Ancient mantle plume components constrained by tungsten isotope variability in arc lavas
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Keywords: tungsten isotopes, 182W, subduction zones, Central America, mantle-plume, rutile, slab melt
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Abstract
Figures
 Figure 1 Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011), Kurzweil et al. (2019), Mazza et al. (2020), and Stubbs et al. (2022). MORB and OIB fields defined after König et al. (2011) and Kurzweil et al. (2019). Adakitic rocks from Laeger et al. (2013) and Straub et al. (2015). |  Figure 2 Two component mixing models for melts derived from a depleted mantle or an enriched mantle modified by Cocos and Coiba Ridge (CCR) melts. Endmember compositions and model parameters can be found in the Supplementary Information. Samples with W/Th > 0.2 not shown. |  Figure 3 Two component mixing models between modelled slab melt and three different mantle compositions: (a) mixing with depleted mantle to model the W isotope composition of adakites and (b) mixing with two types of enriched mantle (models A and B) to produce the source composition of basanites. Grey dashed lines represent the error of the W isotopic composition of the upper mantle. Model parameters can be found in the Supplementary Information. |
| Figure 1 | Figure 2 | Figure 3 |
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Introduction
Mass transfer from variable components of the subducting oceanic lithosphere into the arc mantle and subsequent incorporation into arc magmas represents a major paradigm in Earth Sciences. While there is strong evidence for the involvement of fluids and subducted sediments in the mantle source of many arc magmas (Tera et al., 1986
Tera, F., Brown, L., Morris, J., Sacks, I.S., Klein, J., Middleton, R. (1986) Sediment incorporation in island-arc magmas: Inferences from 10Be. Geochimica et Cosmochimica Acta 50, 535–550. https://doi.org/10.1016/0016-7037(86)90103-1
), the nature of direct contributions of subducted basaltic crust remains debated. However, slab melting under certain conditions has become central to many models of subduction zone processes (e.g., Yogodzinski et al., 2015Yogodzinski, G.M., Brown, S.T., Kelemen, P.B., Vervoort, J.D., Portnyagin, M., Sims, K.W.W., Hoernle, K., Jicha, B.R., Werner, R. (2015) The Role of Subducted Basalt in the Source of Island Arc Magmas: Evidence from Seafloor Lavas of the Western Aleutians. Journal of Petrology 56, 441–492. https://doi.org/10.1093/petrology/egv006
). Here, we use isotope and concentration data for W in arc-related rocks to trace slab- and plume-derived source components in arc magmas. Variations in the distribution of 182W in terrestrial rocks must have been established within the first 50 Myr of Earth’s history due to the short half-life of its extinct parent isotope 182Hf (e.g., Willbold et al., 2011Willbold, M., Elliott, T., Moorbath, S. (2011) The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature 477, 195–198. https://doi.org/10.1038/nature10399
). The only known modern setting exhibiting negative 182W variability is ocean islands associated with deep-seated mantle plumes, such as Galápagos (e.g., Mundl-Petermeier et al., 2020Mundl-Petermeier, A., Walker, R.J., Fischer, R.A., Lekic, V., Jackson, M.G., Kurz, M.D. (2020) Anomalous 182W in high 3He/4He ocean island basalts: Fingerprints of Earth’s core? Geochimica et Cosmochimica Acta 271, 194–211. https://doi.org/10.1016/j.gca.2019.12.020
). In this context, the Central American arc system is a prime location for using W isotopes as a tracer for oceanic crust and plume-mantle components in arc magmas. Here, the 13 to 15 Ma old Cocos and Coiba Ridge (CCR), and other hotspot traces related to the Galápagos plume, are being subducted along the Panama–Costa Rica section of the Central American arc system (Hauff et al., 2000Hauff, F., Hoernle, K., van den Bogaard, P., Alvarado, G., Garbe-Schönberg, D. (2000) Age and geochemistry of basaltic complexes in western Costa Rica: Contributions to the geotectonic evolution of Central America. Geochemistry, Geophysics, Geosystems 1, 1009. https://doi.org/10.1029/1999GC000020
; Abratis and Wörner, 2001Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
; Gazel et al., 2009Gazel, E., Carr, M.J., Hoernle, K., Feigenson, M.D., Szymanski, D., Hauff, F., van de Bogaard, P. (2009) Galapagos-OIB signature in southern Central America: Mantle refertilization by arc–hot spot interaction. Geochemistry, Geophysics, Geosystems 10, Q02S11. https://doi.org/10.1029/2008GC002246
, 2011Gazel, E., Hoernle, K., Carr, M.J., Herzberg, C., Saginor, I., van den Bogaard, P., Hauff, F., Feigenson, M., Swisher III, C. (2011) Plume–subduction interaction in southern Central America: Mantle upwelling and slab melting. Lithos 121, 117–134. https://doi.org/10.1016/j.lithos.2010.10.008
). About 1.5 to 5 Ma old adakitic lavas from Panama and Costa Rica are of particular interest, since involvement of a slab melt component in their petrogenesis has previously been proposed (e.g., Defant et al., 1991Defant, M.J., Clark, L.F., Stewart, R.H., Drummond, M.S., de Boer, J.Z., Maury, R.C., Bellon, H., Jackson, T.E., Restrepo, J.F. (1991) Andesite and dacite genesis via contrasting processes: the geology and geochemistry of El Valle Volcano, Panama. Contributions to Mineralogy and Petrology 106, 309–324. https://doi.org/10.1007/BF00324560
; Abratis and Wörner, 2001Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
; Gazel et al., 2009Gazel, E., Carr, M.J., Hoernle, K., Feigenson, M.D., Szymanski, D., Hauff, F., van de Bogaard, P. (2009) Galapagos-OIB signature in southern Central America: Mantle refertilization by arc–hot spot interaction. Geochemistry, Geophysics, Geosystems 10, Q02S11. https://doi.org/10.1029/2008GC002246
). Identification of negative W isotope anomalies in these adakites would thus provide a strong, first-hand indication for the involvement of plume-derived subducted oceanic crust in arc melts from the Central American arc system. Further, a suite of alkaline mafic lavas (basanites) in the back-arc in Costa Rica dated at 4 to 6 Ma possibly record a mantle contribution from the Galápagos plume (Abratis and Wörner, 2001Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
). Here, radiogenic W isotope systematics provide a powerful tracer to identify different source components that may be derived from the Galápagos plume.top
Samples and Methods
We selected 14 well-characterised adakites from the Costa Rica and Panama arc front and five basanites from behind the volcanic arc of southern Costa Rica for W isotope and trace element analysis. To constrain the isotopic composition of subducted material we also analysed ocean island basalt (OIB) terranes that were accreted to the forearc of Costa Rica and Panama. The latter were interpreted to represent 18 to 71 Ma old hotspot tracks of the Galápagos plume (e.g., Appel et al., 1994
Appel, H., Wörner, G., Alvarado, G., Rundle, C., Kussmaul, S. (1994) Age relations in igneous rocks from Costa Rica. Profil 7, 63–69.
; Hauff et al., 2000Hauff, F., Hoernle, K., van den Bogaard, P., Alvarado, G., Garbe-Schönberg, D. (2000) Age and geochemistry of basaltic complexes in western Costa Rica: Contributions to the geotectonic evolution of Central America. Geochemistry, Geophysics, Geosystems 1, 1009. https://doi.org/10.1029/1999GC000020
; Wegner et al., 2011Wegner, W., Wörner, G., Harmon, R.S., Jicha, B.R. (2011) Magmatic history and evolution of the Central American Land Bridge in Panama since Cretaceous times. Bulletin of the Geological Society of America 123, 703–724. https://doi.org/10.1130/B30109.1
; Gazel et al., 2018Gazel, E., Trela, J., Bizimis, M., Sobolev, A., Batanova, V., Class, C., Jicha, B. (2018) Long-Lived Source Heterogeneities in the Galapagos Mantle Plume. Geochemistry, Geophysics, Geosystems 19, 2764–2779. https://doi.org/10.1029/2017GC007338
). Further details on the samples as well as Sr, Pb and Nd isotope compositions can be found in Appel et al. (1994)Appel, H., Wörner, G., Alvarado, G., Rundle, C., Kussmaul, S. (1994) Age relations in igneous rocks from Costa Rica. Profil 7, 63–69.
, Abratis and Wörner (2001)Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
and Wegner et al. (2011)Wegner, W., Wörner, G., Harmon, R.S., Jicha, B.R. (2011) Magmatic history and evolution of the Central American Land Bridge in Panama since Cretaceous times. Bulletin of the Geological Society of America 123, 703–724. https://doi.org/10.1130/B30109.1
. The W isotopic compositions are reported as μ182W, representing the part per million deviation of the 182W/184W ratio of a sample from W standard NIST 3163. Detailed descriptions of methods and analytical results are provided in the Supplementary Information.top
Results and Discussion
The adakites range in SiO2 content between 53 to 69 wt. % and show high Sr/Y ratios from 100 to 200 at low Y concentrations of 7 to 14 μg/g. They feature prominent depletions in high field strength elements (HFSE) and are low in heavy rare earth elements (HREE) due to melting of hydrous meta-basalt with residual rutile and garnet (Figure S-1; Martin et al., 2005
Martin, H., Smithies, R.H., Rapp, R., Moyen, J.-F., Champion, D. (2005) An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24. https://doi.org/10.1016/j.lithos.2004.04.048
). Their W isotopic compositions range from μ182W = −6.89 ± 2.95 to +0.87 ± 2.95 (external reproducibility, 2 s.d.). There are no observable correlations between μ182W and either major or trace element concentrations, their ratios or with any radiogenic isotope ratios. Basanites have SiO2 concentrations from 43 to 47 wt. % with high MgO of 6.3 to 9.3 wt. %. They show trace element patterns that are strongly enriched in incompatible elements with notable depletions in HFSE comparable to the adakites. Although their Sr/Y ratios are elevated compared to normal arc lava and range between 42 and 120, they also have high Y concentrations (17.5 to 30 μg/g) and are silica-undersaturated, which places them outside the compositional range expected for adakitic rocks (Martin et al., 2005Martin, H., Smithies, R.H., Rapp, R., Moyen, J.-F., Champion, D. (2005) An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24. https://doi.org/10.1016/j.lithos.2004.04.048
). Values for μ182W range from −9.04 ± 4.32 to +1.74 ± 4.32. Similar to the adakites, no correlations with other chemical or radiogenic isotope tracers can be observed. Accreted OIB have MgO concentrations ranging from 6 to 21 wt. %. Trace element patterns show typical intra-plate affinities, similar to the modern Galápagos archipelago with enriched incompatible elements and a relative depletion in Pb. Their μ182W ranges from −9.72 ± 4.8 to +0.98 ± 2.95. Thus, as a first-order observation, all three rock types related to the Costa Rica–Panama subduction zone show resolvable W isotope deficits. In the following, we will address likely scenarios that can reconcile this observation.Previous results for modern basalts from the Galápagos archipelago, together with our own data for the accreted OIB terranes, provide an approximation of the isotopic composition of the basalts from the CCR, that are currently subducted below Central America. A chemical and isotopic zonation within the Galápagos plume (Hoernle et al., 2000
Hoernle, K., Werner, R., Morgan, J.P., Garbe-Schönberg, D., Bryce, J., Mrazek, J. (2000) Existence of complex spatial zonation in the Galápagos plume. Geology 28, 435–438. https://doi.org/10.1130/0091-7613(2000)28<435:EOCSZI>2.0.CO;2
) is mirrored by contrasting negative W isotopic compositions of basalts from the central and eastern domains of the Galápagos islands (μ182W = −22 and −5, respectively; Mundl-Petermeier et al., 2020Mundl-Petermeier, A., Walker, R.J., Fischer, R.A., Lekic, V., Jackson, M.G., Kurz, M.D. (2020) Anomalous 182W in high 3He/4He ocean island basalts: Fingerprints of Earth’s core? Geochimica et Cosmochimica Acta 271, 194–211. https://doi.org/10.1016/j.gca.2019.12.020
). This chemical zonation is also reflected in the CCR, as well as in the basaltic rocks accreted in the Central American forearc (Gazel et al., 2018Gazel, E., Trela, J., Bizimis, M., Sobolev, A., Batanova, V., Class, C., Jicha, B. (2018) Long-Lived Source Heterogeneities in the Galapagos Mantle Plume. Geochemistry, Geophysics, Geosystems 19, 2764–2779. https://doi.org/10.1029/2017GC007338
and references therein). We find that the W isotopic compositions of the accreted CCR rocks analysed here do not fully reflect the entire range observed in the modern Galápagos archipelago. However, μ182W deficits of up to −9.72 ± 4.80 confirm that the Galápagos plume is isotopically variable and, more importantly, show that the incorporated primordial W isotopic signature has existed for at least the past 70 Myr. This implies that the unusual W isotopic signature is a long-lived, persistent characteristic of the plume. If equivalents of such basaltic rocks from the CCR are also subducted to the depth where magmas are formed, these arc magmas would also be expected to show similar μ182W deficits.This is, in fact, supported by our observations: the μ182W deficits of up to −6.89 ± 2.95 in the adakites cover almost the entire range of μ182W variations measured in the accreted CCR basalts, providing a clear indication for involvement of a Galápagos plume component in their source. We will now test whether partial melts of the subducted basalts from the CCR contributed to the μ182W deficits or, alternatively, the mantle wedge below Costa Rica and Panama contained material from the Galápagos plume, as was proposed for the origin of the basanites (Abratis and Wörner, 2001
Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
). The geochemical behaviour of W in subduction zones is best studied using W/Th ratios (König et al., 2008König, S., Münker, C., Schuth, S., Garbe-Schönberg, D. (2008) Mobility of tungsten in subduction zones. Earth and Planetary Science Letters 274, 82–92. https://doi.org/10.1016/j.epsl.2008.07.002
). Bulk partition coefficients of W and Th are very similar during mantle melting (Arevalo and McDonough, 2008Arevalo Jr., R., McDonough, W.F. (2008) Tungsten geochemistry and implications for understanding the Earth’s interior. Earth and Planetary Science Letters 272, 656–665. https://doi.org/10.1016/j.epsl.2008.05.031
), resulting in only small variations of W/Th ratios in oceanic basalts (MORB = 0.09 to 0.24, OIB = 0.08 to 0.19; König et al., 2011König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
; Kurzweil et al., 2019Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
). During differentiation of mafic magmas, this ratio should remain constant. However, W is mobile in subduction zone fluids (Bali et al., 2012Bali, E., Keppler, H., Audetat, A. (2012) The mobility of W and Mo in subduction zone fluids and the Mo–W–Th–U systematics of island arc magmas. Earth and Planetary Science Letters 351–352, 195–207. https://doi.org/10.1016/j.epsl.2012.07.032
), resulting in elevated W/Th ratios in arc magmas compared to MORB and OIB (Fig. 1; König et al., 2008König, S., Münker, C., Schuth, S., Garbe-Schönberg, D. (2008) Mobility of tungsten in subduction zones. Earth and Planetary Science Letters 274, 82–92. https://doi.org/10.1016/j.epsl.2008.07.002
; Stubbs et al., 2022Stubbs, D., Yang, R., Coath, C.D., John, T., Elliott, T. (2022) Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids. Geochimica et Cosmochimica Acta 334, 135–154. https://doi.org/10.1016/j.gca.2022.08.005
). Indeed, W/Th ratios for “normal” arc lavas from Central America, with W/Th ranging from 0.05 to 0.43, fall into the global arc magma range (Fig. 1). In contrast, adakites and basanites show surprisingly low W/Th ratios between 0.02 and 0.06, substantially lower than MORB, OIB and most arc front lava previously measured. Only five of the 19 adakites and basanite samples have elevated W/Th (>0.09). These also record high Ba/Th ratios of >280 or high 87Sr/86Sr ratios of >0.704, in line with additional fluid or sedimentary components in their source (Fig. 1, Table S-1; Stubbs et al., 2022Stubbs, D., Yang, R., Coath, C.D., John, T., Elliott, T. (2022) Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids. Geochimica et Cosmochimica Acta 334, 135–154. https://doi.org/10.1016/j.gca.2022.08.005
). Neither involvement of slab fluids, nor the addition of an enriched mantle source, can explain the exceptionally low average W/Th ratios in the remaining adakites and basanites, because such components would result in higher, not lower, W/Th ratios. On the other hand, such low W/Th ratios could be due to melting of subducted basalts with residual rutile, where rutile preferentially retains W and other HFSE (Rudnick et al., 2000Rudnick, R.L., Barth, M., Horn, I., McDonough, W.F. (2000) Rutile-Bearing Refractory Eclogites: Missing Link Between Continents and Depleted Mantle. Science 287, 278–281. https://doi.org/10.1126/science.287.5451.278
; Zack et al., 2002Zack, T., Kronz, A., Foley, S.F., Rivers, T. (2002) Trace element abundances in rutiles from eclogites and associated garnet mica schists. Chemical Geology 184, 97–122. https://doi.org/10.1016/S0009-2541(01)00357-6
; Bali et al., 2012Bali, E., Keppler, H., Audetat, A. (2012) The mobility of W and Mo in subduction zone fluids and the Mo–W–Th–U systematics of island arc magmas. Earth and Planetary Science Letters 351–352, 195–207. https://doi.org/10.1016/j.epsl.2012.07.032
). Strong depletions of Nb, Ta and Ti in adakites and basanites also make a strong case for the involvement of rutile (Fig. S-1). Moreover, elevated Nb/Ta ratios in both adakites (18.01 ± 1.86) and basanites (20.1 ± 1.85) compared to typical values found in oceanic basalts (Nb/Ta = 14.5 to 16.5; Gale et al., 2013Gale, A., Dalton, C.A., Langmuir, C.H., Su, Y., Schilling, J.-G. (2013) The mean composition of ocean ridge basalts. Geochemistry, Geophysics, Geosystems 14, 489–518. https://doi.org/10.1029/2012GC004334
; Tang et al., 2019Tang, M., Lee, C.-T.A., Chen, K., Erdman, M., Costin, G., Jiang, H. (2019) Nb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation. Nature Communications 10, 235. https://doi.org/10.1038/s41467-018-08198-3
) are complementary to low Nb/Ta ratios in rutile (Green and Pearson, 1987Green, T.H., Pearson, N.J. (1987) An experimental study of Nb and Ta partitioning between Ti-rich minerals and silicate liquids at high pressure and temperature. Geochimica et Cosmochimica Acta 51, 55–62. https://doi.org/10.1016/0016-7037(87)90006-8
). Combined, the unusual W isotope deficits and low W/Th ratios make a strong case that the petrogenesis of adakites and basanites is linked to partial melting of a subducted metabasaltic source derived from the Galápagos plume. This either involves the slab melt directly or a mantle source modified by slab melts derived from CCR basalts.Figure 1 Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011)
König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
, Kurzweil et al. (2019Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
), Mazza et al. (2020)Mazza, S.E., Stracke, A., Gill, J.B., Kimura, J.-I., Kleine, T. (2020) Tracing dehydration and melting of the subducted slab with tungsten isotopes in arc lavas. Earth and Planetary Science Letters 530, 115942. https://doi.org/10.1016/j.epsl.2019.115942
, and Stubbs et al. (2022)Stubbs, D., Yang, R., Coath, C.D., John, T., Elliott, T. (2022) Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids. Geochimica et Cosmochimica Acta 334, 135–154. https://doi.org/10.1016/j.gca.2022.08.005
. MORB and OIB fields defined after König et al. (2011)König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
and Kurzweil et al. (2019)Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
. Adakitic rocks from Laeger et al. (2013)Laeger, K., Halama, R., Hansteen, T., Savov, I.P., Murcia, H.F., Cortés, G.P., Garbe-Schönberg, D. (2013) Crystallization conditions and petrogenesis of the lava dome from the ∼900 years BP eruption of Cerro Machín Volcano, Colombia. Journal of South American Earth Sciences 48, 193–208. https://doi.org/10.1016/j.jsames.2013.09.009
and Straub et al. (2015)Straub, S.M., Gómez-Tuena, A., Bindeman, I.N., Bolge, L.L., Brandl, P.A., et al. (2015) Crustal recycling by subduction erosion in the central Mexican Volcanic Belt. Geochimica et Cosmochimica Acta 166, 29–52. https://doi.org/10.1016/j.gca.2015.06.001
.Based on the large range of silica content, it was argued that the adakites in Costa Rica and Panama do not represent pure slab melts, but rather derive from a mantle wedge metasomatised by slab melts (Gazel et al., 2009
Gazel, E., Carr, M.J., Hoernle, K., Feigenson, M.D., Szymanski, D., Hauff, F., van de Bogaard, P. (2009) Galapagos-OIB signature in southern Central America: Mantle refertilization by arc–hot spot interaction. Geochemistry, Geophysics, Geosystems 10, Q02S11. https://doi.org/10.1029/2008GC002246
, 2011Gazel, E., Hoernle, K., Carr, M.J., Herzberg, C., Saginor, I., van den Bogaard, P., Hauff, F., Feigenson, M., Swisher III, C. (2011) Plume–subduction interaction in southern Central America: Mantle upwelling and slab melting. Lithos 121, 117–134. https://doi.org/10.1016/j.lithos.2010.10.008
; Martin et al., 2005Martin, H., Smithies, R.H., Rapp, R., Moyen, J.-F., Champion, D. (2005) An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24. https://doi.org/10.1016/j.lithos.2004.04.048
). To test this model with our data, we performed simple mixing calculations between a slab-derived melt and a subduction-modified mantle wedge (Fig. 2; see Supplementary Information for model parameters). The source of adakites is best represented by a mantle wedge metasomatised by 3 to 20 wt. % of a slab melt with low W/Th of 0.018. This is in good agreement with previous models using radiogenic isotopes (Gazel et al., 2009Gazel, E., Carr, M.J., Hoernle, K., Feigenson, M.D., Szymanski, D., Hauff, F., van de Bogaard, P. (2009) Galapagos-OIB signature in southern Central America: Mantle refertilization by arc–hot spot interaction. Geochemistry, Geophysics, Geosystems 10, Q02S11. https://doi.org/10.1029/2008GC002246
). The variability of μ182W in the adakites and the lack of correlation with other geochemical parameters require that the slab was heterogeneous in μ182W. Therefore, this model constrains the maximum W isotope deficit of a slab melt necessary to explain the range observed in the adakites. As shown in Figure 3a, assuming μ182W values varying between −12 to 0 for the subducted CCR basalts can reconcile the isotopic compositions of most adakites. Three samples with high Ba/Th and W/Th, however, plot outside of this plausible mixing field, which is likely due to an additional component in their source.Figure 2 Two component mixing models for melts derived from a depleted mantle or an enriched mantle modified by Cocos and Coiba Ridge (CCR) melts. Endmember compositions and model parameters can be found in the Supplementary Information. Samples with W/Th > 0.2 not shown.
Figure 3 Two component mixing models between modelled slab melt and three different mantle compositions: (a) mixing with depleted mantle to model the W isotope composition of adakites and (b) mixing with two types of enriched mantle (models A and B) to produce the source composition of basanites. Grey dashed lines represent the error of the W isotopic composition of the upper mantle. Model parameters can be found in the Supplementary Information.
To account for the enriched trace element signature observed in the basanites, we included an enriched source model component in our calculations. Following slab window formation below Costa Rica and Panama, previous models have argued for the ascent and decompression melting of a mantle component that was derived from the Galápagos plume as the source for the basanites (Abratis and Wörner, 2001
Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
; Gazel et al., 2011Gazel, E., Hoernle, K., Carr, M.J., Herzberg, C., Saginor, I., van den Bogaard, P., Hauff, F., Feigenson, M., Swisher III, C. (2011) Plume–subduction interaction in southern Central America: Mantle upwelling and slab melting. Lithos 121, 117–134. https://doi.org/10.1016/j.lithos.2010.10.008
). However, similar to the case of the adakites, the low W/Th ratios of the basanites require an additional slab melt component. In our model, the enriched mantle composition was estimated from the average Galápagos basalt. Melting of this enriched mantle modified by 2 to 10 wt. % slab melt formed from CCR basalts can explain the observed incompatible element enrichment in basanites while maintaining their low W/Th ratios (Figs. 2, S-2). Finally, we can test how this enriched Galápagos mantle influences the W isotopic composition of the basanites. Model A in Figure 3b uses the enriched mantle composition assuming μ182W = 0, while model B involves a Galápagos mantle with μ182W as low as −6. Each model encompasses the observed basanite compositions including the most anomalous basanite (μ182W = −9.04 ± 4.32). Model A, however, shows that contributions of isotopically anomalous W from the enriched mantle source are not required to explain the variability observed in the basanites. If this mantle source is characterised by depletions in μ182W, values cannot be significantly lower than −6, as it is shown in model B. It is therefore unlikely that this component reflects the composition of the modern central Galápagos domain (Bekaert et al., 2021Bekaert, D.V., Gazel, E., Turner, S., Behn, M.D., de Moor, J.M., et al. (2021) High 3He/4He in central Panama reveals a distal connection to the Galápagos plume. Proceedings of the National Academy of Sciences 118, e2110997118. https://doi.org/10.1073/pnas.2110997118
). In any case, the negative W isotope signal observed in adakties and basanites from Costa Rica and Panama requires a slab melt component that carries the anomalous μ182W from the Galápagos plume.top
Conclusions
The tungsten isotope systematics of the adakites verify melting of subducted oceanic crust at mantle depth in the Central American arc system. Melts derived from a hybridised mantle wedge with negative μ182W signatures provide strong evidence that this contribution is related to Cocos and Coiba Ridges (CCR). In the case of the back-arc basanites, this signature is possibly modified by mantle components derived from the Galápagos plume, although their contribution is not strictly required to explain their isotopic budget. Unusually low W/Th in both adakites and basanites imply control by residual rutile on the W budget of their sources. These observations further strengthen previous proposals for magma genesis for these adakites and basanites related to the evolution of a slab window below Costa Rica and Panama as a consequence of CCR collision with the Central American subduction zone. Finally, we document that the anomalous low μ182W signal is a long-lived (>70 Myr) geochemical signature of the Galápagos plume.
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Acknowledgements
This study was funded through the Priority Programme 1833 “Building a Habitable Earth” of the German Science Foundation (DFG grant No. WI 3579/3-1 to MW). GW acknowledges DFG grants No. WO 362/10 and WO 362/27-2 for providing funds for sampling in the field. We thank Caroline Soderman and Jonas Tusch for their constructive review of the manuscript and Helen Williams for editorial handling. M. Abratis, W. Wegner, S. Rausch, and R. Harmon are thanked for their efforts during strenuous fieldwork in Central America. We acknowledge Rachel Bezard for helpful discussions and Dirk Hoffmann for support with mass spectrometry and clean lab maintenance.
Editor: Helen Williams
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References
Abratis, M., Wörner, G. (2001) Ridge collision, slab-window formation, and the flux of Pacific asthenosphere into the Caribbean realm. Geology 29, 127–130. https://doi.org/10.1130/0091-7613(2001)029<0127:RCSWFA>2.0.CO;2
Show in context Here, the 13 to 15 Ma old Cocos and Coiba Ridge (CCR), and other hotspot traces related to the Galápagos plume, are being subducted along the Panama–Costa Rica section of the Central American arc system (Hauff et al., 2000; Abratis and Wörner, 2001; Gazel et al., 2009, 2011).
View in article
About 1.5 to 5 Ma old adakitic lavas from Panama and Costa Rica are of particular interest, since involvement of a slab melt component in their petrogenesis has previously been proposed (e.g., Defant et al., 1991; Abratis and Wörner, 2001; Gazel et al., 2009).
View in article
Further, a suite of alkaline mafic lavas (basanites) in the back-arc in Costa Rica dated at 4 to 6 Ma possibly record a mantle contribution from the Galápagos plume (Abratis and Wörner, 2001).
View in article
Further details on the samples as well as Sr, Pb and Nd isotope compositions can be found in Appel et al. (1994), Abratis and Wörner (2001) and Wegner et al. (2011).
View in article
We will now test whether partial melts of the subducted basalts from the CCR contributed to the μ182W deficits or, alternatively, the mantle wedge below Costa Rica and Panama contained material from the Galápagos plume, as was proposed for the origin of the basanites (Abratis and Wörner, 2001).
View in article
Following slab window formation below Costa Rica and Panama, previous models have argued for the ascent and decompression melting of a mantle component that was derived from the Galápagos plume as the source for the basanites (Abratis and Wörner, 2001; Gazel et al., 2011).
View in article
Appel, H., Wörner, G., Alvarado, G., Rundle, C., Kussmaul, S. (1994) Age relations in igneous rocks from Costa Rica. Profil 7, 63–69.
Show in context The latter were interpreted to represent 18 to 71 Ma old hotspot tracks of the Galápagos plume (e.g., Appel et al., 1994; Hauff et al., 2000; Wegner et al., 2011; Gazel et al., 2018).
View in article
Further details on the samples as well as Sr, Pb and Nd isotope compositions can be found in Appel et al. (1994), Abratis and Wörner (2001) and Wegner et al. (2011).
View in article
Arevalo Jr., R., McDonough, W.F. (2008) Tungsten geochemistry and implications for understanding the Earth’s interior. Earth and Planetary Science Letters 272, 656–665. https://doi.org/10.1016/j.epsl.2008.05.031
Show in context Bulk partition coefficients of W and Th are very similar during mantle melting (Arevalo and McDonough, 2008), resulting in only small variations of W/Th ratios in oceanic basalts (MORB = 0.09 to 0.24, OIB = 0.08 to 0.19; König et al., 2011; Kurzweil et al., 2019).
View in article
Bali, E., Keppler, H., Audetat, A. (2012) The mobility of W and Mo in subduction zone fluids and the Mo–W–Th–U systematics of island arc magmas. Earth and Planetary Science Letters 351–352, 195–207. https://doi.org/10.1016/j.epsl.2012.07.032
Show in context However, W is mobile in subduction zone fluids (Bali et al., 2012), resulting in elevated W/Th ratios in arc magmas compared to MORB and OIB (Fig. 1; König et al., 2008; Stubbs et al., 2022).
View in article
On the other hand, such low W/Th ratios could be due to melting of subducted basalts with residual rutile, where rutile preferentially retains W and other HFSE (Rudnick et al., 2000; Zack et al., 2002; Bali et al., 2012).
View in article
Bekaert, D.V., Gazel, E., Turner, S., Behn, M.D., de Moor, J.M., et al. (2021) High 3He/4He in central Panama reveals a distal connection to the Galápagos plume. Proceedings of the National Academy of Sciences 118, e2110997118. https://doi.org/10.1073/pnas.2110997118
Show in context It is therefore unlikely that this component reflects the composition of the modern central Galápagos domain (Bekaert et al., 2021).
View in article
Defant, M.J., Clark, L.F., Stewart, R.H., Drummond, M.S., de Boer, J.Z., Maury, R.C., Bellon, H., Jackson, T.E., Restrepo, J.F. (1991) Andesite and dacite genesis via contrasting processes: the geology and geochemistry of El Valle Volcano, Panama. Contributions to Mineralogy and Petrology 106, 309–324. https://doi.org/10.1007/BF00324560
Show in context About 1.5 to 5 Ma old adakitic lavas from Panama and Costa Rica are of particular interest, since involvement of a slab melt component in their petrogenesis has previously been proposed (e.g., Defant et al., 1991; Abratis and Wörner, 2001; Gazel et al., 2009).
View in article
Gale, A., Dalton, C.A., Langmuir, C.H., Su, Y., Schilling, J.-G. (2013) The mean composition of ocean ridge basalts. Geochemistry, Geophysics, Geosystems 14, 489–518. https://doi.org/10.1029/2012GC004334
Show in context Moreover, elevated Nb/Ta ratios in both adakites (18.01 ± 1.86) and basanites (20.1 ± 1.85) compared to typical values found in oceanic basalts (Nb/Ta = 14.5 to 16.5; Gale et al., 2013; Tang et al., 2019) are complementary to low Nb/Ta ratios in rutile (Green and Pearson, 1987).
View in article
Gazel, E., Carr, M.J., Hoernle, K., Feigenson, M.D., Szymanski, D., Hauff, F., van de Bogaard, P. (2009) Galapagos-OIB signature in southern Central America: Mantle refertilization by arc–hot spot interaction. Geochemistry, Geophysics, Geosystems 10, Q02S11. https://doi.org/10.1029/2008GC002246
Show in context Here, the 13 to 15 Ma old Cocos and Coiba Ridge (CCR), and other hotspot traces related to the Galápagos plume, are being subducted along the Panama–Costa Rica section of the Central American arc system (Hauff et al., 2000; Abratis and Wörner, 2001; Gazel et al., 2009, 2011).
View in article
About 1.5 to 5 Ma old adakitic lavas from Panama and Costa Rica are of particular interest, since involvement of a slab melt component in their petrogenesis has previously been proposed (e.g., Defant et al., 1991; Abratis and Wörner, 2001; Gazel et al., 2009).
View in article
Based on the large range of silica content, it was argued that the adakites in Costa Rica and Panama do not represent pure slab melts, but rather derive from a mantle wedge metasomatised by slab melts (Gazel et al., 2009, 2011; Martin et al., 2005).
View in article
This is in good agreement with previous models using radiogenic isotopes (Gazel et al., 2009).
View in article
Gazel, E., Hoernle, K., Carr, M.J., Herzberg, C., Saginor, I., van den Bogaard, P., Hauff, F., Feigenson, M., Swisher III, C. (2011) Plume–subduction interaction in southern Central America: Mantle upwelling and slab melting. Lithos 121, 117–134. https://doi.org/10.1016/j.lithos.2010.10.008
Show in context Here, the 13 to 15 Ma old Cocos and Coiba Ridge (CCR), and other hotspot traces related to the Galápagos plume, are being subducted along the Panama–Costa Rica section of the Central American arc system (Hauff et al., 2000; Abratis and Wörner, 2001; Gazel et al., 2009, 2011).
View in article
Based on the large range of silica content, it was argued that the adakites in Costa Rica and Panama do not represent pure slab melts, but rather derive from a mantle wedge metasomatised by slab melts (Gazel et al., 2009, 2011; Martin et al., 2005).
View in article
Following slab window formation below Costa Rica and Panama, previous models have argued for the ascent and decompression melting of a mantle component that was derived from the Galápagos plume as the source for the basanites (Abratis and Wörner, 2001; Gazel et al., 2011).
View in article
Gazel, E., Trela, J., Bizimis, M., Sobolev, A., Batanova, V., Class, C., Jicha, B. (2018) Long-Lived Source Heterogeneities in the Galapagos Mantle Plume. Geochemistry, Geophysics, Geosystems 19, 2764–2779. https://doi.org/10.1029/2017GC007338
Show in context This chemical zonation is also reflected in the CCR, as well as in the basaltic rocks accreted in the Central American forearc (Gazel et al., 2018 and references therein).
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The latter were interpreted to represent 18 to 71 Ma old hotspot tracks of the Galápagos plume (e.g., Appel et al., 1994; Hauff et al., 2000; Wegner et al., 2011; Gazel et al., 2018).
View in article
Green, T.H., Pearson, N.J. (1987) An experimental study of Nb and Ta partitioning between Ti-rich minerals and silicate liquids at high pressure and temperature. Geochimica et Cosmochimica Acta 51, 55–62. https://doi.org/10.1016/0016-7037(87)90006-8
Show in context Moreover, elevated Nb/Ta ratios in both adakites (18.01 ± 1.86) and basanites (20.1 ± 1.85) compared to typical values found in oceanic basalts (Nb/Ta = 14.5 to 16.5; Gale et al., 2013; Tang et al., 2019) are complementary to low Nb/Ta ratios in rutile (Green and Pearson, 1987).
View in article
Hauff, F., Hoernle, K., van den Bogaard, P., Alvarado, G., Garbe-Schönberg, D. (2000) Age and geochemistry of basaltic complexes in western Costa Rica: Contributions to the geotectonic evolution of Central America. Geochemistry, Geophysics, Geosystems 1, 1009. https://doi.org/10.1029/1999GC000020
Show in context Here, the 13 to 15 Ma old Cocos and Coiba Ridge (CCR), and other hotspot traces related to the Galápagos plume, are being subducted along the Panama–Costa Rica section of the Central American arc system (Hauff et al., 2000; Abratis and Wörner, 2001; Gazel et al., 2009, 2011).
View in article
The latter were interpreted to represent 18 to 71 Ma old hotspot tracks of the Galápagos plume (e.g., Appel et al., 1994; Hauff et al., 2000; Wegner et al., 2011; Gazel et al., 2018).
View in article
Hoernle, K., Werner, R., Morgan, J.P., Garbe-Schönberg, D., Bryce, J., Mrazek, J. (2000) Existence of complex spatial zonation in the Galápagos plume. Geology 28, 435–438. https://doi.org/10.1130/0091-7613(2000)28<435:EOCSZI>2.0.CO;2
Show in context A chemical and isotopic zonation within the Galápagos plume (Hoernle et al., 2000) is mirrored by contrasting negative W isotopic compositions of basalts from the central and eastern domains of the Galápagos islands (μ182W = −22 and −5, respectively; Mundl-Petermeier et al., 2020).
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König, S., Münker, C., Schuth, S., Garbe-Schönberg, D. (2008) Mobility of tungsten in subduction zones. Earth and Planetary Science Letters 274, 82–92. https://doi.org/10.1016/j.epsl.2008.07.002
Show in context The geochemical behaviour of W in subduction zones is best studied using W/Th ratios (König et al., 2008).
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However, W is mobile in subduction zone fluids (Bali et al., 2012), resulting in elevated W/Th ratios in arc magmas compared to MORB and OIB (Fig. 1; König et al., 2008; Stubbs et al., 2022).
View in article
König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
Show in context Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011), Kurzweil et al. (2019), Mazza et al. (2020), and Stubbs et al. (2022).
View in article
MORB and OIB fields defined after König et al. (2011) and Kurzweil et al. (2019).
View in article
Bulk partition coefficients of W and Th are very similar during mantle melting (Arevalo and McDonough, 2008), resulting in only small variations of W/Th ratios in oceanic basalts (MORB = 0.09 to 0.24, OIB = 0.08 to 0.19; König et al., 2011; Kurzweil et al., 2019).
View in article
Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
Show in context Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011), Kurzweil et al. (2019), Mazza et al. (2020), and Stubbs et al. (2022).
View in article
MORB and OIB fields defined after König et al. (2011) and Kurzweil et al. (2019).
View in article
Bulk partition coefficients of W and Th are very similar during mantle melting (Arevalo and McDonough, 2008), resulting in only small variations of W/Th ratios in oceanic basalts (MORB = 0.09 to 0.24, OIB = 0.08 to 0.19; König et al., 2011; Kurzweil et al., 2019).
View in article
Laeger, K., Halama, R., Hansteen, T., Savov, I.P., Murcia, H.F., Cortés, G.P., Garbe-Schönberg, D. (2013) Crystallization conditions and petrogenesis of the lava dome from the ∼900 years BP eruption of Cerro Machín Volcano, Colombia. Journal of South American Earth Sciences 48, 193–208. https://doi.org/10.1016/j.jsames.2013.09.009
Show in context Adakitic rocks from Laeger et al. (2013) and Straub et al. (2015).
View in article
Martin, H., Smithies, R.H., Rapp, R., Moyen, J.-F., Champion, D. (2005) An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution. Lithos 79, 1–24. https://doi.org/10.1016/j.lithos.2004.04.048
Show in context They feature prominent depletions in high field strength elements (HFSE) and are low in heavy rare earth elements (HREE) due to melting of hydrous meta-basalt with residual rutile and garnet (Figure S-1; Martin et al., 2005).
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Although their Sr/Y ratios are elevated compared to normal arc lava and range between 42 and 120, they also have high Y concentrations (17.5 to 30 μg/g) and are silica-undersaturated, which places them outside the compositional range expected for adakitic rocks (Martin et al., 2005).
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Based on the large range of silica content, it was argued that the adakites in Costa Rica and Panama do not represent pure slab melts, but rather derive from a mantle wedge metasomatised by slab melts (Gazel et al., 2009, 2011; Martin et al., 2005).
View in article
Mazza, S.E., Stracke, A., Gill, J.B., Kimura, J.-I., Kleine, T. (2020) Tracing dehydration and melting of the subducted slab with tungsten isotopes in arc lavas. Earth and Planetary Science Letters 530, 115942. https://doi.org/10.1016/j.epsl.2019.115942
Show in context Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011), Kurzweil et al. (2019), Mazza et al. (2020), and Stubbs et al. (2022).
View in article
Mundl-Petermeier, A., Walker, R.J., Fischer, R.A., Lekic, V., Jackson, M.G., Kurz, M.D. (2020) Anomalous 182W in high 3He/4He ocean island basalts: Fingerprints of Earth’s core? Geochimica et Cosmochimica Acta 271, 194–211. https://doi.org/10.1016/j.gca.2019.12.020
Show in context The only known modern setting exhibiting negative 182W variability is ocean islands associated with deep-seated mantle plumes, such as Galápagos (e.g., Mundl-Petermeier et al., 2020).
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A chemical and isotopic zonation within the Galápagos plume (Hoernle et al., 2000) is mirrored by contrasting negative W isotopic compositions of basalts from the central and eastern domains of the Galápagos islands (μ182W = −22 and −5, respectively; Mundl-Petermeier et al., 2020).
View in article
Rudnick, R.L., Barth, M., Horn, I., McDonough, W.F. (2000) Rutile-Bearing Refractory Eclogites: Missing Link Between Continents and Depleted Mantle. Science 287, 278–281. https://doi.org/10.1126/science.287.5451.278
Show in context On the other hand, such low W/Th ratios could be due to melting of subducted basalts with residual rutile, where rutile preferentially retains W and other HFSE (Rudnick et al., 2000; Zack et al., 2002; Bali et al., 2012).
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Straub, S.M., Gómez-Tuena, A., Bindeman, I.N., Bolge, L.L., Brandl, P.A., et al. (2015) Crustal recycling by subduction erosion in the central Mexican Volcanic Belt. Geochimica et Cosmochimica Acta 166, 29–52. https://doi.org/10.1016/j.gca.2015.06.001
Show in context Adakitic rocks from Laeger et al. (2013) and Straub et al. (2015).
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Stubbs, D., Yang, R., Coath, C.D., John, T., Elliott, T. (2022) Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids. Geochimica et Cosmochimica Acta 334, 135–154. https://doi.org/10.1016/j.gca.2022.08.005
Show in context Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011), Kurzweil et al. (2019), Mazza et al. (2020), and Stubbs et al. (2022).
View in article
However, W is mobile in subduction zone fluids (Bali et al., 2012), resulting in elevated W/Th ratios in arc magmas compared to MORB and OIB (Fig. 1; König et al., 2008; Stubbs et al., 2022).
View in article
These also record high Ba/Th ratios of >280 or high 87Sr/86Sr ratios of >0.704, in line with additional fluid or sedimentary components in their source (Fig. 1, Table S-1; Stubbs et al., 2022).
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Tang, M., Lee, C.-T.A., Chen, K., Erdman, M., Costin, G., Jiang, H. (2019) Nb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation. Nature Communications 10, 235. https://doi.org/10.1038/s41467-018-08198-3
Show in context Moreover, elevated Nb/Ta ratios in both adakites (18.01 ± 1.86) and basanites (20.1 ± 1.85) compared to typical values found in oceanic basalts (Nb/Ta = 14.5 to 16.5; Gale et al., 2013; Tang et al., 2019) are complementary to low Nb/Ta ratios in rutile (Green and Pearson, 1987).
View in article
Tera, F., Brown, L., Morris, J., Sacks, I.S., Klein, J., Middleton, R. (1986) Sediment incorporation in island-arc magmas: Inferences from 10Be. Geochimica et Cosmochimica Acta 50, 535–550. https://doi.org/10.1016/0016-7037(86)90103-1
Show in context While there is strong evidence for the involvement of fluids and subducted sediments in the mantle source of many arc magmas (Tera et al., 1986), the nature of direct contributions of subducted basaltic crust remains debated.
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Wegner, W., Wörner, G., Harmon, R.S., Jicha, B.R. (2011) Magmatic history and evolution of the Central American Land Bridge in Panama since Cretaceous times. Bulletin of the Geological Society of America 123, 703–724. https://doi.org/10.1130/B30109.1
Show in context The latter were interpreted to represent 18 to 71 Ma old hotspot tracks of the Galápagos plume (e.g., Appel et al., 1994; Hauff et al., 2000; Wegner et al., 2011; Gazel et al., 2018).
View in article
Further details on the samples as well as Sr, Pb and Nd isotope compositions can be found in Appel et al. (1994), Abratis and Wörner (2001) and Wegner et al. (2011).
View in article
Willbold, M., Elliott, T., Moorbath, S. (2011) The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature 477, 195–198. https://doi.org/10.1038/nature10399
Show in context Variations in the distribution of 182W in terrestrial rocks must have been established within the first 50 Myr of Earth’s history due to the short half-life of its extinct parent isotope 182Hf (e.g., Willbold et al., 2011).
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Yogodzinski, G.M., Brown, S.T., Kelemen, P.B., Vervoort, J.D., Portnyagin, M., Sims, K.W.W., Hoernle, K., Jicha, B.R., Werner, R. (2015) The Role of Subducted Basalt in the Source of Island Arc Magmas: Evidence from Seafloor Lavas of the Western Aleutians. Journal of Petrology 56, 441–492. https://doi.org/10.1093/petrology/egv006
Show in context However, slab melting under certain conditions has become central to many models of subduction zone processes (e.g., Yogodzinski et al., 2015).
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Zack, T., Kronz, A., Foley, S.F., Rivers, T. (2002) Trace element abundances in rutiles from eclogites and associated garnet mica schists. Chemical Geology 184, 97–122. https://doi.org/10.1016/S0009-2541(01)00357-6
Show in context On the other hand, such low W/Th ratios could be due to melting of subducted basalts with residual rutile, where rutile preferentially retains W and other HFSE (Rudnick et al., 2000; Zack et al., 2002; Bali et al., 2012).
View in article
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Supplementary Information
The Supplementary Information includes:
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Figures
Figure 1 Fluid mobile element systematics for Panama and Costa Rica arc rocks and compiled arc data from König et al. (2011)
König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
, Kurzweil et al. (2019Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
), Mazza et al. (2020)Mazza, S.E., Stracke, A., Gill, J.B., Kimura, J.-I., Kleine, T. (2020) Tracing dehydration and melting of the subducted slab with tungsten isotopes in arc lavas. Earth and Planetary Science Letters 530, 115942. https://doi.org/10.1016/j.epsl.2019.115942
, and Stubbs et al. (2022)Stubbs, D., Yang, R., Coath, C.D., John, T., Elliott, T. (2022) Tungsten isotopic fractionation at the Mariana arc and constraints on the redox conditions of subduction zone fluids. Geochimica et Cosmochimica Acta 334, 135–154. https://doi.org/10.1016/j.gca.2022.08.005
. MORB and OIB fields defined after König et al. (2011)König, S., Münker, C., Hohl, S., Paulick, H., Barth, A.R., Lagos, M., Pfänder, J., Büchl, A. (2011) The Earth’s tungsten budget during mantle melting and crust formation. Geochimica et Cosmochimica Acta 75, 2119–2136. https://doi.org/10.1016/j.gca.2011.01.031
and Kurzweil et al. (2019)Kurzweil, F., Münker, C., Grupp, M., Braukmüller, N., Fechtner, L., Christian, M., Hohl, S.V., Schoenberg, R. (2019) The stable tungsten isotope composition of modern igneous reservoirs. Geochimica et Cosmochimica Acta 251, 176–191. https://doi.org/10.1016/j.gca.2019.02.025
. Adakitic rocks from Laeger et al. (2013)Laeger, K., Halama, R., Hansteen, T., Savov, I.P., Murcia, H.F., Cortés, G.P., Garbe-Schönberg, D. (2013) Crystallization conditions and petrogenesis of the lava dome from the ∼900 years BP eruption of Cerro Machín Volcano, Colombia. Journal of South American Earth Sciences 48, 193–208. https://doi.org/10.1016/j.jsames.2013.09.009
and Straub et al. (2015)Straub, S.M., Gómez-Tuena, A., Bindeman, I.N., Bolge, L.L., Brandl, P.A., et al. (2015) Crustal recycling by subduction erosion in the central Mexican Volcanic Belt. Geochimica et Cosmochimica Acta 166, 29–52. https://doi.org/10.1016/j.gca.2015.06.001
.
Figure 2 Two component mixing models for melts derived from a depleted mantle or an enriched mantle modified by Cocos and Coiba Ridge (CCR) melts. Endmember compositions and model parameters can be found in the Supplementary Information. Samples with W/Th > 0.2 not shown.
Figure 3 Two component mixing models between modelled slab melt and three different mantle compositions: (a) mixing with depleted mantle to model the W isotope composition of adakites and (b) mixing with two types of enriched mantle (models A and B) to produce the source composition of basanites. Grey dashed lines represent the error of the W isotopic composition of the upper mantle. Model parameters can be found in the Supplementary Information.