A NEW OCCURRENCE OF KIMBERLITE NEAR KOTAKONDA, MAHBOOBNAGAR DISTRICT,ANDHRA-PRADESH

A Kimberlite dyke, with the appearance of a conglomerate due to the pr esence of mega and macro-crysts of olivine resembling pebbles, is loca ted for the first time near Kotakonda, at about 10 km SSE of the known kimberlitic occurrences of Maddur area. Its massive look, lack of cou ntry rock xenoliths, local trachytic texture and concentration of mega crysts of olivine and orthopyroxene reflect hypabyssal nature. It cons ists mainly of rounded and corroded mega and macro-crysts of serpentin e pseudomorphs of olivine.and subordinate ortho- and clinopyroxene set in a fine-grained matrix containing microphenocrysts of euhedral oliv ine, monticellite, perovskite, spinel, apatite, calcite, ilmenite, mag netite, chromite and pyrite. The intergranular space is occupied by ph logopite, serpentite and carbonates. The major element chemistry of Ko takonda kimberlite, with low Niggili Si and high k and mg values and a lkali- and alumina-poor and cafemic-rich nature, matches well with tha t of kimberlite pipes 2,3,4 and 7 of Vajrakarur and kimberlites of Rus sia and Greenland. Its REE data agrees with that of 'basaltic kimberli tes' of south India. The Kotakonda and Maddur kimberlite occurrences, possibly representing the northern loci of kimberlitic activity of Vaj rakarur area, show a rise of + 10 mgl over the background value in the regional gravity picture and fall within the zone of intersection of NE-SW and NNW-SSE lineaments, which could be a manifestation of mantle uplift and crustal thinning, thereby opening a new vista for the sear ch of kimberlites.