Geochemical Characteristics of Active Backarc Basin Volcanism at the Southern End of the Mariana Trough

Masuda, Harue; Fryer, Patricia

doi:10.1007/978-4-431-54865-2_21

Cited by 12 publications

(26 citation statements)

References 62 publications

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“…Whereas the southern flank of the DSZ has no small seamounts, the southern flank of the MGR has two groups of large seamounts. Both groups have been described as arc front-type volcanoes (Brounce et al, 2016;Masuda & Fryer, 2015). The second group consists of the Toto caldera (Gamo et al, 2004) and several smaller seamounts closer to the axis of the MGR (referred to as the Patgon-Masala Volcanic Chain by Masuda & Fryer, 2015).…”

Section: Seafloor Fabric In the Southern Mariana Marginmentioning

confidence: 99%

“…Both groups have been described as arc front-type volcanoes (Brounce et al, 2016;Masuda & Fryer, 2015). The second set of volcanic edifices, proximal to the MGR, are less faulted in general and possibly younger than the FNVC (Masuda & Fryer, 2015). The flanks of the volcanoes overlap rather than forming the distinct spaced edifices more typical of the arc volcanic front.…”

Section: Seafloor Fabric In the Southern Mariana Marginmentioning

confidence: 99%

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Diffuse Extension of the Southern Mariana Margin

et al. 2018

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Extension within the southern Mariana margin occurs both normal to and parallel to the trench. Trench‐normal extension takes place along focused and broad backarc spreading axes forming crust that is passively accreted to the rigid Philippine Sea plate flank to the northwest. To the southeast, trench‐parallel extension has split apart the Eocene‐Miocene forearc terrain accreting new crust diffusely over a 150–200 km wide zone forming a pervasive volcano‐tectonic fabric oriented at high angles to the trench and the backarc spreading center. Earthquake seismicity indicates active extension over this forearc region and basement samples date young although waning volcanic activity. Such diffuse formation of new oceanic crust and lithosphere is unusual; in most oceanic settings extension rapidly focuses to narrow plate boundary zones—a defining feature of plate tectonics. Diffuse crustal accretion has been inferred to occur during subduction zone infancy, however. We hypothesize that in a near‐trench extensional setting, the continual addition of water from the subducting slab creates a weak overriding hydrous lithosphere that deforms broadly. This process counteracts mantle dehydration and strengthening proposed to occur at mid‐ocean ridges that may help to focus deformation and melt delivery to narrow plate boundary zones. The observations from the southern Mariana margin suggest that where lithosphere is weakened by high water content narrow seafloor spreading centers cannot form. These conditions likely prevail during subduction zone infancy, explaining the diffuse contemporaneous volcanism inferred in this setting.

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Section: Seafloor Fabric In the Southern Mariana Marginmentioning

confidence: 99%

Section: Seafloor Fabric In the Southern Mariana Marginmentioning

confidence: 99%

Diffuse Extension of the Southern Mariana Margin

et al. 2018

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“…These seamounts are located at an extension of the Mariana Arc volcanoes. However, basaltic lavas collected from these seamounts show chemical affinities with those collected from the Mariana Trough backarc spreading axis and classified as a low-K series backarc basalt in a K 2 O-SiO 2 diagram (Fryer et al, 1998;Stern et al, 2013;Masuda and Fryer, 2015). Along with the lack of magmatic focusing to build a single stratovolcano, magmatism in the ASVP is not similar to that in normal arc volcanoes, but appears to be substantially related to extension tectonics in this region.…”

Section: Geologic Settingmentioning

confidence: 82%

Chemical composition of hydrothermal fluids in the central and southern Mariana Trough backarc basin

Ishibashi

Tsunogai

Toki

et al. 2015

Deep Sea Research Part II: Topical Studies in Oceanography

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“…We then compare these results with the composition of southeastern Mariana forearc rift (SEMFR, Figure 1) lavas in order to constrain the relationship between melts and fluids from the subducting Pacific plate and volcanism in the southern Mariana convergent margin. [Masuda and Fryer, 2015]. The basemap for plots a and b was created using GeoMapApp (http://www.geomapapp.org) [Ryan et al, 2009].…”

Section: Citationmentioning

confidence: 99%

“…White diamonds with gray outlines are data for the SEMFR [Ribeiro et al, 2013b]. Small gray circles are bulk pillow glass data for Fina Nagu samples dredged during cruise Hakuho, 1998, and described by Masuda and Fryer (2015). The white inverted triangles represent three MORB compositions.…”

Section: Dissolved H 2 O and Comentioning

confidence: 99%

The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

Brounce

Kelley

Stern

et al. 2016

Geochem Geophys Geosyst

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In the Mariana convergent margin, large arc volcanoes disappear south of Guam even though the Pacific plate continues to subduct and instead, small cones scatter on the seafloor. These small cones could form either due to decompression melting accompanying back-arc extension or flux melting, as expected for arc volcanoes, or as a result of both processes. Here, we report the major, trace, and volatile element compositions, as well as the oxidation state of Fe, in recently dredged, fresh pillow lavas from the Fina Nagu volcanic chain, an unusual alignment of small, closely spaced submarine calderas and cones southwest of Guam. We show that Fina Nagu magmas are the consequence of mantle melting due to infiltrating aqueous fluids and sediment melts sourced from the subducting Pacific plate into a depleted mantle wedge, similar in extent of melting to accepted models for arc melts. Fina Nagu magmas are not as oxidized as magmas elsewhere along the Mariana arc, suggesting that the subduction component responsible for producing arc magmas is either different or not present in the zone of melt generation for Fina Nagu, and that amphibole or serpentine mineral destabilization reactions are key in producing oxidized arc magmas. Individual Fina Nagu volcanic structures are smaller in volume than Mariana arc volcanoes, although the estimated cumulative volume of the volcanic chain is similar to nearby submarine arc volcanoes. We conclude that melt generation under the Fina Nagu chain occurs by similar mechanisms as under Mariana arc volcanoes, but that complex lithospheric deformation in the region distributes the melts among several small edifices that get younger to the northeast.

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Geochemical Characteristics of Active Backarc Basin Volcanism at the Southern End of the Mariana Trough

Cited by 12 publications

References 62 publications

Diffuse Extension of the Southern Mariana Margin

Diffuse Extension of the Southern Mariana Margin

Chemical composition of hydrothermal fluids in the central and southern Mariana Trough backarc basin

The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

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