SUPERSILICIC CLINOPYROXENE AND SILICA EXSOLUTION IN UHPM ECLOGITE AND PELITIC GNEISS FROM THE KOKCHETAV MASSIF, KAZAKHSTAN
- DSpace Home
- →
- Геология России
- →
- ELibrary
- →
- View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.
dc.contributor.author | Katayama I. | |
dc.contributor.author | Parkinson C.D. | |
dc.contributor.author | Okamoto K. | |
dc.contributor.author | Nakajima Y. | |
dc.contributor.author | Maruyama S. | |
dc.date.accessioned | 2021-01-29T07:11:11Z | |
dc.date.available | 2021-01-29T07:11:11Z | |
dc.date.issued | 2000 | |
dc.identifier | https://elibrary.ru/item.asp?id=13804706 | |
dc.identifier.citation | American Mineralogist, 2000, 85, 10, 1368-1374 | |
dc.identifier.issn | 0003-004X | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/24019 | |
dc.description.abstract | Abundant exsolved quartz rods occur in matrix clinopyroxene of eclogite from the Kokchetav massif, Kazakhstan. These rocks are diamond-grade, ultrahigh-pressure (UHP) metamorphic rocks that recrystallized at P > 6 GPa and T > 1000 °C, Zircon is an excellent container, which effectively protects peak UHP metamorphic phases from retrogression. Therefore, to ascertain the pre-exsolution composition of the clinopyroxene, we analyzed clinopyroxene inclusions in zircon of the eclogite and a diamond-bearing biotite gneiss. Clinopyroxene in zircon has an excess of Fe3+ + (VI)Al over (IV)Al + Na + K, and calculated cation totals significantly less than 4.0 per six O atoms. The stoichiometry of these pyroxenes can be reconciled if the Ca-Eskola end-member (Ca0.5[ ]0.5AlSi2O6) is considered. The zircon-hosted clinopyroxene in the eclogite contains up to 9.6 mol% of the Ca-Eskola component, and in the biotite gneiss up to 18.2 mol%, whereas the matrix clinopyroxene contains much less (1.3 mol%, on average). Recalculation of the composition of the matrix clinopyroxene prior to exsolution of quartz rods yields 6.8 mol% Ca-Eskola component, which is consistent with the composition of the clinopyroxene inclusions in zircon. We conclude that the Ca-Eskola component in the peak metamorphic clinopyroxenes broke down by a retrograde reaction: 2 Ca0.5[ ]0.5AlSi2O6 → CaAl2SiO6 + 3 SiO2 resulting in exsolution of the quartz rods in the matrix clinopyroxene. Subducted crustal and supracrustal rocks from the Ca-Eskola clinopyroxene at high pressures and temperatures. The vacancy-containing clinopyroxene may have an important bearing on the physico-chemical properties of the subducted slab at upper mantle depth. | |
dc.title | SUPERSILICIC CLINOPYROXENE AND SILICA EXSOLUTION IN UHPM ECLOGITE AND PELITIC GNEISS FROM THE KOKCHETAV MASSIF, KAZAKHSTAN | |
dc.type | Статья |
Files in this item
This item appears in the following Collection(s)
-
ELibrary
Метаданные публикаций с сайта https://www.elibrary.ru