AUTHOR=Ren Qianhui , Li Binkai , Zhang Yan , Wu Haitao 

TITLE=Origin and evolution of intercrystalline brine in the northern Qaidam Basin based on hydrochemistry and stable isotopes

JOURNAL=Frontiers in Environmental Science

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2023.1106181

DOI=10.3389/fenvs.2023.1106181

ISSN=2296-665X

ABSTRACT=<p>The Kunteyi Basin, located in northern Qaidam, is known as a significant potash ore deposit in China. It is of great significance to study the origin of the potassium-rich intercrystalline brine to support the exploitation of potassium salts. In this study, the major ion concentrations and isotopic ratios (δ<sup>2</sup>H, δ<sup>18</sup>O, and δ<sup>11</sup>B) of intercrystalline brine were used to analyze the evolution of the brine. The results show that the intercrystalline brine has a much higher concentration of total dissolved solids compared with the oil-field brine. Most of the ions are enriched except Ca<sup>2+</sup> and Br<sup>−</sup>. The value of δ<sup>2</sup>H and δ<sup>18</sup>O are much negative while the δ<sup>11</sup>B values are positive. The analysis of <italic>C</italic><sub>Na</sub>/<italic>C</italic><sub>Cl</sub>, <italic>C</italic><sub>Br</sub>/<italic>C</italic><sub>Cl</sub>, Cl/(Na + K + Mg) and isotopes ratios, indicate that (1) Atmospheric precipitation is the primary source of water in brine; (2) The salinity of the brine is mainly influenced by halite dissolution; (3) The study area was influenced by the deep hydrothermal fluids. The thermal water recharged the Pleistocene layer, reacted with polyhalite, and formed Mg- and K-rich brine. The solution rose along the channel formed by the Shuangqiquan Fault and was supplied to the shallow intercrystalline brine.</p>