The Pangidi Anorthosite Complex, Eastern Ghats Granulite Belt, India: Mesoproterozoic Sm-Nd isochron age and evidence for significant crustal contamination

The Pangidi Anorthosite Complex (PAC) is a small, magmaticaliy layered body emplaced into high-grade supracrustal rocks and metamorphosed together with the host rocks in the southern sector of the Eastern Ghats Granulite Belt, South India. It is dominated by coarse-grained anorthosite and leuconorite, minor leucogabbronorite and ultramafics with chromitites. The anorthositic rocks contain plagioclase (An(55-70)) + orthopyroxene (En(50-60)) + augite + amphibole + ilmenite + magnetite with accessory olivine, biotite, apatite and rarely coronal garnet related to metamorphic reconstitution. Despite a less calcic plagioclase composition in the anorthosites, the major and trace element distributions are akin to comparable litho, types (at similar SiO2 Wt%) of the Kondapalli layered anorthosite complex in close proximity. However, the PAC shows distinct effects of metamorphism and significant modal volume of secondary hydrous mineral phases unlike the latter. A five-point whole-rock Sm-Nd isochron gives 1739 +/- 220 million years (Ma) (2sigma) age for the complex, which constraints the, younger limit to its intrusion and probably metamorphism under amphibolite to granulite facies conditions. The PAC is characterized by strikingly low epsilon(Nd) ((at 1750 Ma)) of -14.4 +/- 3.7, indicating the importance of crustal contamination in its genesis possibly involving significantly older (Late Archaean) crustal components.