cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.3454691.v1
title: Late Cretaceous to Miocene seamount accretion and mélange formation in the Osa and Burica Peninsulas (Southern Costa Rica): episodic growth of a convergent margin

description: Multidisciplinary study of the Osa and Burica peninsulas, Costa Rica, recognizes the Osa Igneous Complex and the Osa Mélange – records of a complex Late Cretaceous–Miocene tectonic–sedimentary history. The Igneous Complex, an accretionary prism (<em>sensu stricto</em>) comprises mainly basaltic lava flows, with minor sills, gabbroic intrusives, pelagic limestones and radiolarites. Sediments or igneous rocks derived from the upper plate are absent. Four units delimited on the base of stratigraphy and geochemistry lie in contact along reactivated palaeo-décollement zones. They comprise fragments of a Coniacian–Santonian oceanic plateau (Inner Osa Igneous Complex) and Coniacian–Santonian to Middle Eocene seamounts (Outer Osa Igneous Complex). The units are unrelated to other igneous complexes of Costa Rica and Panama and are exotic with respect to the partly overthickened Caribbean Plate; they formed by multiple accretions between the Late Cretaceous and Middle Eocene, prior to the genesis of the mélange. Events of high-rate accretion alternated with periods of low-rate accretion and tectonic erosion. The NW Osa Mélange in contact with the Osa Igneous Complex has a block-in-matrix texture at various scales, produced by sedimentary processes and later tectonically enhanced. Lithologies are mainly debris flows and hemipelagic deposits. Clastic components (grains to large boulders) indicate Late Eocene mass wasting of the Igneous Complex, forearc deposits and a volcanic arc. Gravitational accumulation of a thick pile of trench sediments culminated with shallow-level accretion. Mass-wasting along the margin was probably triggered by seamount subduction and/or plate reorganization at larger scale. The study provides new geological constraints for seamount subduction and associated accretionary processes, as well as on the erosive/accretionary nature of convergent margins devoid of accreted sediments.
DOI: 10.6084/m9.figshare.3454679
title: Evidence of multi-phase Cretaceous to Quaternary alkaline magmatism on Tore–Madeira Rise and neighbouring seamounts from <sup>40</sup>Ar/<sup>39</sup>Ar ages

description: The Tore–Madeira Rise is a seamount chain located 300 km off the Portugal and Morocco coasts attributed to hotspot activity. U–Pb ages of lavas from the northern and central Tore–Madeira Rise range between 103 and 80.5 Ma whereas <sup>40</sup>Ar/<sup>39</sup>Ar ages from the central and southern Tore–Madeira Rise yield ages ranging from 94.5 to 0.5 Ma. We performed new <sup>40</sup>Ar/<sup>39</sup>Ar measurements to better understand the geodynamic history of the Tore–Madeira Rise. Plagioclase ages from the Bikini Bottom and Torillon seamounts suggest ages of &gt;90 Ma and ≥60 Ma, respectively. Amphiboles from the Seine seamount yield an age of 24.0 ± 0.8 Ma. Biotites from lavas of the Ashton seamount give ages of 97.4 ± 1.1 Ma and 97.8 ± 1.1 Ma. The geochronological database available on the Tore–Madeira Rise has been filtered on statistical criteria to eliminate unreliable ages. The resulting database reveals three pulses of alkaline magmatism on the Tore–Madeira Rise at 103–80.5 Ma, at <em>c</em>. 68 Ma and between 30 Ma and the present. The magmatism was continuous from 103 Ma until <em>c</em>. 68 Ma and from <em>c</em>. 30 Ma until the present on the Tore–Madeira Rise, the surrounding seamounts and the Portugal coast. We suggest that the space–time distribution of this magmatism results from the interaction between a wide thermal anomaly emitting magmatic pulses and the complex motion of the Iberian plate.
DOI: 10.6084/m9.figshare.3454676
title: The Precambrian Khondalite Belt in the Daqingshan area, North China Craton: evidence for multiple metamorphic events in the Palaeoproterozoic era

description: High-grade pelitic metasedimentary rocks (khondalites) are widely distributed in the northwestern part of the North China Craton and were named the ‘Khondalite Belt’. Prior to the application of zircon geochronology, a stratigraphic division of the supracrustal rocks into several groups was established using interpretative field geology. We report here SHRIMP U–Pb zircon ages and Hf-isotope data on metamorphosed sedimentary and magmatic rocks at Daqingshan, a typical area of the Khondalite Belt. The main conclusions are as follows: (1) The early Precambrian supracrustal rocks belong to three sequences: a 2.56–2.51 Ga supracrustal unit (the previous Sanggan ‘group’), a 2.51–2.45 Ga supracrustal unit (a portion of the previous upper Wulashan ‘group’) and a 2.0–1.95 Ga supracrustal unit (including the previous lower Wulashan ‘group’, a portion of original upper Wulashan ‘group’ and the original Meidaizhao ‘group’) the units thus do not represent a true stratigraphy; (2) Strong tectono-thermal events occurred during the late Neoarchaean to late Palaeoproterozoic, with four episodes recognized: 2.6–2.5, 2.45–2.37, 2.3–2.0 and 1.95–1.85 Ga, with the latest event being consistent with the assembly of the Palaeoproterozoic supercontinent Columbia; (3) During the late Neoarchaean to late Palaeoproterozoic (2.55–2.5, 2.37 and 2.06 Ga) juvenile, mantle-derived material was added to the crust.
DOI: 10.6084/m9.figshare.3454676.v1
title: The Precambrian Khondalite Belt in the Daqingshan area, North China Craton: evidence for multiple metamorphic events in the Palaeoproterozoic era

description: High-grade pelitic metasedimentary rocks (khondalites) are widely distributed in the northwestern part of the North China Craton and were named the ‘Khondalite Belt’. Prior to the application of zircon geochronology, a stratigraphic division of the supracrustal rocks into several groups was established using interpretative field geology. We report here SHRIMP U–Pb zircon ages and Hf-isotope data on metamorphosed sedimentary and magmatic rocks at Daqingshan, a typical area of the Khondalite Belt. The main conclusions are as follows: (1) The early Precambrian supracrustal rocks belong to three sequences: a 2.56–2.51 Ga supracrustal unit (the previous Sanggan ‘group’), a 2.51–2.45 Ga supracrustal unit (a portion of the previous upper Wulashan ‘group’) and a 2.0–1.95 Ga supracrustal unit (including the previous lower Wulashan ‘group’, a portion of original upper Wulashan ‘group’ and the original Meidaizhao ‘group’) the units thus do not represent a true stratigraphy; (2) Strong tectono-thermal events occurred during the late Neoarchaean to late Palaeoproterozoic, with four episodes recognized: 2.6–2.5, 2.45–2.37, 2.3–2.0 and 1.95–1.85 Ga, with the latest event being consistent with the assembly of the Palaeoproterozoic supercontinent Columbia; (3) During the late Neoarchaean to late Palaeoproterozoic (2.55–2.5, 2.37 and 2.06 Ga) juvenile, mantle-derived material was added to the crust.
DOI: 10.6084/m9.figshare.3454670
title: Recent progress in Scandian ultrahigh-pressure metamorphism in the northernmost domain of the Western Gneiss Complex, SW Norway: continental subduction down to 180–200 km depth

description: Earlier workers established 20 kbar and 750–800 °C as being the maximum Scandian metamorphic grade for the Caledonized basement units in the northernmost ultrahigh-pressure metamorphic (UHPM) domain of the Western Gneiss Region, SW Norway. These early pressure estimates were entirely based on jadeite isopleths applied to bimineralic eclogites; low Al values in orthopyroxene from opx-eclogites were interpreted to be due to ’disequilibrium effects'. After the initial discovery of microdiamond and majoritic garnet in the area, the low Al<sub>2</sub>O<sub>3</sub> isopleths in opx (cores), ranging from 0.15 to 1.50 wt% in newly discovered and already known occurrences of ’internal' and ’external' opx eclogites–websterites, were reinvestigated and taken as the first indicator that metamorphic grade, on a regional scale, occurred at much higher pressures than previously thought. Regional-scale diamond-grade UHPM conditions were subsequently demonstrated by <em>in situ</em> microdiamond discoveries in two widely separated orthopyroxene eclogite–websterite localities included in Mg–Cr (mantle-derived) and Fe–Ti type (crust-derived) peridotite–websterite bodies, leading to a simple strategy for <em>in situ</em> microdiamond recognition, described here for the first time. All <em>in situ</em> microdiamonds are associated with multiphase solid-inclusion assemblages interpreted to be crystallized from Scandian supercritical, dense, COH-rich subduction zone fluids. In addition, the recent discovery at Fjørtoft of a second, Scandian, majoritic garnet generation (in garnet websterites enclosed in garnet peridotite), having enriched light REE (LREE) patterns (in clinopyroxene and garnet), contrasts strongly to the Archaean–mid-Proterozoic LREE-depleted majoritic garnet patterns (and exsolved pyroxenes) discovered in garnet peridotites from Otrøy. The latter is strong evidence that Scandian continental subduction (and eduction) occurred down to 180–200 km depths, making the northernmost UHPM domain by far the deepest subducted (and educted) part of the Western Gneiss Complex. Such a conclusion is also consistent with (some) geothermobarometric results from internal and external orthopyroxene eclogites and garnet websterites showing results indicative of pressure–temperature estimates deep in the diamond-eclogite facies (850–950 °C and 5.5–6.5 GPa ).
DOI: 10.6084/m9.figshare.3454670.v1
title: Recent progress in Scandian ultrahigh-pressure metamorphism in the northernmost domain of the Western Gneiss Complex, SW Norway: continental subduction down to 180–200 km depth

description: Earlier workers established 20 kbar and 750–800 °C as being the maximum Scandian metamorphic grade for the Caledonized basement units in the northernmost ultrahigh-pressure metamorphic (UHPM) domain of the Western Gneiss Region, SW Norway. These early pressure estimates were entirely based on jadeite isopleths applied to bimineralic eclogites; low Al values in orthopyroxene from opx-eclogites were interpreted to be due to ’disequilibrium effects'. After the initial discovery of microdiamond and majoritic garnet in the area, the low Al<sub>2</sub>O<sub>3</sub> isopleths in opx (cores), ranging from 0.15 to 1.50 wt% in newly discovered and already known occurrences of ’internal' and ’external' opx eclogites–websterites, were reinvestigated and taken as the first indicator that metamorphic grade, on a regional scale, occurred at much higher pressures than previously thought. Regional-scale diamond-grade UHPM conditions were subsequently demonstrated by <em>in situ</em> microdiamond discoveries in two widely separated orthopyroxene eclogite–websterite localities included in Mg–Cr (mantle-derived) and Fe–Ti type (crust-derived) peridotite–websterite bodies, leading to a simple strategy for <em>in situ</em> microdiamond recognition, described here for the first time. All <em>in situ</em> microdiamonds are associated with multiphase solid-inclusion assemblages interpreted to be crystallized from Scandian supercritical, dense, COH-rich subduction zone fluids. In addition, the recent discovery at Fjørtoft of a second, Scandian, majoritic garnet generation (in garnet websterites enclosed in garnet peridotite), having enriched light REE (LREE) patterns (in clinopyroxene and garnet), contrasts strongly to the Archaean–mid-Proterozoic LREE-depleted majoritic garnet patterns (and exsolved pyroxenes) discovered in garnet peridotites from Otrøy. The latter is strong evidence that Scandian continental subduction (and eduction) occurred down to 180–200 km depths, making the northernmost UHPM domain by far the deepest subducted (and educted) part of the Western Gneiss Complex. Such a conclusion is also consistent with (some) geothermobarometric results from internal and external orthopyroxene eclogites and garnet websterites showing results indicative of pressure–temperature estimates deep in the diamond-eclogite facies (850–950 °C and 5.5–6.5 GPa ).
DOI: 10.6084/m9.figshare.3454667
title: Fluid regime in continental subduction zones: petrological insights from ultrahigh-pressure metamorphic rocks

description: Intensive studies of ultrahigh-pressure (UHP) metamorphic rocks in continental collision zones have provided petrological insights into the fluid regime during subduction and exhumation. Recent studies in the Dabie–Sulu orogen of China have made important contributions to understanding fluid action in such systems, hence these rocks are the main focus of this review. Sources of metamorphic fluid can be deduced from study of hydrous minerals, structural hydroxyl and molecular water in nominally anhydrous minerals. Fluid and solid inclusions of UHP metamorphic minerals are also a record of fluid action in deep subduction zones. The presence or absence of metamorphic fluid during subduction and exhumation dictates zircon growth and recrystallization, making available materials for U–Pb dating. Isotopic dating demonstrates that after peak UHP metamorphism, retrograde fluid with deuteric origin became active. The decomposition of hydrous minerals and the exsolution of molecular water and structural hydroxyl during exhumation can provide sufficient amounts of aqueous fluid for quartz veining and amphibolite-facies retrogression within UHP slabs. Aqueous fluid released by the exsolution of molecular water and structural hydroxyl from UHP nominally anhydrous minerals is characterized by low salinity and light hydrogen and oxygen isotope compositions. Therefore, one part of the UHP slab is a source of aqueous fluid, whereas another part is a sink. In both cases, the fluid action during subduction and exhumation is episodic rather than continuous.
DOI: 10.6084/m9.figshare.3454667.v1
title: Fluid regime in continental subduction zones: petrological insights from ultrahigh-pressure metamorphic rocks

description: Intensive studies of ultrahigh-pressure (UHP) metamorphic rocks in continental collision zones have provided petrological insights into the fluid regime during subduction and exhumation. Recent studies in the Dabie–Sulu orogen of China have made important contributions to understanding fluid action in such systems, hence these rocks are the main focus of this review. Sources of metamorphic fluid can be deduced from study of hydrous minerals, structural hydroxyl and molecular water in nominally anhydrous minerals. Fluid and solid inclusions of UHP metamorphic minerals are also a record of fluid action in deep subduction zones. The presence or absence of metamorphic fluid during subduction and exhumation dictates zircon growth and recrystallization, making available materials for U–Pb dating. Isotopic dating demonstrates that after peak UHP metamorphism, retrograde fluid with deuteric origin became active. The decomposition of hydrous minerals and the exsolution of molecular water and structural hydroxyl during exhumation can provide sufficient amounts of aqueous fluid for quartz veining and amphibolite-facies retrogression within UHP slabs. Aqueous fluid released by the exsolution of molecular water and structural hydroxyl from UHP nominally anhydrous minerals is characterized by low salinity and light hydrogen and oxygen isotope compositions. Therefore, one part of the UHP slab is a source of aqueous fluid, whereas another part is a sink. In both cases, the fluid action during subduction and exhumation is episodic rather than continuous.
DOI: 10.6084/m9.figshare.3454664
title: On the occurrence and boron isotopic composition of tourmaline in (ultra)high-pressure metamorphic rocks

description: The extensive <em>P–T</em> stability and the high chemical variability of tourmaline (Tur) together with its common occurrence in metasediments proves its high potential for petrological and (isotope) geochemical studies on fluid–rock interaction in subduction- and collision-related rocks. This paper reviews the occurrence, major element chemistry and boron isotopic composition of Tur in high- and ultrahigh-pressure metamorphic (UHPM) rocks. In addition, it presents a new discovery of coesite-bearing Tur (schorl) from the Erzgebirge (Germany), as well as Tur (dravite) related to the retrograde history of coesite- and diamond-bearing rocks from the Erzgebirge and the Kokchetav Massif (Kazakhstan). The scarce data on worldwide occurrences of (U)HPM Tur reveal a high occupation of the crystallographic X-site (dominated by Na) and the possible presence of excess B, with little further distinctiveness in its major element composition when compared with Tur from medium-grade rocks. High K<sub>2</sub>O contents in Tur are probably not related to UHP growth or equilibration. The B isotopic composition of (U)HPM Tur ranges in δ<sup>11</sup>B from −16 to +1‰, with many samples in or below the range of continental crust. In contrast, Tur formed during retrograde fluid influx typically shows high δ<sup>11</sup>B values (up to +28‰), suggesting heavy-B fluids infiltrating the exhuming (U)HPM units. Coesite inclusions in Tur, characterized by Raman spectroscopy, are regarded as the best indicator for its UHP stability.
DOI: 10.6084/m9.figshare.3454664.v1
title: On the occurrence and boron isotopic composition of tourmaline in (ultra)high-pressure metamorphic rocks

description: The extensive <em>P–T</em> stability and the high chemical variability of tourmaline (Tur) together with its common occurrence in metasediments proves its high potential for petrological and (isotope) geochemical studies on fluid–rock interaction in subduction- and collision-related rocks. This paper reviews the occurrence, major element chemistry and boron isotopic composition of Tur in high- and ultrahigh-pressure metamorphic (UHPM) rocks. In addition, it presents a new discovery of coesite-bearing Tur (schorl) from the Erzgebirge (Germany), as well as Tur (dravite) related to the retrograde history of coesite- and diamond-bearing rocks from the Erzgebirge and the Kokchetav Massif (Kazakhstan). The scarce data on worldwide occurrences of (U)HPM Tur reveal a high occupation of the crystallographic X-site (dominated by Na) and the possible presence of excess B, with little further distinctiveness in its major element composition when compared with Tur from medium-grade rocks. High K<sub>2</sub>O contents in Tur are probably not related to UHP growth or equilibration. The B isotopic composition of (U)HPM Tur ranges in δ<sup>11</sup>B from −16 to +1‰, with many samples in or below the range of continental crust. In contrast, Tur formed during retrograde fluid influx typically shows high δ<sup>11</sup>B values (up to +28‰), suggesting heavy-B fluids infiltrating the exhuming (U)HPM units. Coesite inclusions in Tur, characterized by Raman spectroscopy, are regarded as the best indicator for its UHP stability.
DOI: 10.6084/m9.figshare.3454658
title: The IGCP 509 database system: design and application of a tool to capture and illustrate litho- and chrono-stratigraphic information for Palaeoproterozoic tectonic domains, large igneous provinces and ore deposits; with examples from southern Africa

description: The IGCP 509 project is collating global information for the Palaeoproterozoic era through the activities of numerous international collaborators. A database system (StratDB) and web interface has been designed to facilitate this process with links to an existing geochronology database (DateView). As a result, all information captured will remain available in a digital format for future researchers. The philosophy and design of the database and some of the outputs available from it are described. One of the principal features of the system is that it facilitates the construction of time–space correlation charts using an innovative application of GIS technology to non-geographic information, which permits users to query a variety of attribute information associated with lithostratigraphic units, metamorphic and deformation episodes associated with user-selected tectonic domains, large igneous provinces and major ore deposits. In the process, much of the manual labour normally associated with the construction of such charts in standard graphical or drafting packages is avoided. Associations between units, deformation, metamorphism, large igneous provinces and ore deposits may become more apparent once linked information is available for querying and investigation. Geochronological information from the DateView database may also be linked to entities stored in StratDB. GIS maps may be linked to the attribute information in StratDB and DateView to construct a variety of time-slice maps or palaeogeographic reconstructions with the same symbology as is used in the time–space correlation charts. This database system will facilitate the dissemination of lithostratigraphic information for many countries to a broader community and will help non-specialists to easily view information for various Palaeoproterozoic tectonic domains. The system is illustrated using a preliminary compilation of information for the Palaeoproterozoic of southern Africa. The correlation charts and time-slice maps provide insights to the geological evolution of this region which emphasize some aspects and correlations which have not previously been extensively considered; for instance, possible correlation of units in the central and western zones of the Limpopo Belt (South Africa, Zimbabwe and Botswana) with the Magondi Belt of Zimbabwe and its extension into northern Botswana.
DOI: 10.6084/m9.figshare.3454658.v1
title: The IGCP 509 database system: design and application of a tool to capture and illustrate litho- and chrono-stratigraphic information for Palaeoproterozoic tectonic domains, large igneous provinces and ore deposits; with examples from southern Africa

description: The IGCP 509 project is collating global information for the Palaeoproterozoic era through the activities of numerous international collaborators. A database system (StratDB) and web interface has been designed to facilitate this process with links to an existing geochronology database (DateView). As a result, all information captured will remain available in a digital format for future researchers. The philosophy and design of the database and some of the outputs available from it are described. One of the principal features of the system is that it facilitates the construction of time–space correlation charts using an innovative application of GIS technology to non-geographic information, which permits users to query a variety of attribute information associated with lithostratigraphic units, metamorphic and deformation episodes associated with user-selected tectonic domains, large igneous provinces and major ore deposits. In the process, much of the manual labour normally associated with the construction of such charts in standard graphical or drafting packages is avoided. Associations between units, deformation, metamorphism, large igneous provinces and ore deposits may become more apparent once linked information is available for querying and investigation. Geochronological information from the DateView database may also be linked to entities stored in StratDB. GIS maps may be linked to the attribute information in StratDB and DateView to construct a variety of time-slice maps or palaeogeographic reconstructions with the same symbology as is used in the time–space correlation charts. This database system will facilitate the dissemination of lithostratigraphic information for many countries to a broader community and will help non-specialists to easily view information for various Palaeoproterozoic tectonic domains. The system is illustrated using a preliminary compilation of information for the Palaeoproterozoic of southern Africa. The correlation charts and time-slice maps provide insights to the geological evolution of this region which emphasize some aspects and correlations which have not previously been extensively considered; for instance, possible correlation of units in the central and western zones of the Limpopo Belt (South Africa, Zimbabwe and Botswana) with the Magondi Belt of Zimbabwe and its extension into northern Botswana.