- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
Diagnostic analcime-, heulandite-, and laumontite-bearing mineral assemblages from four areas in the upper Carboniferous and the Permian of New South Wales have been correlated with the rank of the associated coals, represented by the carbon content of vitrinite. The coals are high-volatile bituminous to semi-anthracitic; their vitrinites contain from about 82 per cent up to an estimated 91 per cent carbon. Analcime-quartz is found associated with the lower-rank, the laumontite-rich assemblages with the higher-rank coals. Comparison with a similar correlation in northern Yakutia (U.S.S.R.) indicates that diagnostic zeolites are not necessarily associated with coals of the same range of rank in different areas. Unlike the occurrence and stability range of burial metamorphic zeolitic assemblages, degree of coalification is probably independent of partial pressures of H 2 O and CO 2 ; it is controlled mainly by maximum depth of burial, its duration, and the geothermal gradient.