Experimental study of spinel-garnet phase transition in upper mantle and its significance
- 81 Downloads
Experimental study of spinel-garnet phase transition was carried out using natural mineral and rock specimens from xenolith of mantle rocks in Cenozoic basalt as starting materials. From the result it was found that the condition of spinel Iherzolite-garnet Ihenolite phase transition (T = 1 100°C andP = 1.8–2.0 GPa) is consistent with theP-T equilibrium condition of the five-phase assemblage spinel/garnet Iherzolite in eastern China, suggesting that there may exist a spinel-garnet Iherzolite phase transition zone with the thickness of a few km to several ten km at the depth of 55–70 km in the continental upper mantle of eastern China. The depth of phase transition from spinel pyroxenite to garnet pyroxenite is found to be less than 55 km. Experiment results also show that water promotes metasomatism on one hand but suppresses phase transition on the other. Zoning of mineral composition was also discussed.
Keywordsspinel-garnet phase transition high temperature and high pressure experiment upper mantle of eastern China phase transition zone
Unable to display preview. Download preview PDF.
- 5.Willkinson, J. F. G., Le Maitre, R. W., Upper mantle amphiboles and micas and TiO2, K2O, and P2O5 abundances and 100Mg/(Mg+Fe2+) ratios of common basalts and andesites: Implications for modal mantle metasomatism and undepleted mantle composition,J Petrol., 1987, 28: 37Google Scholar
- 7.Fan, Q C., Hooper, P. R., The mineral chemistry of ultrarnafic xenoliths of eastern China: Implications for upper mantle composition and the paleogeotherms,J Petrol., 1989, 30: 1117Google Scholar
- 8.Fan, Q C., Liu, R X., Study on phase transition of multiple spinel/garnet peridotite in upper mantle beneath eastern China,The Collections of Characteristics of the Upper Mantle and Dynamic of China, Beijing: Seismology Press, 1990, 72–82Google Scholar
- 9.Fan, Q C., Liu, R. X., Spinel/garnet lherzolite in Late Tertiary limburgitic pipe from Hebi, Henan Province and its genesis,New Development in Mineralogy, Petrology and Geochemistry Study in China (in Chinese), Lanzhou: Lanzhou University Press, 1994, 141–142Google Scholar
- 11.LADEL Study Group, A lithospheric seismic refraction profile in the western north Atlantic Ocean,Geophys. J R Abstr. Soc., 1983, 75: 23Google Scholar
- 13.Brey, G. P., Kohler, T., Nickel, K. G., Geothermobarometry in four-phase Ihemlites—I Experimental results from 10 to 60 kb,J Petrol, 1990, 31: 1313Google Scholar