Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-25T07:06:58.399Z Has data issue: false hasContentIssue false
  • English
  • Français

Fertility of crustal rocks during anatexis

Published online by Cambridge University Press:  03 November 2011

Alan Bruce Thompson
Alan Bruce Thompson
Affiliation:
Alan Bruce Thompson. Erdwissenschaften. ETH Zurich. CH-8092., Switzerland
Get access Rights & Permissions [Opens in a new window]

Abstract:

After many years of systematic experimental investigations, it is now possible to quantify the conditions for optimum fertility to melt production of most common crustal rock types as functions of temperature and to about 30 kbar pressure. Quartzo-feldspathic melting produces steady increases in melt proportion with increasing temperature. The exact melt fraction depends on the mineral mode relative to quartz-feldspar eutectics and the temperatures of mica dehydration melting reactions. Mica melting consumes SiO2 from residual quartz during the formation of refractory Al2SiO5, orthopyroxene, garnet or cordierite.

A simple graphical interpretation of experimental results allows a deduction of the proportions of mica and feldspar leading to optimum fertility. In effect, the mica dehydration melting reactions, at specific pressure and are superimposed on quartz-feldspar melting relations projected onto Ab-An-Or. Fertility to melt production varies with the mica to feldspar ratio and pressure. Pelites are more fertile than psammites at low pressures (e.g. 5 kbar), especially if they contain An40 to An50 plagioclase. At higher pressure (e.g. 10-20 kbar) and for rocks containing albitic plagioclase, psammites are more fertile than pelites. For a typical pelite (e.g. with An25 at 20 kbar), the cotectic with muscovite lies at higher (≍·) and XAb (≍0·42) than with biotite :≍0·35; XAb(≍·), thus dehydration melting of muscovite requires 10% more plagioclase for fertility than does biotite.

The first melts from dehydration melting of muscovite (with Plg + Qtz) are more sodic and form at lower temperatures than the first melts from Bio + Plg + Qtz. With increasing pressure, to at least 30 kbar, granite minimum and mica dehydration melts become more sodic. This indicates that of such melts is greater than 0·3.

Keywords

optimum melt productioncrustal anatexisdehydration meltingmetasedimentsmica-feldspar ratiopressure
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 87 , Issue 1-2: Third Hutton Symposium. The Origin of Ganites and Related Rocks , 1996 , pp. 1 - 10
Copyright
Copyright © Royal Society of Edinburgh 1996

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Abbott, R. N. 1978. Peritectic reactions in the system. An-Ab-Or-Qz-H2O. CAN MINERAL 16, 245–56.Google Scholar
Ai, Y.&Green, D. H. 1989. Phase relations in the system anorthitepolassium-feldspar at lOkbar with emphasis on their solid solutions. MINERAL MAG 53, 337–45.CrossRefGoogle Scholar
Burnham, C. W. 1967. Hydrothermal fluids at the magmatic stage. In: Barnes, H. L. (ed.) Geochemistry of hydrothermal ore deposits. 34–67. New York: Holt, Rinehart and Winston.Google Scholar
Burnham, C. W. 1979. Magmas and hydrothermal fluids. In: Barnes, H. L. (ed.) Geochemistry of hydrothermal ore deposits. 2nd edn. 71–136. New York: Wiley-Interscience.Google Scholar
Carmichael, I. S. E. 1963. The crystallization of feldspar in volcanic acid liquids. Q J GEOL SOC LONDON 119, 95–131.CrossRefGoogle Scholar
Clemens, J. D.&Vielzeuf, D. 1987. Constraints on melting and magma production in the crust. EARTH PLANET SCI LETT 86, 287–306.CrossRefGoogle Scholar
Ebadi, A.&Johannes, W. 1991. Beginning of melting and composition of first melts in the system Qz-Ab-Or-H2O-CO2. CONTRIB MINERAL PETROL 106, 286–95.CrossRefGoogle Scholar
Gardien, V., Thompson, A. B., Grujic, D.&Ulmer, P. 1994. The role of the source composition on melt fractions generation during crustal anatexis. EOS. TRANS AM GEOPHYS UNION, 75, 359–60.Google Scholar
Gardien, V., Thompson, A. B., Grujic, D.&Ulmer, P. 1995. Melt fractions during crustal anatexis. Experimental melting of biotite + plagioclase + quartz ± muscovite assemblages and implications for crustal melting. J GEOPHYS RES 100, 15581–91.CrossRefGoogle Scholar
Harris, N. B. W.&Inger, S. 1992. Trace element modelling of pelitederived granites. CONTRIB MINERAL PETROL 110, 46–56.CrossRefGoogle Scholar
Holtz, F.&Johannes, W. 1991. Experimental investigation of H2O-saturated and H2O-undersaturated liquidus phase relations in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O-CO2 at 2 and 5kbar. J PETROL 32, 935–58.CrossRefGoogle Scholar
Huang, W. L.&Wyllie, P. J. 1975. Melting reactions in the system NaAlSi3O8-KAlSi3O8-SiO2 to 35 kilobars, dry and with excess water. J GEOL 83, 737–48.CrossRefGoogle Scholar
Huang, W. L.&Wyllie, P. J. 1981. Phase relationship of S-type granite with H2O to 35 kbar: Muscov granite from Harney Peak. South Dakota. J GEOPHYS RES 86, 1015–29.CrossRefGoogle Scholar
James, R. S.&Hamilton, D. L. 1969. Phase relations in the system NaAlSi3O8-KAlSi3O8-CaAl2Si2O8-SiO2 at 1 kilobar water vapour pressure. CONTRIB MINERAL PETROL 21, 111–41.CrossRefGoogle Scholar
Keppler, H. 1989. The influence of the fluid phase composition on the solidus temperatures in NaAlSi3O8-KAlSi3O8-SiO2-H2O-CO2. CONTRIB MINERAL PETROL 102, 321–7.CrossRefGoogle Scholar
Le Breton, N.&Thompson, A. B. 1988. Fluid-absent (dehydration) melting of biotite in metapelites in the early stage of crustal anatexis. CONTRIB MINERAL PETROL 99, 226–37.CrossRefGoogle Scholar
Le Breton, N.. Scaillet, B.&Pons, J. 1995. Amphibole stability in granitoid melts. Experimental constraints. TERRA ABSTR 7, 297.Google Scholar
Luth, W. C. 1969. The systems NaAlSi3O8-SiO2 and KAlSi3O8-SiO2 to 20 kbar and the relationship between H2O content, PH20 and Ptotal in granitic magmas. AM J SCI 267–A, 325–41.Google Scholar
Luth, W. C,Jahns, R. H.&Tuttle, O. F. 1964. The granite system at pressures of 4 to 10 kilobars. J GEOPHYS RES 69, 759–73.CrossRefGoogle Scholar
Naney, M. T. 1983. Phase equilibria of rock forming ferromagnesian silicates in granitic systems. AM J SCI 283, 993–1033.CrossRefGoogle Scholar
Patiño Douce, A. E. 1996. Effects of pressure and H2O content on the compositions of primary crustal melts. TRANS R SOC EDINBURGH 87, 000-000.Google Scholar
Patiño Douce, A. E.&Beard, J. S. 1995. Dehydration-melting of biotite gneiss and quartz amphibolite from 3 to 15kbar. J PETROL 36, 707–38.CrossRefGoogle Scholar
Patiño Douce, A. E.&Johnston, A. D. 1991. Phase equilibria and melt productivity in the pelitic system: implications for the origin the of peraluminous granitoids and aluminous granulites. CONTRIB MINERAL PETROL 107, 202–18.CrossRefGoogle Scholar
Petö, P. 1976. An experimental investigation of melting relations involving muscovite and paragonite in the silica-saturated portion of the system K2O-Na2O-SiO2-H2O to 15kbar total pressure. PROGR EXP PETROL NERC LONDON 3, 41–5.Google Scholar
Petö, P.&Thompson, A. B. 1974. Wet and dry melting of white micaalkali feldspar assemblages. TRANS AM GEOPHYS UNION 55, 479.Google Scholar
Schairer, J. F. 1950. The alkali-feldspar join in the system NaAlSi3O8-KAlSi3O8-SiO2. J GEOL 58, 512–8.CrossRefGoogle Scholar
Singh, J. 1995. Dehydration melting of tonalites—implications for the origin of continental crust. TERRA ABSTR 7, 297.Google Scholar
Skjerlie, K. P.&Johnston, A. D. 1992. Vapor-absent melting at lOkbar of biotite- and amphibole-bearing tonalitic gneiss: implications for the generation of A-type granites. GEOLOGY 20, 263–6.2.3.CO;2>CrossRefGoogle Scholar
Skjerlie, K. P.&Johnston, A. D. 1993. Fluid-absent melting behaviour of an F-rich tonalitic gneiss at mid-crustal pressures: implications for the generation of anorogenic granites. J PETROL 34, 785–815.CrossRefGoogle Scholar
Stevens, G.Clemens, J. D.&Droop, G. T. R. 1995. Hydrous cordierite in granulites and crustal magma production. GEOLOGY 23, 925 8.2.3.CO;2>CrossRefGoogle Scholar
Stewart, D. B.&Roseboom, E. H. 1962. Lower temperature terminations of the three-phase region plagioclase-alkali feldsparliquid. J PETROL 3, 280–315.CrossRefGoogle Scholar
Thompson, A. B. 1982. Dehydration melting of pelitic rocks and the generation of H2O-undersaturated granitic liquids. AM J SCI 282, 1567–95.CrossRefGoogle Scholar
Thompson, A. B. 1988. Dehydration melting of crustal rocks. REND SOC ITAL MINERAL PETROL 43, 41–60.Google Scholar
Thompson, A. B.&Connolly, J. A. D. 1995. Melting of the continental crust: some thermal and petrological constraints on anatexis in continental collision zones and other tectonic settings. J GEOPHYS RES 100, 15565–79.CrossRefGoogle Scholar
Thompson, A. B.&Tracy, R. J. 1979. Model systems for anatexis of pelitic rocks. CONTRIB MINERAL PETROL 70, 429–38.CrossRefGoogle Scholar
Thompson, J. B.&Thompson, A. B. 1976. A model system for mineral facies in pelitic schists. CONTRIB MINERAL PETROL 58, 243–77.CrossRefGoogle Scholar
Tuttle, O. F.&Bowen, N. L. 1958. Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2H2O. GEOL SOC AM MEM 74, 153 pp.Google Scholar
Vielzeuf, D.&Holloway, K. R. 1988. Experimental determination of the fluid-absent melting relations the pelitic system. Consequences for crustal differentiation. CONTRIB MINERAL PETROL 9, 257–76.CrossRefGoogle Scholar
Vielzeuf, D.&Montel, J. M. 1994. Partial melting of metagrey wackes. Part I. Fluid-absent experiments and phase relationships. CONTRIB MINERAL PETROL 117, 375–93.CrossRefGoogle Scholar
Waldbaum, D. R.&Thompson, J. B. 1969. Mixing properties of sanidine crystalline solutions: IV. Phase diagrams from equation of state. AM MINERAL 54, 1274–98.Google Scholar
Winkler, H. G. F. 1979. Anatexis. formation of migmatites. and origin of granitic magmas. In Petrogenesis of metamorphic rocks, 5th edn. New York: Springer.CrossRefGoogle Scholar
Winkler, H. G. F.&Ghose, N. C. 1973. Further data on the eutectics in the system Qz-Or-An-H2O. N JAHRB MINERAL MONATSH 31, 481–4.Google Scholar