DIRECTIONS OF ORE FLUID FLOW IN THE SOUTHEAST MISSOURI LEAD-ZINC DISTRICT AS INTERPRETED FROM ASYMMETRICAL DISTRIBUTIONS OF OREBODIES WITH RESPECT TO PRECAMBRIAN TOPOGRAPHY AND FROM MINERAL/METAL ZONING PATTERNS

One of the most interesting and controversial aspects of the Southeast Missouri Pb-Zn District is the problem regarding the directions in which the ore-depositing fluids flowed to enter the district. Previous investigators have appealed to fluid flow from the south, from the north, and a variety of other directions. The present investigation has examined the apparent ponding of the ore fluids behind Precambrian knobs and ridges as shown by the asymmetrical distribution of orebodies with respect to positive features in the Precambrian surface topography. The character of mineral and metal zoning patterns was further utilized to interpret directions of ore fluid flow to and within the district. Asymmetrical arrangements of orebodies with respect to Precambrian knobs and ridges at the Viburnum 27 mine, Indian Creek mines, Hayden Creek mine (Old Lead Belt), the northern portion of the Old Lead Belt, and an exploration area in the northern portion of the district indicate that the ore fluids that deposited those orebodies came from the northwest. The patterns of metal distribution at the West Fork and Fletcher mines in the Viburnum Trend are interpreted to indicate ore fluid flow from the west. The early deposited copper-rich ores were deposited along their west margins, later deposited zinc-rich ores were deposited in their central portions, and late iron-rich ores were deposited along the eastern margins of those orebodies. Lead mineralization was deposited throughout the zoning pattern. In the Old Lead Belt subdistrict the distribution of copper-rich ores suggest ore fluid flows from the northeast and northwest. Very locally within the Viburnum Trend, ore fluid flow was diverted back to the west. At the Magmont West mine, two miles west of the main Trend, mineral zoning suggests that the ore fluids moved westward from the main Trend. Similarly, orebody patterns with respect to a Precambrian knob at the Casteel mine indicate that part of the ore fluids that deposited that orebody moved westward. In summary, the principal direction of ore fluid flow to the district was from the northwest, but there also was fluid flow from the west to the Viburnum Trend and from the northwest to the Old Lead Belt.