The geology and geochemistry of the Lumwana Cu (± Co ± U) deposits, NW Zambia

The Lumwana Cu (± Co ± U) deposits of NW Zambia are large, tabular, disseminated ore bodies, hosted within the Mwombezhi Dome of the Lufilian Arc. The host rocks to the Lumwana deposits are two mineralogically similar but texturally distinct gneisses, a granitic to pegmatitic gneiss and a banded to augen gneiss which both comprise quartz–feldspar ± biotite ± muscovite ± haematite ± amphibole and intervening quartz–feldspar ± biotite schist. The sulphide ore horizons are typically developed within a biotite–muscovite–quartz–kyanite schist, although mineralization locally occurs within internal gneiss units. Contacts between the ore and host rocks are transitional and characterized by a loss of feldspar. Kinematic indicators, such as S-C fabrics and pressure shadows on porphyroblasts, suggest a top to the north shear sense. The sulphides are deformed by a strong shear fabric, enclosed within kyanite or concentrated into low strain zones and pressure shadows around kyanite porphyroblasts. This suggests that the copper mineralization was introduced either syn- or pre-peak metamorphism. In addition to Cu and Co, the ores are also characterized by enrichments in U, V, Ni, Ba and S and small, discrete zones of uranium mineralization, occur adjacent to the hanging wall and footwall of the copper ore bodies or in the immediate footwall to the copper mineralization. Unlike typical Copperbelt mineralization, unmineralized units show very low background copper values. Whole rock geochemical analyses of the interlayered schist and ore schist, compared to the gneiss, show depletions in Ca, Na and Sr and enrichments in Mg and K, consistent with replacement of feldspar by biotite. The mineral chemistry of muscovite, biotite and chlorite reflect changes in the bulk rock chemistry and show consistent increases in X _Mg as the schists develop. δ³⁴S for copper sulphides range from +2.3?‰ to +18.5?‰, with pyrite typically restricted to values between +3.9?‰ and +6.2?‰. These values are atypical of sulphides precipitated by bacteriogenic sulphate reduction. δ³⁴S data for Chimiwungo (Cu + Co) show a broader range and increased δ³⁴S values compared to the Malundwe (Cu) mineralization. The Lumwana deposits show many characteristics which distinguish them from classical Copperbelt mineralization and which suggests that they are formed by metasomatic alteration, mineralization and shearing of pre-Katangan basement. Although this style of mineralization is reported elsewhere in the Copperbelt, sometimes associated with the more widely reported stratiform ores of the Lower Roan, none of the previously reported occurrences have so far developed the tonnages of ore reported at Lumwana.     

Mineralogy and geochemistry of sediments from Simbock Lake,Yaoundé area (southern Cameroon): provenance and environmental implications

Two cores of sediments, named NR and EB, were collected in the Simbock Lake (Mefou watershed, Yaoundé) to assess their provenance and the degree of heavy metal pollution based on mineralogical and geochemical data. The sediments are sandy, sand-clayey to clayey, and yellowish brown to greenish brown, and with high amounts of organic matter (average value of TOC is 1.95%). The sediments are mainly composed of quartz, kaolinite, accessory goethite, smectite, rutile, feldspars, illite, gibbsite, and interstratified illite-vermiculite. Fourier transform infrared (FT-IR) spectroscopy shows that kaolinite is less crystallized in the NR core than in the EB core. The Index of Compositional Variability (ICV), Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), and the Rb/Sr and K₂O/Rb ratios indicate a high weathering intensity in the source area. These sediments have low contents in Al₂O₃, Fe₂O₃, Na₂O, K₂O, MgO, and CaO as well as high values in SiO₂, P₂O₅, TiO₂, and MnO relative to the upper continental crust. The concentrations of Cr, V, Ba, and Zr are higher in the NR core than those in EB. The total rare earth element (REE) content varies between 78 and 405 ppm. The light REE are abundant (LREE/HREE ~?18–59; avg.?=?25.61). The chondrite-normalized REE patterns exhibit (i) negative Eu anomaly (Eu/Eu^* ~?0.38–0.62; avg.?=?0.5), (ii) slight positive Ce anomaly (Ce/Ce^* ~?1.11–1.34; avg.?=?1.11), and (iii) high REE fractionation ((La/Yb)_N ~?12.3–51.75; avg.?=?25.61). The enrichment factor (EF) shows that the Mefou watershed through the Simbock Lake sediments is slightly polluted by the agricultural and urban activities.     

Petrography and geochemistry of the Shilu Fe–Co–Cu ore district,South China: Implications for the origin of a Neoproterozoic BIF system

The Shilu Fe–Co–Cu ore district is situated in the western Hainan Province of south China. This district consists of the upper Fe-rich layers and the lower Co–Cu ores, which are mainly hosted within the Neoproterozoic Shilu Group, a dominantly submarine siliciclastic and carbonate sedimentary succession that generally has been metamorphosed to greenschist facies. Three facies of metamorphosed BIFs, the oxide, the silicate–oxide and the sulfide–carbonate–silicate, have been identified within the Shilu Group. The oxide banded iron formation (BIF) facies (quartz itabirites or Fe-rich ores) consists of alternating hematite-rich and quartz-rich microbands. The silicate–oxide BIF facies (amphibolitic itabirites or Fe-poor ores) comprises alternating millimeter to tens of meter scale, magnetite–hematite-rich bands with calc-silicate-rich macro- to microbands. The sulfide–carbonate–silicate BIF facies (Co–Cu ores) contain alternating cobaltiferous pyrite, cobaltiferous pyrrhotite and chalcopyrite macrobands to microbands mainly with dolomite–calcite, but also with minor sericite–quartz bands. Blasto-oolitic, pelletoidal, colloidal, psammitic, and cryptocrystalline to microcrystalline textures, and blasto-bedding structures, which likely represent primary sedimentation, are often observed in the Shilu BIF facies.The Shilu BIFs and interbedded host rocks are generally characterized by relatively low but variable ∑ REE concentrations, LREE depletion and/or MREE enrichment relative to HREE, and no Ce, Gd and Eu anomalies to strongly positive Ce, Gd and Eu anomalies in the upward-convex PAAS-normalized REY patterns, except for both the banded or impure dolostones with nil Ce anomaly to negative Ce anomalies and negative La anomalies, and the minor sulfide–carbonate–silicate BIF facies with moderately negative Eu anomalies. They also contain relatively low but variable HFSE abundances as Zr, Nb, Hf, Th and Ti, and relatively high but variable abundances of Cu, Co, Ni, Pb, As, Mn and Ba. The consistently negative ε_Nd(t) values range from − 4.8 to − 8.5, with a T_DM age of ca. 2.0 Ga. In line with the covariations between Al₂O₃ and TiO₂, Fe₂O₃ + FeO and SiO₂, Mn and Fe, Zr and Y/Ho and REE, and Sc and LREE, the geochemical and Sm–Nd isotopic features suggest that the precursors to the Shilu BIFs formed from a source dominated by seafloor-derived, high- to low temperature, acidic and reducing hydrothermal fluids but with variable input of detrital components in a seawater environment. Moreover, the involved detrital materials were sourced dominantly from an unknown, Paleoproterozoic or older crust, with lesser involvement from the Paleo- to Mesoproterozoic Baoban Group underlying the Shilu Group.The Shilu BIFs of various facies are interpreted to have formed in a shallow marine, restricted or sheltered basin near the rifted continental margin most likely associated with the break-up of Rodinia as the result of mantle superplume activity in South China. The seafloor-derived, periodically upwelling metalliferous hydrothermal plume/vent fluids under anoxic but sulfidic to anoxic but Fe^2 +-rich conditions were removed from the plume/vent and accumulated in the basin, and then variably mixed with terrigenous detrital components, which finally led to rhythmic deposition of the Shilu BIFs.     

Mineralogy, geochemistry and stratigraphy of the Maslovsky Pt–Cu–Ni sulfide deposit, Noril’sk Region, Russia

We report new data on the stratigraphy, mineralogy and geochemistry of the rocks and ores of the Maslovsky Pt–Cu–Ni sulfide deposit which is thought to be the southwestern extension of the Noril’sk 1 intrusion. Variations in the Ta/Nb ratio of the gabbro-dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses, which gave rise to the Northern and Southern Maslovsky intrusions that together host the Maslovsky deposit. The Northern intrusion is located inside the Tungusska sandstones and basalt of the Ivakinsky Formation. The Southern intrusion cuts through all of the lower units of the Siberian Trap tuff-lavas, including the Lower Nadezhdinsky Formation; demonstrating that the ore-bearing intrusions of the Noril’sk Complex post-date that unit. Rocks in both intrusions have low TiO₂ and elevated MgO contents (average mean TiO₂ <1 and MgO?=?12?wt.%) that are more primitive than the lavas of the Upper Formations of the Siberian Traps which suggests that the ore-bearing intrusions result from a separate magmatic event. Unusually high concentrations of both HREE (Dy+Yb+Er+Lu) and Y (up to 1.2 and 2.1?ppm, respectively) occur in olivines (Fo_79.5 and 0.25% NiO) from picritic and taxitic gabbro-dolerites with disseminated sulfide mineralization. Thus accumulation of HREE, Y and Ni in the melts is correlated with the mineral potential of the intrusions. The TiO₂ concentration in pyroxene has a strong negative correlation with the Mg# of both host mineral and Mg# of host rock. Sulfides from the Northern Maslovsky intrusion are predominantly chalcopyrite–pyrrhotite–pentlandite with subordinate and minor amounts of cubanite, bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals (Au, Ag and Pd), Sn–Pd–Pt–Bi–Pb compounds and Fe–Pt alloys. Sulfides from the Southern Maslovsky intrusion have δ ³⁴S?=?5–6‰ up to 10.8‰ in two samples whereas the country rock basalt have δ ³⁴S?=?3–4‰, implying there was no in situ assimilation of surrounding rocks by magmas.     

Magnetite geochemistry of the Longqiao and Tieshan Fe–(Cu) deposits in the Middle-Lower Yangtze River Belt: Implications for deposit type and ore genesis

Magnetite is a common mineral in many ore deposits and their host rocks, and contains a wide range of trace elements (e.g., Ti, V, Mg, Cr, Mn, Ca, Al, Ni, Ga, Sn) that can be used for deposit type fingerprinting. In this study, we present new magnetite geochemical data for the Longqiao Fe deposit (Luzong ore district) and Tieshan Fe–(Cu) deposit (Edong ore district), which are important magmatic-hydrothermal deposits in eastern China.Textural features, mineral assemblages and paragenesis of the Longqiao and Tieshan ore samples have suggested the presence of two main mineralization periods (sedimentary and hydrothermal) at Longqiao, among which the hydrothermal period comprises four stages (skarn, magnetite, sulfide and carbonate); whilst the Tieshan Fe–(Cu) deposit comprises four mineralization stages (skarn, magnetite, quartz-sulfide and carbonate).Magnetite from the Longqiao and Tieshan deposits has different geochemistry, and can be clearly discriminated by the Sn vs. Ga, Ni vs. Cr, Ga vs. Al, Ni vs. Al, V vs. Ti, and Al vs. Mg diagrams. Such difference may be applied to distinguish other typical skarn (Tieshan) and multi-origin hydrothermal (Longqiao) deposits in the MLYRB. The fluid–rock interactions, influence of the co-crystallizing minerals and other physicochemical parameters, such as temperature and fO₂, may have altogether controlled the magnetite trace element contents of both deposits. The Tieshan deposit may have had higher degree of fO₂, but lower fluid–rock interactions and ore-forming temperature than the Longqiao deposit. The TiO₂–Al₂O₃–(MgO + MnO) and (Ca + Al + Mn) vs. (Ti + V) magnetite discrimination diagrams show that the Longqiao Fe deposit has both sedimentary and hydrothermal features, whereas the Tieshan Fe–(Cu) deposit is skarn-type and was likely formed via hydrothermal metasomatism, consistent with the ore characteristics observed.     

Magmatic evolution of the Tuwu–Yandong porphyry Cu belt,NW China: Constraints from geochronology,geochemistry and Sr–Nd–Hf isotopes

The Tuwu–Yandong porphyry Cu belt is located in the Eastern Tianshan mountains in the eastern Central Asian Orogenic Belt. Petrochemical and geochronological data for intrusive and volcanic rocks from the Tuwu and Yandong deposits are combined with previous studies to provide constraints on their petrogenesis and tectonic affinity. New LA–ICP–MS zircon U–Pb ages of 348.3 ± 6.0 Ma, 339.3 ± 2.2 Ma, 323.6 ± 2.5 Ma and 324.1 ± 2.3 Ma have been attained from intrusive units associated with the deposits, including diorite, plagiogranite porphyry, quartz albite porphyry and quartz porphyry, respectively. The basalt and andesite, which host part of the Cu mineralization, are tholeiitic with high Al₂O₃, Cr, Ni and low TiO₂ contents, enriched LREEs and negative HFSE (Nb, Ta, Zr, Ti) anomalies consistent with arc magmas. Diorites are characterized by low SiO₂ content but high MgO, Cr and Ni contents, similar to those of high-Mg andesites. The parental magma of the basalt, andesite and diorite is interpreted to have been derived from partial melting of mantle-wedge peridotite that was previously metasomatized by slab melts. The ore-bearing plagiogranite porphyry is characterized by high Na₂O, Sr, Cr and Ni contents, low Y and Yb contents, low Na₂O/K₂O ratios and high Sr/Y ratios and high Mg#, suggesting an adakitic affinity. The high ε_Nd(t) (5.02–9.16), low I_Sr (0.703219–0.704281) and high ε_Hf(t) (8.55–12.99) of the plagiogranite porphyry suggest they were derived by a partial melting of the subducted oceanic crust followed by adakitic melt-mantle peridotite interaction. The quartz albite porphyry and quartz porphyry are characterized by similar Sr–Nd–Hf isotope but lower Mg# and whole-rock (La/Yb)_N ratios to the plagiogranite porphyry, suggesting they were derived from juvenile lower crust, and negative Eu anomalies suggest fractionation of plagioclase. We propose that a flat subduction that started ca. 340 Ma and resulted in formation of the adakitic plagiogranite porphyry after a period of “steady” subduction, and experienced slab rollback at around 323 Ma.     

Mineralogy and geochemistry of Al-phosphate and Al-borosilicate-bearing metaquartzites of the northern Serra do Espinhaço (State of Bahia, Brazil)

Summary The investigated Al-phosphate- and Al-borosilicate-bearing metaquartzite horizon belongs to the Middle Proterozoic Serra de Vereda member of the São Marcos Formation of the northern Espinhaço fold belt. Outcrops are located in the NNW–SSE trending hills of the Serra de Canas/Cana Brava (Northern Serra do Espinhaço, State of Bahia, NE Brazil) about 10km west of the town of Boquira. Sky blue lazulite and deep blue to lilac dumortierite are enriched in layers which sometimes show relic cross bedding. The occurrence of hematite patches and layers is typical. In rocks of type A, phosphorus contents range from 1.89wt.% to 10.73wt.% P₂O₅ and boron contents are mostly below 10ppm whereas in the rocks of type B phosphorus contents are below 1% and boron contents reach 2600ppm with a mean value of 1139ppm. REE distribution patterns of rocks are predominantly controlled by the amount of xenotime, monazite and zircon. Oxygen thermometry on quartz and hematite and the stability of kyanite, augelite, trolleite and berlinite allow to estimate the minimum metamorphic peak P-T conditions at 475°C and 3.8kbar i.e. within the stability field of scorzalite–lazulite and dumortierite. The association of Al-phosphates with hematite layers provides evidence for the deposition of the metaquartzite protolith in a seawater-fed sabkha-like sand flat fringing the Espinhaço rift. It is proposed that apatite, Al-phosphates and Al-borosilicates were chemically precipitated together with iron hydroxides from pore fluids. The antithetic behaviour of phosphorus and boron contents in the metaquartzites is the consequence of an influx of toxic boron-rich water that drastically affected algae populations and consequently reduced phosphorus precipitation.     

Vulnerability and resistance to neoliberal environmental changes: An assessment of agriculture and forestry in the Biobio region of Chile (1974–2014)

This article examines the dynamics of double exposure, vulnerability, and resistance to neoliberal globalization and environmental change in the Chilean agricultural region of Biobio. By using climatic models and secondary Agricultural Census data from 1997 and 2007, we assess how Chilean neoliberal reforms have, since 1974, facilitated land use changes and forestry investments. We demonstrate that policy changes which incentivize forestry investments have reduced cultivated agricultural lands and native forest, and concentrated land in the hands of global agribusiness corporations. Compounding these issues, Biobio shows a climatic trend towards aridity coupled with an increasing demand for irrigation. Analyzing these conditions, we argue that the neoliberal globalization of regional agriculture under the context of climatic changes has produced a regional space of increasing vulnerabilities and uneven geographical development in Biobio. We particularly demonstrate that the Chilean mode of agricultural neoliberalization has been conducive to land dispossession—to the detriment of traditional agriculture —and has homogenized the biophysical landscape, replacing traditional crops and native forests with exotic species like pines and eucalyptus. We also examine how local producers are using resistance movements to cope with and contest neoliberal environmental changes. We conclude by evaluating the implications of these spaces of agricultural vulnerabilities and local resistances in the context of uneven geographical development at a regional and global scale.     

Geochronology and geochemistry of Late Cretaceous igneous intrusions and Mo–Cu–(W) mineralization in the southern Yidun Arc,SW China: Implications for metallogenesis and geodynamic setting

The Sanjiang Tethyan Metallogenic Domain (STMD) is an important part of the Tethyan giant metallogenic belt. The Yidun Arc is a part of the STMD in the eastern Tibetan Plateau. Recently, four newly discovered Mo–Cu–(W) ore deposits related to granitic intrusions were found distributed along the north-south strike in the southern Yidun Arc, which are identified as the Xiuwacu, Relin, Hongshan, and Tongchanggou deposits herein. These four deposits formed along high-angle north-northwest or north-west strike-slip faults, with vein-type and porphyry-type Mo–Cu mineralization developed in the intrusions. Molybdenite Re–Os and zircon U–Pb dating together with zircon Hf isotopes and whole-rock geochemistry of the intrusions were studied to discern the relationship between mineralization and magmatism, metallogenesis, and tectonic settings. Molybdenite from skarn-type mineralization at the Hongshan deposit has a Re–Os isochron age of 81.2 ± 2.6 Ma (MSWD = 1.3, n = 5) consistent with previously published zircon U–Pb ages and Re–Os ages of porphyry-type Mo mineralization. These results indicate that the Hongshan is a Late Cretaceous porphyry-skarn Cu–Mo deposit. Zircon U–Pb ages of the granitic intrusions in the Xiuwacu, Relin, and Tongchanggou deposits varying from ~ 87.4 Ma to ~ 82.7 Ma. Combined with published molybdenite Re–Os age spectrum (~ 85 Ma to ~ 81.2 Ma), it is proposed that the Mo–Cu–(W) mineralization in the Shangri-La region is spatially, temporally, and probably genetically related to the Late Cretaceous granitic intrusions. The Relin, Hongshan, and Tongchanggou intrusions have high SiO₂ (65.2–70.0 wt.%), Sr (363–905 ppm), Sr/Y (22–72), and La/Yb (37–69) ratios, and low Y (11.6–17.0 ppm) and Yb (0.97–1.59 ppm), which displayed adakitic affinities. Their low MgO (0.66–1.44 wt.%), Mg# (25–46), variable negative zircon ε_Hf(t) values (− 7.9 to − 2.3), and Proterozoic two-stages Hf model ages (T_DM2 = 1.13–1.62 Ga) suggest that they were probably dominantly derived from partial melting of thickened lower continental crust. According to the tectonic evolution of the Bangong Meso-Tethys Ocean during the Late Mesozoic, the Late Cretaceous igneous event and mineralization in the Yidun Arc likely formed under a late- or post-collision extensional environment, probably related to the collision between the Lhasa and Qiangtang terranes during the Late Cretaceous.     

Geochronology and geochemistry of the Cambrian (~518 Ma) Chagantaolegai ophiolite in northern West Junggar (NW China): constraints on spatiotemporal characteristics of the Chingiz–Tarbagatai megazone

The Chingiz–Tarbagatai megazone is a well-known early Palaeozoic unit in eastern Kazakhstan that extends into northern West Junggar along the Tarbagatai–Xiemisitai–Sharbuti Mountains. Here, we report new geochronological and geochemical data for the Chagantaolegai ophiolite, discovered in the south Xiemisitai Mountains, north of the Heshituoluogai Valley in West Junggar. The laser ablation inductively coupled plasma mass spectrometry zircon U–Pb ages of a gabbro in the Chagantaolegai ophiolite are 517 ± 3 and 519 ± 3 Ma, corresponding to the early to middle Cambrian. Serpentinized peridotites in the ophiolite show low rare earth element (REE) abundances (0.61–0.94 μg/g) and slight loss of middle REEs. Chagantaolegai metagabbro samples have flat to very slightly depleted patterns in light REEs, with a narrow range of REE abundances. The Chagantaolegai spilites and metagabbros display similar flat patterns, which show a geochemical signature similar to mid-ocean ridge basalt (MORB) between Yb and Zr, and diverge from MORB towards the most incompatible elements in MORB-normalized multi-element diagrams. The Th/Yb vs. Nb/Yb diagram for the spilite samples also suggests a mid-ocean ridge (MOR) setting. To summarize, all the geochemical characteristics of the Chagantaolegai ophiolite point to MOR ophiolite. The positive ε_Nd(t) values (0.78 to +9.85) suggest that the gabbros and spilites were derived from a depleted mantle source with chemical inhomogeneity. The Chagantaolegai ophiolite spatiotemporal characteristics correlate well with the Kujibai and Hongguleleng ophiolites in the northern part of West Junggar, and the Zhaur and Balkybek ophiolites in eastern Kazakhstan. These data show that early Palaeozoic oceanic crust started to develop in the early to middle Cambrian in northern West Junggar. Stratigraphic correlations also suggest that the South Saur Fault and an inferred fault buried in the Heshituoluogai depression are the northern and southern boundary of the Chingiz–Tarbagatai megazone, respectively.     

Geochemistry of the Kalatongke Ni–Cu–(PGE) sulfide deposit,NW China: implications for the formation of magmatic sulfide mineralization in a postcollisional environment

The Kalatongke (also spelt as Karatungk) Ni–Cu–(platinum-group element, PGE) sulfide deposit, containing 33 Mt sulfide ore with a grade of 0.8 wt.% Ni and 1.3 wt.% Cu, is located in the Eastern Junggar terrane, Northern Xinjiang, NW China. The largest sulfide ore body, which occupies more than 50 vol.% of the intrusion Y1, is dominantly comprised of disseminated sulfide with a massive sulfide inner zone. Economic disseminated sulfides also occur at the base of the intrusions Y2 and Y3. The main host rock types are norite in the lower part and diorite in the upper part of each intrusion. Enrichment in large ion lithophile elements and depletion in heavy rare earth elements relative to mid-ocean ridge basalt indicate that the mafic intrusions were produced from magmas derived from a metasomatized garnet lherzolite mantle. The average grades of the disseminated ores are 0.6 wt.% Ni and 1.1 wt.% Cu, whereas those of the massive ores are 2 wt.% Ni and 8 wt.% Cu. The PGE contents of the disseminated ores (14–69 ppb Pt and 78–162 ppb Pd) are lower than those of the massive ores (120–505 ppb Pt and 30–827 ppb Pd). However, on the basis of 100% sulfide, PGE contents of the massive sulfides are lower than those of the disseminated sulfides. Very high Cu/Pd ratios (>4.5 × 10⁴) indicate that the Kalatongke sulfides segregated from PGE-depleted magma produced by prior sulfide saturation and separation. A negative correlation between the Cu/Pd ratio and the Pd content in 100% sulfide indicates that the PGE content of the sulfide is controlled by both the PGE concentrations in the parental silicate magma and the ratio of the amount of silicate to sulfide magma. The negative correlations between Ir and Pd indicate that the massive sulfides experienced fractionation.     

Nature and practical implications of heterogeneities in the geochemistry of zinc-rich,alkaline mine waters in an underground F–Pb mine in the UK

Water pollution arising from base metal sulphide mines is problematic in many countries, yet the hydrogeology of the subsurface contaminant sources is rarely well-characterized. Drainage water pumped from an active F–Pb mine in northern England has unusual chemistry (alkaline with up to 40 mg.l⁻¹ Zn) which profoundly impacts the ecology of the receiving watercourse. Detailed in-mine surveys of the quantity and quality of all ground water inflows to the mine were made. These revealed major, temporally persistent heterogeneities in ground water quality, with three broad types of water identified as being associated with distinct hydrostratigraphic units. Type I waters (associated with the Firestone Sill aquifer) are cool (<10°C), Ca–HCO₃–SO₄ waters, moderately mineralized (specific electrical conductance (SEC)≤410 μS.cm⁻¹) with <4 mg.l⁻¹ Zn. Type II waters (associated with the Great Limestone aquifer) are warmer (≈15°C), of Ca–SO₄ facies, highly mineralized (SEC≤1500 μS.cm⁻¹) with ≤40 mg.l⁻¹ Zn. Type III waters (in the deepest workings) are tepid (>18°C), of Ca–HCO₃–SO₄ facies, intermediately mineralized (SEC≤900 μS.cm⁻¹) with ≤13 mg.l⁻¹ Zn, and with significant Fe (≤12 mg.l⁻¹) and Pb (≤8 mg/l). Monotonic increases in temperature and Cl⁻ concentration with depth contrast with peaks in total mineralization, SO₄ and Zn at medium depth (in Type II waters). Sulphate, Pb and Zn are apparently sourced via oxidation of galena and sphalerite, which would release each metal in stoichiometric equality with SO₄. However, molal SO₄ concentrations typically exceed those of Pb and Zn by 2–3 orders of magnitude, which mineral equilibria suggest is due to precipitation of carbonate “sinks” for these metals. Contaminant loading budgets demonstrate that, although Type II waters amount to only 25% of the total ground water inflow to the mine, they account for almost 60% of the total Zn loading. This observation has important management implications for both the operational and post-abandonment phases of the mine life cycle.     

Anhydrite pseudomorphs and the origin of stratiform Cu–Co ores in the Katangan Copperbelt (Democratic Republic of Congo)

The stratiform Cu–Co ore mineralisation in the Katangan Copperbelt consists of dispersed sulphides and sulphides in nodules and lenses, which are often pseudomorphs after evaporites. Two types of pseudomorphs can be distinguished in the nodules and lenses. In type 1 examples, dolomite precipitated first and was subsequently replaced by Cu–Co sulphides and authigenic quartz, whereas in type 2 examples, authigenic quartz and Cu–Co sulphides precipitated prior to dolomite and are coarse-grained. The sulphur isotopic composition of the copper–cobalt sulphides in the type 1 pseudomorphs is between −10.3 and 3.1‰ relative to the Vienna Canyon Diablo Troilite, indicating that the sulphide component was derived from bacterial sulphate reduction (BSR). The generation of during this process caused the precipitation and replacement of anhydrite by dolomite. A second product of BSR is the generation of H₂S, resulting in the precipitation of Cu–Co sulphides from the mineralising fluids. Initial sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core. Precipitation of authigenic quartz was most likely induced by a pH decrease during sulphide precipitation. Fluid inclusion data from quartz indicate the presence of a high-salinity (8–18 eq. wt.% NaCl) fluid, possibly derived from evaporated seawater which migrated through the deep subsurface. ⁸⁷Sr/⁸⁶Sr ratios of dolomite in type 1 nodules range between 0.71012 and 0.73576, significantly more radiogenic than the strontium isotopic composition of Neoproterozoic marine carbonates (⁸⁷Sr/⁸⁶Sr = 0.7056–0.7087). This suggests intense interaction with siliciclastic sedimentary rocks and/or the granitic basement. The low carbon isotopic composition of the dolomite in the pseudomorphs (−7.02 and −9.93‰ relative to the Vienna Pee Dee Belemnite, V-PDB) compared to the host rock dolomite (−4.90 and +1.31‰ V-PDB) resulted from the oxidation of organic matter during BSR.     

Zircon U–Pb geochronology and geochemistry of the post-collisional volcanic rocks in eastern Xinjiang Province,NW China: implications for the tectonic evolution of the Junggar terrane

We report zircon U–Pb geochronologic and geochemical data for the post-collisional volcanic rocks from the Batamayineishan (BS) Formation in the Shuangjingzi area, northwestern China. The zircon U–Pb ages of seven volcanic samples from the BS Formation show that the magmatic activity in the study area occurred during 342–304 Ma in the Carboniferous. The ages also indicate that the Palaeo-Karamaili Ocean had already closed by 342 Ma. Moreover, the volcanic rocks also contained 10 inherited zircons with ages ranging from 565 to 2626 Ma, indicating that Precambrian continental crust or microcontinents with accretionary arcs are two possible interpretations for the basement underlying the East Junggar terrane. The sampled mafic-intermediate rocks belong to the medium-K to high-K calc-alkaline and shoshonitic series, and the formation of these rocks involved fractional crystallization with little crustal contamination. These Carboniferous mafic-intermediate rocks show depletions in Nb and Ta and enrichments in large ion lithophile elements (e.g. Rb, Ba, U, and Th) and light rare earth elements. The low initial ⁸⁷Sr/⁸⁶Sr values (0.7034–0.7042) and positive ε_Nd(t) values (+2.63 to +6.46) of these rocks suggest that they formed from depleted mantle material. The mafic-intermediate rocks were most likely generated by 5–10% partial melting of a mantle source composed primarily of spinel lherzolite with minor garnet lherzolite that had been metasomatized by slab-derived fluids and minor slab melts. In contrast, the felsic rocks in the BS Formation are A-type rhyolites with positive ε_Nd(t) values and young model ages. These rocks are interpreted to be derived from the partial melting of juvenile basaltic lower crustal material. Taken together, the mafic-intermediate rocks formed in a post-collisional extensional setting generated by slap breakoff in the early Carboniferous (342–330 Ma) and the A-type rhyolites formed in a post-collisional extensional setting triggered by the upwelling asthenosphere in the late Carboniferous (330–304 Ma).     

An integrated methodology for salt damage assessment and remediation: the case of San Jerónimo Monastery (Granada, Spain)

San Jerónimo Monastery (Granada, Spain) was selected as a case study for the investigation of the effect of indoor environmental conditions on salt weathering and for on-site testing of a remediation treatment using crystallization inhibitors on account of the extreme salt damage affecting both the building stone, a biomicritic limestone, calcarenite and wall paintings. A methodology combining several analysis techniques, phenomenological observations, salt and moisture analysis, environmental monitoring and thermodynamic simulations, was adopted in order to study the salt damage problems affecting this building. Within the collected samples, the majority of salts were found to be magnesium sulphate in the form of either hexahydrite or epsomite, depending on the climate conditions, together with minor amounts of gypsum, nitrates and chlorides. Comparison of empirical observations with thermodynamic simulations of the salt mixture behaviour clearly showed that salt-induced damage events take place during the seasonal changes from spring to summer and winter to spring. An aqueous solution of an organic phosphonate, which in laboratory experiments was found to be an effective inhibitor of magnesium sulphate crystallization, was sprayed over a selected test area of unpainted stonework at the site. Preliminary results seem to indicate that after the application of the treatment both the amount of efflorescence and ongoing damage to the stone support is reduced. However, long-term monitoring of the future condition of the test area is needed to confirm whether indeed this treatment is appropriate and effective in reducing salt damage at this case study site. The outcome of this study extends beyond the particular problems at San Jerónimo Monastery, as it demonstrates a methodological approach for the study and evaluation of salt weathering problems affecting cultural heritage.     

Environmental assessment of the arsenic-rich,Rodalquilar gold–(copper–lead–zinc) mining district,SE Spain: data from soils and vegetation

The Rodalquilar mineral deposits (SE Spain) were formed in Miocene time in relation to caldera volcanic episodes and dome emplacement phenomena. Two types of ore deposits are recognized: (1) the El Cinto epithermal, Au–As high sulphidation vein and breccia type; and (2) peripheral low sulphidation epithermal Pb–Zn–Cu–(Au) veins. The first metallurgical plants for gold extraction were set up in the 1920s and used amalgamation. Cyanide leaching began in the 1930s and the operations lasted until the mid 1960s. The latter left a huge pile of ~900,000–1,250,000 m³ of abandoned As-rich tailings adjacent to the town of Rodalquilar. A frustrated initiative to reactivate the El Cinto mines took place in the late 1980s and left a heap leaching pile of ~120,000 m³. Adverse mineralogical and structural conditions favoured metal and metalloid dispersion from the ore bodies into soils and sediments, whereas mining and metallurgical operations considerably aggravated contamination. We present geochemical data for soils, tailings and wild plant species. Compared to world and local baselines, both the tailings and soils of Rodalquilar are highly enriched in As (mean concentrations of 950 and 180 μg g⁻¹, respectively). Regarding plants, only the concentrations of As, Bi and Sb in Asparagus horridus, Launaea arborescens, Salsola genistoides, and Stipa tenacissima are above the local baselines. Bioaccumulation factors in these species are generally lower in the tailings, which may be related to an exclusion strategy for metal tolerance. The statistical analysis of geochemical data from soils and plants allows recognition of two well-differentiated clusters of elements (As–Bi–Sb–Se–Sn–Te and Cd–Cu–Hg–Pb–Zn), which ultimately reflect the strong chemical influence of both El Cinto and peripheral deposits mineral assemblages.     

Mineralogy and geochemistry of claystones from the Guadalupian–Lopingian boundary at Penglaitan,South China: Insights into the pre-Lopingian geological events

The Guadalupian–Lopingian (G/L) boundary, at a stratigraphically well-documented outcrop in Penglaitan, Guangxi Autonomous Region, South China, has been approved as the Global Stratotype Section and Point (GSSP). Several volcanic ashes or tuffs occur at this boundary, but their mineralogy and geochemistry are not available yet and no reliable age for this boundary has been obtained. A combined study of mineralogy, geochemistry and geochronology has been carried out in this study on six layers of claystones collected below (Group 1) and above (Group 2) the G/L boundary at the Penglaitan section. Both Group 1 and Group 2 claystones are likely clastic in origin, rather than volcanic ashes as previously thought. Thus the Penglaitan claystones are not suitable for age determination of the G/L boundary. They are significantly different in terms of mineralogy and geochemistry. Specifically, Group 1 claystones are likely derived from a mafic source which is genetically related to the Emeishan large igneous province, therefore providing additional evidence for the synchroneity between the G/L boundary mass extinction and the Emeishan volcanism. Group 2 samples were derived from a felsic source, of which zircons yield an age spectrum peaked at 262 ± 3 Ma, undistinguishable within the uncertainty from the currently accepted G/L boundary age (260.4 ± 0.4 Ma). Nevertheless, Group 2 samples are not related to Emeishan volcanism, because their negative zircon ε_Hf(t) values differ significantly from those of Emeishan magmas and trace element compositions of zircons are indicative of an arc source, rather than a within-plate source. In consideration of paleogeographic reconstruction, we propose that the Group 2 claystones may have been derived from continental arcs during the palaeo-Tethys evolution. This is the first sedimentary evidence for Permian continental arc in the northern margin of palaeo-Tethys.     

Biogeochemistry of Pb–Zn gossans,northwest Queensland,Australia: Implications for mineral exploration and mine site rehabilitation

The concentration and distribution of metals were studied in metallophytes, growing on and in the vicinity of Pb–Zn gossans, NW Queensland. The study investigated the accumulation of metals in plant species and assessed their potential use as indicators in geobotanical and biogeochemical prospecting and as metal excluders in mine site rehabilitation. Plant species colonising the gossans tolerate high concentrations of metals. Total mean metal concentrations of soils ranged from minima of 14 ppm Cu, 28 ppm Pb and 34 ppm Zn in background areas to maxima of 660 ppm Cu, 12000 ppm Pb and 2100 ppm Zn over mineralised soils. Over the gossans, the grass species Eriachne mucronata forma, Enneapogon lindleyanus and Paraneurachne muelleri replace the characteristic grass Triodia molesta where the soils have high Pb and Zn concentrations. Of the 16 plant species identified, 3 of them, Hybanthus aurantiacus, Clerodendrum tomentosum and Bulbostylis barbata, were confined to the gossan sites. B. barbata appears to be of particular use in geobotanical prospecting as it indicates base metal mineralisation in the region.     

Mineralogy and geochemistry of fine-grained Dahab stream sediments,Southeastern Sinai,Egypt: emphasis on the intergrowths of Fe–Ti oxides

Acta Geochimica - Mineralogical and geochemical characteristics of stream sediments collected from 30 stations in the Dahab-Wadi Kid area (southeastern Sinai, Egypt) are presented. The studied...