Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (<50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (<1000°C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite–Tonalite–Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.
References
1.
TatsumiY, & EgginsS. (1995). Subduction zone magmatism. Frontiers in Earth Sciences, Blackwell Science, pp. 205.
2.
SchmidtM., & PoliS. (1998) Experimentally based water budget for dehydrating slabs and consequences for arc magma generation, Earth Planet. Sci. Lett.163, 361–379.
3.
GreenT.H., & RingwoodA.E. (1968) Genesis of calcalkaline igneous rock suite. Contrib. Mineral. Petrol., 18, 105–162.
4.
MartinH., (1986) Effect of steeper Archean geothermal gradient on geochemistry of subduction zone magmas, Geology14, 753–756.
5.
DefantM.J., & DrummondM.S. (1990) Derivation of some modern arc magmas by melting of young subducted lithosphere, Nature347, 662–665.
6.
GillJ.B. (1981) Orogenic andesites and plate tectonics.New York, Springer Verlag, 390 p.
7.
TatsumiY. (1982) Origin of high-magnesian andesites in the Setouchi volcanic belt, southwest Japan, II. Melting phase relations at high pressures. Earth Planet. Sci. Lett., 60, 305–317.
8.
CoatsR.R. (1962) Magma type and crustal structure in the Aleutian arc. In Crust of the Pacific basin. Geophys. Mon. Am Geophys. Union, 6, 92–109.
9.
BrophyJ.G., & MarshB.D. (1986) On the origin of high alumina arc basalts and the mechanics of melt extraction. J. Petrol., 27, 763–789.
10.
JohnstonA.D. (1986) Anhydrous P-T relations of near-primary high alumina basalt from the South Sandwich Islands. Implications for the origin of island arcs and tonalite trondhjemite series rocks. Contrib. Mineral. Petrol., 92, 368–382.
KayR. W. (1978) Aleutian magnesian andesites: melt from subducted Pacific ocean crust. J. Volc. Geotherm. Res., 4, 117–132
13.
RyersonF.J., & WatsonE.B. (1987) Rutile saturation in magmas: implications for Ti-Nb-Ta depletion in island-arc basalts, Earth Planet. Sci. Lett.86, 225–239.
14.
JuteauT., & MauryR. (1998). Géologie de la croûte océanique. Pétrologie et dynamique endogène. Masson, Paris, 367 p.
15.
ScailletB., & EvansB.W. (1999) The June 15, 1991 eruption of Mount Pinatubo. Phase equilibria and pre-eruption conditions P-T-fO2-fH2O of the dacite magma. J. Petrol., 40, 381–411.
16.
ClemensJ.D., & WatkinsJ.M. (2001) The fluid regime of high-temperature metamorphism during granitoid magma genesis. Contrib. Mineral. Petrol., 140, 600–606.
17.
RappR.P., & WatsonE.B. (1995) Dehydration melting of metabasalt at 8-32 kbar: implications for continental growth and crust-mantle recycling, J. Petrol.36, 891–931.
18.
SenC., & DunnT.(1994) Dehydration melting of a basaltic composition amphibolite at 1.5 and 2.0 GPa: implications for the origin of adakites, Contrib. Mineral. Petrol.117, 394–409.
19.
ProuteauG., ScailletB., PichavantM., & MauryR.C. (1999) Fluid-present melting of ocean crust in subduction zones, Geology27, 1111–1114.
20.
ProuteauG., ScailletB., PichavantM., & MauryR.C. (2001) Evidence for mantle metasomatism of hydrous silicic melts derived from subucted oceanic crust. Nature, 410, 197–200.
21.
SorensenS.S., & GrossmanJ.N. (1989) Enrichment of trace elements in garnet amphibolites from a paleo-subduction zone: Catalina Schist, southern California, Geochim. Cosmochim. Acta53, 3155–3177.
22.
KepezhinskasP.K., DefantM.J., & DrummondM.S. (1995) Na metasomatism in the island-arc mantle by slab melt-peridotite interaction: evidence from mantle xenoliths in the north Kamchatka arc, J. Petrol.36, 1505–1527.
23.
SchianoP., ClocchiattiR., ShimizuN., MauryR.C., JochumK.P., & HofmannA. (1995) Hydrous, silica-rich melts in the sub-arc mantle and their relationship with erupted arc-lavas, Nature377, 595–600.
24.
SekineT., & WyllieP.J. (1983) Experimental simulation of mantle hybridization in subduction zones. J. Geol., 91, 511–528.
25.
CarrollM.J., & WyllieP.J. (1989) Experimental phase relations in the system peridotite-tonalite-H2O at 15 kbar: implications for assimilation and differentiation processes at the crust-mantle boundary, J. Petrol.30, 1351–1382.
26.
KelemenP. (1995) Genesis of high Mg# andesites and the continental crust. Contrib. Mineral. Petrol., 120, 1–19.
27.
SenC., & DunnT. (1994) Experimental modal metasomatism of a spinel lherzolite and the production of amphibole-bearing peridotite. Contrib. Mineral. Petrol., 119, 422–432.
28.
HirschmannM.M., BakerM.B., & StolperE.M. (1998) The effect of alkalis on the silica content of mantle-derived melts, Geochim. Cosmochim. Acta62, 883–902.
29.
YogodzinskyG.M., & KelemenP. (1998) Slab melting in the Aleutians: implications of an ion probe study on clinopyroxene in primitive adakite and basalt. Earth Planet. Sci. Lett., 158, 53–65.
30.
YogodinzskiG.M., VolynetsO.N., KoloskovA.V., SeliverstovN.I. (1994) Magnesian andesites and the subduction component in a strongly calcalkaline series at Piip volcano, far western Aleutian, J. Petrol.34, 163–204.
31.
MartinH. (1994) The Archean grey gneisses and the genesis of continental crust. In Archean crustal evolution, CondieK. (ed.). Amsterdam, Elsevier, 205–259.
32.
SmithiesR.H. (2000) The Archaean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite. Earth Planet. Sci. Lett., 182, 115–125.
33.
AthertonM.P., & PetfordN. (1993) Generation of sodium-rich magmas from newly underplated basaltic crust, Nature362, 144–146
34.
SmithiesR.H., & ChampionD.C. (2000) The Archaean high-Mg diorite suite: links to tonalite-trondhjemite-granodiorite magmatism and implications for early Archaean crustal growth. J. Petrol., 41, 1653–1671.
35.
ZanettiA., Mazzucchelli, RivalentiG., & VannucciR. (1999) The Finero phlogopite-peridotite massif: an example of subduction-related metasomatism, Contrib. Mineral. Petrol.134, 107–122.
36.
BureauH., & KepplerH. (1999) Complete miscibility between silicate melts and hydrous fluids in the upper mantle: experimental evidence and geochemical implications. Earth Planet. Sci. Lett., 165, 187–196.
