Influence of tectonics on Permian coal-rank patterns in Australia

Abstract

Coal in the Australian Permian basins is dominantly subbituminous coal to medium-volatile bituminous coal. The subbituminous coal and higher-rank bituminous coals are generally the result of burial diagenesis. Localized low-volatile bituminous coal to anthracite is commonly associated with igneous activity. Extensive zones of high-rank coal in the eastern part of the Bowen Basin are due to uplift of deeply buried coal-measure sequences during Late Permian and Triassic tectonism. High-rank coals in the Sydney Basin are due to uplift of deeply buried Permian rocks preceding sea-floor spreading in the Tasman Sea during the Late Cretaceous and early Tertiary, although this conclusion is controversial. Localized semianthracite and anthracite at depths greater than 2,500 m in the Cooper Basin were formed either by enhanced heat flow from radiogenic basement granites or by vertical movement of hot fluids through the fractured granitic bodies during the Tertiary. Permian coals in the Pedirka and Arckaringa Basins in the center of the continent, and the Perth, Carnarvon, Canning, Bonaparte and Officer Basins in the west are generally low in rank due to either shallow depths of burial or slight heat flow, or both. The Fitzroy Trough of the Canning Basin is an exception; there significant tectonic activity has occurred since the Permian.