MINERAL CHEMISTRY OF ASBESTOS BEARING ULTRAMAFITES AND ASSOCIATED ROCKS FROM HOLENARASIPUR SCHIST BELT

Abstract

The predominant variety of asbestos fa m Holenarasipur schist belt is anthophyllite. it is derivea from the ultramafic rocks which are associated with amphibolites nzetapelites and TAAC (tremolite-actinolite, anthophyllite, chlorite) schist. Amphibolites contain tschermakite-hastingsite hornblende of Fel Fe+ Mg ratio 0 - 55 to 0 - 35. Plagicclase from the amphibolites have unusually high Cacontent, in the range of An 40 to An o. Some of the amphibolites have garnets with uncommon end member content of a1m 70-py 15-gr15. Anthophyllites contain less than one Al atom per unit formula. _They have inccherent Fe01 Mn0 ratio and variable CaO and Na2 0. Chlcrites have high mg-component (0 . 75 to 0•90); nonuniform SIMI ratio ranging from talc-chlorite to clinochlore. Staurclite and garnet from nzetapelites have Fe-component more than 0'85. Olivines from ultramafites
range from Fon to Fon ; their Ion Ca, Mn content and high Al0 3 indicate that the ultramafites are intrusives. Mineral chemistry of TA AC schists correspond to a mixed rock type of metapelite and ultramafites ranging _Trim dunite. harzburgite tc Iherzolite. The metamorphic reacticns in uttramafites and the contaminated rocks were accompanied by CO2 metasomatisni, which accc wits for tie serpehtineanthophyllite coexistence. P-T cc millions of metamr rphism correspond to upper green schist to lower amphibolite flacks, higher pressures, not commonly encountered in the continental  types. Anthophyllite acquiresfibrous nit rphc gy by recrystallisath nin CO2 rich fluid towards the waning stages of metamorphisn.. Minor demerits and directional pressures ma have been additional factcrs for the devaopment of asbestiform morphology.