UHPM eclogite of the Maksyutov complex (Southern Urals)

摘要

This study reports the first find of a jadeite-bearing eclogite spatially associated with UHP ultramafic rocks of unit 1 of the Maksyutov complex (near the village of Karayanovo). Two phases of elcogitization were recognized based on mineralogical data, petrographic observations, and isotope geochronology. The first UHP metamorphic stage (533 +/- 4.6 Ma, P > 4.4 GPa, T > 700A degrees C) was defined by the assemblage jadeite + grossular-almandine + rutile +/- phengite. This assemblage was later transformed into omphacite + grossular-almandine + phengite + albite + clinozoisite + titanite at a retrograde phase of stage I (392-485 +/- 2-4 Ma, P > 3.1-3.4 GPa, T > 633-740A degrees C) with decreasing pressure and temperature. The second prograde phase (360 +/- 3 Ma, P > 1.1-2.2 GPa, T > 450-550A degrees C) of HP metamorphism was marked by the development of a chlorite rim (almandine-grossular-pyrope-almandine-grossular, diopside, clinozoisite) around the eclogite body. A comparison shows that the studied eclogite and ultramafic rocks followed a common P-T-t path. Jadiet-bearing eclogites and meta-ultramafic rocks represent UHPM fragments of the mantle and crust, which were tectonically emplaced in quartzite schists of unit 1.