Constraints of major ions and arsenic on the geological genesis of geothermal water: Insight from a comparison between Xiong'an and Yangbajain, two hydrothermal systems in China. (June 2020)

• Record Type: Journal Article
• Authors: Guo, Qinghai; He, Tong; Wu, Qifan; Liu, Mingliang
• Is Part Of: Applied geochemistry. Volume 117(2020)
• Publication Date: 2020-06
• Subjects: Geothermal water -- Hydrochemistry -- Arsenic -- Magmatic heat source -- Geological genesis; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2020.104589
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: Hydrochemical similarities are shared by the geothermal waters from Xiong'an, a typical non-magmatic hydrothermal system, and Yangbajain, a typical magmatic hydrothermal system. Both systems are primarily discharging chloride- and sodium-rich geothermal waters with similar TDS values. However, the hydrochemical investigations made in this study show that the chloride in the Xiong'an geothermal waters originates mainly from the mixing of deep saline waters, while that in the Yangbajain geothermal waters is basically of magmatic origin, like many other magmatic hydrothermal systems hosted by felsic rocks worldwide. In contrast to chloride, the concentrations of arsenic in the geothermal waters from Xiong'an and Yangbajain differ greatly. The higher arsenic concentrations of the Yangbajain geothermal waters are attributable to the much greater reservoir temperatures in Yangbajain, and possibly, the input of magmatic fluids to the Yangbajain reservoirs. The contents of arsenic in reservoir rocks, instead, don't seem to be an important factor controlling the geothermal arsenic concentrations. Leaching of arsenic from arsenic-rich sandstone or carbonate rocks at relatively low Xiong'an reservoir temperatures should be much less than that from arsenic-poor granitic rocks at higher Yangbajain reservoir temperatures. The results obtained in this study indicate that arsenic coupled with other hydrochemical constituents can be used as a useful tool to identify the geological geneses of geothermal waters. Highlights: Xiong'an and Yangbajain are typical non-magmatic and magmatic geothermal systems, respectively. Arsenic contents in the studied geothermal waters are mainly controlled by their temperatures. Arsenic contents in reservoir rocks are not positively related to those in geothermal waters. Magmatic fluid input likely contributes to arsenic enrichment in Yangbajain geothermal waters.