Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12―200 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12 h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12―200 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12 h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.

[1]  C. Porcher,et al.  Experimental melting of cordierite gneiss and the petrogenesis of syntranscurrent peraluminous granites in southern Brazil , 2002 .

[2]  Xiaosong Yang,et al.  Genesis of granulite in Himalayan lower crust: Evidence from experimental study at high temperature and high pressure , 2002 .

[3]  Xiaosong Yang,et al.  Experimental study on dehydration melting of natural biotite-plagioclase gneiss from High Himalayas and implications for Himalayan crust anatexis , 2001 .

[4]  E. Sawyer.  Melt segregation in the continental crust: distribution and movement of melt in anatectic rocks , 2001 .

[5]  Carlos Segovia Fernández,et al.  Experimental Constraints on Hercynian Anatexis in the Iberian Massif, Spain , 2000 .

[6]  S. Wickham,et al.  Silicic Magma Formation in Overthickened Crust: Melting of Charnockite and Leucogranite at 15, 20 and 25 kbar , 2000 .

[7]  J. De la Rosa,et al.  Origin of peraluminous granites and granodiorites, Iberian massif, Spain: an experimental test of granite petrogenesis , 1999 .

[8]  Jie Guo,et al.  Experimental studies on silicate structures of basaltic glasses quenched at 1 65093 and 1–3.5 GPa , 1999 .

[9]  E. Watson,et al.  Low melt fraction connectivity of granitic and tonalitic melts in a mafic crustal rock at 800 °C and 1 GPa , 1999 .

[10]  E. Sawyer.  Formation and Evolution of Granite Magmas During Crustal Reworking: the Significance of Diatexites , 1998 .

[11]  N. Harris,et al.  Experimental Constraints on Himalayan Anatexis , 1998 .

[12]  Fulai Liu,et al.  Genetic relationship of metamorphic reaction and dehydration-melting , 1998 .

[13]  X. Pichon,et al.  Uplift of Tibet: from eclogites to granulites — implications for the Andean Plateau and the Variscan belt , 1997 .

[14]  Jagtar Singh,et al.  Dehydration melting of tonalites. Part II. Composition of melts and solids , 1996 .

[15]  K. Winther.  An experimentally based model for the origin of tonalitic and trondhjemitic melts , 1996 .

[16]  E. Watson,et al.  Experimental and theoretical constraints on melt distribution in crustal sources: the effect of crystalline anisotropy on melt interconnectivity , 1995 .

[17]  R. Rapp.  Amphibole-out phase boundary in partially melted metabasalt, its control over liquid fraction and composition, and source permeability , 1995 .

[18]  P. Wyllie,et al.  Liquid segregation parameters from amphibolite dehydration melting experiments , 1995 .

[19]  E. Sawyer,et al.  Introduction to Special Section: Mechanisms and Consequences of Melt Segregation From Crustal Protoliths , 1995 .

[20]  V. Gardien,et al.  Experimental melting of biotite + plagioclase + quartz ± muscovite assemblages and implications for crustal melting , 1995 .

[21]  E. Watson,et al.  Dehydration melting of metabasalt at 8-32 kbar : Implications for continental growth and crust-mantle recycling , 1995 .

[22]  J. Beard,et al.  Dehydration-melting of Biotite Gneiss and Quartz Amphibolite from 3 to 15 kbar , 1995 .

[23]  A. P. Douce,et al.  H2O loss from hydrous melts during fluid-absent piston cylinder experiments , 1994 .

[24]  M. Brown,et al.  The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens , 1994 .

[25]  P. Wyllie,et al.  Dehydration-melting of amphibolite at 10 kbar: the effects of temperature and time , 1994 .

[26]  Hongru Zhao,et al.  Measurements of ultrasonic wave velocities at high temperature and high pressure for window glass, pyrophyllite, and kimberlite up to 1400°C and 5.5 GPa , 1994 .

[27]  P. Wyllie,et al.  Garnet Growth during Amphibolite Anatexis: Implications of a Garnetiferous Restite , 1993, The Journal of Geology.

[28]  P. Wyllie,et al.  Dehydration-melting of solid amphibolite at 10 kbar: Textural development, liquid interconnectivity and applications to the segregation of magmas , 1991 .

[29]  E. Watson,et al.  Partial melting of amphibolite/eclogite and the origin of Archean trondhjemites and tonalites , 1991 .

[30]  G. Lofgren,et al.  Dehydration Melting and Water-Saturated Melting of Basaltic and Andesitic Greenstones and Amphibolites at 1, 3, and 6. 9 kb , 1991 .

[31]  T. Rushmer.  Partial melting of two amphibolites: contrasting experimental results under fluid-absent conditions , 1991 .

[32]  B. Hacker.  Amphibolite-facies-to-granulite-facies reactions in experimentally deformed, unpowdered amphibolite , 1990 .

[33]  J. Puziewicz,et al.  Experimental study of a biotite-bearing granitic system under water-saturated and water-undersaturated conditions , 1990 .

[34]  W. Johannes.  What controls partial melting in migmatites , 1988 .

[35]  A. Thompson,et al.  Fluid-absent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis , 1988 .

[36]  M. Rutter,et al.  Melting of vapour-absent tonalite at 10 kbar to simulate dehydration–melting in the deep crust , 1988, Nature.

[37]  S. Wickham.  The segregation and emplacement of granitic magmas , 1987, Journal of the Geological Society.

[38]  A. Thompson,et al.  Subsolidus and Partial Melting Reactions in the Quartz-excess CaO+MgO+Al2O3+SiO2+H2O System under Water-excess and Water-deficient Conditions to 10 kb: Some Implications for the Origin of Peraluminous Melts from Mafic Rocks , 1986 .

[39]  Raymond Jeanloz,et al.  Temperature distribution in the crust and mantle , 1986 .

[40]  D. McKenzie,et al.  The Generation and Compaction of Partially Molten Rock , 1984 .

[41]  J. Percival.  High-grade metamorphism in the Chapleau-Foleyet area, Ontario , 1983 .

[42]  A. Thompson.  Dehydration melting of pelitic rocks and the generation of H 2 O-undersaturated granitic liquids , 1982 .

[43]  F. Barker.  Trondhjemite: Definition, Environment and Hypotheses of Origin , 1979 .

[44]  H. R. Shaw.  Viscosities of magmatic silicate liquids; an empirical method of prediction , 1972 .

[45]  I. Lambert,et al.  Melting of Gabbro (Quartz Eclogite) with Excess Water to 35 Kilobars, with Geological Applications , 1972, The Journal of Geology.

[46]  J. Holloway,et al.  Melting Relations of Basalt with Equilibrium Water Pressure Less Than Total Pressure , 1972 .