cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3452891
title: Chapter 41 Geology and petroleum potential of the West Greenland–East Canada Province

description: The US Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the West Greenland–East Canada Province as part of the USGS Circum-Arctic Resource Appraisal programme. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geological basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic–Cenozoic Composite Petroleum System. Potential petroleum source rocks include strata of Ordovician, Lower and Upper Cretaceous, and Palaeogene ages. The five AUs defined for this study – the Eurekan Structures AU, NW Greenland Rifted Margin AU, NE Canada Rifted Margin AU, Baffin Bay Basin AU and the Greater Ungava Fault Zone AU – encompass the entire province and were assessed for undiscovered technically recoverable resources. The mean volumes of undiscovered resources for the West Greenland–East Canada Province are 10.7×10<sup>9</sup> barrels of oil, 75×10<sup>12</sup> cubic feet of gas, and 1.7×10<sup>9</sup> barrels of natural gas liquids. For the part of the province that is north of the Arctic Circle, the estimated mean volumes of these undiscovered resources are 7.3×10<sup>9</sup> barrels of oil, 52×10<sup>12</sup> cubic feet of natural gas, and 1.1×10<sup>9</sup> barrels of natural gas liquids.
DOI: 10.6084/m9.figshare.3452891.v1
title: Chapter 41 Geology and petroleum potential of the West Greenland–East Canada Province

description: The US Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the West Greenland–East Canada Province as part of the USGS Circum-Arctic Resource Appraisal programme. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geological basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic–Cenozoic Composite Petroleum System. Potential petroleum source rocks include strata of Ordovician, Lower and Upper Cretaceous, and Palaeogene ages. The five AUs defined for this study – the Eurekan Structures AU, NW Greenland Rifted Margin AU, NE Canada Rifted Margin AU, Baffin Bay Basin AU and the Greater Ungava Fault Zone AU – encompass the entire province and were assessed for undiscovered technically recoverable resources. The mean volumes of undiscovered resources for the West Greenland–East Canada Province are 10.7×10<sup>9</sup> barrels of oil, 75×10<sup>12</sup> cubic feet of gas, and 1.7×10<sup>9</sup> barrels of natural gas liquids. For the part of the province that is north of the Arctic Circle, the estimated mean volumes of these undiscovered resources are 7.3×10<sup>9</sup> barrels of oil, 52×10<sup>12</sup> cubic feet of natural gas, and 1.1×10<sup>9</sup> barrels of natural gas liquids.
DOI: 10.6084/m9.figshare.3452882
title: Chapter 33 Neoproterozoic glaciogenic diamictites of the Tarim Block, NW China

description: Neoproterozoic glaciogenic outcrops are mostly limited to the southwestern and northwestern margins of the Tarim basin and the Tianshan Mountains. Only two glaciogenic diamictites are recorded in the Neoproterozoic successions from the Tielikeli and Aksu-Wusi areas of the Tarim basin. The lower diamictite from the Polong Formation in the Tielikeli area is <em>c.</em> 800 m thick. The upper diamictite in the area is very thin (Yutang diamictite, 10 m; Yulmeinak diamictite, 51 m). In contrast to the Tarim basin, the Neoproterozoic successions along the northern margin of the Tarim Block in the Tianshan Mountains record three or four glaciogenic diamictites, which are well developed and crop out in the Qurugtagh area. Although the glaciogenic nature of the oldest Beiyixi diamictite remains questionable, all other diamictites (Altungol, Tereeken and Hankalchough) exhibit distinct glaciogenic sedimentary features. SHRIMP zircon U–Pb dating demonstrate that the Bayisi diamictite was deposited between 740±7 Ma and 725±10 Ma, the Altungol and Tereeken diamictites between 725±10 Ma and 615±6 Ma, respectively, and the Hankalchough diamictite between 615±6 Ma and <em>c.</em> 542 Ma. Carbonates atop the Altungol, Tereeken and Hankalchough diamictites show distinct C-isotopic values that are typical for those recorded in ‘cap carbonates’ on other continents. The striking similarity between the cap carbonate of the Tereeken and Marinoan-age Nantuo diamictites further support a 635 Ma ‘Marinoan’ age for the Tereeken glaciation. Unlike the 582 Ma Gaskiers glaciations of Newfoundland, the Hankalchough diamictite is possibly &lt;551 Ma, as suggested by C-isotope chemostratigraphy and biostratigraphy, indicating that post-Marinoan glaciations on different continents may be diachronous.
DOI: 10.6084/m9.figshare.3452882.v1
title: Chapter 33 Neoproterozoic glaciogenic diamictites of the Tarim Block, NW China

description: Neoproterozoic glaciogenic outcrops are mostly limited to the southwestern and northwestern margins of the Tarim basin and the Tianshan Mountains. Only two glaciogenic diamictites are recorded in the Neoproterozoic successions from the Tielikeli and Aksu-Wusi areas of the Tarim basin. The lower diamictite from the Polong Formation in the Tielikeli area is <em>c.</em> 800 m thick. The upper diamictite in the area is very thin (Yutang diamictite, 10 m; Yulmeinak diamictite, 51 m). In contrast to the Tarim basin, the Neoproterozoic successions along the northern margin of the Tarim Block in the Tianshan Mountains record three or four glaciogenic diamictites, which are well developed and crop out in the Qurugtagh area. Although the glaciogenic nature of the oldest Beiyixi diamictite remains questionable, all other diamictites (Altungol, Tereeken and Hankalchough) exhibit distinct glaciogenic sedimentary features. SHRIMP zircon U–Pb dating demonstrate that the Bayisi diamictite was deposited between 740±7 Ma and 725±10 Ma, the Altungol and Tereeken diamictites between 725±10 Ma and 615±6 Ma, respectively, and the Hankalchough diamictite between 615±6 Ma and <em>c.</em> 542 Ma. Carbonates atop the Altungol, Tereeken and Hankalchough diamictites show distinct C-isotopic values that are typical for those recorded in ‘cap carbonates’ on other continents. The striking similarity between the cap carbonate of the Tereeken and Marinoan-age Nantuo diamictites further support a 635 Ma ‘Marinoan’ age for the Tereeken glaciation. Unlike the 582 Ma Gaskiers glaciations of Newfoundland, the Hankalchough diamictite is possibly &lt;551 Ma, as suggested by C-isotope chemostratigraphy and biostratigraphy, indicating that post-Marinoan glaciations on different continents may be diachronous.
DOI: 10.6084/m9.figshare.3452876
title: Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny

description: The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a <em>c</em>. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a <em>c</em>. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at <em>c</em>. 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.
DOI: 10.6084/m9.figshare.3452876.v1
title: Age constraints and geochemistry of the Ordovician Tyrone Igneous Complex, Northern Ireland: implications for the Grampian orogeny

description: The Tyrone Igneous Complex is one of the largest areas of ophiolitic and arc-related rocks exposed along the northern margin of Iapetus within the British and Irish Caledonides. New U–Pb zircon data and regional geochemistry suggest that the Tyrone Plutonic Group represents the uppermost portions of a <em>c</em>. 480 Ma suprasubduction-zone ophiolite accreted onto an outboard segment of Laurentia prior to 470.3 ± 1.9 Ma. The overlying Tyrone Volcanic Group formed as an island arc that collided with the Laurentian margin during the Grampian phase of the Caledonidan orogeny. Early magmatism is characterized by transitional to calc-alkaline, light REE (LREE)-enriched island-arc signatures, with an increasing component of continentally derived material up sequence. Tholeiitic rhyolites with flat to U-shaped REE profiles and LREE-depleted basalts, located stratigraphically below a <em>c</em>. 473 Ma rhyolite of the upper Tyrone Volcanic Group, suggest initiation of intra-arc rifting at <em>c</em>. 475 Ma. Metamorphic cooling ages from the Tyrone Central Inlier imply arc–continent collision before 468 ± 1.4 Ma, with the emplacement of the Tyrone Volcanic Group onto the margin. A suite of 470.3 ± 1.9 Ma to 464.3 ± 1.5 Ma calc-alkaline intrusions are associated with the continued closure of Iapetus.
DOI: 10.17632/3sdss7h6ry.4
title: Data for: Decoding pyroclastic density current flow direction and shear conditions in the flow boundary zone via particle-fabric analysis

description: One of the greatest challenges in volcanology is extracting information from volcanic deposits that inform the conditions at the time of emplacement. Here we explore particle shape-fabric within samples from the column-collapse pyroclastic density current (PDC) deposits generated by the 18 May 1980 eruption of Mt. Saint Helens (MSH). Particle shape-fabric is the mutual alignment of particles within the samples, which is dependent of shearing conditions at the time of deposition. Here, particle shape-fabric is used to address the following hypotheses: (1) particle shape-fabric will align with previous interpretations of PDC flow direction during the 1980 event; (2) samples extracted from PDC deposits immediately above a basal contact will show higher extents of fabric development (i.e. clast alignment) relative to samples extracted well above the contact; and (3) samples extracted from the proximal bedded deposits, located on the steep flanks of the volcano, will have higher extents of fabric development relative to samples extracted from the massive facies found in the gently dipping pumice plain. We find that fabric orientations approximate previous flow direction interpretations well for massive PDC deposits, validating the method of using particle-shape fabric to determine flow direction. However, while samples extracted immediately above the PDC deposit-substrate contact do not show a higher measure of clast alignment relative to samples taken well above flow contacts, the typical clast bimodality suggests some degree of traction transport and thus higher shearing conditions relative to when the currents deposited massive lapilli tuffs. Samples extracted from the proximal bedded deposits do not show higher extents of fabric development relative to the massive deposits, supporting previous interpretations that these deposits formed from a rapidly sedimenting, concentrated flow boundary zone that was thin enough to be frequently interrupted or influenced by the overriding turbulent portion of the flow. Finally, observations of fine scale variability in measured fabric within a single outcrop indicates unsteady flow conditions and step-wise aggradation during deposition. This work demonstrates that particle shape-fabric analyses can aid in decoding PDC flow conditions, and future, complementary experimental work may allow for the extraction of quantitative information regarding the magnitudes of shear within the lower flow boundary zone of PDCs.
DOI: 10.6084/m9.figshare.3452870
title: The growth of the Zimbabwe Craton during the late Archaean: an ion microprobe U–Pb zircon study

description: U–Pb zircon ages obtained by ion microprobe are presented for late Archaean granitoids from the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt. Similar ages of crust formation in the felsic gneisses of the Zimbabwe Craton and the felsic granulites of the North Marginal Zone support the view, previously argued on geological grounds, that they represent the middle and lower crustal layers respectively of the Zimbabwe Craton. Zircons from the southern margin of the Zimbabwe Craton and the northern part of the North Marginal Zone contain old cores, confirming the presence of an old (<em>c</em>. 3.5 Ga) nucleus to the Zimbabwe Craton and indicating that the areal extent of this old nucleus is greater than has been hitherto supposed. Thus late Archaean crustal growth involved both the reworking of and the addition of new magmas to this old crustal nucleus. At 2.7 Ga crustal growth was contemporaneous with plume volcanism in the greenstone belts. In contrast, crustal growth at 2.74, 2.67, 2.64 and ?2.62 Ga was focused at the margins of the ‘old craton' and may be related to Andean style continental margin magmatism. Lower crustal melting at 2.61–2.59 Ga led to the emplacement of granitoids in the upper crust.
DOI: 10.6084/m9.figshare.3452870.v1
title: The growth of the Zimbabwe Craton during the late Archaean: an ion microprobe U–Pb zircon study

description: U–Pb zircon ages obtained by ion microprobe are presented for late Archaean granitoids from the Zimbabwe Craton and the North Marginal Zone of the Limpopo Belt. Similar ages of crust formation in the felsic gneisses of the Zimbabwe Craton and the felsic granulites of the North Marginal Zone support the view, previously argued on geological grounds, that they represent the middle and lower crustal layers respectively of the Zimbabwe Craton. Zircons from the southern margin of the Zimbabwe Craton and the northern part of the North Marginal Zone contain old cores, confirming the presence of an old (<em>c</em>. 3.5 Ga) nucleus to the Zimbabwe Craton and indicating that the areal extent of this old nucleus is greater than has been hitherto supposed. Thus late Archaean crustal growth involved both the reworking of and the addition of new magmas to this old crustal nucleus. At 2.7 Ga crustal growth was contemporaneous with plume volcanism in the greenstone belts. In contrast, crustal growth at 2.74, 2.67, 2.64 and ?2.62 Ga was focused at the margins of the ‘old craton' and may be related to Andean style continental margin magmatism. Lower crustal melting at 2.61–2.59 Ga led to the emplacement of granitoids in the upper crust.
DOI: 10.6084/m9.figshare.3452852.v1
title: Hafnium isotope record of the Ancient Gneiss Complex, Swaziland, southern Africa: evidence for Archaean crust–mantle formation and crust reworking between 3.66 and 2.73 Ga

description: Combined U–Pb and Lu–Hf isotope analyses of zircons from 16 tonalite–trondjemite–granodiorite (TTG) gneiss and granite samples from Swaziland reveal that the oldest rocks of the Ancient Gneiss Complex in southern Africa formed by reworking of Early Archaean or perhaps Late Hadean crust at 3.66 Ga, and that new crust was extracted from a depleted mantle source during Palaeoarchaean events between 3.54 and 3.32 Ga. This interpretation is supported by εHf<sub>t</sub> of −1.6 ± 2.0 obtained from 3.66 Ga TTG gneisses, corresponding to hafnium model ages between 3.77 ± 0.18 Ga, for a presumed Hadean–Early Archaean chondritic mantle, and 4.08 ± 0.18 Ga, for a presumed Hadean depleted mantle reservoir, with the first model age being the most likely in the light of recent data from worldwide sources. Furthermore, it is reflected by superchondritic εHf<sub>t</sub> up to +2.2 ± 2.0 for TTGs formed at 3.54, 3.45 and 3.32 Ga. The new datasets additionally show that the Palaeoarchaean crust formed between 3.54 and 3.32 Ga was intensely reworked afterwards, without significant addition of depleted mantle derived material, during orogenic and intracratonic melting processes at 3.23, 3.1 and 2.7 Ga. This is well reflected by an array of decreasing εHf<sub>t</sub> from +2.2 to −7.2 between 3.3 and 2.7 Ga, which can be forced by <sup>176</sup>Lu/<sup>177</sup>Hf of 0.0113, which is similar to that of present-day average continental crust, and might result from lower crust zircon fractionation during Archaean crust reworking.
DOI: 10.6084/m9.figshare.3452849
title: Oceanic lithospheric mantle beneath the continental crust of the Chinese Altai

description: Although subduction–accretion is proposed as a major regime in making new continental crust, how the lithospheric mantle forms remains unclear. Formed after the closure of the Palaeo-Asian Ocean, the Ashele basalt shows normal mid-ocean ridge basalt (N-MORB)-like characteristics with light REE-depleted patterns and extremely low contents of high field strength elements. The low Zr/Y and Nb/Y ratios of the basalt are significantly different from those of asthenosphere-derived melts, and the excess Eu and Sr suggest that the basalt was probably derived from accreted oceanic lithospheric mantle. The presence of the N-MORB-like terrestrial basalt implies that subduction–accretion is an effective mechanism in building the refractory lithospheric mantle of Phanerozoic continents.
DOI: 10.6084/m9.figshare.3452849.v1
title: Oceanic lithospheric mantle beneath the continental crust of the Chinese Altai

description: Although subduction–accretion is proposed as a major regime in making new continental crust, how the lithospheric mantle forms remains unclear. Formed after the closure of the Palaeo-Asian Ocean, the Ashele basalt shows normal mid-ocean ridge basalt (N-MORB)-like characteristics with light REE-depleted patterns and extremely low contents of high field strength elements. The low Zr/Y and Nb/Y ratios of the basalt are significantly different from those of asthenosphere-derived melts, and the excess Eu and Sr suggest that the basalt was probably derived from accreted oceanic lithospheric mantle. The presence of the N-MORB-like terrestrial basalt implies that subduction–accretion is an effective mechanism in building the refractory lithospheric mantle of Phanerozoic continents.
DOI: 10.6084/m9.figshare.3452843
title: Chapter 21 The Tambien Group, Northern Ethiopia (Tigre)

description: The Tambien Group of northern Ethiopia (Tigre), with probable correlatives in Eritrea, is a 2–3-km-thick siliciclastic–carbonate succession that was deposited in an intra-oceanic arc platform setting within the southern Arabian–Nubian Shield (ANS) area (southern extension of the Nakfa Terrane) of the Mozambique Ocean. Its deposition occurred prior to ocean closure between converging fragments of East and West Gondwana and concomitant structural emergence of the East African Orogen (EAO). The Tambien Group is well exposed and best studied in the Mai Kenetal and Negash synclinoria, where litho- and chemostratigraphy (including δ<sup>13</sup>C<sub>carb</sub>, <sup>87</sup>Sr/<sup>86</sup>Sr) provide the basis for a composite reference section. Two glaciogenic intervals have been suggested from exposures within the Didikama and Matheos Formation in the Negash Synclinorium. No reliable palaeomagnetic data exist to constrain the palaeolatitude of Tambien Group deposition and the southern ANS, but palaeogeographic reconstructions and evaporite pseudomorphs in lower carbonate units (Didikama Formation) imply low to intermediate latitudes (&lt;45°). Integration of available geochronological information (regional magmatism and detrital zircon) suggests <em>c.</em> 775–660 Ma as a plausible window constraining deposition of the prospective glacial intervals. The Tambien Group appears to preserve a coherent chemostratigraphic framework that can be effectively subdivided according to shifts in δ<sup>13</sup>C<sub>carb</sub> polarity [polarity intervals A (+), B (–), C (+), D (–)]. Slates underlying and interstratified with polarity interval A carbonate preserve evidence of extreme chemical weathering that lessened prior to deposition of polarity interval B carbonate. Tambien Group carbonate units have sedimentological characteristics consistent with both shallow and deeper marine depositional settings. The lower prospective glacial interval lacks diagnostic sedimentological evidence of synglacial deposition, but is overlain by negative δ<sup>13</sup>C carbonate (polarity interval B) with sedimentological characteristics consistent with well-documented cap-carbonate successions. The upper prospective glacial interval in the Negash Synclinorium (Matheos Diamictite) best exhibits characteristics consistent with glaciogenic deposition (matrix-supported polymictic clasts, possible dropstones, possible bullet-nosed and striated clasts). In contrast to pericratonic rift margin settings that are common for Cryogenian glaciogenic deposits, palaeogeographic reconstructions for the 775–660 Ma timeframe place northern Ethiopia within an intra-oceanic setting that was likely far removed from cratonic hinterlands. More work on Tambien Group sedimentology, geochronology and palaeogeography is required to better evaluate the extent and timing of glacial conditions associated with the prospective glaciogenic intervals.