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Early-diagenetic aluminophosphate minerals (mainly florencite) are ubiquitous in ancient (Archean to Cretaceous) marine-deposited sandstones. The crystals are >10 μm in diameter and are mostly associated with thin coatings or pockets of detrital clay particles lining quartz grain surfaces. Aluminophosphate crystals are also found in altered detrital aluminosilicate grains (e.g. feldspar).

The aluminophosphate minerals precipitated in sands deposited in shallow marine environments. Diagenetic textures and the presence of structural sulfate in the aluminophosphate minerals suggest that the authigenic crystals formed shortly after deposition, probably in the zones of sulfate reduction and methanogenesis. The aluminophosphate minerals formed as the concentrations of phosphate in the pore water increased and phosphate combined with various cations (e.g. calcium, barium, rare earth elements) to precipitate at sites of aluminum availability (e.g. detrital clay particles and aluminosilicate grains).

Although the aluminophosphate minerals are volumetrically minor constituents (<0.05 wt%), the authigenic crystals, which are present in >90% of samples studied, are spatially and temporally widespread in ancient Australian sandstones. Burial flux estimates show that phosphorus is removed at a rate of ~5.6 × 10-7g/cm2-yr. This value suggests that aluminophosphate precipitation was probably an important sink for oceanic phosphorus in the past, and possibly significant in present-day coastal environments. The discovery of the magnitude of the authigenic aluminophosphate sink has implications for models of the marine phosphorus cycle.

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