cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3453602.v1
title: Use and calibration of portable X-Ray fluorescence analysers: application to lithogeochemical exploration for komatiite-hosted nickel sulphide deposits

description: Portable X-Ray Fluorescence (pXRF) analysers allow on-site geochemical analysis of rock powders and drill core. The main advantages of pXRF analysis over conventional laboratory analysis are the speed of data collection and the low cost of the analyses, permitting the collection of extensive, spatially representative datasets. However, these factors only become useful if the quality of the data meets the requirements needed for the purposes of the study. Here, we evaluate the possible use of portable XRF to determine element concentrations and ratios used in exploration for komatiite-hosted nickel sulphides. A portable XRF analyser was used to measure a series of chalcophile and lithophile element concentrations (Si, S, K, Ca, Ti, Cr, Fe, Ni, Cu, Zn, As, Sr, and Zr) of 75 samples from three komatiite units associated with nickel sulphide ores in the Yilgarn Craton, Western Australia. Crucial steps in the study were the development of a strict calibration process as well as numerous data quality checks. The 670 analyses collected in this study were compared with conventional laboratory XRF data on discriminant diagrams commonly utilized in exploration for komatiite-hosted nickel sulphides (Cr vs Ni and Ni/Ti vs Ni/Cr). After comparing the results obtained with pXRF during this study with the laboratory values, we can conclude that portable XRF analyses can be used for rapid assessment of the nickel sulphide prospectivity of komatiites provided that strict control protocols are followed.
DOI: 10.6084/m9.figshare.3453599
title: Ordovician to Silurian magmatism on the Utsira High, North Sea: implications for correlations between the onshore and offshore Caledonides

description: The age and tectonic significance of two basement granitoids cored on the Utsira High, Viking Graben, North Sea, are constrained by zircon LA-ICPMS data. Syenite in well 25/10-2R is dated to 482±2 Ma, with εHf<sub>(482)</sub> values from −4.4 to −5.8, and granite in well 16/1-12 yields an age of 436±3 Ma with εHf<sub>(436)</sub> values from +3.7 to −0.5. The evolved Hf-signature of the syenite demonstrates 482 Ma reworking of Palaeoproterozoic–Archaean crust, interpreted to reflect Taconian–Grampian orogenesis. New and recently published data from the offshore Caledonides allow a first-order correlation of the Utsira High basement with the surrounding on- and offshore Caledonides. The Utsira High occupies a similar position with respect to Dalradian rocks as the Scottish Midland Valley terrane. Geophysical data indicate a volcanic arc beneath the East Shetland Basin, forming a northwards continuation of the Utsira High basement. We propose that the offshore volcanic arc segments represent the northeastern continuation of the Scottish Grampian orogen across the Mesozoic North Sea rift. A north-striking terrane boundary fault is proposed to separate the volcanic arc from the East Shetland Platform and merge northwards with the offshore extension of the Great Glen Fault–Møre Trøndelag Fault Complex.
DOI: 10.6084/m9.figshare.3453599.v1
title: Ordovician to Silurian magmatism on the Utsira High, North Sea: implications for correlations between the onshore and offshore Caledonides

description: The age and tectonic significance of two basement granitoids cored on the Utsira High, Viking Graben, North Sea, are constrained by zircon LA-ICPMS data. Syenite in well 25/10-2R is dated to 482±2 Ma, with εHf<sub>(482)</sub> values from −4.4 to −5.8, and granite in well 16/1-12 yields an age of 436±3 Ma with εHf<sub>(436)</sub> values from +3.7 to −0.5. The evolved Hf-signature of the syenite demonstrates 482 Ma reworking of Palaeoproterozoic–Archaean crust, interpreted to reflect Taconian–Grampian orogenesis. New and recently published data from the offshore Caledonides allow a first-order correlation of the Utsira High basement with the surrounding on- and offshore Caledonides. The Utsira High occupies a similar position with respect to Dalradian rocks as the Scottish Midland Valley terrane. Geophysical data indicate a volcanic arc beneath the East Shetland Basin, forming a northwards continuation of the Utsira High basement. We propose that the offshore volcanic arc segments represent the northeastern continuation of the Scottish Grampian orogen across the Mesozoic North Sea rift. A north-striking terrane boundary fault is proposed to separate the volcanic arc from the East Shetland Platform and merge northwards with the offshore extension of the Great Glen Fault–Møre Trøndelag Fault Complex.
DOI: 10.6084/m9.figshare.3453596
title: Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya

description: Geochemical and geochronological analyses provide quantitative evidence about the origin, development and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India–Asia convergence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and U–Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at <em>c</em>. 800–1000 Ma, 1500–1700 Ma and 2300–2500 Ma and an ϵ<sub>Nd(0)</sub> signature of −18.3 to −12.1, and is intruded by <em>c</em>. 800 Ma and <em>c</em>. 500–600 Ma granites. In contrast, the footwall has a prominent detrital zircon peak at <em>c</em>. 1800–1900 Ma, with older populations spanning 1900–3600 Ma, and an ϵ<sub>Nd(0)</sub> signature of −27.7 to −23.4, intruded by <em>c</em>. 1830 Ma granites. The data reveal a <em>c</em>. 5 km thick zone of tectonic imbrication, where isotopically out-of-sequence packages are interleaved. The rocks became imbricated as the once proximal and distal rocks of the Indian margin were juxtaposed by Cenozoic movement along the Main Central Thrust. Geochronological and isotopic characterization allows for correlation along the Himalayan orogen and could be applied to other cryptic ductile shear zones.
DOI: 10.6084/m9.figshare.3453596.v1
title: Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya

description: Geochemical and geochronological analyses provide quantitative evidence about the origin, development and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India–Asia convergence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and U–Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at <em>c</em>. 800–1000 Ma, 1500–1700 Ma and 2300–2500 Ma and an ϵ<sub>Nd(0)</sub> signature of −18.3 to −12.1, and is intruded by <em>c</em>. 800 Ma and <em>c</em>. 500–600 Ma granites. In contrast, the footwall has a prominent detrital zircon peak at <em>c</em>. 1800–1900 Ma, with older populations spanning 1900–3600 Ma, and an ϵ<sub>Nd(0)</sub> signature of −27.7 to −23.4, intruded by <em>c</em>. 1830 Ma granites. The data reveal a <em>c</em>. 5 km thick zone of tectonic imbrication, where isotopically out-of-sequence packages are interleaved. The rocks became imbricated as the once proximal and distal rocks of the Indian margin were juxtaposed by Cenozoic movement along the Main Central Thrust. Geochronological and isotopic characterization allows for correlation along the Himalayan orogen and could be applied to other cryptic ductile shear zones.
DOI: 10.6084/m9.figshare.3453593
title: Late Variscan metamorphic and magmatic evolution in the eastern Pyrenees revealed by U–Pb age zircon dating

description: Variscan migmatites cropping out in the eastern Pyrenees were dated together with Late Variscan plutonic rocks. Upper Proterozoic–Lower Cambrian series were migmatized during a thermal episode that occurred in the interval 320–315 Ma coeval with the main Variscan deformation event (D<sub>1</sub>). The calc-alkaline Sant Llorenç–La Jonquera pluton and the gabbro–diorite Ceret stock were emplaced during a later thermal episode synchronous with the D<sub>2</sub> deformation event. A tonalite located at the base of La Jonquera suite intruded into the upper crustal levels between 314 and 311 Ma. The gabbro–diorite stock was emplaced in the middle levels of the series in two magmatic pulses at 312 and 307 Ma. The thermal evolution recorded in the eastern Pyrenees can be correlated with that of neighbouring areas of NE Iberia (Pyrenees–Catalan Coastal Ranges) and SE France (Montagne Noire). The correlation suggests a NW–SE-trending zonation where the northeasternmost areas (Montagne Noire and eastern Pyrenees) would occupy relatively more internal zones of the orogen than the southwesternmost ones.
DOI: 10.6084/m9.figshare.3453593.v1
title: Late Variscan metamorphic and magmatic evolution in the eastern Pyrenees revealed by U–Pb age zircon dating

description: Variscan migmatites cropping out in the eastern Pyrenees were dated together with Late Variscan plutonic rocks. Upper Proterozoic–Lower Cambrian series were migmatized during a thermal episode that occurred in the interval 320–315 Ma coeval with the main Variscan deformation event (D<sub>1</sub>). The calc-alkaline Sant Llorenç–La Jonquera pluton and the gabbro–diorite Ceret stock were emplaced during a later thermal episode synchronous with the D<sub>2</sub> deformation event. A tonalite located at the base of La Jonquera suite intruded into the upper crustal levels between 314 and 311 Ma. The gabbro–diorite stock was emplaced in the middle levels of the series in two magmatic pulses at 312 and 307 Ma. The thermal evolution recorded in the eastern Pyrenees can be correlated with that of neighbouring areas of NE Iberia (Pyrenees–Catalan Coastal Ranges) and SE France (Montagne Noire). The correlation suggests a NW–SE-trending zonation where the northeasternmost areas (Montagne Noire and eastern Pyrenees) would occupy relatively more internal zones of the orogen than the southwesternmost ones.
DOI: 10.6084/m9.figshare.3453590
title: Detrital zircon U–Pb and <sup>40</sup>Ar/<sup>39</sup>Ar hornblende ages from the Aileu Complex, Timor-Leste: provenance and metamorphic cooling history

description: Geochronological data from the Aileu Complex provide new constraints on the development of the Banda Arc–continent collision. Detrital zircons of the Aileu Complex have major U–Pb age modes at 270–440 Ma, 860–1240 Ma and 1460–1870 Ma, most compatible with a sediment source located in SE Asia as part of the now fragmented Sula Spur. <sup>40</sup>Ar/<sup>39</sup>Ar cooling ages of hornblende demonstrate an extended cooling history across the complex, with the eastern parts cooling through hornblende closure temperature by 10 Ma and central parts by 6 Ma, consistent with a variable exhumation history. The onset of cooling by 10 Ma implies that metamorphism was probably coeval with initiation of the Banda Arc. We propose that the Aileu Complex cooling ages record deformation related to fragmentation of the Sula Spur and early development of the Banda Arc, rather than collision between the Australian continent and the Banda Arc.
DOI: 10.6084/m9.figshare.3453590.v1
title: Detrital zircon U–Pb and <sup>40</sup>Ar/<sup>39</sup>Ar hornblende ages from the Aileu Complex, Timor-Leste: provenance and metamorphic cooling history

description: Geochronological data from the Aileu Complex provide new constraints on the development of the Banda Arc–continent collision. Detrital zircons of the Aileu Complex have major U–Pb age modes at 270–440 Ma, 860–1240 Ma and 1460–1870 Ma, most compatible with a sediment source located in SE Asia as part of the now fragmented Sula Spur. <sup>40</sup>Ar/<sup>39</sup>Ar cooling ages of hornblende demonstrate an extended cooling history across the complex, with the eastern parts cooling through hornblende closure temperature by 10 Ma and central parts by 6 Ma, consistent with a variable exhumation history. The onset of cooling by 10 Ma implies that metamorphism was probably coeval with initiation of the Banda Arc. We propose that the Aileu Complex cooling ages record deformation related to fragmentation of the Sula Spur and early development of the Banda Arc, rather than collision between the Australian continent and the Banda Arc.
DOI: 10.6084/m9.figshare.3453587
title: Chapter 14 Continuous and campaign-style gravimetric investigations on Montserrat 2006 to 2009

description: Gravimetric time series can provide vital clues about subsurface dynamics associated with active volcanism. Here, we report on continuous and campaign-style gravimetric observations on Montserrat between 2006 and 2009. More than 240 days of continuous gravimetric records enabled us to derive a first local joint solid Earth tides and ocean loading model for Montserrat, and we report the tidal harmonics for 14 major wave groups. Compared to global predictions, the new model (MTY11) achieves an up to one order of magnitude better precision over diurnal and semi-diurnal frequencies. We anticipate that the model will help reduce the effects of tidal perturbations on other geodetic time series recorded on Montserrat. Abrupt variations in gravity accompanied Vulcanian explosions and probably reflect the response of a shallow aquifer to stress changes during pressurization and depressurization of the subvolcanic plumbing system. Campaign data enabled the quantification of mass variations during a cycle of activity including dome formation and repose. Both forward and inverse modelling of the spatio-temporal time series indicates that the source of the recorded gravity variations is situated beneath central Montserrat. Our favourite interpretation of the campaign data is that the gravity variations reflect volcano-tectonic interaction beneath the Centre Hills of Montserrat that are triggered by changes in the active magmatic system of Soufrière Hills Volcano (SHV). We also discuss our findings on subsurface mass variations in relation to annual precipitation records and active dome formation. Both continuous and discrete gravimetric observations indicate coupling between the dominant magmatic sources responsible for the ongoing eruption at SHV and shallow-seated local sources such as aquifers and fluid-saturated fault-damage zones. Our investigations demonstrate the value of including gravimetric observations over a wide frequency range for volcanic system characterization in a volcanic island arc setting.
DOI: 10.6084/m9.figshare.3453587.v1
title: Chapter 14 Continuous and campaign-style gravimetric investigations on Montserrat 2006 to 2009

description: Gravimetric time series can provide vital clues about subsurface dynamics associated with active volcanism. Here, we report on continuous and campaign-style gravimetric observations on Montserrat between 2006 and 2009. More than 240 days of continuous gravimetric records enabled us to derive a first local joint solid Earth tides and ocean loading model for Montserrat, and we report the tidal harmonics for 14 major wave groups. Compared to global predictions, the new model (MTY11) achieves an up to one order of magnitude better precision over diurnal and semi-diurnal frequencies. We anticipate that the model will help reduce the effects of tidal perturbations on other geodetic time series recorded on Montserrat. Abrupt variations in gravity accompanied Vulcanian explosions and probably reflect the response of a shallow aquifer to stress changes during pressurization and depressurization of the subvolcanic plumbing system. Campaign data enabled the quantification of mass variations during a cycle of activity including dome formation and repose. Both forward and inverse modelling of the spatio-temporal time series indicates that the source of the recorded gravity variations is situated beneath central Montserrat. Our favourite interpretation of the campaign data is that the gravity variations reflect volcano-tectonic interaction beneath the Centre Hills of Montserrat that are triggered by changes in the active magmatic system of Soufrière Hills Volcano (SHV). We also discuss our findings on subsurface mass variations in relation to annual precipitation records and active dome formation. Both continuous and discrete gravimetric observations indicate coupling between the dominant magmatic sources responsible for the ongoing eruption at SHV and shallow-seated local sources such as aquifers and fluid-saturated fault-damage zones. Our investigations demonstrate the value of including gravimetric observations over a wide frequency range for volcanic system characterization in a volcanic island arc setting.
DOI: 10.6084/m9.figshare.3453581
title: The Baltoscandian margin detrital zircon signatures of the central Scandes

description: In central parts of the Scandinavian Caledonides, detrital zircon signatures provide evidence of the change in character of the Baltoscandian crystalline basement, from the characteristic Late Palaeoproterozoic granites of the Transscandinavian Igneous Belt (TIB, <em>c.</em> 1650–1850 Ma) in the foreland Autochthon to the typical, mainly Mesoproterozoic-age profile (<em>c.</em> 950–1700 Ma) of the Sveconorwegian Orogen of southwestern Scandinavia in the hinterland. Late Ediacaran to Early Cambrian shallow-marine Vemdal quartzites of the Jämtlandian Nappes (Lower Allochthon) provide strong bimodal signatures with TIB (1700–1800 Ma) and Sveconorwegian, <em>sensu stricto</em> (900–1150 Ma) ages dominant. Mid-Ordovician turbidites (Norråker Formation) of the Lower Allochthon in Sweden, sourced from the west, have unimodal signatures dominated by Sveconorwegian ages with peaks at 1000–1100 Ma, but with subordinate components of older Mesoproterozoic zircons (1200–1650 Ma). Latest Ordovician shallow-marine quartzites also yield bimodal signatures, but are more dispersed than in the Vemdal quartzites. In the greenschist facies lower parts of the Middle Allochthon, the Fuda (Offerdal Nappe) and Särv Nappe signatures are either unimodal or bimodal (950–1100 and/or 1700–1850 Ma), with variable dominance of the younger or older group, and subordinate other Mesoproterozoic components. In the overlying, amphibolite to eclogite facies lower part of the Seve Nappe Complex, where the metasediments are dominated by feldspathic quartzites, calcsilicate-rich psammites and marbles, most units have bimodal signatures similar to the Särv Nappes, but more dispersed; one has a unimodal signature very similar to the Ordovician turbidites of the Jämtlandian Nappes. In the overlying Upper Allochthon, Lower Köli (Baltica-proximal, Virisen Terrane), Late Ordovician quartzites provide unimodal signatures dominated by Sveconorwegian ages (<em>sensu stricto</em>). Further north in the Scandes, previously published zircon signatures in quartzites of the Lower Allochthon are similar to the Vemdal quartzites in Jämtland. Data from the Kalak Nappes at 70°N are in no way exotic to the Sveconorwegian Baltoscandian margin. They do show a Timanian influence (ages of <em>c.</em> 560–610 Ma), as would be expected from the palinspastic reconstructions of the nappes. Thus the detrital zircon signatures reported here and published elsewhere provide supporting evidence for a continuation northwards of the Sveconorwegian Orogen in the Neoproterozoic, from type areas in the south, along the Baltoscandian margin of Baltica into the high Arctic.
DOI: 10.6084/m9.figshare.3453581.v1
title: The Baltoscandian margin detrital zircon signatures of the central Scandes

description: In central parts of the Scandinavian Caledonides, detrital zircon signatures provide evidence of the change in character of the Baltoscandian crystalline basement, from the characteristic Late Palaeoproterozoic granites of the Transscandinavian Igneous Belt (TIB, <em>c.</em> 1650–1850 Ma) in the foreland Autochthon to the typical, mainly Mesoproterozoic-age profile (<em>c.</em> 950–1700 Ma) of the Sveconorwegian Orogen of southwestern Scandinavia in the hinterland. Late Ediacaran to Early Cambrian shallow-marine Vemdal quartzites of the Jämtlandian Nappes (Lower Allochthon) provide strong bimodal signatures with TIB (1700–1800 Ma) and Sveconorwegian, <em>sensu stricto</em> (900–1150 Ma) ages dominant. Mid-Ordovician turbidites (Norråker Formation) of the Lower Allochthon in Sweden, sourced from the west, have unimodal signatures dominated by Sveconorwegian ages with peaks at 1000–1100 Ma, but with subordinate components of older Mesoproterozoic zircons (1200–1650 Ma). Latest Ordovician shallow-marine quartzites also yield bimodal signatures, but are more dispersed than in the Vemdal quartzites. In the greenschist facies lower parts of the Middle Allochthon, the Fuda (Offerdal Nappe) and Särv Nappe signatures are either unimodal or bimodal (950–1100 and/or 1700–1850 Ma), with variable dominance of the younger or older group, and subordinate other Mesoproterozoic components. In the overlying, amphibolite to eclogite facies lower part of the Seve Nappe Complex, where the metasediments are dominated by feldspathic quartzites, calcsilicate-rich psammites and marbles, most units have bimodal signatures similar to the Särv Nappes, but more dispersed; one has a unimodal signature very similar to the Ordovician turbidites of the Jämtlandian Nappes. In the overlying Upper Allochthon, Lower Köli (Baltica-proximal, Virisen Terrane), Late Ordovician quartzites provide unimodal signatures dominated by Sveconorwegian ages (<em>sensu stricto</em>). Further north in the Scandes, previously published zircon signatures in quartzites of the Lower Allochthon are similar to the Vemdal quartzites in Jämtland. Data from the Kalak Nappes at 70°N are in no way exotic to the Sveconorwegian Baltoscandian margin. They do show a Timanian influence (ages of <em>c.</em> 560–610 Ma), as would be expected from the palinspastic reconstructions of the nappes. Thus the detrital zircon signatures reported here and published elsewhere provide supporting evidence for a continuation northwards of the Sveconorwegian Orogen in the Neoproterozoic, from type areas in the south, along the Baltoscandian margin of Baltica into the high Arctic.