Potash cement in modern and ancient halite beds

Abstract

The occurrence of a potash salt cement in halite is a newly recognized feature of early (syndepositional) diagenesis of halite. The potash salt cement has been recognized in modern halite of the Qarhan salt lake playa of the Qaidam Basin, NW China, and in ancient halite of the Permian Teesside Group from Boulby, NE England. Syndepositional textures in ancient halite are normally very difficult to determine. The potash salt cement consists of carnallite and sylvite precipitated in dissolution cavities and fractures in halite. In the Boulby deposits, there is evidence for the incongruent dissolution of carnallite to form sylvite, a process which ultimately leads to the complete replacement of carnallite. In the Qarhan salt lake playa, the potash salt cement may have been precipitated through both the cooling of a surfacial residual brine and mixing of calcium chloride brine from deep fault/oil field with the interstitial brine in the halite.