Regional Variations of River Water Composition Resulting From Halite Solution, Mackenzie River Drainage Basin, Canada

Abstract

The composition of surface waters in the Mackenzie River drainage basin falls into three general groups: (1) rivers entering the Slave‐Mackenzie system from the west which have sum‐of‐constituents 100–200 mg/1 and chloride in the range < 1 mg/1 in their headwaters to 2–5 mg/1 at their mouths; (2) surface waters on the Canadian Shield which have lower sum‐of‐constituents (<100 mg/1) and chloride (<1 mg/1); and (3) the Slave and Mackenzie rivers and the Great Bear and Great Slave lakes, which have sum‐of‐constituents 100—200 mg/1 and chloride 5–10 mg/1. Hydraulic head cross sections with evidence of solution collapse structures and anomalous depositional thicknesses indicate extensive solution of Middle Devonian halite and movement of the resulting brines to discharge areas at the principal Devonian outcrop near the Slave River. Chemical and isotopic analysis of saline springs in the discharge area confirms an origin by solution of halite (and gypsum) by meteoric water.