Structure and Petrography of the Quartz-Magnetite and Associated Rocks of Siddipet Area, Medak District, Andhra Pradesh

A series of detached hills composed of quartz-magnetite rocks and diabases occur in the districts of Medak, Nizamabad, Adilabad and Karimnagar of Andhra Pradesh. The country rock is granitic gneiss and is cut across by a number of dykes. The structure of these rocks near Siddipet in Medak district has been studied in detail, and a number of traverses also made between Armur and Jagtial to the north in the districts of Nizamabad and Karimnagar to infer the probable overall structure of the region.

The quartz-magnetite rocks contain quartz and magnetite only and are devoid of ferro-magnesian minerals. The diabases in the Siddipet area are divided into two groups, one rich in hornblende and the other in pyroxene on the basis of petrographic study.

From a study of the outcrop pattern of the quartz-magnetite rocks and diabase bands in the Siddipet area, three traces of axial planes of folds (FI, FII, FIII) possibly related to three ages of folding are inferred. These rocks have been faulted along N-S and NE-SW directions. From the overall pattern of outcrop of these rocks in the entire region, it is surmised that the rocks of Siddipet area form a part of a major NW plunging anticline with an overturned western limb and with the nose of the fold being near the Godavari river.