Geology of the B-baseline zone, Walton barium-copper-lead-zinc-silver deposit, Nova Scotia.

The Walton Ba-Cu-Pb-Zn-Ag deposit, Nova Scotia, is hosted by Visean-aged carbonate rocks of the Macumber Formation and its associated breccia. The Macumber Formation in the Walton area is divided into two units, the lower Macumber, a laminated carbonate 30-40$\sp\prime$ thick and the upper Macumber, a synsedimentary slump breccia that forms two mounds up to 70$\sp\prime$ thick. Outside the immediate mine area the carbonate is either limestone or dolostone; the Macumber Formation surrounding the deposit has been altered by hydrothermal fluids to manganiferous siderite. Based on barite and metal content two main ore types were defined. Type I comprises barite and variable sulphide contents, whereas Type II comprises only sulphides. Type I ore forms a stratiform sheet which straddles the upper Macumber/lower Macumber contact and contains lenses of Pb-rich and Cu-rich ore. Type II ore is most commonly associated with the upper Macumber mounds where it forms a large pod which cuts the Type I ore zone. The host stratigraphy is presently steeply dipping and faulted, both of which are considered to be post-ore events. The Walton deposit probably formed when uplift of the Cobequid Highlands in the late Namurian initiated gravity-driven flow of basinal fluids through a basal aquifer within the Horton Bluff Formation. The hot fluids flowed south toward the basin margin and leached salts and metals from the aquifer. In the Walton area these fluids were released, along faults, into the overlying Macumber carbonate and synsedimentary carbonate breccia, replacing them initially with manganiferous siderite. (Abstract shortened by UMI.