Chris L Hayward | University of Edinburgh (original) (raw)
Papers by Chris L Hayward
8159 METEORITE. E.V. Christou, L.J. Hallis, L. Daly, I. McCarroll, M. Garbrecht, L. Jang, C.L. Ha... more 8159 METEORITE. E.V. Christou, L.J. Hallis, L. Daly, I. McCarroll, M. Garbrecht, L. Jang, C.L. Hayward, Y. Liu, J. Cairney and M.R. Lee. School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK; Centre for Microscopy & Microanalysis, University of Sydney, Sydney, Australia; School of Geosciences, Grant Institute, University of Edinburgh, Edinburgh, UK. E-mail: e.christou.1@research.gla.ac.uk
theatre architecture, as well as in the historical background to its construction. e re-foundatio... more theatre architecture, as well as in the historical background to its construction. e re-foundation of Sikyon in BC by Demetrios Poliorketes involved the city's relocation
Treatise on Geochemistry, 2014
Gold is a rare metal normally occurring in low abundances (1–5 ppb) in the Earth's crust. It ... more Gold is a rare metal normally occurring in low abundances (1–5 ppb) in the Earth's crust. It is strongly siderophilic, typically occurs in its native form or as an alloy with silver, and is chemically inert. It is nevertheless weakly soluble in the presence of a variety of complexing agents of which two – chloride and bisulfide ligands – are widely implicated in the mobilization and concentration of gold in the Earth's crust. As a result, gold deposits of varying size and economic viability are fairly common, although there is a tendency for concentrations to occur in close spatial and temporal association with major orogenic events. One auriferous sequence – the Archean-aged Witwatersrand Basin – stands out for its unique endowment and convoluted ore-forming paragenesis. The geochemistry of gold in the Witwatersrand deposits provides a number of useful insights into the nature and origin of these ores. Witwatersrand gold is enigmatic in that it exhibits variable morphologies, suggesting two modes of formation – initial fluvial deposition of flattened and overturned micronuggets derived from a heterogeneous provenance and crystalline gold precipitated from hot, metal-charged aqueous solutions. This dichotomy is responsible for contrasting ideas on Witwatersrand ore genesis that have resulted in the century-long debate between placer and hydrothermal models. Gold exhibits variable Ag and Hg contents that are distinguishable at the scale of individual goldfields and mines – systematic variations as a function of stratigraphy and burial depth are less evident. Smaller variance also occurs between gold grains at a meter to millimeter scale, with individual grains also exhibiting compositional heterogeneity at the micron scale. This pattern argues in favor of gold that was originally derived from a heterogeneous source terrane – carrying a fingerprint of its source in its chemical composition – and then substantially recrystallized by circulating basinal fluids over very limited transport distances but essentially retaining its source-area chemical traits. The localized remobilization of gold that is envisaged on the basis of gold morphological and chemical evidence is consistent with a modified placer origin for Witwatersrand ores.
Quaternary Science Reviews, 2017
Correlating tephras and cryptotephras using glass compositional analyses and numerical and statis... more Correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods: review and evaluation. Quaternary Science Reviews (
European Journal of Mineralogy, 1994
Electron microprobe analyses of a suite of four sinhalites (all of gem quality) indicate that sin... more Electron microprobe analyses of a suite of four sinhalites (all of gem quality) indicate that sinhalites (ideal formula MgAlBO 4 ) accommodate excess aluminium and small amounts of iron at the expense of magnesium. The results of structure determination and refinement, based upon single-crystal X-ray diffraction data, are in agreement with previous work. Sinhalite is isostructural with forsterite, having space group Pbnm. The cell parameters are a = 4.3320(4) A, b = 9.8819(5) A, c = 5.6813(4) A. The structure was refined to R u = 0.017, R w = 0.019 with 427 observed reflections and 41 refinable parameters. The assumed ordering scheme of [Mg 0.91 Fe 0.015 Al 0.05 □ 0.025 ] M2 Al M1 BO 4 was deduced from the microprobe analyses. Average B-O, M1-O and M2-O bond lengths are 1.499, 1.903 and 2.092 A respectively. Visible absorption spectra are indicative of extremely low Fe 3+ contents in these sinhalites, suggesting that the main substitutional mechanisms are 3Mg 2+ ↔ 2Al 3+ + □ and Mg 2+ ↔ Fe 2+ , where □ represents a vacancy
Geoarchaeology, 1996
At least 1.5 x lo6 m3 of oolitic limestone from the Corinthia was quarried during antiquity, main... more At least 1.5 x lo6 m3 of oolitic limestone from the Corinthia was quarried during antiquity, mainly for construction. Previously, it has only been possible to speculate about the sources of oolite in ancient constructions because of its uniformity on the macroscopic scale. However, thin section petrography demonstrates a considerable degree of petrographic variation within the oolite of one group of quarries a t Examilia, 4.5 krn ENE of Ancient Corinth. Variation in the characteristics of the ooids and the amount and types of noncarbonate grains in the oolite from different quarries permit the identification of five petrographically distinct zones in the Examilia quarries. This offers great potential as a high resolution provenancing tool, and the data have numerous other archaeological applications. Following these results, the work has been extended to become a comprehensive study of all Corinthian oolite quarries. 0 1996 John Wiley & Sans, Inc.
Physics and Chemistry of Minerals, Aug 1, 1997
… 2010, held 2-7 May …, May 1, 2010
The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive act... more The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive activity repeatedly over the last 16 years. An intense seismic and intrusive event culminated in a small basaltic fissure eruption on the eastern flanks, lasting from 20th March to 12th April. In the early morning of 14th April, a summit eruption, preceded by an intense seismic swarm, commenced at the volcano. During the first few hours activity was subglacial but a visible plume was observed at 6 AM and was followed by onset of meltwater ...
6 The session was organized by Maria Gurova (Bulgaria), with co-organizers Clive Bonsall (UK), Ba... more 6 The session was organized by Maria Gurova (Bulgaria), with co-organizers Clive Bonsall (UK), Barbara Voytek (USA), and Dušan Borić (Serbia/UK) sults of trace element analyses using LA-ICP-MS and EPMA techniques are discussed.
The amygdaloidal carbonatite lavas at Qasiarsuk have a primary phenocryst assemblage of calcite, ... more The amygdaloidal carbonatite lavas at Qasiarsuk have a primary phenocryst assemblage of calcite, fluor-apatite and magnetite set in a groundmass of calcite, apatite and iron oxides, and minor dolomite. Cathodoluminescence reveals a complex history, both for the major minerals which show zonal growth, and for important Nb and REE accessory phases which include pyrochlore and perovskite. The REE reside in fluor/hydrous-carbonates included exclusively in apatite. These REE minerals are similar to synthetic phases from hydrothermal experiments, but probably crystallised in equilibrium with a late-stage volatile-rich carbonate melt. Apart from low-temperature alteration, the rocks have been little disturbed since their extrusion during the earliest phase of development of the Gardar Alkaline Igneous Province.
The structure and electronic properties of trigonal and orthorhombic boric oxide (B 2 O 3) are st... more The structure and electronic properties of trigonal and orthorhombic boric oxide (B 2 O 3) are studied using periodic ab initio Hartree-Fock method. The optimised structural parameters for two B 2 O 3 polymorphs are in good agreement with experimental data. The analyses of their electronic structures provide insights into the chemical nature of the B-O bond and the way in which it changes with the coordination number around boron and oxygen. Our quantum-chemical study suggests that the orthorhombic form is more ionic than the trigonal form and that the coordination number of boron around oxygen plays a more dominant role than that of oxygen around boron in B 2 O 3 crystals.
… 2010, held 2-7 May …, May 1, 2010
The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive act... more The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive activity repeatedly over the last 16 years. An intense seismic and intrusive event culminated in a small basaltic fissure eruption on the eastern flanks, lasting from 20th March to 12th April. In the early morning of 14th April, a summit eruption, preceded by an intense seismic swarm, commenced at the volcano. During the first few hours activity was subglacial but a visible plume was observed at 6 AM and was followed by onset of meltwater ...
M o n o g r a p h s o f t h e D a n i s h I n s t i t u t e a t A t h e n s , V o l u m e 1 7
Scientific reports
The 39-day long eruption at the summit of Eyjafjallajökull volcano on 14 April 22 May 2010 was th... more The 39-day long eruption at the summit of Eyjafjallajökull volcano on 14 April 22 May 2010 was the first explosive eruption in Iceland for decades to send a significant amount of ash towards Europe, resulting in unprecedented disruption to air traffic. By combining ground-based, aircraft and satellite observations during the eruption, extensive tephra sampling on land in Iceland with grain size and chemical analyses, total erupted volume (and mass) and tephra distribution is determined. The eruption produced 0.27±0.08 km3 of benmorite to trachyte tephra with a dense rock equivalent (DRE) volume of 0.18±0.05 km3 (4.7±1.2 1011 kg). With modest magma discharge of 103 to 106 kg s-1 ( 2-260 m3 s-1 DRE) it supported 3-10 km high plumes that dispersed ash over ~7 million km2 in Europe and the North Atlantic. One half of the tephra volume was deposited on land with the remainder dispersed beyond the shores of Iceland. Of order 1010 kg are estimated to have been transported beyond a distance of 600-700 km from the volcano with <108 kg reaching mainland Europe. During the main explosive phases of the eruption more than 90% of the erupted material was smaller than 1000µm (1 mm) in diameter and about 50% was very fine ash (diameter <63 µm). The total amount of ash particles with diameter smaller than 30 µm, potentially capable to stay in the atmosphere for several days, is estimated to have been 1.0±0.3 1011 kg (~100 Tg), or about 20% of the total mass erupted. A fraction of this fine grained material was transported widely while a majority fell as aggregates within a few tens of kilometres of the volcano. These large proportions of very fine ash coupled with persistent northwesterly winds explain the wide dispersal of the Eyjafjallajökull ash-clouds.
![Research paper thumbnail of Characterization of ‘Balkan flint’ artefacts from Bulgaria and the Iron Gates using LA-ICP-MS and EPMA. [2010]](https://attachments.academia-assets.com/1504867/thumbnails/1.jpg)
](Characteristic of the Neolithic in Bulgaria and some neighbouring countries was the use of high q... more Characteristic of the Neolithic in Bulgaria and some neighbouring countries was the use of high quality, yellow, spotted flint, often referred to as ‘Balkan Flint’. This paper reports on the first results of research designed to test the conventional view that all ‘Balkan Flint’ from Neolithic sites in Southeast Europe was obtained from a single source or a limited number of sources on the Moesian Platform of northern Bulgaria, from where it was distributed over much of the Balkan Peninsula. The first section of the paper outlines the development of ideas about the Balkan Flint problem within the context of Bulgarian archaeology. This is followed by a summary of flint resources in Bulgaria. The final section of the paper focuses on the results of a pilot study to establish the provenance of flint from some well-known Neolithic sites, using chemical sourcing. Trace element analysis was undertaken of flint samples from 9 geological sources in northern Bulgaria and 7 Neolithic sites from Bulgaria, Romania and Serbia, using the LA-ICP-MS and EPMA methods. The results point to the following, tentative conclusions: (i) that the ‘Balkan Flint’ used by Neolithic communities across Bulgaria did not come from a single source, and (ii) that the Neolithic inhabitants of Kovačevo in southwest Bulgaria obtained their ‘Balkan Flint’ from at least two, chemically-distinct sources.
Πρακτικά 5ου Συμποσίου Ελληνικής Αρχαιομετρικής Εταιρείας, 2012
Wavelength dispersive analysis of tephra grains and melt inclusions by EPMA has been carried out ... more Wavelength dispersive analysis of tephra grains and melt inclusions by EPMA has been carried out using a focused beam of 3 µm diameter without detected loss of sodium or potassium in standard glasses, including anhydrous basalts, a slightly hydrated rhyolite and a sodium-rich intermediate composition. The ability to make analyses without chemical modification is strongly dependent upon current density at the analysis site. Analysis with narrow beams requires extremely low beam currents that are normally associated with energy dispersive analysis. Experiments indicate that a value of 0.1 nA/µm 2 must not be exceeded, at least for moderately hydrated samples, if sodium loss is to be avoided. High resolution analysis without beam-induced analytical artefacts enables fully quantitative analysis of very distal and/or highly vesicular tephras and very small melt inclusions without the need to use post-analysis corrections. This development has enabled high quality analyses from crypto-tephra layers that were previously impossible to analyse, and has removed the potential for sampling bias within mixed tephra layers by making (in most cases) tephra grains accessible for analysis. The use of focused beams also increases the level of automation, and hence the cost-effectiveness of data collection. The current data suggest limits to the applicability of the beam conditions reported, and that they may lead to alkali loss in compositions most prone to beam-induced modification such as significantly hydrated and/or sodic tephras.
8159 METEORITE. E.V. Christou, L.J. Hallis, L. Daly, I. McCarroll, M. Garbrecht, L. Jang, C.L. Ha... more 8159 METEORITE. E.V. Christou, L.J. Hallis, L. Daly, I. McCarroll, M. Garbrecht, L. Jang, C.L. Hayward, Y. Liu, J. Cairney and M.R. Lee. School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK; Centre for Microscopy & Microanalysis, University of Sydney, Sydney, Australia; School of Geosciences, Grant Institute, University of Edinburgh, Edinburgh, UK. E-mail: e.christou.1@research.gla.ac.uk
theatre architecture, as well as in the historical background to its construction. e re-foundatio... more theatre architecture, as well as in the historical background to its construction. e re-foundation of Sikyon in BC by Demetrios Poliorketes involved the city's relocation
Treatise on Geochemistry, 2014
Gold is a rare metal normally occurring in low abundances (1–5 ppb) in the Earth's crust. It ... more Gold is a rare metal normally occurring in low abundances (1–5 ppb) in the Earth's crust. It is strongly siderophilic, typically occurs in its native form or as an alloy with silver, and is chemically inert. It is nevertheless weakly soluble in the presence of a variety of complexing agents of which two – chloride and bisulfide ligands – are widely implicated in the mobilization and concentration of gold in the Earth's crust. As a result, gold deposits of varying size and economic viability are fairly common, although there is a tendency for concentrations to occur in close spatial and temporal association with major orogenic events. One auriferous sequence – the Archean-aged Witwatersrand Basin – stands out for its unique endowment and convoluted ore-forming paragenesis. The geochemistry of gold in the Witwatersrand deposits provides a number of useful insights into the nature and origin of these ores. Witwatersrand gold is enigmatic in that it exhibits variable morphologies, suggesting two modes of formation – initial fluvial deposition of flattened and overturned micronuggets derived from a heterogeneous provenance and crystalline gold precipitated from hot, metal-charged aqueous solutions. This dichotomy is responsible for contrasting ideas on Witwatersrand ore genesis that have resulted in the century-long debate between placer and hydrothermal models. Gold exhibits variable Ag and Hg contents that are distinguishable at the scale of individual goldfields and mines – systematic variations as a function of stratigraphy and burial depth are less evident. Smaller variance also occurs between gold grains at a meter to millimeter scale, with individual grains also exhibiting compositional heterogeneity at the micron scale. This pattern argues in favor of gold that was originally derived from a heterogeneous source terrane – carrying a fingerprint of its source in its chemical composition – and then substantially recrystallized by circulating basinal fluids over very limited transport distances but essentially retaining its source-area chemical traits. The localized remobilization of gold that is envisaged on the basis of gold morphological and chemical evidence is consistent with a modified placer origin for Witwatersrand ores.
Quaternary Science Reviews, 2017
Correlating tephras and cryptotephras using glass compositional analyses and numerical and statis... more Correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods: review and evaluation. Quaternary Science Reviews (
European Journal of Mineralogy, 1994
Electron microprobe analyses of a suite of four sinhalites (all of gem quality) indicate that sin... more Electron microprobe analyses of a suite of four sinhalites (all of gem quality) indicate that sinhalites (ideal formula MgAlBO 4 ) accommodate excess aluminium and small amounts of iron at the expense of magnesium. The results of structure determination and refinement, based upon single-crystal X-ray diffraction data, are in agreement with previous work. Sinhalite is isostructural with forsterite, having space group Pbnm. The cell parameters are a = 4.3320(4) A, b = 9.8819(5) A, c = 5.6813(4) A. The structure was refined to R u = 0.017, R w = 0.019 with 427 observed reflections and 41 refinable parameters. The assumed ordering scheme of [Mg 0.91 Fe 0.015 Al 0.05 □ 0.025 ] M2 Al M1 BO 4 was deduced from the microprobe analyses. Average B-O, M1-O and M2-O bond lengths are 1.499, 1.903 and 2.092 A respectively. Visible absorption spectra are indicative of extremely low Fe 3+ contents in these sinhalites, suggesting that the main substitutional mechanisms are 3Mg 2+ ↔ 2Al 3+ + □ and Mg 2+ ↔ Fe 2+ , where □ represents a vacancy
Geoarchaeology, 1996
At least 1.5 x lo6 m3 of oolitic limestone from the Corinthia was quarried during antiquity, main... more At least 1.5 x lo6 m3 of oolitic limestone from the Corinthia was quarried during antiquity, mainly for construction. Previously, it has only been possible to speculate about the sources of oolite in ancient constructions because of its uniformity on the macroscopic scale. However, thin section petrography demonstrates a considerable degree of petrographic variation within the oolite of one group of quarries a t Examilia, 4.5 krn ENE of Ancient Corinth. Variation in the characteristics of the ooids and the amount and types of noncarbonate grains in the oolite from different quarries permit the identification of five petrographically distinct zones in the Examilia quarries. This offers great potential as a high resolution provenancing tool, and the data have numerous other archaeological applications. Following these results, the work has been extended to become a comprehensive study of all Corinthian oolite quarries. 0 1996 John Wiley & Sans, Inc.
Physics and Chemistry of Minerals, Aug 1, 1997
… 2010, held 2-7 May …, May 1, 2010
The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive act... more The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive activity repeatedly over the last 16 years. An intense seismic and intrusive event culminated in a small basaltic fissure eruption on the eastern flanks, lasting from 20th March to 12th April. In the early morning of 14th April, a summit eruption, preceded by an intense seismic swarm, commenced at the volcano. During the first few hours activity was subglacial but a visible plume was observed at 6 AM and was followed by onset of meltwater ...
6 The session was organized by Maria Gurova (Bulgaria), with co-organizers Clive Bonsall (UK), Ba... more 6 The session was organized by Maria Gurova (Bulgaria), with co-organizers Clive Bonsall (UK), Barbara Voytek (USA), and Dušan Borić (Serbia/UK) sults of trace element analyses using LA-ICP-MS and EPMA techniques are discussed.
The amygdaloidal carbonatite lavas at Qasiarsuk have a primary phenocryst assemblage of calcite, ... more The amygdaloidal carbonatite lavas at Qasiarsuk have a primary phenocryst assemblage of calcite, fluor-apatite and magnetite set in a groundmass of calcite, apatite and iron oxides, and minor dolomite. Cathodoluminescence reveals a complex history, both for the major minerals which show zonal growth, and for important Nb and REE accessory phases which include pyrochlore and perovskite. The REE reside in fluor/hydrous-carbonates included exclusively in apatite. These REE minerals are similar to synthetic phases from hydrothermal experiments, but probably crystallised in equilibrium with a late-stage volatile-rich carbonate melt. Apart from low-temperature alteration, the rocks have been little disturbed since their extrusion during the earliest phase of development of the Gardar Alkaline Igneous Province.
The structure and electronic properties of trigonal and orthorhombic boric oxide (B 2 O 3) are st... more The structure and electronic properties of trigonal and orthorhombic boric oxide (B 2 O 3) are studied using periodic ab initio Hartree-Fock method. The optimised structural parameters for two B 2 O 3 polymorphs are in good agreement with experimental data. The analyses of their electronic structures provide insights into the chemical nature of the B-O bond and the way in which it changes with the coordination number around boron and oxygen. Our quantum-chemical study suggests that the orthorhombic form is more ionic than the trigonal form and that the coordination number of boron around oxygen plays a more dominant role than that of oxygen around boron in B 2 O 3 crystals.
… 2010, held 2-7 May …, May 1, 2010
The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive act... more The 1660 m high, ice-capped Eyjafjöll volcano has experienced unrest in the form of intrusive activity repeatedly over the last 16 years. An intense seismic and intrusive event culminated in a small basaltic fissure eruption on the eastern flanks, lasting from 20th March to 12th April. In the early morning of 14th April, a summit eruption, preceded by an intense seismic swarm, commenced at the volcano. During the first few hours activity was subglacial but a visible plume was observed at 6 AM and was followed by onset of meltwater ...
M o n o g r a p h s o f t h e D a n i s h I n s t i t u t e a t A t h e n s , V o l u m e 1 7
Scientific reports
The 39-day long eruption at the summit of Eyjafjallajökull volcano on 14 April 22 May 2010 was th... more The 39-day long eruption at the summit of Eyjafjallajökull volcano on 14 April 22 May 2010 was the first explosive eruption in Iceland for decades to send a significant amount of ash towards Europe, resulting in unprecedented disruption to air traffic. By combining ground-based, aircraft and satellite observations during the eruption, extensive tephra sampling on land in Iceland with grain size and chemical analyses, total erupted volume (and mass) and tephra distribution is determined. The eruption produced 0.27±0.08 km3 of benmorite to trachyte tephra with a dense rock equivalent (DRE) volume of 0.18±0.05 km3 (4.7±1.2 1011 kg). With modest magma discharge of 103 to 106 kg s-1 ( 2-260 m3 s-1 DRE) it supported 3-10 km high plumes that dispersed ash over ~7 million km2 in Europe and the North Atlantic. One half of the tephra volume was deposited on land with the remainder dispersed beyond the shores of Iceland. Of order 1010 kg are estimated to have been transported beyond a distance of 600-700 km from the volcano with <108 kg reaching mainland Europe. During the main explosive phases of the eruption more than 90% of the erupted material was smaller than 1000µm (1 mm) in diameter and about 50% was very fine ash (diameter <63 µm). The total amount of ash particles with diameter smaller than 30 µm, potentially capable to stay in the atmosphere for several days, is estimated to have been 1.0±0.3 1011 kg (~100 Tg), or about 20% of the total mass erupted. A fraction of this fine grained material was transported widely while a majority fell as aggregates within a few tens of kilometres of the volcano. These large proportions of very fine ash coupled with persistent northwesterly winds explain the wide dispersal of the Eyjafjallajökull ash-clouds.
Characteristic of the Neolithic in Bulgaria and some neighbouring countries was the use of high q... more Characteristic of the Neolithic in Bulgaria and some neighbouring countries was the use of high quality, yellow, spotted flint, often referred to as ‘Balkan Flint’. This paper reports on the first results of research designed to test the conventional view that all ‘Balkan Flint’ from Neolithic sites in Southeast Europe was obtained from a single source or a limited number of sources on the Moesian Platform of northern Bulgaria, from where it was distributed over much of the Balkan Peninsula. The first section of the paper outlines the development of ideas about the Balkan Flint problem within the context of Bulgarian archaeology. This is followed by a summary of flint resources in Bulgaria. The final section of the paper focuses on the results of a pilot study to establish the provenance of flint from some well-known Neolithic sites, using chemical sourcing. Trace element analysis was undertaken of flint samples from 9 geological sources in northern Bulgaria and 7 Neolithic sites from Bulgaria, Romania and Serbia, using the LA-ICP-MS and EPMA methods. The results point to the following, tentative conclusions: (i) that the ‘Balkan Flint’ used by Neolithic communities across Bulgaria did not come from a single source, and (ii) that the Neolithic inhabitants of Kovačevo in southwest Bulgaria obtained their ‘Balkan Flint’ from at least two, chemically-distinct sources.
Πρακτικά 5ου Συμποσίου Ελληνικής Αρχαιομετρικής Εταιρείας, 2012
Wavelength dispersive analysis of tephra grains and melt inclusions by EPMA has been carried out ... more Wavelength dispersive analysis of tephra grains and melt inclusions by EPMA has been carried out using a focused beam of 3 µm diameter without detected loss of sodium or potassium in standard glasses, including anhydrous basalts, a slightly hydrated rhyolite and a sodium-rich intermediate composition. The ability to make analyses without chemical modification is strongly dependent upon current density at the analysis site. Analysis with narrow beams requires extremely low beam currents that are normally associated with energy dispersive analysis. Experiments indicate that a value of 0.1 nA/µm 2 must not be exceeded, at least for moderately hydrated samples, if sodium loss is to be avoided. High resolution analysis without beam-induced analytical artefacts enables fully quantitative analysis of very distal and/or highly vesicular tephras and very small melt inclusions without the need to use post-analysis corrections. This development has enabled high quality analyses from crypto-tephra layers that were previously impossible to analyse, and has removed the potential for sampling bias within mixed tephra layers by making (in most cases) tephra grains accessible for analysis. The use of focused beams also increases the level of automation, and hence the cost-effectiveness of data collection. The current data suggest limits to the applicability of the beam conditions reported, and that they may lead to alkali loss in compositions most prone to beam-induced modification such as significantly hydrated and/or sodic tephras.