A Note on Oxygen and Carbon Isotopes of Magnesite and Dolostone of Mesoproterozoic Gangolihat Dolomite (Formation), Pithoragarh District, Uttar Pradesh

Nine samples of sparry magnesite and five samples of dolostone of the Mesoproterozoic Gangolihat Dolomite (Formation) of the Chandak area, Pithoragarh are analysed for stable isotopes of carbon and oxygen. δ¹⁸O for dolostone varies from -10.8‰ to -9.0‰ (SMOW) with mean as -10.1‰ (SMOW) and for magnesite it varies from -16.8‰ to -11.8‰ (SMOW) with mean as -14.0‰ (SMOW). δ¹³C for dolostone varies from -1.6‰ to 0.6‰ (PDB) with mean as -0.0‰ (PDB) and for magnesite it varies from -2.2‰ (PDB) to 0.1‰ (PDB) with mean as -1.0‰ (PDB). Thus, magnesite and dolostone show distinctly different isotopic signatures and hence magnesite must have formed from isotopically different fluids than those which produced dolostones. Magnesite is not syndepositionally produced but must have formed at some later stage by hydrothermal solutions.