cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454604.v1
title: Middle Devonian microfloras and megafloras from western Argentina and southern Bolivia: their importance in the palaeobiogeographical and palaeoclimatic evolution of western Gondwana

description: The study of microfloras and megafloras from western Argentina and southern Bolivia presented here extends our knowledge of the biodiversity and succession of floristic events during the Middle Devonian, and hence improves the current biostratigraphy. Among floral remains, species attributable to ‘<em>Haplostigma</em>’ are mostly recorded from the same <em>Grandispora pseudoreticulata</em> and other palynomorph-bearing sections at Balapuca (southern Bolivia) and Del Chaco and La Cortadera creeks in the Precordillera of Argentina. The northernmost record of <em>Grandispora pseudoreticulata</em> is recorded from a third palynoassemblage from the Pando x-1 corehole of northern Bolivia. A great similarity among all these assemblages (notably abundant <em>Grandispora pseudoreticulata</em>) suggests the identification of terrestrial connections, or at least proximity, of these local areas and other regions in South America during the Givetian. Comparison with other contemporary Gondwanan palynofloras shows cosmopolitan species (e.g. <em>Geminospora lemurata</em>, <em>Samarisporites triangulatus</em>, <em>Archaeozonotriletes variabilis</em>, <em>Chelinospora concinna</em>) along with some others with more restricted distribution (e.g. <em>Grandispora pseudoreticulata</em>, <em>Leiotriletes balapucensis</em>, <em>Acinosporites ledundae</em>). This pattern defines an Afro-South American Subrealm, which most likely results from the effects of palaeolatitude and, in a lesser way, local palaeoenvironmental conditions. On the other hand, such a level of cosmopolitanism supports previous palaeogeographical reconstructions where a narrow Rheic Ocean was developed between Euramerica and the northern parts of Africa and South America.
DOI: 10.6084/m9.figshare.3454601
title: Comprehensive refertilization of lithospheric mantle beneath the North China Craton: further Os–Sr–Nd isotopic constraints

description: Mantle peridotitic xenoliths in Cenozoic basalts from Hannuoba, on the northern margin of the Archaean North China Craton, have variable Re (0.01–0.30 ppb) and Os (2.7–6.2 ppb) abundances and <sup>187</sup>Os/<sup>188</sup>Os (0.1138–0.1236) ratios. These xenoliths yield a range of Proterozoic Re depletion ages of 0.8–2.2 Ga that show a general correlation with olivine Fo. Mantle xenoliths in Cenozoic basalts from the centre and southern margin of the North China Craton also overwhelmingly show Proterozoic Re depletion ages that correlate with olivine Fo. These Re–Os age features are completely different from those of Palaeozoic kimberlite-borne peridotitic xenoliths, which have Archaean ages. This age distinction between xenoliths associated with Palaeozoic and Cenozoic volcanism indicates that the present-day lithospheric mantle was dominantly not newly accreted during the Phanerozoic but instead was transformed from the ancient lithospheric mantle by interaction with melts. The Re–Os data in combination with the geochemical and Sr–Nd isotopic features of peridotitic xenoliths from the Cenozoic basalts of the North China Craton demonstrate the presence of multiple stages of mantle metasomatic overprints in the lithospheric mantle. This study thus further indicates that lithospheric transformation through melt–rock interaction could be an important mechanism for compositional refertilization during the Phanerozoic.
DOI: 10.6084/m9.figshare.3454601.v1
title: Comprehensive refertilization of lithospheric mantle beneath the North China Craton: further Os–Sr–Nd isotopic constraints

description: Mantle peridotitic xenoliths in Cenozoic basalts from Hannuoba, on the northern margin of the Archaean North China Craton, have variable Re (0.01–0.30 ppb) and Os (2.7–6.2 ppb) abundances and <sup>187</sup>Os/<sup>188</sup>Os (0.1138–0.1236) ratios. These xenoliths yield a range of Proterozoic Re depletion ages of 0.8–2.2 Ga that show a general correlation with olivine Fo. Mantle xenoliths in Cenozoic basalts from the centre and southern margin of the North China Craton also overwhelmingly show Proterozoic Re depletion ages that correlate with olivine Fo. These Re–Os age features are completely different from those of Palaeozoic kimberlite-borne peridotitic xenoliths, which have Archaean ages. This age distinction between xenoliths associated with Palaeozoic and Cenozoic volcanism indicates that the present-day lithospheric mantle was dominantly not newly accreted during the Phanerozoic but instead was transformed from the ancient lithospheric mantle by interaction with melts. The Re–Os data in combination with the geochemical and Sr–Nd isotopic features of peridotitic xenoliths from the Cenozoic basalts of the North China Craton demonstrate the presence of multiple stages of mantle metasomatic overprints in the lithospheric mantle. This study thus further indicates that lithospheric transformation through melt–rock interaction could be an important mechanism for compositional refertilization during the Phanerozoic.
DOI: 10.6084/m9.figshare.3454598
title: The Akilia Controversy: field, structural and geochronological evidence questions interpretations of &gt;3.8 Ga life in SW Greenland

description: Field relations, structure and geochronology demonstrate that controversial rocks on Akilia, SW Greenland, cannot host evidence of Earth's oldest life. Mafic–ultramafic gneiss that contains a layer of quartz–amphibole–pyroxene gneiss, a few metres thick, with purported biogenic graphite is not cross-cut by the protoliths of &gt;3.82–3.65 Ga tonalitic gneiss. The contact between these gneisses is tectonic so their relative ages are unknown. Multiple episodes of intrusion and deformation in the tonalitic gneiss preceded the earliest deformation fabrics and structures seen in the mafic–ultramafic gneiss. Although previously interpreted as a volcano-sedimentary stratigraphy, the mafic–ultramafic gneiss displays no evidence of such an origin, and could be partly or wholly derived from igneous intrusions. Existing geochronology indicates that the mafic–ultramafic and qtz–am–px gneisses have ages &lt;3.67 Ga. Metamorphic zircon in the qtz–am–px gneiss grew at <em>c</em>. 2.68 Ga during late Archaean high-grade events that complicate any protolith interpretation. U–Pb dating of apatite from a variety of rocks on Akilia shows that this mineral crystallized, or possibly recrystallized, at <em>c</em>. 1.75 Ga and it thus provides no indication of an early Archaean age for any associated graphite, regardless of whether or not the latter is biogenic.
DOI: 10.6084/m9.figshare.3454598.v1
title: The Akilia Controversy: field, structural and geochronological evidence questions interpretations of &gt;3.8 Ga life in SW Greenland

description: Field relations, structure and geochronology demonstrate that controversial rocks on Akilia, SW Greenland, cannot host evidence of Earth's oldest life. Mafic–ultramafic gneiss that contains a layer of quartz–amphibole–pyroxene gneiss, a few metres thick, with purported biogenic graphite is not cross-cut by the protoliths of &gt;3.82–3.65 Ga tonalitic gneiss. The contact between these gneisses is tectonic so their relative ages are unknown. Multiple episodes of intrusion and deformation in the tonalitic gneiss preceded the earliest deformation fabrics and structures seen in the mafic–ultramafic gneiss. Although previously interpreted as a volcano-sedimentary stratigraphy, the mafic–ultramafic gneiss displays no evidence of such an origin, and could be partly or wholly derived from igneous intrusions. Existing geochronology indicates that the mafic–ultramafic and qtz–am–px gneisses have ages &lt;3.67 Ga. Metamorphic zircon in the qtz–am–px gneiss grew at <em>c</em>. 2.68 Ga during late Archaean high-grade events that complicate any protolith interpretation. U–Pb dating of apatite from a variety of rocks on Akilia shows that this mineral crystallized, or possibly recrystallized, at <em>c</em>. 1.75 Ga and it thus provides no indication of an early Archaean age for any associated graphite, regardless of whether or not the latter is biogenic.
DOI: 10.6084/m9.figshare.3454595
title: Correlations between silicic volcanic rocks of the St Mary's Islands (southwestern India) and eastern Madagascar: implications for Late Cretaceous India–Madagascar reconstructions

description: The St Mary's Islands (southwestern India) expose silicic volcanic and sub-volcanic rocks (rhyolites and granophyric dacites) emplaced contemporaneously with the Cretaceous igneous province of Madagascar, roughly 88–90 Ma ago. The St Mary's Islands rocks have phenocrysts of plagioclase, clinopyroxene, orthopyroxene and opaque oxide, moderate enrichment in the incompatible elements (e.g. Zr = 580–720 ppm, Nb = 43–53 ppm, La/Yb<sub>n</sub> = 6.9–7.2), relatively low initial <sup>87</sup>Sr/<sup>86</sup>Sr (0.7052–0.7055) and near-chondritic initial <sup>143</sup>Nd/<sup>144</sup>Nd (0.51248–0.51249). They have mineral chemical, whole-rock chemical and isotopic compositions very close to those of rhyolites exposed between Vatomandry–Ilaka and Mananjary in eastern Madagascar, and are distinctly different from rhyolites from other sectors of the Madagascan province. We therefore postulate that the St Mary's and the Vatomandry–Ilaka–Mananjary silicic rock outcrops were adjacent before the Late Cretaceous rifting that split Madagascar from India. If so, they provide a valuable tool to check and aid traditional Cretaceous India–Madagascar reconstructions based on palaeomagnetism, matching Precambrian geological features, and geometric fitting of continental shelves.
DOI: 10.6084/m9.figshare.3454595.v1
title: Correlations between silicic volcanic rocks of the St Mary's Islands (southwestern India) and eastern Madagascar: implications for Late Cretaceous India–Madagascar reconstructions

description: The St Mary's Islands (southwestern India) expose silicic volcanic and sub-volcanic rocks (rhyolites and granophyric dacites) emplaced contemporaneously with the Cretaceous igneous province of Madagascar, roughly 88–90 Ma ago. The St Mary's Islands rocks have phenocrysts of plagioclase, clinopyroxene, orthopyroxene and opaque oxide, moderate enrichment in the incompatible elements (e.g. Zr = 580–720 ppm, Nb = 43–53 ppm, La/Yb<sub>n</sub> = 6.9–7.2), relatively low initial <sup>87</sup>Sr/<sup>86</sup>Sr (0.7052–0.7055) and near-chondritic initial <sup>143</sup>Nd/<sup>144</sup>Nd (0.51248–0.51249). They have mineral chemical, whole-rock chemical and isotopic compositions very close to those of rhyolites exposed between Vatomandry–Ilaka and Mananjary in eastern Madagascar, and are distinctly different from rhyolites from other sectors of the Madagascan province. We therefore postulate that the St Mary's and the Vatomandry–Ilaka–Mananjary silicic rock outcrops were adjacent before the Late Cretaceous rifting that split Madagascar from India. If so, they provide a valuable tool to check and aid traditional Cretaceous India–Madagascar reconstructions based on palaeomagnetism, matching Precambrian geological features, and geometric fitting of continental shelves.
DOI: 10.6084/m9.figshare.3454592
title: Detrital zircon provenance and Ordovician terrane amalgamation, western Ireland

description: Detrital zircon analysis of sandstones interbedded with <em>c</em>. 464 Ma ignimbrites in the lower Mweelrea Formation of the South Mayo Trough, western Ireland, suggests Ordovician source-rock provenance that corresponds to two distinct volcanic-arc phases on the Laurentian margin. East-derived sandstones contain a suite of zircons with a mean age of <em>c</em>. 487 Ma that suggests derivation from the Cambrian to early Ordovician Baie Verte Oceanic Tract arc–ophiolite complex, locally represented by the Lough Nafooey arc rocks and the Clew Bay Complex. Zircons from south-derived sandstones within the Bunnacunneen conglomerate fan have average ages of <em>c</em>. 467–474 Ma, and correspond to the Notre Dame arc and locally the Connemara metagabbro and orthogneiss suite. Granite clasts in the Bunnacunneen conglomerate are similar to the Connemara orthogneiss suite, in terms of both their geochemistry and their age (<em>c</em>. 471 Ma). The southerly derived sedimentary strata also include Archaean and Proterozoic zircon age spectra consistent with a Dalradian source. A southern provenance from the Notre Dame arc and Dalradian rocks suggests that the Connemara terrane lay to the south of the South Mayo Trough during middle Llanvirn times, from at least 464 Ma.
DOI: 10.6084/m9.figshare.3454592.v1
title: Detrital zircon provenance and Ordovician terrane amalgamation, western Ireland

description: Detrital zircon analysis of sandstones interbedded with <em>c</em>. 464 Ma ignimbrites in the lower Mweelrea Formation of the South Mayo Trough, western Ireland, suggests Ordovician source-rock provenance that corresponds to two distinct volcanic-arc phases on the Laurentian margin. East-derived sandstones contain a suite of zircons with a mean age of <em>c</em>. 487 Ma that suggests derivation from the Cambrian to early Ordovician Baie Verte Oceanic Tract arc–ophiolite complex, locally represented by the Lough Nafooey arc rocks and the Clew Bay Complex. Zircons from south-derived sandstones within the Bunnacunneen conglomerate fan have average ages of <em>c</em>. 467–474 Ma, and correspond to the Notre Dame arc and locally the Connemara metagabbro and orthogneiss suite. Granite clasts in the Bunnacunneen conglomerate are similar to the Connemara orthogneiss suite, in terms of both their geochemistry and their age (<em>c</em>. 471 Ma). The southerly derived sedimentary strata also include Archaean and Proterozoic zircon age spectra consistent with a Dalradian source. A southern provenance from the Notre Dame arc and Dalradian rocks suggests that the Connemara terrane lay to the south of the South Mayo Trough during middle Llanvirn times, from at least 464 Ma.
DOI: 10.6084/m9.figshare.3454589
title: Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

description: Zircons from nine Palaeoproterozoic granitoid intrusions within the southern part of the Fennoscandian Shield have been studied by laser ablation inductively coupled plasma source mass spectrometry to obtain U–Pb ages (in the range 1.88–1.68 Ga) and Hf isotope compositions. Six granitoids are from the 1.85–1.65 Ga Transscandinavian Igneous Belt; during that period more than 10<sup>6 </sup>km<sup>3</sup> of granitoid magma intruded the pre-existing crust. The large majority of magmatic zircons from the nine granitoids have a limited initial range, <sup>176</sup>Hf/<sup>177</sup>Hf = 0.2816–0.2818, and define an evolutionary trend given by an initial value of ε<sub>Hf(1.88Ga)</sub> ≈ +2 ± 3 at an average <sup>176</sup>Lu/<sup>177</sup>Hf = 0.015. These data show that a geographically extensive, long-lived, relatively homogeneous, and dominant magma source resided within 2.1–1.86 Ga Svecofennian juvenile crust between 1.88 and 1.68 Ga. Zircon xenocrysts (1.91–1.98 Ga) with initial ε<sub>Hf</sub> = +0 to +2.5 from one of the intrusions provide additional evidence for such a long-lived crustal source of granitic magmas in central Fennoscandia. The granitoids were emplaced during a period of active mafic underplating that supplied heat to the anatectic zone in the lower–middle crust, but little or no mantle-derived Hf to the granitic magmas, in contrast to many mixed intermediate rocks.
DOI: 10.6084/m9.figshare.3454586
title: The significance of the contemporaneous Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism

description: The relationships between meteorite impact craters, flood basalt volcanism and sudden environmental perturbation on Earth have been debated extensively. We present only the second example of contemporaneous meteorite impact and flood basalt volcanism: the 17 km diameter Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism. The new precise <sup>40</sup>Ar/<sup>39</sup>Ar age of 29.71 ± 0.48 Ma for Logoisk is coincident with the acme of flood volcanism. We argue that at least one crater the size of Logoisk is likely to form during the emplacement of a flood volcanic province, and that contemporaneity of impacts and flood volcanism was the norm. The absence of a biotic effect from the combined Logoisk–Afro-Arabian volcanism we attribute to the magnitude of these combined events, which are both significantly smaller than the other known example of the Chicxulub impact event and the Deccan Traps flood volcanism.
DOI: 10.6084/m9.figshare.3454586.v1
title: The significance of the contemporaneous Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism

description: The relationships between meteorite impact craters, flood basalt volcanism and sudden environmental perturbation on Earth have been debated extensively. We present only the second example of contemporaneous meteorite impact and flood basalt volcanism: the 17 km diameter Logoisk impact structure (Belarus) and Afro-Arabian flood volcanism. The new precise <sup>40</sup>Ar/<sup>39</sup>Ar age of 29.71 ± 0.48 Ma for Logoisk is coincident with the acme of flood volcanism. We argue that at least one crater the size of Logoisk is likely to form during the emplacement of a flood volcanic province, and that contemporaneity of impacts and flood volcanism was the norm. The absence of a biotic effect from the combined Logoisk–Afro-Arabian volcanism we attribute to the magnitude of these combined events, which are both significantly smaller than the other known example of the Chicxulub impact event and the Deccan Traps flood volcanism.
DOI: 10.6084/m9.figshare.3454583
title: Degree of magnetic anisotropy as a strain-intensity gauge in a saturated finite-strain zone

description: Anisotropy of magnetic susceptibility (AMS) analyses were carried out on mylonitic quartzites from the footwall of the Main Central Thrust Zone, Garhwal Higher Himalaya, India. A systematic increase in degree of magnetic anisotropy (<em>P</em>′) with distance from the Main Central Thrust is documented, even in a saturated finite-strain zone. On the basis of correlation between orientation of principal AMS axes and multidomain magnetite and the mylonitic foliation and lineation direction, strain-related recrystallization was inferred to be the cause of development of the magnetic fabric. Based on these results, it is concluded that if <em>P</em>′ is not controlled by <em>K</em><sub>m</sub>, then the former can be used as a strain-intensity gauge.
DOI: 10.6084/m9.figshare.3454583.v1
title: Degree of magnetic anisotropy as a strain-intensity gauge in a saturated finite-strain zone

description: Anisotropy of magnetic susceptibility (AMS) analyses were carried out on mylonitic quartzites from the footwall of the Main Central Thrust Zone, Garhwal Higher Himalaya, India. A systematic increase in degree of magnetic anisotropy (<em>P</em>′) with distance from the Main Central Thrust is documented, even in a saturated finite-strain zone. On the basis of correlation between orientation of principal AMS axes and multidomain magnetite and the mylonitic foliation and lineation direction, strain-related recrystallization was inferred to be the cause of development of the magnetic fabric. Based on these results, it is concluded that if <em>P</em>′ is not controlled by <em>K</em><sub>m</sub>, then the former can be used as a strain-intensity gauge.
DOI: 10.6084/m9.figshare.3454580
title: Post-collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield: time constraints from ion-probe U–Pb dating of zircon

description: Ion-probe U–Pb dating of plutonic rocks from the northern Arabian–Nubian Shield in Sinai and southern Israel constrains the timing of late East African batholithic post-collisional calc-alkaline (CA2) magmatism and within-plate alkaline to peralkaline (AL) magmatism to <em>c</em>. 635–590 Ma and <em>c</em>. 608–580 Ma, respectively. The earliest dated CA2 rocks are slightly deformed to undeformed, indicating that penetrative deformation ceased by <em>c</em>. 630 Ma. Within the CA2 suite a change from mafic to felsic magmatism is manifested in most of the region, peaking in a voluminous pulse of granodiorite to granite intrusion at 610–600 Ma. The AL magmatism started contemporaneously with the peak in CA2 felsic activity at <em>c</em>. 608 Ma and lasted until 580 Ma. It includes mostly alkaline and peralkaline granites, probably representing variable degrees of differentiation of similar parental magmas. Thus CA2 and AL granites do not represent different tectonic settings, but coeval derivation from variable sources during crustal extension. The majority of rocks dated in this study show minor to non-existent zircon inheritance and thus indicate very minor interaction with previously formed felsic crust. The rare zircon xenocrysts span a typical East African age range (900–607 Ma) and confirm the absence of older crustal components in the juvenile Arabian–Nubian Shield.
DOI: 10.6084/m9.figshare.3454580.v1
title: Post-collisional tectonomagmatic evolution in the northern Arabian–Nubian Shield: time constraints from ion-probe U–Pb dating of zircon

description: Ion-probe U–Pb dating of plutonic rocks from the northern Arabian–Nubian Shield in Sinai and southern Israel constrains the timing of late East African batholithic post-collisional calc-alkaline (CA2) magmatism and within-plate alkaline to peralkaline (AL) magmatism to <em>c</em>. 635–590 Ma and <em>c</em>. 608–580 Ma, respectively. The earliest dated CA2 rocks are slightly deformed to undeformed, indicating that penetrative deformation ceased by <em>c</em>. 630 Ma. Within the CA2 suite a change from mafic to felsic magmatism is manifested in most of the region, peaking in a voluminous pulse of granodiorite to granite intrusion at 610–600 Ma. The AL magmatism started contemporaneously with the peak in CA2 felsic activity at <em>c</em>. 608 Ma and lasted until 580 Ma. It includes mostly alkaline and peralkaline granites, probably representing variable degrees of differentiation of similar parental magmas. Thus CA2 and AL granites do not represent different tectonic settings, but coeval derivation from variable sources during crustal extension. The majority of rocks dated in this study show minor to non-existent zircon inheritance and thus indicate very minor interaction with previously formed felsic crust. The rare zircon xenocrysts span a typical East African age range (900–607 Ma) and confirm the absence of older crustal components in the juvenile Arabian–Nubian Shield.
DOI: 10.6084/m9.figshare.3454577
title: Timing of migmatization and granite genesis in the Northwestern Terrane of Svalbard, Norway: implications for regional correlations in the Arctic Caledonides

description: U–Pb ion microprobe investigations of zircons from gneisses, granites and migmatites of the pre-Devonian Smerenburgfjorden and Richarddalen Complexes constrain the tectonic evolution and origin of Svalbard's Northwestern Terrane. Field relationships combined with U–Pb age data indicate that a late Meso- to Neoproterozoic metapelitic protolith was intruded by Tonian (<em>c</em>. 960 Ma) granitoids and suggest that the entire Northwestern Terrane is underlain by early Neoproterozoic granitoids intruding older metasediments. Both rock types were later involved in Caledonian deformation, with subsequent migmatization and granite genesis at <em>c</em>. 435–420 Ma. Ages of inherited zircons in granites and migmatites reflect anatexis of this late Meso- to Neoproterozoic protolith, with zircon xenocrysts ranging in age from <em>c</em>. 1030 to 1820 Ma. Pronounced lithological, geochronological and tectonothermal similarities to NE Svalbard (Nordaustlandet) and the Krummedal supracrustal sequence of East Greenland suggest a strong correlation between Svalbard and East Greenland prior to Caledonian orogenesis.