Abstract
Vanadian-+hromian tourmaline (as much as 4.06 wl.Vo Y 2O3 and 2.387o Cr2O3) and vanadian muscovite (w much as 2.13Vo V2O3) occur in contact-metamorphosed carbonaceous metasediments of the hibrezhnaya anticlinal zone in himorye, Russia. Cfus'ias are compositionally zoned, showing depletion in V and Cr, and enrichment in Al, Mg and Fe, from core to-rim. Zoning is attributed to progressive decrease of VindCr contents in the host rock durilg the coune of crystal growth. Cr and V are incorporated according to the schemes: Cf* <+ Al3+ and V3* <-+ 1Mg2*,Fe2*,Mn2*;. The charge increase that results from the latter exchangeisconsideredtobecompensatedbytheconcomitantsubstitutionofrvAlforSiandbytheappearanceofvacancies in the X site. The associated vanadian muscouite contains minor amounts of Mg, Fe, Ti and Na. An empirical formula calculated from results of an electron-microprobe analysis is (K1.9aNas.69)r2.03(Al3.34v0.29lvlgn.26Tis.65Fe0.0rx,96 (Si6.27Alr.i3)x.00O22(OH)2. Both minerals are products of contact metamorphism of V-Cr-bearing carbonaceous rocks.
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