Stable isotope study of metacarbonate rocks from western Mongolia: Implications for fluid-rock interaction processes in the Central Asian Orogenic Belt

抄録

Mineralization in tectonically active orogenic belts is basically controlled by the movement and activity of fluids. Central Asian Orogenic Belt (CAOB) is a fertile region for mineralization because it consists of several subduction and accretion related metamorphic and magmatic complexes formed between 1000 Ma and 250 Ma, where fluid-rock interaction processes are expected. We present here preliminary data on the carbon and oxygen stable isotopic composition as well as strontium isotope and trace element characteristics of metacarbonate rocks from the several localities in the CAOB. Metacarbonate rocks occur as relatively thin layers intercalated with pelitic and psammitic gneisses, which can be broadly grouped into two categories based on carbon and oxygen isotopic composition. (1) Metacarbonate rocks that preserve pre-metamorphic stable isotope signatures, and (2) those affected by fluid-rock interaction processes during metamorphism and mineralization events. In our presentation, we compare and contrast the geochemical characteristics in mineralized and non-mineralized layers of metacarbonate rocks from selected localities in western Mongolia.