Constraints on the origin of Archean trondhjemites based on phase relationships of Nûk gneiss with H2O at 15 kbar
Tóm tắt
We report the T-X(H2O) phase relations for the trondhjemitic Nûk gneiss which comprises the principal component of the second phase of Archean (3.0–2.8 by) igneous activity in the Godthåb region of southwestern Greenland. A pressure of 15 kbar was chosen to place constraints on possible protoliths for trondhjemitic melts at lower crustal depths. Under H2O-saturated conditions, a melting interval of ∼135° C separates the solidus at ∼610° C from the liquidus at 745° C. H2O-saturation at 15 kbar occurs at approximately 15.5 wt % H2O. The H2O-undersaturated liquidus extends along a curved path from ∼745° C at 15.5 wt % H2O to ∼1100° C at 2% H2O. Lower H2O contents were not investigated. At low H2O contents (<6%) sodic plagioclase (Pl, An32) is the liquidus phase followed at lower but still near-liquidus temperatures by quartz (Qz) and then garnet (Ga). At 6% H2O, Ga replaces Pl on the liquidus and is joined at slightly lower temperatures by Pl and hornblende (Hb). The field for liquidus Ga extends to only ∼7.5% H2O where it is replaced by Hb which is the liquidus phase up to 13% H2O. At all higher H2O contents, epidote (Ep) is the first phase to crystallize, followed by biotite (Bi) at slightly lower temperatures. Following the standard inverse approach, the near-liquidus phase assemblages are interpreted as potential residues from which trondhjemitic melts could be extracted. At high melt H2O contents (>7%), mafic residues consisting of some combination of Hb, Ga, Ep, and Bi are possible and could correspond to amphibolitic source rocks. At lower melt H2O contents (< 5%), possible residues consist of Na-Pl+Qz±Ga and could correspond to an earlier generation of tonalitic-trondhjemitic rocks. However, such residues would not impart the highly fractionated REE patterns characteristic of Archean trondhjemites. If a first generation of tonalitic-trondhjemitic melts was generated by higher pressure partial fusion of eclogite and emplaced at 55 km depth, it would crystallize to an assemblage consisting almost entirely of Na-Pl+Qz with highly fractionated REE patterns. These rocks in turn could be partially melted to yield a second generation of trondhjemites which would inherit the highly fractionated REE patterns because neigher Pl nor Qz is capable of significantly fractionating HREE from LREE.
Tài liệu tham khảo
Allen JC, Boettcher AL (1978) Amphiboles in andesite and basalt: II. Stability as a function of 45-01. Amer Miner 63:1074–1087
Allen JC, Boettcher AL (1983) The stability of amphibole in andesite and basalt at high pressures. Amer Miner 68:307–314
Allen JC, Boettcher AL, Marland G (1975) Amphiboles in andesite and basalt: I. Stability as a function of 45-02. Amer Miner 60:1069–1085
Arth JG, Barker F (1976) Rare-earth partitioning between horn-blende and dacitic liquid and implications for the genesis of trondhjemitic-tonalitic magmas. Geology 4:534–536
Arth JG, Hanson GN (1972) Quartz diorite derived by partial melting of eclogite or amphibolite at mantle depths. Contrib Mineral Petrol 37:161–174
Arth JG, Barker F, Peterman ZE, Friedman E (1978) Geochemistry of the gabbro-diorite-tonalite-trondhjemite suite of south-west Finland and its implications for the origin of tonalite and trondhjemite magmas. J Petrol 19:289–316
Barker F (1979) Trondhjemite: Definition, environment and hypotheses of origin. In: F Barker (ed) Trondhjemites, dacites and related rocks, Elsevier, Amsterdam Oxford New York, 659 p
Barker F, Arth JG (1976) Generation of trondhjemitic-tonalitic liquids and Archean bimodal trondhjemite-basalt series. Geology 4:596–600
Basaltic Volcanism Study Project (1981) Basaltic volcanism on the terrestrial planets. Pergamon, New York, 1286 p
Bence AE, Albee AL (1968) Correction factors for electron probe microanalysis of silicates and oxides. J Geol 76:382–403
Boettcher AL, Wyllie PJ (1968) The quartz-coesite transition measured in the presence of a silicate liquid and calibration of piston-cylinder apparatus. Contrib Mineral Petrol 17:224–232
Boyd FR, England JL (1960) Apparatus for phase-equilibrium measurements at pressures to 50 kilobars and temperatures up to 1750° C. J Geophys Res 65:741–748
Boyd FR, Bell PM, England JL, Gilbert MC (1967) Pressure measurement in single-stage apparatus. Carnegie Inst Wash Yrbk 65:410–414
Bridgewater D, Keto L, McGregor VR, Myers JS (1976) Archaean gneiss complex of Greenland. In: A Escher, WS Watt (eds) Geology of Greenland. Geol Survey of Greenland, 603 p
Compton P (1978) Rare earth evidence for the origin of the Nûk gneisses, Budsefjorden region, southern West Greenland. Contrib Mineral Petrol 66:283–294
Condie KC, Hunter DR (1976) Trace element geochemistry of Archean granitic rocks from the Barberton region, South Africa. Earth Planet Sci Lett 29:389–400
Deer WA, Howie RA, Zussman J (1962) Rock forming minerals, Vol 1, Ortho-and ring silicates. Longmans, London, 333 p
Drummond MS, Ragland PC, Wesolowski D (1986) An example of trondhjemite genesis by means of alkali metasomatism: Rockford granite, Alabama Appalachians. Contrib Mineral Petrol 93:98–113
Evans BW, Vance JA (1987) Epidote phenocrysts in dacitic dikes, Boulder County, Colorado. Contrib Mineral Petrol 96:178–185
Glickson AY (1979) Early Proterozoic tonalite-trondhjemite sialic nuclei. Earth Planet Sci Lett 15:1–73
Green DH (1976) Experimental testing of “equilibrium” partial melting of peridotite under water-saturated, high-pressure conditions. Can Mineral 14:255–268
Green TH (1980) Island-arc and continent-building magmatism — A review of petrogenetic models based on experimental petrology and geochemistry. Tectonophys 63:367–385
Green TH, Ringwood AE (1968) Genesis of the calc-alkaline igneous rock suite. Contrib Mineral Petrol 18:105–162
Helz RT (1976) Phase relations of basalts in their melting ranges at45-03.Part II. Melt compositions. J Petrol 17:139–193
Hess PC, Rutherford MJ, Guillemette RN, Ryerson FJ, Tuchfield TA (1975) Residual products of fractional crystallization of lunar magmas: An experimental study. Proc Lunar Sci Conf 6th, pp 895–909
Hickling HL, Phair G, Moore R, Rose HJ (1970) Boulder Crrek batholith, Colorado. Part I. Allanite and its bearing upon age patterns. Geol Soc Amer Bull 81:1973–1994
Hollister LS, Grissom GC, Peters EK, Stowell HH, Sisson VB (1987) Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons. Amer Miner 72:231–239
Holloway JR, Burnham CW (1972) Melting relations of basalt with equilibrium water pressure less than total pressure. J Petrol 13:1–29
Huang W-L, Wyllie PJ (1981) Phase relationships of S-type granite with H2O to 35 kbar: Muscovite granite from Harney Peak, South Dakota. J Geophys Res 86:1015–1029
Huang W-L, Wyllie PJ (1986) Phase relationships of gabbro-tonalite-granite-water at 15 kbar with applications to differentiation and anatexis. Amer Miner 71:301–316
Hunter DR, Barker F, Millard HT (1978) The geochemical nature of the Archean ancient gneiss complex and granodiorite suite, Swaziland: A preliminary study. Precambrian Res 7:105–127
Jacques AL, Green DH (1979) Determination of liquid compositions in high-pressure melting of peridotite. Amer Mineral 64:1312–1321
Jahn BM, Glikson AY, Pencat JJ, Hickman AH (1981) REE geochemistry and isotopic data of Archean silicic volcanics and granitoids from the Pilbara Block, Western Australia: Implications for the early crustal evolution. Geochim Cosmochim Acta 45:1633–1652
Jahn BM, Vidal P, Kroner A (1984) Multichronometric ages and origin of Archean tonalitic gneisses in Finnish Lapland: A case for long crustal residence time. Contrib Mineral Petrol 86:398–408
Johnston AD (1986) Anhydrous P-T phase 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
Kawakami SI, Mizutani H (1984) Geology and geochemistry of Archean crust and implications for the early history of the Earth. J Earth Sci Nagoya Univ 32:49–94
Lee DE, Mays RE, Van Loenen RE, Rose HJ (1971) Accessory epidote from hybrid granite rocks of the Mt. Wheeler Mine area, Nevada. US Geol Survey Prof Paper 750-C:112–116
McGregor VR (1979) Archean grey gneisses and the origin of the continental crust: Evidence from the Godthåb region, West Greenland, In: F Barker (ed) Trondhjemites, dacites and related rocks. Elsevier, Amsterdam Oxford New York, 659 p
Moorbath S (1977) Ages, isotopes and evolution of Precambrian continental crust. Chem Geol 20:151–187
Mysen BO, Boettcher AL (1975) Melting of a hydrous mantle II: Geochemistry of crystals and liquids formed by anatexis of mantle peridotite at high pressures and temperatures as a function of controlled activities of water, hydrogen, and carbon dioxide. J Petrol 16:549–593
Naney MT (1983) Phase equilibria of rock forming ferromagnesian silicates in granitic systems. Amer J Sci 283:993–1033
Nicholls IA, Ringwood AE (1973) Effect of water on olivine stability in tholeiites and the production of silica-saturated magmas in the island arc environment. J Geol 81:285–300
O'Nions RK, Pankhurst RJ (1974) Rare earth element distribution in Archean gneisses and anorthosites, Godthåb area, West Greenland. Earth Planet Sci Lett 22:328–338
Robertson JK, Wyllie PJ (1971) Rock-water systems, with special reference to the water-deficient region. Amer J Sci 271:252–277
Rutter MJ, Wyllie PJ (1987) Melting of tonalite and the origin of crustal granites. Trans Am Geophys Union 68:441
Shirey SB, Hanson GN (1984) Mantle-derived Archean monzodiorites and trachyandesites. Nature 310:222–224
Spulber SD, Rutherford MJ (1983) The origin of rhyolite and plagiogranite in oceanic crust: An experimental study. J Petrol 24:1–25
Stern CR, Huang WL, Wyllie PJ (1975) Basalt-andesite-rhyolite-H2O: Crystallization intervals with excess H2O and H2O-undersaturated liquidus surfaces to 35 kilobars, with implications for magma genesis. Earth Planet Sci Lett 28:189–196
Tulloch AJ (1979) Secondary Ca-Al silicates as low-grade alteration products of granitoid biotite. Contrib Mineral Petrol 69:105–117
Tulloch AJ (1986) Comments on “Implications of magmatic epidote-bearing plutons on crustal evolution in the accreted terranes of northwestern North America” and “Magmatic epidote and its petrological significance”. Geology 14:186–187
Whitney JA (1975) The effects of pressure, temperature, and X(H2O) on phase assemblages in four synthetic rock compositions. J Geol 83:1–31
Wyllie PJ (1979) Magmas and volatile components. Amer Miner 64:469–500
Wyllie PJ (1982) Subduction products according to experimental prediction. Geol Soc Amer Bull 93:468–476
Wyllie PJ (1984) Constraints imposed by experimental petrology on possible and impossible magma sources and products. Phil Trans R Soc London A-310:439–456
Wyllie PJ, Donaldson CH, Irving AJ, Kesson SE, Merrill RB, Presnall DC, Stolper EM, Usselman TM, Walker D (1981) Experimental petrology of basalts and their source rocks. Chapter 3 in Basaltic Volcanism on the Terrestrial Planets. Pergamon, New York
Zen E, Hammarstrom JM (1984) Magmatic epidote and its petrological significance. Geology 12:515–518