Massive Sulfide Ore Research Articles

Integrating geologic and satellite imagery data for high-resolution mapping and gold exploration targets in the South Eastern Desert, Egypt

The granitoid-greenstone belts of the Arabian–Nubian Shield are well-endowed with lode gold and massive sulfide ores. Although generally characterized by excellent outcrops and arid desert realm, poor accessibility and lack of finance have been always retardant to detailed geologic mapping of vast areas of the shield. Lack of comprehensive geological information and maps at appropriate scales would definitely hinder serious exploration programs.In this study, band ratioing, principal component analysis (PCA), false-color composition (FCC), and frequency filtering (FFT-RWT) of ASTER and ETM+ data have substantially improved visual interpretation for detailed mapping of the Gebel Egat area in South Eastern Desert of Egypt. By compiling field, petrographic and spectral data, controls on gold mineralization have been assessed in terms of association of gold lodes with particular lithological units and structures. Contacts between foliated island arc metavolcanics and ophiolites or diorite are likely to be favorable loci for auriferous quartz veins, especially where the NW–SE foliation is deflected into steeply dipping NNW-trending shear planes. High-resolution mapping of the greenstone belt, structures and alteration zones associated with gold lodes in the study area suggests that dilatation by foliation deflection was related to emplacement of the Egat granitic intrusion, attendant with a sinistral transpression regime (i.e., ∼640–550Ma?). Gold mineralization associated with granitoid intrusions in transpression-induced pull-apart structures elsewhere in the Eastern Desert (e.g., Fawakhir, Sukari and Hangaliya mines) emphasize the reliability of this setting as a model for gold exploration targets in greenstone terrains of Egypt, and may be elsewhere in the Arabian–Nubian Shield.

Pyrite mine waste and water mapping using Hymap and Hyperion hyperspectral data

Hyperspectral low spatial resolution Hyperion data are used to map mine waste from massive sulphide ore deposits, mostly abandoned, on the Iberian Pyrite Belt. Hymap high spatial resolution data are used for crossed interpretation. Mine dams, mill tailings and mine dumps in a variable state of pyrite oxidation are recognizable. Ponds of acid water in the mine sites are spectrally outstanding and, with simple image processing procedures, mappable. In addition, acid water with different chemical composition is mappable with hyperspectral data, whether of high or low spatial resolution. A sequence of hyperspectral image processing algorithms used to produce the maps is suggested. Therefore, hyperspectral data are invaluable in giving quick hints on the quality of the rapidly changing state of the contamination generated by sulphide mine waste, enabling the authorities to activate mitigation procedures.

Zircon dating, Hf–Sr–Nd–Os isotopes and PGE geochemistry of the Tianyu sulfide-bearing mafic–ultramafic intrusion in the Central Asian Orogenic Belt, NW China

The Tianyu mafic–ultramafic intrusion is one of many important sulfide-bearing mafic–ultramafic intrusions in the eastern Tianshan terrane located in the southern margin of the Central Asian Orogenic Belt in north Xinjiang, NW China. The origin of sulfide mineralization in these intrusions, their relationship with Permian basalts and A-type granites, and the geodynamic setting of the bimodal magmatism in the region are controversial. In this paper we use zircon U–Pb age, Hf–Sr–Nd–Os isotope and lithophile–chalcophile trace element constraints from the Tianyu mafic–ultramafic intrusion to address these important issues. The U–Pb age of zircon from the Tianyu intrusion determined by SIMS is 280 ± 2 Ma. This confirms that the Tianyu intrusion is coeval with most sulfide-bearing mafic–ultramafic intrusions and some basalts and A-type granites in the Tianshan region. Similar to coeval basalts in the nearby Tuha basin, the Tianyu intrusive rocks are characterized by negative Nb anomaly and elevated ε Nd values varying between − 1 and + 4.6. The negative Nb anomaly in the Tianyu intrusion is not as pronounced as in the coeval A-type granites but the ε Nd values for these bimodal rocks are similar. The ε Hf values of zircon from the Tianyu intrusion are positive, varying between 3 and 8. These values suggest that the parental magma of the Tianyu intrusion was dominated by melt derived from a depleted source mantle. The γ Os values of pyrrhotite from the Tianyu intrusion are high, ranging from 725 to 995, which can be modeled by selective assimilation of sulfide from the lower and upper crusts. Negative Pt anomaly is present in relatively sulfide-rich samples such as semi-massive and massive sulfide ores but not in sulfide-poor samples, which is more consistent with the effect of post-magmatic hydrothermal alteration than the original signature of the parental magma. The results of modeling using the compositions of selected disseminated sulfide samples suggest that the parental magma of the Tianyu intrusion was depleted in all PGE, which is consistent with previous sulfide segregation at depth. Our data and modeling results support the model of decompression melting of upwelling asthenosphere due to slab break-off during a transition from oceanic subduction to arc–arc or arc–continent collision in the Permian. Decompression melting of the upwelling asthenosphere in the region produced mafic magma. Partial melting in the lower parts of a juvenile arc crust due to mafic magma underplating produced granitic melts. Mixing of the mafic magma with a small amount of granitic melts at depth followed by contamination with the upper crust at a higher level formed the parental magma of the Tianyu intrusion. PGE depletion in the parental magma of the Tianyu intrusion can be attributed to sulfide segregation associated to the first stage of crustal contamination at depth. We suggest that the formation of sulfide ores in the intrusion was related to the second stage of crustal contamination in the upper crust.

The golden geyser – Robert Logan Jack and the geology of Mount Morgan, Queensland

In 1884 the highly respected Queensland Government Geologist, Robert Logan Jack, was sent to inspect and report on a new gold discovery at Mount Morgan in central Queensland. The find was rumoured to be both rich and geologically unique. Jack was bewildered by the form, structure and exceptional richness of the ore that was being quarried in bulk from the summit of Mount Morgan and in response he proposed the radical theory that the deposit represented the outpourings of an extinct gold-bearing thermal spring. The surface ore was in reality the enriched supergene zone of a massive sulphide ore body, a fact that became more and more evident as the deposit was opened up by subsequent mining activity. Jack's theory of a gold spouting geyser, however, had captured the public imagination, and this, as well as factors related to Jack himself and his relationship with the Mount Morgan Gold Mining Company, gave the theory a life well beyond that justified by the growing evidence of the true nature of the deposit.

Geology and Geochemistry of Highly Metamorphosed Footwall Alteration Zones in the Hongtoushan Volcanogenic Massive Sulfide Deposit, Liaoning Province, China

AbstractThe Hongtoushan Archean Cu–Zn volcanogenic massive sulfide (VMS) deposit, which was metamorphosed (3.0–2.8 Ga) to upper amphibolite facies at temperatures between 600 and 650°C, occurs in the Hunbei granite–greenstone terrane, Liaoning Province of NE China. Stratiform cordierite–anthophyllite gneiss (CAG) that occurs hundreds of meters below the ore horizon in the Hongtoushan district corresponds to the metamorphosed semi‐conformable alteration zone of the VMS hydrothermal system, whereas the CAG that contains abundant deformed sulfide‐bearing quartz veins immediately below the main ore layer represents the metamorphosed discordant alteration zone. Whole‐rock geochemistry indicates that stratiform CAG was derived ultimately from five lithologies (basalt, basaltic andesite, andesite, dacite, and rhyolite), while discordant CAG derived from a single lithology (rhyolite). Amphibolite and biotite‐rich gneiss are identified as a metamorphosed least‐altered precursor for these CAGs. Mass change calculation indicates that, compared to the least‐altered rocks, stratiform CAG is enriched in Fe and Mg, and depleted in Na, K, Ca, Cu, Pb and Zn, while discordant CAG is enriched in Fe, Mg, Si, Na, Pb, Cu and Zn, and depleted in K. HREE and HFSE (Zr, Ti, Nb and Ta) behaved inertly during submarine alteration, whereas Rb, Sr, Ba and LREE (especially Eu) were leached off.Both stratiform and discordant CAGs are depleted in 18O, with values up to 7‰ lower than their corresponding least‐altered precursors. Addition of Fe, Mg, and depletion of Ca, K, Sr, and 18O, indicate that hydrothermal alteration for both types of CAGs was characterized by chloritization prior to metamorphism. Stratiform CAG could be used to evaluate the mineralization potential of VMS in metamorphic terranes, while discordant CAG containing sulfide‐bearing quartz veins could be a good indication for overlying stratiform massive sulfide ores as well as an exploration target itself.

Age and primary architecture of the Copperton Zn-Cu VMS deposit, Northern Cape Province, South Africa

The Prieska Copper Mine (Copperton) deposit, located in the Northern Cape Province of South Africa, exploited from 1972 to 1994 a very large (ca. 47 Mt pre-mining resource) massive sulphide lens containing on average ca. 1% Cu and 2% Zn. The orebody occurred as a stratiform/stratabound tabular lens hosted by the subvertically dipping Copperton Formation, which is part of the intensely deformed and highly metamorphosed Areachap Group. The latter represents a 1.3-1.24 Ga continental volcanic island arc that was accreted onto the western margin of the Kaapvaal Craton during the initial stages of the 1.2-1.0 Ga Namaquan Orogeny. The present contribution is aimed at resolving important uncertainties surrounding the architecture, age and origin of this world class base metal deposit. Despite intense deformation and high-grade metamorphism the original architecture of the deposit is found to be unusually well preserved, with a stratabound zone of intense hydrothermal alteration below, and a series of characteristic cap rocks above the massive sulphide orebody. Geochemical data and radiometric ages for host rocks and massive sulphide ores lead to the conclusion that the Copperton deposit comprises a very large chimney-type volcanogenic massive sulphide deposit that formed at 1.28-1.29 Ga. The deposit meets many of the criteria of the bimodal-siliciclastic or bimodal-felsic types of VMS deposits.

The carbonate-hosted willemite prospects of the Zambezi Metamorphic Belt (Zambia)

Zambian willemite (Zn2SiO4) deposits occur in the metasedimentary carbonate rocks of the Proterozoic Katangan Supergroup. The most important orebodies are located around Kabwe and contain both sulphides and willemite in dolomites of low metamorphic grade. The Star Zinc and Excelsior prospects (Lusaka area), discovered in the early 1920s, occur in the metamorphic lithotypes of the late Proterozoic Zambezi Supracrustal sequence, which were deposited in a transtensional basin formed during the oblique collision of the Kalahari and Congo cratons. The deposits are hosted by the limestone and dolomitic marbles of the Cheta and Lusaka Formations. Structural analysis indicates that several fracture sets host the deposits, which may be genetically related to the Pan-African Mwembeshi dislocation zone (a major geotectonic boundary between the Lufilian Arc and the Zambezi Belt). In both prospects, willemite replaces the marbles and is found along joints and fissures with open-space filling textures and locally may develop colloform and vuggy fabrics as well. Silver as well as traces of germanium and cadmium have been detected within the willemite ore, and lead or zinc sulphides are scarce or absent. Calcite locally replaces willemite. Willemite is associated with specular hematite and franklinite and post-dates the Zn-spinel gahnite in the paragenesis. Genthelvite [Zn4Be3(SiO4)3S] occurs as a minor phase in irregular aggregates. The willemites from the Lusaka area, though Mn-poor, show green cathodoluminescence colours and bright green fluorescence in short-wave UV (as the high-temperature willemites in USA). Thermometric analyses of primary fluid inclusions in willemite yield homogenization temperatures that range from 160°C to 240°C and salinities of 8–16 wt.% equiv. NaCl. The homogenization temperatures suggest a hypogene–hydrothermal origin for the willemite concentrations. The geochemistry of fluid inclusion leachates suggests that the hydrothermal fluids were brines derived from highly evaporated seawater. Precise age constraints are currently lacking for the Lusaka area deposits, though the deposits are not deformed, indicating that they post-date the Lufilian orogeny (~520 Ma). The possibility of precursor ores exists; the gahnite–franklinite–willemite deposits could have been derived from a metamorphosed primary sulphide (or even nonsulphide) concentration that has subsequently been completely destroyed. However, there is no real evidence of such a primary source for the willemite mineral association. The Lusaka zinc ores may have been produced by an extensive hydrothermal system, with fluids discharging along basinal fracture zones controlled by the pre-Pan-African rifting stage. A paragenesis similar to that of the Lusaka prospects has been proposed to be a vector towards massive sulphide ores in several parts of the world; therefore, it is possible that these small willemite showings in Zambia may be part of a much bigger, and still unexplored, zinc province.

Vanadium mineralization in ore of the Vihanti massive sulfide base-metal deposit, Finland

A series of vanadium oxides—shcherbinaite, karelianite, kyzylkumite, coulsonite, and berdesinskiite—was found in association with pyrrhotite in pyrite-pyrrhotite ore from the Paleoproterozoic Vihanti massive sulfide deposit of the Kuroko-type. It is suggested that enrichment in vanadium of massive sulfide ore from the Vihanti deposit is a result of their metamorphogenic regeneration and pyrrhotinization at the expense of rocks and ore enriched in vanadium. The list of rare minerals in massive sulfide ore has been extended.

Rb-Sr direct dating of pyrite from the Pipela VMS Zn-Cu prospect, Rajasthan, NW India

In unaltered volcanogenic massive sulfide (VMS) ore deposits, variable Rb/Sr ratios in the ore mineral permits application of the Rb-Sr isotopic method to directly date the time of ore formation. In contrast, post-crystallization deformation and metamorphism would open the system to metamorphic fluids that would alter elemental ratios. To test whether the Rb-Sr isotopic systematics in the ore minerals had preserved the formation time in the ∼800 Ma metamorphosed VMS ores within the ∼1 Ga Ambaji-Sendra arc terrain, Rajasthan, NW India, common sulfides, pyrite and sphalerite from the Pipela Cu-Zn prospect, were analyzed for their geochemistry and Rb-Sr isotopic systematics. Trace and rare earth elements in these minerals are resident probably at crystal defects, whereas all inclusions (including those from metamorphic fluids) were removed by a simple crush leach method. Results of direct dating by the Rb-Sr method to the hydrothermal pyrite yielded an isochron age of 1025±76 Ma with an initial Sr ratio of 0.7051±0.0006, similar to previously determined zircon U-Pb age of 987 Ma from associated rhyolites. This suggests the applicability of the crush leach method to date formation time of metamorphosed pyrite ores.

Probabilistic analysis of open stope stability using numerical modelling

A probabilistic approach is presented for the analysis of open stope stability. The approach considers the inherent variability and uncertainty which are typical of rock mass properties. In this study, a series of numerical analyses were performed using FLAC to study the stability of open stopes while taking into account the variability in the rock mass properties. The rock mass was divided into six strength classes: three classes for the host rock and three classes for the massive sulphide ore. Each class was randomly distributed to the elements in the FLAC model. The host rock-to-massive sulphide ore ratio is envisaged to have a strong influence on the stope. To verify this, three cases of different ore percentages were considered and the results compared. The results, which were presented as Probability Density Functions (PDFs), indicate that the zones of low stiffness show high range of displacements and that the increase in the percentage of the ore significantly affects the stability of the stopes.

CARBONIC FLUID OVERPRINTS IN VOLCANOGENIC MASSIVE SULFIDE DEPOSITS: EXAMPLES FROM THE KELAN VOLCANOSEDIMENTARY BASIN, ALTAIDES, CHINA

The Tiemurte and the Dadonggou Zn-Pb-(Cu) volcanogenic massive sulfide (VMS) deposits, situated in the Devonian Kelan volcanosedmentary basin of the south margin of the Chinese Altaides, were metamorphosed and overprinted by metamorphic sulfide-quartz veins during Early Carboniferous to Early Permian. Two mineralizing periods of ore mineral growth can be identified: (1) disseminated, banded, and massive sulfide ores related to a primary depositional sea-floor volcanic-hydrothermal activity; and (2) the foliated sulfide-quartz veins (Q1) related to synorogenic metamorphism and late chalcopyrite-bearing quartz veins (Q2) cutting the schist related to a younger metamorphic overprinting event. Carbonic (CO 2 -CH 4 -N 2 ) fluid inclusions are ubiquitous in Q1 and Q2 veins. A few carbonic fluid inclusions may be primary and some may be pseudosecondary, whereas the vast number of carbonic fluid inclusions are secondary, representing later events. A microthermometry study shows that primary carbonic fluid inclusions in Q1 and Q2 have Tm CO2 ranging from −64.5° to about −59.4°C with Th CO2 = −13.4° to about +18.6°C. The secondary carbonic fluid inclusions exhibit two behaviors when cooling and heating: the Tm CO2 of the first group (L CO2 ) ranges from −63.3° to −57.7°C, and that of the second group (L CO2-CH4-N2 ) ranges from −83.4° to −61°C. The second group of carbonic fluids has much higher CH 4 and/or N 2 proportions than the first group. The trapping temperatures for the carbonic inclusions have been estimated to be 243.1° to 412.1°C (for Tiemurte) and 216° to ~430°C (for Dadonggou) on the basis of some L CO2 -L H2O inclusions associated with carbonic inclusions, and the trapping pressures have been estimated to be 120 to ~340 MPa, which are consistent with deformation P-T conditions of quartz, and slightly less than the P-T conditions of the biotite and garnet metamorphic zones. These abundant carbonic inclusions at the Tiemurte and the Dadonggou deposits were not a part of a volcanogenic ore-producing system but represent a much younger event, possibly having originated from a synorogenic metamorphism which may have contributed to orogenic gold.

Lithogeochemistry as a tracer of the tectonic setting, lateral integrity and mineralization of a highly metamorphosed Mesoproterozoic volcanic arc sequence on the eastern margin of the Namaqua Province, South Africa

The Areachap Group represents the medium- to high-grade metamorphic and deformed remnants of a Mesoproterozoic (ca. 1.24–1.30 Ga) volcanic arc that was accreted onto the western margin of the Kaapvaal Craton during the early stages of the Namaqua-Natal Orogeny. Few regional geochemical studies of the succession have been undertaken and despite recent geochronological work from throughout the outcrop belt there is still uncertainty as to the lateral integrity and correlation of the succession from one area to another. This uncertainty has been aided by minimal outcrop and extensive deformation and dislocation of one area from another. This study uses trace element geochemistry combined with Sm–Nd-isotopic data from the northern and southern ends of the succession to test its lateral integrity. Minor differences, including the abundance of certain lithologies, varying influences of a crustal component and differences in age between different areas are apparent, but the succession, as a whole, displays lateral integrity as a continental island arc. All lithologies are characterised by enrichment in Th, U, Pb and the large ion lithophile elements relative to primitive mantle, along with Nb–Ta depletion relative to La, and strong light rare earth element (LREE) enrichment relative to heavy REE depletion, which, along with positive ε Nd(t) values of mafic gneisses from both ends of the succession, indicates mantle-derivation within a subduction-related environment with a substantial amount of crustal assimilation. Despite some minor geochemical and isotopic differences in the lithological architecture on a local scale the Areachap Group exhibits coherent geochemical characteristics along its entire strike length. Localised remobilization of elements, particularly in areas characterised by granulite grade metamorphism, as well as in the altered footwall zones of volcanogenic massive sulphide lenses, is present. These alteration trends, along with primary geochemical signatures are remarkably well preserved despite the high grade of metamorphism, as illustrated in clearly defined hydrothermal alteration trends on the alteration box plot, and serves as an efficient tool to delineate areas that have undergone hydrothermal alteration spatially associated with massive sulphide ore bodies. The systematic association of hydrothermal alteration and sulphide ore bodies provides support for the isochemical character of rock compositions during high-grade metamorphism and the lack of extensive post-metamorphic alteration processes.

Sulfur isotope characteristics of metamorphosed Zn–Cu volcanogenic massive sulfides in the Areachap Group, Northern Cape Province, South Africa

Zn- and Cu-rich massive sulfide ores of volcanogenic origin [volcanogenic massive sulfide (VMS) deposits] occur as stratiform/stratabound lenses of variable size hosted by gneisses, amphibolites, and schists of the Areachap Group, in the Northern Cape Province of South Africa. The Areachap Group represents the highly deformed and metamorphosed remnants of a Mesoproterozoic volcanic arc that was accreted onto the western margin of the Kaapvaal Craton during the ∼1.0–1.2 Ga Namaquan Orogeny. Sulfur isotope data (δ34S) are presented for 57 sulfide separates and one barite sample from five massive sulfide occurrences in the Areachap Group. Although sulfides from each site have distinct sulfur isotope values, all δ34S values fall within a very limited range (3.0‰ to 8.5‰). Barite has a δ34S value of 18.5‰, very different from that of associated sulfides. At one of the studied sites (Kantienpan), a distinct increase in δ34S of sulfides is observed from the massive sulfide lens into the disseminated sulfides associated with a distinct footwall alteration zone. Sulfide–sulfide and sulfide–barite mineral pairs which recrystallized together during amphibolite- and lower granulite facies metamorphism are not in isotopic equilibrium. Sulfur isotope characteristics of sulfides and sulfates of the Zn–Cu ores in the Areachap Group are, however, very similar to base metal sulfide accumulations associated with modern volcanic arcs and unsedimented mid-ocean ridges. It is thus concluded that profound recrystallization and textural reconstitution associated with high-grade regional metamorphism of the massive sulfide ores of the Areachap Group did not result in extensive sulfur isotopic homogenization. This is similar to observations in other metamorphosed VMS deposit districts and confirms that massive sulfide ores remain effectively a closed system for sulfur isotopes for both sulfides and sulfates during metamorphism.

Type of volcanoes hosting the massive sulfide deposits of the Iberian Pyrite Belt

The Volcanic Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB) in southern Portugal and Spain, comprises an Upper Devonian to Lower Carboniferous submarine succession with a variety of felsic volcanic lithofacies. The architecture of the felsic volcanic centres includes felsic lavas/domes, pyroclastic units, intrusions and minor mafic units that define lava–cryptodome–pumice cone volcanoes. The diversity of volcanic lithofacies recognized in different areas of the IPB mainly reflects variations in proximity to source, but also differences in the eruption style. The IPB volcanoes are intrabasinal, range in length from 2 km to > 8 km and their thickest sections vary from ∼ 400 m to > 800 m. These volcanoes are dominated by felsic lavas/domes that occur at several stratigraphic positions within the volcanic centre, however the pyroclastic units are also abundant and are spatially related to the lavas/domes. The intrusions are minor, and define cryptodomes and partly-extrusive cryptodomes. The hydrothermal systems that formed the Neves Corvo and Lousal massive sulfide ore deposits are associated with effusive units of felsic volcanic centres. At Neves Corvo, the massive sulfide orebodies are associated to rhyolitic lavas that overlie relatively thick fiamme-rich pyroclastic unit. In several other locations within the belt, pyroclastic units contain sulfide clasts that may have been derived from yet to be discovered coeval massive sulfide deposits at or below the sea floor, which enhances the exploration potential of these pyroclastic units and demonstrates the need for volcanic facies analysis in exploration.

The Gumeshevo skarn-porphyry copper deposits in the Central Urals, Russia: Evolution of the ore-magmatic system as deduced from isotope geochemistry (Sr, Nd, C, O, H)

The Early Devonian Gumeshevo deposit is one of the largest ore objects pertaining to the dioritic model of the porphyry copper system paragenetically related to the low-K quartz diorite island-arc complex. The (87Sr/86Sr)t and (ɛNd)t of quartz diorite calculated for t = 390 Ma are 0.7038–0.7045 and 5.0–5.1, respectively, testifying to a large contribution of the mantle component to the composition of this rock. The contents of typomorphic trace elements (ppm) are as follows: 30–48 REE sum, 5–10 Rb, 9–15 Y, and 1–2 Nb. The REE pattern is devoid of Eu anomaly. Endoskarn of low-temperature and highly oxidized amphibole-epidote-garnet facies is surrounded by the outer epidosite zone. Widespread retrograde metasomatism is expressed in replacement of exoskarn and marble with silicate (chlorite, talc, tremolite)-magnetite-quartz-carbonate mineral assemblage. The 87Sr/86Sr ratios of epidote in endoskarn and carbonate in retrograde metasomatic rocks (0.7054–0.7058 and 0.7053–0.7065, respectively) are intermediate between the Sr isotope ratios of quartz dioritic rocks and marble (87Sr/86Sr = 0.70784 ± 2). Isotopic parameters of the fluid equilibrated with silicates of skarn and retrograde metasomatic rocks replacing exoskarn at 400°C are δ18O = +7.4 to +8.5‰ and δD = −49 to −61‰ (relative to SMOW). The δ13C and δ18O of carbonates in retrograde metasomatic rocks after marble are −5.3 to +0.6 (relative to PDB) and +13.0 to +20.2% (relative to SMOW), respectively. Sulfidation completes metasomatism, nonuniformly superimposed on all metasomatic rocks and marbles with formation of orebodies, including massive sulfide ore. The δ34S of sulfides is 0 to 2‰ (relative to CDT);87Sr/86Sr of calcite from the late calcite-pyrite assemblage replacing marble is 0.704134 ± 6. The δ13C and 87Sr/86Sr of postore veined carbonates correlate positively (r = 0.98; n = 6). The regression line extends to the marble field. Its opposite end corresponds to magmatic (in terms of Bowman, 1998b) calcite with minimal δ13C, δ18O, and 87Sr/86Sr values (−6.9 ‰, +6.7‰, and 0.70378 ± 4, respectively). The aforementioned isotopic data show that magmatic fluid was supplied during all stages of mineral formation and interacted with marble and other rocks, changing its Sr, C, and O isotopic compositions. This confirms the earlier established redistribution of major elements and REE in the process of metasomatism. A contribution of meteoric and metamorphic water is often established in quartz from postore veins.

Reconstruction and interpretation of giant mafic dyke swarms: a case study of 1.78 Ga magmatism in the North China craton

Abstract Short-lived giant mafic dyke swarms are keys to the interpretation of continental evolution and tectonics, reconstruction of continental palaeogeographical regimes, and petrogenesis of volcanism. The 1.78 Ga Taihang–Lvliang dyke swarm, one of the most significant and best-preserved Precambrian swarms in the central part of the North China craton (NCC), is reviewed and discussed. It is interpreted to have a radiating geometry that is compatible with the Xiong'er triple-junction rift, in which the Xiong'er volcanic province is proposed to be the extrusive counterpart of this swarm. It resulted in significant extension, uplift and magmatic accretion of the NCC, and it is comparable with the Phanerozoic large igneous provinces (LIPs) in areal extent ( c. 0.3 Mkm 2 ) and estimated volume ( c. 0.3 Mkm 3 ), short lifespan (<20 Ma), and intraplate setting. This North China LIP is unique in that it comprises large volumes of both mafic and intermediate components. It could have resulted from extensive mantle–crust interaction, probably driven by a large-scale mantle upwelling. A plume tectonic model is favoured by several lines of supporting evidence (i.e. massive volcanic flows correlated over large areas and a giant fanning dyke swarm with plume-affinitive chemistry). It could responsible for massive sulphide (Pb–Zn) and gold (Au–Ag) ore deposits in the Xiong'er volcanic province. Dismembered remnants of this magmatism in other block(s), with potential candidates in South America, Australia and India, could identify other cratonic blocks that were formerly connected to the North China craton.

Society of Economic Geologists Silver Medal for 2008: Citation of Mark D. Hannington

Dear SEG friends and guests: Every now and then a university professor has the good fortune to work with an exceptional student. I am such a professor and the exceptional student in the mid- to late 1980s was Mark Hannington, this year’s SEG Silver Medalist. I somehow convinced Mark to come to Toronto for graduate studies (actually, I bribed him by offering submersible dives). Mark was a member of a small team I had put together to explore the deep sea floor for hydrothermal sulfide deposits as natural laboratories for better understanding volcanic-hosted massive sulfide (VMS) ores that formed on ancient sea beds and are now on land. I supervised Mark’s M.Sc. and Ph.D. theses but use the word “supervised” lightly because Mark was a self-starter. He knew what needed to be done, figured out how to do it, and got on with the task at hand. In addition, he was an unusually talented writer, a skill that would serve him well for what was to come in his career. While at Toronto, Mark collaborated with Peter Herzig. Peter, a cosponsor of Mark’s Silver Medal nomination, was one of my postdocs and is now the director of IFM-GEO-MAR, the large German oceanographic institute in Kiel. Putting Mark and Peter together was one of the best decisions of my academic life because they did exceptional research and have …

Pyrite deformation textures in the massive sulfide ore deposits of the Norwegian Caledonides

The Norwegian Caledonides represent a belt of late Precambrian to early Palaeozoic rocks, emplaced as a series of nappes onto the Fennoscandian basement. Massive sulfide orebodies occur along virtually the whole length of the orogenic belt making it possible to study deposits of a similar origin, chemistry and mineralogy but variably deformed at different metamorphic conditions. Samples from seven pyrite-rich ore deposits deformed at temperatures from ∼ 320 °C to ∼ 610 °C have been investigated using reflected light petrographic observation, orientation contrast (OC) imaging and electron backscatter diffraction (EBSD). While a range of brittle, annealment and growth textures are preserved in the deposits, all preserve evidence for lattice misorientation and low-angle (∼ 2°) sub-grain boundary development indicative of dislocation creep. These results are at odds with those implied from the published pyrite deformation mechanism map, which suggest that pyrite does not deform by plastic mechanisms at natural geological strain-rates and that the brittle–ductile transition is at ∼ 425 °C. Our results imply that pyrite is more ductile than generally inferred and the current deformation mechanism map needs to be revised with plastic deformation mechanisms operating at a much wider range of temperature and strain-rate conditions.

Combination of sequential chemical extraction and modelling of dam-break wave propagation to aid assessment of risk related to the possible collapse of a roasted sulphide tailings dam

The Sotiel–Coronada abandoned mining district (Iberian Pyrite Belt) produced complex massive sulphide ores which were processed by flotation to obtain Cu, Zn and Pb concentrates. The crude pyrite refuses were roasted for sulphuric acid production in a plant located close to the flotation site, and waste stored in a tailing dam. The present study was focused on the measurements of flow properties, chemical characterization and mineralogical determination of the roasted pyrite refuses with the aim of assessing the potential environmental impact in case of dam collapse. Chemical studies include the determination of the total contaminant content and information about their bio-availability or mobility using sequential extraction techniques. In the hypothetical case of the tailing dam breaking up and waste spilling (ca. 4.54 Mt), a high density mud flow would flood the Odiel river valley and reach both Estuary of Huelva (Biosphere Reserve by UNESCO, 1983) and Atlantic Ocean in matter of a couple of days, as it was predicted by numerical simulations of dam-break waves propagation through the river valley based on quasi-2D Saint-Venant equations. The total amount of mobile pollutants that would be released into the surrounding environment is approximately of 7.1·10 4 t of S, 1.6·10 4 t of Fe, 1.4·10 4 t of As, 1.2·10 4 t of Zn, 1.0·10 4 t of Pb, 7.4·10 3 t of Mn, 2.2·10 3 t of Cu, 1.5·10 2 t of Co, 36 t of Cd and 17 t of Ni. Around 90–100% of S, Zn, Co and Ni, 60–70% of Mn and Cd, 30–40% of Fe and Cu, and 5% of As and Pb of the mobile fraction would be easily in the most labile fraction (water-soluble pollutants), and therefore, the most dangerous and bio-available for the environment. This gives an idea of the extreme potential risk of roasted pyrite ashes to the environment, until now little-described in the scientific literature.

Geology and Mineralization of the Shimokawa Mine : An Allochthonous Ridge-type Massive Sulfide Ore Deposit

Geology and Mineralization of the Shimokawa Mine : An Allochthonous Ridge-type Massive Sulfide Ore Deposit