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No direct contribution of recycled crust in Icelandic basalts

S. Lambart1,2

1Department of Earth and Planetary Sciences, University of California Davis, One Shields Avenue, Davis, California 95616, USA
2School of Earth and Ocean Sciences, Cardiff University, CF10 3AT Cardiff, UK

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Lambart, S. (2017) No direct contribution of recycled crust in Icelandic basalts. Geochem. Persp. Let. 4, 7–12.

National Science Foundation grant EAR-1551442 and the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 663830.

Geochemical Perspectives Letters v4  |  doi: 10.7185/geochemlet.1728
Received 02 April 2017  |  Accepted 06 June 2017  |  Published 12 July 2017
Copyright © 2017 The author




Figure 1 (a) Representation of the melting column in the three configurations. Colours show the lithologies that are partially melting at a given pressure. (b) Contribution of the recycled crust (tcR.C./tc) to the melt production as functions of the pressure along the adiabatic path in G2- (red), KG1- (orange) and KG2- (blue) configurations. The contribution of the recycled crust is assumed to be equal to the contribution of G2, to half of the contibution of KG1 and to one third of the contribution of KG2, in the respective configurations.
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Figure 2 Compositions of the aggregated melts produced over the melting column in G2- (red), KG1- (orange) and KG2- (blue) configurations. Grey dots are the compositions of Icelandic basalts with MgO contents between 9.5 and 17 wt. % from the Northern Volcanic zone, the Reykjanes Peninsula, the Snaefellsnes area and the South Eastern Volcanic Zone (GEOROC). Detailed explanations of the calculations are given in the Supplementary Information.
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Supplementary Figures and Tables


Figure S-1 Results of the Melt-PX calculations for the G2-configuration at a potential temperature of 1480 °C. (a) Pressure-temperature path for the column of mantle undergoing isentropic decompression (black line). The solid red and the dashed green lines are the solidi of G2 and KLB-1, respectively. (b-c) Extent of the melting (b) and melt productivity (c) of G2 (solid red line) and KLB-1 (dashed green line) along the adiabatic path.
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Figure S-2 Results of the Melt-PX calculations for the KG1-configuration at a potential temperature of 1480 °C. (a) Pressure-temperature path for the column of mantle undergoing isentropic decompression (black line). The solid orange and the dashed green lines are the solidi of KG1 and KLB-1, respectively. (b-c) Extent of the melting (b) and melt productivity (c) of KG1 (solid orange line) and KLB-1 (dashed green line) along the adiabatic path.
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Figure S-3 Results of the Melt-PX calculations for the KG2-configuration at a potential temperature of 1480 °C. (a) Pressure-temperature path for the column of mantle undergoing isentropic decompression (black line). The solid blue and the dashed green lines are the solidi of KG1 and KLB-1, respectively. (b-c) Extent of the melting (b) and melt productivity (c) of KG1 (solid blue line) and KLB-1 (dashed green line) along the adiabatic path.
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Figure S-4 Evolution of the solid phase modes for the composition KLB-1 (Hirose and Kushiro, 1993) as a function of the proportion of melt during batch melting (solid lines) and continuous melting (dashed lines). The threshold for melt segregation in the continuous melting calculations is 1 %. Calculations were performed at 1 GPa using the thermodynamic model pMELTS (Ghiorso et al., 2002) and the alphaMELTS front-end (Smith and Asimow, 2005). Olivine: red; orthopyroxene (opx): orange; clinopyroxene (cpx): blue; spinel (sp): green.
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Figure S-5 Primitive mantle (PM; Sun and McDonough, 1989) normalised trace element patterns of the first degree melts (dashed lines) and the last accumulated melts produced at the base of the crust (solid lines) in G2- (red), KG1- (orange) and KG2- (blue) configurations.
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Figure S-6 Incompatible trace element ratios of the calculated accumulated melts as functions of the pressure in the three configurations (colour code is the same as in Fig. S-5). Solid lines represent the formation pressure of the first degree melt from the enriched mantle component (G2, KG1 or KG2) and dashed lines represent the formation pressure of the first degree melt from the peridotite component in the corresponding mantle configuration. The grey areas represent the range of compositional ratios in Icelandic basalts with MgO contents between 9.5 and 17 wt. % from the Northern Volcanic zone, the Reykjanes Peninsula, the Snaefellsnes area and the South Eastern Volcanic Zone (GEOROC).
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Figure S-7 Comparison of SiO2 (a) and MgO (b) contents of the melt produced by G2 (red circles; Pertermann and Hirschmann, 2003), KG1 and KG2 (orange and blue squares, respectively; Kogiso et al., 1998), Px-1 (black-diamond; Sobolev et al., 2007), and KLB-1 (green triangles; Hirose and Kushiro, 1993) at 3 GPa.
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Figure S-8 Near-solidus curves (T5%) (a) and melting curves at 3 GPa (b) calculated using Melt-PX (Lambart et al., 2016) for Px-1 (black; Sobolev et al., 2007) and KG1 (orange; Kogiso et al., 1998) compositions.
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Figure S-9 Ni content of olivines from Icelandic basalts (large dark grey circles, Sobolev et al., 2007; large light grey circles, Shorttle and Maclennan, 2011). The lines are modelled olivine compositions produced by fractionally crystallising aggregated parental melts sampled at 4, 1.5 and 0.6 GPa along the adiabatic path in the KG1-configuration. The melts chosen for modelling are reported in Table S-3. Parental melts then had equilibrium olivine fractionally extracted from them at 1 bar using olivine compositions calculated with PRIMELT2.xls (Herzberg and Asimow, 2008) and according the Ni partitioning model of Matzen et al. (2017). Data from Sobolev et al. (2007) in other locations are also shown for comparison (small dark grey circles). See text for details of calculations.
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Table S-1 Majora, traceb element and isotopic compositions of G2, KLB-1, KG1, KG2 and Bulk1.

G2cKLB-1dKG1eKG2eBulk1f
SiO250.0544.484746.245.04
TiO21.970.160.780.570.34
Al2O315.763.599.757.694.81
FeO9.358.19.779.228.23
MnO0.170.12000.13
MgO7.939.2223.628.836.09
CaO11.743.447.356.054.27
Na2O3.040.31.521.110.57
K2O0.030.020.120.090.02
Ni2001964108213761788
Rb1.1880.020.6040.4090.137
Ba19.320.2279.7746.5912.136
Th0.1350.0040.070.0480.017
U0.0460.00180.02390.01650.0062
Nb6.130.08643.10822.10090.6908
Cla2.6950.1341.4150.9880.39
Ce8.1610.4214.2913.0011.195
Sr98.116.09252.10136.76515.294
Nd8.3750.4834.4293.1141.272
Zr654.26934.63524.51310.342
Sm2.30.211.260.910.42
Hf1.7090.1270.9180.6540.285
Eu1.0550.0860.5710.4090.183
Gd3.70.3242.0121.4490.662
Tb0.70.0640.3820.2760.128
Dy4.40.4712.4361.7810.864
Ho1.150.1080.6290.4550.212
Y24.723.12913.92510.3265.288
Er2.6530.3291.4911.1040.561
Yb3.40.3481.8741.3650.653
Lu0.3710.0560.2140.1610.088
143Nd/144Nd0.51270.51340.5127380.5128190.512939
87Sr/86Sr0.70370.7020.7036360.7034930.703306

a in wt. %
b in ppm
c G2: Major element composition is from Perterman and Hirschmann (2003); Ni content is from Sobolev et al. (2007); trace element composition corresponds to the composition K11 from Koorneff et al. (2012b); isotopic composition corresponds to a 2 Ga recycled oceanic crust altered by sea water and modified during the subduction process by dehydration using the model of Stracke et al. (2003).
d KLB-1: Major element composition and Ni content are from Hirose and Kushiro (1993); trace element composition is DDMM from Workman and Hart (2005); isotopic composition corresponds to the extreme D-MORB from Salters and Stracke (2004).
e KG1 and KG2: Major element compositions are from Kogiso et al. (1998); Ni content and trace element and isotopic compositions calculated as 1G2:1KLB-1 and 1G2:2KLB-1, respectively.
f Bulk1: Major, trace element and isotopic compositions are calculated as 1G2:9KLB-1.

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Table S-2 Melt compositions and parameters used in olivine fractionation modelling.
P4 GPa1.5 GPa
0.6 GPa

KG1aKG1bKLB-1cKG1bKLB-1d
SiO24349.948.649.950.7
TiO23.320.451.160.450.42
Al2O315.513.814.313.814.6
FeO11.57.929.197.927.64
MgO14.215.713.515.713.4
CaO7.8210.710.210.711.2
Na2O3.681.042.651.041.5
K2O0.870.040.210.040.19
F e248.516.47123
Xol f20.811.559.52970.7
Xopxf1.817.516.605.5
Xcpxf47.221.4700.6
Xgtf29.90000
Xspf0.31.10.500.2
TLg17851712166216671616
Fog88.39290.192.391.5
DNiol/liq h4.254.615.584.966.19
Ni in melti636657498504415

a Major-element composition used to model the KG1-derived melt at 4 GPa (glass in run #KH22 in Kogiso et al., 1998).
b Major-element composition used to model the KG1-derived melt at 1.5 GPa and 0.6 GPa. GPa (glass in run #KH43 in Kogiso et al., 1998).
d Major-element composition used to model the KBL-1-derived melt at 0.6 GPa (glass in run #14 in Hirose and Kushiro, 1993).
e Melting degree calculated with Melt-PX at the corresponding pressure along the adiabatic path.
f Mode of the residual solid phases of each lithology at the corresponding pressure along the adiabatic path.
g Calculated liquidus temperature (TL) in kelvin and forsterite content (Fo) of the olivine in equilibrium with each liquid at the corresponding pressure (Herzberg and Asimow, 2008).
h Calculated DNiol/liq using the Ni partitioning model from Matsen et al. (2017).
i Ni content (in ppm) in the melts. Contents in melts from KG1 and KLB1 are calcuated using the modelled DNiol/liq, and using Ni partitioning callibration for orthopyroxene-melt (Beattie et al., 1991), olivine-garnet (Canil, 1999) and orthopyroxene-clinopyroxene (Seitz et al., 1999).

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Table S-3 Compositions of the aggregated parental melt (APM) sampled at 4, 1.5 and 0.6 GPa and of the olivine in equilibrium at 1 bar.

4 GPa1.5 GPa0.6 GPa
tcpyr/tc a10.540.53
SiO2 (wt. %)4349.249.5
TiO2 (wt. %)3.320.830.84
Al2O3 (wt. %)15.514.114.4
FeO (wt. %)11.58.618.52
MgO (wt. %)14.214.513.5
CaO (wt. %)7.8210.410.6
Na2O (wt. %)3.681.92.16
K2O (wt. %)0.870.130.2
Ni (ppm)636571468
TLb160116091586
Fob9091.691.1
DNiol/liq c5.725.766.44
Ni in ol d364132883016

a Contribution of the melt derived from KG1 to the volume of magma produced.
b Calculated liquidus temperature (TL) and forsterite content (Fo) of the olivine in equilibrium with APM at 1bar (Herzberg and Asimow, 2008).
c DNiol/liq at 1 bar using Matzen et al. (2017) model.
d Ni content (in ppm) in olivine in equilibrium with APM at 1 bar.

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