Tk. Rao et Kj. Sarma, A NEW OCCURRENCE OF KIMBERLITE NEAR KOTAKONDA, MAHBOOBNAGAR DISTRICT,ANDHRA-PRADESH, Journal of the Geological Society of India, 43(1), 1994, pp. 75-85
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.