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Diverse connections between ores and organic matter
Ore Geology Reviews 24 (2004) 1 – 5 www.elsevier.com/locate/oregeorev
Preface
Diverse connections between ores and organic matter The world’s premier deposits of barite, copper, gold, iron, lead, and zinc occur in sedimentary basins (Laznicka, 1999). Many are associated with organicrich shales and hydrocarbons (Fig. 1). For example, the Pb and Zn ores of the American Mississippi Valley including the Viburnum Trend, the world’s largest known concentration of lead, occur on the peripheries of basins containing hydrocarbon deposits and black shales (Dozy, 1970; Coveney, 2000). Spatial correlations, among other factors, have led to inferences about critical roles for organic matter and organisms in sourcing, transporting, and depositing ores. However, in many cases, clear proof of a genetic relationship between ores and organic matter remains elusive—in some cases even dubious, despite spatial coincidence. The Selwyn Basin of western Canada and the Zechstein of northern Europe contain both carbonate-hosted deposits and sedimentary exhalative (sedex) deposits, which share many common characteristics, including transport of ore constituents by basinal brines (Sangster, 1990). Yet, certain major shale basins, such as those of the Mississippi Valley, USA, contain no known sedex ores, despite the presence of major carbonate-hosted lead – zinc deposits, black shales, and hydrocarbons. Moreover, some black shale basins appear to contain neither type of deposit, although this may be attributable to insufficient exploration. Besides the productive deposits alluded to above, stratified rocks contain other deposits that may be important in the future including non-placer resources of Au and platinum group elements (PGE). For example, Kucha (1982) reported remarkably rich centimeter-scale Au and PGE laminae in the Kupferschiefer of Poland, which are not economic because of their thinness. Nevertheless, his results led to further studies and the discovery of significant Au minerali0169-1368/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.oregeorev.2003.08.002
zation in the accompanying Rote Fa¨ule facies in the same mining district (Piestrzyn´ski and Wodzicki, 2000), which may become an important source of precious metals. Similar possibilities exist for the unusual decimeter-scale beds of Ni, Mo, As, and Zn sulfides containing PGE and Au in China (Fan, 1983) and the Yukon (Hulbert et al., 1992) (Fig. 1). Their possible economic value is supported by reports of thicknesses up to 1 m for the deposits in Guizhou, China (Zeng, 1998; Mao et al., 2002). Moreover, Goodfellow (2002) has documented three new occurrences in the Yukon, separated by 400 km. These workers suggest that the deposits may have been deposited from normal sea water or in the wake of an asteroid impact, respectively, but others favor comparatively prosaic sedex origins (e.g., Hulbert et al., 1992; Lott et al., 1999).
1. Summaries of articles The eight articles contained in this special issue of Ore Geology Reviews are a sampling of 35 oral and poster presentations given in symposium 11-3, Mineral Deposits Associated with Black Shales, at the 31st International Geological Congress (IGC-31) held in August 2000 in Rio de Janeiro, Brazil. The contributions cover Au, Mn, Cu, Hg, Zn, Ni, Sn, Sb, and barite deposits hosted by sedimentary or metasedimentary rocks (Fig. 1). Two occurrences of organic matter are described: (1) the exceptionally large, and possibly unique, shungite deposits hosted by Proterozoic strata in Russia and (2) a showing of metalliferous bitumen located not far from a former lead – silver – nickel mine in Scotland. Victor A. Melezhik, M.M. Filippov, and A.E. Romashkin describe the unique deposits of Russian
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Fig. 1. Locations of deposits. Airo and Loukola-Ruskeeniemi (2003) propose a means for locating massive sulfide deposits by geophysical techniques that partly depend on their organic contents. Munteanu et al. (2003) review sediment-hosted Mn deposits associated with black shales in the Eastern Carpathian Mountains of Romania. The world’s preeminent giant deposits of barite are located in China and India, but it is unclear which of these deposits is largest. Three of these, the Qinling and Jiangnan deposits of China, and the Mangampeta deposit of India, as well as the Nevada Barite Belt deposits, are reviewed by Clark et al. (2003). Distler et al. (2003) thoroughly cover the giant Au – PGE lode deposit hosted by metamorphosed black shales at Sukhoi Log in Siberia. Fan et al. (2003a,b) discuss the influences of organic matter in the formation of both the tin deposits at Dachang and the world’s largest antimony deposits at Xikuangshan, China. The peculiar carbon-rich material, known as shungite, that may be a source of fullerenes occurs in the Karelian region of Russia (Melezhik et al., 2003). A minor but interesting occurrence of metal-rich bitumen from Scotland illustrates the mobility of Ti in basinal brines (Parnell, 2003). The illustration shows the locations major sedimentary basins containing metalliferous black shales with respect to the positions of the world’s largest ore deposits for various commodities. Locations of premier deposits and black shale basins are taken from Gustafson and Williams (1981), Goodfellow (1987), Sangster (1990), Laznicka (1999), and Coveney (2000). The locations of the world’s largest deposits of 14 metals, Sb, and barite are from Sangster (1990), Laznicka (1999), and Searls (2000).
Karelia that contain shungite, which can be used to extract aqueous pollutants and to make shungisite, a lightweight insulating material. Fullerenes were first reported from nature from these deposits by Buseck et al. (1992), but the likelihood of commercial extraction of this extremely valuable commodity is clouded by uncertainty over the quantity of natural fullerenes that are present. Nevertheless, even if commercial amounts of fullerenes are not present, Melezhik et al. (2003) suggest that the deposits may provide a useful raw material for synthesis of fullerenes. Marian Munteanu, Stefan Marincea, Haino Uwe Kasper, Karel Zak, Veronica Alexe, Angela Mihalache, Corina Cristea, Vasile Trandafir, George Sapte-
frati, Cristian Simionescu, and Danuzia Airinei propose that the East Carpathian manganese deposits of Romania were deposited in an environment located near the interface between anoxic bottom waters and overlying oxic seawater. They discount the importance of supergene processes in the development of Mn oxide ores that have been postulated by others. Delian Fan, Tao Zhang, and Jie Ye discuss the enormous Xikuangshan deposit, of Hunan, China, the world’s largest source of antimony (Laznicka, 1999). This deposit is hosted by Devonian Sb-rich black shale, rich in organic carbon that accumulated during anoxic sedimentation (Fan et al., 2003a). With her collaborators, Tao Zhang, Jie Ye, Jan Pasˇava, Bohdan
Preface
Krˇibek, P. Dobes, I. Varrin, and K. Zak, Delian Fan also covers the Dachang Sn-polymetallic deposits hosted by Devonian black shales of Guangxi, China, which are second in production only to the Malaysian placer Sn deposits (Laznicka, 1999). Fan et al. (2003b) favor a biogenic source for sulfur for some of the tin deposits but infer an igneous source for sulfur in other cases based on isotopic data. Pasˇava and Krˇ´ıbek (2001) and Pasˇava et al. (2003) have provided additional evidence for the active involvement of black shales and organic matter in the origin of tin-polymetallic deposits in the Dachang mining district. Devonian black shales were a likely source of S and in part for Sb, Co, Pb, V, and Fe during ore deposition at the Dafulou, Huile, and Kangma cassiterite-sulfide deposits in the eastern part of the district. Black shales also played an important role in controlling the deposition of remobilized and epigenetic replacement-type sulfide Sn mineralization related to granitic intrusions. At the Dafulou deposit, geochemical studies show that in situ organic matter locally interacted with hydrothermal solutions to decrease the fO2 and form massive pyrrhotite ores and pyrobitumen that are generally absent in other deposits located in the eastern part of the district. Pasˇava et al. (2003) suggested that black shales at the Dachang ore district may have controlled deposition of the ores associated with the Longxianggai granite by inducing low fO2 conditions at the exocontact, which may have resulted in the accumulation of Sn2 + in the residual melt and the formation of high-Ca black shale or carbonate-replacement tin-sulfide ores distal to the intrusion. The contribution by Vadim V Distler, Marina A. Yudovskaya, Gennady L. Mitrofanov, Vsevolod Y. Prokof’ev, and Eric N. Lishnevskii covers the Ptbearing gold deposit at Sukhoi Log in Siberia, which contains an estimated 1100 tons of Au. Although the Sukhoi Log deposit is comparatively rich in organic matter, no significant correlation exists between grades for Au, or for that matter Pt, and total organic matter. The lodes of Sukhoi Log may have been an important source of precious metals for major placer deposits that have been mined in the area for many years. Meri-Liisa Airo and Kirsti Loukola-Ruskeeniemi demonstrate the use of high-resolution geophysical techniques to find favorable environments for massive
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sulfide ores, such as those of Outokumpu, in the Proterozoic of eastern Finland. Such techniques, which partly depend upon the presence or absence of graphite formed from organic matter, may be critically important for effective exploration of areas where outcrops are rare because of glacial cover, deep weathering, or other causes. Sandra H.B. Clark, Forest G. Poole, and Zhongcheng Wang compare the geologic settings and genesis of barite deposits from including several from the world’s most productive barite mining regions including the Yangtze Platform of China from which more than half of current barite production is derived (Searls, 2000) and the huge Mangampeta barite deposit of Andhra Pradesh, India. Clark et al. (2003) round out their survey with the Nevada Barite Belt, which has become the chief supplier of domestic barite in the United States, surpassing Missouri and other formerly important sources. Geochemical results and comparisons with barite occurrences currently being formed off the coast of California lead the authors to conclude that major barite deposits can be formed by either sedex hydrothermal or biogenic processes. John Parnell’s study shows that titanium can be readily mobilized in pore fluids. The Craigs, Scotland, occurrence of bitumen is located within 500 m of a small mine that formerly produced nickel, lead, and silver, suggesting the possibility of genetic connections. Mixed hydrocarbon – brine fluid inclusions testify to the interrelationships among energy resources, mineral deposits, and migrating hydrothermal fluids in the region. The peculiar association of nickel and arsenic is reminiscent of the unusual Ni –Mo – PGE – Au deposits of China and the Yukon that are discussed above.
2. Relationship of ores to organics Clearly, organic constituents in rocks and fluids can be a source, a means of transport, or a cause of precipitation of ore constituents. For example, Parnell (2003) concludes that transport of ore metals such as Ti and Ni probably depended on the intervention of hydrocarbons at Craigs. Clark et al. (2003) favor a role for biogenesis in the development of barite ores. Munteanu et al. (2003) conclude that oxidation –
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reduction processes caused precipitation of Mn ore of the Carpathians and that organic matter influenced the style of subsequent metamorphism. Fan et al. (2003a,b) favor biogenic sources for at least part of the sulfur for Chinese tin and antimony deposits. In other cases, such as the Sukhoi Log deposit described by Distler et al. (2003), it is not at all clear whether a case can be made for any genetic connection between ore constituents and organic matter. In this regard, Peacor et al. (2000) showed that the vanadium contained by the Mecca Quarry Shale of Indiana is more strongly associated with illite than with organic matter. The paucity of metals in the massive Karelian shungite deposits reported by Melezhik et al. (2003) indicates that metal-rich basinal brines did not interact with the deposits. If any interaction had occurred, the shungite should be enriched in metals given the propensity of the material to adsorb metal and organic pollutants. Nevertheless, in some cases, such as the Sukhoi Log deposit described by Distler et al. (2003), it is not at all clear whether a case can be made for any genetic connection between ore constituents and organic matter. The papers in this volume clearly show the diversity of roles played (or not) by organic matter in the development of ore deposits and the evolution of sedimentary basins. The results also hint at the large of amount of research that remains to be done in this area of ore geochemistry.
Acknowledgements We thank the contributing authors for their efforts in providing articles concerning an unusually diverse set of deposits. Drs. Jaroslav Aichler, Frank B. Bierlein, Thomas A. Giordano, Bohdan Krˇibek, Richard Kyle, Ma´rta Polga´ri, Donald F. Sangster, Richard B. Schultz, Lee D. Slater, Jorge Spangenberg, and five other technical experts provided incisive peer reviews that were essential to the production of this volume. Ms. Sophia Sherman ably completed corrections of numerous drafts, reference checks, and final formatting of the manuscripts. We thank the organizers of IGC-31 for sponsoring symposium 11-3 and UNESCO for support of International Geological Correlations Progamme (IGCP) Project 429 on Ores and Organic Matter.
References Airo, M.L., Loukola-Ruskeeniemi, K., 2003. Characterization of sulfide deposits by airborne magnetic and gamma-ray responses in eastern Finland. Ore Geology Reviews 24, 67 – 84 (this volume). Buseck, P.R., Tsipursky, S.J., Hettich, R., 1992. Fullerenes from the geological environment. Science 257, 215 – 216. Clark, S.H.B., Poole, F.G., Wang, Z., 2003. Comparison of some sediment-hosted, stratiform barite deposits in China, the United States, and India. Ore Geology Reviews 24, 85 – 101 (this volume). Coveney Jr., R.M., 2000. Metalliferous shales and the role of organic matter with examples from China, Poland and the United States. In: Giordano, T.H., Kettler, R.M., Wood, S.A. (Eds.), Ore Genesis and Exploration: The Roles of Organic Matter. Reviews in Economic Geology, vol. 9. Society of Economic Geologists, Littleton, Colorado, USA, pp. 251 – 280. Distler, V.V., Yudovskaya, M.A., Mitrofanov, G.L., Prokof’ev, V.Yu., Lishnevskii, E.N., 2003. The Sukhoi Log noble metals deposit: geology, composition and genesis of mineralization. Ore Geology Reviews (this volume). Dozy, J.J., 1970. A geological model for the genesis of the lead – zinc ores of the Mississippi Valley, U.S.A. Institute of Mining and Metallurgy Transactions, Section B 79, 163 – 170. Fan, D., 1983. Polyelements in the lower Cambrian black shale series in southern China. In: Augustithis, S.S. (Ed.), The Significance of Trace Metals in Solving Petrogenetic Problems and Controversies. Theophrastus Publications, Athens, Greece, pp. 447 – 474. Fan, D., Tao, Z., Ye, J., Pasava, J., Krˇibek, B., Dobes, P., Varrin, I., Zak, K., 2003a. Geochemistry and origin of the giant tin-polymetallic sulfide deposits hosted in the Devonian black shale series in the Dachang region of Southern China. Ore Geology Reviews 24, 103 – 120 (this volume). Fan, D., Tao, K., Ye, J., 2003b. The giant Xikuangshan Sb-deposit hosted by the upper Devonian black shale series of Hunan, China. Ore Geology Reviews 24, 121 – 133 (this volume). Goodfellow, W.D., 1987. Anoxic stratified oceans as a source of sulphur in sediment-hosted stratiform Zn – Pb deposits (Selwyn Basin, Yukon, Canada). Chemical Geology (Isotope Geoscience Section) 65, 359 – 382. Goodfellow, W.D., 2002. A meteorite impact origin for Late Devonian Ni-PGE sulphide and associated tsunami deposits, northern Yukon Canada. Extended Abstracts for the IAGOD Meeting, Windhoek Namibia, August. Namibian Geological Society. 7 pp. Gustafson, L.B., Williams, N., 1981. Sediment-hosted stratiform deposits of copper, lead, and zinc. Economic Geology 75th Anniversary Volume, 139 – 178. Hulbert, L.J., Carne, R.C., Gregoire, D.C., Paktunc, D., 1992. Sedimentary nickel, zinc, and platinum-group-element mineralization in Devonian black shales at the Nick property, Yukon Canada: a new deposit type. Exploration and Mining Geology 1, 39 – 62. Kucha, H., 1982. Platinum group metals in Zechstein copper deposits. Economic Geology 77, 1578 – 1591.
Preface Laznicka, P., 1999. Quantitative relationships among giant deposits of metals. Economic Geology 94, 455 – 473. Lott, D.A., Coveney Jr., R.M., Murowchick, J.B., Grauch, R.I., 1999. Sedimentary exhalative nickel – molybdenum ores from south China. Economic Geology 94, 1051 – 1066. Mao, J., Lehmann, B., Du, A., Zhang, G., Ma, D., Wang, Y., Zeng, M., Kerrich, R., 2002. Re – Os dating of polymetallic Mo – PGE – Au mineralization in lower Cambrian black shales of southern China. Economic Geology 97, 1051 – 1061. Melezhik, V.A., Fillipov, M.M., Romanshkin, A.E., 2003. A giant Paleoproterozoic deposit of shungite in NW Russia: genesis and practical applications. Ore Geology Reviews 24, 135 – 154 (this volume). Munteanu, M., Marincea, S., Kasper, H.U., Zak, K., Alexe, V., Mihalache, A., Cristea, C., Trandafir, V., Saptefrati, G., Mihalache, A., 2003. Black chert-hosted manganese deposits from the eastern Carpathians of Romania: petrography, genesis and metamorphic evolution. Ore Geology Reviews (this volume). Parnell, J., 2003. Titanium mobilization by hydrocarbon fluids related to sill intrusion in a sedimentary sequence, Scotland. Ore Geology Review 24, 155 – 167 (this volume). Pasˇava, J., Krˇ´ıbek, B., 2001. Geochemistry of host rocks and role of organic matter in the precipitation of cassiterite – sulfide ores at the Dafulou deposit, Dachang tin field (south China). Bulletin of the Czech Geological Survey 76, 3 – 14. Pasˇava, J., Krˇ´ıbek, B., Dobesˇ, P., Zˇa´k, K., Fan, D., Zhang, T., Boiron, M.Ch., 2003. Tin-polymetallic sulfide deposits in the eastern part of the Dachang tin field (South China) and the role of black shales in their origin. Mineralium Deposita 38, 39 – 66.
5 Peacor, D.R., Coveney Jr., R.M., Zhao, G., 2000. Authigenic illite and organic matter: the principal hosts of vanadium in the Mecca Quarry Shale at Velpen Indiana. Clays and Clay Minerals 48, 311 – 316. Piestrzyn´ski, A., Wodzicki, A., 2000. Origin of the gold deposit in the Polkowice-West mine, Lubin-Sieroszowice mining district, Poland. Mineralium Deposita 35, 37 – 47. Sangster, D.F., 1990. Mississippi Valley-type and Sedex lead – zinc deposits—a comparative examination. Institution of Mining and Metallurgy Transactions, Section B, Applied Earth Sciences 99, 21 – 42. Searls, J.P., 2000. Barite: United States Geological Survey Minerals Yearbook. Chapter 10, 10.1-10.4. URL: http://minerals.usgs. gov/minerals/pubs/commodity/barite/. Zeng, M.A., 1998. Geological features of the Huangjiawan Ni – Mo deposit in Zunyi of Guizhou and its prospect for development. Guizhou Geology 16, 305 – 310.
Raymond M. Coveney Jr. * Department of Geoscience, University of Missouri, 420D Flarsheim Hall, Kansas City, MO, USA E-mail address: [email protected] Jan Pasˇava Czech Geological Survey, Prague, Czech Republic
* Corresponding author. Tel.: +1-816-2352980.
Preface
Diverse connections between ores and organic matter The world’s premier deposits of barite, copper, gold, iron, lead, and zinc occur in sedimentary basins (Laznicka, 1999). Many are associated with organicrich shales and hydrocarbons (Fig. 1). For example, the Pb and Zn ores of the American Mississippi Valley including the Viburnum Trend, the world’s largest known concentration of lead, occur on the peripheries of basins containing hydrocarbon deposits and black shales (Dozy, 1970; Coveney, 2000). Spatial correlations, among other factors, have led to inferences about critical roles for organic matter and organisms in sourcing, transporting, and depositing ores. However, in many cases, clear proof of a genetic relationship between ores and organic matter remains elusive—in some cases even dubious, despite spatial coincidence. The Selwyn Basin of western Canada and the Zechstein of northern Europe contain both carbonate-hosted deposits and sedimentary exhalative (sedex) deposits, which share many common characteristics, including transport of ore constituents by basinal brines (Sangster, 1990). Yet, certain major shale basins, such as those of the Mississippi Valley, USA, contain no known sedex ores, despite the presence of major carbonate-hosted lead – zinc deposits, black shales, and hydrocarbons. Moreover, some black shale basins appear to contain neither type of deposit, although this may be attributable to insufficient exploration. Besides the productive deposits alluded to above, stratified rocks contain other deposits that may be important in the future including non-placer resources of Au and platinum group elements (PGE). For example, Kucha (1982) reported remarkably rich centimeter-scale Au and PGE laminae in the Kupferschiefer of Poland, which are not economic because of their thinness. Nevertheless, his results led to further studies and the discovery of significant Au minerali0169-1368/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.oregeorev.2003.08.002
zation in the accompanying Rote Fa¨ule facies in the same mining district (Piestrzyn´ski and Wodzicki, 2000), which may become an important source of precious metals. Similar possibilities exist for the unusual decimeter-scale beds of Ni, Mo, As, and Zn sulfides containing PGE and Au in China (Fan, 1983) and the Yukon (Hulbert et al., 1992) (Fig. 1). Their possible economic value is supported by reports of thicknesses up to 1 m for the deposits in Guizhou, China (Zeng, 1998; Mao et al., 2002). Moreover, Goodfellow (2002) has documented three new occurrences in the Yukon, separated by 400 km. These workers suggest that the deposits may have been deposited from normal sea water or in the wake of an asteroid impact, respectively, but others favor comparatively prosaic sedex origins (e.g., Hulbert et al., 1992; Lott et al., 1999).
1. Summaries of articles The eight articles contained in this special issue of Ore Geology Reviews are a sampling of 35 oral and poster presentations given in symposium 11-3, Mineral Deposits Associated with Black Shales, at the 31st International Geological Congress (IGC-31) held in August 2000 in Rio de Janeiro, Brazil. The contributions cover Au, Mn, Cu, Hg, Zn, Ni, Sn, Sb, and barite deposits hosted by sedimentary or metasedimentary rocks (Fig. 1). Two occurrences of organic matter are described: (1) the exceptionally large, and possibly unique, shungite deposits hosted by Proterozoic strata in Russia and (2) a showing of metalliferous bitumen located not far from a former lead – silver – nickel mine in Scotland. Victor A. Melezhik, M.M. Filippov, and A.E. Romashkin describe the unique deposits of Russian
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Fig. 1. Locations of deposits. Airo and Loukola-Ruskeeniemi (2003) propose a means for locating massive sulfide deposits by geophysical techniques that partly depend on their organic contents. Munteanu et al. (2003) review sediment-hosted Mn deposits associated with black shales in the Eastern Carpathian Mountains of Romania. The world’s preeminent giant deposits of barite are located in China and India, but it is unclear which of these deposits is largest. Three of these, the Qinling and Jiangnan deposits of China, and the Mangampeta deposit of India, as well as the Nevada Barite Belt deposits, are reviewed by Clark et al. (2003). Distler et al. (2003) thoroughly cover the giant Au – PGE lode deposit hosted by metamorphosed black shales at Sukhoi Log in Siberia. Fan et al. (2003a,b) discuss the influences of organic matter in the formation of both the tin deposits at Dachang and the world’s largest antimony deposits at Xikuangshan, China. The peculiar carbon-rich material, known as shungite, that may be a source of fullerenes occurs in the Karelian region of Russia (Melezhik et al., 2003). A minor but interesting occurrence of metal-rich bitumen from Scotland illustrates the mobility of Ti in basinal brines (Parnell, 2003). The illustration shows the locations major sedimentary basins containing metalliferous black shales with respect to the positions of the world’s largest ore deposits for various commodities. Locations of premier deposits and black shale basins are taken from Gustafson and Williams (1981), Goodfellow (1987), Sangster (1990), Laznicka (1999), and Coveney (2000). The locations of the world’s largest deposits of 14 metals, Sb, and barite are from Sangster (1990), Laznicka (1999), and Searls (2000).
Karelia that contain shungite, which can be used to extract aqueous pollutants and to make shungisite, a lightweight insulating material. Fullerenes were first reported from nature from these deposits by Buseck et al. (1992), but the likelihood of commercial extraction of this extremely valuable commodity is clouded by uncertainty over the quantity of natural fullerenes that are present. Nevertheless, even if commercial amounts of fullerenes are not present, Melezhik et al. (2003) suggest that the deposits may provide a useful raw material for synthesis of fullerenes. Marian Munteanu, Stefan Marincea, Haino Uwe Kasper, Karel Zak, Veronica Alexe, Angela Mihalache, Corina Cristea, Vasile Trandafir, George Sapte-
frati, Cristian Simionescu, and Danuzia Airinei propose that the East Carpathian manganese deposits of Romania were deposited in an environment located near the interface between anoxic bottom waters and overlying oxic seawater. They discount the importance of supergene processes in the development of Mn oxide ores that have been postulated by others. Delian Fan, Tao Zhang, and Jie Ye discuss the enormous Xikuangshan deposit, of Hunan, China, the world’s largest source of antimony (Laznicka, 1999). This deposit is hosted by Devonian Sb-rich black shale, rich in organic carbon that accumulated during anoxic sedimentation (Fan et al., 2003a). With her collaborators, Tao Zhang, Jie Ye, Jan Pasˇava, Bohdan
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Krˇibek, P. Dobes, I. Varrin, and K. Zak, Delian Fan also covers the Dachang Sn-polymetallic deposits hosted by Devonian black shales of Guangxi, China, which are second in production only to the Malaysian placer Sn deposits (Laznicka, 1999). Fan et al. (2003b) favor a biogenic source for sulfur for some of the tin deposits but infer an igneous source for sulfur in other cases based on isotopic data. Pasˇava and Krˇ´ıbek (2001) and Pasˇava et al. (2003) have provided additional evidence for the active involvement of black shales and organic matter in the origin of tin-polymetallic deposits in the Dachang mining district. Devonian black shales were a likely source of S and in part for Sb, Co, Pb, V, and Fe during ore deposition at the Dafulou, Huile, and Kangma cassiterite-sulfide deposits in the eastern part of the district. Black shales also played an important role in controlling the deposition of remobilized and epigenetic replacement-type sulfide Sn mineralization related to granitic intrusions. At the Dafulou deposit, geochemical studies show that in situ organic matter locally interacted with hydrothermal solutions to decrease the fO2 and form massive pyrrhotite ores and pyrobitumen that are generally absent in other deposits located in the eastern part of the district. Pasˇava et al. (2003) suggested that black shales at the Dachang ore district may have controlled deposition of the ores associated with the Longxianggai granite by inducing low fO2 conditions at the exocontact, which may have resulted in the accumulation of Sn2 + in the residual melt and the formation of high-Ca black shale or carbonate-replacement tin-sulfide ores distal to the intrusion. The contribution by Vadim V Distler, Marina A. Yudovskaya, Gennady L. Mitrofanov, Vsevolod Y. Prokof’ev, and Eric N. Lishnevskii covers the Ptbearing gold deposit at Sukhoi Log in Siberia, which contains an estimated 1100 tons of Au. Although the Sukhoi Log deposit is comparatively rich in organic matter, no significant correlation exists between grades for Au, or for that matter Pt, and total organic matter. The lodes of Sukhoi Log may have been an important source of precious metals for major placer deposits that have been mined in the area for many years. Meri-Liisa Airo and Kirsti Loukola-Ruskeeniemi demonstrate the use of high-resolution geophysical techniques to find favorable environments for massive
3
sulfide ores, such as those of Outokumpu, in the Proterozoic of eastern Finland. Such techniques, which partly depend upon the presence or absence of graphite formed from organic matter, may be critically important for effective exploration of areas where outcrops are rare because of glacial cover, deep weathering, or other causes. Sandra H.B. Clark, Forest G. Poole, and Zhongcheng Wang compare the geologic settings and genesis of barite deposits from including several from the world’s most productive barite mining regions including the Yangtze Platform of China from which more than half of current barite production is derived (Searls, 2000) and the huge Mangampeta barite deposit of Andhra Pradesh, India. Clark et al. (2003) round out their survey with the Nevada Barite Belt, which has become the chief supplier of domestic barite in the United States, surpassing Missouri and other formerly important sources. Geochemical results and comparisons with barite occurrences currently being formed off the coast of California lead the authors to conclude that major barite deposits can be formed by either sedex hydrothermal or biogenic processes. John Parnell’s study shows that titanium can be readily mobilized in pore fluids. The Craigs, Scotland, occurrence of bitumen is located within 500 m of a small mine that formerly produced nickel, lead, and silver, suggesting the possibility of genetic connections. Mixed hydrocarbon – brine fluid inclusions testify to the interrelationships among energy resources, mineral deposits, and migrating hydrothermal fluids in the region. The peculiar association of nickel and arsenic is reminiscent of the unusual Ni –Mo – PGE – Au deposits of China and the Yukon that are discussed above.
2. Relationship of ores to organics Clearly, organic constituents in rocks and fluids can be a source, a means of transport, or a cause of precipitation of ore constituents. For example, Parnell (2003) concludes that transport of ore metals such as Ti and Ni probably depended on the intervention of hydrocarbons at Craigs. Clark et al. (2003) favor a role for biogenesis in the development of barite ores. Munteanu et al. (2003) conclude that oxidation –
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Preface
reduction processes caused precipitation of Mn ore of the Carpathians and that organic matter influenced the style of subsequent metamorphism. Fan et al. (2003a,b) favor biogenic sources for at least part of the sulfur for Chinese tin and antimony deposits. In other cases, such as the Sukhoi Log deposit described by Distler et al. (2003), it is not at all clear whether a case can be made for any genetic connection between ore constituents and organic matter. In this regard, Peacor et al. (2000) showed that the vanadium contained by the Mecca Quarry Shale of Indiana is more strongly associated with illite than with organic matter. The paucity of metals in the massive Karelian shungite deposits reported by Melezhik et al. (2003) indicates that metal-rich basinal brines did not interact with the deposits. If any interaction had occurred, the shungite should be enriched in metals given the propensity of the material to adsorb metal and organic pollutants. Nevertheless, in some cases, such as the Sukhoi Log deposit described by Distler et al. (2003), it is not at all clear whether a case can be made for any genetic connection between ore constituents and organic matter. The papers in this volume clearly show the diversity of roles played (or not) by organic matter in the development of ore deposits and the evolution of sedimentary basins. The results also hint at the large of amount of research that remains to be done in this area of ore geochemistry.
Acknowledgements We thank the contributing authors for their efforts in providing articles concerning an unusually diverse set of deposits. Drs. Jaroslav Aichler, Frank B. Bierlein, Thomas A. Giordano, Bohdan Krˇibek, Richard Kyle, Ma´rta Polga´ri, Donald F. Sangster, Richard B. Schultz, Lee D. Slater, Jorge Spangenberg, and five other technical experts provided incisive peer reviews that were essential to the production of this volume. Ms. Sophia Sherman ably completed corrections of numerous drafts, reference checks, and final formatting of the manuscripts. We thank the organizers of IGC-31 for sponsoring symposium 11-3 and UNESCO for support of International Geological Correlations Progamme (IGCP) Project 429 on Ores and Organic Matter.
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Raymond M. Coveney Jr. * Department of Geoscience, University of Missouri, 420D Flarsheim Hall, Kansas City, MO, USA E-mail address: [email protected] Jan Pasˇava Czech Geological Survey, Prague, Czech Republic
* Corresponding author. Tel.: +1-816-2352980.