Geochemistry and origin of the dolostones from the Yuntai Mountain area, Shibing, Guizhou

The karast landforms in the Yuntai Mountain area, Shibing, Guizhou are dominantly made up of the Cambrian dolostones in which the dolomite contents come up to 90%, and display euhedral-subhedral crystals. The dolostones in this area have the contents of 30.4% for CaO, 21.7% for MgO and 72.4×10^-6 for the average of Sr contents with the Sr/Ba ratios of more than 1, and are characterized by low ΣREE (12.54×10^-6), slightly negative Eu anomaly, and right-leaning LREE-enriched distribution patterns. It is inferred that the dolostones were originated from the lagoon-subtidal environments within the restricted platforms with shallower water depths and weakly to moderate hydrodynamic environments, and xerothermic palaeoclimatic conditions. Influenced by the xerothermic climates, the pre-existing calcium carbonates were highly evaporated to give rise to the lagoon brines, and the seaward infiltration and seepage reflux of the brines finally resulted in the formation of the dolomites. It follows that the dolostones in the study area should be assigned to the near-surface replacement dolostones generated during the penecontemporaneous-early diagenetic stages.