Abstract
Determining the origin of saline groundwater is crucial for effective water resource management and protection, clues for minerals and petroleum discoveries. Out of fifty three groundwater that were sampled and analyzed from part of the Middle Benue Trough, three are saline water which are discharge from folded and faulted sandstone of the study areas. Inductively Coupled Plasma Mass Spectrophotometer (ICP-MS) was used to analyze for the major cations and trace elements while titration was used for sulphate (SO4). Bicarbonate (HCO3) was also determined in the field by titration. Chloride (Cl) above 400mg/l and bromine (Br) were analyzed using the Ion Chromatographic Method (IC). Oxygen isotopes (δ18O) in water samples were analyzed via CO2 equilibration and hydrogen isotopes (δ2H) in water samples were analyzed by thermo-chemical reduction method. Three different statistical analyses; Piper trilinear diagram and Chadha plot, Cl/Br ratio, and isotopes plot were used to determine the origin of groundwater in the study area. Using Chadha’s plot, Cl/Br ratio, and isotopes plot, three origins were discovered as meteoric, mixed and marine. All the saline water in the study area are marine in origin and are associated with sandstone aquifer found in the Asu River Group and Awe Formations which are the oldest formations in the study area. In Nigeria, there is no work done on the use of Chadha’s plot and Cl/Br ratios to determine the origin of saline groundwater.

Key words: Key words: Origin, saline water, Middle Benue, Nigeria