Origin and Circulation of Springs in the Nangqen and Qamdo Basins, Southwestern China, Based on Hydrochemistry and Environmental Isotopes

Xiwei Qin,Weiliang Miao,Xiasong Hu,Xiying Zhang,Sha Yang,Wenhua Han,Qian Song,Haizhou Ma,Mei Wu,Huaide Cheng,Guorong Li,Jibin Han,Yongshou Li,Maurizio Barbieri

doi:10.1155/2022/7190994

Abstract

The Nangqen and Qamdo (NQ-QD) basins in China have very rich geothermal and brine resources. The origin and spatiotemporal evolutionary processes of its hot and saline springs however remain unclear. Geochemical and isotopic (18O, 2H, 3H) studies have therefore been conducted on the water from the geothermal and saline springs in the NQ-QD Basin. All saline springs in the study area are of the Na-Cl geochemical type while geothermal waters show different geochemical types. The oxygen and hydrogen isotopic compositions of the springs in the NQ-QD Basin are primarily controlled by meteoric water or ice-snow melt water and are influenced by rock-water interactions. It is found that the saline springs in the study area are derived from the dissolution of halite and sulfate that occur in the tertiary Gongjue red bed, while the hot springs in the QD Basin are greatly influenced by the dissolution of carbonatites and sulfates from the Bolila (T3b) and Huakaizuo (J2h) formations. Results from silica geothermometry and a silicon-enthalpy hybrid model indicate that the apparent reservoir temperatures and reservoir temperatures for the hot springs in the QD Basin range from 57–130°C to75–214°C, respectively. Deuterium analysis indicates that most of the hot springs are recently recharged rain water. Furthermore, the saline springs have a weaker groundwater regeneration capacity than the hot springs. Tritium data shows that the ranges of calculated residence times for springs in this study are 25 to 55 years, and that there is a likelihood that hot springs in the QD Basin originated from two different hydrothermal systems. The geochemical characteristics of the NQ-QD springs are similar to those of the Lanping-Simao Basin, indicating similar solute sources. Thus, the use of water isotope analyses coupled with hydrogeochemistry proves to be an effective tool to determine the origin and spatiotemporal evolution of the NQ-QD spring waters.

Highlights

Hot and saline springs usually refer to springs that form due to the emergence of geothermal resources or saline minerals from the earth’s crust
The spring waters had a wide range of salinities (32.74~327.44 g/L for saline springs, 0.33-2.43 g/L for hot springs, and 0.4-1.72 g/L for river waters)
From the δ18O-δD plot (Figure 5), it is seen that all the spring samples collected from the Nangqen and Qamdo basins fall near the global meteoric water line (GMWL) [17], the China meteoric

Summary

Introduction

Hot and saline springs usually refer to springs that form due to the emergence of geothermal resources or saline minerals from the earth’s crust. To further the understanding of such resources, spring waters can provide significant information about evaporite deposits and geothermal processes in the subsurface because of their halite dissolution and thermal conductivity. Geofluids many evaporite deposits (halite, gypsum, aragonite, dolomite, and magnesite deposition) and saline springs [1, 2], and it is rich in geothermal resources which are mainly distributed in Dingqing, Chaya, Basu, Zuogong, Markam, and Qamdo counties. Detailed hydrochemistry and isotopic characteristics have rarely been described to assist in understanding the origin and spatiotemporal evolution process of hot and saline springs in the study area. The aim of this study is, to better describe the genesis, circulation, reservoir temperature, residence time, and spatiotemporal evolution of the hot and saline springs in the NQ-QD basins of China using new hydrogeochemical and water isotope techniques

Objectives

Results

Conclusion