Petrology and geochemistry of back-arc basin basalts from Lau Basin spreading ridges at 15�, 18� and 19�S

Falloon, Trevor J.; Malahoff, Alexander; Zonenshaina, L. P.; Bogdanova, Y.

doi:10.1007/bf01165295

Cited by 96 publications

(68 citation statements)

References 46 publications

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“…In the mineralogical, major element, and trace element plots presented in this chapter, the following data sources are used: Bauer (1970), Baker et al (1971), Oversby and Ewart (1972), Ewart et al (1973Ewart et al ( , 1977, Ewart (1976), Gill (1976), Hawkins (1976), Johnstone (1978), Kay and Hubbard (1978), Hawke (1983), Cole et al (1985Cole et al ( , 1990, Hawkins and Melchior (1985), Valuer et al (1985Valuer et al ( , 1991, Ewart and Hawkesworth (1987), Falloon et al (1987Falloon et al ( , 1989Falloon et al ( , 1992, Jenner et al (1987), Frenzel et al (1990), Boespflug et al (1990), Loock et al (1990), Sunkel (1990), Falloon and Crawford (1991), and Ernewein et al (in press). Additional unpublished Kermadec data were made available by Dr. J.A.…”

Section: Methods and Techniquesmentioning

confidence: 99%

“…The first four of these divisions follow from the imagery results of Parson et al (1990), together with the inferred history of development of these ridges as southward-moving propagators (Parson and Hawkins, this volume), an interpretation with considerable geochemical implications. The KTJ (Falloon et al, 1992) is inferred to represent three intersecting spreading centers and a transform fault (Parson et al, 1990), situated in the northeastern Lau Basin. As far as possible, only data from these ridge systems are included, with seamounts being specifically excluded from this compilation.…”

Section: Methods and Techniquesmentioning

confidence: 99%

“…Lee Vallier et al, 1991);Sonne in 1984/85 and again in 1987(e.g., von Stackelberg and Shipboard Scientific Party, 1985, 1988Sunkel, 1990;Frenzel et al, 1990); Charles Darwin (e.g., Parson et al, 1990;Collier and Sinha, 1990); Natsushima (Falloon and Crawford, 1991;Falloon et al, 1987); and Akademik Mstislav Keldysh (Falloon et al, 1992). The results accumulated by these cruises now allow the compilation of a good data base of petrological, geochemical, morphological, and geophysical data on which to develop models based on the recognition of patterns of geochemical behavior, interrelated temporally and geographically to the progressive opening of the Lau Basin.…”

Section: Introductionmentioning

confidence: 99%

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Regional Geochemistry of the Lau-Tonga Arc and Backarc Systems

Ewart¹,

Bryan²,

Chappell³

et al. 1994

Proceedings of the Ocean Drilling Program

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Detailed comparison of mineralogy, and major and trace geochemistry are presented for the modern Lau Basin spreading centers, the Sites 834-839 lavas, the modern Tonga-Kermadec arc volcanics, the northern Tongan boninites, and the Lau Ridge volcanics. The data clearly confirm the variations from near normal mid-ocean-ridge basalt (N-MORB) chemistries (e.g., Site 834, Central Lau Spreading Center) to strongly arc-like (e.g., Site 839, Valu Fa), the latter closely comparable to the modern arc volcanoes. Sites 835 and 836 and the East Lau Spreading Center represent transitional chemistries. Bulk compositions range from andesitic to basaltic, but lavas from Sites 834 and 836 and the Central Lau Spreading Center extend toward more silica-undersaturated compositions. The Valu Fa and modern Tonga-Kermadec arc lavas, in contrast, are dominated by basaltic andesites. The phenocryst and groundmass mineralogies show the strong arc-like affinities of the Site 839 lavas, which are also characterized by the existence of very magnesian olivines (up to Fo 90 _9 2 ) and Cr-rich spinels in Units 3 and 6, and highly anorthitic plagioclases in Units 2 and 9.The regional patterns of mineralogical and geochemical variations are interpreted in terms of two competing processes affecting the inferred magma sources: (1) mantle depletion processes, caused by previous melt extractions linked to backarc magmatism, and (2) enrichment in large-ion-lithophüe elements, caused by a subduction contribution. Ageneral trend of increasing depletion is inferred both eastward across the Lau Basin toward the modern arc, and northward along the Tongan (and Kermadec) Arc. Numerical modeling suggests that multistage magma extraction can explain the low abundances (relative to N-MORB) of elements such as Nb, Ta, and Ti, known to be characteristic of island arc magmas. It is further suggested that a subduction jump following prolonged slab rollback could account for the initiation of the Lau Basin opening, plausibly allowing a later influx of new mantle, as required by the recognition of a two-stage opening of the Lau Basin.

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Section: Methods and Techniquesmentioning

confidence: 99%

Section: Methods and Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Regional Geochemistry of the Lau-Tonga Arc and Backarc Systems

Ewart¹,

Bryan²,

Chappell³

et al. 1994

Proceedings of the Ocean Drilling Program

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“…These new ®ndings provided an explanation for a similarity of rock types (i.e., lavas, dykes and intrusives within boninite-arc tholeiite compositional spectrum, and peridotites) found in modern forearcs and SSZ ophiolites (e.g., Bloomer and Hawkins 1983;Sharaskin et al 1983), and it has been proposed that these forearcs are the best modern analogs for SSZ ophiolites (e.g., Bloomer et al 1995). However, the association of variably evolved tholeiites with strong``arc'' a nities and more primitive boninite and boninite-like lavas has also been described at presently active spreading centres propagating towards the Tonga arc in the southern and northern parts of the Lau Backarc Basin (southern tip of the Valu Fa Ridge; Frenzel et al 1990;Vallier et al 1991;King's Triple Junction: Falloon and Crawford 1991;Falloon et al 1992).…”

Section: Introductionmentioning

confidence: 99%

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

Portnyagin

Danyushevsky²,

Kamenetsky³

1997

Contributions to Mineralogy and Petrology

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We present a detailed mineralogical, petrological and melt inclusion study of unusually fresh, primitive olivine + clinopyroxene phyric Lower Pillow Lavas (LPL) found near Analiondas village in the northeastern part of the Troodos ophiolite (Cyprus). Olivine phenocrysts in these primitive LPL show a wide compositional range (Fo 82±92 ) and have higher CaO contents than those from the Upper Pillow Lavas (UPL). Cr-spinel inclusions in olivine are signi®cantly less Cr-rich (Cr/Cr + Al = 28±67 mol%) compared to those from the UPL (Cr# = 70±80). These features reect di erences in melt compositions between primitive LPL and the UPL, namely higher CaO and Al 2 O 3 and lower FeO* compared to the UPL at a given MgO. LPL parental melts (in equilibrium with Fo 92 ) had $10.5 wt% MgO and crystallization temperatures $1210°C, which are signi®cantly lower than those previously published for the UPL (14±15 wt% MgO and $1300°C for Fo 92 ). The fractionation path of LPL parental melts is also di erent from that of the UPL. It is characterized initially by olivine + clinopyroxene cotectic crystallization joined by plagioclase at $9 wt% MgO, whereas UPL parental melts experienced a substantial interval of olivine-only crystallization. Primitive LPL melts were formed from a mantle source which was more fertile than that of tholeiites from well-developed intra-oceanic arcs, but broadly similar in its fertility to that of MidOcean Ridge Basalt (MORB) and Back Arc Basin Basalts (BABB). The higher degrees of melting during formation of the LPL primary melts compared to average MORB were caused by the presence of subduction-related components (H 2 O). Our new data on the LPL coupled with existing data for the UPL support the existing idea that the LPL and UPL primary melts originated from distinct mantle sources, which cannot be related by progressive source depletion. Temperature di erences between these sources ($150°C), their position in the mantle ($10 kbar for the colder LPL source vs 15±18 kbar for the UPL source), and temporal succession of Troodos volcanism, all cannot be reconciled in the framework of existing models of mantle wedge processes, thermal structure and evolution, if a single mantle source is invoked. Possible tectonic settings for the origin of the Troodos ophiolite (forearc regions of intra-oceanic island arc, propagation of backarc spreading into arc lithosphere) are discussed.

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“…Another alternative explanation introduced by Smellie & Stone (2001) might be provided by the variety of lava types erupted during off-axis magmatism and the propagation of a spreading ridge into arc and back-arc crust (e.g. Falloon et al 1992). Overall, and in view of the lithological complexity at Ballantrae, it is conceivable that many (perhaps all) of the proposed conditions pertained at different times.…”

Section: Arcs Back-arcs and Ocean Islandsmentioning

confidence: 99%

A review of geological origins and relationships in the Ballantrae Complex, SW Scotland

Stone

2014

SJG

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SynopsisA substantial history of research has established the Ballantrae Complex as an ophiolite assemblage, generated within the Iapetus Ocean and accreted at the margin of Laurentia as that ocean began to close. Radiometric dates and graptolite biostratigraphy provide an age range from Neoproterozoic (rarely and questionably) to early Ordovician (commonly and securely). Components of the complex formed in a range of oceanic environments: within-plate oceanic islands, island arcs and backarc spreading zones. Overall, the various lines of evidence point to an early Arenig marginal basin, incorporating some older elements, which was tectonically disrupted and compressed during an obduction event driven by arc-continent collision. Despite the general consensus as to the age and origin of the complex there remain areas of uncertainty. It is highly probable that some components of the complex that are now structurally juxtaposed originated at a considerable distance from each other both horizontally and vertically. Further, the sporadic presence of high-grade metamorphic rocks -notably blueschists -suggests a complicated and probably polyphase structural history, whilst the relative importance of serpentinite diapirism versus compressional and strike-slip tectonics remains unresolved.

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Petrology and geochemistry of back-arc basin basalts from Lau Basin spreading ridges at 15�, 18� and 19�S

Cited by 96 publications

References 46 publications

Regional Geochemistry of the Lau-Tonga Arc and Backarc Systems

Regional Geochemistry of the Lau-Tonga Arc and Backarc Systems

Coexistence of two distinct mantle sources during formation of ophiolites: a case study of primitive pillow-lavas from the lowest part of the volcanic section of the Troodos Ophiolite, Cyprus

A review of geological origins and relationships in the Ballantrae Complex, SW Scotland

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