Basalts from the Efate Island Group, central section of the Vanuatu arc, SW Pacific: geochemistry and petrogenesis

Raos, Alison M; Crawford, Anthony J.

doi:10.1016/j.jvolgeores.2003.12.004

Cited by 36 publications

(34 citation statements)

References 38 publications

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“…Tavua rock data include analyses from Rogers and Setterfield [1994]. Data sources are as follows: MORB field, Danyushevsky [2001]; Tonga‐Kermadec arc tholeiite field, Gamble et al [1993] and Turner et al [1997]; Vanuatu calc‐alkaline field, Barsdell [1988], Barsdell and Berry [1990], Crawford et al [1988], Eggins [1993], Monzier et al [1997], and Raos and Crawford [2004]; Mariana shoshonitic field, Lin et al [1989] and Sun and Stern [2001]; Tabar‐Feni shoshonitic field, Kennedy et al [1990] and Stracke and Hegner [1998].…”

Section: Discussionmentioning

confidence: 99%

“…(c) Average trace element abundance of Fijian absarokites normalized to average Vanuatu arc medium‐K calc‐alkaline composition. Data sources are as follows: Tonga Kermadec arc tholeiites, Gamble et al [1993] and Turner et al [1997]; Vanuatu medium‐K calk‐alkaline rocks, Barsdell [1988], Barsdell and Berry [1990], Crawford et al [1988], Eggins [1993], Monzier et al [1997], and Raos and Crawford [2004].…”

Section: Trace Elementsmentioning

confidence: 99%

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Primitive shoshonites from Fiji: Geochemistry and source components

Leslie

Danyushevsky

Crawford

et al. 2009

Geochem Geophys Geosyst

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[1] The eruption of shoshonitic magmas in Fiji during the Late Miocene-Pliocene (5.5-3 Ma) from 11 main volcanic centers along three broad ENE and NNW trending lineaments coincides with welldeveloped spreading in the North Fiji and Lau back-arc basins and maximum rotation of the Fiji Platform. The most mafic shoshonitic lavas (absarokites) range from 8.4 to 15.2 wt % MgO and are variably clinopyroxene + olivine-phyric. Fijian shoshonitic suites display a range of enrichment in large ion lithophile elements, Th, U, and P relative to rare earth elements and high field strength elements (HFSE), reflecting variable contributions by the subarc mantle source and subduction-related components. The subarc mantle source component controls HFSE, heavy rare earth elements, to a lesser degree light rare earth elements (LREE), and most importantly the sensitivity of the mantle source with respect to subduction-related enrichment processes, whereas Pb, K, Sr, Ba, Rb, Th, U, P 2 O 5 , and LREE are contributed by hydrous or supercritical fluid(s) and sediment melts that are added to the subarc mantle. Fijian shoshonitic suites situated $150 km apart display a wide range of Nb/Yb (0.3-4.3), implying that there is significant spatial heterogeneity in the sub-Fijian mantle with respect to the ambient fertility of mantle sources independent of subduction-related enrichment. The range in incompatible element ratios (e.g., Th/Nb, U/Nb, Ba/Th, Ba/La, P/Nd, and Ce/Pb) displayed by Fijian shoshonitic suites cannot reflect addition of the same subduction-derived component to variably enriched subarc mantle sources. Differences in the relative amount of fluid versus sediment melt and potentially the composition of the subducted sediment are required to explain the data. The greater overall subduction-related enrichment in Fijian shoshonites relative to calk-alkaline and tholeiitic arc magmas is attributed to a melt generation process involving low-degree partial melting of metsomatized subarc lithosphere in contrast to magmas associated with active or steady state arcs, where higher degrees of melting occur in response to volatile fluxing of the mantle wedge. Shoshonitic magma generation occurs in linear zones during extension of the arc lithosphere preceding arc fragmentation and establishment of back-arc spreading centers.

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Section: Discussionmentioning

confidence: 99%

Section: Trace Elementsmentioning

confidence: 99%

Primitive shoshonites from Fiji: Geochemistry and source components

Leslie

Danyushevsky

Crawford

et al. 2009

Geochem Geophys Geosyst

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“…In the Lesser Antilles and eastern Aleutians the continental signature may reflect recycling of a component derived from subducting continental sediments 23,24 . The geochemistry of Vanuatu magmas is influenced by the subduction of intraplate seamounts and an aseismic ridge 25 . Most of Izu-Bonin, Marianas, South Scotia and Tonga arcs with a CI of >100 have the least continent-like geochemical signatures.…”

Section: Global Survey Of Intra-oceanic Arcsmentioning

confidence: 99%

Continental crust generated in oceanic arcs

et al. 2015

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Thin oceanic crust is formed by decompression melting of the upper mantle at mid-ocean ridges, but the origin of the thick and buoyant continental crust is enigmatic. Juvenile continental crust may form from magmas erupted above intraoceanic subduction zones, where oceanic lithosphere subducts beneath other oceanic lithosphere. However, it is unclear why the subduction of dominantly basaltic oceanic crust would result in the formation of andesitic continental crust at the surface. Here we use geochemical and geophysical data to reconstruct the evolution of the Central American land bridge, which formed above an intra-oceanic subduction system over the past 70 Myr. We find that the geochemical signature of erupted lavas evolved from basaltic to andesitic about 10 Myr ago-coincident with the onset of subduction of more oceanic crust that originally formed above the Galápagos mantle plume. We also find that seismic P-waves travel through the crust at velocities intermediate between those typically observed for oceanic and continental crust. We develop a continentality index to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust globally. We conclude that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone-a process probably more common in the Archaean-can produce juvenile continental crust.

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“…The silicic lithologies on Efate are overlain by basalts of the Basalt Volcanoes Formation (BVF), as defined by Ash, et al, [23]. The BVF basalts were erupted in two episodes from 0.7 Ma; the older episode comprises subaerial and shallow subaqueous lava, breccia and intrusive rocks that form the remnant composite cones of Quoin Hill and Mt Fatmalapa ( Figure 1) and the younger comprises the subaerial pahoehoe lavas, autobreccias and pyroclastic rocks of Nguna, Emau and Pele Islands (Figures 1, 2A, C, D) [24]. Development of at least 5 coral reef terraces over the last 0.3 Ma [25] records uplift of at least 600 m subsequent to the emplacement of the BVF rocks and places a minimum age on the BVF formation [26].…”

Section: Geology Of Efate and Adjacent Islandsmentioning

confidence: 99%

Is Efate (Vanuatu, SW Pacific) a result of subaerial or submarine eruption? An alternative model for the 1 Ma Efate Pumice Formation

2010

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Abstract:The Efate Pumice Formation (EPF) is a trachydacitic volcaniclastic succession widespread in the central part of Efate Island and also present on Hat and Lelepa islands to the north. The volcanic succession has been inferred to result from a major, entirely subaqueous explosive event north of Efate Island. The accumulated pumice-rich units were previously interpreted to be subaqueous pyroclastic density current deposits on the basis of their bedding, componentry and stratigraphic characteristics. Here we suggest an alternative eruptive scenario for this widespread succession. The major part of the EPF is distributed in central Efate, where pumiceous pyroclastic rock units several hundred meters thick are found within fault scarp cliffs elevated about 800 m above sea level. The basal 200 m of the pumiceous succession is composed of massive to weakly bedded pumiceous lapilli units, each 2-3 m thick. This succession is interbedded with wavy, undulatory and dune bedded pumiceous ash and fine lapilli units with characteristics of co-ignimbrite surges and ground surges. The presence of the surge beds implies that the intervening units comprise a subaerial ignimbritedominated succession. There are no sedimentary indicators in the basal units examined that are consistent with water-supported transportation and/or deposition. The subaerial ignimbrite sequence of the EPF is overlain by a shallow marine volcaniclastic Rentanbau Tuffs. The EPF is topped by reef limestone, which presumably preserved the underlying EPF from erosion. We here propose that the EPF was formed by a combination of initial subaerial ignimbrite-forming eruptions, followed by caldera subsidence. The upper volcaniclastic successions in our model represent intra-caldera pumiceous volcaniclastic deposits accumulated in a shallow marine environment in the resultant caldera. The present day elevated position of the succession is a result of a combination of possible caldera resurgence and ongoing arc-related uplift in the region.

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Basalts from the Efate Island Group, central section of the Vanuatu arc, SW Pacific: geochemistry and petrogenesis

Cited by 36 publications

References 38 publications

Primitive shoshonites from Fiji: Geochemistry and source components

Primitive shoshonites from Fiji: Geochemistry and source components

Continental crust generated in oceanic arcs

Is Efate (Vanuatu, SW Pacific) a result of subaerial or submarine eruption? An alternative model for the 1 Ma Efate Pumice Formation

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