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 stri king Salem-Attur deep fault zone which represents the eastern extention of the Moyar fault in the southern granulite terrane of India X-ray diffractio n, FTIR spectroscopy and chemical analyses show calcite, ankerite, siderite and benstonite as dominant minerals besides minor apatite and green biotit e. Whole rock compositions show enrichment of light REE, Ba, Sr and Nb. C a nd O isotopic data determined for calcite (delta C-13= -4.9 to -5.1 parts p er thousand V-PDB and delta O-18 = 9 to 9.2 parts per thousand V-SMOW) poin ts to a mantle origin. The chemical characteristics therefore suggest that the carbonate veins have carbonatitic affinity. The FTIR spectra provide ev idence for presence of H2O and CH4 in addition to CO2 in the carbonate mine rals of these veins.