cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453545
title: Retrogression of eclogite-facies shear zones by short-lived fluid infiltration during the Caledonian orogeny, Lofoten islands, Norway

description: Norwegian eclogite-facies shear zones in the Lofoten islands served as major pathways for short-lived pulses of both <sup>40</sup>Ar-rich and <sup>40</sup>Ar-poor hot fluids during eclogitization and retrogression events related to the Caledonian orogeny. The open system for Ar affected most of the minerals leading to old <sup>40</sup>Ar/<sup>39</sup>Ar ages, particularly in trioctahedral micas. <sup>40</sup>Ar concentration in the fluids appears to decrease during the amphibolite-facies retrogression and Ca-rich amphiboles yield <sup>40</sup>Ar/<sup>39</sup>Ar ages of <em>c.</em> 415 Ma (Scandian event). Late- and post-Caledonian <sup>40</sup>Ar/<sup>39</sup>Ar muscovite and K-feldspar ages and Rb/Sr biotite ages coincide with multiple extensional events, fluid infiltration and thermal activity during the final exhumation of the crustal rocks, potentially reflecting major tectonic episodes such as rifting of Pangaea and seafloor spreading between Europe and North America.
DOI: 10.6084/m9.figshare.3453545.v1
title: Retrogression of eclogite-facies shear zones by short-lived fluid infiltration during the Caledonian orogeny, Lofoten islands, Norway

description: Norwegian eclogite-facies shear zones in the Lofoten islands served as major pathways for short-lived pulses of both <sup>40</sup>Ar-rich and <sup>40</sup>Ar-poor hot fluids during eclogitization and retrogression events related to the Caledonian orogeny. The open system for Ar affected most of the minerals leading to old <sup>40</sup>Ar/<sup>39</sup>Ar ages, particularly in trioctahedral micas. <sup>40</sup>Ar concentration in the fluids appears to decrease during the amphibolite-facies retrogression and Ca-rich amphiboles yield <sup>40</sup>Ar/<sup>39</sup>Ar ages of <em>c.</em> 415 Ma (Scandian event). Late- and post-Caledonian <sup>40</sup>Ar/<sup>39</sup>Ar muscovite and K-feldspar ages and Rb/Sr biotite ages coincide with multiple extensional events, fluid infiltration and thermal activity during the final exhumation of the crustal rocks, potentially reflecting major tectonic episodes such as rifting of Pangaea and seafloor spreading between Europe and North America.
DOI: 10.6084/m9.figshare.3453542
title: A genetic link between silicic slab components and calc-alkaline arc volcanism in central Mexico

description: A fundamental question in the formation of orogenic andesites is whether their high melt SiO<sub>2</sub> reflects the recycling of silicic melts from the subducted slab or the processing of basaltic mantle melts in the overlying crust. The latter model is widely favoured, because most arc magmas lack the ‘garnet’ signature of partial slab melts. Here we present new trace element data from Holocene high-Mg# &gt;64–72 calc-alkaline basalts to andesites (50–62 wt% SiO<sub>2</sub>) from the central Mexican Volcanic Belt that crystallize high-Ni olivines with the high <sup>3</sup>He/<sup>4</sup>He=7–8 of the upper mantle. These magmas have been proposed to be partial melts from ‘reaction pyroxenites’, which formed by hybridization of mantle peridotite (<em>c.</em> 82–85%) and heavy rare earth element-depleted silicic slab melt (&gt;15–18%). Forward and inverse models suggest that the absence of a garnet signature in these melts reflects the efficient buffering of the heavy rare earth elements (Ho to Lu) in the subarc mantle. In contrast, all elements more incompatible than Ho – excepting TiO<sub>2</sub> – are more or less strongly controlled by the silicic slab flux that also directly contributes to the silicic arc magma formation. Our study emphasizes the strong link between slab recycling and the genesis of orogenic andesites.
DOI: 10.6084/m9.figshare.3453542.v1
title: A genetic link between silicic slab components and calc-alkaline arc volcanism in central Mexico

description: A fundamental question in the formation of orogenic andesites is whether their high melt SiO<sub>2</sub> reflects the recycling of silicic melts from the subducted slab or the processing of basaltic mantle melts in the overlying crust. The latter model is widely favoured, because most arc magmas lack the ‘garnet’ signature of partial slab melts. Here we present new trace element data from Holocene high-Mg# &gt;64–72 calc-alkaline basalts to andesites (50–62 wt% SiO<sub>2</sub>) from the central Mexican Volcanic Belt that crystallize high-Ni olivines with the high <sup>3</sup>He/<sup>4</sup>He=7–8 of the upper mantle. These magmas have been proposed to be partial melts from ‘reaction pyroxenites’, which formed by hybridization of mantle peridotite (<em>c.</em> 82–85%) and heavy rare earth element-depleted silicic slab melt (&gt;15–18%). Forward and inverse models suggest that the absence of a garnet signature in these melts reflects the efficient buffering of the heavy rare earth elements (Ho to Lu) in the subarc mantle. In contrast, all elements more incompatible than Ho – excepting TiO<sub>2</sub> – are more or less strongly controlled by the silicic slab flux that also directly contributes to the silicic arc magma formation. Our study emphasizes the strong link between slab recycling and the genesis of orogenic andesites.
DOI: 10.6084/m9.figshare.3453536
title: Evolution of volcanism and magmatism during initial arc stage: constraints on the tectonic setting of the Oman Ophiolite

description: Based on detailed stratigraphy, petrology and geochemistry, the initial arc magmatism of the Oman Ophiolite consisting of tholeiitic lavas followed by boninite flows and tephras is studied in the Wadi Bidi area, northern Oman Mountains. An 1110-m-thick V2 sequence is divided into the lower 970 m (LV2) and upper 140 m (UV2) thick subsequences by a 1.0-m-thick sedimentary layer. Pahoehoe flows dominate in the lower part of the LV2, while the upper part consists mainly of sheet flows with sparse interbedded pelagic sediments and a cylindrical plug. In addition to the presence of a feeder conduit, the flow-dominant lithofacies with a few thin sedimentary interbeds in the LV2 indicates that the study area was the centre of a volcano grown in a short period. The UV2 is composed of boninite sheet flows overlain by a 2.0-m-thick pyroclastic fall deposit. A small amount of boninite lavas at the end of the V2 sequence overlain by thick pelagic sediments suggests that the subduction-related arc volcanism was short lived and terminated long before the ophiolite obduction.
DOI: 10.6084/m9.figshare.3453536.v1
title: Evolution of volcanism and magmatism during initial arc stage: constraints on the tectonic setting of the Oman Ophiolite

description: Based on detailed stratigraphy, petrology and geochemistry, the initial arc magmatism of the Oman Ophiolite consisting of tholeiitic lavas followed by boninite flows and tephras is studied in the Wadi Bidi area, northern Oman Mountains. An 1110-m-thick V2 sequence is divided into the lower 970 m (LV2) and upper 140 m (UV2) thick subsequences by a 1.0-m-thick sedimentary layer. Pahoehoe flows dominate in the lower part of the LV2, while the upper part consists mainly of sheet flows with sparse interbedded pelagic sediments and a cylindrical plug. In addition to the presence of a feeder conduit, the flow-dominant lithofacies with a few thin sedimentary interbeds in the LV2 indicates that the study area was the centre of a volcano grown in a short period. The UV2 is composed of boninite sheet flows overlain by a 2.0-m-thick pyroclastic fall deposit. A small amount of boninite lavas at the end of the V2 sequence overlain by thick pelagic sediments suggests that the subduction-related arc volcanism was short lived and terminated long before the ophiolite obduction.
DOI: 10.6084/m9.figshare.3453533
title: Origin and significance of intra-basement seismic reflections offshore western Norway

description: We use 3D seismic data to image a series of enigmatic, SW-dipping reflection packets within pre-Mesozoic crystalline basement offshore western Norway. Based on their low-angle dip and complex reflection wave-train our preferred interpretation is that the reflection packets are the seismic expression of mylonitic zones generated by nappe emplacement during the Caledonian orogeny. Late Jurassic faults truncate and offset these reflection packets by several hundred metres, suggesting that these faults did not exploit pre-existing basement weaknesses. Our observations suggest that older basement fabrics may not always play a significant role in determining the geometry of later fault systems.
DOI: 10.6084/m9.figshare.3453533.v1
title: Origin and significance of intra-basement seismic reflections offshore western Norway

description: We use 3D seismic data to image a series of enigmatic, SW-dipping reflection packets within pre-Mesozoic crystalline basement offshore western Norway. Based on their low-angle dip and complex reflection wave-train our preferred interpretation is that the reflection packets are the seismic expression of mylonitic zones generated by nappe emplacement during the Caledonian orogeny. Late Jurassic faults truncate and offset these reflection packets by several hundred metres, suggesting that these faults did not exploit pre-existing basement weaknesses. Our observations suggest that older basement fabrics may not always play a significant role in determining the geometry of later fault systems.
DOI: 10.6084/m9.figshare.3453530
title: Element concentrations in granitic magmas: ghosts of textures past?

description: The geochemistry of granitic rocks appears to contain information about some aspects of the pre-anatectic textures of the protoliths. There are marked contrasts in the covariations between Ba (a proxy for melting proportion in the protolith) and the P<sub>2</sub>O<sub>5</sub>, TiO<sub>2</sub>, Y, Zr and Ce concentrations in I- and S-type granitic magmas (rocks). These contrasts are interpreted as features resulting from the interplay between differences in the locations of accessory mineral grains in the protoliths, their solubilities in the granitic melts and the degree of foliation developed in the protoliths. It is inferred that S-type protoliths are more highly foliated, with accessory minerals concentrated into the biotite-rich layers that form the foci for partial melting. I-type protoliths appear to have less pronounced foliation and a more random distribution of both hydrous mafic silicates and accessory grains.
DOI: 10.6084/m9.figshare.3453530.v1
title: Element concentrations in granitic magmas: ghosts of textures past?

description: The geochemistry of granitic rocks appears to contain information about some aspects of the pre-anatectic textures of the protoliths. There are marked contrasts in the covariations between Ba (a proxy for melting proportion in the protolith) and the P<sub>2</sub>O<sub>5</sub>, TiO<sub>2</sub>, Y, Zr and Ce concentrations in I- and S-type granitic magmas (rocks). These contrasts are interpreted as features resulting from the interplay between differences in the locations of accessory mineral grains in the protoliths, their solubilities in the granitic melts and the degree of foliation developed in the protoliths. It is inferred that S-type protoliths are more highly foliated, with accessory minerals concentrated into the biotite-rich layers that form the foci for partial melting. I-type protoliths appear to have less pronounced foliation and a more random distribution of both hydrous mafic silicates and accessory grains.
DOI: 10.6084/m9.figshare.3453527
title: Magma genesis controlled by tectonic styles in the northern part of the Arabia plate during Cenozoic time

description: Widespread lava fields in the northern part of the Arabian platform are the subject of an open geodynamic debate on the origin of the intraplate volcanism. We present new K–Ar ages and whole-rock geochemical data for lava flows from Syria, which allow us to propose a new model of volcano-tectonic evolution highlighting how tectonics have controlled magma genesis in the region during the last 18 Ma. The Cenozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma erupted in such a continental intraplate context. Basaltic samples from different Syrian volcanic provinces show significant variations in terms of incompatible trace element signatures. Crustal contamination plays a negligible role during magma migration and differentiation, and crystal fractionation is essentially restricted to olivine and clinopyroxene. Our results suggest that the Syrian lavas have been generated by variable degrees of partial melting (<em>c.</em> 1–10%) from different levels of a locally heterogeneous lithospheric mantle. The light/medium rare Earth element (LREE/MREE) ratios not only illustrate how the degree of partial melting has changed spatially and temporally during the last <em>c.</em> 18 Ma, but also indicate that the degree and the style of extensional tectonics has changed through time. We conclude that the Cenozoic Syrian volcanism is a consequence of extensional tectonics, under periodical influence of the north- and eastwards convergence at the Arabia–Eurasia margin, which induces rotational tectonic styles. This controls the partial melting at various depths in the mantle. The volcanism of northern Arabia developed in the framework of the Red Sea rifting and initiated at the same time as the southern Red Sea volcanism. It extends up to historical time, progressively smoothed to the north in a contradictory relation with the compressional/extensional setting of the Arabia–Eurasia margin.
DOI: 10.6084/m9.figshare.3453527.v1
title: Magma genesis controlled by tectonic styles in the northern part of the Arabia plate during Cenozoic time

description: Widespread lava fields in the northern part of the Arabian platform are the subject of an open geodynamic debate on the origin of the intraplate volcanism. We present new K–Ar ages and whole-rock geochemical data for lava flows from Syria, which allow us to propose a new model of volcano-tectonic evolution highlighting how tectonics have controlled magma genesis in the region during the last 18 Ma. The Cenozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma erupted in such a continental intraplate context. Basaltic samples from different Syrian volcanic provinces show significant variations in terms of incompatible trace element signatures. Crustal contamination plays a negligible role during magma migration and differentiation, and crystal fractionation is essentially restricted to olivine and clinopyroxene. Our results suggest that the Syrian lavas have been generated by variable degrees of partial melting (<em>c.</em> 1–10%) from different levels of a locally heterogeneous lithospheric mantle. The light/medium rare Earth element (LREE/MREE) ratios not only illustrate how the degree of partial melting has changed spatially and temporally during the last <em>c.</em> 18 Ma, but also indicate that the degree and the style of extensional tectonics has changed through time. We conclude that the Cenozoic Syrian volcanism is a consequence of extensional tectonics, under periodical influence of the north- and eastwards convergence at the Arabia–Eurasia margin, which induces rotational tectonic styles. This controls the partial melting at various depths in the mantle. The volcanism of northern Arabia developed in the framework of the Red Sea rifting and initiated at the same time as the southern Red Sea volcanism. It extends up to historical time, progressively smoothed to the north in a contradictory relation with the compressional/extensional setting of the Arabia–Eurasia margin.
DOI: 10.6084/m9.figshare.3453521
title: A kilometre-scale highly refractory harzburgite zone in the mantle section of the northern Oman Ophiolite (Fizh Block): implications for flux melting of oceanic lithospheric mantle

description: We report the major element compositions of constituent minerals in 278 harzburgites and of 101 whole rocks from the northern Fizh mantle section in the northern Oman Ophiolite to investigate the formation and evolution of oceanic lithospheric mantle. Olivine Fo varies from 90 to 92 whereas spinel Cr# (= Cr/(Cr+Al) atomic ratio) varies from 0.15 to 0.78. The Cr# of spinels in a large number of harzburgites exceeds 0.6, which is the upper bound for abyssal peridotites. In the northern Fizh mantle section, highly refractory harzburgites with spinel Cr# greater than 0.7 are distributed in a 3-km-wide band along a NW–SE-striking shear zone. We infer a two-stage depletion process in the northern Fizh mantle section. In the first stage, asthenospheric mantle was partially melted beneath a mid-ocean ridge, producing a harzburgitic residual column. In the second stage during detachment of oceanic lithosphere an H<sub>2</sub>O-rich fluid, released from the metamorphic sole due to thermal metamorphism of altered oceanic crust, extensively infiltrated the northern Fizh mantle section where the ridge segment boundary region was previously located. The residual harzburgites were subjected to flux melting, resulting in a highly refractory harzburgite zone with spinel Cr# greater than 0.7.
DOI: 10.6084/m9.figshare.3453521.v1
title: A kilometre-scale highly refractory harzburgite zone in the mantle section of the northern Oman Ophiolite (Fizh Block): implications for flux melting of oceanic lithospheric mantle

description: We report the major element compositions of constituent minerals in 278 harzburgites and of 101 whole rocks from the northern Fizh mantle section in the northern Oman Ophiolite to investigate the formation and evolution of oceanic lithospheric mantle. Olivine Fo varies from 90 to 92 whereas spinel Cr# (= Cr/(Cr+Al) atomic ratio) varies from 0.15 to 0.78. The Cr# of spinels in a large number of harzburgites exceeds 0.6, which is the upper bound for abyssal peridotites. In the northern Fizh mantle section, highly refractory harzburgites with spinel Cr# greater than 0.7 are distributed in a 3-km-wide band along a NW–SE-striking shear zone. We infer a two-stage depletion process in the northern Fizh mantle section. In the first stage, asthenospheric mantle was partially melted beneath a mid-ocean ridge, producing a harzburgitic residual column. In the second stage during detachment of oceanic lithosphere an H<sub>2</sub>O-rich fluid, released from the metamorphic sole due to thermal metamorphism of altered oceanic crust, extensively infiltrated the northern Fizh mantle section where the ridge segment boundary region was previously located. The residual harzburgites were subjected to flux melting, resulting in a highly refractory harzburgite zone with spinel Cr# greater than 0.7.
DOI: 10.6084/m9.figshare.3453512
title: Detrital zircon U–Pb–Hf systematics of Israeli coastal sands: new perspectives on the provenance of Nile sediments

description: The Nile drains a large basin covering various source-rock terrains of different age, mineralogical and isotopic characteristics. Its sediments are stored within the Nile delta but significant volumes are swept eastwards in the SE Mediterranean, onto the Sinai–Israeli coasts. Alongside wave transport, aeolian transport plays an important role in recycling the Nile-derived sands. We present new laser ablation inductively coupled plasma mass spectrometry, 882 U–Pb and 586 Lu–Hf analyses of detrital zircons from Quaternary to Recent sands of the Israeli coast and shelf to decipher their provenance. The detrital populations are dominated by 0.56–1.15 Ga zircons with ϵHf(t) of +13 to −27, implying a mixture of juvenile and non-juvenile latest Mesoproterozoic to Neoproterozoic sources. Small populations of Archaean–Palaeoproterozoic and Palaeozoic zircons are also distinguished. The detrital zircon U–Pb–Hf pattern indicates that rather than being sourced from the Arabian–Nubian Shield or older basement terranes in the Nile drainage basin, the sands are dominantly recycling products of older sediments. The detrital zircon U–Pb–Hf spectra resemble those of Cambro-Ordovician sandstones that blanket much of North Africa. These sediments were recycled into younger sand reservoirs that were in turn eroded into the Nile and transported to the coast of Israel.
DOI: 10.6084/m9.figshare.3453512.v1
title: Detrital zircon U–Pb–Hf systematics of Israeli coastal sands: new perspectives on the provenance of Nile sediments

description: The Nile drains a large basin covering various source-rock terrains of different age, mineralogical and isotopic characteristics. Its sediments are stored within the Nile delta but significant volumes are swept eastwards in the SE Mediterranean, onto the Sinai–Israeli coasts. Alongside wave transport, aeolian transport plays an important role in recycling the Nile-derived sands. We present new laser ablation inductively coupled plasma mass spectrometry, 882 U–Pb and 586 Lu–Hf analyses of detrital zircons from Quaternary to Recent sands of the Israeli coast and shelf to decipher their provenance. The detrital populations are dominated by 0.56–1.15 Ga zircons with ϵHf(t) of +13 to −27, implying a mixture of juvenile and non-juvenile latest Mesoproterozoic to Neoproterozoic sources. Small populations of Archaean–Palaeoproterozoic and Palaeozoic zircons are also distinguished. The detrital zircon U–Pb–Hf pattern indicates that rather than being sourced from the Arabian–Nubian Shield or older basement terranes in the Nile drainage basin, the sands are dominantly recycling products of older sediments. The detrital zircon U–Pb–Hf spectra resemble those of Cambro-Ordovician sandstones that blanket much of North Africa. These sediments were recycled into younger sand reservoirs that were in turn eroded into the Nile and transported to the coast of Israel.
DOI: 10.6084/m9.figshare.3453506
title: U–Pb zircon provenance of Moldanubian metasediments in the Bohemian Massif

description: Detrital zircon U–Pb age data from the Moldanubian part of the Bohemian Massif obtained by laser ablation inductively coupled plasma mass spectrometry show variations between the lithotectonic units and point to their formation in spatially close but separated basins that were supplied by detritus from somewhat different source areas, possibly over different periods of time. The youngest detrital zircon component in metasediments of the Monotonous and Varied Units is Early Ordovician and Mid- to Late Devonian in age, respectively, suggesting their deposition in Palaeozoic times. Reliable interpretation of the Mid- to Late Devonian zircons recovered from metasediments of the Gföhl Unit is precluded by their high metamorphic grade and presence of anatectic melt. The Early Carboniferous zircons from the Gföhl Unit are interpreted as being of metamorphic origin. Comparison of detrital zircon age spectra from the Moldanubian, Teplá–Barrandian and Moravo-Silesian metasediments suggests that these were deposited in separate basins but the overall similarity of the Neoproterozoic and Palaeoproterozoic age maxima and sparse Neo- and Mesoarchaean ages suggest that the three crustal segments must have been spatially related prior to the Variscan orogeny. Future tectonic models of the Variscan assembly of the Bohemian Massif must account for nearly synchronous evolution of the Moldanubian, Teplá–Barrandian and Moravo-Silesian Palaeozoic sedimentary basins that shared a common crust and most of their sedimentary sources, as well as for a rapid burial of the Moldanubian sediments to mid- and lower crustal levels that was followed by their rapid exhumation to the upper crust in Mid-Devonian to Early Carboniferous times.