cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453443
title: Tectonic reconstruction and sediment provenance of a far-travelled oceanic nappe, Helgeland Nappe Complex, west-central Norway

description: The Helgeland Nappe Complex (HNC), part of the Uppermost Allochthon of the north-central Norwegian Caledonides, originated near the Laurentian margin and was transferred to Baltica during the closure of Iapetus in Late Silurian–Early Devonian time. The islands of Rødøy, Bolvær and Leka, located in the Sauren–Torghatten (S–T) nappe of the HNC, are composed of ultramafic and mafic basement rocks unconformably overlain by metaconglomerates and fine-grained metasedimentary rocks. Geochemical and isotopic characteristics of the basement rocks are consistent with formation in a supra-subduction zone setting. Overlying metasedimentary rocks record an increasing proportion of continental detritus supplied to the basins through time. Precambrian cratonic source regions supplied cobbles and other detritus. This source area may have been located in modern SE Greenland/Labrador or in the Lower Nappe of the HNC. The second alternative best accounts for the short transport distances required by the coarse-grained conglomerates. The maximum age of deposition is constrained by the age of the youngest zircon grain dated at 471±8 Ma. Final sedimentation, nappe thrusting and nappe stacking occurred in rapid succession during <em>c.</em> 480–475 Ma.
DOI: 10.6084/m9.figshare.3453437
title: Constraining depositional models in the Barents Sea region using detrital zircon U–Pb data from Mesozoic sediments in Svalbard

description: Detrital zircon U–Pb laser ablation inductively coupled plasma mass spectrometry age data on sandstones from Mesozoic successions on Svalbard are used to investigate provenance changes over time, constrain potential source areas, and to test and refine previous interpretations of the Mesozoic filling of the Barents Sea. The zircon age data indicate a western Laurentian (North Greenland) source in the Early and Middle Triassic. The westerly derived sediments most likely include reworked older sediments with proto-sources in Canada and Greenland. Sediments reaching Svalbard in the Late Triassic display a distinct Uralide signature that demonstrates derivation from the east. Zircon age populations in Late Triassic–Early Jurassic sands suggest mixing of zircons from the Early and Middle Triassic and Late Triassic sediments; the data are interpreted to reflect reworking of older Mesozoic sands and possible renewed input of sediments from the west. The data thus demonstrate a shift from westerly to easterly sediment sources in the early Late Triassic. The Early and Middle Triassic zircon age signature in this study appears to resurface in published Early Cretaceous provenance data from Svalbard, suggesting that sediment input from the east ceased during the Jurassic, and shifted back to westerly sources.
DOI: 10.6084/m9.figshare.3453437.v1
title: Constraining depositional models in the Barents Sea region using detrital zircon U–Pb data from Mesozoic sediments in Svalbard

description: Detrital zircon U–Pb laser ablation inductively coupled plasma mass spectrometry age data on sandstones from Mesozoic successions on Svalbard are used to investigate provenance changes over time, constrain potential source areas, and to test and refine previous interpretations of the Mesozoic filling of the Barents Sea. The zircon age data indicate a western Laurentian (North Greenland) source in the Early and Middle Triassic. The westerly derived sediments most likely include reworked older sediments with proto-sources in Canada and Greenland. Sediments reaching Svalbard in the Late Triassic display a distinct Uralide signature that demonstrates derivation from the east. Zircon age populations in Late Triassic–Early Jurassic sands suggest mixing of zircons from the Early and Middle Triassic and Late Triassic sediments; the data are interpreted to reflect reworking of older Mesozoic sands and possible renewed input of sediments from the west. The data thus demonstrate a shift from westerly to easterly sediment sources in the early Late Triassic. The Early and Middle Triassic zircon age signature in this study appears to resurface in published Early Cretaceous provenance data from Svalbard, suggesting that sediment input from the east ceased during the Jurassic, and shifted back to westerly sources.
DOI: 10.6084/m9.figshare.3453428
title: Using detrital garnet compositions to determine provenance: a new compositional database and procedure

description: Detrital garnet compositions can be used to help determine the provenance of sedimentary rocks. In this study a garnet compositional database consisting of more than 2500 wet chemical and electron microprobe analyses was compiled from the literature. For the garnets in the database the six principal garnet end-member compositions (pyrope, almandine, spessartine, uvarovite, grossular and andradite) were calculated. A multi-stage methodology was devised to match garnet compositions to source rocks, and a series of garnet provenance fields on ternary plots were identified. The method was tested using compositional data from detrital garnet studies in several areas where provenance has already been identified, with good results. The methodology was then used to assess the provenance of detrital garnets from Neogene sandstones of northern Sabah, Borneo for which provenance is unknown and in a region where there are few garnet analyses for comparison. Comparison of garnet compositions from possible sources on Palawan, Philippines and in Borneo combined with the ternary plots excludes some known garnet-bearing rocks as potential sources and suggests derivation of metamorphic and igneous garnets from Palawan during the Early Miocene.
DOI: 10.6084/m9.figshare.3453428.v1
title: Using detrital garnet compositions to determine provenance: a new compositional database and procedure

description: Detrital garnet compositions can be used to help determine the provenance of sedimentary rocks. In this study a garnet compositional database consisting of more than 2500 wet chemical and electron microprobe analyses was compiled from the literature. For the garnets in the database the six principal garnet end-member compositions (pyrope, almandine, spessartine, uvarovite, grossular and andradite) were calculated. A multi-stage methodology was devised to match garnet compositions to source rocks, and a series of garnet provenance fields on ternary plots were identified. The method was tested using compositional data from detrital garnet studies in several areas where provenance has already been identified, with good results. The methodology was then used to assess the provenance of detrital garnets from Neogene sandstones of northern Sabah, Borneo for which provenance is unknown and in a region where there are few garnet analyses for comparison. Comparison of garnet compositions from possible sources on Palawan, Philippines and in Borneo combined with the ternary plots excludes some known garnet-bearing rocks as potential sources and suggests derivation of metamorphic and igneous garnets from Palawan during the Early Miocene.
DOI: 10.6084/m9.figshare.3453425
title: Zircon U–Pb and Hf – isotopes from the eastern part of the Sveconorwegian Orogen, SW Sweden: implications for the growth of Fennoscandia

description: Current models for the growth of Fennoscandia, including the eastern part of the Sveconorwegian Province, are largely based on U–Pb data and do not discriminate between juvenile and reworked crust. Here we present new combined U–Pb and Hf isotopic data, from the Eastern Segment and the Idefjorden terrane of the Sveconorwegian Province, and suggest a revised model of crustal growth. Most of the crystalline basement in this part of the shield formed by mixing of a 2.1–1.9 Ga juvenile component and Archaean crust. Archaean reworking decreases between 1.9 and 1.7 Ga and a mixed Svecofennian crustal reservoir is generated. Succeeding magmatism between 1.7 and 1.4 Ga indicates reworking of this reservoir with little or no crust generation. At <em>c.</em> 1.2 Ga, an influx of juvenile magma is recorded by granite to quartz-syenite magmatism with mildly depleted (ε<sub>Hf 1.18 Ga</sub> of <em>c.</em> 3) signatures. The amount of recycled crust in the 1.9–1.7 Ga arc system is in contrast to previously proposed models for the growth of the southwestern part of the Fennoscandian Shield. This model agrees with long-term subduction along the western margin of Fennoscandia, but suggests substantial reworking of existing crust and decreasing amounts of &lt;1.9 Ga crustal growth.
DOI: 10.6084/m9.figshare.3453425.v1
title: Zircon U–Pb and Hf – isotopes from the eastern part of the Sveconorwegian Orogen, SW Sweden: implications for the growth of Fennoscandia

description: Current models for the growth of Fennoscandia, including the eastern part of the Sveconorwegian Province, are largely based on U–Pb data and do not discriminate between juvenile and reworked crust. Here we present new combined U–Pb and Hf isotopic data, from the Eastern Segment and the Idefjorden terrane of the Sveconorwegian Province, and suggest a revised model of crustal growth. Most of the crystalline basement in this part of the shield formed by mixing of a 2.1–1.9 Ga juvenile component and Archaean crust. Archaean reworking decreases between 1.9 and 1.7 Ga and a mixed Svecofennian crustal reservoir is generated. Succeeding magmatism between 1.7 and 1.4 Ga indicates reworking of this reservoir with little or no crust generation. At <em>c.</em> 1.2 Ga, an influx of juvenile magma is recorded by granite to quartz-syenite magmatism with mildly depleted (ε<sub>Hf 1.18 Ga</sub> of <em>c.</em> 3) signatures. The amount of recycled crust in the 1.9–1.7 Ga arc system is in contrast to previously proposed models for the growth of the southwestern part of the Fennoscandian Shield. This model agrees with long-term subduction along the western margin of Fennoscandia, but suggests substantial reworking of existing crust and decreasing amounts of &lt;1.9 Ga crustal growth.
DOI: 10.6084/m9.figshare.3453422
title: Insights into the early Tibetan Plateau from (U–Th)/He thermochronology

description: The central Songpan–Ganzi belt, located on the eastern margin of the Tibetan Plateau, has a similar high elevation and low relief to parts of central Tibet. Thermochronological studies from the central Tibetan Plateau reveal a history of slow exhumation (rates &lt;0.05kmMa<sup>−1</sup>) since 45Ma; however, the exhumation history of the central Songpan–Ganzi belt is unknown. To address this, we conducted an apatite and zircon (U–Th)/He thermochronology study of bedrock samples collected across the central Songpan–Ganzi belt and into central parts of the Tibetan Plateau. Zircon (U–Th)/He ages range from 54.2±7.5 to 146.5±10.0Ma and the majority of apatite (U–Th)/He ages fall between 74.7±19.0 and 35.7±9.4Ma. Thermal history models of these data show rapid cooling in the late Mesozoic and much slower cooling diagnostic of low rates of erosion throughout most of the Cenozoic. The late Mesozoic rapid cooling is consistent with the existence of significant topography and relief at least in some parts of the Songpan–Ganzi belt at that time. We find no evidence for a regional Miocene acceleration in erosion, although three samples from the headwaters of the Salween and Mekong rivers gave younger AHe ages between 15 and 16Ma that reflect an acceleration in river incision.
DOI: 10.6084/m9.figshare.3453422.v1
title: Insights into the early Tibetan Plateau from (U–Th)/He thermochronology

description: The central Songpan–Ganzi belt, located on the eastern margin of the Tibetan Plateau, has a similar high elevation and low relief to parts of central Tibet. Thermochronological studies from the central Tibetan Plateau reveal a history of slow exhumation (rates &lt;0.05kmMa<sup>−1</sup>) since 45Ma; however, the exhumation history of the central Songpan–Ganzi belt is unknown. To address this, we conducted an apatite and zircon (U–Th)/He thermochronology study of bedrock samples collected across the central Songpan–Ganzi belt and into central parts of the Tibetan Plateau. Zircon (U–Th)/He ages range from 54.2±7.5 to 146.5±10.0Ma and the majority of apatite (U–Th)/He ages fall between 74.7±19.0 and 35.7±9.4Ma. Thermal history models of these data show rapid cooling in the late Mesozoic and much slower cooling diagnostic of low rates of erosion throughout most of the Cenozoic. The late Mesozoic rapid cooling is consistent with the existence of significant topography and relief at least in some parts of the Songpan–Ganzi belt at that time. We find no evidence for a regional Miocene acceleration in erosion, although three samples from the headwaters of the Salween and Mekong rivers gave younger AHe ages between 15 and 16Ma that reflect an acceleration in river incision.
DOI: 10.6084/m9.figshare.3453419
title: Evolution of the Tyrone ophiolite, Northern Ireland, during the Grampian–Taconic orogeny: a correlative of the Annieopsquotch Ophiolite Belt of central Newfoundland?

description: The Tyrone Plutonic Group of Northern Ireland represents the upper portions of a tectonically dissected suprasubduction-zone ophiolite accreted to the composite Laurentian margin during the Middle Ordovician. Understanding its development and relationship to the Tyrone Central Inlier, an outboard fragment of relatively high-grade, peri-Laurentian continental crust, is essential for reconstructing the closure of the Iapetus Ocean. The Tyrone Plutonic Group is composed of tectonized layered, isotropic and pegmatitic gabbros, sheeted dolerite dykes and rare pillow lavas. New U–Pb zircon thermal ionization mass spectrometry geochronology has yielded an age of 483.68 ± 0.81 Ma from pegmatitic gabbro. Geochemical characteristics, Nd and Sr isotope systematics, and zircon inheritance indicate that the Tyrone Plutonic Group formed above a north-dipping subduction zone, by the propagation of a spreading centre into a microcontinental block. Synkinematic, calc-alkaline tonalitic to granitic material preserved in the contact zone between the Tyrone Plutonic Group and the Tyrone Central Inlier has produced pressure estimates of 2.3–4.0 ± 0.6 kbar and temperatures of 525–610 °C. Coeval arc–ophiolite accretion at <em>c</em>. 470 Ma may explain how sillimanite-grade metamorphic conditions were reached locally in the underlying Tyrone Central Inlier. Strong temporal, geochemical and lithological similarities exist to the Annieopsquotch Ophiolite Belt of Newfoundland.
DOI: 10.6084/m9.figshare.3453419.v1
title: Evolution of the Tyrone ophiolite, Northern Ireland, during the Grampian–Taconic orogeny: a correlative of the Annieopsquotch Ophiolite Belt of central Newfoundland?

description: The Tyrone Plutonic Group of Northern Ireland represents the upper portions of a tectonically dissected suprasubduction-zone ophiolite accreted to the composite Laurentian margin during the Middle Ordovician. Understanding its development and relationship to the Tyrone Central Inlier, an outboard fragment of relatively high-grade, peri-Laurentian continental crust, is essential for reconstructing the closure of the Iapetus Ocean. The Tyrone Plutonic Group is composed of tectonized layered, isotropic and pegmatitic gabbros, sheeted dolerite dykes and rare pillow lavas. New U–Pb zircon thermal ionization mass spectrometry geochronology has yielded an age of 483.68 ± 0.81 Ma from pegmatitic gabbro. Geochemical characteristics, Nd and Sr isotope systematics, and zircon inheritance indicate that the Tyrone Plutonic Group formed above a north-dipping subduction zone, by the propagation of a spreading centre into a microcontinental block. Synkinematic, calc-alkaline tonalitic to granitic material preserved in the contact zone between the Tyrone Plutonic Group and the Tyrone Central Inlier has produced pressure estimates of 2.3–4.0 ± 0.6 kbar and temperatures of 525–610 °C. Coeval arc–ophiolite accretion at <em>c</em>. 470 Ma may explain how sillimanite-grade metamorphic conditions were reached locally in the underlying Tyrone Central Inlier. Strong temporal, geochemical and lithological similarities exist to the Annieopsquotch Ophiolite Belt of Newfoundland.
DOI: 10.6084/m9.figshare.3453416
title: Pulling apart the Mid to Late Cenozoic magmatic record of the Gulf of California: is there a Comondú Arc?

description: The composition of the lithosphere can be fundamentally altered by long-lived subduction processes such that subduction-modified lithosphere can survive for hundreds of millions of years. Incorrect petrotectonic interpretations result when spatial–temporal–compositional trends of, and source contributions to, magmatism are not properly considered. Western Mexico has had protracted Cenozoic magmatism developed mostly in-board of active oceanic plate subduction beneath western North America. A broad range of igneous compositions from basalt to high-silica rhyolite were erupted with intermediate to silicic compositions in particular, showing calc-alkaline and other typical subduction-related geochemical signatures. A major Oligocene rhyolitic ignimbrite ‘flare-up’ (&gt;300 000 km<sup>3</sup>) switched to a bimodal volcanic phase in the Early Miocene (<em>c.</em> 100 000 km<sup>3</sup>), associated with distributed extension and opening of numerous graben. Extension became more focused <em>c.</em> 18 Ma resulting in localized volcanic activity along the future site of the Gulf of California. This localized volcanism (known as the Comondú ‘arc’) was dominantly effusive and andesite–dacite in composition. Past tectonic interpretations of Comondú-age volcanism may have been incorrect as these regional temporal–compositional changes are alternatively interpreted as a result of increased mixing of mantle-derived basaltic and crust-derived rhyolitic magmas in an active rift environment rather than fluid flux melting of the mantle wedge above the subducting Guadalupe Plate.
DOI: 10.6084/m9.figshare.3453416.v1
title: Pulling apart the Mid to Late Cenozoic magmatic record of the Gulf of California: is there a Comondú Arc?

description: The composition of the lithosphere can be fundamentally altered by long-lived subduction processes such that subduction-modified lithosphere can survive for hundreds of millions of years. Incorrect petrotectonic interpretations result when spatial–temporal–compositional trends of, and source contributions to, magmatism are not properly considered. Western Mexico has had protracted Cenozoic magmatism developed mostly in-board of active oceanic plate subduction beneath western North America. A broad range of igneous compositions from basalt to high-silica rhyolite were erupted with intermediate to silicic compositions in particular, showing calc-alkaline and other typical subduction-related geochemical signatures. A major Oligocene rhyolitic ignimbrite ‘flare-up’ (&gt;300 000 km<sup>3</sup>) switched to a bimodal volcanic phase in the Early Miocene (<em>c.</em> 100 000 km<sup>3</sup>), associated with distributed extension and opening of numerous graben. Extension became more focused <em>c.</em> 18 Ma resulting in localized volcanic activity along the future site of the Gulf of California. This localized volcanism (known as the Comondú ‘arc’) was dominantly effusive and andesite–dacite in composition. Past tectonic interpretations of Comondú-age volcanism may have been incorrect as these regional temporal–compositional changes are alternatively interpreted as a result of increased mixing of mantle-derived basaltic and crust-derived rhyolitic magmas in an active rift environment rather than fluid flux melting of the mantle wedge above the subducting Guadalupe Plate.
DOI: 10.6084/m9.figshare.3453413
title: High-magnesium andesites: the example of the Papuan Volcanic Arc

description: The late Cenozoic arc-type volcanic arc in southeastern Papua New Guinea developed in an environment of complex tectonic processes including obduction, subduction, rifting and sea floor spreading. The volcanic arc extends from the Papuan Peninsula south-eastward through the D'Entrecasteaux Islands into the Louisiade Archipelago. Lithologies are predominantly basaltic andesite and andesite, but include basalt, dacite and rhyolite. The rocks have typical arc-type geochemical features but include a group ranging from basalt to dacite which, although comparable in most other aspects of their compositions, are higher in MgO, Cr and Ni. These high-Mg rocks are less porphyritic and have simple olivine- or clinopyroxene- dominated phenocryst assemblages compared with the associated low-Mg rocks. The low-Mg rocks are plagioclase-phyric and contain augite and hypersthene with or without olivine, hornblende and biotite phenocrysts. Boninites are spatially associated with, but genetically unrelated to the arc-type rocks in Papua. The high-Mg rocks represent magmas derived by partial melting of subduction-modified mantle which rose rapidly from their source. In contrast, the low-Mg lavas represent magmas which were modified by shallow processes. The unusual abundance of high-Mg lavas in southeastern Papua is related to extensional tectonics which allowed deep sourced magmas to rise without significant modification.
DOI: 10.6084/m9.figshare.3453413.v1
title: High-magnesium andesites: the example of the Papuan Volcanic Arc

description: The late Cenozoic arc-type volcanic arc in southeastern Papua New Guinea developed in an environment of complex tectonic processes including obduction, subduction, rifting and sea floor spreading. The volcanic arc extends from the Papuan Peninsula south-eastward through the D'Entrecasteaux Islands into the Louisiade Archipelago. Lithologies are predominantly basaltic andesite and andesite, but include basalt, dacite and rhyolite. The rocks have typical arc-type geochemical features but include a group ranging from basalt to dacite which, although comparable in most other aspects of their compositions, are higher in MgO, Cr and Ni. These high-Mg rocks are less porphyritic and have simple olivine- or clinopyroxene- dominated phenocryst assemblages compared with the associated low-Mg rocks. The low-Mg rocks are plagioclase-phyric and contain augite and hypersthene with or without olivine, hornblende and biotite phenocrysts. Boninites are spatially associated with, but genetically unrelated to the arc-type rocks in Papua. The high-Mg rocks represent magmas derived by partial melting of subduction-modified mantle which rose rapidly from their source. In contrast, the low-Mg lavas represent magmas which were modified by shallow processes. The unusual abundance of high-Mg lavas in southeastern Papua is related to extensional tectonics which allowed deep sourced magmas to rise without significant modification.