High-Fe Garnet Paraamphibolites at the Base of the Khabarny Ophiolitic Allochthon in the Southern Urals

摘要

Ophiolitic allochthons are often accompanied by metamorphic rocks, which bear additional information on the tectonic setting and formation conditions of allochthons. Metamorphic aureoles are most frequently composed of greenschist- and amphibolite-facies metabasic rocks. In some cases, the peak of metamorphism is marked by garnet amphibolites or eclogites. Well-studied metamorphic complexes are known at the base of the Voikar-Syn'ya and Kempirsai ophiolitic massifs in the Polar and southern Urals, respectively. According to Efimov et al. [2, 3], garnet amphibolites were formed in these massifs as a result of high-pressure metamorphism characterized by a counterclockwise PT trend. The maximum PT parameters were 750-500℃ at 10-13 kbar. Various gabbroic rocks and less abundant basic volcanics served as protoliths. We found garnet amphibolites at the base of the Khabarny ophiolitic allochthon. The unusual phase and chemical compositions of these rocks testify, in our opinion, to the sedimentary nature of the protolith.