Experimental study of spinel-garnet phase transition in upper mantle and its significance

• Published in: Science China. Earth sciences Vol. 40; no. 4; pp. 383 - 389
• Main Author: 樊祺诚 刘若新 谢鸿森 张月明 徐平 林卓然
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.08.1997
• Subjects: and; Basalt; Cenozoic; China; eastern; Equilibrium; Equilibrium conditions; experiment; Garnet; Garnets; high; Mantle; Mineral composition; Mineralogy; Minerals; phase; Phase assemblages; Phase transformations; Phase transitions; pressure; Rock; Rocks; Spinel; spinel-garnet; temperature; Thickness; transition; Transition zone; Ugh; upper; Upper mantle; zone; Zoning
• ISSN: 1674-7313; 1006-9313; 1869-1897; 1862-2801
• DOI: 10.1007/BF02877569

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 lherzolite-garnet lherzolite phase transition ( T = 1100℃ and P = 1.8-2.0 GPa) is consistent with the P-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 pyrox-enite 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.