Rare Earth Element Geochemistry of the Kondapalli Layered Complex, Andhra Pradesh

Tiie Kondapalli Layered Complex (KLC) is a minor mafic-ultramafic intrusion occurring in the charnockitic region of the Eastern Ghats Mobile Belt (EGMB). it consists dominantly of gabbroic and anorthositic rocks, with subordinate ultramafic rocks (orthopyroxenite, websterite, cliriopyroxenite, harzburgite and dunite), which are associated with chromitite. The components of the KLC are grouped into two series: (1) Chromitite-Ultramafic Rock Series (CURS), and (2) Gabbro-Anorthosite Layered Series (GALS); some mafic gabbros belong to CURS. A profound petrological and geochemical hiatus exists between the primitive CURS and evolved GALS, which constitute a regressive intrusive sequence, it is shown that the REE abundances and chondrite-normalized patterns of 27 rocks from the KLC are controlled by the dominant cumulus minerals and variable amounts of trapped melt. The cumulate anorthositic and gabbroic rocks of the GALS are classified into those showing (1) positive Eu anomaly (An I and Gb I), (2) no Eu anomaly (An II and Gb II), and (3) negative Eu anomaly (Gb III). The whole-rock REE compositions possibly record the evolution of the "associated" liquids. Calculated associated liquid compositions, when viewed in conjunction with the available mineralogical, petrological and geochemical data of CURS and GALS, strongly suggest a two-magma genesis for the Kondapalli Layered Complex.