Bromine content and Br/Cl molar ratio of halite in a core from Laos: implications for origin and environmental changes

Autor: Gengxin Zhang, Zengjie Zhang, Minghui Li, Shurui Sun, Xiaomin Fang, Maodu Yan, Xiaoming Liu
Rok vydání: 2019
Předmět:
Zdroj: Carbonates and Evaporites. 34:1107-1115
ISSN: 1878-5212
0891-2556
Popis: Bromine (Br) is one of the trace elements in halite. Br content and the Br/chlorine (Cl) molar ratio can be used to reveal dry climates, the degree of evaporation, and/or brine concentration. The Br content of basal halite is more useful than that the Br content of halite from later stages when being used to distinguishing marine from nonmarine origins. Evaporite deposits on the Khorat Plateau (KP) have been a primary source of evaporites in southeastern Asia. The origin (i.e., marine, nonmarine, or a combination of the two) of these deposits is still disputed. In this study, we used the Br concentration of basal halite and the Br/Cl molar ratio to explore the origin of these deposits and the environmental changes that took place in the Late Cretaceous. We analyzed a total of 330 halite samples from borehole ZK2893 for cations (K+, Ca2+, Na+, and Mg2+) and anions (Br−, Cl−, and SO42−). The Br content ranged from 24.04 to 277.87 ppm, and the Br/Cl molar ratio ranged from 0.02 to 0.27 ppm. The low Br content (24.04 ppm) and Br × 103/Cl molar ratio (0.02) of the basal halite suggested that no marine water was in the basin when the halite precipitation began. The temporal variations in the Br content and the Br × 103/Cl molar ratio of halite implied that: (1) the climate in this area during the Late Cretaceous was dry, with two dry stages occurring from 92 to 85 Ma and from 80 to 72 Ma; and (2) the drying trend increased from 92 to 85 Ma and from 80 to 72 Ma, with two extremely dry events occurring during the periods 89–85 Ma and 76–73 Ma.
Databáze: OpenAIRE
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