The fate of diamondoids in coals and sedimentary rocks

Diamondoids were detected in the extracts of a series of coals and rocks varying in maturity, lithology, source input, and depositional environment. At the same maturity level, diamondoids are generally about a magnitude more abundant in source rocks than in coals. The concentrations of diamondoids are maturity dependent. However, while diamondoids become more abundant with the increasing thermal maturity, a diminution in diamondoid concentrations is observed at the maturity value of about Ro = 4.0% in both coals and rocks. The occurrence of diamantane destruction at 550 ??C during pyrolysis suggests that diamondoids may be eventually destroyed at high temperatures in the Earth. Here we propose three main phases of diamondoid life in nature: diamondoid generation (phase I, Ro < 1.1%), diamondoid generation and enrichment (phase II, 1.1% ??? Ro ??? 4.0%), and diamondoid destruction (phase III, Ro > 4.0%). ?? 2006 Geological Society of America.