Abstract:
The new potassic high-calcium and rich-in-aluminum amphibolc - potassic-magncsiohastingsite was found in blocks of biotite-amphibolc gabbro from serpentinite melange of Ilmenogorsky metamorphic complex at the area of Ilmcnsky natural reserve (Chelyabinsk district, the South Urals, Russia), precisely at Osinovy mys (Aspen cape) on the lake Bolshoy Ishkul. Composition of this amphibole varies slightly in samples taken from different gabbro blocks, mainly in contents of K2O, SiO2, A^Oj. For instance, in sample ИК-194-5 its empirical formula was defined as (Ko.5jNao.47)y.o (Cai.90Mno.o6Mgo.o3Bao.oi)2.o(Mg2.o6Fe^'t fc'+ai^' Tiai9vo.oi)s.o8 [SieosAl! 97)8.0 O22J(OHi.93Onn7)2.o and in the sample ИК-194-16 it makes (Ko.esNao.JiBaowH.oCCa 1.9зМп0.обВа0.о1 h.o(Mg2.32 Рец2Рео+84А1о.47Т'о.17 ^zKSis.sjAl^yb,oO22](OH|.«Clo.uW- The host gabbros containing potassic-magnesio-hastingsite have the cenotypal image and the magmatic structure (ophitic, hypidiomorphic one). They seem to be xcnoliths rafted from rocks of the deep levels of the Urals earth crust and transported up to surface by protrusions of scrpcntinitcs.