Chemistry of Halite and Potash Salt Cores, DSDP Sites 374 and 376, Leg 42A, Mediterranean Sea

Abstract

Two salt cores from Site 376 and two from Site 374 were analyzed. The salt core from Site 376 consists mainly of halite, which is associated with gypsum. The low bromine content of the halite (20-30 ppm) suggests a derivation through recycling. Sample 22-3, 24-30 cm from Site 374 contains halite in association with polyhalite, sulfoborite, sylvite, bischofite, and clay minerals. The bromine content in halite ranges from 114 to 218 ppm. The halite was precipitated with polyhalite from an evaporated seawater. The somewhat lower than standard bromine content in some cores suggests some contamination of the seawater by waters from continental sources. Sample 22-3, 107-130 cm from Site 374 contains halite in association with polyhalite and kainite. The average bromine content in halite is 320 ppm and in kainite is 830 ppm. The values are comparable to those obtained from analyses of salts in Sicily and in Calabria, and they suggest primary precipitation from evaporated seawater. The bromine profiles of both Site 374 cores show very abrupt changes. The pattern is consistent with our postulate, on the basis of our interpretation of the immediately overlying sediments, that the brine lake was not very deep when the halite and potash salts were deposited at Site 374.