Postsubduction ocean island alkali basalts in Fiji

Gill, James B.; Whelan, Peter

doi:10.1029/jb094ib04p04579

Cited by 55 publications

(50 citation statements)

References 30 publications

(2 reference statements)

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“…Development of the Lau Basin behind the Tonga-Kermadec arc since the Miocene illustrates the diversity of rock associations that can form during arc rifting and its evolution to back-arc spreading (Fig. 8) (Gill and Whalen 1989). Submarine, hydrothermal convection systems develop in association with rift-driftrelated intra-arc or back-arc magmatism (e.g., Lau Basin, Fig.…”

Section: Evidence For Intra-arc Extension In the Flin Flon Arc Assembmentioning

confidence: 99%

Contrasting arc and MORB-like assemblages in the Paleoproterozoic Flin Flon Belt, Manitoba, and the role of intra-arc extension in localizing volcanic-hosted massive sulphide deposits

et al. 1999

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The Flin Flon Belt (Trans-Hudson Orogen, Manitoba and Saskatchewan) is the largest Paleoproterozoic volcanic-hosted massive sulphide (VMS) district in the world, with 118.7 million tonnes (Mt) of Zn-Cu-(Au-Ag) sulphide ore in 25 past or presently producing mines and 64.3 Mt in subeconomic deposits. The orebodies are restricted to isotopically juvenile volcanic-arc sequences, dated at 1.903-1.881 Ga at Flin Flon. Sequences of ca. 1.904-1.901 Ga back-arc and ocean-plateau basalts and related plutonic rocks, structurally juxtaposed with the arc assemblages at 1.880-1.870 Ga, are not known to contain economic base metal deposits. The juvenile arc tectonostratigraphic assemblages are generally marked by older and stratigraphically lower tholeiitic submarine volcanic packages (ca. 1.903-1.886 Ga) that are observed or interpreted to be overlain by extensive and lithologically varied sequences of calc-alkaline and alkaline (shoshonitic) arc rocks and arc rift deposits (ca. 1.888-1.881 Ga). VMS deposits occur in both the tholeiitic and calc-alkaline arc sequences, but the 62 Mt Flin Flon deposit occurs in a 1.903 Ga tholeiitic primitive arc package. It can be demonstrated that for the Flin Flon -Callinan -Triple 7, Cuprus, and White Lake VMS deposits, whose stratigraphic context is preserved, deposition of the massive sulphides was temporally associated with inferred arc rifting processes. Critical observations for arc rifting include evidence for extensional faulting, erosion, and development of unconformities; extrusion of MORB-like basalts and associated rhyolites; and development of depositional basins with thick sequences of shoshonitic turbidites. As has been proposed for other major VMS camps (e.g., Kuroko, Kidd Creek, Bathurst), arc rifting can generate the loci of sustained high heat flow and fluid pathways required for the development of long-lived hydrothermal convection systems.Résumé : La Zone de Flin Flon (de l'orogène trans-hudsonien, au Manitoba et en Saskatchewan) représente le plus grand district de sulfures massifs associés à des roches volcaniques dans le monde, avec 118,7 millions de tonnes (Mt) de minerai sulfuré de Zn-Cu-(Au-Ag) dans les 25 gisements actuellement ou antérieurement en production, auxquels on doit ajouter 64,3 MT dans des gîtes à teneur subéconomique. Les corps minéralisés sont restreints aux séquences d'arc volcanique isotopiquement juvéniles qui sont datées de 1,903-1,881 Ga à Flin Flon. On n'a pas réussi à trouver des gîtes de métaux communs à teneur économique dans les séquences d'arrière-arc âgées approximativement de 1,904-1,901 Ga, et ni dans les basaltes de plateau océaniques ou dans les roches plutoniques associées qui sont structuralement juxtaposées aux assemblages d'arc âgés de 1,880-1,870 Ga. Dans les assemblages tectonostratigraphiques d'arc juvénile, apparaissent généralement des lots de roches volcaniques tholéiitiques plus anciennes (environ 1,903-1,886 Ga) d'origine sous-marine à un niveau stratigraphique inférieur; ces lots sont observés ou interprétés comme étant r...

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Section: Evidence For Intra-arc Extension In the Flin Flon Arc Assembmentioning

confidence: 99%

Contrasting arc and MORB-like assemblages in the Paleoproterozoic Flin Flon Belt, Manitoba, and the role of intra-arc extension in localizing volcanic-hosted massive sulphide deposits

et al. 1999

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“…In modern arcs, HFSE-enriched lavas may be found toward the back-arc region, in rifting environments, and where the subducting slab is characterized by an elevated thermal regime (Pearce 1982;Gill and Whelan 1989). The signatures found toward the back-arc region, as in the example of the Cascade arc, may result from melting in the mantle wedge when amphibole, which concentrates HFSE, ceases to be a residual phase (Borg et al 1997).…”

Section: Introductionmentioning

confidence: 96%

“…Alternatively, declining fluid inputs from the slab toward the back-arc region, may allow melting of preexisting low melting point components in the mantle wedge (Leeman et al 1990). Enrichments in HFSE during advanced stages of rifting, as in the Fiji arc (Gill and Whelan 1989), and during the development of slab windows (Hole et al 1991(Hole et al , 1995Johnston and Thorkelson 1997), are imparted from asthenospheric sources. Elevated thermal regimes in arcs are usually associated with the subduction of young oceanic crust, and may result in either early dehydration of the slab allowing tapping of mantle less affected by metasomatism (Harry and Green 1999), or melting of the subducting slab (Defant and Kepezhinskas 2001).…”

Section: Introductionmentioning

confidence: 98%

Geochemical and Nd‐Sr‐Pb isotopic evidence on the origin and geodynamic evolution of mid‐Cretaceous continental arc volcanic rocks of the Spences Bridge Group, south‐central British Columbia

Smith

Thorkelson

2002

Geological Journal

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The mid-Cretaceous Spences Bridge Group (SBG) comprises a series of basaltic to rhyolitic lavas and related volcaniclastic rocks (Pimainus Formation) overlain by a succession of mainly amygdaloidal andesites (Spius Formation) related to the closure of the Methow-Tyaughton basin and accretion of the Insular terrane in the North American Cordillera. Geochemical variation in the SBG is related primarily to metasomatic processes in the mantle wedge. Pimainus lavas include low-to high-K, tholeiitic and calc-alkaline types, and have isotopic compositions (" Nd .43) between the ranges for primitive arcs and accreted terrane crust. Crustal sources are identified only for some low-medium K dacite and rhyolite compositions. The occurrence of intermediate compositions with high MgO contents (up to 6 wt%) and the presence of adakitic trace element features in medium-high K felsic lavas attests to metasomatism of the mantle wedge by slab melts during Pimainus volcanism. Spius lavas have comparable K 2 O and Pb isotopic compositions to the Pimainus, even higher MgO (up to 9.2 wt%), and display a mild intraplate character in having up to 0.6 wt% P 2 O 5 , 15 ppm Nb, and 240 ppm Zr. Spius Nd À Sr isotopic compositions (" Nd (100Ma) ¼ þ 5.3 to þ 6.9, " Sr (100Ma) ¼ À 14 to À 25) define an array extending from Pimainus to alkaline seamount compositions. The low " Sr values, elevated high field strength element contents, and moderate silica contents suggest Spius volcanism was related to the introduction of small melt fractions from the asthenosphere into the mantle wedge which had previously generated Pimainus melts. The range of compositional types in the Pimainus Formation constrains tectonic scenarios to include an elevated slab thermal regime, likely from approach of an ocean ridge system toward the continental margin. Spius volcanism may have been generated by asthenospheric upwelling triggered by slab window development or slab-hinge rollback on closure of the Methow-Tyaughton basin.

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“…Alkaline volcanic provinces similar to those of the Bering Sea region occur in a wide range of tectonic settings. This type of volcanism has been related to mantle plumes (e.g., Chen and Frey, 1985), to regions of postsubduction magmatism (Gill and Whelan, 1989), rifting , and areas undergoing transtensional deformation (Hoang and Flower, 1998). The similar characteristics of alkaline magmas in all of these settings from both continental and oceanic plates (e.g., Fitton, 1987) have led some workers to suggest that these magmas must be derived from beneath the lithosphere-asthenosphere boundary.…”

Section: Introductionmentioning

confidence: 97%

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

Wirth¹,

Grandy²,

Kelley³

et al. 2002

Tectonic Evolution of the Bering Shelf-Chukchi Sea-Artic Margin and Adjacent Landmasses

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Late Cenozoic volcanic centers throughout the Bering Sea region of Alaska consist of small-volume eruptions of ×ows and cones of tholeiitic to alkaline basalt. Peridotite (spinel lherzolite, websterite, wehrlite, and pyroxenite) and gabbro xenoliths are abundant in some of the most alkaline ×ows and cones. Spinel lherzolite xenoliths are characterized by granuloblastic-equant and coarse-equant textures typical of mantle peridotites and yield equilibration temperatures of 1000-1200 °C (1.5 GPa). Relative to other spinel lherzolites worldwide, these xenoliths have low MgO and high Fe 2 O 3 T and are similar to some modeled compositions for fertile mantle. However, these xenoliths are relatively enriched in the light rare earth elements (REE), Th, U, K, Nb, and Ta. Rare amphibole peridotite xenoliths have textures and compositions that are consistent with an origin as pyroxenite veins in the mantle that were variably deformed and metasomatized with potassium-rich ×uids. These xenoliths have concave-up light REE patterns similar to those of the host basalts, suggesting that the alkaline melts may have been produced by melting of amphibole-bearing mantle peridotites. Gabbroic xenoliths are variably deformed and recrystallized at relatively high pressure (0.4-0.6 GPa). Trace element ratios (e.g., Ba/Nb, La/Nb) indicate that these xenoliths crystallized from melts that were produced in a suprasubduction-zone setting and suggest that they represent cumulates that formed in the lower crust during Late Cretaceous subduction. We suggest that these cumulates are the source of the strong re×ec-tions that are observed in seismic re×ection proµle images of the Bering Sea region.Volcanic ×ows consist of tholeiite, olivine tholeiite, alkali-olivine basalt, and basanite, whereas cones consist mostly of alkali-olivine basalt and basanite. Geochemical variations within each volcanic µeld largely re×ect the effects of fractionation and melting (depth and fraction of melting), whereas between-µeld geochemical differences are largely due to source composition differences. The enriched incompatible trace element compositions (light REE, Ba, Th, Nb, Ta) and ratios (Th/Ta, Rb/Zr, Nb/La, La/Yb) are similar to intraplate basalts from ocean island and continental extensional settings. In particular, the compositions of Bering Sea basalts are similar to those of the diffuse volcanic province of Southeast Asia, a region where late Cenozoic volcanism has been related to tectonic extrusion along reactivated strike-slip faults.

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Postsubduction ocean island alkali basalts in Fiji

Cited by 55 publications

References 30 publications

Contrasting arc and MORB-like assemblages in the Paleoproterozoic Flin Flon Belt, Manitoba, and the role of intra-arc extension in localizing volcanic-hosted massive sulphide deposits

Contrasting arc and MORB-like assemblages in the Paleoproterozoic Flin Flon Belt, Manitoba, and the role of intra-arc extension in localizing volcanic-hosted massive sulphide deposits

Geochemical and Nd‐Sr‐Pb isotopic evidence on the origin and geodynamic evolution of mid‐Cretaceous continental arc volcanic rocks of the Spences Bridge Group, south‐central British Columbia

Evolution of crust and mantle beneath the Bering Sea region: Evidence from xenoliths and late Cenozoic basalts

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