cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453296
title: Building Bayesian networks from basin-modelling scenarios for improved geological decision making

description: Basin models are used to gain insights about a petroleum system, and to simulate geological processes required to form oil and gas accumulations. The focus of such simulations is usually on charge and timing-related issues, although uncertainty analysis about a wider range of parameters is becoming more common. Bayesian networks (BNs) are useful for decision making in geological prospect analysis and exploration. In this paper we propose a framework for merging these two methodologies: by doing so, we explicitly account for dependencies between the geological elements. The probabilistic description of the BN is trained by using multiple scenarios of Basin and Petroleum Systems Modelling (BPSM). A range of different input parameters are used for total organic content, heat flow, porosity and faulting to span a full categorical design for the BPSM scenarios. Given the consistent BN for trap, reservoir and source attributes, we demonstrate important decision-making applications, such as evidence propagation and the value of information. <strong>Supplementary material:</strong> Tables and figures of analyses and data are available at: www.geolsoc.org.uk/SUP18607.
DOI: 10.6084/m9.figshare.3453296.v1
title: Building Bayesian networks from basin-modelling scenarios for improved geological decision making

description: Basin models are used to gain insights about a petroleum system, and to simulate geological processes required to form oil and gas accumulations. The focus of such simulations is usually on charge and timing-related issues, although uncertainty analysis about a wider range of parameters is becoming more common. Bayesian networks (BNs) are useful for decision making in geological prospect analysis and exploration. In this paper we propose a framework for merging these two methodologies: by doing so, we explicitly account for dependencies between the geological elements. The probabilistic description of the BN is trained by using multiple scenarios of Basin and Petroleum Systems Modelling (BPSM). A range of different input parameters are used for total organic content, heat flow, porosity and faulting to span a full categorical design for the BPSM scenarios. Given the consistent BN for trap, reservoir and source attributes, we demonstrate important decision-making applications, such as evidence propagation and the value of information. <strong>Supplementary material:</strong> Tables and figures of analyses and data are available at: www.geolsoc.org.uk/SUP18607.
DOI: 10.6084/m9.figshare.3453290
title: Metamorphic zircon: tracking fluid pathways and the implications for the preservation of detrital zircon

description: Zircon in greenschist-facies Dalradian metasedimentary rocks of Scotland is characterized by two types: large detrital grains and small euhedral metamorphic grains. The former are concentrated in psammites and contain abundant evidence of dissolution and reaction with metamorphic fluids. The smallest metamorphic microzircons (&lt;9 µm<sup>2</sup>) represent &gt;65% of zircon grains, are clustered within pelites and form in aligned arrays that cut across the bedding. The combination of textural characteristics with the spatial distribution shows that the growth of microzircon occurred in a small-scale crack network that developed after folding, reflecting precipitation from locally derived metamorphic fluids. Zircons within psammites in the hinge of an antiform show an enhanced metamorphic response suggesting focusing of fluids by the fold. Metamorphic zircon may be successfully used to map detailed fluid pathways, providing a unique approach to monitoring permeability structure in the crust. The scarcity of unmodified detrital zircon, which forms &lt;7% of larger grains, indicates that major biases in the preservation potential of zircon are generated during metamorphism. These biases may feed through into the U–Pb ages of detrital zircons that are analysed from metamorphic rocks and hence into models of crustal evolution.
DOI: 10.6084/m9.figshare.3453290.v1
title: Metamorphic zircon: tracking fluid pathways and the implications for the preservation of detrital zircon

description: Zircon in greenschist-facies Dalradian metasedimentary rocks of Scotland is characterized by two types: large detrital grains and small euhedral metamorphic grains. The former are concentrated in psammites and contain abundant evidence of dissolution and reaction with metamorphic fluids. The smallest metamorphic microzircons (&lt;9 µm<sup>2</sup>) represent &gt;65% of zircon grains, are clustered within pelites and form in aligned arrays that cut across the bedding. The combination of textural characteristics with the spatial distribution shows that the growth of microzircon occurred in a small-scale crack network that developed after folding, reflecting precipitation from locally derived metamorphic fluids. Zircons within psammites in the hinge of an antiform show an enhanced metamorphic response suggesting focusing of fluids by the fold. Metamorphic zircon may be successfully used to map detailed fluid pathways, providing a unique approach to monitoring permeability structure in the crust. The scarcity of unmodified detrital zircon, which forms &lt;7% of larger grains, indicates that major biases in the preservation potential of zircon are generated during metamorphism. These biases may feed through into the U–Pb ages of detrital zircons that are analysed from metamorphic rocks and hence into models of crustal evolution.
DOI: 10.6084/m9.figshare.3453287
title: Open-system processes in the differentiation of mafic magma in the Teide–Pico Viejo succession, Tenerife

description: Oceanic island basalts are commonly thought to differentiate by fractional crystallization, yet closed-system fractionation models have so far failed to reproduce major and trace element variations observed in mafic lavas from the Teide–Pico Viejo stratovolcano complex on Tenerife. Here, new high-precision plagioclase trace element data are fed into such a fractionation model. The results confirm that fractionation of phenocrysts found in the lavas does not reproduce trace element variations, in particular enrichment of Sr and Zr observed in the Teide–Pico Viejo mafic suite. This enrichment of Sr and Zr is tested by an energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC) model at high <em>T</em> and low Δ<em>T</em> intervals, consistent with previously determined magma storage beneath Tenerife at sub-Moho depths. Published mineral–melt equilibrium relations using the plagioclase anorthite content (0.4 &lt; <em>X</em><sub>An</sub> &lt; 0.8) constrain the temperature during differentiation. Gabbroic xenoliths found in Tenerife lavas are assumed as contaminant. Enrichment of Sr and Zr in the Teide mafic suite is reproduced by this combined assimilation and fractional crystallization model, as assimilation causes higher degrees of enrichment in incompatible trace elements than is possible by crystal fractionation alone. Recycling of plutonic roots may thus have significantly enriched trace elements in the primitive lavas of the Teide–Pico Viejo succession.
DOI: 10.6084/m9.figshare.3453287.v1
title: Open-system processes in the differentiation of mafic magma in the Teide–Pico Viejo succession, Tenerife

description: Oceanic island basalts are commonly thought to differentiate by fractional crystallization, yet closed-system fractionation models have so far failed to reproduce major and trace element variations observed in mafic lavas from the Teide–Pico Viejo stratovolcano complex on Tenerife. Here, new high-precision plagioclase trace element data are fed into such a fractionation model. The results confirm that fractionation of phenocrysts found in the lavas does not reproduce trace element variations, in particular enrichment of Sr and Zr observed in the Teide–Pico Viejo mafic suite. This enrichment of Sr and Zr is tested by an energy-constrained recharge, assimilation and fractional crystallization (EC-RAFC) model at high <em>T</em> and low Δ<em>T</em> intervals, consistent with previously determined magma storage beneath Tenerife at sub-Moho depths. Published mineral–melt equilibrium relations using the plagioclase anorthite content (0.4 &lt; <em>X</em><sub>An</sub> &lt; 0.8) constrain the temperature during differentiation. Gabbroic xenoliths found in Tenerife lavas are assumed as contaminant. Enrichment of Sr and Zr in the Teide mafic suite is reproduced by this combined assimilation and fractional crystallization model, as assimilation causes higher degrees of enrichment in incompatible trace elements than is possible by crystal fractionation alone. Recycling of plutonic roots may thus have significantly enriched trace elements in the primitive lavas of the Teide–Pico Viejo succession.
DOI: 10.6084/m9.figshare.3453284
title: Persistent long-term (<em>c.</em> 24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

description: To address Miocene–present episodic v. persistent exhumation, we utilize a simple graphical procedure that vertically stacks spatially diverse K-feldspar <sup>40</sup>Ar/<sup>39</sup>Ar multi-domain diffusion (MDD) models from the length of the approximately 100 km-long high-peak region of the Eastern Alaska Range. We supply additional constraints with <sup>40</sup>Ar/<sup>39</sup>Ar mica dating because the higher closure-temperature-window places limits on the initiation of rapid Eastern Alaska Range exhumation. We also provide a broad <sup>40</sup>Ar/<sup>39</sup>Ar K-feldspar minimum closure age data set to add more detail on spatial patterns in the regional exhumation history for the Eastern Alaska Range. We find that rapid and persistent exhumation has occurred in the Eastern Alaska Range since about 24 Ma at a long-term rate of approximately 0.9 km/Ma, but that this rapid exhumation is spatially variable through time. Onset of rapid Eastern Alaska Range exhumation is coincident with the initiation of rapid exhumation in SW Alaska, the Western Alaska Range and the Chugach–Saint Elias Range at around 25 Ma, implying a region-wide deformational response to a change in tectonic forcing. The initiation of highly coupled flat-slab subduction of the Yakutat microplate is probably responsible for this prolonged period of rapid exhumation in southern Alaska.
DOI: 10.6084/m9.figshare.3453284.v1
title: Persistent long-term (<em>c.</em> 24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

description: To address Miocene–present episodic v. persistent exhumation, we utilize a simple graphical procedure that vertically stacks spatially diverse K-feldspar <sup>40</sup>Ar/<sup>39</sup>Ar multi-domain diffusion (MDD) models from the length of the approximately 100 km-long high-peak region of the Eastern Alaska Range. We supply additional constraints with <sup>40</sup>Ar/<sup>39</sup>Ar mica dating because the higher closure-temperature-window places limits on the initiation of rapid Eastern Alaska Range exhumation. We also provide a broad <sup>40</sup>Ar/<sup>39</sup>Ar K-feldspar minimum closure age data set to add more detail on spatial patterns in the regional exhumation history for the Eastern Alaska Range. We find that rapid and persistent exhumation has occurred in the Eastern Alaska Range since about 24 Ma at a long-term rate of approximately 0.9 km/Ma, but that this rapid exhumation is spatially variable through time. Onset of rapid Eastern Alaska Range exhumation is coincident with the initiation of rapid exhumation in SW Alaska, the Western Alaska Range and the Chugach–Saint Elias Range at around 25 Ma, implying a region-wide deformational response to a change in tectonic forcing. The initiation of highly coupled flat-slab subduction of the Yakutat microplate is probably responsible for this prolonged period of rapid exhumation in southern Alaska.
DOI: 10.6084/m9.figshare.3453281
title: A laser probe <sup>40</sup>Ar/<sup>39</sup>Ar investigation of poikilitic shergottite NWA 4797: implications for the timing of shock metamorphism

description: Spatially resolved argon isotope measurements have been performed on neutron-irradiated samples of NW Africa (NWA) 4797. Shock heating of NWA 4797 completely melted and vesiculated precursor igneous plagioclase, which cooled to an assemblage of plagioclase crystals with interstitial glasses of variable composition (Ca/K ratios). Using a focused ultraviolet laser beam, is has been possible to distinguish between argon isotopic signatures from groundmass minerals (igneous olivine + pyroxene), plagioclase and a shock vein. This study focuses on the potential for this meteorite to shed light on shock ages of shergottites. Apparent <sup>40</sup>Ar/<sup>39</sup>Ar ages of groundmass minerals show that there are large amounts of excess argon in this phase, yielding a wide range of calculated ages from 690 ± 30 Ma to several apparent ages older than 4.5 Ga. A traverse of laser-probe extractions across the 1 mm-diameter shock vein in NWA 4797 yielded apparent <sup>40</sup>Ar/<sup>39</sup>Ar ages younger than the groundmass. A signature of the Martian atmosphere, identified by <sup>40</sup>Ar/<sup>36</sup>Ar ratios of 1600–1900, was not found in the NWA 4797 shock vein. This is distinct from other shergottites where the products of shock melting contain a nearly pure sample of Martian atmosphere. We attribute this to a distinct formation mechanism, and hence gas-trapping mechanism, of the NWA 4797 shock vein. We undertook 44 analyses of plagioclase areas identified by SEM analysis. Ages ranged from 45 ± 27 to 3771 ± 109 Ma and yield an average age of 375 ± 77 Ma, considerably younger than ages obtained in this study from either the groundmass or the shock vein. A plot of age v. <sup>37</sup>Ar/<sup>39</sup>Ar for plagioclase showed a continuum of ages from the oldest to youngest ages measured. Older ages are correlated with higher Ca/K ratios of plagioclase, indicating contamination from groundmass minerals rich in excess argon. The youngest ages correlate to plagioclase extractions with the lowest Ca/K ratios, interpreted to have crystallized from a nearly pure plagioclase melt with contributions from a K-rich mesostasis. We see no evidence for multiple shock events in NWA 4797. Rather, we favour the interpretation that the cosmic-ray exposure (CRE) age of 3.0±0.5 Ma, obtained on NWA 4797 in this study using cosmogenic <sup>38</sup>Ar, approximates the timing of shock melting in this meteorite.
DOI: 10.6084/m9.figshare.3453281.v1
title: A laser probe <sup>40</sup>Ar/<sup>39</sup>Ar investigation of poikilitic shergottite NWA 4797: implications for the timing of shock metamorphism

description: Spatially resolved argon isotope measurements have been performed on neutron-irradiated samples of NW Africa (NWA) 4797. Shock heating of NWA 4797 completely melted and vesiculated precursor igneous plagioclase, which cooled to an assemblage of plagioclase crystals with interstitial glasses of variable composition (Ca/K ratios). Using a focused ultraviolet laser beam, is has been possible to distinguish between argon isotopic signatures from groundmass minerals (igneous olivine + pyroxene), plagioclase and a shock vein. This study focuses on the potential for this meteorite to shed light on shock ages of shergottites. Apparent <sup>40</sup>Ar/<sup>39</sup>Ar ages of groundmass minerals show that there are large amounts of excess argon in this phase, yielding a wide range of calculated ages from 690 ± 30 Ma to several apparent ages older than 4.5 Ga. A traverse of laser-probe extractions across the 1 mm-diameter shock vein in NWA 4797 yielded apparent <sup>40</sup>Ar/<sup>39</sup>Ar ages younger than the groundmass. A signature of the Martian atmosphere, identified by <sup>40</sup>Ar/<sup>36</sup>Ar ratios of 1600–1900, was not found in the NWA 4797 shock vein. This is distinct from other shergottites where the products of shock melting contain a nearly pure sample of Martian atmosphere. We attribute this to a distinct formation mechanism, and hence gas-trapping mechanism, of the NWA 4797 shock vein. We undertook 44 analyses of plagioclase areas identified by SEM analysis. Ages ranged from 45 ± 27 to 3771 ± 109 Ma and yield an average age of 375 ± 77 Ma, considerably younger than ages obtained in this study from either the groundmass or the shock vein. A plot of age v. <sup>37</sup>Ar/<sup>39</sup>Ar for plagioclase showed a continuum of ages from the oldest to youngest ages measured. Older ages are correlated with higher Ca/K ratios of plagioclase, indicating contamination from groundmass minerals rich in excess argon. The youngest ages correlate to plagioclase extractions with the lowest Ca/K ratios, interpreted to have crystallized from a nearly pure plagioclase melt with contributions from a K-rich mesostasis. We see no evidence for multiple shock events in NWA 4797. Rather, we favour the interpretation that the cosmic-ray exposure (CRE) age of 3.0±0.5 Ma, obtained on NWA 4797 in this study using cosmogenic <sup>38</sup>Ar, approximates the timing of shock melting in this meteorite.
DOI: 10.6084/m9.figshare.3453275
title: A U–Pb age for the Late Caledonian Sperrin Mountains minor intrusions suite in the north of Ireland: timing of slab break-off in the Grampian terrane and the significance of deep-seated, crustal lineaments

description: An intrusion of trachy-andesite, representative of a newly discovered suite of high-K–Ba–Sr, calc-alkaline minor intrusions (termed herein the Sperrin Mountains suite), hosted within the Grampian terrane in the north of Ireland, has been dated by U–Pb zircon at 426.69 ± 0.85 Ma (mid-Silurian; Wenlock–Ludlow boundary). Geochemistry reveals a close association with the Fanad, Ardara and Thorr plutons of the Donegal Batholith and the Argyll and Northern Highlands Suite of Scotland. The deep-seated Omagh Lineament appears to have limited eastward propagation of the Sperrin Mountains suite from beneath the main centre of granitic magmatism in Donegal. A Hf depleted mantle model age (T<sub>DM</sub>Hf) of <em>c</em>. 800 Ma for trachy-andesite zircons indicates partial melting from a source previously separated from the mantle. Whole-rock geochemistry of the suite is consistent with a model of partial melting, triggered by slab break-off, following thrusting of Ganderia–Avalonia under the Southern Uplands–Down–Longford accretionary prism (i.e. Laurentian margin). The new age constrains the timing of this event in the north of Ireland and is consistent with the petrogenesis of Late Caledonian high-K granites, appinites and minor intrusions across the Caledonides of northern Britain and Ireland.
DOI: 10.6084/m9.figshare.3453275.v1
title: A U–Pb age for the Late Caledonian Sperrin Mountains minor intrusions suite in the north of Ireland: timing of slab break-off in the Grampian terrane and the significance of deep-seated, crustal lineaments

description: An intrusion of trachy-andesite, representative of a newly discovered suite of high-K–Ba–Sr, calc-alkaline minor intrusions (termed herein the Sperrin Mountains suite), hosted within the Grampian terrane in the north of Ireland, has been dated by U–Pb zircon at 426.69 ± 0.85 Ma (mid-Silurian; Wenlock–Ludlow boundary). Geochemistry reveals a close association with the Fanad, Ardara and Thorr plutons of the Donegal Batholith and the Argyll and Northern Highlands Suite of Scotland. The deep-seated Omagh Lineament appears to have limited eastward propagation of the Sperrin Mountains suite from beneath the main centre of granitic magmatism in Donegal. A Hf depleted mantle model age (T<sub>DM</sub>Hf) of <em>c</em>. 800 Ma for trachy-andesite zircons indicates partial melting from a source previously separated from the mantle. Whole-rock geochemistry of the suite is consistent with a model of partial melting, triggered by slab break-off, following thrusting of Ganderia–Avalonia under the Southern Uplands–Down–Longford accretionary prism (i.e. Laurentian margin). The new age constrains the timing of this event in the north of Ireland and is consistent with the petrogenesis of Late Caledonian high-K granites, appinites and minor intrusions across the Caledonides of northern Britain and Ireland.
DOI: 10.6084/m9.figshare.3453272
title: Taxonomic diversity of Eocene Antarctic penguins: a changing picture

description: Eocene Antarctic penguins, at least 10 species in six genera, are known only from the La Meseta Formation, Seymour Island, Antarctic Peninsula. They are most numerous (in terms of individuals, body sizes and taxa) in Late Eocene strata. Specimens from three species and phylogenetic analysis presented in this work shed new light on the systematics and evolution of Antarctic Sphenisciformes. The earliest reported bones of giant penguins from the genus <em>Anthropornis</em> set the conservative estimate of its divergence time at <em>c</em>. 53 Ma (Early Eocene). They also document the oldest known appearance of quite a high diversity of Sphenisciformes; altogether, three morphotypes (differing in size) have been found within the same sampling locality. A newly described, relatively small and intriguingly elongated, tarsometatarsus from the Late Eocene of the La Meseta Formation, belonging to another genus of large-sized Antarctic penguins (<em>Palaeeudyptes</em>), suggests the possible existence of an unnamed species within this long-established genus. The phylogenetic analysis based on tarsometatarsal features shows that the relationship between ‘<em>Archaeospheniscus</em>’ <em>wimani</em> and three species of <em>Delphinornis</em> (all of them co-existed during the Late Eocene time period) does not appear to be close enough to justify merging them into a single genus (as was recently postulated).
DOI: 10.6084/m9.figshare.3453272.v1
title: Taxonomic diversity of Eocene Antarctic penguins: a changing picture

description: Eocene Antarctic penguins, at least 10 species in six genera, are known only from the La Meseta Formation, Seymour Island, Antarctic Peninsula. They are most numerous (in terms of individuals, body sizes and taxa) in Late Eocene strata. Specimens from three species and phylogenetic analysis presented in this work shed new light on the systematics and evolution of Antarctic Sphenisciformes. The earliest reported bones of giant penguins from the genus <em>Anthropornis</em> set the conservative estimate of its divergence time at <em>c</em>. 53 Ma (Early Eocene). They also document the oldest known appearance of quite a high diversity of Sphenisciformes; altogether, three morphotypes (differing in size) have been found within the same sampling locality. A newly described, relatively small and intriguingly elongated, tarsometatarsus from the Late Eocene of the La Meseta Formation, belonging to another genus of large-sized Antarctic penguins (<em>Palaeeudyptes</em>), suggests the possible existence of an unnamed species within this long-established genus. The phylogenetic analysis based on tarsometatarsal features shows that the relationship between ‘<em>Archaeospheniscus</em>’ <em>wimani</em> and three species of <em>Delphinornis</em> (all of them co-existed during the Late Eocene time period) does not appear to be close enough to justify merging them into a single genus (as was recently postulated).