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Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth’s water.

This study identifies new key parameters that have resulted in the formation of an economic-scale bentonite resource on the emergent island of Milos. It is concluded that in an emergent volcanic arc setting, the hydrology needed to form a bentonite deposit is not constrained to the marine environment and can be connected to emergent parts of the volcanic edifice. High-precision geochronology indicates bentonite development happens on volcanic timescales (10-100 kyrs.) A cumulative volcanic and sub-volcanic pile coeval with the formation of bentonite suggests that multiple magmatic episodes over narrow timeframes provide and sustain the thermal driver for significant bentonite development., This study identifies new key parameters that have resulted in the formation of an economic-scale bentonite resource on the emergent island of Milos. It is concluded that in an emergent volcanic arc setting, the hydrology needed to form a bentonite deposit is not constrained to the marine environment and can be connected to emergent parts of the volcanic edifice. High-precision geochronology indicates bentonite development happens on volcanic timescales (10-100 kyrs.) A cumulative volcanic and sub-volcanic pile coeval with the formation of bentonite suggests that multiple magmatic episodes over narrow timeframes provide and sustain the thermal driver for significant bentonite development.

Studies have been carried out of the oxygen and hydrogen isotope compositions of propylitic mineral separates (epidote, chlorite, and quartz), selected potassic mineral separates (quartz and magnetite), and quartz-hosted fluid inclusions from around the E48 and E26 deposits in the Northparkes porphyry Cu-Au district, New South Wales, Australia. The strontium isotope composition of epidote was also determined to test for the potential contribution of seawater in the Northparkes system given the postulated island-arc setting and submarine character of some country rocks. The results suggest that warming and equilibrating meteoric water alone cannot have generated the observed fluid characteristics and was not solely responsible for propylitic alteration. Rather, fluids containing a magmatic component must have been present throughout much of the propylitic halo, to distances of at least 1.6 km from the E48 deposit. The most likely scenario is one involving expulsion, cooling, and equilibration of magmatic fluid up to around 3 km from the porphyry system, beyond which a mixing interface with external meteoric waters developed. It is concluded that ore formation was purely an orthomagmatic process driven by thermal and chemical gradients around the quartz monzonite porphyry intrusions., Studies have been carried out of the oxygen and hydrogen isotope compositions of propylitic mineral separates (epidote, chlorite, and quartz), selected potassic mineral separates (quartz and magnetite), and quartz-hosted fluid inclusions from around the E48 and E26 deposits in the Northparkes porphyry Cu-Au district, New South Wales, Australia. The strontium isotope composition of epidote was also determined to test for the potential contribution of seawater in the Northparkes system given the postulated island-arc setting and submarine character of some country rocks. The results suggest that warming and equilibrating meteoric water alone cannot have generated the observed fluid characteristics and was not solely responsible for propylitic alteration. Rather, fluids containing a magmatic component must have been present throughout much of the propylitic halo, to distances of at least 1.6 km from the E48 deposit. The most likely scenario is one involving expulsion, cooling, and equilibration of magmatic fluid up to around 3 km from the porphyry system, beyond which a mixing interface with external meteoric waters developed. It is concluded that ore formation was purely an orthomagmatic process driven by thermal and chemical gradients around the quartz monzonite porphyry intrusions.

New delta13C, delta18O, and delta34S data from the Karakaene Ndi skarn, Au occurrences along the western margin of the Kofi series, and zircons within plutonic rocks of the Faleme batholith are combined with existing data from the Loulo Au deposits to model the contribution of magmatic volatiles to Au mineralisation. Comparison of the C and O isotope data with water-rock reaction models indicates the Loulo Au deposits formed primarily through unmixing of an aqueous carbonic fluid derived from the devolatilisation of sedimentary rocks with an organic carbon component. Isotopic data suggest the presence of a hypersaline brine that enhanced this phase separation including components derived from both Kofi series evaporite horizons interlayered with the dolostones and a magmatic-hydrothermal brine. This magmatic-hydrothermal component is particularly apparent in O, C, and S isotope data from the Gara deposit and Au prospects immediately adjacent to the Faleme batholith. It is concluded that there was a critical role for magmatism in the development of early alteration assemblages in the Loulo district, in the genesis of the Faleme iron skarns, and in those Au deposits that formed in response to fluid mixing., New delta13C, delta18O, and delta34S data from the Karakaene Ndi skarn, Au occurrences along the western margin of the Kofi series, and zircons within plutonic rocks of the Faleme batholith are combined with existing data from the Loulo Au deposits to model the contribution of magmatic volatiles to Au mineralisation. Comparison of the C and O isotope data with water-rock reaction models indicates the Loulo Au deposits formed primarily through unmixing of an aqueous carbonic fluid derived from the devolatilisation of sedimentary rocks with an organic carbon component. Isotopic data suggest the presence of a hypersaline brine that enhanced this phase separation including components derived from both Kofi series evaporite horizons interlayered with the dolostones and a magmatic-hydrothermal brine. This magmatic-hydrothermal component is particularly apparent in O, C, and S isotope data from the Gara deposit and Au prospects immediately adjacent to the Faleme batholith. It is concluded that there was a critical role for magmatism in the development of early alteration assemblages in the Loulo district, in the genesis of the Faleme iron skarns, and in those Au deposits that formed in response to fluid mixing.

New geochemical data are presented for the composite units of the Mount Kinabalu granitoid intrusion of Borneo and explore discrimination between crustal- and mantlederived granitic magmas. The geochemical data demonstrate that the units making up this composite intrusion became more potassic through time. This was accompanied by an evolution of isotope ratios from a continental-affinity towards a slightly more mantle-affinity (87Sr/86Sri ~0.7078; 143Nd/144Ndi ~0.51245; 206Pb/204Pbi ~18.756 for the oldest unit compared to 87Sr/86Sri ~0.7065, 143Nd/144Ndi ~0.51250 and 206Pb/204Pbi ~18.721 for the younger units). Oxygen isotope ratios (calculated whole-rock δ18O of +6.5–9.3‰) do not show a clear trend with time. The isotopic data indicate that the magma cannot result only from fractional crystallisation of a mantle-derived magma. Alkali metal compositions show that crustal anatexis is also an unsuitable process for genesis of the intrusion. The data indicate that the high-K units were generated by fractional crystallisation of a primary, mafic magma, followed by assimilation of the partially melted sedimentary overburden. We present a new, Equilibrated Major Element – Assimilation with Fractional Crystallisation (EME-AFC) approach for simultaneously modelling the major element, trace element, and radiogenic and oxygen isotope compositions during such magmatic differentiation; addressing the lack of current AFC modelling approaches for felsic, amphibole- or biotite-bearing systems. We propose that Mt Kinabalu was generated through low degree melting of upwelling fertile metasomatised mantle driven by regional crustal extension in the Late Miocene.

In a terrestrial Triassic–Jurassic boundary succession of southern Sweden, perfectly zoned sphaerosiderites are restricted to a specific sandy interval deposited during the end-Triassic event. Underlying and overlying this sand interval there are several other types of siderite micromorphologies, i.e. poorly zoned sphaerosiderite, spheroidal (ellipsoid) siderite, spherical siderite and rhombohedral siderite. Siderite overgrowths occur mainly as rhombohedral crystals on perfectly zoned sphaerosiderite and as radiating fibrous crystals on spheroidal siderite. Concretionary sparry, microspar and/or micritic siderite cement postdate all of these micromorphologies. The carbon isotope composition of the siderite measured by conventional mass spectrometry shows the characteristic broad span of data, probably as a result of multiple stages of microbial activity. SIMS (secondary ion mass spectrometry) revealed generally higher δ13C values for the concretionary cement than the perfectly zoned sphaerosiderite, spheroidal siderite and their overgrowths, which marks a change in the carbon source during burial. All the various siderite morphologies have almost identical oxygen isotope values reflecting the palaeo-groundwater composition. A pedogenic/freshwater origin is supported by the trace element compositions of varying Fe:Mn ratios and low Mg contents. Fluctuating groundwater is the most likely explanation for uniform repeated siderite zones of varying Fe:Mn ratios reflecting alternating physiochemical conditions and hostility to microbial life/activity. Bacterially mediated siderite precipitation likely incorporated Mn and other metal ions during conditions that are not favourable for the bacteria and continued with Fe-rich siderite precipitation as the physico-chemical conditions changed into optimal conditions again, reflecting the response to groundwater fluctuations.

Minerals are vital to support economic growth and the functioning of modern society. Demand for minerals is increasing as global population expands and minerals are used in a greater range of applications, particularly associated with the deployment of new technologies. While concerns about future mineral scarcity have been expressed, these are generally unfounded and based on over-simplistic analysis. This paper considers recent debate around security of mineral supply and technical, geosciences-based options to improve utilization of the resource base and contribute to replenishing reserves. History suggests that increasing demand for minerals and higher prices will generally lead to technological and scientific innovation that results in new or alternative sources of supply. Recent assessments of global mineral endowment suggest that society should be optimistic about its ability to meet future demand for minerals, provided that there is continued innovation and investment in science and technology. Reducing energy consumption and breaking the current link between metal production and greenhouse gas emissions are among the greatest challenges to secure a sustainable mineral supply. However, widespread adoption of low-carbon mineral extraction technologies, underpinned by multidisciplinary research, and increased global utilization of low-carbon energy sources will allow these challenges to be met.

The Kago low-sulphidation deposit is located within a circular depression on the edge of the southwest Nansatsu district of Japan, which is punctuated by high-sulphidation-type mineralisation. Gold and silver was excavated by underground mining over a 400-year period up to the mid-20th century. The deposit, composed of a series of NE-SW trending veins, is hosted in the Shimanto Supergroup, an extensive interstratified sandstone/mudstone formation stretching from southwest Shikoku to southern Kyushu. Host rocks are strongly altered and exhibit an argillic composition of illite, illite/smectite mixed-layer minerals and alteration minerals with the presence of adularia suggesting a neutral pH condition. Ore minerals recognised at the deposit are electrum, polybasite, chalcopyrite, covellite and pyrite. EPMA carried out on high-grade samples containing visible electrum showed that the Au composition of electrum is uniform with measurements of 66-69 wt% Au. 40Ar/39Ar age dating carried out on adularia hosted in colloform, crustiform and brecciated veins gave an age range of 4.23-4.0 Ma. Fluid inclusion microthermometry points towards a mixed origin fluid, dominated by fluids of meteoric origin. The presence of high and low-sulphidation deposits in close proximity has here been shown to have been generated within the same mineralisation time frame. Thus, Kago is likely to have been related to the same hydrothermal episode, whilst exhibiting a completely different genetic condition of mineralisation., The Kago low-sulphidation deposit is located within a circular depression on the edge of the southwest Nansatsu district of Japan, which is punctuated by high-sulphidation-type mineralisation. Gold and silver was excavated by underground mining over a 400-year period up to the mid-20th century. The deposit, composed of a series of NE-SW trending veins, is hosted in the Shimanto Supergroup, an extensive interstratified sandstone/mudstone formation stretching from southwest Shikoku to southern Kyushu. Host rocks are strongly altered and exhibit an argillic composition of illite, illite/smectite mixed-layer minerals and alteration minerals with the presence of adularia suggesting a neutral pH condition. Ore minerals recognised at the deposit are electrum, polybasite, chalcopyrite, covellite and pyrite. EPMA carried out on high-grade samples containing visible electrum showed that the Au composition of electrum is uniform with measurements of 66-69 wt% Au. 40Ar/39Ar age dating carried out on adularia hosted in colloform, crustiform and brecciated veins gave an age range of 4.23-4.0 Ma. Fluid inclusion microthermometry points towards a mixed origin fluid, dominated by fluids of meteoric origin. The presence of high and low-sulphidation deposits in close proximity has here been shown to have been generated within the same mineralisation time frame. Thus, Kago is likely to have been related to the same hydrothermal episode, whilst exhibiting a completely different genetic condition of mineralisation.

In north-west Wales vein mineralization is hosted by the Ordovician Snowdon Volcanic Group, and older sedimentary rocks. Mineralization typically consists of narrow, steeply dipping base metal veins, stockworks, disseminated sulfides and quartz-sulfide cemented breccia zones. Sulfur isotope analyses were carried out on vein sulfides and country rocks to elucidate ore sulfur source/s. The volcanic-hosted and the majority of sedimentary rock-hosted sulfides have delta S-34 from +9.1 to +22.3 parts per thousand, with mean vein delta S-34 of +12.2 +/- 3.7 parts per thousand. The Snowdon Volcanic Group is generally considered to represent a reservoir of isotopically heavy sulphur with mean delta S-34 of +11.7 parts per thousand +/- 4.5 parts per thousand. The sedimentary rock diagenetic sulfides are typically heavier. These values are thus compatible with a typical volcanogenic massive sulfide system, with sulfur originating from a combination of leaching of volcanic host lithologies, and reduction of Ordovician seawater. The delta S-34 ore sulfides from around Snowdon are comparable to those found in Ordovician age volcanogenic massive sulfide deposits globally.

In magmatic-hydrothermal and associated geothermal systems, acidic magmatic-derived fluids (pH<3) commonly discharge from springs proximal to the vent of active (degassing) volcanoes and more alkaline (pH>5) geothermal fluids are typically limited to lateral outflows some distance from the main vent. Here we describe an unusual hydrothermal system associated with Savo volcano, a recently active (1830–40) trachyte-dominated island arc stratovolcano in the Solomon Islands. Hot springs (~100°C) near to the volcanic crater discharge alkaline waters instead of the more commonly recognised acidic fluids. The hydrothermal system of Savo dominantly discharges sinter and travertine-forming alkaline sulphate (pH 7–8) waters at hot springs on its upper flanks, in addition to a small number of lower discharge acid sulphate springs (pH 2–7). Alkaline sulphate springs discharge dilute, chloride-poor (<50 mg/l), sulphate- (>600 mg/l) and silica-rich (>250 mg/l) fluids. They have restricted δ34SSO4 (5.4 ± 1.5‰) and δ18OH2O values (−4‰; local non-thermal groundwater is −8‰). Acid sulphate springs discharge low chloride (<20 mg/l), high sulphate (300–800 mg/l) waters, with variable silica (100–300 mg/l) and distinctly lower δ34SSO4 values (−0.6 ± 2.5‰) compared to the alkaline sulphate fluids. They also display high δ18OH2O and δDH2O relative to non-thermal groundwater. Geochemical modelling shows that water–rock reaction and dilution in the presence of secondary anhydrite, pyrite and quartz leads to chloride being diluted to low concentrations, whilst maintaining high sulphate and silica concentrations in the fluid. Strontium, oxygen and hydrogen isotopes confirm water–rock reaction and mixing with groundwater as primary controls on the composition of the alkaline sulphate springs. The highly unusual dilute chemistry of all discharges at Savo is a consequence of high regional rainfall, i.e. climatic control, and results from open system mixing at depth between hydrothermal and meteo

Sulphur isotope studies of the Platreef, South Africa, indicated that magmatic signatures are preserved in early-formed sulphide droplets within the Platreef pyroxenites in the area from Sandsloot to Witrivier. These values are comparable to sulphide inclusions in diamonds in the nearby Klipspringer kimberlite and are considered to have a primary mantle origin. Later sulphides found in calc-silicate floor rocks at Sandsloot and Zwaltfontein and in xenoliths of calc-silicate throughout the section indicate an input of country rock S. Previous studies indicated that, in areas where the sedimentary floor rocks contain appreciable sulphides rather than sulphates, the Platreef sulphides are contaminated with country-rock S. Sulphur saturation in the Platreef magma took place before contamination, probably in a staging chamber prior to intrusion. A major pulse of magma entrained the preformed PGE- rich sulphides and was injected to form the Platreef, where assimilation of country-rock sulphides upgraded the S content on a local scale, and hydrothermal leaching introduced S from country-rock sulphates into later stage sulphides, also on a local scale., Sulphur isotope studies of the Platreef, South Africa, indicated that magmatic signatures are preserved in early-formed sulphide droplets within the Platreef pyroxenites in the area from Sandsloot to Witrivier. These values are comparable to sulphide inclusions in diamonds in the nearby Klipspringer kimberlite and are considered to have a primary mantle origin. Later sulphides found in calc-silicate floor rocks at Sandsloot and Zwaltfontein and in xenoliths of calc-silicate throughout the section indicate an input of country rock S. Previous studies indicated that, in areas where the sedimentary floor rocks contain appreciable sulphides rather than sulphates, the Platreef sulphides are contaminated with country-rock S. Sulphur saturation in the Platreef magma took place before contamination, probably in a staging chamber prior to intrusion. A major pulse of magma entrained the preformed PGE- rich sulphides and was injected to form the Platreef, where assimilation of country-rock sulphides upgraded the S content on a local scale, and hydrothermal leaching introduced S from country-rock sulphates into later stage sulphides, also on a local scale.

Savo volcano, Solomon Islands, is host to an active hydrothermal system that is potentially analogous to high sulfidation epithermal Au deposits. Chemical and stable isotope data from fluids discharged at the surface indicate a relatively shallow condensate layer fed by magmatic volatiles including SO2. Acidic condensates are buffered to high pH by wall rock reaction, leading to the precipitation of unusual carbonate-silica sinters at the surface, in an environment where low pH fluids and associated products would be expected.

Savo is a recently emergent volcano. An active geothermal system has been present for at least 50 years, expressed at the surface by numerous hot springs, fumaroles and steaming ground. Samples of water and steam were collected from geothermal features and non-thermal springs and wells, and representative samples of altered rocks and precipitates were collected from geothermal areas. Analysis of the waters for anion, cation and stable isotope composition shows that the waters discharging at the surface fall into two groups Reoka type fluids have the high sulfate, low pH, and enriched δ18O and δD values typical of steam heated acid sulfate waters, where shallow groundwater is heated by rising steam and gas. Isotopically light H2S is oxidised in the near surface environment to produce the sulfate content. Rembokola type fluids have chemistry distinct from the Reoka type fluids, despite the two being found within close proximity (<10 m). Rembokola Type fluids produce a carbonate sinter, so are assumed to be saturated with bicarbonate. The aqueous sulfate has heavy δ34S, suggesting that it is not exclusively produced by the oxidation of H2S in the near surface environment. We suggest that condensation of volcanic gases (including CO2 and isotopically heavy SO2) into meteoric-derived groundwater in the upper levels of the volcanic edifice produces these carbonate–sulfate waters. The presence of SO2 suggests that there is a degassing magma at depth, and potentially a high sulfidation-type epithermal system beneath the steam heated zone.

The aim of the meeting was both to highlight the importance of mineral deposits and to increase understanding of their links to Earth systems. The first two papers address the effects of meteorite impact, both in general and with reference to the Witwatersrand basin. A group of papers then considers the role of mineral deposits in constraining models of tectonic evolution on different scales, revealing that Archaean cratons are more richly endowed with metals than younger rocks, with the distinctive metal signature of each reflecting mantle heterogeneity, and that deposit types vary in time as a function of formation and preservation processes. Heat-flow constraints on the Ashanti gold belt and the plate-tectonic frameworks for giant gold deposits and for the Urals metallogenic province are discussed and other studies of particular aspects of early source rocks and conditions for ore genesis include: Terrane and basement discrimination in northern Britain using sulphur isotopes and mineralogy of ore deposits, by Lowry D., Boyce A.J., Fallick A.E., Stephens W.E. and Grassineau N.V., p.133-151, 80 refs., which compares four terranes; The terrestrial record of stable sulphur isotopes: a review of the implications for evolution of Earth's sulphur cycle, by Farquhar J. and Wing B.A., p.167-177, 43 refs.; Reactive iron enrichment in sediments deposited beneath euxinic bottom waters: constraints on supply by shelf recycling, by Raiswell R. and Anderson T.F., p.179-194, 98 refs., on a model derived from studies of modern basins such as the Black Sea and Cariaco basin; and Distinguishing biological from hydrothermal signatures via sulphur and carbon isotopes in Archaean mineralisations at 3.8 and 2.7 Ga, by Grassineau N.V., Appel P.W.U., Fowler C.M.R. and Nisbet E.G., p.195-212, 75 refs, a discussion of the Isua and Belingwe greenstone belts. Finally, deposit-forming sedimentary and igneous processes are addressed in two papers on diamond placers and porphyry Cu-Au-Mo deposi, The aim of the meeting was both to highlight the importance of mineral deposits and to increase understanding of their links to Earth systems. The first two papers address the effects of meteorite impact, both in general and with reference to the Witwatersrand basin. A group of papers then considers the role of mineral deposits in constraining models of tectonic evolution on different scales, revealing that Archaean cratons are more richly endowed with metals than younger rocks, with the distinctive metal signature of each reflecting mantle heterogeneity, and that deposit types vary in time as a function of formation and preservation processes. Heat-flow constraints on the Ashanti gold belt and the plate-tectonic frameworks for giant gold deposits and for the Urals metallogenic province are discussed and other studies of particular aspects of early source rocks and conditions for ore genesis include: Terrane and basement discrimination in northern Britain using sulphur isotopes and mineralogy of ore deposits, by Lowry D., Boyce A.J., Fallick A.E., Stephens W.E. and Grassineau N.V., p.133-151, 80 refs., which compares four terranes; The terrestrial record of stable sulphur isotopes: a review of the implications for evolution of Earth's sulphur cycle, by Farquhar J. and Wing B.A., p.167-177, 43 refs.; Reactive iron enrichment in sediments deposited beneath euxinic bottom waters: constraints on supply by shelf recycling, by Raiswell R. and Anderson T.F., p.179-194, 98 refs., on a model derived from studies of modern basins such as the Black Sea and Cariaco basin; and Distinguishing biological from hydrothermal signatures via sulphur and carbon isotopes in Archaean mineralisations at 3.8 and 2.7 Ga, by Grassineau N.V., Appel P.W.U., Fowler C.M.R. and Nisbet E.G., p.195-212, 75 refs, a discussion of the Isua and Belingwe greenstone belts. Finally, deposit-forming sedimentary and igneous processes are addressed in two papers on diamond placers and porphyry Cu-Au-Mo deposi

The occurrence of vent fauna and isotopic evidence for surface fluid interactions support a near-seafloor origin for the economic mineral deposits of the Irish orefield. Classically epigenetic mineralisation represents a minor component of the ore systems and is believed to have formed at depth, in part synchronously with overlying, near-seafloor sulphides that precipitated in partially lithified sediment. Constraints from fluid PVT modelling suggest that some of the later paragenetic phases related to such activity formed at depths of at least 165 m beneath the seafloor. True exhalative components are restricted in occurrence and appear to be best developed in the SW of the orefield. It is possible that mineralisation was diachronous as well as episodic., The occurrence of vent fauna and isotopic evidence for surface fluid interactions support a near-seafloor origin for the economic mineral deposits of the Irish orefield. Classically epigenetic mineralisation represents a minor component of the ore systems and is believed to have formed at depth, in part synchronously with overlying, near-seafloor sulphides that precipitated in partially lithified sediment. Constraints from fluid PVT modelling suggest that some of the later paragenetic phases related to such activity formed at depths of at least 165 m beneath the seafloor. True exhalative components are restricted in occurrence and appear to be best developed in the SW of the orefield. It is possible that mineralisation was diachronous as well as episodic.

This study reports new laser fluorination oxygen isotope data for 60 volcanic rocks and 15 sediments distributed over the whole length of the Banda Arc, eastern Indonesia. The melt oxygen isotope values (δ

The 2.95-2.8 Ga Yalgoo-Singleton greenstone belt is dissected by a number of structures including the unexposed c.60 km Mougooderra shear zone, host to most of the belt's current 1 000 000 oz Au resource, whose geometry and kinematics have been poorly understood although recent structural analysis has revealed that mineralisation along its length is structurally-controlled and conforms to a fault-valve model whereby high pore fluid pressures have facilitated reverse movement along a steeply-oriented structure. A paragenetic study reveals the sulphide assemblage at the 400 000 oz Au Silverstone deposit consists of pyrite, pyrrhotite and arsenopyrite, with minor chalcopyrite and Sb-sulphides, primarily ullmannite (NiSbS) and stibnite (Sb2S3). The ore zone has experienced intense carbonate alteration, with a chlorite-sericite-albite-calcite alteration assemblage in mafic protoliths and talc-magnesite-fuchsite assemblage in ultramafic protoliths. At least two discrete Au-bearing phases are identified, comprising an earlier phase of arsenopyrite and a later phase of Au-bearing antimony sulphides. Gold occurs both as inclusions and as free gold. These assemblages and textures are very consistent at deposits over a strike length of over 30 km. The uniformity of mineral assemblages, ore textures and sulphide S isotope data at deposits along the length of the shear zone supports structural analysis and demonstrate that mineralisation across the belt formed as part of the same episode of crustal shortening., 4 refs., The 2.95-2.8 Ga Yalgoo-Singleton greenstone belt is dissected by a number of structures including the unexposed c.60 km Mougooderra shear zone, host to most of the belt's current 1 000 000 oz Au resource, whose geometry and kinematics have been poorly understood although recent structural analysis has revealed that mineralisation along its length is structurally-controlled and conforms to a fault-valve model whereby high pore fluid pressures have facilitated reverse movement along a steeply-oriented structure. A paragenetic study reveals the sulphide assemblage at the 400 000 oz Au Silverstone deposit consists of pyrite, pyrrhotite and arsenopyrite, with minor chalcopyrite and Sb-sulphides, primarily ullmannite (NiSbS) and stibnite (Sb2S3). The ore zone has experienced intense carbonate alteration, with a chlorite-sericite-albite-calcite alteration assemblage in mafic protoliths and talc-magnesite-fuchsite assemblage in ultramafic protoliths. At least two discrete Au-bearing phases are identified, comprising an earlier phase of arsenopyrite and a later phase of Au-bearing antimony sulphides. Gold occurs both as inclusions and as free gold. These assemblages and textures are very consistent at deposits over a strike length of over 30 km. The uniformity of mineral assemblages, ore textures and sulphide S isotope data at deposits along the length of the shear zone supports structural analysis and demonstrate that mineralisation across the belt formed as part of the same episode of crustal shortening.

Scotland’s first ever commercial gold mine, with a current resource of 266 000 oz Au and 1 096 000 oz Ag, has ore consisting of a series of hydrothermal quartz+/-carbonate veins that occupy an anastomosing, transtensional fault zone striking NE-SW, sub-parallel to the nearby Tyndrum fault; mineralisation crosscuts multiply deformed stratigraphy of the Dalradian Supergroup, metamorphosed to epidote-amphibolite facies at c.470 Ma. Whilst Cononish displays broad commonalities with the orogenic group of ore deposits, K-feldspar alteration in an auriferous breccia yield Ar/Ar ages of c.408-407 Ma, linking mineralisation to the main episode of shear-modulated, post-Caledonian magmatism in the Grampian belt. S and Pb isotope analyses were conducted on a suite of early auriferous and later, non-auriferous vein sulphides in order to resolve the source(s) of S and Pb, and by inference the source(s) of gold. A comparison of the Pb isotopes with sedex, Dalradian and magmatic end-members supports the hypothesis that mixing between sedex and Dalradian strata was the main source of Pb to both auriferous and non-auriferous sulphides, implying that, given the homogeneity of Pb sources, these strata were not a major gold source and post-Caledonian magmatism was the most plausible genetic contributor., 9 refs., Scotland’s first ever commercial gold mine, with a current resource of 266 000 oz Au and 1 096 000 oz Ag, has ore consisting of a series of hydrothermal quartz+/-carbonate veins that occupy an anastomosing, transtensional fault zone striking NE-SW, sub-parallel to the nearby Tyndrum fault; mineralisation crosscuts multiply deformed stratigraphy of the Dalradian Supergroup, metamorphosed to epidote-amphibolite facies at c.470 Ma. Whilst Cononish displays broad commonalities with the orogenic group of ore deposits, K-feldspar alteration in an auriferous breccia yield Ar/Ar ages of c.408-407 Ma, linking mineralisation to the main episode of shear-modulated, post-Caledonian magmatism in the Grampian belt. S and Pb isotope analyses were conducted on a suite of early auriferous and later, non-auriferous vein sulphides in order to resolve the source(s) of S and Pb, and by inference the source(s) of gold. A comparison of the Pb isotopes with sedex, Dalradian and magmatic end-members supports the hypothesis that mixing between sedex and Dalradian strata was the main source of Pb to both auriferous and non-auriferous sulphides, implying that, given the homogeneity of Pb sources, these strata were not a major gold source and post-Caledonian magmatism was the most plausible genetic contributor.