CRYSTAL CHEMISTRY OF CHLORITES FROM PYRITIC COPPER AND POLYMETALLIC DEPOSITS OF RUDNYY ALTAI

Abstract

A sizable fraction of hydrothermally altered sedimentary rocks, surrounding ore bodies in pyritic copper and polymetallic deposits of the Rudnyy Altai, consists of shaly chloritic rocks, which usually are homogeneous and almost monomineralic. The aim of our study was to ascertain how metamorphism affects the crystal chemistry of such chlorites. From the results of X-ray analysis and IR spectroscopy, our chlorite specimens can be divided fairly clearly into two groups. Characteristic features of the first are diversity of polytypes (IIc, Ic), low aluminum content and sharp fluctuations in silicon-aluminum ratios. The chlorites of metamorphosed ore deposits are more homogeneous, monomineralic structurally stable (IIc polytype), and higher in iron and aluminum. From these data, we conclude that the crystal chemistry of chlorite depends on extent of dynamothermal metamorphism of the ore deposits.