Evolution of carbon systems vis-à-vis naturally occurring graphene in a graphite–gold interface
摘要
We report probably the second/third possible occurrence of the world and the first occurrence of natural graphene in India associated with graphite from the Paleoproterozoic Bhukia gold deposit, western India. Gold occurs in both native and lattice-bound invisible forms, closely associated with graphite and natural graphene. Graphene–graphite–gold interface is spatially and temporally associated with pyrrhotite, pyrite, magnetite, tourmaline and carbonates. Albitite and dolomitic marble predominantly host gold+graphite mineralization along with naturally occurring graphene, which is very rare in nature as most of the graphene so far obtained or recovered is in synthesized form except their natural occurrences in the Coosa provinces in Alabama, USA; Sheba Gold mine in Barberton area, South Africa and in the ancient meteorites. Two types of graphitic phases are found in the mineralizing system: (i) as flaky sheet-like and (ii) as lath-shaped along with graphene. Distribution patterns and association of the graphite+graphene grains with sulfides suggest possible hydrothermal precipitation of the graphite, which is coeval with gold mineralization and has a primordial biogenic precursor. Presence of naturally occurring graphene may throw some light on the evolution of life during Precambrian time, and also for understanding the hitherto lesser known high-technology carbonic phases.