Original paper

Controls of evolution of mineral assemblages in ultrahigh-temperature metamorphosed Mn-carbonate-silicate rocks from the Eastern Ghats Belt, India

Mukhopadhyay, Subir; Roy, Supriya; Fukuoka, Masato; Dasgupta, Somnath


A unique suite of Mn-silicate-carbonate rocks from the Eastern Ghats Belt, India, were metamorphosed under ultrahigh temperatures and exhibit contrasting mineral assemblages in closely spaced domains. Development of contrasting assemblages under isothermal-isobaric conditions is attributed to initial variations in fluid composition particularly aCO2, and bulk-rock Mn:Mg:Al:Si:Ca ratios. The fO2 was buffered near the QFM buffer during peak metamorphism. Garnet shows a sharp increase in Fe+3 content towards the rim, which is interpreted to be the result of increased aCO2 during later stages of evolutions of the rocks due to channelled fluid flux. At the terminal stage of evolution, the rocks suffered hydration at lower temperatures.


mn-silicate-carbonate rocksultrahigh-temperature metamorphismbulk compositional controls