MISSISSIPPI VALLEY-TYPE LEAD-ZINC

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1 10. MISSISSIPPI VALLEY-TYPE LEAD-ZINC MISSISSIPPI VALLEY-TYPE LEAD-ZINC D.F. Sangster INTRODUCTION Mississippi Valley-type (MVT) lead-zinc deposits typically are composed of galena and sphalerite occurring as openspace fillings in carbonate breccias; replacement of host rocks is relatively minor except in high grade zones. The deposits owe their commonly accepted name to the fact that several classical districts occur within the drainage basin of the Mississippi River, central U.S.A. Important Canadian examples include Pine Point, Polaris, Nanisivik, Newfoundland Zinc, and Monarch-Kicking Horse deposits; of lesser importance are the deposits at Gays River, Nova Scotia and Robb Lake, British Columbia (Fig. 10-1). IMPORTANCE Prior to the opening of the Pine Point mine in 1965, Mississippi Valley-type deposits contributed only negligibly to Canadian lead-zinc production. Since that time, and until recently, about 30% of annual production has been derived from deposits of this type. With the closures of Pine Point and Newfoundland Zinc mines, however, the proportion of zinc and, to a lesser extent, lead derived from MVT deposits has decreased dramatically. Sangster, D.F. 1996: Mississippi Valley-type lead-zinc; & Geology of Canadian Mineral Deposit Types, (ed.) O.R. Eckstrand, W.D. Sinclair, and R.I. Thorpe; Geological Survey of Canada, Geology of Canada, no. 8, p (also Geological Society of America, The Geology of North America, v. P-I). SIZE AND GRADE OF DEPOSITS Data for individual deposits are difficult to obtain, mainly because of company repbrting policies or because the'deposi& themselves tend to be interconnected. Most deuosits, however, are small and fall between l and 10 Mt (~able.10-l). Grades generally range between 5 and 10% combined leadzinc with a majority of deposits being decidedly zinc-rich relative to lead. The tendency for MVT deposits to occur in clusters, up to as many as 400 in the Upper Mississippi Valley district, for example, renders them amenable to exploitation through establishment of common infrastructures. Some of these districts can be as large, in terms of contained lead and zinc, as certain of the world's giant stratiform, sediment-hosted (Sedex) deposits. GEOLOGICAL FEATURES The geological characteristics of these deposits have been summarized many times, most recently by Anderson and Macqueen (1988). A review by Sverjensky (1986) concisely lists the more important attributes of MVT deposits and Leach and Sangster (1993) present a comprehensive review of MVT deposits, their characteristics, and genetic models. Geological setting The deposits are hosted in carbonate rocks, usually platformal in origin, peripheral to cratonic sedimentary basins and characterized by tectonically stable depositional conditions (Anderson and Macqueen, 1988; Leach and Sangster, 1993). Only afew have been significantly affected by postore deformational events. In Canada, for example, the Polaris deposit has been tilted roughly 20' eastward by postore folding. Most deposits/districts are found below unconformities or nonconfo~mities, presumably produced by minor uplift or warping of the host strata.

2 TYPE 10 Age of host rocks and mineralization Host rocks to Canadian deposits range from Upper Proterozoic (Nanisivik, Gayna River) to Lower Carboniferous (Gays River) but most are in lower to mid-paleozoic strata. Pine Point, the largest Canadian Mississippi Valley-type district, is found in rocks of Middle Devonian age. Age of mineralization in MVT deposits in general, and in Canadian ones in particular, is known for only a few districts. The ore-forming process itself does not consistently yield material, either within the deposit or by alteration of adjacent host rocks, amenable to dating by traditional radiometric methods (see discussion & Sangster, 1986). Furthermore, the characteristic relatively stable tectonic regime of MVT districts generally precludes bracketing of mineralization age by field observations of postore events. Some success has recently been achieved through Rb-Sr dating of carefully selected sphalerite (e.g. Brannon et al., 1992) or through Ar-Ar methods on alteration minerals (e.g. Kontak et al., 1994). The most widespread technique, however, has been paleomagnetic dating of ore and host rocks, resulting in successful dating of several North American MVT deposits and districts (Pan et al., 1990, 1993; Symons and Sangster, 1991, 1992; Sangster and Symons, 1991; Symons et al., 1993). Results from all these recent methods have yielded mineralization dates which coincide with periods of orogenic uplift in the regions adjacent to the respective MVT deposits/districts. This correspondence in ages has been interpreted as support for the "gravity-driven fluid flow7' model for MVT genesis (see discussion under "Genetic model" below). Phanerozoic cover rocks L,,/;I #esozoic orogen ~a~eozoic orogen n Proterozoic cover rocks Middie Proterozoic wogen Early Proterozoic orogen Archean craton GSC Figure Locations of significant Canadian MVT deposits and districts.

3 MISSISSIPPI VALLEY-TYPE LEAD-ZINC Table Grade-tonnage data for selected MVT deposits/districts. DEPOSlTlDlSTRlCT Canada Mt I Newfoundland Zinc deposit I Production I Lane.1990 I Polaris deposit Nanisivik deposit Gays River deposit Pine Point district 22 > %Zn %Pb I Robb Lake deposit Reserves, 1975 I Macqueen and Thompson, 1978 ( I U.S.A. I Tri-State district East Tenn. district Old Lead Belt district Viburnum district Production I Haqni.1989 I Morocco-Algeria Bou Beker-El Abed district - = not reported COMMENTS Reserves + production, 1994 Production Reserves 1992 Reserves + production, 1983 Production Production Production Reserves + production, 1993 REFERENCE Randell, 1994 McNeil et al., 1993 Kontak, 1993 Rhodes et al., 1984 Brockie et al., 1968 Briskey et a1.,1986 Hagni,l989 Bouabdellah,l993 I Relations of ore to host rock Deposits are discordant on a deposit scale but stratabound on a district scale. Ore-hosting structures are most commonly zones of highly brecciated dolomite; in some instances (e.g. Pine Point, Newfoundland Zinc) these zones are arranged in linear patterns suggesting a structural control, although faults of large displacement are never present. The breccia zones may range from more-or-less concordant, occurring in one or two beds, to highly discordant cylindrical structures which penetrate tens of metres of sedimentary succession (Fig. 10-2, 10-3). Although the ore-hosting breccia bodies are commonly interpreted to be collapse breccias brought about by dissolution of underlying beds, there is little consensus on whether the dissolution and brecciation is due to meteoric waters (meteoric karst) or the ore-bearing fluids themselves (hydrothermal karst). A large majority of MVT deposits are overlain by a disconfonnity or unconformity and this has been cited in support of the meteoric hypothesis (e.g. Kyle, 1981). However, as pointed out by Sangster (1988, p. 114) "little or no direct evidence of a preore meteoric component... has yet been recognized" in MVT deposits. The hydrothermal karst origin for the collapse breccias has been most strongly supported for the Polish Silesian district (e.g. Sass-Gustkiewicz et al., 19821, the Upper Mississippi Valley district (Hey1 et al., 19591, and the Pine Point district (Qing, 1991). Distribution of ore minerals Characteristically, sulphide minerals in MVT deposits are found as open-space fillings between angular dolomite fragments in the ore-hosting breccias. In some instances, sulphides fill primary porosity cavities such as fossil molds or voids between the carbonate grains. Replacement of carbonate host rocks is generally minor except in those deposits, or portions of deposits, containing high-grade mineralization. Ore composition and zoning A majority of MVT deposits are of simple composition and consist of lead, zinc, and iron sulphides. Copper is not normally a constituent of MVT ores and is important only in the Southeast Missouri district, U.S.A. Cadmium, germanium, barite, and fluorite are, or have been, recovered from some districts. In the Southeast Missouri district and, to a lesser degree, the Upper Mississippi Valley district, Cu, Ni, and Co are diagnostic accessory elements but are atypical of the deposit type as a whole. Silver contents are generally very low; in most deposits silver is not reported in reserve statements. In those few deposits where it is reported, silver grades generally average in the g/t range. Nanisivik contains the highest silver grade in Canadian MVT ores with an average around 60 g/t. With the exception of the Southeast Missouri (U.S.A.) and Touissit-Beddiane (Morocco) districts, all major MVT districts are zinc-rich relative to lead and possess Zn/(Zn+Pb) ratios greater than 0.5. In the Southeast Missouri district, metal ratios are less than 0.1. Some ores, such as those of East Tennessee and Newfoundland Zinc, are essentially lead-free and have Zn/(Zn+Pb) ratios approaching 1.0. Consistent, well developed metal or mineralogical zon- ing is not a characteristic feature of MVT deposits. The simplicity of the ores all but precludes systemat& zoningin most districts. Again. however, the unusually mineralogically complex southeast ~issouri district is an exception andexhibits its own unique zoning patterns of Pb, Zn, Cu, Ni, and Co.

4 TYPE 10 Of the other world-class MVT districts, metal zoning has been described only for the Upper Mississippi Valley and Pine Point districts. In the former, Heyl et al. (1959, p. 143) have defined the district boundaries in terms of the distribution of lead-bearing deposits. Within the mainly east-trending lead district, zinc and copper occur mainly in a north-south belt through the east-central portion. An elongate north-south barite zone coincides with the western edge of the copper zone. A nickel zone, within which all lead-zinc orebodies contain millerite, is centred within the northern quarter of the barite zone. Compositional zoning in individual deposits at Pine Point has been described by Kyle (1981). Prismatic, discordant orebodies in this district feature an outward increase in the Fe/(Fe+Zn+Pb) ratio and a decrease in the Pb/(Pb+Zn) ratio; tabular, concordant orebodies in the same district are not zoned. Alteration Dissolution, recrystallization, and brecciation of the host carbonate rocks within, and peripheral to, mineralization is common to virtually all MVT deposits. These effects, which occur in conjunction with silicification and dolomitization, constitute the major form of wall rock alteration in MVT districts. Silicification is most characteristic of the Tri-State district in south-central U.S.A. (Brockie et al., 1968). The typical pattern there is a central dolomitic core surrounded progressively outward by the main ore zone, then by the silicified zone (consisting of microcrystalline quartz referred to as 'Sasperoid"), and finally by unaltered limestone. Dolomitization, of pre-, syn-, and postore age, is a widespread and characteristic feature of MVT districts. In spite of this, however, its significance and genetic history relative to burial diagenesis and the mineralizing event(s) is not well understood. In some districts it displays a complex relationship to host rocks and ore paragenesis. At Pine Point, for example, Krebs and Macqueen (1984) reported eight major paragenetic stages within which are at least seven periods of dolomite or calcite deposition. Alteration of rocks other than carbonates has only been reported in two districts. In the Upper Mississippi Valley district, Heyl et al. (1964) showed that minor changes occur in illite crystal structure outward from the ore zones. In basement granitic fragments occurring within the Southeast Missouri district, Stormo and Sverjensky (1983) observed alteration of K-feldspar and albite to kaolinite, quartz, and minor sericite. Mineralogy Simple mineralogy has long been identified as one of the main characteristics of MVT deposits but, as Ohle (1959, p. 775) pointed out, simplicity is apparent only on a district scale. When several MVT districts are considered together, an impressive list of more than three dozen minerals can be compiled. When, however, the mineralogically unique and complex Southeast Missouri district is omitted, together with those minerals reported in only one or two districts, the most common minerals are: pyrite, marcasite, sphalerite, and galena, although relative mineral abundances vary markedly between deposits and/or districts. Barite andlor fluorite are accessory minerals in Trace 01 premlneral~zed and / prellu~d allerar~ori slr~ke.sl~p lault I - 1 BRANCHING SHOOT - TYPE ORE BODIES +BREAKTHROUGH, TYPE ORE BODY Figure Schematic representation of a columnar ore-bearing breccia body in the East Tennessee MVT district (modified from Ohle, 1985).

5 MISSISSIPPI VALLEY-TYPE LEAD-ZINC some lead-zinc districts (e.g. Central Tennessee) but, in a majority of districts, these minerals are entirely lacking. Lead and zinc are the most common elements that determine economic viability. In some districts, silver is an important byproduct but, in most deposits, it is a negligible factor. Cadmium, germanium, barite, and fluorite are, or have been, recovered from some deposits. Organic material Organic material, usually in the form of mature, tarry hydrocarbon ("pyrobitumen") is common in some, but not all, MVT districts and occurs as a paragenetically late phase (e.g., Macqueen and Powell, 1983). Methane andlor liquid petroleum have been identified in fluid inclusions in sphalerite in a few instances. Ore textures The most diagnostic textures of MVT deposits are those produced by open-space filling. Replacement is relatively minor except in high grade zones. The open spaces may be primary (e.g. fossil molds) but are usually secondary. Secondary porosity is dominantly in the form of collapse (solution) breccias; sulphides and carbonates constitute the cement between breccia fragments. Ore textures are, to a considerable degree, controlled by ore-bearing breccias. The latter vary considerably, from one MVT district to the other, in the nature and abundance of their internal features. Three main breccia types or textures have been recognized: crackle breccia, mineralized breccia (sometimes referred to as "ore-matrix breccia"), and barren breccia ("rock-matrix breccia") (Sangster, 1988). As suggested by the name, sulphides are most common and abundant in the mineralized breccia which is characterized by dolostone fragments cemented by white or pink crystalline spany dolomite and sulphides (Fig. 10-4). Dolostone fragments are typically rotated and can usually be demonstrated to have dropped from their original stratigraphic position. Both ore and gangue minerals are commonly, but not invariably, coarse grained. The Tri-State district, U.S.A., for example, is world-renowned for its exceptionally large, euhedral sphalerite and galena crystals yet the ore-related chert and jasperoid consists of microcrystalline quartz. Some districts, in contrast, are characterized by their extremely fine grained sulphides as exemplified by the banded, colloform sphalerite containing skeletal galena crystals as at Pine Point and Polaris in Canada, the Silesia district in Poland, and the Cadjebut deposit in Australia. Three sulphide textures in particular are characteristic of MVT deposits although it is uncommon for all three to occur in a single deposit: trash zones, internal sediments, and "snow-on-roof'. During dissolution of the host carbonate, resulting in formation of the ore-bearing collapse breccias, much insoluble material accumulated at the bottom of the breccia bodies. These trash zone accumulations can range up to a few metres in thickness, consist of poorly sorted grains of a variety of minerals, most of which are dolomite clay, chert, quartz, sulphides, and black, carbonaceous material (Hill et al., 1971). Internal sediments, well stratified material which partly or entirely fills the space between breccia fragments (Fig. 10-5), consist mainly of Figure Prismatic ore breccia, 0-28 deposit, Pine Point district. Note beds on left bend downward as they approach the breccia body (outlined by short dashes). GSC M Figure Ore-matrix breccia, Jefferson City mine, East Tennessee district. White material is sparry dolomite cement. Length of pen visible is 6 cm. GSC D 257

6 TYPE 10 dolomite grains but commonly contain a large component of detrital sand-size sulphide grains and composite sulphidecarbonate fragments (Kendall, 1960; Sass-Gustkiewicz et al., 1982; Rhodes et al., 1984; Randell and Anderson, 1990; Bouabdellah, 1993). Graded bedding is not uncommon in internal sediments. First described by Oder and Hook (l%o), "snow-on-roof' texture is, in the author's opinion, the most diagnostic texture of MVT deposits because it has not been reported in any other type of mineral deposit. Typically, sphalerite occurs as coarse crystals preferentially coating the of dolomite breccia fragments in ore-matrix breccias (Fig. 10-6). Undersides of the same fragments are coated either not at all or to a much lesser degree. A variety of snow-on-roof texture is sphalerite lining the bottoms of cavities (Fig. 10-7). In either case, the feature can be regarded as a geopetal indicator. Figure Internal sediments in K-57 orebody, Pine Point district. Sediment consists of detrital dolomite sand grains. Knife is 8 cm. GSC F DEFINITIVE CHARACTERISTICS 1. Deposits occur principally in limestone or dolomite in platform carbonate sequences; 2. Ore is strongly controlled by individual strata (i.e. stratabound); 3. The most common minerals are pyrite, sphalerite, galena, dolomite, calcite, and quartz; 4. Deposits are not associated with igneous rocks; 5. They may occur in areas of mild deformation expressed as brittle fracture, uplift of broad domes, and subsidence of related basins; 6. There is always evidence of dissolution of carbonate host rock expressed by slumping, collapse, brecciation, or some combination of these; 7. Fluid inclusions in the constituent minerals always contain dense, saline, aqueous fluids. Total dissolved salts range from 10 to 30 wt.% and are predominantly sodium and calcium chlorides. Figure Snow-on-roof texture in ore-matrix breccia, K zone, Newfoundland Zinc mine. Sphalerite is the grey material within the white sparry dolomite cement and immediately on top of the dark fragment under the pen. Note the sphalerite is absent underneath the same fragment but is present again on top of the next fragment, lower right corner. Pen is 6 cm. GSC H Figure Coarse grained sphalerite (dark) lying on bottom of cavity; remainder of void filled with carbonate. Elrnwood mine, Central Tennessee district. Pen is 16 cm. GSC E

7 MISSISSIPPI VALLEY-TYPE LEAD-ZINC GENETIC MODEL The deposits are obviously epigenetic, having been emplaced after host rock lithification. The ore-hosting breccias are considered to have resulted from dissolution of more soluble sedimentary layers with subsequent collapse of overlying beds (see discussion Sangster, 1988). The major mineralizing processes appear to have been openspace filling between breccia fragments and replacement of fragments or wall rock, although the relative importance of these two processes varies widely among deposits. Based on fluid inclusion data, MVT deposits clearly formed from hot, saline, aqueous solutions which, in many respects, are similar to modern oil-field brines (e.g. Sverjensky, 1984). Thus, some form of basinal brine migration out of sedimentary basins, through aquifers, to the basin periphery is the most widely accepted general mode of formation of MVT ores (Sverjensky, 1986). To move the ore solutions out of the basin clastics and into the platform carbonates, two main models have been proposed: 1. Basin compaction-driven fluid flow In this proposal, two subtypes may be considered: (i) continuous outward flow which assumes that simple compaction of sediments in a subsiding basin will drive pore fluids laterally along aquifers; and (ii) episodic outward flow. The latter subtype was proposed to overcome some of the objections raised in the concept of continuous flow, notably the problem of maintaining high initial fluid temperatures during transport of up to hundreds of kilometres from basin source to platform depositional site. To address this dificulty, a process involving overpressuring of subsurface aquifers by rapid sedimentation, followed by rapid and episodic release of basinal fluids, has been proposed (Sharp, 1978; Cathles and Smith, 1983). 2. Gravity-driven fluid flow The gravity-driven fluid flow model advocates flushing of subsurface brines out of a sedimentary basin by groundwater flow from recharge areas, in elevated regions of a foreland basin, to discharge areas in regions of lower elevation (Garven, 1985; Bethke, 1986; Bethke and Marshak, 1990). The pros and cons of each of these mechanisms have been debated in the scientific literature (e.g. Sverjensky, 1986) and, as pointed out by Bethke and Marshak (1990), considerable evidence is being accumulated in support of the gravity-driven fluid concept, particularly with respect to the MVT districts of mid-continent U.S.A. "Increasingly it is clear that the migrating brines originated in the forelands of North American tectonic belts, and that the migrations coincided in time with intervals during which the belts were deformed" (Bethke and Marshak, 1990, p. 287). Evidence in support of this concept includes: i) a steady decrease in MVT ore-stage fluid inclusion homogenization temperatures away from the uplifted orogenic belt and toward the continental interior; ii) the development of alteration potassium feldspar and clay minerals in the host sedimentary rocks, interpreted as due to K-metasomatism associated with brine movement; iii) epigenetic dolomite cement with chemical and isotopic compositions indicating flow directions away from the uplifted orogen; iv) correlation of cathodoluminescence banding in dolomite cements over very large areas, indicating widespread brine migration; v) paleomagnetic ages in MVT ores which coincide with periods of orogenic uplift; and vi) radiometric ages of authigenic K-feldspar in platform carbonate rocks, also coinciding with orogenic uplift. Results of these studies are still being evaluated relative to other evidence from MVT deposits but seem to indicate that MVT deposits may have formed in response to brine migration through carbonate successions in the forelands of tectonic belts. In addition to the problem of transport of fluid fi-om the basin to carbonate platforms, three geochemical models have been proposed to account for chemical transport and deposition of the ore constituents: i) mixing model -base metals are transported by fluids of low sulphur content. Precipitation is effected by a) mixing with fluids containing hydrogen sulphide, or b) replacement of diagenetic iron sulphide, or C) thermal degradation of organic compounds and resultant release of sulphur; ii) sulphate reduction model - base metals are transported together with sulphate in the same solution. Precipitation is the result of reduction of sulphate by reaction with organic matter or methane; iii) reduced sulphur model - base metals are transported together with reduced sulphur in the same solution. precipitation is brought about by any or all of: a) change of ph, or b) dilution, or c) cooling. In attempting to explain the genesis of MVT deposits, it has been traditional to emphasize the common features of several MVT districts. In recent years, however, several writers have begun to question this approach and to suggest, instead, that a re-examination of the differences might be a more fruitful line of approach. Thus, for example, Ohle (1980, p. 163) reflected on the fact that the "individualities raise the question as to whether each ore had a different source, a different plumbing system, and a different timing from all the others". Similarly, Sangster (1983, p. 7) concluded that the differences between MVT districts outweighed the similarities, both numerically and in significance, and that, therefore, a common genetic model was perhaps precluded. In a review of MVT deposit models, Sverjensky (1986) concluded that significant differences exist between MVT districts and that, as a consequence, all districts may not have formed in exactly the same way. Evidence from Pine Point, for example, suggests a two-fluid mixing model whereas Southeast Missouri ores appear to have been precipitated from a single fluid containing base metals and reduced sulphur. RELATED DEPOSIT TYPES Fracture-controlled, F-dominant deposits (with subordinate Ba, Pb, and Zn) such as those of Illinois-Kentucky and the English Pennines, the central Missouri Ba(Pb) district, and the Tennessee Sweetwater F-Ba(Pb-Zn) district may represent MVT F-Ba deposits rather than MVT Pb-Zn deposits.

8 TYPE 10 Inasmuch as the weight of current evidence favours the formation of MVT Pb-Zn ores from sedimentary basin waters, these deposits have been genetically linked to sedimentary exhalative deposits (Sedex) Pb-Zn which are also considered to have formed from basinal fluids (Sangster, 1990,1993). EXPLORATION GUIDES Because of the significant differences between districts noted above, universal exploration guides for MVT deposits are virtually precluded. Only broad guidelines such as platformal carbonates adjacent to large sedimentary basins, the presence of unconformities in the carbonate platform, and the abundance of dolomite in and around MVT districts can be regarded as common to all districts. The presence of basement highs underneath the carbonate cover, if detectable by means, might be useful in some instances. Extension of ex~loration outward from known districts should focus on tge ore-containing strata of the known district. Beyond this rather self-evident truism, however, there is little to guide the explorationist. This is borne out by the "random walk" method used to site exploration holes used in the discovery of the Central Tennessee district situated in similar strata to, but 200 km distant from, the well-known East Tennessee district (Callahan, 1977). SELECTED BIBLIOGRAPHY References with asterisks (*) are considered to be the best source ofgeneral information on this deposit type. Anderson, G.M. and Macqueen, R.W. 1988: Ore deposit models - 6. Mississippi Valley-type lead-zinc deposits: - in Ore Deposit Models, (ed.) R.G. Roberts and P.A. Sheahan; Geoscience Canada, Reprint Series 3, p Bethke, C.M. 1986: Hydrologic constraints on the genesis of the Upper Mississippi Valley mineral district from Illinois Basin brines; Economic Geology, v. 81, p *Bethke, C.M. and Marshak, S. 1990: Brine migrations across North America - the plate tectonics of groundwater; Annual Review and Earth Planetary Science, v. 18, p Bouabdellah, M. 1993: MBtallogen&se d'un district de type Mississippi Valley, cas de Beddiane, District de Toussit-Bou Becker, Maroc; PhD. thesis, Ecole Polytechnique, Montreal, Canada, 338 p. Brannon, J.C., Podosek, FA, and McLimans, R.K. 1992: Alleghanian age of the Upper Mississippi Valley zinc-lead depposit determined by Rb-Sr dating of sphalerite; Nature, v. 356, p Briskey, J.A., Dingess, P.R., Smith, F., Gilbert, R.C., Armstrong, A.K., and Cole, G.P. 1986: Localization and source of Mississippi Valley-type zinc deposits in Tennessee, U.S.A., and comparisons with Lower Carboniferous rocks of Ireland; p , jrj Geology and Genesis of Mineral Deposits in Ireland, (ed.) C.J. Andrew, R.W.A. Crowe, S. Findlay, W.M. Pennel, and J.F. Pyne; Irish Association for Economic Geology, Cahill Printers Ltd., Dublin, 699 p. Brockie, D.C., Hare, E.H., Jr., and Dingess, P.R. 1968: The geology and ore deposits of the Tri-State District of Missouri, Kansas, and Oklahoma; Ore Deposits of the United States, (ed.) J.D. Ridge; American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., New York, v. 1, p Callahan, W.H. 1977: The history of the discovery of the zinc deposit at Elmwood, Tennessee: concept and consequence; Economic Geology, v. 72, p Cathles, L.M. and Smith, AT. 1983: Thermal constraints on the formation of Mississippi Valley-type lead-zinc deposits and their implications for episodic basin dewatering and deposit genesis; Economic Geology, v. 78, p *Gwen, G. 1985: The role of regional fluid flow in the genesis of the Pine Point deposit, Western Canada sedimentary basin, Economic Geology, v. 80, p Garven, G. and Freeze, R.A. 1984a: Theoretical analysis of the role of groundwater flow in the genesis of stratabound ore deposits: 1. Mathematical and numerical model; American Journal of Science, v. 284, p b: Theoretical analysis of the role of groundwater flow in the genesis of stratabound ore deposits: 2. Quantitative results; American Journal of Science, v. 284, p Hagni, R.D. 1989: The southeast Missouri lead district: a review; Mississippi Valley-type Mineralization of the Viburnum Trend, Missouri, (ed.) R.D. Hagni and R.M. Coveney, Jr.; Guidebook Series Volume 5, Society of Economic Geologists, p Heyl, A.V., Agnew, A.F., Lyons, EJ., and Behre, C.H., Jr. 1959: Geology of the Upper Mississippi Valley zinc-lead district; United States Geological Survey, Professional Paper 309,310 p. Heyl, A.V., Hosterman, J.W., and Brock, M.R. 1964: Clay mineral alteration in the Upper Mississippi Valley zinc-lead district, Twelfth National Conference on Clays and Clay Minerals, 1963, Proceedings, New York, MacMillan Co., p Hill, W.T., Morris, R.G., and Hagegeorge, C.G. 1971: Ore controls and related sedimentary features at the Flat Gap mine, Treadway, Tennessee; Economic Geology, v. 66, p Jackson, S.A. and Beales, F.W. 1967: An aspect of sedimentary basin evolution: the concentration of Mississippi Valley-type ores during late stages of diagenesis; Canadian Petroleum Geology Bulletin, v. 15, p Kendall, D.L. 1960: Ore deposits and sedimentary features, Jefferson City mine, Tennessee; Economic Geology, v. 55, p Kontak, D.J. 1993: A preliminary report on geological, geochemical, fluid inclusion, and isotopic studies of the Gays River Zn-Pb deposit, Nova Scotia; Nova Scotia Department of Natural Resources, Open File Report , 223 p. Kontak, D.J., Farrar, E., and McBride, S.L. 1994: 40ArP9Ar dating of fluid migration in a Mississippi Valley-type deposit: the Gays River Zn-Pb deposit, Nova Scotia, Canada; Economic Geology, v. 89, p Krebs, W. and Macqueen, R. 1984: Sequence of diagenetic and mineralization events, Pine Point lead-zinc property, Northwest Territories, Canada; Canadian Petroleum Society Bulletin, v. 32, p Kyle, J.R. 1981: Geology of the Pine Point lead-zinc district; Handbook of strata-bound and stratiform ore deposits, (ed.) K.H. Wolf; Elsevier Publishing Company, New York, v. 9, p Lane, T.E. 1990: Dolomitization, brecciation, and zinc mineralization and their paragenetic, stratigraphic, and structural relationships in the Upper St. George Group (Ordovician) at Daniel's Harbour, western Newfoundland; PhD. thesis, Memorial University of Newfoundland, St. John's, Newfoundland, 565 p. *Leach, D.L. and Sangster, D.F. 1993: Mississippi Valley-type lead-zinc deposits; Mineral Deposit Modeling (ed.) R.V. Kirkham, J.M. Duke, W.D. Sinclair, and R.I. Thorpe; Geological Association of Canada, Special Paper 40, p Macqueen, R.W. and Powell, T.G. 1983: Organic geochemistry of the Pine Point lead-zinc ore field and region, Northwest Territories, Canada; Economic Geology, v. 78, p McNeil, W.H., Rawling, K.R., and Sutherland, R.A. 1993: Nanisivik Mine - operations and innovations in an Arctic environment; World Zinc '93, Proceedings of the International Symposium on Zinc, (ed.) I.G. Mathews; Australasian Institute of Mining and Metallurgy, Publication Series No. 7/93, p , Oder, C.R.L. and Hook, J.W. 1950: Zinc deposits in the southeastern states; jrj Symposium on Mineral Resources of the South-eastern United States, (ed.) F.G. Snyder; Knoxville, Tennessee, University of Tennessee Press, p

9 MISSISSIPPI VALLEY-TYPE LEAD-ZINC Ohle, E.L. 1959: Some considerations in determining the origin of ores of the Mississippi Valley type; Economic Geology, v. 54, p : Some considerations in determining the origin of ores of the Mississippi Valley type, Part 11; Economic Geology, v. 75, p : Breccias in Mississippi Valley-type deposits; Economic Geology, v. 80, p Oliver, J. 1986: Fluids expelled tectonically from orogenic belts: their role in hydrocarbon migration and other geologic phenomena; Geology, v. 14, p Pan, H., Symons, D.T.A., and Sangster, D.F. 1990: Paleomagnetism of the Mississippi Valley-type ores and host rocks in the northern Arkansas and Tri-State districts; Canadian Journal of Earth Sciences, v. 27, p : Paleomagnetism of the Gays River zinc-lead deposit, Nova Scotia: Pennsylvanian ore genesis; Geophysical Research Letters, v. 20, D Qiw, H. 1991: Diagenesis of Middle Devonian Presqu'ile dolomite, Pine Point, N.W.T. and adjacent subsurface; PhD. thesis, McGill University, Montreal, Quebec, 287 p. Randell, R.N. 1994: Geology of the Polaris Zn-Pb Mississippi Valley-type deposit, Canadian Arctic Archipelago; PhD. thesis, University of Toronto, Toronto, Ontario. Randell, R.N. and Anderson, G.M. 1990: The geology of the Polaris carbonate-hosted Zn-Pb deposit, Canadian Arctic Archipelago; h Current Research, Part D; Geological Survey of Canada, Paper 90-ID, p Rhodes, DA, Lantos, EA, Lantos, JA, Webb, R.J., and Owens, D.C. 1984: Pine Point orebodies and their relationship to the stratigraphy, structure, dolomitization, and karstification of the Middle Devonian barrier complex; Economic Geology, v. 79, p Sangster, D.F. 1983: Mississippi Valley-type deposits: a geological m6lange; b Proceedings, International Conference on Mississippi Valley-type Lead-zinc Deposits, (ed.) K. Kisvarsanyi, S.K. Grant, W.P. Pratt, and J.W. Koenig; University of Missouri-Rolla, Missouri, p : Age of mineralization in Mississippi Valley-type (MVT) deposits: a critical requirement for genetic modelling; b Geology and Genesis of Mineral Deposits in Ireland, (ed.) C.J. Andrew, R.W.A. Crowe, S. Findlay, W.M. Pennel, and J.F. Pyne; Irish Association for Economic Geology, Cahill Printers Ltd. Dublin, p Sangster, D.F. (cont.) 1990: Mississippi Valley-type and sedex lead-zinc deposits: a comparative examination; Institution of Mining and Metallurgy, Transactions, (Sect. B: Applied earth science), v. 99, p. B21-B : Breccia-hosted lead-zinc deposits in carbonate rocks; hpaleokarst, (ed.) N.P. James and P.W. Choquette; Society of Economic Paleontologists and Mineralogists, p : Evidence for, and implications of, a genetic relationship between MVT and SEDEX zinc-lead deposits;h World Zinc '93, Proceedings of the International Symposium on Zinc, (ed.) I.G. Mathews; Australasian Institute of Mining and Metallurgy, Publication Series No. 7/93, p Sangster, D.F. and Symons, D.T.A. 1991: Methodology and genetic implications of paleomagnetic dating of Mississippi Valley-type lead-zinc deposits in the midcontinental region of the USA.; Source, Transport and Deposition of Metals, Proceedings of the 25th Anniversary Meeting of the Society for Geology Applied to Mineral Deposits, (ed.) M. Page1 and J.L. Leroy; p Sass-Gustkiewicz, M., Dzulynski, S., and Ridge, J.D. 1982: The emplacement of zinc-lead sulfide ores in the Upper Silesian district - a contribution to the understanding of Mississippi Valley-type deposits; Economic Geology, v. 77, p Sharp, J.M., Jr. 1978: Energy and momentum transport model of the Ouachita basin and its possible impact on formation of economic mineral deposits; Economic Geology, v. 73, p Stormo, S. and Sve jensky, DA 1983: Silicate hydrothermal alteration in a Mississippi Valley-type deposit, Viburnum, southeast Missouri lead district; Geological Society of America, Abstracts with Programs, v. 15, p Sve jensky, DA 1984: Oil field brines as ore-forming solutions; Economic Geology, v. 79, p '1986: Genesis of Mississippi Valley-type lead-zinc deposits; Annual Review, Earth and Planetary Science, v. 14, p Symons, D.T.A. and Sangster, D.F. 1991: Paleomagnetic age of the central Missouri barite deposits and its genetic implications; Economic Geology, v. 86, p : Late Devonian paleomagnetic age for the Polaris Mississippi Valley-type Zn-Pb deposit, Canadian Arctic Archipelago; Canadian Journal of Earth Sciences, v. 29, p Symons, D.T.A., Pan, H., Sangster, D.F., and Jowett, E.C. 1993: Paleomagnetism of the Pine Point Zn-Pb deposits; Canadian Journal of Earth Sciences, v. 30, p Author's address D.F. Sangster Geological Survey of Canada 601 Booth Street Ottawa, Ontario KIA OE8 Printed in Canada 261

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