GEOCHEMISTRY AND ORIGIN OF FORMATION WATERS IN WESTERN CANADA SEDIMENTARY BASIN .2. ALKALI METALS

The population statistics for Cl, Br, I, HCO3, SO4, Na, Ca, Mg, K, Rb, Li, Sr, Mn, Zn, Fe, Ni, Co, Cr and Cu in formation waters from the western Canada sedimentary basin are presented, together with weighted, mean composition. Five types of formation waters are present in the basin but only two are considered in detail: (1) a membrane-concentrated formation water; and (2) a formation water formed either by mixture of #1 and very small amounts of bitterns resulting from halite precipitation or by hyperfiltration. Investigation of the alkali metals indicates that the membrane is selective and leads to a relative concentration pattern in the solution of: Rb > K > Na > Li. The movement of alkalies through the filter is primarily by site-hopping and the relative rate is controlled by the ion's ease of replacibility in the order: Li > Na > K > Rb. The composition, and thus ionratios, are set by mineral-solution reactions, particularly during early diagenesis. Modification of the composition then occurs by selective filtration, further chemical reaction, and mixing during the subsequent fluid migration resulting from hydrodynamic drive. © 1969.