Rutile saturation in magmas: implications for TiNbTa depletion in island-arc basalts

doi:10.1016/0012-821X(87)90223-8

Earth and Planetary Science Letters

Volume 86, Issues 2–4, December 1987, Pages 225-239

https://doi.org/10.1016/0012-821X(87)90223-8 Get rights and content

Abstract

The TiO₂ contents of rutile-saturated melts ranging from basalt to rhyodacite have been investigated at P = 8–30 kbar and T = 1000–1300°C under hydrous, CO₂-saturated, and volatile-absent conditions. Dissolved TiO₂ is positively correlated with T and not strongly dependent on P_total. For fixed P and T, TiO₂ content decreases markedly as the melts become more felsic. The distribution of TiO₂ between rutile and liquid, expressed as a wt.% concentration ratio, D (rut/liq), is given by: In D = −3.16 + (9373T) + 0.026P − 0.152FM where T is in Kelvins, P in kbar and FM is a melt composition parameter, FM = [Na+K+ 2(Ca+Fe+Mg)]/Al· 1/Si in which the chemical symbols represent cation fractions. The first term expresses the competition of aluminate and titanate anions for charge-compensating cations, and the second term expresses the inverse dependence of dissolved TiO₂ on SiO₂ content. There is no apparent dependence of rutile solubility on water content.

For ranges of probable solidus conditions, rutile saturation in basaltic, andesitic, and dacitic liquids requires 7–9, 5–7, and 1–3 wt.% TiO₂, respectively. These concentrations are well in excess of those found in the respective rock types, so depletion in Nb, Ta, and Ti and reduced Nb/U and Nb/Th ratios in volcanic rocks erupted at convergent plate margins cannot be attributed to residual rutile in their source regions. Thus, Nb, Ta and Ti depletion must be an inherent property of the source region.

We suggest that the island-arc source region has been depleted in Nb and Ta by a previous episode of melt extraction (MORB), zoning refining, or equilibration with a percolating melt or fluid. Such a process markedly depletes the LILE and HFSE element concentrations in the residuum, but ratios such as Nb/U, Nb/Th and U/Th remain relatively constant due to similar solid-melt partition coefficients. The depletion of Nb relative to Th in the source regions of island-arc magmas occurs during hybridization of the source by rutile-saturated (Nb/Ta-depleted) melts or aqueous fluids. If the hybridizing agent is a melt, a relatively felsic composition, produced under low T (900°) hydrous conditions, is required.

References (81)

McCullochM.T. et al.
¹⁴³Nd/¹⁴⁴Nd,⁸⁷Sr/⁸⁶Sr and trace element constraints on the petrogenesis of Aleutian island arc magmas
Earth Planet. Sci. Lett.
(1981)
PearceJ.A. et al.
Tectonic setting of basic volcanics rocks determined using trace element analyses
Earth Planet. Sci. Lett.
(1973)
PerfitM.R. et al.
Chemical characteristics of island-arc basalts: implications for mantle sources
Chem. Geol.
(1980)
NohdaS. et al.
Nd and Sr isotopic study of volcanic rocks from Japan
Earth Planet. Sci. Lett.
(1981)
SunS.S. et al.
Geochemical characteristics of mid-ocean ridge basalts
Earth Planet. Sci. Lett.
(1979)
WoodD.A. et al.
A re-appraisal of the use of trace elements to classify and discriminate between magma series erupted in different tectonic settings
Earth Planet. Sci. Lett.
(1979)
TeraF. et al.
Sediment incorporation in island arc magmas: inferences from¹⁰Be
Geochim. Cosmochim. Acta
(1986)
ArculusR.J.
Island-arc magmatism in relation to the evolution of the crust and mantle
Tectonophysics
(1981)
MorrisJ.D. et al.
Isotopic and incompatible element constraints on the genesis of island arc volcanic from Cold Bay and Amak Island, Aleutians, and implications for mantle structure
Geochim. Cosmochim. Acta
(1983)
HickeyR.L. et al.
Geochemical characteristics of boninite series volcanics: implications for their source
Geochim. Cosmochim. Acta
(1982)

GreenT.H.

Experimental evidence for the role of accessory phases in magma genesis

J. Volcanol. Geotherm. Res.

(1981)

SaundersA.D. et al.

Transverse geochemical variations across the Antarctic Peninsula: implications for the genesis of calc-alkaline magmas

Earth Planet. Sci. Lett.

(1980)

WatsonE.B. et al.

Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types

Earth Planet. Sci. Lett.

(1983)

HansonG.N. et al.

Modeling of major elements in mantle-melt systems using trace element approaches

Geochim. Cosmochim. Acta

(1978)

DickinsonJ.E. et al.

Rutile solubility and titanium coordination in silicate melts

Geochim. Cosmochim. Acta

(1985)

GreenT.H. et al.

Ti-rich accessory phase saturation in hydrous mafic-felsic compositions at high P, T

Chem. Geol.

(1986)

HellmanP.L. et al.

The role of sphene as an accessory phase in high pressure partial melting of hydrous mafic compositions

Earth Planet. Sci. Lett.

(1979)

HofmannA.W. et al.

Nb and Pb in oceanic basalts: new constraints on mantle evolution

Earth Planet. Sci. Lett.

(1986)

AllègreC.J. et al.

Fine chronology of volcanic processes

Earth Planet. Sci. Lett.

(1976)

FreyF.A. et al.

Geochemistry of diverse basalt types from Loihi Seamount, Hawaii: petrogenetic implications

Earth Planet. Sci. Lett.

(1983)

RodenM.F. et al.

Geochemistry of tholeiitic and alkali lavas from the Koolau range, Oahu, Hawaii: implications for Hawaii volcanism

Earth Planet. Sci. Lett.

(1984)

TatsumotoM. et al.

UThPb and RbSr systematics of Allende and UThPb systematics Orgueil

Geochim. Cosmochim. Acta

(1976)

HsuiA.T. et al.

On melting of the subducted ocean crust: effects of subduction induced mantle flow

Tectonophysics

(1983)

SaundersA.D. et al.

The geochemistry of basalts from a back-arc spreading center in the East Scotia Sea

Geochim. Cosmochim. Acta

(1979)

BeccaluvaL. et al.

Petrology and K/Ar ages of volcanics dredged from Eolian seamounts: implications for geodynamic evolution of the southern Tyrrhenian basin

Earth Planet. Sci. Lett.

(1985)

GreenT.H. et al.

Genesis of the calc-alkaline igneous rock suite

Contrib. Mineral. Petrol.

(1968)

MarshB.D. et al.

Benioff zone magmatism

J. Geophys. Res.

(1974)

BrophyJ.G. et al.

On the origin of Hi-Alumina arc basalt and the mechanics of melt extraction

J. Petrol.

(1986)

NichollsI.A. et al.

Effect of olivine stability in tholeiites and the production of silica saturated magmas in the island-arc environment

J. Geol.

(1973)

ArculusR.J. et al.

Island arc magma sources: a geochemical assessment of the roles of slab-derived components and crustal contamination

Geochem. J.

(1981)

RingwoodA.E.

The petrologic evolution of island arc systems

J. Geol. Soc. London

(1974)

ArculusR.J. et al.

Source component mixing in the regions of arc magma generation

J. Geophys. Res.

(1986)

PearceJ.A.

Trace element characteristics of lavas from destructive plate boundaries

DePaoloD.J. et al.

Magma genesis in the New Britain Island arc: constraints from Nd and Sr isotopes and trace element patterns

Contrib. Mineral. Petrol.

(1979)

JagoutzE. et al.

The abundances of major, minor and trace elements in the earth's mantle as derived from primitive ultramafic nodules

WoodD.A. et al.

Elemental and Sr isotope variations in basic lavas from Iceland and the surrounding ocean floor: the nature of mantle source inhomogeneities

Contrib. Mineral. Petrol.

(1979)

Basaltic Volcanism Study Project

Island Arc Basalts

EwartA. et al.

Mineralogy and geochemistry of the younger volcanic islands of Tonga, S.W. Pacific

J. Petrol.

(1973)

DeLongS. et al.

Magmatic evolution of Semisopochnoi Island, Alaska: trace element and isotopic constraints

J. Geol.

(1985)

PearceJ.A. et al.

Petrogenetic implications of Ti, Zr, Y and Nb variations in volcanic rocks

Contrib. Mineral. Petrol.

(1979)

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