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Chemical and isotopic systematics of oceanic basalt : implications for mantle composition and processes

S. S. Sun
01 Jan 1989-Vol. 42, pp 313-345
TL;DR: In this article, trace-element data for mid-ocean ridge basalts and ocean island basalts are used to formulate chemical systematics for oceanic basalts, interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone.
Abstract: Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.
Citations
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Journal Article•DOI•
The composition of the Earth

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William F. McDonough1, Shen-Su Sun1•
Australian National University1
01 Mar 1995-Chemical Geology
TL;DR: In this paper, the authors compared the relative abundances of the refractory elements in carbonaceous, ordinary, and enstatite chondritic meteorites and found that the most consistent composition of the Earth's core is derived from the seismic profile and its interpretation, compared with primitive meteorites, and chemical and petrological models of peridotite-basalt melting relationships.

10,830 citations

Journal Article•DOI•
Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust

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Julian A. Pearce1•
Cardiff University1
01 Jan 2008-Lithos
TL;DR: Two geochemical proxies are particularly important for the identification and classification of oceanic basalts: the Th-Nb proxy for crustal input and hence for demonstrating an oceanic, non-subduction setting; and the Ti-Yb proxy, for melting depth and hence indicating mantle temperature and thickness of the conductive lithosphere as mentioned in this paper.

2,487 citations

Journal Article•DOI•
Major and trace element composition of the depleted MORB mantle (DMM)

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R. Workman1, Stanley R. Hart1•
Woods Hole Oceanographic Institution1
28 Feb 2005-Earth and Planetary Science Letters
TL;DR: Asimow et al. as mentioned in this paper derived an estimate for the chemical composition of the depleted MORB mantle (DMM), the source reservoir to mid-ocean ridge basalts (MORBs), which represents at least 30% the mass of the whole silicate Earth.

2,340 citations

Journal Article•DOI•
Zircon trace element geochemistry: partitioning with garnet and the link between U–Pb ages and metamorphism

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Daniela Rubatto1•
Australian National University1
15 Mar 2002-Chemical Geology
TL;DR: In this article, the trace element distribution coefficients between zircon and garnet were analyzed for trace elements using LA-ICP-MS and SHRIMP ion microprobe.

2,246 citations

Cites methods from "Chemical and isotopic systematics o..."

  • ...Notes to Table 1: r = Rim; c = core; na = not analysed; bd = below detection; Lun/Smn = normalised to chondrite after Sun and McDonough (1989). a Average and standard deviation values for each zircon category are based on a larger number of analyses (see Background Data Set, http:// www....

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  • ...Normalisation after Sun and McDonough (1989). D....

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Journal Article•DOI•
Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa

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R.P Rapp1, Nobumichi Shimizu2, Marc D. Norman3, G.S Applegate4, G.S Applegate1 •
State University of New York System1, Woods Hole Oceanographic Institution2, Macquarie University3, Middlebury College4
02 Sep 1999-Chemical Geology
TL;DR: In this paper, a set of experiments on natural, hydrous basalts at 1-4 GPa constrain the composition of "unadulterated" partial melts of eclogitized oceanic crust within downgoing lithospheric slabs in subduction zones, where these same adakite melts are allowed to infiltrate and react with an overlying layer of peridotite.

1,492 citations

References
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The continental crust: Its composition and evolution

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Stuart Ross Taylor, Scott M. McLennan
01 Jan 1985
TL;DR: In this paper, the authors describe the composition of the present upper crust and deal with possible compositions for the total crust and the inferred composition of lower crust, and the question of the uniformity of crustal composition throughout geological time is discussed.
Abstract: This book describes the composition of the present upper crust, and deals with possible compositions for the total crust and the inferred composition of the lower crust. The question of the uniformity of crustal composition throughout geological time is discussed. It describes the Archean crust and models for crustal evolution in Archean and Post-Archean time. The rate of growth of the crust through time is assessed, and the effects of the extraction of the crust on mantle compositions. The question of early pre-geological crusts on the Earth is discussed and comparisons are given with crusts on the Moon, Mercury, Mars, Venus and the Galilean Satellites.

12,457 citations

Journal Article•DOI•
A large-scale isotope anomaly in the Southern Hemisphere mantle

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Stanley R. Hart1•
Massachusetts Institute of Technology1
28 Jun 1984-Nature
TL;DR: The authors showed that the isotopic mantle anomaly is globe-encircling in extent, centred on latitude 30° S. They also showed that this mantle anomaly has been in existence for billions of years and placed severe constraints on mantle convection models.
Abstract: Basalts from many Southern Hemisphere regions have anomalous Sr and Pb isotopic characteristics. This article shows that the isotopic mantle anomaly is globe-encircling in extent, centred on latitude 30° S. Arguments suggesting that this mantle anomaly has been in existence for billions of years place severe constraints on mantle convection models.

2,321 citations

"Chemical and isotopic systematics o..." refers background or methods in this paper

  • ...1982; Palacz & Saunders 1986), mantle enrichment through melt migration from the LVZ into oceanic and continental lithosphere (eg Sun 1980; Hart et al. 1986) or derivation of OIBs from the lower mantle which has lost lead by continuous core formation (eg Vidal & Dosso 1978). However, Newsom et al. (1986) showed that St Helena basalts have the same molybdenum (highly chalcophile) to praseodymium (highly lithophile) abundance ratios as MORBs and other OIBs, effectively arguing against continuous core formation. The EM-type character is generally considered to be related to processes associated with convergent margins, such as the recycling of sediments with oceanic crust (eg Hawkesworth et al. 1979; Cohen & O'Nions 1982; White 1985; Weaver et al. 1986). The formation of these OIB sources from remobilization or delamination of metasomatized enriched continental lithosphere has also been proposed (eg Richardson et al. 1982; McKenzie & O'Nions 1983; Hawkesworth et al. 1986). Multiple origins for EM-type mantle is likely, including superposition of different processes. Menzies (1983) suggested that EM1 could be related to enrichment by the introduction of CO2-rich silicate melt (eg kimberlite, nephelinite) whereas the high Rb/Sr, 878r/86Sr character of EM2 is similar to some modern island arc basalts (eg White 1985)....

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  • ...More recently, Hart et al. (1986) pointed out that HIMU and EM1...

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  • ...Schematic diagram of the ENd versus 87Sr/S6Sr plot for OIB data to show the fields of different types of oceanic basalts and the end-member assigned by Zindler & Hart (1986). Modified from Hart et al. (1986)....

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  • ...Zindler & Hart (1986) used different terminology to define the characteristics of mantle end-members: DMM (depleted MORB mantle), PREMA (prevalent mantle, including Iceland, Galapagos, the Easter Islands of White's MORB group and the Hawaiian islands), HIMU (long-term high U/Pb in the source, including St Helena, Tubuai, Mangaia), EM1 (enriched mantle type 1 for the Kerguelen type) and EM2 (enriched mantle type 2 for the Society Island type)....

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  • ...Schematic diagram of the ENd versus 87Sr/S6Sr plot for OIB data to show the fields of different types of oceanic basalts and the end-member assigned by Zindler & Hart (1986). Modified from Hart et al....

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Journal Article•DOI•
The Generation and Compaction of Partially Molten Rock

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Dan McKenzie
01 Aug 1984-Journal of Petrology
TL;DR: Uounu et al. as mentioned in this paper derived the equations governing the movement of the melt and the matrix of a partially molten material from the conservation of mass, momentum, and energy using expressions from the theory of mixtures.
Abstract: The equations governing the movement of the melt and the matrix of a partially molten material are obtained from the conservation of mass, momentum, and energy using expressions from the theory of mixtures. The equations define a length scale dc called the compaction length, which depends only on the material properties of the melt and matrix. A number of simple solutions to the equations show that, if the porosity is initially constant, matrix compaction only occurs within a distance ~<5C of an impermeable boundary. Elsewhere the gravitational forces are supported by the viscous stresses resulting from the movement of melt, and no compaction occurs. The velocity necessary to prevent compaction is known as the minimum fluidization velocity. In all cases the compaction rate is controlled by the.properties of the matrix. These results can only be applied to geological problems if the values of the permeability, bulk and shear viscosity of the matrix can be estimated. All three depend on the microscopic geometry of the melt, which is in turn controlled by the dihedral angle. The likely equilibrium network provides some guidance in estimating the order of magnitude of these constants, but is no substitute for good measurements, which are yet to be carried out. Partial melting by release of pressure at constant entropy is then examined as a means of produced melt within the earth. The principal results of geological interest are that a mean mantle temperature of 1350 °C is capable of producing the oceanic crustal thickness by partial melting. Local hot jets with temperatures of 1550 °C can produce aseismic ridges with crustal thicknesses of about 20 km on ridge axes, and can generate enough melt to produce the Hawaiian Ridge. Higher mantle temperatures in the Archaean can produce komatiites if these are the result of modest amounts of melting at depths of greater than 100 km, and not shallow melting of most of the rock. The compaction rate of the partially molten rock is likely to be rapid, and melt-saturated porosities in excess of perhaps 3 per cent are unlikely to persist anywhere over geological times. The movement of melt through a matrix does not transport major and trace elements with the mean velocity of the melt, but with a slower velocity whose magnitude depends on the distribution coefficient. This effect is particularly important when the melt fraction is small, and may both explain some geochemical observations and provide a means of investigating the compaction process within the earth. I N T R O D U C T I O N There is an obvious need for a simple physical model which can describe the generation of a partially molten rock, and the separation of the melt from the residual solid, which will be referred to as the matrix. If such a model is to be useful it must lead to differential equations which can be solved by standard methods. The principal aim of this paper is to propose such a model, derive the governing equations, and obtain some solutions for particularly simple cases. The model is concerned with the physics, rather than the chemistry, of the process, though the formulation is sufficiently general to allow the inclusion of complicated phase equilibria. Several effects whose importance is unclear have not been included, in order to obtain the simplest model which can describe the generation and extraction of magma. Generation of a magma containing few solid crystals requires two operations. A partially mohen rock must first be generated, either by supplying heat or by reducing the pressure and so changing the solidus temperature. Once such a rock has been formed, the melt must UounuJ of Petrology, Vol. 25, Pirt 3, pp. 713-765, 19841 at W asngton U niersity at St L ouis on M arch 5, 2013 http://petroxfordjournals.org/ D ow nladed from

1,772 citations

Journal Article•DOI•
Plumbotectonics-the model

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R.E. Zartman1, B.R. Doe1•
United States Geological Survey1
10 May 1981-Tectonophysics
TL;DR: Plumbotectonics is an attempt to model the geochemical behaviour of U, Th and Pb, among major terrestrial reservoirs in agreement with observational data as discussed by the authors, by recycling rock through the orogenic environment, a dynamically communicating upper crust, lower crust, and mantle can produce the required patterns of lead-isotope evolution.

1,562 citations

Journal Article•DOI•
Nb and Pb in oceanic basalts: new constraints on mantle evolution

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Albrecht W. Hofmann1, Klaus Peter Jochum1, M. Seufert1, William M. White1•
Max Planck Society1
01 Aug 1986-Earth and Planetary Science Letters
TL;DR: In this paper, the authors proposed a new constraint on mantle composition: the differentiated part of the mantle, chemically depleted after separation of the major portion of the continental crust, was subsequently internally rehomogenized.

1,475 citations

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