Detecting hydrothermal graphite deposition during metamorphism and gold mineralization

Fourier Transform IR analyses of carbonaceous material from the Otago and Alpine Schists and the Macraes gold deposit of the South Island, New Zealand, show the progressive effects of graphitization during metamorphism and suggest that the majority of carbonaceous material identified at the Macraes deposit precipitated from hydrothermal fluids. Given that the distinction of sedimentary carbonaceous material from fluid-precipitated graphite is a key to better understanding the redox state of crustal rocks, ore depositional processes and the extent of carbon cycling in the crust, this study highlights the importance of IR spectroscopy in the characterization of reduced carbon-bearing rocks.