X-ray Diffraction, Infrared and Isotope Study of the Lakadong Limestone, Meghalaya

X-ray diffraction (XRD) and infrared (IR) spectral analyses of the Lakadong Limestone, Meghalaya indicate calcite as its dominant mineral phase. Association of dolomite at the base and presence of silica at the top of the sequence is evidenced from the spectra. A significant relationship between CaO content and the peak intensity of IR-spectra is found and needs standardisation before it can be utilised for rapid estimation of quality of limestone and can be an alternative for different time consuming analytical procedures. Stable isotope of δ¹³C {0.63 to 1.12‰( av.0.87±0.01‰)} points to enrichment of heavier C isotope and δ¹⁸O values {-7.34 to-10.55‰ (av.-9.06±0.01‰) ) to lighter O isotope enrichment. Isotopic grid analysis confirms the marine origin for the limestone. Biochemical fractionation along with diagenetic reorganisation might have played critical roles in controlling the isotopic ratios of this limestone.