Zr-Th-U MINERALS IN HIGH-MG DIORITE OF THE CHELYABINSK MASSIF (SOUTH URALS) – EVIDENCE FOR CRUST–MANTLE INTERACTION
Zr-Th-U minerals, namely baddeleyite, zircon and U-Th-oxide, were found in high-Mg diorite from the Late Devonian – Early Carboniferous synplutonic dyke in granodiorites of the Chelyabinsk massif, South Urals. Micron-sized minerals were investigated by electron microscopy and cathodoluminescence spe...
Published in: | Nature Communications |
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Main Authors: | , , , , , , , |
Other Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | Russian |
Published: |
Institute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch
2021
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Subjects: | |
Online Access: | https://www.gt-crust.ru/jour/article/view/1215 https://doi.org/10.5800/GT-2021-12-2-0528 |
Summary: | Zr-Th-U minerals, namely baddeleyite, zircon and U-Th-oxide, were found in high-Mg diorite from the Late Devonian – Early Carboniferous synplutonic dyke in granodiorites of the Chelyabinsk massif, South Urals. Micron-sized minerals were investigated by electron microscopy and cathodoluminescence spectroscopy. Their chemical compositions were determined by electron probe microanalysis that was optimized to ensure more precise measurements of the composition of minerals. Baddeleyite grains are found as inclusions in amphibole crystals and reside in intergranular areas. The former retain their composition and show no traces of corrosion or substitution. In the intergranular areas, baddeleyite grains were replaced by polycrystalline zircon due to the reaction with an acid melt, and the U-Th-oxide precipitated inside baddeleyite simultaneously, which suggests the restite origin of baddeleyite. The main features of the baddeleyite composition are extremely high concentrations of ThO2 and UO2 (to 0.03 wt. % and 1.0 wt. %, respectively), which may be due to the metasomatic interaction between the mantle peridotite and the crustal or carbonatite fluid or melt. В высокомагнезиальном диорите, слагающем синплутоническую дайку позднедевонско-раннекаменноугольного возраста в гранодиоритах Челябинского гранитоидного массива на Южном Урале, выявлена ассоциация Zr-Th-U минералов, представленная бадделеитом, ураноторианитом и цирконом. Минералы микронного размера исследовались методом электронной микроскопии и катодолюминесценции, а химический состав определялся методом электронно-зондового микроанализа (ЭЗМА), который был оптимизирован для измерения состава минералов с высокой локальностью. Бадделеит присутствует в виде включений субидиоморфных кристаллов в амфиболе и в межзерновом пространстве. Заключенный в амфиболе бадделеит сохраняет свой состав и не подвергается коррозии или замещению. В межзерновом пространстве в результате реакции с кремнекислым расплавом бадделеит замещается полизернистым цирконом с одновременным ... |
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