Oxygen Isotope Geochemistry of Oceanic-Arc Lavas

Variations of oxygen isotope ratios in arc-related lavas can constrain the contributions of subducted crustal igneous rocks, sediments, and fluids to the sub-arc mantle. We have measured oxygen isotope ratios in 72 arc and back-arc lavas from five ocean–ocean subduction zone systems using laser-fluorination analyses of olivine and other phenocrysts and glass. Eighty percent of our samples have {delta}18O values for any given phase (olivine, plagioclase, glass, or biotite) within 0·2{per thousand} of the average value for that phase in upper-mantle peridotites and mid-ocean ridge basalt (MORB); the range for each phase is <=1·0{per thousand}. This result contrasts with previous studies of whole-rock samples (which are significantly more variable even after exclusion of samples believed to be altered or fractionated by magmatic differentiation) and demonstrates that most arc-related lavas contain <=1–2% of 18O-enriched crustal oxygen from any source (i.e. assimilation or subducted contributions). Elevations in {delta}18O that do occur in these basic, arc-derived magmas relative to values most common for mantle-derived lavas are associated both with ‘enriched’ radiogenic isotope signatures and, even more strongly, with chemical indices consistent with high integrated extents of melting of their peridotite sources. We interpret these relationships as evidence that melting in the sources of the high-{delta}18O lavas we have studied was fluxed by addition of high-{delta}18O aqueous fluid (or perhaps a hydrous melt) from the subducted slab, such that sources that contain relatively large components of slab-derived fluid or melt are both relatively 18O enriched and also experienced relatively large amounts of melting. We have developed a quantitative model linking the amount of melting to the extents of 18O, radiogenic isotope, and trace-element enrichment in a mantle source being fluxed by addition of aqueous fluid. Comparison of this model with observed variations in the geochemistry of lavas from the Vanuatu–Fiji–New Caledonia region (the suite of related samples showing the greatest range in {delta}18O observed in this study) constrains the amounts and chemical and isotopic compositions of slab-derived phases in the sources of these arc-related lavas. Assuming a {delta}18O value of 20{per thousand} for the slab-derived fluid, 0·5–1·0 wt % is added to the sources of most mantle-derived arc magmas; the maximum amount of slab-derived flux in the sources of arc magmas according to our results is 2·5 wt %.

[1]  Marie C. Johnson,et al.  Dehydration and melting experiments constrain the fate of subducted sediments , 2000 .

[2]  E. Nakamura,et al.  Across-arc variation of Li isotopes in lavas and implications for crust/mantle recycling at subduction zones , 1998 .

[3]  G. Gaetani,et al.  The influence of water on melting of mantle peridotite , 1998 .

[4]  D. Mattey,et al.  Oxygen isotope variations in Lau Basin lavas , 1998 .

[5]  J. Eiler.  Oxygen Isotope Geochemistry of Oceanic Arc Lavas , 1998 .

[6]  H. Craig,et al.  Oxygen isotope variations in ocean island basalt phenocrysts , 1997 .

[7]  R. Harmon,et al.  Resolution of the effects of crustal assimilation, sediment subduction, and fluid transport in island arc magmas: PbSrNdO isotope geochemistry of Grenada, Lesser Antilles , 1996 .

[8]  M. Thirlwall,et al.  Trace Element and Isotope Geochemistry of the Volcanic Rocks of Bequia, Grenadine Islands, Lesser Antilles Arc: a Study of Subduction Enrichment and Intra-crustal Contamination , 1996 .

[9]  H. Craig,et al.  Oxygen isotope evidence against bulk recycled sediment in the mantle sources of Pitcairn Island lavas , 1995, Nature.

[10]  R. Harmon,et al.  Oxygen isotope heterogeneity of the mantle deduced from global 18O systematics of basalts from different geotectonic settings , 1995 .

[11]  P. Michael.  Regionally distinctive sources of depleted MORB: Evidence from trace elements and H2O , 1995 .

[12]  A. Hofmann,et al.  Hydrous, silica-rich melts in the sub-arc mantle and their relationship with erupted arc lavas , 1995, Nature.

[13]  D. McKenzie,et al.  The Source Regions of Ocean Island Basalts , 1995 .

[14]  Brian M. Smith,et al.  Large scale isotopic Sr, Nd and O isotopic anatomy of altered oceanic crust: DSDP/ODP sites417/418 , 1995 .

[15]  M. Ghiorso,et al.  New software models thermodynamics of magmatic systems , 1994 .

[16]  N. Rogers,et al.  Potassium and incompatible-element enrichment in shoshonitic lavas from the Tavua volcano, Fiji , 1994 .

[17]  D. Lowry,et al.  Oxygen isotope composition of mantle peridotite , 1994 .

[18]  T. Green.  Experimental studies of trace-element partitioning applicable to igneous petrogenesis , 1994 .

[19]  C. Stern,et al.  Subduction zone melting of pelagic sediments constrained by melting experiments , 1994, Nature.

[20]  A. Crawford,et al.  High-Mg andesites from the southern termination of the New Hebrides island arc (SW Pacific) , 1993 .

[21]  S. Eggins.  Origin and differentiation of picritic arc magmas, Ambae (Aoba), Vanuatu , 1993 .

[22]  C. Langmuir,et al.  Tracing trace elements from sediment input to volcanic output at subduction zones , 1993, Nature.

[23]  G. Wasserburg,et al.  An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules: equilibrium values and kinetic effects , 1993 .

[24]  S. Eggins,et al.  High field strength and transition element systematics in island arc and back-arc basin basalts: Evidence for multi-phase melt extraction and a depleted mantle wedge , 1993 .

[25]  S. Hart,et al.  Experimental cpx/melt partitioning of 24 trace elements , 1993 .

[26]  J. Brophy,et al.  Oxygen isotope constraints on the petrogenesis of Aleutian arc magmas , 1992 .

[27]  A. Crawford,et al.  Primitive island arc and oceanic lavas from the hunter ridge-hunter fracture zone. Evidence from glass, olivine and spinel compositions , 1992 .

[28]  M. Drummond,et al.  Derivation of some modern arc magmas by melting of young subducted lithosphere , 1990, Nature.

[29]  P. Kelemen,et al.  High-field-strength element depletions in arc basalts due to mantle–magma interaction , 1990, Nature.

[30]  F. Tera,et al.  10Be and 9Be in mineral separates and whole rocks from volcanic arcs: Implications for sediment subduction , 1989 .

[31]  R. Stern,et al.  Shoshonitic volcanism in the Northern Mariana Arc: 2. Large‐ion lithophile and rare earth element abundances: Evidence for the source of incompatible element enrichments in intraoceanic arcs , 1989 .

[32]  Michael O. Garcia,et al.  MAJOR ELEMENT, VOLATILE, AND STABLE ISOTOPE GEOCHEMISTRY , 1989 .

[33]  W. McDonough,et al.  Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes , 1989, Geological Society, London, Special Publications.

[34]  F. Albarède,et al.  Hydrothermal Alteration of the Oceanic Crust , 1989 .

[35]  W. Hildreth,et al.  Crustal contributions to arc magmatism in the Andes of Central Chile , 1988 .

[36]  C. Hawkesworth,et al.  Elemental and isotopic variations in subduction related basalts: evidence for a three component model , 1988 .

[37]  C. Langmuir,et al.  Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness , 1987 .

[38]  E. Ito,et al.  The O, Sr, Nd and Pb isotope geochemistry of MORB , 1987 .

[39]  H. Taylor,et al.  Igneous rocks; I, Processes of isotopic fractionation and isotope systematics , 1986 .

[40]  M. Monzier,et al.  Petrology of Matthew and Hunter volcanoes, south New Hebrides island arc (southwest Pacific) , 1986 .

[41]  N. Fujii,et al.  Connectivity of melt phase in a partially molten peridotite , 1986 .

[42]  Mark E. Schneider,et al.  Fluids in equilibrium with peridotite minerals: Implications for mantle metasomatism , 1986 .

[43]  K. Muehlenbachs.  Alteration of the oceanic crust and the 18 O history of seawater , 1986 .

[44]  H. Taylor,et al.  Stable isotopes in high temperature geological processes , 1986 .

[45]  E. Ito,et al.  Oxygen- and strontium-isotopic investigations of subduction zone volcanism: the case of the Volcano Arc and the Marianas Island Arc , 1986 .

[46]  J. Hawkins,et al.  Petrology of Mariana Trough and Lau Basin basalts , 1985 .

[47]  H. Dick,et al.  Chromian spinel as a petrogenetic indicator in abyssal and alpine-type peridotites and spatially associated lavas , 1984 .

[48]  J. R. O'neil,et al.  Genetic relations among basic lavas and ultramafic nodules: Evidence from oxygen isotope compositions , 1982 .

[49]  J. Gill.  Orogenic Andesites and Plate Tectonics , 1981 .

[50]  J. R. O'neil,et al.  Oxygen isotope thermometry of basic lavas and mantle nodules , 1981 .

[51]  R. Kay.  Volcanic Arc Magmas: Implications of a Melting-Mixing Model for Element Recycling in the Crust-Upper Mantle System , 1980, The Journal of Geology.

[52]  A. R. Cooper,et al.  Oxygen diffusion in forsterite , 1980 .

[53]  P. Hamilton,et al.  A geochemical study of island-arc and back-arc tholeiites from the Scotia Sea , 1977 .

[54]  S. Hoernes,et al.  Oxygen Isotope Investigations of Rocks of Leg 37 , 1977 .

[55]  S. Epstein,et al.  Stable isotope geochemistry of deep sea cherts , 1976 .

[56]  H. Craig,et al.  Oxygen isotope variations in marginal basin and ocean-ridge basalts , 1976 .

[57]  R. Arculus,et al.  Rare earth element concentrations in a suite of basanitoids and alkali olivine basalts from Grenada, Lesser Antilles , 1975 .

[58]  I. Kushiro.  On the nature of silicate melt and its significance in magma genesis; regularities in the shift of the liquidus boundaries involving olivine, pyroxene, and silica minerals , 1975 .

[59]  M. A. Lauffer.  The Role of Water , 1975 .

[60]  R. Clayton,et al.  Oxygen Isotope Abundances in Apollo 14 and 15 Rocks and Minerals , 1972 .

[61]  H. Taylor,et al.  The oxygen isotope and cation exchange chemistry of feldspars , 1967 .