Sub-microscopic textures and retrogressive metamorphic origin of Longxi nephrite
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Nephrite specimens from Longxi, Sichuan, prepared by ion-thinning and dispersion techniques have been studied using TEM and SAED. A series of sub-microscopic textures such as (010) multiple-chain faults and related fault terminations, (001) mechanical twinning, sub-grain boundaries or fault walls, tremolite fibrous pseudoform of talc and intergrowth of tremolite and talc with (010) as interface are revealed. By analogy of metallographic textures, characteristics and mechanisms of the process of “deformation — recovery — recrystallization” are discussed in detail, Topotactic reaction mechanism by which tremolite retrogresses to talc was studied and a retrogressive metamorphic origin of Longxi nephrite is proposed.
KeywordsSlip System Talc Fault Wall Mechanical Twinning Electron Diffraction Study
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- Bradt, R.C., Newnham, R.E. and Biggers, J.V. (1973) The toughness of jade,Am. Mineral. 58, 727 - 732.Google Scholar
- Wang Chunyun (1988) Mineralogical study of Longxi Nephrite. M.S. thesis. Institute of Geochemistry, Academia Sinica (in Chinese).Google Scholar
- Wang Chunyun, Ren Guohao, Xie Yuanzhang and Li Yaguo (1989) Topotactic reaction from tremolite to talc: Electron diffraction study of Longxi Nephrite.Acta Mineralogica Sinica (in press)(in Chinese).Google Scholar
- Humphreys, F. J. (1979) Recrystallization mechanisms in two-phase alloys.Metal Science 13, 136 - 145.Google Scholar
- Knopf, E.B. (1931) Retrogressive metamorphism and phyllonitization, part I.Am. J. Sci. 21, 319–331.Google Scholar
- Leaming, S.F. (1978) Jade in Canada. Paper Geol. Sury. Canada, 78–19.Google Scholar
- Vernon, R. H. (1976) Metamorphic Processes, Reaction and Microstructure Development. Allen and Unwin, Ltd., London.Google Scholar
- Whinkler, H.G.F. (1967) Petrogenesis of Metamorphic Rocks, 2nd ed., Springer-Verlag Berlin Heidelberg New York.Google Scholar