Plate Tectonics and Geochemical Composition of Sandstones

Sandstones of the Paleozoic turbidite sequences of eastern Australia show a large variation in their major element geochemistry, reflecting the distinct sedimentary provenance and tectonic setting of each suite. On the basis of bulk composition, five suites are discriminated: Tamworth, Hill End, Hodgkinson, Bendigo, and Cookman. A close correlation exists between the geochemical composition of sandstones and tectonic settings of sedimentary basins. The nature of the continental margin and oceanic basins can be deciphered on the basis of the major element composition of sandstones. The most discriminating parameters are and . In general, there is a progressive decrease in , and an increase in and in sandstones from oceanic island arc to continental island arc to active continental margins to passive margins. Oceanic island arc sandstones are characterized by the high abundance of , and low and ratios. The continental island arc type sandstones can be distinguished from the oceanic island arc type by their lower and , and higher and . The active continental margin type sandstones are characterized by low and . Passive margin type sandstones are generally enriched in and depleted in , CaO, and , suggesting their highly recycled and matured nature.