The sedimentary structures of barite: examples from the Chaudfontaine ore deposit, Belgium



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The Chaudfontaine ore deposit is composed mainly of barite and hosted in Frasnian shale and carbonate formations of Belgium. Thirteen sedimentary structures involving barite crystals are described and discussed. Many of these structures appear to have developed under gravity control. The role of mechanical and chemical ore apposition processes are detailed in each case.

The study shows that two populations of barite were formed: (1) crystals which grew in brine above the water-sediment interface and (2) crystals which developed in the sediment during early diagenesis. The two modes of formation have specific sizes, habits and structures. Both populations crystallized under the control of the prevailing physico-chemical conditions, and the size and abundance of the barite crystals may be expressed as a function of the degree of barium supersaturation. High-energy currents and unstable sediment caused previously deposited crystals to be reworked. Morphological similarities were found between Chaudfontaine barite and gypsum from evaporites.