Open AccessZr-Th-U MINERALS IN HIGH-MG DIORITE OF THE CHELYABINSK MASSIF (SOUTH URALS) – EVIDENCE FOR CRUST–MANTLE INTERACTION
Author(s) -
Т. А. Осипова,
Г. А. Каллистов,
Д. А. Замятин,
В. А. Булатов
Publication year - 2021
Publication title -
geodinamika i tektonofizika
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.336
H-Index - 8
ISSN - 2078-502X
DOI - 10.5800/gt-2021-12-2-0528
Subject(s) - baddeleyite , zircon , carbonatite , geochemistry , massif , geology , metasomatism , cathodoluminescence , molybdenite , diorite , amphibole , tremolite , mantle (geology) , mineralogy , materials science , metallurgy , paleontology , quartz , optoelectronics , luminescence , fluid inclusions , asbestos
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 ThO 2 and UO 2 (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.