AN IMPROVED MODEL FOR STRUCTURAL TRANSFORMATIONS OF HEAT-TREATED ALUMINOUS DIOCTAHEDRAL 2:1 LAYER SILICATES
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dc.contributor.author | Drits V.A. | |
dc.contributor.author | Besson G. | |
dc.contributor.author | Muller F. | |
dc.date.accessioned | 2020-12-03T08:41:37Z | |
dc.date.available | 2020-12-03T08:41:37Z | |
dc.date.issued | 1995 | |
dc.identifier | https://elibrary.ru/item.asp?id=31101076 | |
dc.identifier.citation | Clays and Clay Minerals, 1995, , 6, 718-731 | |
dc.identifier.issn | 0009-8604 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/20320 | |
dc.description.abstract | An improved model for the interpretation of thermal effects during dehydroxylation in alu- minous dioctahedral 2:1 layer phyllosilicates considers trans-vacant (tv) and cis-vacant (cv) 2:1 layers and leads to very different temperatures of dehydroxylation for these tv and cv vacant modifications. In particular, smectites and illites consisting ofcv 2:1 layers are characterized by dehydroxylated temperatures which are higher by 150"C to 200"C than those for the same minerals consisting of the tv 2:1 layers. A considerable lengthening of the OH-OH edges in cv 2:1 layers in comparison with the OH-OH edges in the tv 2:1 layers is postulated as the reason for the higher dehydroxylation. Dehydroxylation in aluminous cv 2:1 layer silicates should occur in two stages. Initially, each two adjacent OH groups are replaced by a residual oxygen atom and the A1 cations, which originally occupied cis -and trans-sites, become 5- and 6-coordinated, respectively. The structure of 2:1 layers corresponding to this stage of the dehydroxylation is unstable. Thus the AI cations migrate from the former trans-sites to vacant pentagonal prisms. The resulting dehydroxylated structure of the original cv 2:1 layers is similar to that of the former tv 2:1 layers. Diffraction and structural features of the cv dehydroxylates predicted by the model are in agreement with X-ray diffraction effects observed for cv illite, illite-smectite and montmorillonite samples heated to different temperatures. In particular, the diffusion of A1 cations to empty five-fold prisms during dehydroxylation of the tv 2:1 layers explains why dehydroxylation of reheated cv montmorillonites occurs at temperatures lower by 150"C to 200"C than samples that were not recycled. | |
dc.title | AN IMPROVED MODEL FOR STRUCTURAL TRANSFORMATIONS OF HEAT-TREATED ALUMINOUS DIOCTAHEDRAL 2:1 LAYER SILICATES | |
dc.type | Статья |
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