辽宁红透山块状硫化物矿床矿石糜棱岩铜-金富集机制

辽宁红透山太古宙块状硫化物型铜锌矿床成矿后的变质作用达到高角闪岩相 ,并经历了 3个阶段的变形。矿床的主要矿石矿物为黄铁矿、磁黄铁矿、黄铜矿和闪锌矿。主矿体内分布有 30多条矿石糜棱岩带 ,它们大多数平行或近于平行块状硫化物矿层 ,少数产在矿体附近围岩中。带中的各种硫化物矿物均遭受了强烈的剪切变形 ,其中黄铁矿以碎裂为主 ,而磁黄铁矿、黄铜矿和闪锌矿显示强烈的塑性。矿石糜棱岩比块状硫化物矿石明显富集铜、金、银等元素 ,其铜、金和银平均含量分别达1 1 .0 0 % ,1 .74g/t和 2 35g/t,相对于块状矿石的富集系数分别为 5 .3、5 .0和 4 .6。这些金属的高度富集主要是因为矿石糜棱岩受到了后期流体的叠加。铅同位素组成表明矿石糜棱岩中的金属一部分来自块状矿石 ,另一部分来自块状硫化物矿体之外。韧性剪切和流体叠加均发生于矿床退变质过程中     

Mineralogy and textures of the Lahanos and Kızılkaya massive sulphide deposits,northeastern Turkey,and their similarity to Kuroko ores

A distinct vertical zonation very similar to that described for the Kuroko deposits of Japan, is displayed by both mineralogy and textures of sulphides from the Lahanos and Kzlkaya massive sulphide deposits of northeastern Turkey. A deeper erosional level is exposed at the Kzlkaya deposit, so that only remnants of the massive sulphide ore zone are present. The zonation is from an upper zone of massive Cu and Zn sulphides (black and yellow ore) with fine-grained, colloform, banded, framboidal, and spherulitic textures, downwards through an intermediate zone of low Cu-Zn massive pyrite with transitional textures, to a lower zone of stockwork and impregnated pyrite displaying euhedral, zoned textures. The fine-grained and colloform pyrite of the upper zones is progressively overgrown by, and recrystallized to, the massive and euhedral pyrite of lower zones. The original textures of these deposits are best preserved by pyrite. The previous interpretation of these textures, of sulphide deposition from colloidal solutions ponded by an impermeable pyroclastic horizon, is reexamined in the light of present observations. Although ultra-fine-grained sulphides, framboids, and radially-cracked spherules could have formed by replacement of pre-existing minerals by a colloidal solution, the colloform and banded textures are indicative of growth in open spaces. It thus seems likely that the fine-grained colloform sulphides, including chalcopyrite, sphalerite, and tennantite as well as pyrite, were initially deposited on or near the surface of the sea-floor. Additional evidence for this interpretation is seen in the progressive recrystallization of the sulphide textures to massive, much coarser, pyrite in the lower zones. This recrystallization may in part be due to diagenetic and hydrothermal processes operating after formation of the original layered sulphides. These conclusions are in agreement with those reached for the similar, but larger Madenköy deposit 100 km to the east.     

Coal geology and coal quality of the Miocene Mugla basin, southwestern Anatolia, Turkey

This work focuses on the relationship between the coal geology and coal quality of the Miocene Mugla basin, Southwestern Anatolia, Turkey. To this end, detailed petrographical, mineralogical and geochemical studies were performed on composite profile samples from the nine coal fields in the Mugla basin (Alatepe, Bagyaka, Bayir, Çakiralan, Ekizköy, Eskihisar, Hüsamlar, Sekköy and Tinaz coal fields). The Mugla lignite is a high ash (from 16 to 56%) and sulphur (from 2.1 to 5.7%) lignite which is petrographically characterised by a high huminite content, mainly gelinite macerals. The mineral matter of the studied lignite samples is made up mainly of clay minerals and quartz, with the exception of the Sekköy and Ekizköy lignites, in which calcite is the dominant mineral phase with minor amounts of quartz, clay minerals, pyrite and gypsum and traces of aragonite. Syngenetic opal is also frequently identified in these samples. The differentiation of these two types of lignite with specific mineralogical patterns is attributed to the contemporaneous development of peatlands with a high detrital input, dominated by the quartz and clay mineral setting, and peatlands with low detrital supply and a dominant carbonate-rich lacustrine environment. The higher water table of the latter allowed the precipitation of micritic carbonates and the development of lakes with abundant mollusc fauna. This differentiation is also evidenced by the geochemical data. Thus, the Sekköy, Ekizköy, Hüsamlar, Bayir and Alatepe lignites are characterised by relatively low Al and Fe contents (<1.4%) and high sulphur contents (4.2 to 5.7%). In addition Sekköy and Ekizköy show relatively high contents of Ca (6.3–7.1% compared to 1.6–3.8% in the other lignites). All the lignite samples studied are characterised by relatively high Mo and U contents when compared with the worldwide averages of trace elements in coal. Relatively high alkaline syngenetic conditions of the peat-forming environment of the Mugla coal are deduced from the following mineralogical, petrographical and geochemical evidence: (a) the precipitation of syngenetic opal (dissolution of quartz and re-precipitation as opal) and calcite; (b) minor and very early syngenetic sulphide precipitation (only framboidal and euhedral pyrite); (c) high bacterial activity, typical of high pH conditions, inferred from low preservation of tissue structures; (d) preservation of aragonite gastropod shells; and (e) the anomalous enrichment of U, Mo and W. A key result of the study of Mugla limnic coals (at least of the Sekköy and Ekizköy coal fields) is that a major influence was exerted on the early diagenetic evolution of the coal by the hydrochemistry of the lacustrine waters. This hydrochemistry was largely linked to the lithology of the surrounding source rock areas although the final evolutionary trend of the solute composition in the lake waters, characterized by very high carbonate and sulphate contents, was largely enhanced by the endorheic river drainage system and the arid–semiarid paleoclimatic situation under which organic matter accumulation took place.     

The Rammelsberg massive sulphide Cu-Zn-Pb-Ba-Deposit, Germany: an example of sediment-hosted, massive sulphide mineralisation

The Rammelsberg polymetallic massive sulphide deposit was the basis of mining activity for nearly 1000 y before finally closing in 1988. The deposit is hosted by Middle Devonian pelitic sediments in the Rhenohercynian terrane of the Variscan Orogen. The deposit consists of two main orebodies that have been intensely deformed. Deformation obscures the original depositional relationships, but the regional setting as well as the geochemistry and mineralogy of the mineralisation display many characteristics of the SHMS (sediment-hosted massive sulphide) class of ore deposits. Rammelsberg is briefly compared to the other massive sulphide deposits in the European Variscan, including Meggen and those deposits in the Iberian Pyrite Belt. Received: 28 September 1998 / Accepted: 5 January 1999     

河南水洞岭铜锌矿床特征、成因及找矿潜力分析

水洞岭铜锌矿床矿体赋存在石英角斑凝灰岩中,呈似层状、透镜状产出,与地层产状一致,矿石具块状、浸染和条带状构造,中细粒结构,主要矿石矿物为黄铁矿、黄铜矿、闪锌矿和方铅矿等。地质和地球化学证据表明,水洞岭铜锌矿床为海相火山沉积块状硫化物矿床。通过找矿潜力分析在矿区及外围困出了四个找矿靶区：黄土岭、老胡家、张圪塔和砂固堆。     

Synchronous deposition of massive sulphide deposits in the Iberian Pyrite Belt: New data from Las Herrerías and La Torerera ore-bodies

Two small to medium sized massive sulphide deposits, Las Herrerías and La Torerera, located in the Iberian Pyrite Belt (IPB) are examined from a geological and palynostratigraphic perspective. The palynological assemblages are assignable to the Retispora lepidophyta–Verrucosisporites nitidus (LN) miospore Biozone (Latest Devonian: Latest Famennian/Strunian) of Western Europe. This age permits correlation with some of the main massive sulphide deposits dated so far in the region (viz., Tharsis, Aznalcóllar, Sotiel-Coronada or Neves-Corvo), and validates once again the hypothesis that a single mineralizing event was responsible for the genesis of most of the IPB’s massive sulphide deposits. The present study confirms that palynostratigraphy is an invaluable high-resolution biostratigraphic tool in the IPB, applicable to dating, correlation and ore-exploration.     

Mercury and mercury compounds in surface air, soil gas, soils and rocks

Secondary mercury dispersion haloes were detected and defined above sulphide mineralization by in-situ mercury in soil gas measurements. The meteorological factors controlling the concentration of mercury in soil gas were investigated by long-term experiments. Different mercury compounds in soils and rocks have been determined by a thermal destruction technique. In areas with sulphide mineralization, adsorbed mercury, HgCl₂, HgS, HgSO₄ and organically fixed mercury are the most important mercury compounds. The concentrations, transport and secondary formation of mercury and its compounds is controlled by: (1) the content of organic matter, Fe-oxides/hydroxides and clay minerals of the soils; and (2) the composition of the underlying rocks.The occurrence of mercury-sulphur compounds indicates the topographic influence on down-slope dispersion and the direction of inclination of the ore body. HgS and HgSO₄ are the dominant mercury compounds in the ore; in the bedrock, mercury occurs mainly as adsorbed mercury.     

On the origin of the livingstonite deposits at Huitzuco,Guerrero, Mexico

Livingstonite is the principal ore mineral in the deposits of the Huitzuco District in the State of Guerrero, Mexico. The ore is found in the lower part of the Morelos Formation, which consists of a thick bed of sedimentary anhydrite containing lenses of dolomite and dolomite breccia. In the unweathered ore practically all the mercury is in the livingstonite, whereas the antimony occurs partly in the livingstonite and partly in stibnite. Native sulfur forms pockets as much as 30 centimeters in diameter in the ore and is also found in gypsum on the surface away from the ore.It appears that the deposition of livingstonite, rather than of the combination of cinnabar and stibnite that is more usual in other districts, was caused by the native sulfur present in considerable quantity scattered through the sedimentary dolomite and anhydrite above, below, and in the ore. Since the formula of livingstonite is actually HgSb₄S₈ (not HgSb₄S₇ as was previously supposed), it is not stable in solutions containing only HgS, Sb₂S₃, Na₂S, and H₂O. It has been proved by one of us, experimentally, that in order to form livingstonite, the solutions must contain elemental sulfur in addition to HgS, Sb₂S₃, Na₂S, and H₂O. In such solutions the solubility of mercuric sulfide is extremely low. However, the problem of transport is overcome if the elemental sulfur is already present in the wall rock. In that case, the reaction of the elemental sulfur with a solution containing mercuric sulfide and antimony sulfide, but not saturated with either, would precipitate livingstonite, as was proved by our experimental work.     

Detection of concealed Cu–Zn massive sulfide mineralization below eolian sand and a calcrete cover in the eastern part of the Namaqua Metamorphic Province, South Africa

The regolith studied here is located at the defunct Areachap mine and the newly discovered Kantienpan Cu–Zn volcanic-hosted massive sulfide (VHMS) deposit, located in the Areachap Group of the eastern part of Mesoproterozoic Namaqua Metamorphic Province. This area is highly prospective for further VHMS discoveries. Paleo and recent weathering of the upper most parts of massive sulfide deposits led to the formation of a gossan zone. Due to semi-arid climatic conditions during the late Cretaceous, affecting the African Land surface, the lowermost units of the Kalahari Group and the underlying floor rocks were calcretized. An approximately 6 m thick calcrete layer formed above the gossan zone and this was later covered by eolian Kalahari sand. Samples were collected from the eolian sand cover in the study areas to determine the best analytical method that would enable recognition of the concealed ore deposits and detect the widest secondary dispersion halo.Mobile metal ions from the finest fraction of the eolian sand samples (< 75 μm) were extracted with a NH₄EDTA (EDTA) solution. The solution was analysed for Cu, Zn, Pb and Mn by inductively coupled plasma mass spectrometry (ICP-MS). The same grainsize fraction of the original samples was also analysed for comparison purposes by means of X-ray fluorescence (XRF).Results indicate that the ore zone in both areas may be recognized by both partial and total analyses of the eolian sand samples collected, although the calcrete layer, below the sand cover, acts as a partial geochemical barrier. The recognition of the ore zone depends on the regolith forming processes and the thickness of the eolian sand cover. In the Areachap area, with a relatively thick sand cover (in excess of 1 m) above the calcrete layer, the detectable geochemical halo is related to the distribution of the mobile metal ions, and partial extraction (EDTA solution) results define a larger dispersion halo than that, that could be detected by total analysis (XRF). Whereas, in the Kantienpan area with a very thin sand cover (< 50 cm) dispersion appears to be related more to the secondary redistribution of gossaniferous clasts released by recent weathering out of the calcrete, than to dispersion of mobile metal ions on the surface of sand particles. In this area, the XRF results reveal a wider dispersion of the elements of interest.     

分量化探方法稳定性、异常重现性及有效性研究--以相山铀矿田为例

在相山铀矿田开展了分量化探方法稳定性、异常重现性及有效性研究。结果表明,分量分析方法稳定性较高,同一样品多次测试结果之间的符合度及不同时间(批次)测试结果的一致性均较好。石里坑地区的重复性测量结果显示,两次测量的分量铀平均含量相近、地球化学波动特征相似、局部分布形态和部分高值区的强度有所差异,但高值区和低值区的展布形态、空间位置吻合较好,说明分量化探的异常重现性较好。云际工作区的分量化探测量结果表明,分量铀高值区(带)与已知矿体的空间对应关系较佳,可有效地指示深部隐伏铀矿体,反映了分量化探在相山盆地铀矿勘查中的有效性及适用性。     

Identification and origin of bitumen in Neolithic artefacts from Demirköy Höyük (8100 BC): Comparison with oil seeps and crude oils from southeastern Turkey

Two ring-like artefacts from the aceramic Neolithic site of Demirköy Höyük in southeastern Turkey were analysed using geochemical techniques in order to determine whether they were prepared using a bitumen amalgam or not. The artefacts, dated 8100 BC, are early evidence of the innovative use of a petroleum-based material to prepare pieces of ornaments (beads, rings, etc.) for the elite of a Neolithic settlement. In order to trace the source of the presumed bitumen, two oil seeps, Boğazköy and Yeşilli, were sampled. To complete the genetic references, geochemical data on crude oils from the main oil fields from the area were compiled.Basic geochemical data show that bitumen is present in the artefacts. Sterane and terpane patterns, as well as carbon isotopic data on C₁₅₊ saturated and C₁₅₊ aromatic hydrocarbons, allowed us to conclude that the Demirköy Höyük bitumen and the Boğazköy oil seep were generated from a Silurian source rock. The detailed geochemical characteristics show, however, that the Demirköy Höyük bitumen does not correlate perfectly with the Boğazköy oil. This discrepancy suggests several explanations: the real bitumen source may be elsewhere in the vicinity and has not been discovered or was at the Boğazköy oil seep location but with slightly different properties in Neolithic times, or has disappeared. Another possibility is that the slight molecular differences are due to weathering effects, which affected the pristine bitumen within the archaeological sample.     

The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part I: geology

The Kristineberg volcanic-hosted massive sulphide (VMS) deposit, located in the westernmost part of the Palaeoproterozoic Skellefte district, northern Sweden, has yielded 22.4 Mt of ore, grading 1.0% Cu, 3.64% Zn, 0.24% Pb, 1.24 g/t Au, 36 g/t Ag and 25.9% S, since the mine opened in 1941, and is the largest past and present VMS mine in the district. The deposit is hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the Skellefte Group, which forms the lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits. The Kristineberg deposit is situated lower in the Skellefte Group than most other deposits. It comprises three main ore zones: (1) massive sulphide lenses of the A-ore (historically the main ore), having a strike length of about 1,400 m, and extending from surface to about 1,200 m depth, (2) massive sulphide lenses of the B-ore, situated 100–150 m structurally above the A-ore, and extending from surface to about 1,000 m depth, (3) the recently discovered Einarsson zone, which occurs in the vicinity of the B-ore at about 1,000 m depth, and consists mainly of Au–Cu-rich veins and heavily disseminated sulphides, together with massive sulphide lenses. On a regional scale the Kristineberg deposit is flanked by two major felsic rock units: massive rhyolite A to the south and the mine porphyry to the north. The three main ore zones lie within a schistose, deformed and metamorphosed package of hydrothermally altered, dominantly felsic volcanic rocks, which contain varying proportions of quartz, muscovite, chlorite, phlogopite, pyrite, cordierite and andalusite. The strongest alteration occurs within 5–10 m of the ore lenses. Stratigraphic younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration, and tectonic folding and shearing. In the vicinity of the ore lenses, hydrothermal alteration has produced both Mg-rich assemblages (Mg-chlorite, cordierite, phlogopite and locally talc) and quartz–muscovite–andalusite assemblages. Both types of assemblages commonly contain disseminated pyrite. The sequence of volcanic and ore-forming events at Kristineberg is poorly constrained, as the ages of the massive rhyolite and mine porphyry are unknown, and younging indicators are absent apart from local metal zoning in the A-ores. Regional structural trends, however, suggest that the sequence youngs to the south. The A- and B-ores are interpreted to have formed as synvolcanic sulphide sheets that were originally separated by some 100–150 m of volcanic rocks. The Einarsson zone, which is developed close to the 1,000 m level, is interpreted to have resulted in part from folding and dislocation of the B-ore sulphide sheet, and in part from remobilisation of sulphides into small Zn-rich massive sulphide lenses and late Au–Cu-rich veins. However, the abundance of strongly altered, andalusite-bearing rocks in the Einarsson zone, coupled with the occurrence of Au–Cu-rich disseminated sulphides in these rocks, suggests that some of the mineralisation was synvolcanic and formed from strongly acidic hydrothermal fluids. Editorial handling: P. Weihed     

Comparison of total and partial extractable copper in anomalous and background peat samples

Nitric-perchloride acid, 0.5 M hydrochloric acid, 0.05 M EDTA and neutral ammonium acetate were investigated as extractants for copper in peat samples. Greatest contrast between anomalous and background samples was found with nitric-perchloric acid (‘total’) digestion. EDTA or dilute hydrochloric acid liberated 13–100% of the total copper whereas ammonium acetate removed a maximum of 8%.     

A magnetite-rich Cyprus-type VMS deposit in Ortaklar: A unique VMS style in the Tethyan metallogenic belt,Gaziantep, Turkey

The Ortaklar VMS deposit is hosted in the Koçali Complex consisting of basalts and deep sea pelagic sediments, which formed by rifting and continental break-up of the southern Neotethyan in Late Triassic. The basalts are of NMORB-type without notable crustal contamination. From the surface to depth, the Ortaklar deposit consists of a gossan zone, a thick massive ore zone and a poorly developed stockwork zone. Primary mineralisation is characterised by distinctive facies including sulphide breccias (proximal), graded beds (distal), stockworks and chimney fragments. Ore mineral abundances decrease in the order of pyrite, magnetite, chalcopyrite, and sphalerite. Two distinct phases of mineralisation, massive magnetite and massive sulphide, are present in the Ortaklar deposit. Textural evidence (e.g., magnetite replacing sulphides) and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages. The transition from sulphide to magnetite mineralisation is interpreted to relate to variation in H₂S content of ore fluids. The 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in Fe and H₂S. The 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in Fe but poor in H₂S, replacing the pre-existing sulphide ore.The alteration patterns, mineral paragenesis, lithological features (massive ore-stockwork ore-gossan) of the Ortaklar deposit together with its trace elements, Cu-Pb-Zn-Au-Ag and REE signatures are all consistent with a Cyprus-type VMS system. The δ³⁴S values in pyrite and chalcopyrite samples range from 2.6 to 5.7‰, indicating that the hydrothermal fluids were associated with sub-seafloor igneous activity, typical of Cyprus-type VMS deposits. However, magnetite formed later than sulphide minerals in the Ortaklar deposit, contrasting with typical Cyprus-type VMS deposits where magnetite generally occurs in lower sections. Consequently, although the Ortaklar deposit generally conforms to Cyprus-type deposits, it is distinguished from them by its late stage and high magnetite concentration. Thus, the Ortaklar deposit is thought to be an exceptional and perhaps unique Cyprus-type VMS deposit.     

A sulfur isotope study of volcanogenic massive sulfide deposits of the Eastern Black Sea province,Turkey

Kuroko-type massive sulfide deposits of the Eastern Black Sea province of Turkey are related to the Upper Cretaceous felsic lavas and pyroclastic rocks, and associated with clay and carbonate alteration zones in the footwall and hangingwall lithologies. A complete upward-vertical section of a typical orebody consists of a stringer-disseminated sulfide zone composed mainly of pyrite and chalcopyrite; a massive pyrite zone; a massive yellow ore consisting mainly of chalcopyrite and pyrite; a black ore made up mainly of galena and sphalerite with minor amounts of chalcopyrite, bornite, pyrite and various sulfosalts; and a barite zone. Most of the deposits in the province are associated with gypsum in the footwall or hangingwall. The paragenetic sequence in the massive ore is pyrite, sphalerite, chalcopyrite, bornite, galena and various sulfosalts, with some overlap between the mineral phases. Massive, stringer and disseminated sulfides from eight kuroko-type VMS deposits of the Eastern Black Sea province have a ³⁴S range of 0–7 per mil, consistent with the ³⁴S range of felsic igneous rocks. Sulfides in the massive ore at Madenköy (4.3–6.1 per mil) differ isotopically from sulfides in the stringer zone (6.3–7.2 per mil) suggesting a slightly increased input of H₂S derived from marine sulfate with time. Barite and coarse-grained gypsum have a ³⁴S range of 17.7–21.5 per mil, a few per mil higher than the ³⁴S value of contemporaneous seawater sulfate. The deposits may, therefore, have formed in restricted basins in which bacterial reduction of sulfate was taking place. Fine-grained, disseminated gypsum at Kutlular and Tunca has ³⁴S values (2.6–6.1 per mil) overlapping those of ore sulfides, indicating sulfide oxidation during waning stages of hydrothermal activity.     

Mineralogical Associations of Arsenic and Antimony in Thirty Five Geochemical Reference Materials by Sequential Extraction with Hydride Generation and Atomic Absorption Spectrometry

A method is described to estimate the chemical forms of arsenic (As) and antimony (Sb) in a variety of geochemical reference materials, combining a sequential extraction scheme with hydride generation and atomic absorption spectrometry (HG-AAS). The fractions dissolved by sequential extraction are empirically defined as the exchangeable, EDTA soluble, oxide, sulfide and residual fractions. The amount of As and Sb in the EDTA soluble fraction have been derived mainly from oxide phases, and partly from carbonate minerals. Most sulfide minerals in common geological samples were considered to be dissolved with the digestion of 0.7 mol l⁻¹ NaOCl, but only small fraction of arsenopyrite and loellingite in ores could be dissolved in this way. Satisfactory agreement was observed between the sum of the As or Sb values from exchangeable to residual fractions and the reported total As or Sb values, with a few exceptions. Analytical results of As and Sb for thirty five geochemical reference materials are tabulated, and geochemical and mineralogical features are discussed.     

A Genetic Model for Ore Magma of the Chibaisong Copper-Nickel Sulphide Deposit, Jilin

In the early 1980's, the author proposed his view that copper-nickel sulphide deposts are of ore magma origin. For more than ten years, this view has aroused attention of his colleagues at home and abroad. In this paper an attempt is made to deal with the genetic model for ore magma of copper-nickel sulphide deposits in more details on the basis of geological, geochemical, petrophysico - chemical and thermodynamic studies of the Chibaisong copper-nickel sulphide deposit in the Changbai Mountains, Jilin province.     

Bismuth and cobalt minerals as indicators of stringer zones to massive sulphide deposits, Iberian Pyrite Belt

The stringer zones and commonly the interaction zone at the base of the massive sulphide mounds in the Iberian Pyrite Belt contain bismuth and cobalt minerals that are not found in the overlying massive sulphides. These are fairly rare cobalt sulphoarsenides (cobaltite, alloclasite, galucodot) that were formed at the beginning of the massive sulphide genesis, and fairly common bismuth sulphides (bismuthinite, hammarite, wittichenite, cosalite, kobellite, joseite, etc.), including species rare at world scale (nuffieldite, giessenite, jaskolskiite) that were deposited from last stage high-temperature (> 300 °C) copper-bearing fluids containing Bi (Te, Se). The last stage fluids precipitated chalcopyrite containing Cu, Bi, Te, (Se) sulphosalts at the base of the sulphide mound to form a high cupriferous zone. Their interaction with the massive sulphides is reflected by the formation of an exchange zone, a few metres thick, showing chalcopyrite disease textures, at the base of the mound; this zone forms the upper limit of potentially economic copper enrichment and of bismuth minerals. Gold is undoubtedly in part, if not totally, related to this last phase. The bismuth concentrations being equivalent in the massive sulphides and the stringers, the presence of bismuth minerals in the stringer zones results from high-temperature conditions combined with a rarity of galena, which impedes absorption of available Bi. The distribution of these bismuth minerals provides a basic mineralogical zoning in the stringer zone, with a deep, low-aS₂ zone containing native bismuth and tellurides and a shallow, higher-aS₂ zone in contact with the massive ore sensu stricto and containing complex bismuth sulphides. These results make it possible to distinguish between sulphide veinlets belonging to stockwork zones of massive orebodies and veinlets of an ambiguous nature, and provide mineralogical criteria for the proximity of copper-rich zones. They enrich the very complex mineralogy of the Iberian Pyrite Belt.     

Chemical evidence for,and implications of,a primary FeS phase in the Ankarvattnet Zn-Cu-Pb massive sulphide deposit,central Swedish Caledonides

The origin of the pyrrhotite in the Ankarvattnet massive sulphide deposit is discussed, based on chemical relations between the different mineralization types. A metamorphic genesis is rejected and a premetamorphic origin is alternatively suggested, which is in agreement with similar ideas for the origin of the pyrrhotite in other deposits. The pyrrhotite is thought to have formed in the stringer zone to a massive pyritic layer with similar formation mechanisms as for volcanogenic massive sulphide deposits. The recognition of a stringer zone mineralogy provides better possibilities to understand the physico-chemical character of the ore forming environment.     

Intraplate mafic magmatism,degasification, and deposition of mercury: The giant Almadén mercury deposit (Spain) revisited

The giant Almadén mercury deposit (Spain) is hosted by the Lower Silurian Criadero Quartzite; in turn this ore-bearing rock unit is cross-cut by the so-called Frailesca unit, a diatreme body of basaltic composition. The geochemical characteristics of the Silurian to Devonian Almadén District volcanic units indicate that these rocks originated from an enriched, evolving mantle source that ultimately yielded basanites–nephelinites to rhyolites, through olivine-basalts, pyroxene-basalts, trachybasalts, trachytes, very scarce rhyolites, and quartz-diabases. The Silurian intraplate alkaline volcanism developed in submarine conditions which triggered widespread hydrothermal activity resulting in Hg ore formation and pervasive alteration to carbonates. The δ¹⁸O, δ¹³C, and δ³⁴S isotopic signatures for carbonates and pyrite suggest different sources for carbon and sulfur, including magmatic and organic for the former and magmatic and sea water for the latter. The most important and efficient natural source of mercury on Earth is by far the volcanic activity, which liberates mercury via quiescent degassing and catastrophic (Plinian) events when eruptions can overwhelm the atmospheric budget of Hg. Thus, we suggest that CO₂ degasification and coeval distillation of mercury from the volcanic rocks fed the huge hydrothermal system that led to massive deposition of mercury at Almadén. Build up of Hg⁰_gas in magmatic chambers during waning rifting in the Late Ordovician, followed by renewed volcanism in the Early Silurian, would have resulted in massive degasification of the accumulated mercury. Part of this mercury went into the Criadero Quartzite leading to formation of the huge Almadén deposit and others (e.g., El Entredicho) along the same stratigraphic level. Progressive depletion of the deep seated magmatic Hg stock would have resulted in a drastic reduction in ore deposit size after the Lower Silurian when smaller deposits formed (e.g., Las Cuevas).