Magmatic fluids, both vapour and hypersaline liquid, are a primary source of many components in hydrothermal ore deposits formed in volcanic arcs. These components, including metals and their ligands, become concentrated in magmas in various ways from various sources, including subducted oceanic crust. Leaching of rocks also contributes components to the hydrothermal fluid—a process enhanced where acid magmatic vapours are absorbed by deeply circulating meteoric waters. Advances in understanding the hydrothermal systems that formed these ore deposits have come from the study of their active equivalents, represented at the surface by hot springs and volcanic fumaroles.

The role of magmas in the formation of hydrothermal ore deposits

Geological atlas of western and central Europe

▪ Abstract Manganese(IV) oxides produced through microbial activity, i.e., biogenic Mn oxides or Mn biooxides, are believed to be the most abundant and highly reactive Mn oxide phases in the environment. They mediate redox reactions with organic and inorganic compounds and sequester a variety of metals. The major pathway for bacterial Mn(II) oxidation is enzymatic, and although bacteria that oxidize Mn(II) are phylogenetically diverse, they require a multicopper oxidase-like enzyme to oxidize Mn(II). The oxidation of Mn(II) to Mn(IV) occurs via a soluble or enzyme-complexed Mn(III) intermediate. The primary Mn(IV) biooxide formed is a phyllomanganate most similar to δ-MnO2 or acid birnessite. Metal sequestration by the Mn biooxides occurs predominantly at vacant layer octahedral sites.

Biogenic manganese oxides: Properties and mechanisms of formation

Mechanism of molybdenum removal from the sea and its concentration in black shales: EXAFS evidence

Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols

The Kupferschiefer, a thin (<4 m) bed of marine bituminous marl of Upper Permian (Zech-stein) age, occurs over a large area of north-central Europe and has, in certain areas, been exploited for silver and some base metals, notably copper, since medieval times. It has been regarded as the type example of a shale-hosted, strata-bound sulfide deposit and theories regarding the origins of Kupferschiefer mineralization have exerted considerable influence on theories of ore genesis.The Kupferschiefer sediments were deposited following a rapid marine transgression over an area that had been subject to a very long period of arid to semi-arid conditions. In many areas the Kupferschiefer overlies red-bed sediments (Rotliegende), but in others it overlies Carboniferous sandstones and marls or the bleached and reworked equivalents of earlier rocks (Grauliegende and Weissliegende). Within the Kupferschiefer, lithologieal variations can be related to detailed paleogeography. Overall a euxinic, sapropelic facies predominates, but changes occur in the region of paleohighs where more carbonate and clastic-rich facies are developed. Strong evidence exists for the development of chemical stratification in the Zech-stein sea (from which the Kupfersehiefer was deposited) with oxidizing conditions in the upper part and reducing conditions in the lower part. Everywhere the Kupferschiefer grades upward into overlying dolomitie limestones.Although large areas of the Kupferschiefer contain only average concentrations of base and precious metals compared to other shales and marls, in certain areas the concentrations reach ore grade. Historically, the Mansfeld district (SE Harz Mountains) was important for copper and silver mining, but at present-day mining is undertaken only in the Spremberg-Weisswasser area (East Germany) and in Lower Silesia (Poland). The ores in such regions contain sulfides of Cu, Pb, and Zn and may be enriched in a variety of other elements, notably V, Mo, U, Ag,As, Sb, Bi, and Se; Cd, Tl, Au, Re, and the platinum-group metals are also reported; lateral and vertical zoning of Cu, Pb, and Zn may be observed; and in some areas, a reddening of the rocks adjacent to ores (Rote Fule facies) is a useful exploration guide. The Kupfersehiefer in Poland, in two contrasting regions in Germany (the Lower Rhine basin and the Hessian depression) and in England (where it is termed the Marl Slate) are compared and provide evidence for four types of mineralization.The first (and oldest) is a weakly mineralized type exemplified by the English Marl Slate. Average base metal content of this type is approximately 100 ppm. Detailed mineralogieal, geochemical, and isotopic studies indicate that the mineralization is synsedimentary; these studies have enabled a model to be developed in which precipitation of the various mineral phases can be related to stratification of the early Zeehstein sea and oscillations in water and oxic-anoxic boundary levels.The second is an average mineralization involving base metal content at the 2,000-ppm level. In this ease, the study of German examples indicates the important influence of strata underlying the Kupferschiefer, as stressed by subdivision into a basin type that overlies thick Rotliegende sediments, and a schwellen type that overlies Paleozoie basement. The two subtypes differ in mineralogy and overall base metal ratios, indicating the importance of underlying strata as a source of metals. The relationship between barium concentrations in the Kupferschiefer and barite mineralization in underlying rocks is also clear from geochemical (including Sr isotope) studies of German examples. The evidence points to an early diagenetic origin for the average mineralization, with sulfur derived bacteriogenically interacting with low-temperature solutions deriving metals largely from immediately underlying rocks.The third is an ore mineralization where the average base metal concentration reaches approximately 3 percent. Zonation is clearly developed, as is the association of the Rote Faeule facies with mineralization, although the detailed zoning patterns are more complex than commonly believed. The ore mineralization type is generally restricted to the regions representing the margins of Rotliegende basins, and models of origin associated with late diagenetic processes and the introduction of metal-rich brines (possibly associated with basin compaction) are in line with the geologic and geochemical evidence. Preliminary fluid inclusion data on strata associated with the mineralization point to temperatures of approximately 120 degrees C, and organic maturation studies can also be used to support models involving introduction of oxidative metal-rich brines during late diagenesis. Again, sulfur isotope data point to fixation of the metals by sulfur derived from bacterial reduction of sulfate. The fourth mineralization associated with the Kupferschiefer is a much later (postdiagenetic) structure-controlled mineralization (Ruecken) involving Co, Ni, Ba, As, and Ag phases, genetically distinct from the types mentioned above and of probable hydrothermal origin. Other possible episodes of mineralization can be identified on a local scale; in many cases insufficient data are available to assess their genetic significance.The Kupferschiefer is a deposit that appears to be the product of a variety of mineralizing processes influenced by the environment of deposition of the host rock and the underlying geology, but there are many unifying features; notably, that the bulk of the evidence still points to fixation of metals as sulfides by bacteriogenic processes.

The Kupferschiefer; an overview with an appraisal of the different types of mineralization

Lead isotope ratios of galena from the carbonate-hosted massive sulphide deposits of Kabwe (Pb-Zn) and Tsumeb (Pb-Zn-Cu) in Zambia and Namibia, respectively, have been measured and found to be homogeneous and characteristic of upper crustal source rocks. Kabwe galena has average isotope ratios of 206/204Pb = 17.997 ± 0.007, 207/204Pb = 15.713 ± 0.010 and 208/204Pb = 38.410 ± 0.033. Tsumeb galena has slightly higher 206/204Pb (18.112 ± 0.035) and slightly lower 207/204Pb (15.674 ± 0.016) and 208/204Pb (38.276 ± 0.073) ratios than Kabwe galena. The isotopic differences are attributed to local differences in the age and composition of the respective source rocks for Kabwe and Tsumeb. The homogeneity of the ore lead in the two epigenetic deposits suggests lead sources of uniform isotopic composition or, alternatively, thorough mixing of lead derived from sources with relatively similar isotopic compositions. Both deposits have relatively high 238U/204Pb ratios of 10.31 and 10.09 for Kabwe and Tsumeb galenas, respectively. These isotope ratios are considered to be typical of the upper continental crust in the Damaran-Lufilian orogenic belt, as also indicated by basement rocks and Cu-Co sulphides in stratiform Katangan metasediments which have a mean μ-value of 10.25 ± 0.12 in the Copperbelt region of Zambia and the Democratic Republic of Congo (formerly Zaire). The 232Th/204Pb isotope ratios of 43.08 and 40.42 for Kabwe and Tsumeb suggest Th-enriched source regions with 232Th/235U (κ-values) of 4.18 and 4.01, respectively. Model isotopic ages determined for the Kabwe (680 Ma) and Tsumeb (530 Ma) deposits indicate that the timing of the mineralisation was probably related to phases of orogenic activity associated with the Pan-African Lufilian and Damaran orogenies, respectively. Galena from the carbonate-hosted Kipushi Cu-Pb-Zn massive sulphide deposit in the Congo also has homogeneous lead isotope ratios, but its isotopic composition is comparable to that of the average global lead evolution curve for conformable massive sulphide deposits. The μ (9.84) and κ (3.69) values indicate a significant mantle component, and the isotopic age of the Kipushi deposit (456 Ma) suggests that the emplacement of the mineralisation was related to a post-tectonic phase of igneous activity in the Lufilian belt. The isotope ratios (206/204Pb, 207/204Pb, 208/204Pb) of the three deposits are markedly different from the heterogeneous lead ratios of the Katangan Cu-Co stratiform mineralisation of the Copperbelt as well as those of the volcanogenic Nampundwe massive pyrite deposit in the Zambezi belt which typically define radiogenic linear trends on lead-lead plots. The host-rock dolomite of the Kabwe deposit also has homogeneous lead isotope ratios identical to the ore galena. This observation indicates contamination of the Kabwe Dolomite Formation with ore lead during mineralisation.

Lead isotopes of the carbonate-hosted Kabwe, Tsumeb, and Kipushi Pb-Zn-Cu sulphide deposits in relation to Pan African orogenesis in the Damaran-Lufilian fold belt of Central Africa

The distribution of rare earth and minor elements in manganese nodules and sediments from the equatorial and S.W. Pacific

I Deposits in Mafic and Ultramafic Complexes.- The Physical and Petrologie Setting and Textural and Compositional Characteristics of Sulfides from the South Kawishiwi Intrusion, Duluth Complex, Minnesota, USA.- Application of Stable Isotopic Studies to Problems of Magmatic Sulfide Ore Genesis with Special Reference to the Duluth Complex, Minnesota.- Controls on the Formation of Komatiite-Associated Nickel-Copper Sulfide Deposits.- Depositional Environments of Volcanic Peridotite-Associated Nickel Sulphide Deposits with Special Reference to the Kambalda Dome.- Geochemistry of the Sudbury Igneous Complex: A Model for the Complex and Its Ores.- Sulfide Petrology and Genesis of Copper-Nickel Ore Deposits.- Types and Distinctive Features of Ore-Bearing Formations of Copper-Nickel Deposits.- On the Role of Metamorphism in the Formation of Nickel-Copper Sulfide Deposits in the Kola Peninsula.- The Gabbro-Wehrlite Association in the Eastern Part of the Baltic Shield.- Peridotitic Komatiites and the Origin of Ores (Southeastern Part of the Baltic Shield).- Geologic Setting of Selected Chromium and Nickel Deposits of China.- II Porphyry Deposits.- Recent Advances in Porphyry Base Metal Deposit Research.- The Geochemical Behaviour of Copper and Molybdenum in Ore-Forming Processes.- Batholith-Volcano Coupling in the Metallogeny of Porphyry Copper Deposits.- Space-Time Distribution, Crustal Setting and Cu/Mo Ratios of Central Andean Porphyry Copper Deposits: Metallogenic Implications.- Metallogenic Zoning of Volcano-Plutonic Belts and Porphyry-Copper Mineralization.- Geological and Structural Conditions of Localization of the High-Grade Ores of Porphyry Copper Deposits.- Elements Determining in the Geological-Structural Model of the Erdenetuin-Obo Copper-Molybdenum Ore Field, Mongolia.- Genetic Aspects of the Recsk Mineralized Complex, Hungary.- Ore-Magmatic Systems of Copper-Molybdenum Deposits.- III Deposits of Volcanic-Hydrothermal Association.- Base Metal Deposits in the Iberian Pyrite Belt.- Copper-Pyrite and Pyrite Base Metal Deposits of the Caucasian Region.- The Hidden Mineralogical and Geochemical Zoning and the Ore-Forming Conditions of Copper and Copper- Lead-Zinc Massive Sulfide Deposits.- Zoning of Massive Sulphide Deposits and their Origin.- Physico-Chemical Conditions of Base Metal Sulphide Ore Formation.- On the Genesis of Barite Associated with Volcanogenic Massive Sulfides, Fukazawa Mine, Hokuroku District, Japan.- IV Sediment-Hosted Deposits.- Diagenetic Features at White Pine (Michigan), Redstone (N. W. Territories, Canada) and Kamoto (Zaire). Sequence of Mineralization in Sediment-Hosted Copper Deposits (Part 1).- Diagenetic Sulphide Mineralization Within the Stratiform Copper-Cobalt Deposit of West Kambove (Shaba- Zaire). Sequence of Mineralization in Sediment-Hosted Copper Deposits (Part 2).- Geochemical Aspects of Stratiform and Red-Bed Copper Deposits in the Catskill Formation (Pennsylvania, USA) and Redstone Area (Canada). Sequence of Mineralization in Sediment-Hosted Copper Deposits (Part 3).- Stratabound Copper Deposits in East South-Central Alaska: Their Characteristics and Origin.- Major Element Geochemistry of the Host Rocks in Some Sediment-Hosted Copper Deposits.- Zechstein Copper-Bearing Shales in Poland. Lagoonal Environments and the Sapropel Model of Genesis.- Formation Conditions of Copper Sandstone and Copper-Shale Deposits.- Major Types of Copper-Bearing Zones in the Soviet Union.- Red-Colored Terrigenous Sediments - Specific Copper- Forming Systems.- Cupriferous Sandstones and Shales of the Siberian Platform.- Genetic Types of Copper Mineralization in the Igarka Area, West of the Siberian Platform.- The Diverse Styles of Sediment-Hosted Copper Deposits in Australia.- Mineral Zoning in Sediment-Hosted Copper-Iron Sulfide Deposits - A Quantitative Kinetic Approach.- Results of Recent Exploration for Copper-Silver Deposits in the Kupferschiefer of West Germany.

Günther Friedrich

Papers

The Kupferschiefer; an overview with an appraisal of the different types of mineralization

Lead isotopes of the carbonate-hosted Kabwe, Tsumeb, and Kipushi Pb-Zn-Cu sulphide deposits in relation to Pan African orogenesis in the Damaran-Lufilian fold belt of Central Africa

The distribution of rare earth and minor elements in manganese nodules and sediments from the equatorial and S.W. Pacific

Geology and metallogeny of copper deposits

The manganese nodule belt of the Pacific Ocean : geological environment, nodule formation, and mining aspects