cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453350
title: The Mesoproterozoic Rayner Province in the Lambert Glacier area: its age, origin, isotopic structure and implications for Australia–Antarctica correlations

description: Within the Rayner Province in the Lambert Glacier area, two Proterozoic lithotectonic zones are distinguished, which differ in age and lithology. In the Fisher Zone, a significant juvenile component (ε<sub>Nd</sub>(<em>t</em>)=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at <em>c.</em> 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at <em>c.</em> 1150–930 Ma. New U–Pb SHRIMP-II zircon ages (<em>c.</em> 1140 Ma and 1095 Ma – protolith emplacement; <em>c.</em> 950–850 and <em>c.</em> 540 Ma – metamorphism), chemical and Sm–Nd isotopic data indicate that both zones have their continuations in the eastern Amery Ice shelf coast. The Rayner Province has some geological features in common with the Albany-Fraser Orogen in Western Australia, suggesting that these regions evolved in similar tectonic environments at <em>c.</em> 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia.
DOI: 10.6084/m9.figshare.3453350.v1
title: The Mesoproterozoic Rayner Province in the Lambert Glacier area: its age, origin, isotopic structure and implications for Australia–Antarctica correlations

description: Within the Rayner Province in the Lambert Glacier area, two Proterozoic lithotectonic zones are distinguished, which differ in age and lithology. In the Fisher Zone, a significant juvenile component (ε<sub>Nd</sub>(<em>t</em>)=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at <em>c.</em> 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at <em>c.</em> 1150–930 Ma. New U–Pb SHRIMP-II zircon ages (<em>c.</em> 1140 Ma and 1095 Ma – protolith emplacement; <em>c.</em> 950–850 and <em>c.</em> 540 Ma – metamorphism), chemical and Sm–Nd isotopic data indicate that both zones have their continuations in the eastern Amery Ice shelf coast. The Rayner Province has some geological features in common with the Albany-Fraser Orogen in Western Australia, suggesting that these regions evolved in similar tectonic environments at <em>c.</em> 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia.
DOI: 10.6084/m9.figshare.3453344
title: Conjugate divergent margins: an introduction

description: The main objective of this book is to provide a global overview of divergent margins based on geological and geophysical interpretation of sedimentary basins along the South, Central and North Atlantic conjugate margins, from plate tectonics and crustal scales to a more detailed description of stratigraphical and structural elements that are responsible for petroleum plays. These themes are complemented by geodynamic concepts based on physical and numerical models, and by comparisons with present-day embryonic margins, which are succinctly discussed in some papers.
DOI: 10.6084/m9.figshare.3453338
title: <sup>40</sup>Ar/<sup>39</sup>Ar geochronology and the diffusion of <sup>39</sup>Ar in phengite–muscovite intergrowths during step-heating experiments <em>in vacuo</em>

description: Step-heating experiments <em>in vacuo</em> are routine when conducting <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, including for white mica. White mica can break down, due to dehydroxylation and delamination, so experiments involving mica are often conducted in relative haste, and not with the care and precision necessary when intending to apply multi-diffusion-domain theory to model the results. Here we show, however, that carefully managed step-heating experiments appear to allow release of argon through solid-state diffusion processes alone. We analysed phengite-muscovite intergrowths in high-pressure metamorphic rocks exhumed in and beneath extensional ductile shear zones during continental extension. Such materials often yield Arrhenius plots in which there is a distinct steepening of slope mid-way through the step-heating sequence. This steepening appears to correspond with steps in which release of argon from phengite components dominate. We analysed the data using a computer program (<em>eArgon</em>) and numerically simulated mixing of gas released from multiple diffusion domains. The results suggest that diffusion of <sup>39</sup>Ar in phengitic white mica involves radically different diffusion parameters in comparison with muscovite. If these results extrapolate to nature then <sup>40</sup>Ar/<sup>39</sup>Ar geochronology may allow direct dating of white mica mineral growth during metamorphism.
DOI: 10.6084/m9.figshare.3453338.v1
title: <sup>40</sup>Ar/<sup>39</sup>Ar geochronology and the diffusion of <sup>39</sup>Ar in phengite–muscovite intergrowths during step-heating experiments <em>in vacuo</em>

description: Step-heating experiments <em>in vacuo</em> are routine when conducting <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, including for white mica. White mica can break down, due to dehydroxylation and delamination, so experiments involving mica are often conducted in relative haste, and not with the care and precision necessary when intending to apply multi-diffusion-domain theory to model the results. Here we show, however, that carefully managed step-heating experiments appear to allow release of argon through solid-state diffusion processes alone. We analysed phengite-muscovite intergrowths in high-pressure metamorphic rocks exhumed in and beneath extensional ductile shear zones during continental extension. Such materials often yield Arrhenius plots in which there is a distinct steepening of slope mid-way through the step-heating sequence. This steepening appears to correspond with steps in which release of argon from phengite components dominate. We analysed the data using a computer program (<em>eArgon</em>) and numerically simulated mixing of gas released from multiple diffusion domains. The results suggest that diffusion of <sup>39</sup>Ar in phengitic white mica involves radically different diffusion parameters in comparison with muscovite. If these results extrapolate to nature then <sup>40</sup>Ar/<sup>39</sup>Ar geochronology may allow direct dating of white mica mineral growth during metamorphism.
DOI: 10.6084/m9.figshare.3453335
title: Metamorphic grade of source rocks revealed by chemical fingerprints of detrital amphibole and garnet

description: Amphibole and garnet are among the most widespread heavy minerals in orogenic sediments. Their chemical composition and optical properties vary markedly and systematically with temperature and pressure conditions during growth, and thus provide important information on the metamorphic evolution of source areas that is crucial in palaeotectonic and palaeogeodynamic reconstructions. This study investigates the chemical composition of detrital amphiboles and garnets derived from parent rocks of progressively increasing metamorphic grade through a well-studied composite section across the Central and Southern Alps, including the granulite-facies core of the Late Palaeozoic orogen exposed in the Ivrea–Verbano Zone and the amphibolite-facies core of the Cenozoic orogen exposed in the Lepontine Dome. We specifically focus on metamorphic grade because it represents the best proxy for tectono-stratigraphic crustal level, and hence degree of unroofing of source areas. In river sands collected between metamorphic isograds corresponding to crystallization temperatures ranging from <em>c.</em> 500 °C to <em>c.</em> 850 °C, TiO<sub>2</sub> gradually increases in detrital amphibole while its colour progressively changes from blue-green in the lower amphibolite-facies where actinolite, hornblende and tschermakite are most abundant, to brown in the granulite facies where pargasite is dominant. Detrital garnets display moderate gradual changes across the amphibolite-facies Lepontine Dome, where low-Mg ‘type B’ garnets predominate. Almandine-spessartine is spatially associated with abundance of pegmatites while entering the zone of anatexis (Southern Steep Belt), where grossular or grossular-andradite-spessartine are occasionally found. A sharp change occurs while reaching granulite-facies in the Ivrea–Verbano Zone, where high-Mn garnets disappear and ‘type A’ almandine-pyrope (from ‘stronalite’ metasediments) and ‘type C’ almandine-pyrope-grossular (from metagabbros of the Mafic Complex) predominate. Also redefined in this article are a series of numerical indices based on amphibole colour and relative abundances of diverse key minerals (chloritoid, staurolite, andalusite, kyanite, fibrolitic and prismatic sillimanite), useful to accurately assess the average metamorphic grade of meta-igneous and metasedimentary source rocks.
DOI: 10.6084/m9.figshare.3453335.v1
title: Metamorphic grade of source rocks revealed by chemical fingerprints of detrital amphibole and garnet

description: Amphibole and garnet are among the most widespread heavy minerals in orogenic sediments. Their chemical composition and optical properties vary markedly and systematically with temperature and pressure conditions during growth, and thus provide important information on the metamorphic evolution of source areas that is crucial in palaeotectonic and palaeogeodynamic reconstructions. This study investigates the chemical composition of detrital amphiboles and garnets derived from parent rocks of progressively increasing metamorphic grade through a well-studied composite section across the Central and Southern Alps, including the granulite-facies core of the Late Palaeozoic orogen exposed in the Ivrea–Verbano Zone and the amphibolite-facies core of the Cenozoic orogen exposed in the Lepontine Dome. We specifically focus on metamorphic grade because it represents the best proxy for tectono-stratigraphic crustal level, and hence degree of unroofing of source areas. In river sands collected between metamorphic isograds corresponding to crystallization temperatures ranging from <em>c.</em> 500 °C to <em>c.</em> 850 °C, TiO<sub>2</sub> gradually increases in detrital amphibole while its colour progressively changes from blue-green in the lower amphibolite-facies where actinolite, hornblende and tschermakite are most abundant, to brown in the granulite facies where pargasite is dominant. Detrital garnets display moderate gradual changes across the amphibolite-facies Lepontine Dome, where low-Mg ‘type B’ garnets predominate. Almandine-spessartine is spatially associated with abundance of pegmatites while entering the zone of anatexis (Southern Steep Belt), where grossular or grossular-andradite-spessartine are occasionally found. A sharp change occurs while reaching granulite-facies in the Ivrea–Verbano Zone, where high-Mn garnets disappear and ‘type A’ almandine-pyrope (from ‘stronalite’ metasediments) and ‘type C’ almandine-pyrope-grossular (from metagabbros of the Mafic Complex) predominate. Also redefined in this article are a series of numerical indices based on amphibole colour and relative abundances of diverse key minerals (chloritoid, staurolite, andalusite, kyanite, fibrolitic and prismatic sillimanite), useful to accurately assess the average metamorphic grade of meta-igneous and metasedimentary source rocks.
DOI: 10.6084/m9.figshare.3453332
title: Provenance of late Palaeozoic terrestrial sediments on the northern flank of the Mid North Sea High: detrital zircon geochronology and rutile geochemical constraints

description: Zircon U–Pb and rutile trace element data are used to investigate the provenance of late Devonian to early Permian terrestrial sandstones in the Embla and Flora oil fields on the north flank of the Mid North Sea High, central North Sea. Two Old Red Sandstone samples (ORS 1) are dominated by 1.2–0.9 Ga Grenvillian zircons and low- to medium-grade rutile, with sparse Cambro-Ordovician Caledonian zircons (2–4%) and high-grade rutiles (0–5%). The samples are interpreted as recycled metasediments from the Scottish Caledonides. Two other Old Red Sandstone samples (ORS 2) contain a high proportion of Caledonian, mainly Silurian zircons (15–19%) and high-grade rutiles (15–18%); we propose that these components are traceable to the Krummedal sequence on East Greenland (and related sediments). We interpret the data to reflect a temporal evolution of the regional drainage system from northwestern to northeastern sources, with high-grade detritus reaching the Mid North Sea High in the Famennian–early Carboniferous. A late Carboniferous and an early Permian sandstone yielded zircon and rutile signatures compatible with recycling of Palaeozoic sediments north of southernmost Scotland, probably reflecting inversion tectonics. Recycling of Mesoproterozoic to Palaeozoic sediments is thus a prominent feature of the studied late Palaeozoic sandstones.
DOI: 10.6084/m9.figshare.3453329
title: Heavy mineral provenance of the Mesozoic succession in Andøya, northern Norway: implications for sand transport in the Vøring Basin

description: A heavy mineral, mineral chemical and detrital zircon study of Jurassic–Cretaceous (Bathonian–Valanginian) sandstones of the Andøya B borehole, Lofoten–Vesterålen, northern Norway, has revealed the existence of significant differences within the succession. These are related partly to changes in source and partly to variations in the extent of weathering during alluvial storage. Three mineralogical units have been identified. The main change takes place within the Bathonian, and is interpreted as marking a switch from eastern (West Troms) to western (Andøya–Lofoten High) sourcing, consistent with previously published sedimentological models. U–Pb age data indicate that most of the zircons were derived from Palaeoproterozoic rocks (<em>c.</em> 1750–1860 Ma), with a subordinate Archaean group (<em>c.</em> 2600–2800 Ma) and a small early Palaeozoic group (mostly in the 435–446 Ma range). These groups can all be tied back to lithological components of the Lofoten–Vesterålen and West Troms regions, including Palaeozoic rocks hosted in Caledonian allochthons. The provenance characteristics of the Andøya succession have no counterpart in Cretaceous and Paleocene sandstones of the Vøring Basin. This suggests that sediment fed into the basin from Lofoten–Vesterålen was of minor importance, and that prospective Cretaceous–Paleocene hydrocarbon reservoir sandstones in the Vøring Basin were mainly derived from either northern Nordland or northern East Greenland.
DOI: 10.6084/m9.figshare.3453329.v1
title: Heavy mineral provenance of the Mesozoic succession in Andøya, northern Norway: implications for sand transport in the Vøring Basin

description: A heavy mineral, mineral chemical and detrital zircon study of Jurassic–Cretaceous (Bathonian–Valanginian) sandstones of the Andøya B borehole, Lofoten–Vesterålen, northern Norway, has revealed the existence of significant differences within the succession. These are related partly to changes in source and partly to variations in the extent of weathering during alluvial storage. Three mineralogical units have been identified. The main change takes place within the Bathonian, and is interpreted as marking a switch from eastern (West Troms) to western (Andøya–Lofoten High) sourcing, consistent with previously published sedimentological models. U–Pb age data indicate that most of the zircons were derived from Palaeoproterozoic rocks (<em>c.</em> 1750–1860 Ma), with a subordinate Archaean group (<em>c.</em> 2600–2800 Ma) and a small early Palaeozoic group (mostly in the 435–446 Ma range). These groups can all be tied back to lithological components of the Lofoten–Vesterålen and West Troms regions, including Palaeozoic rocks hosted in Caledonian allochthons. The provenance characteristics of the Andøya succession have no counterpart in Cretaceous and Paleocene sandstones of the Vøring Basin. This suggests that sediment fed into the basin from Lofoten–Vesterålen was of minor importance, and that prospective Cretaceous–Paleocene hydrocarbon reservoir sandstones in the Vøring Basin were mainly derived from either northern Nordland or northern East Greenland.
DOI: 10.6084/m9.figshare.3453323
title: Raman spectroscopy in heavy-mineral studies

description: Raman spectroscopy is an innovative tool with tremendous potential, serving as a fundamental complement to a variety of provenance methods including heavy-mineral analysis and detrital geochronology. Because of its accuracy, efficiency and versatility, the results of the Raman technique are indispensable for fully reliable identification of heavy minerals in grain mounts or thin sections. Thorny long-standing problems that cannot be solved confidently with a polarizing microscope alone, such as the determination of opaque and altered heavy minerals, of detrital grains as small as a few microns, or of colourless crystals with uncertain orientation and rounded morphology, can finally be addressed. Although the method can be highly automatized, the full ability and experience of the operator is required to combine Raman data with the optical information obtained under the microscope on the same grains, which is essential for the efficient application of the method in provenance studies. This article provides exemplary Raman spectra useful for the comparison and determination of over 70 different opaque and transparent heavy-mineral species commonly found in sediments, conveying specific information on the genesis of their source rocks, and thus is particularly useful in provenance diagnoses and palaeotectonic reconstructions.
DOI: 10.6084/m9.figshare.3453323.v1
title: Raman spectroscopy in heavy-mineral studies

description: Raman spectroscopy is an innovative tool with tremendous potential, serving as a fundamental complement to a variety of provenance methods including heavy-mineral analysis and detrital geochronology. Because of its accuracy, efficiency and versatility, the results of the Raman technique are indispensable for fully reliable identification of heavy minerals in grain mounts or thin sections. Thorny long-standing problems that cannot be solved confidently with a polarizing microscope alone, such as the determination of opaque and altered heavy minerals, of detrital grains as small as a few microns, or of colourless crystals with uncertain orientation and rounded morphology, can finally be addressed. Although the method can be highly automatized, the full ability and experience of the operator is required to combine Raman data with the optical information obtained under the microscope on the same grains, which is essential for the efficient application of the method in provenance studies. This article provides exemplary Raman spectra useful for the comparison and determination of over 70 different opaque and transparent heavy-mineral species commonly found in sediments, conveying specific information on the genesis of their source rocks, and thus is particularly useful in provenance diagnoses and palaeotectonic reconstructions.
DOI: 10.6084/m9.figshare.3453317
title: Constraints on the timing of Scandian deformation and the nature of a buried Grampian terrane under the Caledonides of northwestern Ireland

description: In the Caledonides of northwestern Ireland there is little evidence for the crystalline basement to the Dalradian Supergroup, though ascertaining its nature is a critical prerequisite for palaeogeographical reconstructions. In Donegal a lamprophyre intrusion has sampled material with isotopic composition, age and fabrics that permit the investigation of the hidden basement of this region. U–Pb and Lu–Hf isotopes in concert with structural analysis are used to elucidate the origin of three morphologically distinct zircon populations from the lamprophyre. The first of these comprises <em>c</em>. 828 to <em>c</em>. 1660 Ma rounded inherited grains. The second population, of 476 ± 3 Ma large xenocrystic grains, displays oscillatory zoned cores embayed by cross-cutting overgrowths, implying a multi-stage magmatic genesis. The third population, of 437 ± 5 Ma high aspect ratio euhedral grains, is interpreted to date the magmatic crystallization of the lamprophyre. Hf isotopic data from the Silurian and Neo- to Mesoproterozoic zircons yield crustal residence ages of 1.0–2.3 Ga. However, the Ordovician grains have ϵHf<sub>i</sub> values of <em>c</em>. −20 and model ages of 2.7–2.8 Ga. These data are consistent with the presence of either Archaean crust or an underthrust Ordovician magmatic rock with an Archaean source component, at depth in NW Ireland. Felsic xenoliths, interpreted to be derived from the country rock Dalradian metasediments, exhibit a pre-entrainment foliation and are randomly oriented relative to the foliation within the lamprophyre matrix, indicating deformation prior to <em>c</em>. 437 Ma, probably related to the Grampian orogeny. The host lamprophyre contains a magmatic foliation parallel to a foliation in the country rock, implying synkinematic emplacement during regional NW–SE compression at 437 Ma.
DOI: 10.6084/m9.figshare.3453317.v1
title: Constraints on the timing of Scandian deformation and the nature of a buried Grampian terrane under the Caledonides of northwestern Ireland

description: In the Caledonides of northwestern Ireland there is little evidence for the crystalline basement to the Dalradian Supergroup, though ascertaining its nature is a critical prerequisite for palaeogeographical reconstructions. In Donegal a lamprophyre intrusion has sampled material with isotopic composition, age and fabrics that permit the investigation of the hidden basement of this region. U–Pb and Lu–Hf isotopes in concert with structural analysis are used to elucidate the origin of three morphologically distinct zircon populations from the lamprophyre. The first of these comprises <em>c</em>. 828 to <em>c</em>. 1660 Ma rounded inherited grains. The second population, of 476 ± 3 Ma large xenocrystic grains, displays oscillatory zoned cores embayed by cross-cutting overgrowths, implying a multi-stage magmatic genesis. The third population, of 437 ± 5 Ma high aspect ratio euhedral grains, is interpreted to date the magmatic crystallization of the lamprophyre. Hf isotopic data from the Silurian and Neo- to Mesoproterozoic zircons yield crustal residence ages of 1.0–2.3 Ga. However, the Ordovician grains have ϵHf<sub>i</sub> values of <em>c</em>. −20 and model ages of 2.7–2.8 Ga. These data are consistent with the presence of either Archaean crust or an underthrust Ordovician magmatic rock with an Archaean source component, at depth in NW Ireland. Felsic xenoliths, interpreted to be derived from the country rock Dalradian metasediments, exhibit a pre-entrainment foliation and are randomly oriented relative to the foliation within the lamprophyre matrix, indicating deformation prior to <em>c</em>. 437 Ma, probably related to the Grampian orogeny. The host lamprophyre contains a magmatic foliation parallel to a foliation in the country rock, implying synkinematic emplacement during regional NW–SE compression at 437 Ma.