cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454400.v1
title: Thermochronological (<sup>40</sup>Ar/<sup>39</sup>Ar) evidence of Early Palaeozoic basin inversion within the southern Prince Charles Mountains, East Antarctica: implications for East Gondwana

description: <sup>40</sup>Ar/<sup>39</sup>Ar systematics within metasedimentary rocks exposed in the southern Prince Charles Mountains, East Antarctica, were thermally reset during a period of Early Palaeozoic (between 524 ± 1 Ma and 486 ± 2 Ma) orogenesis. This event affected three temporally distinct (Archaean to Neoproterozoic) stratigraphic levels that are now exposed in the upper crust. In the structural record, evidence of orogenesis during Early Palaeozoic times is preserved as late-stage, subvertical mylonite zones in the Archaean orthogneiss–metasedimentary basement and thin-skinned folding and thrusting of the overlying Neoproterozoic metasedimentary rocks. Synchronous cooling ages, contrasting structural styles and similar peak metamorphic conditions are interpreted as reflecting basement-involved thin-skinned deformation that was the result of inversion of a Neoproterozoic basin. The presence of pre-existing crustal heterogeneities is the mechanism that localized Early Palaeozoic orogenesis within the region. This interpretation differs from previous models that attribute Early Palaeozoic orogenesis within the southern Prince Charles Mountains to a collisional tectonic setting. An Early Palaeozoic intra-cratonic setting for the region suggests that amalgamation between India and Antarctica was likely to have occurred prior to the final construction of Gondwana.
DOI: 10.6084/m9.figshare.3454397
title: Textural immaturity of cumulates as an indicator of magma chamber processes: infiltration and crystal accumulation in the Rum Eastern Layered Intrusion

description: Textural maturity describes the extent to which rocks have approached textural equilibrium. For igneous rocks, this is a function of the time-integrated thermal history in the sub-solidus which, for cumulate rocks, generally translates to the cooling history via the rate of solidification of the accumulating crystal mush. The most straightforward way to quantify the textural maturity of orthocumulates (<em>sensu lato</em>) is to measure the angle subtended at the corners of interstitial grains. Texturally mature cumulates have angle populations with median values of <em>c</em>. 120°, whereas texturally immature cumulates have lower medians, inherited by the interstitial phase, which infills either an impingement texture in the accumulating mush or a texturally equilibrated pore topology. Textural observations of allivalites from the Rum Layered Suite demonstrate that stratigraphically localized excursions towards textural immaturity are the result of either transient, relatively rapid, solidification rates (perhaps a result of the arrival of cold crystal-laden bodies of fluid on the chamber floor) or late-stage infiltration of fully solidified cumulates by evolved liquids expelled upwards by compaction of underlying horizons. These two processes have distinct textural and compositional signatures.
DOI: 10.6084/m9.figshare.3454397.v1
title: Textural immaturity of cumulates as an indicator of magma chamber processes: infiltration and crystal accumulation in the Rum Eastern Layered Intrusion

description: Textural maturity describes the extent to which rocks have approached textural equilibrium. For igneous rocks, this is a function of the time-integrated thermal history in the sub-solidus which, for cumulate rocks, generally translates to the cooling history via the rate of solidification of the accumulating crystal mush. The most straightforward way to quantify the textural maturity of orthocumulates (<em>sensu lato</em>) is to measure the angle subtended at the corners of interstitial grains. Texturally mature cumulates have angle populations with median values of <em>c</em>. 120°, whereas texturally immature cumulates have lower medians, inherited by the interstitial phase, which infills either an impingement texture in the accumulating mush or a texturally equilibrated pore topology. Textural observations of allivalites from the Rum Layered Suite demonstrate that stratigraphically localized excursions towards textural immaturity are the result of either transient, relatively rapid, solidification rates (perhaps a result of the arrival of cold crystal-laden bodies of fluid on the chamber floor) or late-stage infiltration of fully solidified cumulates by evolved liquids expelled upwards by compaction of underlying horizons. These two processes have distinct textural and compositional signatures.
DOI: 10.6084/m9.figshare.3454394
title: Geochemistry and tectonic setting of mafic rocks in western Dronning Maud Land, East Antarctica: implications for the geodynamic evolution of the Proterozoic Maud Belt

description: On the basis of new bulk major and trace element (including REE) as well as Sm–Nd and Rb–Sr isotope data, used in conjunction with available geochronological data, a post-tectonic mafic igneous province and four groups of pre- to syntectonic amphibolite are distinguished in the polymetamorphic Maud Belt of western Dronning Maud Land, East Antarctica. Protoliths of the Group 1 amphibolites are interpreted as volcanic arc mafic intrusions with Archaean to Palaeoproterozoic Nd model ages and depletion in Nb and Ta. Isotopic and lithogeochemical characteristics of this earliest group of amphibolite indicate that the Maud Belt was once an active continental volcanic arc. The most likely position of this arc, for which a late Mesoproterozoic age (<em>c</em>. 1140 Ma) is indicated by available U–Pb single-zircon age data, was on the southeastern margin of the Kaapvaal–Grunehogna Craton. The protoliths of Group 2 amphibolites are attributed to the 1110 Ma Borgmassivet–Umkondo thermal event on the basis of comparable Nd model ages and trace element distributions. Group 3 amphibolite protoliths are characterized by mid-ocean ridge basalt-type REE patterns and low Th/Yb ratios, and they are related to Neoproterozoic extension. Group 4 amphibolite protoliths are distinguished by high Dy/Yb ratios and are attributed to a phase of syntectonic Pan-African magmatism as indicated by Rb–Sr isotope data.
DOI: 10.6084/m9.figshare.3454394.v1
title: Geochemistry and tectonic setting of mafic rocks in western Dronning Maud Land, East Antarctica: implications for the geodynamic evolution of the Proterozoic Maud Belt

description: On the basis of new bulk major and trace element (including REE) as well as Sm–Nd and Rb–Sr isotope data, used in conjunction with available geochronological data, a post-tectonic mafic igneous province and four groups of pre- to syntectonic amphibolite are distinguished in the polymetamorphic Maud Belt of western Dronning Maud Land, East Antarctica. Protoliths of the Group 1 amphibolites are interpreted as volcanic arc mafic intrusions with Archaean to Palaeoproterozoic Nd model ages and depletion in Nb and Ta. Isotopic and lithogeochemical characteristics of this earliest group of amphibolite indicate that the Maud Belt was once an active continental volcanic arc. The most likely position of this arc, for which a late Mesoproterozoic age (<em>c</em>. 1140 Ma) is indicated by available U–Pb single-zircon age data, was on the southeastern margin of the Kaapvaal–Grunehogna Craton. The protoliths of Group 2 amphibolites are attributed to the 1110 Ma Borgmassivet–Umkondo thermal event on the basis of comparable Nd model ages and trace element distributions. Group 3 amphibolite protoliths are characterized by mid-ocean ridge basalt-type REE patterns and low Th/Yb ratios, and they are related to Neoproterozoic extension. Group 4 amphibolite protoliths are distinguished by high Dy/Yb ratios and are attributed to a phase of syntectonic Pan-African magmatism as indicated by Rb–Sr isotope data.
DOI: 10.6084/m9.figshare.3454391
title: Thermo-chronology of the Barlet metamorphic basement unit: evidence for a Stephanian thermal event linked to Sb mineralization in the Haut Allier, France

description: A thermo-chronological analysis of the Barlet basement unit (French Massif Central) reveals a four-stage history. Peak metamorphism (650 °C and 7 kbar) was followed by retrograde growth of albite blasts and development of the main foliation at 600 °C, and chloritization of the ferromagnesian minerals. The third stage is a marked reversal of cooling, with recrossing of the biotite isograd and local reappearance of garnet at 450 °C. This thermal event, inferred to result from hot fluid infiltration, is also recognized in the adjacent basin of Langeac, where it gives rise to anomalous coal grades (recording 200 °C at 1 km). A Stephanian age for this event correlates with a regional thermal event recognized throughout the Variscan, where it has been linked to delamination of the continental crust. This work represents the first instance in the Massif Central that recognizes this event in the shallow basement itself. Final cooling is accompanied by extensive fluid-induced sericitization, starting immediately after the peak of the thermal event and continuing to temperatures inferred for Sb–As ore deposition. This continuum leads us to conclude that reheating-related silicate reactions and ore deposition are caused by the same fluid and related to the wider regional Variscan thermal event.
DOI: 10.6084/m9.figshare.3454391.v1
title: Thermo-chronology of the Barlet metamorphic basement unit: evidence for a Stephanian thermal event linked to Sb mineralization in the Haut Allier, France

description: A thermo-chronological analysis of the Barlet basement unit (French Massif Central) reveals a four-stage history. Peak metamorphism (650 °C and 7 kbar) was followed by retrograde growth of albite blasts and development of the main foliation at 600 °C, and chloritization of the ferromagnesian minerals. The third stage is a marked reversal of cooling, with recrossing of the biotite isograd and local reappearance of garnet at 450 °C. This thermal event, inferred to result from hot fluid infiltration, is also recognized in the adjacent basin of Langeac, where it gives rise to anomalous coal grades (recording 200 °C at 1 km). A Stephanian age for this event correlates with a regional thermal event recognized throughout the Variscan, where it has been linked to delamination of the continental crust. This work represents the first instance in the Massif Central that recognizes this event in the shallow basement itself. Final cooling is accompanied by extensive fluid-induced sericitization, starting immediately after the peak of the thermal event and continuing to temperatures inferred for Sb–As ore deposition. This continuum leads us to conclude that reheating-related silicate reactions and ore deposition are caused by the same fluid and related to the wider regional Variscan thermal event.
DOI: 10.6084/m9.figshare.3454388
title: Terrane analysis along a Neoproterozoic active margin of Gondwana: insights from U–Pb zircon geochronology

description: The tectonic affinities of terranes in accretionary orogens can be evaluated using geochronological techniques. U–Pb zircon data obtained from paragneisses of the Coedana Complex (Anglesey) and the Malverns Complex, southern Britain, indicate that they were deposited during the mid- to late Neoproterozoic and have a comparable Amazonian provenance. Metamorphism of the Coedana gneisses occurred at 666 ± 7 Ma, similar to the age of metamorphism in the Malverns Complex. Anglesey therefore probably evolved in proximity to the Avalonian basement of mainland southern Britain during the mid- to late Neoproterozoic and is not a ‘suspect terrane’ relative to the remainder of Avalonia.
DOI: 10.6084/m9.figshare.3454388.v1
title: Terrane analysis along a Neoproterozoic active margin of Gondwana: insights from U–Pb zircon geochronology

description: The tectonic affinities of terranes in accretionary orogens can be evaluated using geochronological techniques. U–Pb zircon data obtained from paragneisses of the Coedana Complex (Anglesey) and the Malverns Complex, southern Britain, indicate that they were deposited during the mid- to late Neoproterozoic and have a comparable Amazonian provenance. Metamorphism of the Coedana gneisses occurred at 666 ± 7 Ma, similar to the age of metamorphism in the Malverns Complex. Anglesey therefore probably evolved in proximity to the Avalonian basement of mainland southern Britain during the mid- to late Neoproterozoic and is not a ‘suspect terrane’ relative to the remainder of Avalonia.
DOI: 10.6084/m9.figshare.3454382
title: Evidence for anoxia at the Ediacaran–Cambrian boundary: the record of redox-sensitive trace elements and rare earth elements in Oman

description: The Ediacaran–Cambrian boundary in Oman is characterized by a globally correlative negative δ<sup>13</sup>C<sub>carb</sub> excursion in platform carbonate rocks, and deposition of basinal organic-rich rocks. These observations may relate to the development of local, and possibly global, anoxia. We have studied redox-sensitive trace elements (TE) and REE from basinal and platform successions. Detrital input and authigenic element enrichment were the main factors controlling the record of TE and REE. Trace elements in the basin are enriched relative to crustal concentrations. In siliceous rocks, TE enrichment was decoupled from detrital input, suggesting authigenic concentration of TE under anoxic (possibly sulphidic) water column conditions. Trace elements and REE indicate higher detrital input in shales. Element enrichment was minimally influenced by detrital input in the platform carbonate rocks; it is strongest in the basal platform section, coincident with the carbon isotope excursion. The results suggest development of anoxia in a stagnant basinal water mass. Overturn or upward expansion of the deep water charged with TE and isotopically light C produced anoxia on the platform, and was probably related to development of the isotope excursion. These results are consistent with anoxia in boundary strata of Iran, and with the hypothesis of global anoxia at this time.
DOI: 10.6084/m9.figshare.3454382.v1
title: Evidence for anoxia at the Ediacaran–Cambrian boundary: the record of redox-sensitive trace elements and rare earth elements in Oman

description: The Ediacaran–Cambrian boundary in Oman is characterized by a globally correlative negative δ<sup>13</sup>C<sub>carb</sub> excursion in platform carbonate rocks, and deposition of basinal organic-rich rocks. These observations may relate to the development of local, and possibly global, anoxia. We have studied redox-sensitive trace elements (TE) and REE from basinal and platform successions. Detrital input and authigenic element enrichment were the main factors controlling the record of TE and REE. Trace elements in the basin are enriched relative to crustal concentrations. In siliceous rocks, TE enrichment was decoupled from detrital input, suggesting authigenic concentration of TE under anoxic (possibly sulphidic) water column conditions. Trace elements and REE indicate higher detrital input in shales. Element enrichment was minimally influenced by detrital input in the platform carbonate rocks; it is strongest in the basal platform section, coincident with the carbon isotope excursion. The results suggest development of anoxia in a stagnant basinal water mass. Overturn or upward expansion of the deep water charged with TE and isotopically light C produced anoxia on the platform, and was probably related to development of the isotope excursion. These results are consistent with anoxia in boundary strata of Iran, and with the hypothesis of global anoxia at this time.
DOI: 10.6084/m9.figshare.3454379
title: Detrital zircon ages in Neoproterozoic to Ordovician siliciclastic rocks, northeastern Australia: implications for the tectonic history of the East Gondwana continental margin

description: U–Pb detrital zircon ages in variably metamorphosed, dominantly fine-grained clastic successions are used in northeastern Australia to identify two major successions along the East Gondwana margin. The older succession is of probable Late Neoproterozoic age and is considered part of a passive margin associated with rifting at <em>c</em>. 600 Ma. Most detrital zircons have ages in the range 1000–1300 Ma and were probably derived from an extension of a Late Mesoproterozoic (1050–1200 Ma) orogenic belt from the central Australian Musgrave Complex located 1500 km to the west. No evidence has been found for 600–800 Ma rifting of a Rodinian supercontinent and therefore it is suggested that breakup must have occurred well outboard of the present Early Palaeozoic East Gondwana margin. The younger succession is of Early Palaeozoic age and contains the distinctive 500–600 Ma detrital zircon signature that is widespread in East Gondwana in addition to some samples with ages in the range 460–510 Ma consistent with local igneous sources. The younger succession is related to the active margin of Gondwana that developed on the former passive margin in a back-arc setting, and the source of 510–600 Ma zircons is considered to be a composite of rift-related and back-arc volcanic sources.
DOI: 10.6084/m9.figshare.3454376
title: A pre-Rodinian ophiolite involved in the Variscan suture of Galicia (Cabo Ortegal Complex, NW Spain)

description: U–Pb dating of zircons from a metagabbro of the Purrido amphibolitic unit (Cabo Ortegal Complex, NW Iberian Massif) yielded an age of 1159 ± 39 Ma, interpreted to approximate the crystallization age of the gabbroic protolith. Considering the arc affinity of the metagabbroic rocks, the unit is interpreted as a pre-Rodinian ophiolite developed in a back-arc setting. It is suggested that the ophiolite was obducted over the West African terranes during the assembly of Rodinia. There, this terrane remained tectonically stable and facing an ocean for a long time, and eventually became part of the Gondwanan margin. The ophiolite was finally involved in the Variscan suture of Galicia where it is sandwiched between Palaeozoic rocks. The Purrido unit is so far the only example of a Mesoproterozoic ophiolite in the European Variscan belt, where pre-Neoproterozoic rocks are very scarce and restricted to small exposures.
DOI: 10.6084/m9.figshare.3454379.v1
title: Detrital zircon ages in Neoproterozoic to Ordovician siliciclastic rocks, northeastern Australia: implications for the tectonic history of the East Gondwana continental margin

description: U–Pb detrital zircon ages in variably metamorphosed, dominantly fine-grained clastic successions are used in northeastern Australia to identify two major successions along the East Gondwana margin. The older succession is of probable Late Neoproterozoic age and is considered part of a passive margin associated with rifting at <em>c</em>. 600 Ma. Most detrital zircons have ages in the range 1000–1300 Ma and were probably derived from an extension of a Late Mesoproterozoic (1050–1200 Ma) orogenic belt from the central Australian Musgrave Complex located 1500 km to the west. No evidence has been found for 600–800 Ma rifting of a Rodinian supercontinent and therefore it is suggested that breakup must have occurred well outboard of the present Early Palaeozoic East Gondwana margin. The younger succession is of Early Palaeozoic age and contains the distinctive 500–600 Ma detrital zircon signature that is widespread in East Gondwana in addition to some samples with ages in the range 460–510 Ma consistent with local igneous sources. The younger succession is related to the active margin of Gondwana that developed on the former passive margin in a back-arc setting, and the source of 510–600 Ma zircons is considered to be a composite of rift-related and back-arc volcanic sources.
DOI: 10.6084/m9.figshare.3454376.v1
title: A pre-Rodinian ophiolite involved in the Variscan suture of Galicia (Cabo Ortegal Complex, NW Spain)

description: U–Pb dating of zircons from a metagabbro of the Purrido amphibolitic unit (Cabo Ortegal Complex, NW Iberian Massif) yielded an age of 1159 ± 39 Ma, interpreted to approximate the crystallization age of the gabbroic protolith. Considering the arc affinity of the metagabbroic rocks, the unit is interpreted as a pre-Rodinian ophiolite developed in a back-arc setting. It is suggested that the ophiolite was obducted over the West African terranes during the assembly of Rodinia. There, this terrane remained tectonically stable and facing an ocean for a long time, and eventually became part of the Gondwanan margin. The ophiolite was finally involved in the Variscan suture of Galicia where it is sandwiched between Palaeozoic rocks. The Purrido unit is so far the only example of a Mesoproterozoic ophiolite in the European Variscan belt, where pre-Neoproterozoic rocks are very scarce and restricted to small exposures.
DOI: 10.6084/m9.figshare.3454373
title: Laccolithic, as opposed to cauldron subsidence, emplacement of the Eastern Mourne pluton, N. Ireland: evidence from anisotropy of magnetic susceptibility

description: The structural evolution and emplacement of the Eastern Mourne pluton was investigated using anisotropy of magnetic susceptibility (AMS) measurements (carried out on 112 oriented block samples) and structural data from the host rocks. From these new data cauldron subsidence, as the emplacement mechanism, is disputed and evidence for an alternative, laccolithic style model involving inflation is presented. This includes deflection and uplift of host-rock bedding close to contacts and the magnetic fabric pattern, which has a gentle dome geometry, even close to contacts. The magnetic lineations usually plunge down-dip near the external margins but otherwise have a general SSW–NNE trend that diverges northward. This suggests a northward-directed inflow direction. The model for the emplacement of the Eastern Mourne pluton is a laterally fed laccolith, emplaced south to north. The eastern margin is interpreted as a faulted contact facilitating the inflation of an asymmetrical ‘breached’ laccolith.
DOI: 10.6084/m9.figshare.3454373.v1
title: Laccolithic, as opposed to cauldron subsidence, emplacement of the Eastern Mourne pluton, N. Ireland: evidence from anisotropy of magnetic susceptibility

description: The structural evolution and emplacement of the Eastern Mourne pluton was investigated using anisotropy of magnetic susceptibility (AMS) measurements (carried out on 112 oriented block samples) and structural data from the host rocks. From these new data cauldron subsidence, as the emplacement mechanism, is disputed and evidence for an alternative, laccolithic style model involving inflation is presented. This includes deflection and uplift of host-rock bedding close to contacts and the magnetic fabric pattern, which has a gentle dome geometry, even close to contacts. The magnetic lineations usually plunge down-dip near the external margins but otherwise have a general SSW–NNE trend that diverges northward. This suggests a northward-directed inflow direction. The model for the emplacement of the Eastern Mourne pluton is a laterally fed laccolith, emplaced south to north. The eastern margin is interpreted as a faulted contact facilitating the inflation of an asymmetrical ‘breached’ laccolith.