The phosphates of Ecuador: characterization, genesis, and radiological implications
The Cretaceous Napo Formation in Ecuador contains a phosphate deposit of economic significance. The apatite in the phosphate deposit is a peloidal, fluorine rich carbonate fluorapatite, embedded in calcitic cement. It is a moderately substituted, reactive apatite with a unit-cell a-value of 9.334 A?. Sedimentary phosphates in E cuador were formed authigenically in discreet stages under anoxic conditions at the sediment-water interface, in a localized area. Chemical analyses using NAA and ICP-OE S revealed that Uranium and Rare Earth Elements are positively correlated with phosphorus indicating these elements are either incorporated into the apatite lattice, or adsorbed onto mineral surfaces. The uranium concentration of the Napo phosphate averages 100 mg kg-1, while the radioactivity ranges from 20 to 410 Bq kg-1. The overall radiation emanating from the static mine environment is 280.63 Bq kg-1 equating to a radiation dose of 1.85 mSv per year, resulting in a 0.01% risk of developing cancer.