Mineralogical and Geochemical Study on Carbonate Veins of the Salem-Attur Fault Zone, Southern India: Evidence for Carbonatitic Affinity

Carbonate veins up to few metres thick have been recognised in the E-W striking Salem-Attur deep fault zone which represents the eastern extention of the Moyar fault in the southern granulite terrane of India. X-ray diffraction, FTIR spectroscopy and chemical analyses show calcite, ankerite, siderite and benstonite as dominant minerals besides minor apatite and green biotite. Whole rock compositions show enrichment of light REE, Ba, Sr and Nb. C and 0 isotopic data determined for calcite (δ¹³C= -4.9 to -5.1%0 V-PDB and δ¹⁸0 = 9 to 9.2%0 V-SMOW) points to a mantle origin. The chemical characteristics therefore suggest that the carbonate veins have carbonatitic affinity. The FTIR spectra provide evidence for presence of H₂0 and CH₄ in addition to CO₂ in the carbonate minerals of these veins.