Geology of the Brushy Creek Mine, Viburnum Trend, Southeast Missouri

Abstract

The Brushy Creek mine is located near the center of the Viburnum Trend along thewest flank of the Ozark Dome within the stable interior region of the continent.Sedimentation during Cambrian time was influenced by the rugged topography andoutlying islands of the Precambrian porphyries and granites. These structures brought about a prominent north-south fades strike within the host Bonneterre Formation consisting of open shelf, off-reef sands, algal reef, and back reef carbonates.Galena, sphalerite, and chalcopyrite mineralization is continous along the north-south belt with considerable variations in thickness, width, and grade. The ore occurs principally as banded disseminations, with some cross-cutting, and open-space fracture and breccia filling within the upper portion of the Bonneterre Formation. A north-south linear breccia trend occurs in the western margin carrying the better grade of mineralization.Ore localization appears to have been controlled largely by the existing permeability and porosity of the Bonneterre units. Fractures also played a prominent part in the localization of the ore as the galena often increases in grade and vertical extent where they cross the ore-bearing 5 zone oolitic grainstone units.