Jg. Li et al., Methyl diamantane index (MDI) as a maturity parameter for Lower Palaeozoiccarbonate rocks at high maturity and overmaturity, ORG GEOCHEM, 31(4), 2000, pp. 267-272
Diamantanes were identified in extracts from the Lower Ordovician Majiagou
formations (Olms) of the central gas field, Shanganning Basin, China. At 31
00 3800 m, corresponding to R-o 1.9-3.9%, the MDI [methyl diamantane index
= 4-MD/(1-MD + 3-MD + 4-MD)] ranges from 40 to 65% for the source rock extr
acts. Changes in the MDI index in the very mature sections (R-o > 2.0%) are
relatively small and no linear correlation between MDI and R-o, or MDI and
depth, is noted, as previously reported, suggesting the possibility that t
he MDI may have limited applicability in maturity determinations. (C) 2000
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