cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454157.v1
title: Source of the Dalradian Supergroup constrained by U–Pb dating of detrital zircon and implications for the East Laurentian margin

description: Detrital zircons in siliciclastic units of the Dalradian Supergroup yield U–Pb ages ranging from 3.2 to 0.5 Ga. Detrital zircons from the sub-Grampian Group basement and the Grampian Group are predominantly of Palaeoproterozoic and Mesoproterozoic ages with Archaean grains absent or rare. In contrast, the overlying Appin, Argyll and Southern Highland groups contain a significant contribution of Archaean detrital zircon grains, some of which locally preserve evidence for late Palaeoproterozoic overgrowths dated at <em>c</em>. 1.8 Ga. In addition, on concordia plots Archaean grains are slightly discordant with a lower intercept at <em>c</em>. 1.8 Ga suggesting they were affected by a tectonothermal event at this time. Late Palaeoproterozoic and Mesoproterozoic grains also show evidence for overprinting by a tectonothermal event around 1.0–0.9 Ga. These tectonothermal events occurred in the source region before accumulation of the siliciclastic detritus. The analysed samples contained no definitive evidence for having been affected by a late Neoproterozoic (Knoydartian) event or of containing detritus derived from a source showing evidence for this event. The overall age range of detritus, combined with sparse palaeocurrent data, is consistent with derivation from the Laurentian foreland, especially the Labrador–Greenland region. Archaean detritus overlaps with that of Archaean cratons, notably the Superior, whereas Palaeoproterozoic detritus corresponds to the timing of suturing of Archaean cratons by a series of orogenic belts (Ketilidian–Makkovik, New Quebec, Nagssugtoqidian, Torngat belts). Mesoproterozoic detritus is consistent with derivation from the Grenville Orogen. The presence of a series of detrital age peaks in the late Palaeoproterozoic and early Mesoproterozoic (1.8–1.5 Ga), the paucity of mid-Mesoproterozoic detritus (1.4–1.2 Ga), and evidence for a tectonothermal event between 1.0 and 0.9 Ga is typical of the geological history of the Labrador–Greenland region of Laurentia.
DOI: 10.6084/m9.figshare.3454154
title: A cryptic Mesoarchaean terrane in the basement to the Central African Copperbelt

description: In a study of the geochronology of the Katangan Sequence and its basement in the Central African Copperbelt, detrital and xenocrystic zircons from Muva quartzites and Katangan lapilli tuffs, were dated using the Sensitive High-Resolution Ion Microprobe (SHRIMP). A detrital population (dated between 3007 and 3031 Ma) and a group of xenocrystic zircons aged between 3169 and 3225 Ma provide the first evidence for the existence of a Mesoarchaean basement beneath the Central African Copperbelt.
DOI: 10.6084/m9.figshare.3454154.v1
title: A cryptic Mesoarchaean terrane in the basement to the Central African Copperbelt

description: In a study of the geochronology of the Katangan Sequence and its basement in the Central African Copperbelt, detrital and xenocrystic zircons from Muva quartzites and Katangan lapilli tuffs, were dated using the Sensitive High-Resolution Ion Microprobe (SHRIMP). A detrital population (dated between 3007 and 3031 Ma) and a group of xenocrystic zircons aged between 3169 and 3225 Ma provide the first evidence for the existence of a Mesoarchaean basement beneath the Central African Copperbelt.
DOI: 10.6084/m9.figshare.3454151
title: Application of portable XRF to the direct analysis of till samples from various deposit types in Canada

description: In this study, results by direct portable XRF (‘pXRF’) on unsieved till samples were compared with those by established laboratory methods (aqua regia or fusion ICP-MS and ICP-ES) on the &lt;0.063-mm fraction to determine if the application of direct pXRF in the field would serve as an acceptable guide for immediate follow-up work. Four test sites in Canada were chosen: the Halfmile Lake Cu-Pb-Zn VMS deposit; the intrusion-hosted W-Mo Sisson deposit; a Pb-Zn Mississippi Valley–type (MVT) deposit in the Pine Point district; and the Triple B kimberlite. Unsieved till samples from the GSC archive collection were used for this study and included samples from background areas, immediately overlying, and at various distances down-ice of each deposit. Ziploc® and Whirl-Pak® bags that were used to contain the samples in the field were tested for their properties of X-ray attenuation and contamination. In general, the performance of pXRF in the four test areas was very good where concentrations of elements of interest (indicator or pathfinder elements) were substantially above detection limits by this technique (in the low ppm range for many elements). The following elements, shown to be useful indicator elements (important constituents of the ore/commodity) or pathfinder elements (those associated with the commodity elements) by the established methodology, showed similar patterns by pXRF on the unsieved material: Zn, Cu, Pb, and As at Halfmile Lake; W, Mo, Cu, Zn, Pb, and As at the Sisson deposit; Zn, Pb, and Fe at Pine Point; and Ca, Sr, Cr, and Ni at Triple B. Pathfinder elements whose concentrations were too low for determination by pXRF include: Ag and Sb at Halfmile Lake; Ag and Cd at Sisson; Cd, S, and Se at Pine Point; and Co, Mg, P, U, and Th at Triple B. The high background for Bi by pXRF, equivalent to <em>c</em>. 50 ppm, and its noisy signal precluded its use at Halfmile Lake and Sisson. Elements which tended to show poor precision (three analyses each sample) by pXRF in some samples due to sample heterogeneity include Sn, V, and W. Mercury was erroneously reported for the majority of samples in the low ppm range by pXRF whereas its concentration in fact was in the low ppb range. Several Pb-, Zn- (<em>c</em>. 1% Pb, Zn) and Fe-rich (up to 16% Fe) samples demonstrated spectral interferences by: Pb on As, Th and Se; Zn on Cu; and Fe on Co. Results for six till samples analysed in Ziploc® and Whirl-Pak® bags showed that Ziploc® absorbs fewer low-energy photons and hence is preferable for determining light elements such as Si, K and Ca.
DOI: 10.6084/m9.figshare.3454151.v1
title: Application of portable XRF to the direct analysis of till samples from various deposit types in Canada

description: In this study, results by direct portable XRF (‘pXRF’) on unsieved till samples were compared with those by established laboratory methods (aqua regia or fusion ICP-MS and ICP-ES) on the &lt;0.063-mm fraction to determine if the application of direct pXRF in the field would serve as an acceptable guide for immediate follow-up work. Four test sites in Canada were chosen: the Halfmile Lake Cu-Pb-Zn VMS deposit; the intrusion-hosted W-Mo Sisson deposit; a Pb-Zn Mississippi Valley–type (MVT) deposit in the Pine Point district; and the Triple B kimberlite. Unsieved till samples from the GSC archive collection were used for this study and included samples from background areas, immediately overlying, and at various distances down-ice of each deposit. Ziploc® and Whirl-Pak® bags that were used to contain the samples in the field were tested for their properties of X-ray attenuation and contamination. In general, the performance of pXRF in the four test areas was very good where concentrations of elements of interest (indicator or pathfinder elements) were substantially above detection limits by this technique (in the low ppm range for many elements). The following elements, shown to be useful indicator elements (important constituents of the ore/commodity) or pathfinder elements (those associated with the commodity elements) by the established methodology, showed similar patterns by pXRF on the unsieved material: Zn, Cu, Pb, and As at Halfmile Lake; W, Mo, Cu, Zn, Pb, and As at the Sisson deposit; Zn, Pb, and Fe at Pine Point; and Ca, Sr, Cr, and Ni at Triple B. Pathfinder elements whose concentrations were too low for determination by pXRF include: Ag and Sb at Halfmile Lake; Ag and Cd at Sisson; Cd, S, and Se at Pine Point; and Co, Mg, P, U, and Th at Triple B. The high background for Bi by pXRF, equivalent to <em>c</em>. 50 ppm, and its noisy signal precluded its use at Halfmile Lake and Sisson. Elements which tended to show poor precision (three analyses each sample) by pXRF in some samples due to sample heterogeneity include Sn, V, and W. Mercury was erroneously reported for the majority of samples in the low ppm range by pXRF whereas its concentration in fact was in the low ppb range. Several Pb-, Zn- (<em>c</em>. 1% Pb, Zn) and Fe-rich (up to 16% Fe) samples demonstrated spectral interferences by: Pb on As, Th and Se; Zn on Cu; and Fe on Co. Results for six till samples analysed in Ziploc® and Whirl-Pak® bags showed that Ziploc® absorbs fewer low-energy photons and hence is preferable for determining light elements such as Si, K and Ca.
DOI: 10.6084/m9.figshare.3454145
title: Petrogenesis and tectonomagmatic significance of Eocene mafic intrusions from the Neotethyan suture zone in the Muslim Bagh–Khanozai region, Pakistan

description: New geochemical data for mafic intrusions within the Eocene Nisai Formation along the suture zone between the Indian and Eurasian plates are used to constrain their petrogenesis and assess the local tectonics and mantle dynamics. Petrological and geochemical data indicate that these alkalic intrusions have moderately enriched incompatible trace element compositions similar to ocean island basalt magmatism. Modelling suggests that these intrusions are the result of 1–5% melting of a deep, enriched, predominantly garnet lherzolite, with a small amount of subduction-derived fluids. These melts then underwent fractional crystallization at lithospheric depths of <em>c</em>. 30 km. <strong>Supplementary materials:</strong> Detailed information on each analysed sample including field notes and latitude and longitude, replicate analysis of standards, and fractional crystallization modelling are available at http://www.geolsoc.org.uk/SUP18893.
DOI: 10.6084/m9.figshare.3454145.v1
title: Petrogenesis and tectonomagmatic significance of Eocene mafic intrusions from the Neotethyan suture zone in the Muslim Bagh–Khanozai region, Pakistan

description: New geochemical data for mafic intrusions within the Eocene Nisai Formation along the suture zone between the Indian and Eurasian plates are used to constrain their petrogenesis and assess the local tectonics and mantle dynamics. Petrological and geochemical data indicate that these alkalic intrusions have moderately enriched incompatible trace element compositions similar to ocean island basalt magmatism. Modelling suggests that these intrusions are the result of 1–5% melting of a deep, enriched, predominantly garnet lherzolite, with a small amount of subduction-derived fluids. These melts then underwent fractional crystallization at lithospheric depths of <em>c</em>. 30 km. <strong>Supplementary materials:</strong> Detailed information on each analysed sample including field notes and latitude and longitude, replicate analysis of standards, and fractional crystallization modelling are available at http://www.geolsoc.org.uk/SUP18893.
DOI: 10.6084/m9.figshare.3454142
title: Anomalous terrain at Dove Crags ‘cirqueform’ and Gasgale Gill asymmetric valley, English Lake District, attributed to large-scale rock slope failure of pre-LGM origins

description: An unusually bold, cirque-like cavity, above a small, apparently fluvial side valley rich in landscape anomalies, is evaluated as a large-scale (<em>c</em>. 1 km<sup>2</sup>) rock slope failure (RSF) with possible pre-Last Glacial Maximum (LGM) origins. Although the failed mass is much subdued, field evidence includes dry gullies and a tarnless hollow; a sharp flank scarp and a high cutbank toe suggest reactivation. Indirect support is provided by a pioneering (in Britain) schematic reconstruction of a whole-valley pre-RSF landscape, employing a ‘clone-stamping’ procedure, which resolves the main terrain anomalies. The RSF interpretation is satisfactorily tested by: (1) compatible proxy cavity and slipmass volumes of 35 and 25 million m<sup>3</sup> respectively, with the deficit attributed to trimming by an LGM valley glacier; (2) comparisons with other RSFs by area, cavity parameters, and a total extant volume (derived from an inferred balanced long section) of <em>c</em>. 50 million m<sup>3</sup>; and (3) a proposed ‘zone of crush’ model that allows a large failed mass, <em>c</em>. 100–200 m thick, to descend incrementally by <em>c</em>. 300 m without disintegrating. A landscape paradox is identified whereby the valley now has an asymmetric, quasi-fluvial profile, with till covering the slope below the cirqueform cavity, yet is inferred to have had a pre-RSF glacial form and an LGM glacier. This is resolved by envisaging: (a) that a pre-LGM RSF created a cavity that was exploited by cirque glaciers on at least two occasions; (b) that the RSF was pared back by an LGM valley glacier; and (c) that it subsequently re-descended to the valley floor after the LGM. A pre-LGM origin for the RSF would account for the till-covered slipmass. It also allows time for excavation of the present cirque headwall by 50–100 m, and for the opposite valleyside to erode back by <em>c</em>. 50 m in response to a progressively displacing river and valley glacier. If this proposition is correct, Dove Crags would be one of the first substantial pre-LGM RSFs to be recognized in the glaciated mountains of Britain and Ireland, implying that others ought to be present.
DOI: 10.6084/m9.figshare.3454142.v1
title: Anomalous terrain at Dove Crags ‘cirqueform’ and Gasgale Gill asymmetric valley, English Lake District, attributed to large-scale rock slope failure of pre-LGM origins

description: An unusually bold, cirque-like cavity, above a small, apparently fluvial side valley rich in landscape anomalies, is evaluated as a large-scale (<em>c</em>. 1 km<sup>2</sup>) rock slope failure (RSF) with possible pre-Last Glacial Maximum (LGM) origins. Although the failed mass is much subdued, field evidence includes dry gullies and a tarnless hollow; a sharp flank scarp and a high cutbank toe suggest reactivation. Indirect support is provided by a pioneering (in Britain) schematic reconstruction of a whole-valley pre-RSF landscape, employing a ‘clone-stamping’ procedure, which resolves the main terrain anomalies. The RSF interpretation is satisfactorily tested by: (1) compatible proxy cavity and slipmass volumes of 35 and 25 million m<sup>3</sup> respectively, with the deficit attributed to trimming by an LGM valley glacier; (2) comparisons with other RSFs by area, cavity parameters, and a total extant volume (derived from an inferred balanced long section) of <em>c</em>. 50 million m<sup>3</sup>; and (3) a proposed ‘zone of crush’ model that allows a large failed mass, <em>c</em>. 100–200 m thick, to descend incrementally by <em>c</em>. 300 m without disintegrating. A landscape paradox is identified whereby the valley now has an asymmetric, quasi-fluvial profile, with till covering the slope below the cirqueform cavity, yet is inferred to have had a pre-RSF glacial form and an LGM glacier. This is resolved by envisaging: (a) that a pre-LGM RSF created a cavity that was exploited by cirque glaciers on at least two occasions; (b) that the RSF was pared back by an LGM valley glacier; and (c) that it subsequently re-descended to the valley floor after the LGM. A pre-LGM origin for the RSF would account for the till-covered slipmass. It also allows time for excavation of the present cirque headwall by 50–100 m, and for the opposite valleyside to erode back by <em>c</em>. 50 m in response to a progressively displacing river and valley glacier. If this proposition is correct, Dove Crags would be one of the first substantial pre-LGM RSFs to be recognized in the glaciated mountains of Britain and Ireland, implying that others ought to be present.
DOI: 10.6084/m9.figshare.3454139
title: Simulating maar–diatreme volcanic systems in bench-scale experiments

description: Maar–diatreme eruptions are incompletely understood, and explanations for the processes involved in them have been debated for decades. This study extends bench-scale analogue experiments previously conducted on maar–diatreme systems and attempts to scale the results up to both field-scale experimentation and natural volcanic systems to produce a reconstructive toolkit for maar volcanoes. These experimental runs produced via multiple mechanisms complex deposits that match many features seen in natural maar–diatreme deposits. The runs include deeper single blasts, series of descending discrete blasts, and series of ascending blasts. Debris-jet inception and diatreme formation are indicated by this study to involve multiple types of granular fountains within diatreme deposits produced under varying initial conditions. It is not possible to infer the energies of single blasts in multiple-blast series from the final deposits. The depositional record of blast sequences can be ascertained from the proportion of fallback sedimentation versus maar ejecta rim material, the final crater size and the degree of overturning or slumping of accessory strata. Quantitatively, deeper blasts involve a roughly equal partitioning of energy into crater excavation energy versus mass movement of juvenile material, whereas shallower blasts expend a much greater proportion of energy in crater excavation.
DOI: 10.6084/m9.figshare.3454139.v1
title: Simulating maar–diatreme volcanic systems in bench-scale experiments

description: Maar–diatreme eruptions are incompletely understood, and explanations for the processes involved in them have been debated for decades. This study extends bench-scale analogue experiments previously conducted on maar–diatreme systems and attempts to scale the results up to both field-scale experimentation and natural volcanic systems to produce a reconstructive toolkit for maar volcanoes. These experimental runs produced via multiple mechanisms complex deposits that match many features seen in natural maar–diatreme deposits. The runs include deeper single blasts, series of descending discrete blasts, and series of ascending blasts. Debris-jet inception and diatreme formation are indicated by this study to involve multiple types of granular fountains within diatreme deposits produced under varying initial conditions. It is not possible to infer the energies of single blasts in multiple-blast series from the final deposits. The depositional record of blast sequences can be ascertained from the proportion of fallback sedimentation versus maar ejecta rim material, the final crater size and the degree of overturning or slumping of accessory strata. Quantitatively, deeper blasts involve a roughly equal partitioning of energy into crater excavation energy versus mass movement of juvenile material, whereas shallower blasts expend a much greater proportion of energy in crater excavation.
DOI: 10.6084/m9.figshare.3454133
title: Frontier exploration and the North Atlantic Igneous Province: new insights from a 2.6 km offshore volcanic sequence in the NE Faroe–Shetland Basin

description: The Lagavulin exploration well 217/15-1Z penetrated a <em>c</em>. 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene–Eocene boundary in the NE Faroe–Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene–Eocene boundary. Basalts from the lower <em>c</em>. 1.3 km have low TiO<sub>2</sub> (&lt;1.5 wt%) and low Zr/Y (2–3), with olivine-phyric picrites towards the base (Mg# 70–82; olivine Fo<sub>85–91</sub>). The hiatus correlates precisely with a change to high-TiO<sub>2</sub> (2.5–3.2 wt%), high-Zr/Y (&gt;4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area.
DOI: 10.6084/m9.figshare.3454133.v1
title: Frontier exploration and the North Atlantic Igneous Province: new insights from a 2.6 km offshore volcanic sequence in the NE Faroe–Shetland Basin

description: The Lagavulin exploration well 217/15-1Z penetrated a <em>c</em>. 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene–Eocene boundary in the NE Faroe–Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene–Eocene boundary. Basalts from the lower <em>c</em>. 1.3 km have low TiO<sub>2</sub> (&lt;1.5 wt%) and low Zr/Y (2–3), with olivine-phyric picrites towards the base (Mg# 70–82; olivine Fo<sub>85–91</sub>). The hiatus correlates precisely with a change to high-TiO<sub>2</sub> (2.5–3.2 wt%), high-Zr/Y (&gt;4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area.
DOI: 10.6084/m9.figshare.3454130
title: Evidence from Rb–Sr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland

description: Shetland occupies a unique central location within the North Atlantic Caledonides. Thirty-three new high-precision Rb–Sr mineral ages indicate a polyorogenic history. Ages of 723–702 Ma obtained from the vicinity of the Wester Keolka Shear Zone indicate a Neoproterozoic (Knoydartian) age and preclude its correlation with the Silurian Moine Thrust. Ordovician ages of <em>c</em>. 480–443 Ma obtained from the Yell Sound Group and the East Mainland Succession constrain deformation fabrics and metamorphic assemblages to have formed during Grampian accretionary orogenic events, broadly contemporaneously with orogenesis of the Dalradian Supergroup in Ireland and mainland Scotland. The relative paucity of Silurian ages is attributed to a likely location at a high structural level in the Scandian nappe pile relative to mainland Scotland. Ages of <em>c</em>. 416 and <em>c</em>. 411 Ma for the Uyea Shear Zone suggest a late orogenic evolution that has more in common with East Greenland and Norway than with northern mainland Scotland. <strong>Supplementary material:</strong> Detailed appraisal of biotite petrography is available at http://www.geolsoc.org.uk/SUP18887.