ORIGIN OF ARAGONITE IN A CONTINENTAL SALINE SEEP, NORTH QUEENSLAND

Aragonite, low-magnesian calcite, gypsum and halite were identified by X-ray diffraction and electron microbeam techniques in mineral precip itates near a salt seep 50 km southwest of Charters Towers in north Qu eensland. The chemistry of water from the creek and from the groundwat er at the salt seep shows that Mg:Ca ratios are greater than or equal to 1.5 throughout the year. The formation of halite and gypsum is due to evaporative concentration of the water at the seep and that of the carbonates, in particular aragonite, is probably due to a combination of evaporation and photosynthetic activity by diatoms.