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The Dehydroxylation of Chlorite and the Formation of Topotactic Product Phases

Published online by Cambridge University Press:  28 February 2024

Wudi Zhan  and
Stephen Guggenheim
Wudi Zhan
Affiliation:
Department of Geological Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois 60607-7059
Stephen Guggenheim
Affiliation:
Department of Geological Sciences, University of Illinois at Chicago, 845 W. Taylor St., Chicago, Illinois 60607-7059
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Abstract

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Single-crystal, X-ray examination of Mg,Fe-rich chlorites that were heated at 650°C for 24 hours in air and have undergone dehydroxylation of the interlayer shows that two product phases result with a topotactic relationship, with the c axis of both phases parallel. One phase (“modified chlorite” or “14-A phase”) has relatively sharp reflections with a 14-A c-axis repeat, indicating that it is well crystallized and maintains the 2:1 layer from the parent. Cell parameters are a = 5.368(1)A, b = 9.297(2)A, c = 14.215(6)A, a = 89.86(3)°, ß = 97.15(3)°, γ = 89.98(2)°, and it crystallizes in CĪ symmetry. A structure refinement, details of which will be reported later, indicates that the interlayer consists of two planes, each containing (M + O), where M is the interlayer cation species. These planes show about ±0.5A positional disorder along the [001] direction. There is no evidence for scattering material at z = 0.5 between the 2:1 layers. The second phase in the topotactic relationship is based on a 27-A unit c axis (“27-A phase”). The diffraction data are limited with about 15 diffuse reflections observed, indicating that it is poorly crystallized. The 27-A spacing suggests that both octahedral sheets in the parent chlorite contribute to the formation of this phase.

Heating Mg,Fe-rich chlorite powder in a closed system to 550°C, under either reducing or oxidizing conditions, prevents the formation of the 27-A phase. Because the 27-A phase forms in an open system, we infer that water fugacity is an important factor in its formation. Heating experiments involving samples with different polytypes and octahedral “type” (dioctahedral vs trioctahedral) of the 2:1 layer suggests that these two variables are important. However, the results are equivocal, and an ill-defined B-rich chlorite from Madagascar breaks the observed trends for both variations in stacking sequence and octahedral type. However, B-content may be a factor in the transformation also for those chlorites that contain B.

Keywords

ChloriteDehydroxylationTopotactic phasesX-ray diffraction
Type
Research Article
Information
Clays and Clay Minerals , Volume 43 , Issue 5 , October 1995 , pp. 622 - 629
Copyright
Copyright © 1995, The Clay Minerals Society

References

Bai, T.-B., Guggenheim, Stephen, Wang, Shi-Jie, Rancourt, Denis G., and Koster van Groos, A. F. 1993. Metastable phase relations in the chlorite-H2O system. Amer. Miner. 78: 1208–1216.Google Scholar
Bailey, S. W., 1980. Structures of layer silicates. In Crystal Structures of Clay Minerals and Their X-ray Identification. Brindley, G. W., and Brown, G., eds. London: Mineralogical Society, 1–124.Google Scholar
Brindley, G. W., and Ali, S. Z. 1950. X-ray study of thermal transformations in some magnesium chlorite minerals. Acta Crystallogr. 3: 25–30.Google Scholar
Brindley, G.W., and Chang, Tien-Show. 1974. Development of long basal spacings in chlorites by thermal treatment. Amer. Miner. 59: 152–158.Google Scholar
Caillère, S., and Hénin, S. 1960. Relation entre la constitution cristlochemique des phyllites et leur température de dehydration application au cas des chlorites. Bull. Société Française Céramiques 48: 63–67.Google Scholar
Cerný, P., 1970. Compositional variations in cookeite. Can. Mineral. 10: 636–647.Google Scholar
Evans, B. W., and Guggenheim, S. 1988. Talc, pyrophyllite, and related minerals. In Hydrous Phyllosilicates (Exclusive of Micas). Bailey, S. W., ed. Mineralogical Society of America Reviews in Mineralogy 19: 225–294.Google Scholar
Fransolet, A.-M., and Bourguignon, P. 1978. Di/trioctahedral chlorite in quartz veins from the Ardenne, Belgium. Can. Mineral. 16: 365–373.Google Scholar
Guggenheim, S., Schulze, W. A., Harris, G. A., and Lin, J.-C. 1983. Noncentric layer silicates: An optical second harmonic generation, chemical, and X-ray study. Clays & Clay Miner. 31: 251–260.CrossRefGoogle Scholar
Guggenheim, S., Chang, Y.-H., and Koster van Groos, A. F. 1987. Muscovite dehydroxylation: High temperature studies. Amer. Miner. 72: 537–550.Google Scholar
Lacroix, A., 1922. Minéralogie de Madagascar, I, Paris.Google Scholar
Lin, C-y., and Bailey, S. W. 1985. Structural data for sudoite. Clays & Clay Miner. 33: 410–414.Google Scholar
Miser, H. D., and Milton, C. 1964. Quartz, rectorite, and cookeite from the Jeffrey Quarry, near North Little Rock, Pulaski County, Arkansas. Bull. Ark. Geol. Commission 21: 29 pp.Google Scholar
Moore, D. M., and Reynolds, R. C. Jr. 1989. X-ray Diffraction and the identification and analysis of clay minerals. Oxford: Oxford University Press, 332 pp.Google Scholar
Nelson, D. O., and Guggenheim, S. 1993. Inferred limitations to the oxidation of iron in chlorite: A single-crystal high-temperature X-ray study. Amer. Miner. 59: 1197–1207.Google Scholar
Phillips, T. L., Loveless, J. K., and Bailey, S. W. 1980. Cr3+ coordination in chlorites: A structural study of ten chromian chlorites. Amer. Miner. 65: 112–122.Google Scholar
Ranorosoa, N., Fontan, F., and Fransolet, A.-M. 1989. Rediscovery of manandonite in the Sahatany Valley, Madagascar. Eur. J. Mineral. 1: 633–638.Google Scholar
Saccocia, Peter J., and Seyfried, William E. Jr. 1994. The solubility of chlorite solid solutions in 3.2 wt% NaCl fluids from 300-400°C, 500 bars. Geochim. Cosmochim. Acta 58: 567–585.CrossRefGoogle Scholar
Villieras, F., Yvon, J., Cases, J. M., Donato, P. de, Lhote, F., and Baeza, R. 1994. Development of microporosity in clinochlore upon heating. Clays & Clay Miner. 42: 679–688.Google Scholar