Chemical and isotopic signature of groundwater in the Santa Ninfa karst system and possible inferences on neotectonics

Abstract

The Santa Ninfa karst system is an area strongly controlled by tectonics, whose intense fracturing gave rise to the formation of a large number of cavities that foster the drainage of water. The hydrogeochemical characters of groundwater circulating in this aquifer, together with its isotopic signature, were investigated in detail. The chemistry of groundwater reflects the nature of the rocks hosting the aquifers, constituted by primary and diagenetic selenitic gypsum, salts, and gypsumarenite, whose dissolution is responsible of the geochemical fingerprint of the quasi-totality of the samples. A single site (CAM) is characterised by a different chemical composition, indicating a mixing between Ca-sulphate, Ca-bicarbonate and a NaCl-rich water. From the chemical point of view, no evidence of interaction between shallow groundwater and deep fluids has been detected.Conversely, isotopic fluctuations highlight mixing processes between surficial (evaporated) runoff and groundwater. Different mixing proportion among these endmembers can be reflected in variations of the chemical character of the sampled springs. Changes in mixing proportions can be the effect of differential permeability variations, in turn produced by local stress field changes during seismogenic processes. In this scenario the geochemical monitoring of the Santa Ninfa karst aquifer could be of relevant interest in the study of seismogenic processes in this area, with particular reference to the relationship between seismic and geochemical transients.

Bed Separation Formation Mechanism and Water Inrush Evaluation in Coal Seam Mining under a Karst Cave Landform

“…In such karst areas, groundwater seepage is complicated, and karst caves are developed in the karst area. Favara R [3] believes that the karst system is an area that is strongly controlled by structure, and the fault has formed favorable drainage holes; the researcher discusses the relationship between geochemical monitoring of the Santa Ninfa karst aquifer and earthquake seismic generating processes. Ivanik O [4] found that groundwater is guided by the bottom of the syncline, and made hydrological simulations of upwellings using a mathematical rainfall runoff model to obtain the law of water balance.…”