Abstract: Base Metal Concentration in Density Stratified Evaporite Pan

P. Sonnenfeld, P. P. Hudec, J. A. Boon, A. Turek

The sediments and waters of a density and temperature stratified pond located on Los Roques Archipelago, Venezuela, have been analyzed for their base metal content of Mn, Fe, Cu, Pb, and Zn. The pond has an indirect connection to the open sea, and also received runoff from the nearby volcanic hills. As a result, the surface layer of water is enriched in the base metals as compared to sea water. Evaporation concentrates all metals until the concentration of gypsum precipitation is reached.

Upon precipitation, gypsum removes from 7 to 15 percent of the metals from solution, and contains 22.9, 12.1, and 58.4 ppm, on the average, of Zn, Cu, and Pb, respectively. The metal is also in part abstracted by the slowly settling particulate matter which collects in the deep part of the pond. The metal concentration of the bottom brine layers is approximately twice that of the surface layer.

It is suggested that upon conversion of gypsum to anhydrite under lithostatic pressure of burial the gypsum can serve as a source of metal-rich solutions.

AAPG Search and Discovery Article #90978©1975 GCAGS-GC Section SEPM Annual Meeting, Jackson, Mississippi