Petrographical Characters of Some important host rocks in Vizianagarm Manganese Ores Belt (A.P.), INDIA.

Abstract

Petrographical study of various rocks types has been carried out in the present study area with the discovery of a new rock type- Crystalline algal Limestone. An attempt has been made to describe the petrographical characters of the following rock types encountered in the present study area.
1. Calc-granulite
2. Garnet-sillimanite-feldspathic gneiss
3. Garnetiferous gneiss
4. Feldspathic quartzite
5. Crystalline algal limestone
6. Shale
7. Hypersthene gneiss.
8. Granitic gneiss.
The older Khondalite Group mainly consists of calc-granulite, garnet sillimanite gneiss, feldspathic quartzite and garnetiferous gneiss. The occurrence of crystalline algal limestone and red and green shales have been reported for the first time. The younger Charnockite Group mainly consists of hypersthene gneiss (porphyrroblastic and non-porphyroblastic) and granitic gneisses. Granite and pegmatite occur as intrusive bodies in this

group of rocks. The Khondalites and Charnockites show a complex structural pattern resulting from repeated periods of deformation. The general strike of rocks is NW-SE with local swings at places. These rocks at places show relict banding.
Stratigraphically these are included within a thick succession of Pre- Cambrian rocks belonging to the Khondalite and Charnockite Groups of Dharwar Supergroup, that form a part of Eastern Ghat Complex of India. The manganiferous rocks that have been encountered in the Vizianagarm Manganese Ore Belt (A.P.) India are known as Kodurites. At different places the rock types constituting the host rocks of manganese are essentially garnet sillimanite gneiss (Chipurupalle and Garbham), quartzite and garnetiferous quartzite (Garbham, Koduru, Perapi & Avagudem) and
calc granulites and gneisses (Koduru).

Keywords: Pertrography, Vizianagram, Manganeses Ores, Khondalite, Charnockite, Calc-granulite, Garnet Sillimanite Gneiss, Felspathic Quartzite, Crystalline Algal Limestone.