DOCSLIB.ORG

Oxygen Isotope Variations in Lau Basin Lavas

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Oxygen Isotope Variations in Lau Basin Lavas Chemical Geology 144Ž. 1998 177±194 Oxygen isotope variations in Lau Basin lavas Colin G. Macpherson ), David P. Mattey Department of Geology, Royal Holloway UniÕersity of London, Egham, Surrey TW20 0EX, UK Abstract New laser-fluorination oxygen isotope data are presented for volcanic glasses and phenocrysts from Lau and North Fiji Basin lavas. The low oxygen blank of the technique allows accurate analysis of these often scarce igneous phases. d 18O values of volcanic glass range from 5.53½ to 6.06½. Oxygen isotope ratios of ferromagnesian and plagioclase phenocrysts are lower and higher than their host glasses, respectively, and coexisting phases appear to represent oxygen isotope equilibrium at magmatic temperatures. Evolved lavas from the propagating and dying rift tips in the Central Lau Basin display significant 18O-enrichment with magmatic evolution due to FeTi-oxide crystallisation and require that precursor melts had relatively low d 18O values immediately prior to oxide saturation. Development of these precursor melts from basaltic parents involved assimilation of hydrothermally altered sheeted dykes or gabbros in recently accreted oceanic crust accompanied by crystallisation of a plagioclase-rich assemblage. The stable isotope geochemistry and petrology of Central Lau Basin lavas constrain magmatic evolution to depths between 2.5 and 5 km beneath the seafloor. A dacite from Valu Fa Ridge is slightly 18O-enriched relative to Valu Fa basalts, consistent with crystallisation of a mineral assemblage similar to mid-ocean ridge basalts. 18Or 16O ratios of Lau Basin basaltic glasses decrease with Mg Number; this observation could be reconciled with the assimilation and fractional crystallisation model proposed for initial differentiation of the evolved lavas. However, oxygen isotope data for Central Lau Basin basalts correlate positively with BarLa while basaltic glasses from 18 throughout the region display a negative correlation between d O and Na8.0 suggesting that recycling of subducted oxygen andror mantle fertility may also exert an influence on 18Or 16O of primary melts. Presently, the lack of quantitative control over oxygen isotope fractionation in basaltic systems prohibits resolution of these effects. Detailed investigation of less complex suites of lavas, employing the precision offered by laser fluorination, may provide new insights into the behaviour of oxygen at magmatic temperatures. q 1998 Elsevier Science B.V. Keywords: Lau Basin; Oxygen isotopes; Magmatism; Subduction; Melting; Assimilation 1. Introduction Unaltered lavas erupted at mid-ocean spreading centres display limited18 Or 16O variationŽ 5.7" 0.3½; Ito et al., 1987. This is thought to result from ) Corresponding author. Present address: Geosciences Research melting of an upper mantle reservoir that is uniform Division ± 0220, Scripps Institution of Oceanography, 9500 with respect to oxygen isotopes, followed by limited Gilman Drive, La Jolla, CA 92093-0220, USA. Tel.: q1Ž. 619 534-3260; fax: q 1Ž. 619 534-0784; e-mail: degrees of chemical evolution in sub-ridge magma [email protected] chambersŽ Muehlenbachs and Clayton, 1972; Taylor 0009-2541r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. PII S0009-2541Ž. 97 00130-7 178 C.G. Macpherson, D.P. MatteyrChemical Geology 144() 1998 177±194 and Sheppard, 1986, and references therein. Pro- oxygen from various reservoirs into primary Lau tracted fractional crystallisation can produce oxygen Basin melts. isotope variations in cogenetic lava suites but this is rare at mid-ocean spreading centres, having been recognised only at the 958W propagating rift tip of 2. Samples and technique the Galapagos Spreading CentreŽ Muehlenbachs and Byerly, 1982; Ito et al., 1987. Oxygen isotope ratios The Lau Basin is a triangular-shaped back-arc are frequently employed in petrogenetic studies of basin situated west of the Tonga RidgeŽ. Fig. 1a , subduction zone magmatism to discriminate between where the Pacific Plate is being subducted beneath source and crustal contamination of the magmatic the Australian Plate at the Tonga TrenchŽ Karig, systemŽ. James, 1981 . While the effects of both 1970. The triangular shape results from rapid, crystallisation and open system behaviour have been clockwise rotation of the Tonga Ridge relative to the observed in some tholeiitic lava series, the magni- remnant Lau Ridge, and the southward propagation tude of variations that may be produced by these of two phases of ocean spreadingŽ Parson and processes are small: F0.5½Ž e.g. Taylor, 1968; Hawkins, 1994; Bevis et al., 1995. At around 5.5 Anderson et al., 1971; Matsuhisa et al., 1973; Shep- Ma the first phase of spreading was initiated, south- pard and Harris, 1985; Woodhead et al., 1987; Ellam east of what is now Peggy Ridge, producing oceanic and Harmon, 1990. Furthermore, identification of crust at the Eastern Lau Spreading CentreŽ. ELSC original magmatic 18 Or 16 O variation in submarine and the Valu Fa RidgeŽ. Fig. 1a . These spreading lavas is often obscured by the effects of post-erup- centres propagated southwards through extended arc tive alterationŽ Muehlenbachs and Clayton, 1972; crust between the Tonga and Lau ridges. Then, Pineau et al., 1976; Taylor and Sheppard, 1986. around 1.5 Ma, the Central Lau Spreading Centre Phenocrysts or fresh volcanic glass can be analysed Ž.CLSC began to propagate through crust formed at to avoid alteration products but these phases are the ELSCŽ. Fig. 1a . commonly too scarce in seafloor dredge hauls to Parson et al.Ž. 1990 identified three active spread- allow conventional oxygen isotope analysis of entire ing segments in the Central Lau Basin, representing suites of lavas. propagating and dying rifts with an intermediate This study presents oxygen isotope data obtained `relay' sectionŽ. Fig. 1b . The crests of these ridges by laser-fluorinationŽ. LF for fresh lavas collected were dredged by Cruise 33 of the R.V. Charles from three sites of active volcanism in the Lau Darwin Ž.Pearce et al., 1994 . Eruptive products from Basin. Laser ablation of bulk samples vastly reduces the ELSC and Intermediate Lau Spreading Centre oxygen blanks compared to the classic `bomb' fluo- Ž.ILSC are dominantly basaltic with Mg No.)50, rination method and thus allows routine determina- although glasses from the northern ELSCŽ. site 20 tion of18 Or 16O ratios in igneous phasesŽ Sharp, are more evolvedŽ. Table 1 . Ferrobasalts and an- 1990; Mattey and Macpherson, 1993. Furthermore, desites erupted at the propagating rift tip of the highly refractory phases can be analysed with high CLSC display evidence of extreme chemical frac- precision. Intensive sampling of a propagating rift tip tionation and volatile degassing, compared to other and associated dying rift in the Central Lau Basin Central Lau Basin lavas and mid-ocean ridge basalt has allowed examination of oxygen isotope systemat- ŽMORB; Pearce et al., 1994; Macpherson and Mat- ics through a diverse compositional spectrum of tey, 1994; Farley and Newman, 1994. Plagioclase lavas generated in an oceanic setting. In an effort to dominated the crystallising assemblage in melts with detect subduction-related spatial controls on the 4 wt.%-MgO-7.5 wt.% subduing Sr enrichment 18 Or 16 O ratios of lavas, oxygen isotope data are and producing negative Eu anomalies during differ- also reported for lavas from the northern and south- entiation. Strong FeO, TiO2 and V depletions in ern extremities of the basin. These results are com- evolved lavas are the result of FeTi-oxide crystallisa- pared with other geochemical properties of the lavas tionŽ. Pearce et al., 1994 . Elevated concentrations of and conventionally obtained 18 Or 16 O data from incompatible alkali and alkali earth elements and nearby localities in an effort to constrain the flux of greater vesicularity in ELSC lavas, relative to MORB, C.G. Macpherson, D.P. MatteyrChemical Geology 144() 1998 177±194 179 Fig. 1.Ž. a Map of the Lau Basin and Eastern part of the North Fiji Basin modified from Parson et al.Ž. 1994 . A heavy box outlines the propagating rift system of the Central Lau Basin shown inŽ. b , and the dashed line marks the approximate extent of oceanic crust formed at the Valu Fa Ridge and East Lau Spreading CentreŽ. ELSC . KK16 was recovered approximately 300 km west of Fiji. SO indicates the location of the Valu Fa samples for which detailed localities are presented by Frenzel et al.Ž.Ž. 1990 . b Geometry of the Central Lau Basin neovolcanic zonesŽ. stippled identified by Parson et al. Ž. 1990 , and dredge sites from Cruise 33 of the R.V. Charles Darwin. CLSCsCentral Lau Spreading Centre; ILSCsIntermediate Lau Spreading Centre; ELSCsEastern Lau Spreading Centre. The CLSC is propagating south at the expense of the ELSC. The ILSC is a `relay' zoneŽ. Parson et al., 1990 . 180 C.G. Macpherson, D.P. MatteyrChemical Geology 144() 1998 177±194 may reflect a greater flux of subducted material followed by oxide saturationŽ. Frenzel et al., 1990 . being recycling close to the arcŽ. Pearce et al., 1994 . Magma chambers have been seismically imaged, at The southern end of the Valu Fa Ridge marks the 1±4 km depth, along the entire length of the spread- limit of ocean spreading in the Lau BasinŽ Parson ing segment from which these samples were col- and Hawkins, 1994. Collection sites and petrology lectedŽ. Collier and Sinha, 1992 . Radiogenic isotope of the three glasses analysed from this ridge are and trace element ratios suggest that a small but described by Frenzel et al.Ž. 1990 . Major element significant slab flux is present in Valu Fa lavas concentrations of the basaltic andesites are similar to ŽJenner et al., 1987; Sunkel, 1990; Loock et al., MORB and the daciteŽ. SO35-77KD2 was produced 1990.Ž. ; however, Hilton et al. 1993 showed that He by `normal basaltic differentiation' of basic melts isotopic variations are decoupled from Sr, Nd and Pb isotopes as a result of combined degassing and as- similation.
Load more

Recommended publications
  • Article Is Available Online Initiation, Earth Planet
    Solid Earth, 9, 713–733, 2018 https://doi.org/10.5194/se-9-713-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Boninite and boninite-series volcanics in northern Zambales ophiolite: doubly vergent subduction initiation along Philippine Sea plate margins Americus Perez1, Susumu Umino1, Graciano P. Yumul Jr.2, and Osamu Ishizuka3,4 1Division of Natural System, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan 2Apex Mining Company Inc., Ortigas Center, Pasig City, 1605, Philippines 3Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST, Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan 4Research and Development Center for Ocean Drilling Science, JAMSTEC, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan Correspondence: Americus Perez ([email protected], [email protected]) Received: 25 December 2017 – Discussion started: 31 January 2018 Revised: 7 May 2018 – Accepted: 12 May 2018 – Published: 5 June 2018 Abstract. A key component of subduction initiation rock itudes derived from tilt-corrected sites in the Acoje Block suites is boninite, a high-magnesium andesite that is uniquely place the juvenile arc of northern Zambales ophiolite in the predominant in western Pacific forearc terranes and in select western margin of the Philippine Sea plate. In this scenario, Tethyan ophiolites such as Oman and Troodos. We report, for the origin of Philippine Sea plate boninites (IBM and Zam- the first time, the discovery of low-calcium, high-silica boni- bales) would be in a doubly vergent subduction initiation set- nite in the middle Eocene Zambales ophiolite (Luzon Island, ting.
    [Show full text]
  • EGU2017-16685, 2017 EGU General Assembly 2017 © Author(S) 2017
    Geophysical Research Abstracts Vol. 19, EGU2017-16685, 2017 EGU General Assembly 2017 © Author(s) 2017. CC Attribution 3.0 License. From rifting to spreading - seismic structure of the rifted western Mariana extinct arc and the ParceVela back-arc basin Ingo Grevemeyer (1), Shuichi Kodaira (2), Gou Fujie (2), and Narumi Takahashi (2) (1) GEOMAR Helmholtz Centre of Ocean Research, RD4 - Marine Geodynamics, Kiel, Germany ([email protected]), (2) Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan The proto Izu-Ogasawara (Bonin)-Mariana (IBM) Island arc was created when subduction of the Pacific plate be- gan during the Eocene. Today, the Kyushu-Palau Ridge (KPR) at the centre of the Philippine Sea and the western Mariana Ridge (WMR) are considered to be a remnant of the proto IBM Island arc. The KPR and WMR were separated when back-arc spreading began at 30 to 29 Ma in the Shikoku Basin and ParceVela Basin (PVB). Vol- canic activity along the arcs diminished at 27 Ma and there is little evidence of volcanic activity between 23–17 Ma. Arc volcanism was reactivated at ∼15 Ma, when the opening of the Shikoku Basin and PVB ceased. At about 5 Ma the Mariana Basin opened, rifting the WMR from the Mariana arc. Here, we report results from the seismic refraction and wide-angle profile MR101c shot in summer of 2003 by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) aboard the RV KAIYO during the cruise KY03-06, extending from the PVB across the WMR and terminating just to the east of the WMR.
    [Show full text]
  • 1 Revision #2 2 PETROLOGIC EVOLUTION of BONINITE LAVAS
    This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press. DOI: https://doi.org/10.2138/am-2021-7733. http://www.minsocam.org/ 1 1 2 Revision #2 3 PETROLOGIC EVOLUTION OF BONINITE LAVAS FROM THE IBM FORE-ARC, 4 IODP EXPEDITION 352: EVIDENCE FOR OPEN-SYSTEM PROCESSES DURING 5 EARLY SUBDUCTION ZONE MAGMATISM 6 Jesse L. Scholppa, Jeffrey G. Ryana, John W. Shervaisb, Ciprian Stremtanc, Martin Rittnerd, 7 Antonio Lunaa, Stephen A. Hilla, Zachary D. Atlasa, Bradford C. Macka 8 a School of Geosciences, University of South Florida, 4202 E. Fowler Avenue, NES 107, Tampa, 9 FL, 33620 USA 10 b Department of Geology, Utah State University, 4505 Old Main Hill, Logan, UT, 84322 USA 11 c Teledyne CETAC Technologies, 14306 Industrial Road, Omaha, NE, 68144 USA 12 d TOFWERK AG, Schorenstrasse 39, 3645 Thun, Switzerland 13 ABSTRACT 14 Boninite samples from several intervals within Hole U1439C, recovered during IODP 15 Expedition 352, show highly variable mineral chemistries that imply complex crystallization 16 histories. Small pyroxene grains show oscillatory zoning with cores and zones ranging from 17 pigeonite to augite. Late crystallizing augite has highly variable Al2O3 contents (1.9-13.7 wt%.) 18 and Ca-Tschermak component contents (3-13 mol%), which reflect disequilibrium conditions. 19 Large, euhedral, low-Ca pyroxene (i.e., enstatite/clinoenstatite) crystals exhibit complex sector 20 and oscillatory zoning patterns. Cr-rich spinel is found as inclusions both in olivine and low-Ca 21 pyroxene.
    [Show full text]
  • Western South Pacific Regional Workshop in Nadi, Fiji, 22 to 25 November 2011
    SPINE .24” 1 1 Ecologically or Biologically Significant Secretariat of the Convention on Biological Diversity 413 rue St-Jacques, Suite 800 Tel +1 514-288-2220 Marine Areas (EBSAs) Montreal, Quebec H2Y 1N9 Fax +1 514-288-6588 Canada [email protected] Special places in the world’s oceans The full report of this workshop is available at www.cbd.int/wsp-ebsa-report For further information on the CBD’s work on ecologically or biologically significant marine areas Western (EBSAs), please see www.cbd.int/ebsa south Pacific Areas described as meeting the EBSA criteria at the CBD Western South Pacific Regional Workshop in Nadi, Fiji, 22 to 25 November 2011 EBSA WSP Cover-F3.indd 1 2014-09-16 2:28 PM Ecologically or Published by the Secretariat of the Convention on Biological Diversity. Biologically Significant ISBN: 92-9225-558-4 Copyright © 2014, Secretariat of the Convention on Biological Diversity. Marine Areas (EBSAs) The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the Convention on Biological Diversity concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of Special places in the world’s oceans its frontiers or boundaries. The views reported in this publication do not necessarily represent those of the Secretariat of the Areas described as meeting the EBSA criteria at the Convention on Biological Diversity. CBD Western South Pacific Regional Workshop in Nadi, This publication may be reproduced for educational or non-profit purposes without special permission from the copyright holders, provided acknowledgement of the source is made.
    [Show full text]
  • Kermadec Arc
    ARTICLE Received 11 Nov 2012 | Accepted 5 Mar 2013 | Published 16 Apr 2013 DOI: 10.1038/ncomms2702 Louisville seamount subduction and its implication on mantle flow beneath the central Tonga–Kermadec arc Christian Timm1, Daniel Bassett2, Ian J. Graham1, Matthew I. Leybourne1,w, Cornel E.J. de Ronde1, Jon Woodhead3, Daniel Layton-Matthews4 & Anthony B. Watts2 Subduction of intraplate seamounts beneath a geochemically depleted mantle wedge pro- vides a seldom opportunity to trace element recycling and mantle flow in subduction zones. Here we present trace element and Sr, Nd and Pb isotopic compositions of lavas from the central Tonga–Kermadec arc, west of the contemporary Louisville–Tonga trench intersection, to provide new insights into the effects of Louisville seamount subduction. Elevated 206Pb/ 204Pb, 208Pb/204Pb, 86Sr/87Sr in lavas from the central Tonga–Kermadec arc front are con- sistent with localized input of subducted alkaline Louisville material (lavas and volcaniclastics) into sub-arc partial melts. Furthermore, absolute Pacific Plate motion models indicate an anticlockwise rotation in the subducted Louisville seamount chain that, combined with esti- mates of the timing of fluid release from the subducting slab, suggests primarily trench-normal mantle flow beneath the central Tonga–Kermadec arc system. 1 Department of Marine Geoscience, GNS Science, PO Box 30-368, Lower Hutt 5040, New Zealand. 2 Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK. 3 School of Earth Sciences, University of Melbourne, Melbourne, Victoria 3010, Australia. 4 Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario, Canada K7L 3N6. w Present address: ALS Geochemistry, 2103 Dollarton Hwy, North Vancouver, British Columbia, Canada.
    [Show full text]
  • The Taupo Rift, New Zealand
    PUBLICATIONS Tectonics RESEARCH ARTICLE Rapid Evolution of Subduction-Related Continental 10.1002/2017TC004715 Intraarc Rifts: The Taupo Rift, New Zealand Key Points: P. Villamor1 , K. R. Berryman1 , S. M. Ellis1, G. Schreurs2 , L. M. Wallace1 , G. S. Leonard1, • The Taupo Rift evolves through 1 1 asymmetric inward migration of R. M. Langridge , and W. F. Ries boundary faults (width narrowing) 1 2 and along-strike propagation GNS Science, Lower Hutt, New Zealand, Institute of Geological Sciences, University of Bern, Bern, Switzerland • Comparison between Taupo Rift and subduction and intraplate rifts suggests that the former evolves Abstract The evolution of the continental intraarc Taupo Rift in the North Island, New Zealand, is rapid, faster in particular during early stages significantly faster than comparative intracontinental rifts such as the African Rifts. Based on our faulting • Shallow voluminous magmatism aids episodic rifting. Evolution reversals data and published geological, geophysical, and borehole data, we show that activity in the ~2 Ma Taupo Rift (from magmatic to tectonic) also has rapidly and asymmetrically narrowed via inward and eastward migration of faulting (at rates of À À occur in subduction rifts approximately 30 km Myr 1 and 15 km Myr 1, respectively) and has propagated southward along its axis ~70 km in 350 kyr. The loci of voluminous volcanic eruptions and active faulting are correlated in time and Supporting Information: space, suggesting that a controlling factor in the rapid rift narrowing is the presence of large shallow • Supporting Information S1 heterogeneities in the crust, such as large rhyolitic magma bodies generated by subduction processes, which weaken the crust and localize deformation.
    [Show full text]
  • The Composition of Back-Arc Basin Lower Crust and Upper Mantle in the Mariana Trough: a First Report
    The Island Arc (1996) 5, 354-372 Research Article The composition of back-arc basin lower crust and upper mantle in the Mariana Trough: A first report ROBERTJ. STERN,' SHERMAN H. BLOOMER,^ FERNANDO TOSHITSUGUYAMAZAKI AND T. MARK HARRISON 'Center for Lithospheric Studies, University of Texas at Dallas, Richardson TX 75083-0688, USA, 2Depa?.tment of Geosciences, Oregon State Universtty, Corvallis OR 97331, USA, 3School of Oceav ad Earth Science and Technology, University of Hawaii, Ho~oluluHI 96822, USA, 4Geological Survey of Japan, Higashi, Tsukuba, Iburalii 305, Jupan, 5Departmeiit of Earth and Space Sciences, University of Califomaia at Los Angeles, CA 90024, USA Abstract The Mariana Trough is an active back-arc basin, with the rift propagating northward ahead of spreading. The northern part of the Trough is now rifting, with extension accommo- dated by combined stretching and igneous intrusion. Deep structural graben are found in a region of low heat flow, and we interpret these to manifest a low-angle normal fault system that defines the extension axis between 19"45' and 21"lO'N. A single dredge haul from the deepest (-5.5 km deep) of these graben recovered a heterogeneous suite of volcanic and plutonic crustal rocks and upper mantle peridotites, providing the first report of the deeper levels of back-arc basin lithosphere. Several lines of evidence indicate that these rocks are similar to typical back-arc basin lithosphere and are not fragments of rifted older arc lithosphere. Hornblende yielded an 40Ar/s9Arage of 1.8i 0.6 Ma, which is interpreted to approximate the time of crust formation.
    [Show full text]
  • Special Issue Feature Oceanography Back-Arc , Volume 1, a Quarterly 20, Number Th Journal of Society
    or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of Th e Oceanography Society. Send all correspondence to: [email protected] or Th eOceanography PO Box 1931, Rockville, USA.Society, MD 20849-1931, or e to: [email protected] Oceanography correspondence all Society. Send of Th approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution articleis has been published in Th SPECIAL ISSUE FEATURE Oceanography Back-Arc Threproduction, Republication, systemmatic research. for this and teaching article copy to use in reserved. e is rights granted All OceanographyPermission Society. by 2007 eCopyright Oceanography Society. journal of Th 20, Number 1, a quarterly , Volume Basins BY FERNANDO MARTINEZ, KYOKO OKINO, YASUHIKO OHARA, ANNA-LOUISE REYSENBACH, AND SHANA K. GOFFREDI Earth’s geology is fashioned to a large degree at lithospheric plate boundaries by the types of relative motion between adjacent plates. At divergent plate boundaries, such as mid- ocean ridges, mafi c basaltic lavas erupt, forming the seafl oor that underlies most of the ocean basins. At convergent boundaries, such as subduction zones, oceanic lithosphere is consumed at deep-sea trenches, leading to the eruption of chains of andesitic arc volcanoes near the edge of the overriding plate. Back-arc basins are especially diverse geologic set- tings because they inherently involve both of these types of plate boundaries. Back-arc basins are extensional basins formed behind subduction zones by rifting vol- canic arcs and accreting new volcanic seafl oor (Karig, 1970).
    [Show full text]
  • Geoprisms Science Goals in the Havre Trough Back-Arc Basin
    GeoPRISMS Science Goals in the Havre Trough Back-Arc Basin Fernando Martinez1 and Robert A Dunn2 1 Hawaii Institute of Geophysics and Planetology; 2 Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822, USA [email protected]; [email protected] The Havre Trough is an ultra-slow opening (~15-20 mm/yr, Ruellan et al., 2003) back-arc basin undergoing active extension in a broad zone proximal to the arc volcanic front. This appears to be a distinct style of seafloor spreading specific to back-arc basins. We suggest that it facilitates the study of intrinsic melt generation and chemical patterns in the mantle wedge by minimizing 2-D plate-driven advection components while sampling mantle wedge melts over a broad zone. These conditions make the Havre Trough well suited to address GeoPRISMS science objectives: How do volatile release and transfer affect the rheology and dynamics of the plate interface, from the incoming plate and trench through to the arc and back-arc? At mid-ocean ridges the extraction of water from the mantle by melting has been proposed to greatly strengthen the residual mantle leading to the formation of a strong anhydrous “compositional” lithosphere [Hirth and Kohlstedt, 1996; Phipps Morgan, 1997] and perhaps helps focus deformation and volcanism to narrow plate boundary zones [Macdonald, 1982]. At back-arc basins, mantle water content increases by over an order of magnitude as the volcanic arc is approached [Kelley et al., 2006] resulting in a several orders of magnitude weakening of mantle material [Hirth and Kohlstedt, 2003].
    [Show full text]
  • The Fiji Region Includes Three Back-Arc/Marginal Basins Known As South Fiji Basin, Lau Basin, and North Fiji Basin (Fig
    J. Phys. Earth, 34, 407-426, 1986 UPPER MANTLE VELOCITY OF FIJI REGION FROM SURFACE WAVE DISPERSION Kandiah SUNDARALINGAM Department of Physics, The University of the South Pacific, Suva, Fiji (Received May 12, 1986; Revised October 17, 1986) Single station group velocities over the period range 15-100 s are computed for nine fundamental mode Rayleigh wave propagation paths that cross tectonic provinces of the Fiji region. These computations are based on recordings of the earthquakes around the Fiji Islands by the WWSSN (World Wide Standard Seismic Network) stations AFI (Afiamalu), HNR (Honiara), and WEL (Wellington). The inversion of the derived dispersion curves for shear velocity-depth structure shows that uppermost mantle velocity beneath South Fiji basin, Lau basin, and North Fiji basin is slightly lower than that derived for the Pacific ocean region of similar age by Yu and MITCHELL(1979). The uppermost mantle lid is almost absent beneath these marginal basins, and the shear velocity is between 4.0-4.3 km/s in the depth range from Moho down to 220 km. 1. Introduction The Fiji region includes three back-arc/marginal basins known as South Fiji basin, Lau basin, and North Fiji basin (Fig. 1). The South Fiji basin is one of a series of marginal basins west of the Tonga- Kermadec Island arc-trench system (KARIG, 1970). It lies to the north of New Zealand and is bounded by the Lau-Colville ridge to the east, the Hunter fracture zone to the north and the Loyalty rise and Three Kings rise to the west. The basin is underlain by oceanic crust (SH©Ret al., 1971) and was considered by KARIG(1970) to be formed by crustal extension in Oligocene times, with the Three Kings rise and Loyalty rise being interpreted as remanent arcs.
    [Show full text]
  • Hikurangi Plateau Subduction a Trigger for Vitiaz Arc Splitting and Havre Trough Opening (Southwestern Pacific) K
    https://doi.org/10.1130/G48436.1 Manuscript received 15 May 2020 Revised manuscript received 12 November 2020 Manuscript accepted 15 November 2020 © 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 30 December 2020 Hikurangi Plateau subduction a trigger for Vitiaz arc splitting and Havre Trough opening (southwestern Pacific) K. Hoernle1,2, J. Gill3, C. Timm1,4, F. Hauff1, R. Werner1, D. Garbe-Schönberg2 and M. Gutjahr1 1 GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany 2 Institute of Geosciences, Kiel University, 24118 Kiel, Germany 3 Department of Earth and Planetary Sciences, University of California, Santa Cruz, California 95064, USA 4 GNS Science, PO Box 30-368, Lower Hutt 5040, New Zealand ABSTRACT et al., 2011). It formed at ca. 125 Ma as part Splitting of the Vitiaz arc formed the Tonga-Kermadec and Lau-Colville Ridges (south- of the Ontong Java–Manihiki–Hikurangi super- western Pacific Ocean), separated by the Lau Basin in the north and Havre Trough in the plateau, which broke apart shortly after forma- south. We present new trace element and Sr-Nd-Hf-Pb isotope geochemistry for the Kermadec tion (e.g., Davy et al., 2008; Hoernle et al., and Colville Ridges extending ∼900 km north of New Zealand (36°S–28°S) in order to (1) 2010). The basement of the plateau fragments compare the composition of the arc remnants with Quaternary Kermadec arc volcanism, consists of two distinct geochemical types: (2) constrain spatial geochemical variations in the arc remnants, (3) evaluate the effect of (1) low-Ti basalts (Kroenke and Kwaimbaita Hikurangi igneous plateau subduction on the geochemistry of the older arc lavas, and (4) groups on Ontong Java) have isotopically inter- elucidate what may have caused arc splitting.
    [Show full text]
  • The Northern Lau Basin: Diffuse Backarc Extension at the Leading Edge of the Indo-Australian Plate
    THE NORTHERN LAU BASIN: DIFFUSE BACKARC EXTENSION AT THE LEADING EDGE OF THE INDO-AUSTRALIAN PLATE L.M. Parson' and D.L. Tiffin' August 1992 SOPAC Technical Report 141 1 LM. Parson, Institute OF Oceanographic Sciences Deacon Laboratory, Brook Road, Wormley, Surrey, UK :2 D.L Tiffin, South Pacific Applied Geoscience Commission, Suva, Fiji Prepared for:South Pacific Applied Geoscience Commission (SOPAC) [3J CONTENTS Page ABSTRACT 5 ACKNOWLEDGEMENTS . .. 6 INTRODUCTION . .. 7 BATHYMETRY 9 GEOPHYSICS 10 DATA 11 GLORIA IMAGERY 11 THE GLORIA SURVEY 11 RESULTS 13 The basement ridge AND sedimented Inter-ridge area 16 The Kings Triple Junction AND surrounding area 23 The sedimented BLOCK terrain IN the central northern Lau Basin 26 The Northwest Lau Spreading Centre (NWLSC) 27 • The northern Peggy Ridge 29 DISCUSSiON 29 MINERAL RESOURCE POTENTIAL OF THE NORTHERN LAU BASIN 33 CONCLUSIONS 35 REFERENCES 36 [TR141 • Parson & TlffinJ [4] LIST OF FIGURES Figure Page 1 Location map of lau Basin between Fiji and Tonga 8 2 Outline of the northern lau Basin survey area 12 3 GLORIA mosaic of the northern lau Basin survey area 14 4 Line drawing structural Interpretation of Figure 3 15 5 Bathymetry of the northeastern Lau Basin area of study 17 6 A section of seismic reflection profile 18 7 A section of seismic reflection profile 21 8 Preliminary detaJed bathymetry by RV Ke/dysh of a dive area 24 9 A section of seismic reflection profile with line drawing 28 10 Tectonic synthesis of the Lau Basin 31 (TR141 - Parson & Tiffin] [5) ABSTRACT GLORIA sidescan imagery of the Lau Basin north of 1tJS reveals several morphoteetonic terrains: a basement ridge and sedlmented Inter-ridge area in the southeast between 1740W' and 1750SOW, 15°50'$ and 1'fJS; a triple Junction in highly tectonlsed sedlmented terrain In the eastern north Lau Basin; an extensional deeply sedlmented terrain in the central north Lau Basin; a newly discovered linear neovolcanlc zone striking NNE from Peggy Ridge In the northwestern basin; and the northern Peggy Ridge.
    [Show full text]