Low Arsenic Content Research Articles

Middle Bronze Age Arsenical Copper Alloys in Southern Portugal

In the Iberian Peninsula, the copper metallurgy from the Chalcolithic to the Middle Bronze Age (MBA) was mostly characterized by low arsenic contents. A collection of 53 MBA artefacts from southern Portugal was analysed by micro-EDXRF, optical microscopy, SEM–EDS and Vickers to investigate the metal composition and manufacture. No technological distinction was found between artefacts from domestic and funerary contexts, which were radiocarbon-dated to 2000–1500 cal bc. The arsenic contents of almost 100 MBA artefacts from this region, including the above-mentioned set, have a Gaussian distribution with a high average (3.9 wt% As). Possible explanations are discussed for this distinctive metallurgy at the south-western end of the Iberian Peninsula.

Importance of low substrate arsenic content in mushroom cultivation and safety of final food product

Mushrooms are known to accumulate various concentrations of different arsenic (As) species depending on the metalloid residue level in the substrate. These species are of different toxicity to humans and may represent a significant health problem. In the present study, edible fungal species (Agaricus bisporus, Pleurotus ostreatus, Pleurotus eryngii and Hericium erinaceus) grown separately on substrate containing different As species (As(III), As(V) and dimethylarsinic acid—DMA; each form individually) at different concentrations (0.1–0.8 mM) exhibited different accumulation of total As, the lowest being in A. b isporus (1.97 ± 0.14 mg kg−1 DW) and the highest in P. o streatus HK35 (68.8 ± 19.0 mg kg−1 DW) and P. e ryngii (68.0 ± 31.0 mg kg−1 DW). The highest biomass was observed for A. b isporus, regardless of the As forms and their concentration (from 341.24 ± 13.16 to 378.49 ± 14.57 g). This confirms that A. b isporus is highly resistant to As due to low metalloid uptake and accumulation. To ensure quality of cultivated mushroom species and safety of final food product to human health, there is a necessity to control the level of substrate contamination with As.

Source of arsenic-bearing pyrite in southwestern Vermont, USA: Sulfur isotope evidence

Arsenic-bearing pyrite is the source of arsenic in groundwater produced in late Cambrian and Ordovician gray and black slates and phyllites in the Taconic region of southwestern Vermont, USA. The aim of this study is to analyze the sulfur isotopic composition of this pyrite and determine if a relationship exists between pyrite δ34S and arsenic content. Pyrite occurs in both sedimentary/diagenetic (bedding-parallel layers and framboids) and low-grade metamorphic (porphyroblast) forms, and contains up to >2000ppm As. The sulfur isotopic composition of arsenic-bearing pyrite ranges from −5.2‰ to 63‰. In the marine environment, the sulfur in sedimentary pyrite becomes increasingly enriched in 34S as the geochemical environment becomes increasingly anoxic. There is a positive correlation between δ34S and arsenic content in the Taconic pyrite, suggesting that uptake of arsenic by pyrite increased as the environment became more reducing. This increased anoxia may have been due to a rise in sea level and/or tectonic activity during the late Cambrian and Ordovician. Low-grade metamorphism appears to have little effect on sulfur isotope composition, but does correlate with lower arsenic content in pyrite. New groundwater wells drilled in this region should therefore avoid gray and black slates and phyllites that contain sedimentary/diagenetic pyrite with heavy δ34S values.

Arsenic K-edge X-ray absorption near-edge spectroscopy to determine oxidation states of arsenic of a coastal aquifer–aquitard system

Determination of oxidation states of solid-phase arsenic in bulk sediments is a valuable step in the evaluation of its bioavailability and environmental fate in deposits, but is difficult when the sediments have low arsenic contents and heterogeneous distribution of arsenic species. As K-edge X-ray absorption near-edge spectroscopy (XANES) was used to determine quantitatively the oxidation states of arsenic in sediments collected from different depths of boreholes in the Pearl River Delta, China, where the highest aquatic arsenic concentration is 161.4 μg/L, but the highest solid arsenic content only 39.6 mg/kg. The results demonstrated that XANES is efficient in determining arsenic oxidation states of the sediments with low arsenic contents and multiple arsenic species. The study on the high-resolution vertical variations of arsenic oxidation states also indicated that these states are influenced strongly by groundwater activities. With the help of geochemical data, solid arsenic speciation, toxicity and availability were further discussed.

Arsenic in marine sediments from French Mediterranean ports: Geochemical partitioning, bioavailability and ecotoxicology

This work investigates arsenic mobility, bioavailability and toxicity in marine port sediments using chemical sequential extraction and laboratory toxicity tests. Sediment samples were collected from two different Mediterranean ports, one highly polluted with arsenic and other inorganic and organic pollutants (Estaque port (EST)), and the other one, less polluted, with a low arsenic content (Saint Mandrier port (SM)). Arsenic distribution in the solid phase was studied using a sequential extraction procedure specifically developed for appraising arsenic mobility in sediments. Toxicity assessment was performed on sediment elutriates, solid phases and aqueous arsenic species as single substance using the embryo-toxicity test on oyster larvae (Crassostrea gigas) and the Microtox test with Vibrio fischeri. Toxicity results showed that all sediment samples presented acute and sub-chronic toxic effects on oyster larvae and bacteria, respectively. The Microtox solid phase test allow to discriminate As-contaminated samples from the less contaminated ones, suggesting that toxicity of whole sediment samples is related to arsenic content. Toxicity of dissolved arsenic species as single substance showed that Vibrio fischeri and oyster larvae are most sensitive to As(V) than As(III). The distribution coefficient (Kd) of arsenic in sediment samples was estimated using results obtained in chemical sequential extractions. The Kd value is greater in SM (450Lkg−1) than in EST (55Lkg−1), indicating that arsenic availability is higher for the most toxic sediment sample (Estaque port). This study demonstrates that arsenic speciation play an important role on arsenic mobility and its bioavailability in marine port sediments.

Microbial Reduction of Arsenic-Doped Schwertmannite by Geobacter sulfurreducens

The fate of As(V) during microbial reduction by Geobacter sulfurreducens of Fe(III) in synthetic arsenic-bearing schwertmannites has been investigated. During incubation at pH7, the rate of biological Fe(III) reduction increased with increasing initial arsenic concentration. From schwertmannites with a relatively low arsenic content (<0.3 wt %), only magnetite was formed as a result of dissimilatory iron reduction. However, bioreduction of schwertmannites with higher initial arsenic concentrations (>0.79 wt %) resulted in the formation of goethite. At no stage during the bioreduction process did the concentration of arsenic in solution exceed 120 μgL(1), even for a schwertmannite with an initial arsenic content of 4.13 wt %. This suggests that the majority of the arsenic is retained in the biominerals or by sorption at the surfaces of newly formed nanoparticles. Subtle differences in the As K-edge XANES spectra obtained from biotransformation products are clearly related to the initial arsenic content of the schwertmannite starting materials. For products obtained from schwertmannites with higher initial As concentrations, one dominant population of As(V) species bonded to only two Fe atoms was evident. By contrast, schwertmannites with relatively low arsenic concentrations gave biotransformation products in which two distinctly different populations of As(V) persisted. The first is the dominant population described above, the second is a minority population characterized by As(V) bonded to four Fe atoms. Both XAS and XMCD evidence suggest that the latter form of arsenic is that taken into the tetrahedral sites of the magnetite. We conclude that the majority population of As(V) is sorbed to the surface of the biotransformation products, whereas the minority population comprises As(V) incorporated into the tetrahedral sites of the biomagnetite. This suggests that microbial reduction of highly bioavailable As(V)-bearing Fe(III) mineral does not necessarily result in the mobilization of the arsenic.

Roasting kinetics of high-arsenic copper concentrates: a review

The roasting process of copper concentrates containing variable quantities of arsenic in a fluidized bed regime was analyzed, considering the technical literature published on the topic in the last quarter century. Although emphasis has been given to the analysis in the fluidized bed regime, other processes have also been considered, under a reducing, neutral or oxidizing atmosphere. The kinetic mechanisms of roasting, as well as the models that have been applied or those likely to be used to explain the kinetics of arsenic removal, are analyzed. Regarding the kinetic mechanisms, those that have been applied to copper concentrates with both high and low arsenic content are included. The roasting kinetic model includes the kinetic data analysis techniques, general models, equations and an estimation of the conversion degree through dynamic, differential and integral methods, as well as particular models for mineralogical components, such as smelter dust and copper concentrates with low and high arsenic content.

Growth Effect and Accumulation of as on / in Two Vegetables in Three Types of Chinese Soil

Greenhouse trials with brassica camprestris (BC) and raphanns sativns (RS) grown in three types of Chinese soils (Henan fluvo-aquic soil; Jilin black soil; and Hunan red soil) were conducted to evaluate the growth effect and accumulation of As on/in vegetables resulting from different arsenic contents in soils. The arsenic uptake rate of the vegetables response to type of soils and investigated plant species as well. Experimental results show that low arsenic content in soil has no effect on vegetable growth, but promote the biomass of vegetables. However, higher arsenic concentrations in soils lead to decrease in growth of both leaf- and root systems of the vegetables, especially when arsenic concentration is above 90 mg kg-1 in the soil. Arsenic levels in soils and vegetables correlated positively according to the experimental results. The tests also reveal that vegetables grown in alkali soils may accumulate more arsenic than that in acid soils, which suggests that arsenic in different types of soil may have different impacts on vegetables even with the same concentration. Arsenic concentration in RS is always higher than that in BC during the experiments, which indicates root vegetables may, have greater ability for arsenic uptake from soil than leafy vegetables potentially.

The sources of geogenic arsenic in aquifers at Datong basin, northern China: Constraints from isotopic and geochemical data

Mineralogical, geochemical and zircon U–Pb dating studies were carried out to identify the sources of arsenic in the shallow aquifers of Datong Basin in northern China. A sediment sample from 18 m depth containing 10.3 mg/kg arsenic showed a Zircon U–Pb concordant age of 2528 ± 20 to 271 ± 4 Ma that can be divided into two groups (2528 ± 20 to 1628 ± 21 Ma and 327 ± 4 to 271 ± 4 Ma) and is comparable to that of the sedimentary rocks of Taiyuan (upper Carboniferous) and Shanxi Formation (lower Permian) outcropping to the west of Datong Basin. In contrast, a sediment sample from 22.5 m depth containing 5.7 mg/kg arsenic displayed a Zircon U–Pb concordant age ranging from 2561 ± 21 to 1824 ± 26 Ma that is comparable to that of the Hengshan Complex (Ne-Archaean Precambrian) outcropping to the east of . Electron microscope analysis of the rock samples of Taiyuan and Shanxi Formations revealed that iron oxides and sulfides occurred unevenly in a matrix of clay and organic matter. Arsenic was elevated in the iron oxides with a mean of 660 mg/kg ( n = 11) and 970 mg/kg ( n = 4) for Shanxi and Taiyuan Formations, respectively. Except one pyrite grain, arsenic contents were lower than the detection limit (1 mg/kg) in other pyrite grains. Arsenic in iron oxides from Shanxi and Taiyuan Formations contributed to high arsenic in aquifer sediment of Datong Basin. The low arsenic sediment of Datong Basin is likely to be derived from weathering of the Hengshan Complex with low arsenic content (ranging from 0.37 to 4.14 mg/kg).

Coexistence properties of phase separation and CuPt-ordering in InGaAsP grown on GaAs substrates by organometallic vapor phase epitaxy

CuPt-ordering and phase separation were directly investigated in In 1- x Ga x As y P 1- y with a low arsenic content grown by organometallic vapor phase epitaxy on GaAs substrates. CuPt-ordering and phase separation in samples grown at the substrate temperatures of 630 and 690 °C were characterized by transmission electron diffraction and transmission electron microscopy. Although the immiscibility of InGaAsP was enhanced at the lower substrate temperature, the sample grown at 630 °C showed less phase separation than the 690 °C-grown sample. The degree of CuPt-ordering was significantly enhanced in the sample grown at 630 °C. The results demonstrated that the CuPt-ordering originating from surface reconstruction of P(2×4) suppressed the phase separation even in the miscibility gap. The detailed characterization of the phase separation clearly revealed a vertical composition modulation (VCM) in InGaAsP for the first time. The mechanism of the VCM formation is discussed based on the modulated-strain field on the surface.

Effect of Quantum Well Compressive Strain Above 1% On Differential Gain and Threshold Current Density in Type-I GaSb-Based Diode Lasers

InGaAsSb/AlGaAsSb quantum well (QW) diode laser structures with either 1% or 1.5% compressively strained QWs were grown on GaSb substrates by molecular beam epitaxy. Wide-stripe lasers fabricated from structures of both types have room-temperature operating wavelengths near 2.3 microns. The room-temperature threshold current density of 1-mm-long uncoated devices with 1.5% strained QWs was lower than threshold current density of the 1.0% strained QW devices by nearly a factor of two (120 A/cm2 versus 230 A/cm2 ). Experiment shows that the reduction in threshold current density with increasing QW strain is related to the increase in differential gain and decrease in transparency current density. Optical gain calculations prove that improvement of the QW hole confinement reduces the threshold carrier concentration in laser structures with heavily strained low arsenic content quantum wells.

Nuclear quadrupole resonance study of local bonding in glassyAsxSe1−x

Nuclear quadrupole resonance (NQR) experiments were performed on glassy ${\mathrm{As}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$ to study the local structural order. The bonding in ${\mathrm{As}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$ is governed by preferential bonding (chemical ordering) between arsenic and selenium at arsenic concentrations $x\ensuremath{\leqslant}0.40$; however, the bonding for higher arsenic concentrations is governed mostly by statistical considerations. At concentrations $x\ensuremath{\geqslant}0.45$ the glasses are inhomogeneous with the presence of local regions of different composition. Measurements of the NQR spin echo intensity identify regions formed by arsenic atoms bonded to zero, one, two, or three selenium atoms. The NQR spectral line shapes and the longitudinal relaxation times suggest that these regions have a more ordered structure as compared to the homogeneous samples with low arsenic content. The existence of a small concentration of crystalline inclusions in amorphous ${\mathrm{As}}_{0.60}{\mathrm{Se}}_{0.40}$ is also suggested.

Arsenic fixation on iron-hydroxide-rich and plant litter-containing sediments in natural environments

Iron-hydroxide-rich and plant litter-containing sediments from natural sites contaminated with uranium mine tailing leachates were examined for their ability to adsorb arsenic. The samples with high contents of iron hydroxides (Fetotal concentration, >300 g kg−1) exhibited remarkable fixation of arsenic (up to 40 g As kg−1). This value corresponded approximately to the supersaturation point for natural iron hydroxides under the present conditions, and it was significantly lower than the value found for synthetic iron hydroxides. There was a strong correlation (R=0.8999) between the concentration of iron and that of arsenic at low arsenic contents, indicating adsorption on strong binding sites. Although all the samples had noticeable contents of organic carbon (plant litter), calcium, and manganese, no obvious effect of these elements on arsenic fixation could be detected. The amount of iron hydroxides was found the only fixation-controlling parameter immediately below a leaching water source.

Speciation of Arsenic in Feed Coals and Their Ash Byproducts from Canadian Power Plants Burning Sub-bituminous and Bituminous Coals

The arsenic species in the feed coals and ash byproducts from seven Canadian power plants (including one with a fluidized-bed combustor) that were burning local sub-bituminous and bituminous coals with sulfur contents in the range of 0.30−3.5 wt % have been examined using As X-ray absorption fine structure (XAFS) spectroscopy. The feed coals can be grouped based on their contents of arsenic associated with pyrite (As/pyr) and as As3+ and As5+ (arsenate) species. The arsenic species in sub-bituminous feed coals with low sulfur (0.22−0.38 wt %) and arsenic (1.6−2.2 mg/kg) contents consist of ∼50% As3+ and ∼50% As5+, whereas those with moderate sulfur (0.50 wt %) and arsenic (3.63 mg/kg) contents consist of 84% As/pyr, 7% As3+, and 9% As5+. In bituminous feed coal with low sulfur (0.40 wt %) and arsenic (4.39 mg/kg) contents, the arsenic speciation consists of 34% As/pyr, 12% As3+, and 54% As5+, and for those with high sulfur (2.60−3.56 wt %) and arsenic (54−84 mg/kg) contents, it consists of 77%−82% As/pyr and 18%−23% As5+. The bottom ash produced from sub-bituminous feed coals with low sulfur and arsenic contents consists of 10%−20% As3+ and 80%−90% As5+, and for moderate sulfur (0.50 wt %) and arsenic (3.63 mg/kg), the arsenic speciation consists of 5% As/pyr, 10% As3+, and 85% As5+ as arsenate. For bituminous feed coals with low sulfur and arsenic contents, the bottom ash is entirely As5+, whereas for coals with high sulfur and arsenic contents, the bottom ash consists of 10%−15% As3+ and 85%−90% As5+; and for the fluidized-bed combustor, the bottom ash is entirely As5+ arsenate. The species of arsenic in fly ash from sub-bituminous and bituminous coals are mostly arsenate (As5+), possibly in part incorporated in the glass matrix, and remains the same for coarse- and fine-grained electrostatic precipitator (ESP), baghouse, and stack-emitted ashes. The only difference between the ESP and baghouse fly ash is the higher amount of crystalline arsenates in the hopper fly ash. Neither the sulfur content nor the pyrite content of the feed coal seems to influence the speciation of arsenic, because virtually all of the arsenic in fly ash samples from high-sulfur coal is in the form of arsenate (As5+). However, arsenic (mostly as As5+) in these fly ashes is found to be very surface-enriched, because the amount measured by XPS decreases from >3 wt % to <0.8 wt % in the first few atomic layers. The presence of stable calcium or transition-metal iron hydroxyl arsenate hydrate [(M2+)2Fe3(AsO4)3(OH)4·10H2O] complexes, as determined by X-ray diffractometry, in the fly ash produced from high-sulfur/pyrite feed coals indicates that some of the arsenic might be captured by calcium and iron compounds.

Determination of arsenate and organic arsenic via potentiometric titration of its heteropoly anions

Determination of arsenate based on its conversion to molybdoarsenate heteropoly anions followed by potentiometric titration is described. The titration is realized on the ion-pairing principle using cetylpyridinium chloride (or an analogous titrant containing a lipophilic cation), and is monitored by a carbon paste electrode, although other liquid–polymeric membrane-based electrodes can also be used. Calibration plots of the titrant end-point consumption versus concentration of arsenic were constructed and used to evaluate the content of arsenic in aqueous samples. The method could be applied in the analyses of samples with quite low arsenic content (amounts ≈10 μg As in 50 cm 3 could be titrated). Organic arsenic was determined analogously after the Schöniger combustion of the sample and conversion of its arsenic to arsenate.

COAL FLY ASH-AND COPPER SMELTER DUST-INDUCED MODULATION OF EX VIVO PRODUCTION OF TUMOR NECROSIS FACTOR-ALPHA BY MURINE MACROPHAGES: EFFECTS OF METALS AND OVERLOAD

The objective of this study was to assess the effect of two arsenic-containing particles, coal fly ash (FA) and copper smelter dust (CU), on lung integrity and on the ex vivo release of tumor necrosis factor alpha (TNF- ) by alveolar phagocytes. Particle effects were compared in nonoverload condition on the basis of a low but identical volume load and arsenic content intratracheally instilled in the mouse lung (273 nl/mouse and 186 ng arsenic/mouse; FAL and CUL groups). Other mice received 600 ng arsenic/mouse in amounts of particles leading to different volume loads (FAH and CUH groups: 880 and 273 nl/mouse, respectively). Animals were sacrificed at 1, 6, 30, or 120 d (FAL and CUL groups) or at 6 and 120 d posttreatment (FAH and CUH groups). Biochemical markers and inflammatory cell number and type were analyzed in bronchoalveolar lavage, ex vivo TNF- production by alveolar phagocytes was assessed, and measurement of arsenic lung content and histopathological examinations were performed. Our results show that coal fly ash and copper smelter dust bear distinct inflammatory properties. At the end of the observation period (d 120), the high CU dose (CUH ) produced a fibrotic reaction whereas the high dose of FA particles (FAH ) generated a delayed and persistent lung inflammatory reaction associated with lymphoid noduli. Marked differences in TNFproduction were observed within the CU and FA groups. CU particles, conceivably through their metal content, decreased TNF-production by alveolar phagocytes. Due to their low arsenic content, considerably higher FA particle doses needed to be administered to produce an inhibition of TNF-production. Since high doses of FA (FAH) caused an overload condition, our results do not allow us to decide whether FA-mediated TNF reduction is due to the load administered or to the metallic content.

Ordering in Ga xIn 1− xAs yP 1− y grown on GaAs by metalorganic vapour-phase epitaxy

We have investigated ordering behaviour in MOVPE-grown GaInAsP lattice-matched to GaAs using luminescence and diffraction methods. Our observations indicate that the occurrence of ordering variants depends not only on the growth conditions and the layer composition but is also extremely sensitive to very small substrate misorientation from (0 0 1). For GaInAsP alloys with low arsenic content ( y∼0.15) the ordering behaviour is very similar to that in the well-studied (In,Ga)P system. Polarization dependent PL reveals that in comparison to InGaP, the degree of ordering in the quaternary gets weaker with rising arsenic content. For higher arsenic content ( y⩾0.5) weak ordering is detected only for layers with y≈0.7 when grown with a high V/III ratio in the gas phase. The observed valence-band splittings were ≈12 meV for y=0.15 and 8 meV for y=0.7, respectively.

97/03303 Poisoning by coal smoke containing arsenic and fluoride

SUMMARY: An investigation was made into a disease involving skin pigmentation, keratosis of the hands and feet, dental discoloration, and generalized bone and joint pain, stiffness and rigidity, in the village of Bazhi, Zhijin County, Guizhou Province, People's Republic of China. Measurements were made of the arsenic and fluoride levels of coal, water, air, food, urine and hair in Bazhi and a control village, Xinzhai, in which coal with a low arsenic content was used. Up to 188 persons, including children, in Bazhi and 752 in Xinzhai, were examined for the presence of chronic arsenism, skeletal fluorosis, dental fluorosis and electrocardiogram abnormalities. The coal in Bazhi was found to contain high levels of arsenic and fluoride resulting, after burning in homes without an adequate chimney system for the removal of smoke, in pollution of air and food with arsenic and fluoride. The coal in Xinzhai did not cause arsenic pollution but did produce a higher level of fluoride pollution. Chronic arsenism was found to affect 30% of the persons in Bazhi but none in Xinzhai. In both villages 100% of the children aged 8-15 years had dental fluorosis. Skeletal fluorosis was present in 47.5% of the adults in Bazhi and 56.1% of those in Xinzhai (difference not significant). It was concluded that the endemic disease in Bazhi was caused by pollution by coal smoke containing arsenic and fluoride. It is suggested that arsenic may act synergistically with fluoride so that a lower level of fluoride may produce fluoride toxicity with dental and skeletal fluorosis.

A Problem of Maya Metallurgy in the Medium Grijalva, Central Guatemala, and the Yucatan Peninsula: Copper-Lead Alloy

ABSTRACTThe study of 4 metallic artifacts from the Medium Grijalva, two bells, a bipointed awl, and a needle, and one bell from Huehuetenango, Guatemala, were studied using of elemental analysis by flame atomic absorption spectroscopy (FAAS), metallographic examination and typological classification. Several problems arose, including the need to have a clearer definition of bell types, better knowledge of the technology of production of needles and awls, and problems with the Cu-Pb alloys, especially if a how high a lead content forms a Cu-Pb alloy solution.Early analyses made of bells and copper artifacts from the Maya area, Western Mexico and Southwest USA shows variable but important amounts of lead. The Cu-Pb phase diagram shows a monotectic reaction where the metals have poorcapability of alloying or mixing, forming a eutectic at very low lead concentrations. Few metalographic studies of these alloys are reported in papers about historic metals. However, some ternary Cu-Pb alloys are found in recent literature. Does the low arsenic content as in the analysis of the Cu-PbMayan bells influence the properties of the alloys? The importance of the distribution of types of bells made of Cu-Pb could clarify possible cultural connections and trade among the Maya area, western Mexico and southwest United States. The possible introduction of metallurgy from and trade with South America makes this search of even more importance.

The Savage Lode magnesian skarn in the Marvel Loch gold–silver mine, Southern Cross greenstone belt, Western Australia. Part 1: Structural setting, petrography, and geochemistry

The Marvel Loch mine in the Archean Yilgarn Block. Western Australia, has produced 9.70 t gold and 1.92 t silver from 3.28 × 106 t of oxide–sulphide ore. The deposit is located in the Southern Cross greenstone belt, and occurs within the medium-grade metamorphic aureole of the Ghooli Dome granitoid batholith, about 1.5 km from the granitoid–greenstone contact, The deposit is controlled by a broad ductile shear zone and spatially associated with late syn- to post-mineralization pegmatite dykes. The major orebodies, represented by the Savage Lode, are hosted by a uniform sequence of metakomatiites, and form zoned replacement bodies oriented subparallel to the steeply dipping foliation of the shear zone. Lens-shaped domains of pillowed metakomatiiles (hornblende + cummingtonite + chlorite) are locally preserved between the orebodies.The gangue of the Savage Lode is laterally zoned, and shows distinct similarities to Phanerozoic magnesian skarns. Calcite–olivine rock and calcite–phlogopite–chlorite schist occur in the centre, and are enveloped by three types of calcite-poor ore, namely banded diopside–amphibole rock, quartz–diopside veins, and tremolite–phlogopite schist. The latter grades laterally into subeconomic, outer tremolite–chlorite schists. Local retrogression of prograde alteration minerals is evident in the partial replacement of olivine by iddingsite and serpentine, and in the occurrence of late muscovite, clinozoisite, and prehnite. The gangue in the lode reflects strong carbon dioxide, calcium, and potassium metasomatism.Hydrothermal oxides and sulphides (2–5 vol.%) occur disseminated throughout the Savage Lode. The oxide assemblage includes hercynite–spinel, magnetite, ilmenite, and scheelite, whereas the sulphide assemblage is dominated by pyrrhotite, loellingite, and arsenopyrite. Native gold occurs as discrete grains (0.001–3 mm) intergrown with sulphides or enclosed in gangue minerals. The average magnesian ore skarn is characterized by a MgO–FeO ratio of 2.0:1, a Au–Ag ratio of 1.7:1, and low base metal (&lt; 500 ppm), anomalous tungsten (20–40 ppm), and high arsenic (2900 ppm) contents. The Savage and other lodes in the Marvel Loch mine may be classified as gold or gold–silver skarns by economic metal content. The magnesian rather than calcic nature of the Marvel Loch skarns is related to the high magnesium content (21 wt.% MgO) of the precursor metakomatiite rocks.