li et al. (2013b). They include FABs, boninites, high-Mg andesites (referred to here as high-Mg adakites due to their high Sr/Y values) and dacites (Li et al., 2013b). ...
... Detailed locations of the dredged sites with latitude and longitude coordinates are presented in Li et al. (2013b). They include FABs, boninites, high-Mg andesites (referred to here as high-Mg adakites due to their high Sr/Y values) and dacites (Li et al., 2013b). These samples have been well characterized, including detailed petrology, major, trace elements and radiogenic isotopes (Li et al., 2013b). ...
Addition of subducted materials from the slab to the mantle wedge is often thought to elevate the oxygen fugacity of arc magmas and also to fertilize the mantle wedge in metals for subduction-related Cu-Au deposits. However, it remains controversial if slab-driven metal addition is effective and whether it occurs at all stages of subduction. The Izu-Bonin-Mariana (IBM) forearc preserves a full record of arc development from the initiation of subduction of the Pacific plate to mature arc volcanism. Here, we study the ore-forming and redox-sensitive metal Cu and its isotopes (δ65Cu) in the type-locality forearc basalts (FABs), boninites and high-Mg andesites from the IBM forearc, as well as MORBs from the East Pacific rise. Overall, the FABs display variably high Cu contents and MORB-like δ65Cu, consistent with limited Cu isotopic fractionation during partial melting of typical MORB mantle sources. Beginning with the boninites, the magma products from the IBM record strong slab signals, high water contents and high fO2 (ΔFMQ > +1). However, the oxidized, hydrous boninites and subsequent high-Mg andesites display low Cu contents, and mantle-like Cu/Sc ratios and δ65Cu, with no clear indication of the addition of Cu from the slab. The boninites show noticeably lower TiO2, Yb and Cu contents than the FABs, consistent with refractory mantle sources. Combined with available data from boninites and arc basalts worldwide, our results lead to a general conclusion that subducted oceanic slabs from initial to mature subduction contribute little Cu to the mantle wedge. This is further supported by the compiled Cu contents of arc peridotites. Adding Cu-poor, water-rich slab melts to the mantle wedge at any stage of Pacific oceanic subduction causes limited release of Cu, which remains trapped predominantly by reduced sulfides in the subducting slab. This likely reflects the overall reducing nature of slab materials added to the mantle wedge. However, we propose that the subsequent reaction of such reducing, hydrous slab melts with peridotites and flux melting produce oxidized primitive arc magmas deep in the mantle wedge. The reactive process promotes sulfide dissolution and metal release from the mantle wedge itself to oxidized arc magmas with high sulfur solubility, which explains the inheritance of mantle-like δ65Cu and the sulfide-undersaturated early-stage evolution in boninites and arc basalts. This study elucidates the role of subducted oceanic slabs in metal transfer and redox evolution and implies no significant Cu enrichment in the metasomatized mantle sources of magmatic arcs.
... magmas with reduced MgO and Mg# are not in equilibrium with mantle peridotites. The role of the mantle wedge peridotites in the genesis of arc high-Mg andesites has increasingly been stressed (Blatter & Carmichael, 1998, 2001Hirose, 1997;Hirose & Kawamoto, 1995; Y. B. Li et al., 2013;H. Y. Li et al., 2019;Xu et al., 2020), for example, the origin of boninites from partial melting of hydrous mantle peridotites (Wood & Turner, 2009) and adakites from reaction of slab melts with mantle wedge peridotites (Kelemen, 1995;Kelemen et al., 2003;Li et al., 2013;Wang, Wyman, Xu, Zi, et al., 2008). ...
... The role of the mantle wedge peridotites in the genesis of arc high-Mg andesites has increasingly been stressed (Blatter & Carmichael, 1998, 2001Hirose, 1997;Hirose & Kawamoto, 1995; Y. B. Li et al., 2013;H. Y. Li et al., 2019;Xu et al., 2020), for example, the origin of boninites from partial melting of hydrous mantle peridotites (Wood & Turner, 2009) and adakites from reaction of slab melts with mantle wedge peridotites (Kelemen, 1995;Kelemen et al., 2003;Li et al., 2013;Wang, Wyman, Xu, Zi, et al., 2008). However, boninites are considered to be the product of early subduction, while the origin of adakites requires subducting slab with ages younger than 25 Ma (Castillo, 2012;Kay, 1978). ...
Andesitic to rhyolitic arc volcanism commonly occurs in the cold subduction system in the modern western Pacific, however, their genesis remains debated. The high-Mg andesitic arc rocks with enrichments of Th and K are suggested to be derived from a contribution of the subducted sediments and the depleted mantle wedge. The partial melts of pure sediments have MgO too low to explain the origin of such high-Mg arc rocks. For a cold subduction system, melting of subducted slab can unlikely occur, while sediment diapirism serves as a possible mechanism to contribute to the origin of arc volcanism. Here, we conducted high-pressure experiments on the mixed sediment (±CaCO3) and peridotite with proportions of 7:3 and 5:5 at 3.5 GPa and 1000–1300°C. The experiment resulted in andesitic to rhyolitic melts with elevated MgO and enriched K2O. All melts reduce in K2O with increasing temperatures as no K-rich minerals were produced. The interactions between carbonate-bearing sediments and peridotites during the diapirism promote decarbonation and produce melts with elevated MgO. The results of the experiments can explain the origin of high-Mg and K-rich andesite-rhyolite series of the Izu-Bonin-Mariana arc system. A higher sediment proportion used in the experiment is coupled with a stronger effect of garnet, which explains the volcanic rocks with higher K2O and La/Yb. We propose that sediment diapirism in the mantle wedge can produce high-Mg and K-rich andesitic-rhyolitic arc lavas and facilitate decarbonation of subducted sedimentary carbonates in the typical cold Izu-Bonin-Mariana subduction zone.
