Water yield property and water storage structure of magmatic fracture structure in the northern Huangshan area

The Northern Huangshan area is located at the junction between Jiangnan orogenic and fault-fold structural belt of the southern Anhui Province, and its outcrop is Taiping granodiorite of Late Jurassic and Huangshan granite of Early Cretaceous. The structure activity of comagmatic or post-magmatic was intensive, and the nearly north-south fracture and north-west fracture was well-developed, which controlled the drainage system distribution. Massive intrusive rock was in poor water yield property in the study area, so the remote sensing hydrogeological interpretation, geological surveying, electrical profiling measurement, and hydrological test borehole for verification were conducted to find the location of single well with water inflow of more than 240 m³/d. The water-bearing characteristics and groundwater storage structures of the faulted structures in the study area were basically clarified. Through surface investigation, the authors found that the study area has developed weathering reticulate jointing, dip-slope unloading jointing, diagenetic jointing, and structure jointing, which were the main channels for groundwater to receive recharge from surface water and precipitation. Besides, the low resistance anomalies were identified through electrical profiling measurement, and the hydrological test holes were implemented. It is recognized that the tensile fractures and normal transecting fractures in the northern Huangshan area had medium permeability through borehole verification, and those fractures were water-conducting structures. Hydrological test holes could be placed at the intersection of more than two sets of directional fractures or at the intersection of fractures and rock veins. The authors in this research recognized that the intersection of multiple sets of directional fractures, low-lying terrain fracture intersections with dike rock, and water-blocking structures were favorable locations for water exploration. The water yield property of the contact zone between different lithology types in the study area was weak, and water yield property was middle for depression weathered belt type, fracture structure models type and dike type. And the water-bearing structure with the superposition of the three types had good water yield property. These research results could provide technical references for further exploration of groundwater resource and its rational utilization in Huangshan area.