Metamorphic evolution of eclogite and associated garnet-mica schist in the high-pressure metamorphic Maksyutov complex, Ural, Russia

Metasedimentary garnet-mica schists are interlayered with metabasic garnet–omphacite schists and enclose eclogite boudins in the high-pressure metamorphic Maksyutov complex in the Southern Urals, Russia. These three rock types were investigated in one outcrop and compared chemographically and thermobarometrically. The Fe/Mg distributions between garnet rim–omphacite and garnet rim–phengite pairs indicate different equilibration temperatures for the three samples, with the lowest temperature (500°C, >1.5 GPa) for the eclogite boudin, an intermediate temperature (630°C, >1.7 GPa) for the foliated eclogite and the highest temperature (650°C, >1.7 GPa) for the garnet-mica schist. The garnets in garnet-mica schist enclose abundant chloritoid relics and the Fe/Mg distribution between chloritoid and garnet records an earlier high-temperature stage (650°C, >2.0 GPa) before the garnet rim–phengite temperatures were reached. Together with some minimum- and maximum-pressure estimates three different prograde pressure–temperature paths and a common retrograde metamorphic evolution are interpreted from the chemographic and thermobarometric data. The different early metamorphic evolutions and conditions confirm the variability of protoliths, which are also indicated by different U/Pb zircon and rutile ages.     

厂坝铅锌矿床中钠长石岩的成因探讨

厂坝铅锌矿床中钠长石岩的产状、常量元素、微量元素、稀土元素和放射性同位素等地质地球化学特征表明．该岩石为中泥盆统成矿流体在海底沉积和交代围岩形成的典型热液沉积岩——钠长石岩，其物质来自矿体的下状沉积地层柱和海水。该沉积岩在后期的强烈变质改造过程中，发生了重结晶作用。