Origins of the Mid-Cretaceous evaporite deposits of the Sakhon Nakhon Basin in Laos: Evidence from the stable isotopes of halite

摘要

The origins of the evaporite deposits of the Khorat Plateau remain disputed. Based purely on the known evolution of the Khorat Plateau, materials of marine origin and/or remnant seawater should be present, but instead the salt layers of the deposits found there present typically continental lithological features. New data suggest that the Laotian evaporite deposits can be dated to the Middle to Late Cretaceous. In this paper we present the sulfate delta S-34 (5.2% to 15.6%) and delta O-18-(SO4) (10.3% to 14.1%) records, Sr isotopic compositions (0.707443 to 0.708587), delta O-18(-inclusion) (-7.1% to 13.9%) and delta D-inclusion (-72% to -150%) records and the trace metal elements for halite deposits extracted from Core ZK2893 in the Sakhon Nakhon Basin, Laos. These values suggest that the deposits are of continental and hydrothermal origins with trace marine remnants. Evaporites in the basins are very likely to have been formed originally by the evaporation of seawater, prior to being dissolved in meteoric water and hydrothermal fluid, and subsequently precipitated.