Comparative study of lamprophyres from the Cuddapah intrusive province (CIP) of Andhra Pradesh, India

Tbe mid-Proterazoic lamprophyric rocks broadly represented by kimberlites, lamproites and lamprophyres (sensu stricto) are emplaced in and adjacent to the intracratonic Cuddapah basin in the eastern Dharwar craton of India wh ich was recently recognized as the Cuddapah (intrusive) province (CIP). Whi le the kimberlite pipes and lamprophyre dykes are located outside but close to the western and eastern margins of the Cuddapah basin respectively, the lamproites are hosted within the basin. Lamprophyres occur in seven locati ons of the Prakasam district of Andhra Pradesh. Elchuru, where more than on e hundred lamprophyre dykes are found, represents a prominent centre of lam prophyre magmatism. Purimetla comes next to Elchuru with a tally of twenty lamprophyre dykes. At other places lamprophyres are numerically insignifica nt. The CU? lamprophyres encompass different varieties and they cut across an equally wide-ranging variety of host rocks; these lamprophyres come unde r 1) feldspathoidal or non-feldspathoidal and 2) plagioclase- or orthoclase -bearing categories. With a single exception, all the lamprophyres are mica ceous and distinctly alkaline. The genesis of CIP lamprophyres as a manifes tation of alkaline magmatism is discussed.