Sulfides of blyb metamorphic complex of the Northern Caucasus: new type of minerals-container for high pressure and premetamorphic mineral assemblages
Category: 14-1
UDC 552.48
A. N. Konilov(1), G.V. Bondarenko(2), K.A. Dokukina(1), V.A. Kamzolkin(3)
(1) Geological Institute, Russian Academy of Sciences, Moscow, Russia
(2) Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Russia
(3) Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Abstract
In sulfides of paragneisses of the Blyb metamorphic complex (BMC) of the Northern Caucasus Fore Range inclusions of minerals – indicators of high pressures: paragonite, phengite, omphacite are found. Composition of the omphacite is almost identical to known compositions of omphacites from eclogite bodies placed in the BMC. As a result of imposing of intensive retrograde processes mineral associations of high pressures apparently are completely erased from rock fabric. Sulfides relicts of high pressure minerals are also exposed to alteration process and are partially replaced by ferrigidrits, with replacement omphacite by aegirine and a hornblende. Preservation of fragments of early association in minerals containers allows to reconstruct PT condition of formation of the BMC gneisses. Peak conditions of a metamorphism of the complex can reach 16 kbar at 680 °С. As a result of study the A-type of subduction for BMC was established. This indicates essential shortening of Caucasian lithosphere in middle Palaeozoic time.
Keywords: mineral-containers, pyrites, HP-complexes.
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