Preprint SME Annual Meeting Mar. 27-Mar.29, 2006, St. Louis, MO

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1 Preprint DIRECTIONS OF ORE FLUID FLOW IN THE SOUTHEAST MISSOURI LEAD-ZINC DISTRICT AS INFERRED FROM ASYMMETRICAL DISTRIBUTIONS OF OREBODIES AROUND PRECAMBRIAN KNOBS AND FROM MINERAL/METAL ZONING PATTERNS R. D. Hagni, Univ. of Missouri-Rolla, Rolla, MO Introduction The ore deposits of the Viburnum Trend in the Southeast Missouri Lead District constitute the world's largest lead producing district. Six or seven mines currently are in production in the Viburnum Trend. The principal minerals are few in number, simple in composition, and form simple superposition and replacement textures. The economically valuable minerals in the typical lead-zinc ores of the Viburnum Trend are the sulfides, galena, sphalerite, chalcopyrite, and siegenite. The most abundant gangue minerals are dolomite, marcasite, pyrite, calcite, quartz, and dickite. Four concentrates, lead, zinc, copper, and cobalt are produced from the ores, and they contain an interesting suite of trace elements, of which silver and cadmium are recovered at the smelter and refinery. 1 Emphasis is given here to the variations in directions of ore fluid flow based upon interpretations of the positions of orebodies due to the ore fluids being impeded by Precambrian basement relief and upon patterns of ore mineral/metal zoning. The Precambrian basement relief and Lamotte Formation pinchout has exerted an important control upon the specific locations of orebodies in the Southeast Missouri Lead District. The locations of some orebodies along one side of Precambrian knobs or ridges strongly suggests that they are positioned on the side from which the ore fluids flowed. Other orebodies are located in positions that suggest that they formed where the ore fluids passed around or between Precambrian knobs. Patterns of mineral and/or metal zoning have been used in many mineral districts to interpret the directions of ore fluid flow. The mineral/metal zoning pattern correlates closely with that of the mineral paragenesis. The earliest deposited minerals tend to be deposited nearest to the source, the later deposited minerals next closest to the source, and the latest deposited minerals furthest from the source. In the Southeast Missouri Lead District, it is interpreted here that the early-deposited copper-rich ores are closest to the source of the ore fluids, the subsequently-deposited zinc-rich ores are next closest to the source, and iron-rich ores are furthest from the source. PREVIOUS INTERPRETATIONS OF DIRECTIONS OF ORE FLUID MOVEMENT One of the most interesting and controversial aspects regarding the genesis of the ore deposits in the Southeast Missouri Lead District is that of the direction or directions in which the ore fluids moved into and through the district. An almost limitless variety of ore fluid movement directions have been proposed by various previous investigators. This section briefly reviews the principal interpretations of previous investigators and the geological features that were utilized to indicate directions of ore fluid flow. The following section provides interpretations of fluid flow directions for ten selected mine and exploration locations in the Southeast Missouri Lead District. The most prominent idea has been that the ore fluids were derived from the Arkoma Basin to the south in Arkansas and Oklahoma, that they were either squeezed out by compaction or driven out by local uplift, and flowed northward to the Southeast Missouri Lead district. 2,3,4 The strongest evidence in support of this interpretation has come from the fact that published data on fluid inclusion filling temperatures for sphalerite indicate a gradual decrease in average temperature from the Northern Arkansas district at the south through the Tri-State District and Viburnum Trend to the Central Missouri Barite District at the north. 2 However, consideration of all available data, published, semi-published, and unpublished, indicates no significant difference in average sphalerite fluid inclusion filling temperatures between the main three districts/subdistricts: Northern Arkansas, Tri- State, and Viburnum. 5 One approach to an understanding of directions of ore fluid movement has been through studies of mineral asymmetry. 6 Asymmetrical ore and gangue mineral coatings are common in the Viburnum Trend. Early octahedral galena, the main lead-deposing stage, has been coated by crystals of sparry dolomite, late chalcopyrite, marcasite, pyrite. Late-stage cubic galena has been coated by late quartz. The directions of those coatings typically indicate an apparent downward motion of the fluids ("snow-on-the-roof" texture), but locally close examination reveals lateral or horizontal asymmetry A study of about 300 specimens at 66 locations in six mines in the Viburnum Trend suggested that the main ore fluids entered the Trend in the vicinity of the Magmont and Buick mines and flowed both to the north and south from those mines. 7,8 There also appeared to be another contribution of fluid from the south at the Sweetwater mine at the south end of the trend. In support of the interpretations from mineral asymmetry, both the amounts and the ratios of cobalt and nickel have appeared to indicate similar directions of ore fluid flow in the Viburnum Trend. 9,10 The average amounts of cobalt and nickel are highest at the Magmont and Buick mines in the north-central portion of the Trend, and they decrease both to the north and to the south. Copper shows variations that are similar to those of cobalt and nickel. The ratio of nickel to cobalt also increases from the Magmont-Buick mines toward the north and south. The amounts of cobalt and nickel are even greater in the Fredericktown subdistrict located to the south of the Old Leadbelt subdistrict. Those metals are about ten time more abundant than in the Old Leadbelt and Viburnum subdistricts. This aspect has been interpreted to suggest that the source of the ore fluids lies to the south of the Old Leadbelt and Fredericktown subdistricts, that the cobalt and nickel were derived from mafic intrusions in the Reelfoot Rift, and that the flow of the ore fluids were structurally controlled by lineaments leading northwestward from the Reelfoot Rift to the lead district. 11 A study of trace element contents of dolomite in the Bonneterre Basal Dolomite at the base of the Bonneterre Formation revealed systematic variations within the Viburnum Trend that contrasted with those outside the trend. 12 The amounts of iron and manganese in dolomite decrease southward within the trend and, by contrast, they decrease northward outside the trend. Strontium variations were the opposite as those of iron and manganese. These variations were interpreted to indicate that although there was a system of northerly fluid movement throughout much of southern Missouri, ore fluid flow within the trend was southerly. Variations in crystal habit also have been used to interpret directions of ore fluid flow in the Southeast Missouri barite and lead districts. In the Washington County barite district, Wagner 13,14 outlined east-west trending fault-controlled ore runs by variations in the crystallinity of barite. Very coarsely crystalline barite occupied the centers of the runs adjacent to faults, coarse to medium crystalline barite formed intermediate positions, and finely crystalline barite occurred in the outer portions of the runs. Interestingly, in the Viburnum Trend, Morris 15 found the opposite relationship, that the finer sulfide crystals formed in the inner portions of ore runs and coarser 1 Copyright 2006 by SME

2 crystals defined the outer margins of the runs. In an effort to further use galena crystal habit as a means of defining ore fluid flow in the Viburnum Trend, Sun et al. 16 carefully measured the degree of cubic modification of 400 octahedral galena crystals from 103 locations in the Sweetwater mine. The galena crystals were classified into ten groups of varying octahedron:cube development. The locations of the ten types outlined linear northwest and northeast trends with increasingly greater cubic modification as the fluids flowed along the fracture channels and moved laterally from the source channels. DIRECTIONS OF ORE FLUID MOVEMENT INTERPRETED FROM OREBODY POSITIONS RELATIVE TO PRECAMBRIAN TOPOGRAPHY AND METAL ZONING PATTERNS For the purposes of the present study of possible directions of ore fluid movement, eight areas in the Southeast Missouri Lead District were considered with respect to the positions of orebodies with respect to Precambrian ridges and knobs and with respect to areal mineral/metal zoning patterns. Where the ore fluids had a considerable horizontal component and were impeded by structures in the paths of their movement, the ore fluids may be deflected around those impediments and provide a clue to the directions of their movements. In the Southeast Missouri Lead District this relationship is most readily observed where the ore fluids have been impeded and deflected around Precambrian knobs and ridges. Areal patterns of mineral and/or metal zoning can also reveal directions of movement of the ore fluids that deposited those minerals. Early deposited copper-rich ores were deposited closer to the source than the later deposited lead and zinc sulfides. Even later deposited sulfides typically were deposited further from the source. In the Southeast Missouri Lead District, copper-rich chalcopyrite ores mark the portion of the orebody toward the direction from which the ore fluids came, whereas iron-rich marcasite and pyrite ores mark the portion of the orebody furthest from the source. The application of these principles to eight selected areas provide some interesting insight into potential directions of ore fluid movements in the district. Viburnum 27 Mine, Viburnum Trend The relationship between ore deposit distribution and Precambrian ridges is especially well shown at the Viburnum 27 mine in the Viburnum Trend. 17 Two relatively high Precambrian ridges, which are about 2000 feet long and arranged crudely in an east-west direction, have served to constrain the southwestward flow of the ore fluids. The ore deposit was deposited on the north and west sides of the two ridges. The deposit also extends to southward where the ore fluids passed between the two ridges (Fig. 1). These spatial relationships indicates that the ore fluids at the Viburnum 27 mine were flowing in a south to southeast direction. Exploration in the Palmer Area, Northwest of the Viburnum Trend A second area in which spatial relationships between lead-zinc mineralization and a Precambrian ridge provide evidence for the direction of ore fluid movement is that of an area of exploration by the Doe Run Company in the Palmer area to the north-northwest of the Viburnum Trend. 18 Where a lead-zinc mineralized trend from the westnorthwest was impeded by a northeast-trending Precambrian ridge, the mineralization was deflected around each end of the Precambrian ridge (Fig. 2). It appears that east-southeast-flowing ore fluids were initially ponded against the ridge and then they flowed southeastward around each end of the ridge. Casteel mine, Viburnum Trend At the Casteel mine in the Viburnum Trend, part of the orebody extends westward from the main north-south trend of the Viburnum Trend. In order to closely compare the position of the orebody at Casteel with the Precambrian and structural relief, figures 2 and 3 from Dunn and Grundmann 19 have been changed to the same scale and superimposed (Fig. 3). The extension of the orebody to the west, as pointed out by Dunn and Grundmann, follows the crest of an underlying Precambrian ridge. Where the westward extension reached a high Precambrian knob, the ore fluids flow both to the north and to the west partially encircling the knob. These relationships appear to indicate that some of the ore fluids at the Casteel mine escaped from the main north-south trend and traveled westward along the ridge crest. Where the westward-traveling fluids were impeded by the high knob and forced to flow northward along the east side of the knob and westward along the south side of that knob. Indian Creek Subdistrict The Indian Creek subdistrict consisted of two mines that were operated in an area located to the northeast of the Viburnum Trend and northwest of the Old Lead Belt. The ore deposits occurred in close association with a northeast-trending Precambrian ridge. The ores were predominantly in the uppermost part of the Lamotte Formation, but they extended upward into the lowest Bonneterre Formation. Figure 4 is a modification of a block diagram from Kyle and Gutierrez, 20 but in which the orebodies have been projected back down upon the Precambrian topography and rotated to place north at the top. The main long orebody occurs along the west-northwest side of a Precambrian knob and the smaller orebody occurs at the northnortheast end of that ridge. These relationships appear to indicate that the ore fluids at Indian Creek have come from the west-northwest and ponded against the northwest side of the Precambrian ridge. With respect to ore mineral zoning, the long orebody is copperrich at each end of that orebody. This probably indicates that the ore fluids entered this orebody at each end and then spread through the orebody. The position of the copper-rich ores within the smaller orebody provide further support for the ore fluid movements from the west-northwest. Old Leadbelt Subdistrict Metal zoning was studied in the Old Lead Belt Subdistrict by Davis. 21 The main area of copper-rich ores occurred along the northeast side of the northwest-trending subdistrict, but a smaller area of copper-rich ores were present at the northwest end of that subdistrict (Fig. 5). The distributions of copper-rich ores in this subdistrict is interpreted here to indicate that ore fluids came from the northeast along the northeast side of the subdistrict, but that ore fluids also came from the northwest along the northwest end of the subdistrict. The fact that the ores were said to be concentrated on the northwest side of some of the sedimentary structures at the northwest end of the subdistrict, 22 lends support to this interpretation of the metal zoning pattern. Hayden Creek mine, Old Leadbelt Subdistrict Further support for ore fluid movement from the northwest in the northwest portion of the Old Leadbelt Subdistrict comes from the fact that the Lamotte conglomerate-hosted orebodies at the Hayden Creek mine were positioned along the northwest and west-northwest sides of two Precambrian granite knobs. 23 Short extensions of the ore to the south and southeast from the two knobs occurred where the fluids flowed around those two knobs (Fig. 6). Fletcher mine, South Orebody, Viburnum Trend The pattern of metal zoning in the southern orebody at the Fletcher mine has been mapped by Childers et al. 24 and is shown in Figure 7. Where copper-rich ores are present they occur along the western side of the orebody. Relatively zinc-rich ores overlap the copper ores on the west and are present in the center of the orebody. This areal distribution suggests that the fluid came from the west depositing early copper-rich ores, and subsequently depositing somewhat later zinc-rich ores. Fletcher mine, North Orebody, Viburnum Trend The pattern of metal zoning in the northern orebody at the Fletcher mine also has been mapped by Childers et al. 24 and is shown in Figure 8. The copper-rich ores are predominantly along the western edge of the orebody, but a smaller area of copper-rich ores also occurs locally on the east. Again, relatively zinc-rich ores overlap the copper ores on the west and are present in the center of the orebody. Ironrich ores occur along the eastern side throughout the length of the mapped orebody. It is interpreted that ore fluids moving from the west deposited copper-rich ores on the west, later zinc-rich ores in the middle, and late iron-rich ores on the east. 2 Copyright 2006 by SME

3 West Fork mine, Viburnum Trend The pattern of metal zoning at the West Fork mine is similar to that at the Fletcher mine and may represent the dominant pattern for most ore deposits in the Viburnum Trend. Figure 9 is from Childers et al. 24 and it is a simplification of a map from Mavrogenes et al. 25 The copper-rich ores are restricted to the west edge of the orebody, and this suggests that the ore fluids at West Fork (and Fletcher) came from the west. Support for this interpretation comes from the fact that the late iron-rich pyrite-marcasite ores are concentrated along the east edge of that orebody. Magmont-West mine, Viburnum Trend The Magmont-West mine is an unusual orebody that lies about two miles west of the main Viburnum Trend, occurs slightly higher stratigraphically than most orebodies in the trend, contains relatively zinc-rich ores, and is interpreted to be closely controlled by a northwest-trending fault or fracture zone. 26,27 The form of the orebody also is partly modified by control from two minor east-northeasttrending faults (Fig. 10). Copper-rich ores occur at the east-northeast edge of the orebody and indicate that at Magmont-West the ore fluids came from the east-northeast (from the main Viburnum Trend to the east). In contrast to the map by Fennel, however, Voss 28 noted that there were rich copper ores along the west edge of Magmont-West orebody during the final days of mining, a feature that would suggest a component of ore fluid movement also from the west. A small area of copper-nickel sulfide ores formed even earlier than the copper-rich ores, and their location was closely associated with the intersections of the main northwest-trending fault with one of the minor northeast-trending faults. SUMMARY AND CONCLUSIONS One of the most interesting and controversial aspects of the ore deposits of southeast Missouri is that of the directions of flow of the ore fluids. One would presume that for the 45 mile-long north-south Viburnum Trend the answer would be simple. Either the fluids entered the trend from the south and flowed north, or the fluids entered the trend from north and flowed south. Previous workers have usually ascribed to one or the other of these thoughts. The present study has utilized the ponding of ore fluids behind Precambrian ridges and knobs and the patterns of ore mineral zoning to interpret the patterns of ore fluid flow in the district. The interpretations of ore fluid flow for the above ten selected mines and exploration areas are shown by seven arrows on a map (Figure 11) of the Southeast Missouri Lead District modified after Guilbert and Park 29 after Kisvarsanyi. 30 Ore fluids that deposited the main orebodies in the Viburnum Trend came predominantly from the northwest. Toward the southern portion of the Viburnum Trend the fluids may have come from a more easterly direction. Ore fluids that deposited the orebodies in the Indian Creek subdistrict also came from the northwest. The ore fluids that mineralized the Old Leadbelt Subdistrict came from the northeast as well as from the northwest. Locally, the ore fluids flowed in other directions. In the Viburnum Trend, for example, the ore fluids flowed westward at the Casteel and Magmont-West mines. At those mines, it is interpreted that the ore fluids had escaped from the main Viburnum Trend and locally flowed westward. Arrows are not shown on Figure 11 for those local variations of ore fluid flow. ACKNOWLEDGEMENTS The writer wishes to acknowledge previous discussions of Southeast Missouri Lead District geology with many company geologists, and especially with Joe Wagner with respect to possible directions of ore fluid movement in the Viburnum Trend. REFERENCES 1. Hagni, Richard D. (2000), The Mineralogy of Minor and Trace Elements in the Co-Ni-Cu-Pb-Zn Ores of the Viburnum Trend, Southeast Missouri: Ag, Cd, Ge, Ga, Co, Ni, As, Sb, Bi Minerals, in Minor Elements 2000: Processing and Environmental Aspects of As, Sb, Se, Te, and Bi, C. Young, ed., Littleton, CO, Society for Mining, Metallurgy, and Exploration, p Leach, David L. and, E. Lanier Rowan (1986), Genetic Link between Ouachita Foldbelt Tectonism and Mississippi Valley-type Deposits of the Ozarks, Geology, v. 14, p Bethke, C. M., W. J. Harrison, C. Upson,, S. P. Altaner (1988) Supercomputer Analysis of Sedimentary Basins, Science, v. 239, p Garven, Grant and J. P. Raffensperger (1997) Hydrogeology and Geochemistry of Ore Genesis in Sedimentary Basins Chapter 4 in Geochemistry of Hydrothermal Ore Deposits, Hughes L. Barnes, ed., 3 rd ed, New York, NY, John Wiley & Sons, p Shelton, Kevin L., I. B. Burstein,, Jay M. Gregg, and Richard D. Hagni, (1993), The Absence of a Regional Thermal Gradient, Does the Viburnum Trend Fit into a Common Regional Hydrologic Flow Model with other Ozark Region MVT Deposits? in Geology and Geochemistry of Mississippi Valley-type Ore Deposits, Kevin L. Shelton and Richard D. Hagni, eds University of Missouri-Rolla, Rolla, MO, p Stoiber, Richard E. (1946) Movement of Mineralizing Solutions in the Picher Field, Oklahoma-Kansas, Econ. Geol., v. 41, p Fass, Fred W. R. (1980), Mineral Asymmetry and Direction of Flow of the Ore-forming Fluids in the Viburnum Trend, Southeast Missouri, Unpub. M.S. Thesis, Univ. Missouri-Rolla, Rolla, Missouri, 94 p. 8. Hagni, Richard D. (1983), Ore Microscopy, Paragenetic Sequence, Trace Element Content, and Fluid Inclusion Studies of the Copper- Lead-Zinc Deposits of the Southeast Missouri Lead District, in International Conference on Mississippi Valley Type Lead-Zinc Deposits, Proceedings Volume, Geza Kisvarsanyi, S. Kerry Grant, Waldemar P. Pratt, and John W. Koenig, eds., University of MO- Rolla, Rolla, MO, p Jessey, David R. (1981), Mineralogical and Compositional Variations of the Nickel-Cobalt Mineralization in the S.E. Missouri Mining District, in Process Mineralogy, Donald M. Hausen and Won C. Park, eds., AIME, New York, p Hagni, Richard D. (1983), Minor Elements in Mississippi Valleytype Ore Deposits," Chapter 7 in, Cameron Volume on Unconventional Mineral Deposits, Wayne C. Shanks, III, ed. SME- AIME, New York, p Horrall, Keneth B., Mark R. Farr, and Richard D. Hagni (1997), Evidence for Focusing of Mississippi Valley-type fluids along the Bloomfield Lineament Zone, southeast Missouri, in. Carbonate- Hosted Lead-Zinc Deposits, Donald F. Sangster, ed,75 th Anniversary Volume, Soc. Econ. Geol. Spec. Publ. No. 4, p Gregg, Jay M. and Kevin L. Shelton (1989), Minor- and Traceelement Distributions in the Bonneterre Dolomite (Cambrian), Southeast Missouri: Evidence for Possible Multiple-Basin Fluid Sources and Pathways during Lead-Zinc Mineralization, Geological Society of America Bulletin, v. 101, p Wagner, R. Joe (1973), Stratigraphic and Structural Controls and Genesis of Barite Deposits in Washington County, Missouri, Unpub. Ph.D. Dissertation, University of Michigan, Ann Arbor, Michigan, 265 p. 14. Wagner, R. Joe (1995), Stratigraphic and Structural Controls and Genesis of Barite Deposits in Washington County, Missouri, (abstract and 2 figures) in Carbonate-Hosted Lead-Zinc-Fluorite- Barite Deposits of North America, Kula C. Misra,, ed., Society of Economic Geologists, International Field Conference Guidebook, p Morris, Richard L. (1994), Sulfide Minerals and Galena Morphological Distributions in Selected Viburnum Trend Ore Deposits, Southeast Missouri, Unpub. M.S. Thesis, University of Missouri-Rolla, Rolla, Missouri, 133 p. 16. Sun, Yan, Richard D. Hagni, Wayne T. Walker, and R. Joe Wagner (1998), Classification and Areal Distributions of Galena Morphologies in a Mississippi Valley-type Deposit, Sweetwater mine, Viburnum Trend, Southeast Missouri, U.S.A., in Proceedings of the Ninth IAGOD Symposium, International Association on the Genesis of Ore Deposits, Beijing, China, Richard D. Hagni, ed., E. 3 Copyright 2006 by SME

4 Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany, p Grundmann, William H., Jr. (1977), Geology of the Viburnum No. 27 mine, Viburnum Trend, Southeast Missouri, Econ. Geol., v. 72, p Wagner, R. Joe (2002), pers. comm Dunn, Robert G., Jr. and William H. Grundmann, Jr., (1989), Geology of the Casteel Mine: Copper-rich Ore in a MVT Setting, in Mississippi Valley-type Mineralization of the Viburnum Trend, Missouri, Richard D. Hagni and Raymond M. Coveney, Jr., eds., Society of Economic Geologists Guidebook Series, v. 5, p Kyle, J. Richard and G. N. Gutierrez (1988), Origin of the Indian Creek Sandstone-hosted Lead Deposits, Southeast Missouri, USA, Proceedings of the 7 th Quadrennial IAGOD Symposium, Lulea, Sweden, p Davis, James H. (1960), Mineralization in the Southeast Missouri Lead district, Unpub. Ph.D. Dissertation, Univ. Wisconsin, 68 p. 22. Perry, Bobbie (1961), pers. comm Ohle, Ernest L. (1952), Geology of the Hayden Creek Lead Mine, Southeast Missouri, AIME Trans., v. 193, p Childers, G. Andrew, Norman L. Paarlberg, and Lanny L. Evans (1995), Geology of the Fletcher Mine, Viburnum Trend, Southeast Missouri, in Carbonate-Hosted Lead-Zinc-Fluorite-Barite Deposits of North America, Kula C. Misra,, ed., Society of Economic Geologists, International Field Conference Guidebook, p Mavrogenes, John A., Richard D. Hagni, and P. Richard Dingess (1992), Metal Sulfide Mineral Zoning at ASARCO's West Fork Mine, Viburnum Trend, Southeast Missouri, Econ. Geol, v. 87, p Bradley, Milton F. and Thomas E. Krolak (1989), Magmont-West Lead-Zinc-Copper Mine (Cominco American Incorporated-Dresser Minerals) Viburnum Trend, Southeast Missouri, in Mississippi Valley-type Mineralization of the Viburnum Trend, Missouri, Richard D. Hagni and Raymond M. Coveney, Jr., eds., Society of Economic Geologists Guidebook Series, v. 5, p Fennel, Mark J., Richard D. Hagni, and Milton F. Bradley (1997), Mineralogy, Paragenetic Sequence, and Mineral Zoning at the Magmont-West Mine, Viburnum Trend, Southeast Missouri Lead District, in Carbonate-Hosted Lead-Zinc Deposits, Donald F. Sangster, ed., 75th Anniversary Volume, Society of Economic Geologists, p Voss, Robert L. (2003), pers. comm Guilbert, John M. and Charles C. Park (1999), The Geology of Ore Deposits, New York, NY, W. H. Freeman, 7 th printing, 985 p. 30. Kisvarsanyi, Geza (1977), The Role of the Precambrian Igneous Basement in the Formation of the Stratabound Lead-Zinc-Copper Deposits in Southeast Missouri, Econ. Geol., v. 72, p Copyright 2006 by SME

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