U-series Isotope Data on Lau Basin Glasses: the Role of Subduction-related Fluids during Melt Generation in Back-arc Basins

Peate, David W.; Kokfelt, Thomas F.; Hawkesworth, Chris J.; Calsteren, P. W. van; Hergt, Janet M; Pearce, Julian A.

doi:10.1093/petrology/42.8.1449

Cited by 102 publications

(146 citation statements)

References 81 publications

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“…Between the MGR and the DSC sidescan sonar imagery shows high backscatter, numerous small volcanic cones and overlapping lobate flows, indicative of recent resurfacing by volcanism. This is similar to what is observed at the southern end of the Valu Fa ridge, where backarc spreading is propagating into the arc volcanic region (Peate et al 2001). The most important change in magmatic activity that happens during the formation of a backarc basin is the transition from arc igneous activity to true sea-floor spreading and new lithosphere formation.…”

Section: Discussionsupporting

confidence: 82%

“…They also suggested that the increasing H 2 O and Ba/La ratio were evidence of relationship of slab-derived water affecting backarc magma production in other parts of the Mariana Trough. Based on the U-series isotope characteristics of the rocks in the Valu Fa ridge, a similar mantle chemistry was presumed beneath the arc and backarc spreading areas in the Lau Basin, whereas slab-derived water contributes less in the backarc spreading ridge than in the arc (Peate et al 2001). The enrichment of Ba in the seamounts north of 13 N ( Fig.…”

Section: Discussionmentioning

confidence: 84%

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

Masuda

Fryer

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Major and minor chemistry, Sr, Nd and Pb isotope ratios, water content and hydrogen isotope ratios of the backarc basin volcanic rocks taken from the active spreading ridge and surrounding area between 12 40 0 N and 13 15 0 N in the southern part of the Mariana Trough indicate a complex regional interplay of suprasubduction-zone magmatic sources.In this area, active backarc spreading occurs along the eastern side of the Mariana Trough, and discrete seamounts align on two parallel chains east of the backarc spreading center. The spreading-center rocks originated from a typical mid-ocean ridge basalt (MORB)-like source, influenced progressively southwestward by proximity to the arc magmatic source and range from basaltic to dacitic in composition. The volcanic rocks from the seamount chains are explained by the mixing of two types of magmatic sources; one is originally a depleted mantle similar to the arc source for magmas farther north and the other is the MORB-like source of the spreading ridge rocks. The influence of the arc source on magma composition of the seamount chains is higher north of 13 N, indicating heterogeneity of the mantle wedge in this region and the merging of the two sources toward the southwest.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 84%

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

Masuda

Fryer

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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“…Spreading centers now advect ambient MORB-source mantle and their crustal accretion characteristics are like MORs. lavas are LREE-depleted and MORB-like, with low water contents (V0.3%) and only very slight enrichments in LILE and depletions in Ta, Nb [35,37,44]. With average ridge depths of V2300 m, the CLSC and MSC end-member Fe8 and Na8 values (10.5%, 2.25%, Fig.…”

Section: Normal Magmatismmentioning

confidence: 95%

Back-arc basin basalt systematics

Taylor

Martínez

2003

Earth and Planetary Science Letters

410

253

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The Mariana, east Scotia, Lau, and Manus back-arc basins (BABs) have spreading rates that vary from slow ( 6 50 mm/yr) to fast ( s 100 mm/yr) and extension axes located from 10 to 400 km behind their island arcs. Axial lava compositions from these BABs indicate melting of mid-ocean ridge basalt (MORB)-like sources in proportion to the amount added of previously depleted, water-rich, arc-like components. The arc-like end-members are characterized by low Na, Ti and Fe, and by high H 2 O and Ba/La; the MORB-like end-members have the opposite traits. Comparisons between basins show that the least hydrous compositions follow global MORB systematics and an inverse correlation between Na8 and Fe8. This is interpreted as a positive correlation between the average degree and pressure of mantle melting that reflects regional variations in mantle potential temperatures (Lau/Manus hotter than Mariana/Scotia). This interpretation accords with numerical model predictions that faster subduction-induced advection will maintain a hotter mantle wedge. The primary compositional trends within each BAB (a positive correlation between Fe8, Na8 and Ti8, and their inverse correlation with H 2 O(8) and Ba/La) are controlled by variations in water content, melt extraction, and enrichments imposed by slab and mantle wedge processes. Systematic axial depth (as a proxy for crustal production) variations with distance from the island arc indicate that compositional controls on melting dominate over spreading rate. Hydrous fluxing enhances decompression melting, allowing depleted mantle sources just behind the island arc to melt extensively, producing shallow spreading axes. Flow of enriched mantle components around the ends of slabs may augment this process in transform-bounded back-arcs such as the east Scotia Basin. The re-circulation (by mantle wedge corner flow) to the spreading axes of mantle previously depleted by both arc and spreading melt extraction can explain the greater depths and thinner crust of the East Lau Spreading Center, Manus Southern Rifts, and Mariana Trough and the very depleted lavas of east Scotia segments E8/E9. The crust becomes mid-ocean ridge (MOR)-like where the spreading axes, further away from the island arc and subducted slab, entrain dominantly fertile mantle. ß

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“…This includes data from the L'Esperance (Ewart et al 1994(Ewart et al , 1998Turner et al 1997) and the Rumble III and IV (Wysoczanski et al 2006(Wysoczanski et al , 2012 island arc volcanoes, as well as from the Valu Fa Ridge (Davis et al 1990;Vallier et al 1991;Peate et al 2001;Haase et al 2002;Fretzdorff et al 2006;Jenner et al 2015) and the Pual Ridge (Kamenetsky et al 2001;Moss and Scott 2001;Scott 2002, 2005;Sun et al 2004;Jenner et al 2010Jenner et al , 2012, as examples for back-arc volcanism. Three groups of major elements can be distinguished based on their behaviour during magma evolution, i.e., with increasing SiO 2 , including elements with an (1) incompatible (K 2 O, Na 2 O), (2) compatible (MgO, Al 2 O 3 , CaO) and (3) an initially incompatible and later compatible (TiO 2 , FeO T ) character (Fig.…”

Section: Lava Compositionmentioning

confidence: 99%

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

Keith

Haase

Klemd

et al. 2018

Contrib Mineral Petrol

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Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L'Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu > 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe-Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal-porphyry deposits.

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U-series Isotope Data on Lau Basin Glasses: the Role of Subduction-related Fluids during Melt Generation in Back-arc Basins

Cited by 102 publications

References 81 publications

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

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

Back-arc basin basalt systematics

Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

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