Geological Analysis of Typical Geothermal Systems in East of China

ABSTRACT: Eastern China, which lies to the east of the Hu Huanyong Line that connects the Heihe and Tengchong areas, has a high population density, a developed economy, and a huge demand for energy. To determine the geothermal resources in eastern China, this study analyzed the typical geothermal systems in this region based on disciplines of structural geology, and petrology. As a result, this study determined the distribution patterns of medium and deep geothermal resources in this region. Eastern China is a superimposed region of three major global tectonic domains, namely Paleo-Asia, Circum-Pacific, and Tethyan. Its crust-mantle structure presents a special flyover pattern, while its shallow surface has alternating basins and mountains and well-spaced uplifts and depressions. Studies have shown that medium-high-temperature geothermal resources in China are mainly distributed in the Mesozoic-Cenozoic basins in eastern China. However, they are dominated by medium-temperature geothermal resources with low abundance. The geothermal reservoir types mainly include porous sandstone reservoirs, karstified fractured-vuggy carbonate reservoirs, and fissured granite reservoirs. 1. INTRODUCTION Eastern China, which lies to the east of the Hu Huanyong Line that connects the Heihe and Tengchong areas, consists of Northeast China, North China, the middle and lower reaches of the Yangtze River, Southwest China, and South China from north to south, has a high population density, hosting 96% of the total population of China, as well as a developed economy and a huge demand for energy (Fig. 1). As an earth-derived energy source, geothermal resources are clean, renewable, and highly competitive and can be used for indoor heating, industrial and agricultural utilization, and power generation. The successive launch of national projects in China, such as the Deep Resource Exploration and Exploitation Program, began the exploration of the deep earth in China, and important achievements have been increasingly achieved in basic geology and geothermal geology. Moreover, research on deep-crust temperature and crust-mantle dynamic mechanisms has been gradually intensified (Shi 1990; Xu et al., 1995; He et al., 2001; An et al., 2007; Wang et al., 2012; Qiu et al., 2015). Remarkable progress has been made in research on terrestrial heat flow (Jiang et al., 2016, 2019), geothermal system types (Chen et al., 1996; Zhang et al., 2017), the division of geotectonic units and geothermal units (Pan et al., 2009; He et al., 2017), the selection and evaluation of optimal exploration areas (He et al., 2020; Zhang et al., 2020; Ke et al., 2022), hot dry rock development experiments (Wang et al., 2022), and geothermal applications (Wang et al., 2014), laying a solid foundation for the study of deep geothermal resources.