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Hebrides
\"Peter May and photographer David Wilson present a photographic record of the countless locations around the Hebridean archipelago that so inspired May when he was bringing the islands of detective Fin McLeod's childhood to the page. From the tiny southern island of Barra to the largest and most northern island of Lewis, travel the storm-whipped North Atlantic scenery with May as he once again strolls the wild and breathtaking countryside that gave birth to his masterful trilogy of novels\"--Amazon.com.
Book
Clumped-isotope palaeothermometry and LA-ICP-MS U–Pb dating of lava-pile hydrothermal calcite veins
Calcite veins are a common product of hydrothermal fluid circulation. Clumped-isotope palaeothermometry is a promising technique for fingerprinting the temperature of hydrothermal fluids, but clumped-isotope systematics can be reset at temperatures of > ca. 100 °C. To model whether the reconstructed temperatures represent calcite precipitation or closed-system resetting, the precipitation age must be known. LA-ICP-MS U–Pb dating of calcite is a recently developed approach to direct dating of calcite and can provide precipitation ages for modelling clumped-isotope systematics in calcite veins. In this study, clumped-isotope and LA-ICP-MS U–Pb calcite analyses were combined in basalt-hosted calcite veins from three settings in Scotland. Samples from all three localities yielded precipitation temperatures of ca. 75–115 °C from clumped-isotope analysis, but veins from only two of the sites were dateable, yielding precipitation ages of 224 ± 8 Ma and 291 ± 33 Ma (2σ). Modelling from the dated samples enabled confident interpretation that no closed-system resetting had occurred in these samples. However, the lack of a precipitation age from the third location meant that a range of possible thermal histories had to be modelled meaning that confidence that resetting had not occurred was lower. This highlights the importance of coupling clumped-isotope thermometry and LA-ICP-MS U–Pb calcite dating in determining the temperature of hydrothermal fluids recorded in calcite veins. This paired approach is shown to be robust in constraining the timing and precipitation temperature of calcite formation, and thus for tracking hydrothermal processes.
Journal Article
Love of country : a journey through the Hebrides
\"Over six years, Bunting traveled the Hebrides, exploring their landscapes, histories, and magnetic pull. She delves into the meanings of home and belonging, which in these islands have been fraught with tragedy as well as tenacious resistance. Bunting considers the extent of the islands' influence beyond their shores, finding that their history of dispossession and migration has been central to the British imperial past.\"--Provided by publisher.
Book
Novel track morphotypes from new tracksites indicate increased Middle Jurassic dinosaur diversity on the Isle of Skye, Scotland
Dinosaur fossils from the Middle Jurassic are rare globally, but the Isle of Skye (Scotland, UK) preserves a varied dinosaur record of abundant trace fossils and rare body fossils from this time. Here we describe two new tracksites from Rubha nam Brathairean (Brothers' Point) near where the first dinosaur footprint in Scotland was found in the 1980s. These sites were formed in subaerially exposed mudstones of the Lealt Shale Formation of the Great Estuarine Group and record a dynamic, subtropical, coastal margin. These tracksites preserve a wide variety of dinosaur track types, including a novel morphotype for Skye: Deltapodus which has a probable stegosaur trackmaker. Additionally, a wide variety of tridactyl tracks shows evidence of multiple theropods of different sizes and possibly hints at the presence of large-bodied ornithopods. Overall, the new tracksites show the dinosaur fauna of Skye is more diverse than previously recognized and give insight into the early evolution of major dinosaur groups whose Middle Jurassic body fossil records are currently sparse.
Journal Article
Magmatic Evolution of the Fossil Melanesian Island Arc: Evidence From Lower Miocene Lavas of Malekula Island (Vanuatu)
The subduction zones in the SW Pacific Ocean are some of the most dynamic plate boundaries on Earth with changes in subduction polarity and subduction initiation processes. The New Hebrides island arc formed some 10 million years ago after the Melanesian island arc was abandoned due to the cessation of subduction of the Pacific Plate after collision of oceanic plateaus with the island arc. Parts of the Melanesian island arc occur within the New Hebrides island arc and we show that Miocene volcanic rocks exposed on Malekula island in the New Hebrides island arc consist of island arc tholeiites to alkaline basalts with variable slab contribution. The lava erupted between 22.5 and 16.3 Ma, similar to the Wainimala Group lavas on Fiji representing the eastern portion of the Melanesian island arc. Partial melts from subducted sediments affected a Pacific MORB‐type mantle, but we do not find evidence for a slab component derived from the Ontong Java Plateau or for assimilation of continental crust. Thus, no Miocene subduction of the Ontong Java Plateau occurred beneath Malekula and the basement of the island probably does not consist of continental crust rifted from Australia. The Malekula lava succession resembles that of other portions of the Miocene Melanesian island arc between New Britain and Fiji, indicating continuous subduction of the Pacific plate along this arc. Plain Language Summary The subduction processes in the SW Pacific Ocean changed polarity some 10 million years ago and little is known about the Melanesian island arc that was active before this time. Volcanic rocks of this Melanesian island arc occur on Malekula island in Vanuatu and these have typical compositions of subduction‐related magmas. The lava erupted between 22.5 and 16.3 Ma, similar to lavas on Fiji representing the eastern portion of the Melanesian island arc. There is no chemical or isotopic evidence for subduction of the Ontong Java Plateau or for assimilation of continental crust. Thus, the basement of the island probably does not consist of continental crust rifted from Australia, which was suggested for the neighboring island. Key Points Variable lavas formed between 22 and 16 Ma in the Melanesian island arc, probably as small eruptions in an extensional basin Magmas reflect mixing of Pacific‐type mantle with melt from subducted pelagic sediment, but no assimilation of continental crust Malekula lava resemble other magmatic rocks of the Melanesian island arc and isotopes do not show subduction of Ontong Java Plateau material
Journal Article
Outer Hebrides : the Western Isles of Scotland, from Lewis to Barra
\"Bradt's new guide to the Outer Hebrides: The Western Isles of Scotland, from Lewis to Barra, by experienced writer and journalist Mark Rowe is the only full-size guide to focus solely on the islands of Lewis, Harris, St Kilda, North Uist, Benbecula, South Uist, Eriskay, Barra and Vatersay. Background information is included, from geography and geology to art and architecture, with significant coverage of wildlife, too, as well as all the practical details you could need: when to visit, suggested itineraries, public holidays and festivals, local culture, plus accommodation and where to eat and drink. Walkers, bird-watchers, wildlife photographers, beach lovers and genealogists are all catered for, and this is an ideal guide for those who travel simply with curious minds to discover far-flung places of great cultural, historical and wildlife interest. The Outer Hebrides is an archipelago of 15 inhabited islands and more than 50 others that are free of human footprint. Huge variations in landscape are found across the islands, from Lewisian gneiss, which dates back almost three billion years, to rugged Harris with its magnificent sands running down its western flanks and the windswept, undulating flatness and jagged sea lochs of the Uists. This is a land where Gaelic is increasingly spoken and ancient monuments abound, where stunning seabird colonies and birds of prey can be watched, and where the grassy coastal zones known as the machair are transformed into glorious carpets of wildfllowers in late spring and summer. Whether visiting the Standing Stones of Callanish, the Uig peninsula, Barra's Castle Bay, or historic St Kilda, or if you just want to experience the romance of the Sound of Harris, one of the most beautiful ferry journeys in the world, Bradt's Outer Hebrides: The Western Isles of Scotland, from Lewis to Barra has all the information you need.\" -- Provided by publisher.
Book
Rapid crystallization of precious-metal-mineralized layers in mafic magmatic systems
The solidified remnants of mafic magmatic systems host the greatest concentrations of platinum-group metals in the Earth’s crust. Our understanding of precious-metal mineralization in these intrusive bodies is underpinned by a traditional view of magma chamber processes and crystal mush solidification. However, considerable uncertainty remains regarding the physical and temporal controls on concentrating these critical metals, despite their importance to modern society. We present high-precision 87Sr/86Sr analyses of plagioclase and clinopyroxene from within centimetre-thick precious-metal-enriched layers in the Palaeogene open-system Rum layered intrusion (northwest Scotland). Isotopic heterogeneity is present between plagioclase crystals, between clinopyroxene and plagioclase and within plagioclase crystals throughout the studied section. On the basis of these observations, we demonstrate that platinum-group element mineralization formed by repeated small-volume reactive melt percolation events. The preservation of strontium isotope heterogeneities at 10–100 µm length scales implies cooling of the melts that formed the precious-metal-rich layers occurred at rates greater than 1 °C per year, and cooling to diffusive closure within tens to hundreds of years. Our data highlight the importance of cyclic dissolution–recrystallization events within the crystal mush and raise the prospect that precious-metal-bearing mafic intrusions may form by repeated self-intrusion during cooling and solidification.Mineralization of platinum-group elements in mafic intrusions occurs due to repeated self-intrusion of magma, according to strontium isotope heterogeneities preserved in the Rum layered intrusion, Scotland.
Journal Article
Braided peridotite sills and metasomatism in the Rum Layered Suite, Scotland
The Rum Eastern Layered Intrusion (ELI; Scotland) is an open-system layered intrusion constructed of 16 macro-rhythmic units. Each of the macro-rhythmic units consists of a peridotite base and a troctolite (± gabbro) top, previously attributed to the fractional crystallisation of a single magma batch. This classic paradigm has been challenged, however, with evidence presented for the emplacement of peridotite sills in Units 9, 10, and 14, such as cross-cutting relationships, upward-oriented apophyses, and lateral discontinuities. To test whether the other major peridotites within the ELI represent sills, we have carried out new field, petrographic, and mineral chemical analyses of the peridotites in Units 7, 8 and 9. The peridotites display large- and small-scale cross-cutting relationships with the overlying troctolite, indicative of an intrusive relationship. The peridotites also show large-scale coalescence and lateral spatial discontinuities such that the ELI unit divisions become arbitrary. Harrisite layers and Cr-spinel seams found throughout Units 7, 8, and 9 suggest the peridotites were constructed incrementally via repeated injections of picritic magma. Our observations allow for distinct subtypes of peridotite to be defined, separated by intrusive contacts, allowing for their relative chronology to be determined. Older, poikilitic peridotite, rich in clinopyroxene, is truncated by younger, well-layered peridotite, containing abundant harrisite layers. In addition to the new peridotite subtypes defined in this study, we find strong evidence for laterally oriented metasomatism within clinopyroxene-rich wehrlites at the top of the Unit 8 peridotite. The wehrlites and surrounding peridotites record a complex series of metasomatic reactions that transformed thin picrite sills into clinopyroxene-rich wehrlites without any evidence for the sort of vertical melt movement typically posited in layered intrusions. The observations presented in this study from the ELI cannot be reconciled with the classic magma chamber paradigm and are better explained by the emplacement of composite sills into pre-existing feldspathic cumulate (gabbro or troctolite). The evidence for sill emplacement presented here suggests that the layered complex was constructed by a combination of sill emplacement and metasomatism, forming many of the unusual (often clinopyroxene-rich) lithologies that surround the sills. The broad-scale formation of the layered peridotites via incremental sill emplacement, suggested by the occurrence of upward-oriented apophyses, coalescence, and lateral discontinuity, could be applied to much larger ultramafic intrusions, which might have formed by similar mechanisms.
Journal Article