ALBERT

Description: The chemistry of mafic volcanic rocks and minor intrusions erupted on continents can be used to define sub-continental asthenospheric and lithospheric mantle sources. Data have been collated from Antarctica and the Falkland Islands (adjacent in Gondwana) in order to identify lithospheric mantle sources beneath the continent. The lithosphere-derived magmas include lamproitic and some lamprophyric rocks and end-members in basaltic suites that are interpreted as mixtures of magmas from lithospheric and asthenospheric sources. The lithosphere-derived mafic rocks from Archaean to Middle Proterozoic cratonic and circumcratonic areas of East Antarctica have time-corrected {varepsilon}Nd values of -20 to -3. This demands isolation of the LREE-enriched sources within pockets of stable sub-cratonic lithosphere for more than 1 Ga, consistent with the lithosphere thickness up to 250 km imaged by seismic tomography. In contrast, lithosphere-derived mafic rocks from Middle Proterozoic to Early Palaeozoic areas of West Antarctica, Victoria Land and the Falkland Islands that formed the Gondwana continental margin, have time-corrected {varepsilon}Nd values of -3.6 to +3.5, implying more recent isolation from asthenosphere. In terms of mantle reservoirs, cratonic and circumcratonic areas trend toward EMI, with EMII possibly being a minor component. In contrast, Gondwana margin areas trend toward EMII, with EMI being, at most, a very minor component.

Description: The Mesozoic fore-arc of the Antarctic Peninsula is exposed along its west coast. On Adelaide Island, a 2–3 km succession of turbiditic coarse sandstones and volcanic rocks is exposed. Four U–Pb (zircon) ages are presented here that, in combination with a new stratigraphy, have permitted a robust chrono- and lithostratigraphy to be constructed, which in turn has allowed tentative correlations to be made with the Fossil Bluff Group of Alexander Island, where the ‘type’ fore-arc sequences are described. The lithostratigraphy of Adelaide Island includes the definition of five volcanic/sedimentary formations. The oldest formation is the Buchia Buttress Formation (149.5 ± 1.6 Ma) and is correlated with the Himalia Ridge Formation of Alexander Island. The sandstone–conglomerate dominated succession of the Milestone Bluff Formation (113.9 ± 1.2 Ma) is tentatively correlated with the Pluto Glacier Formation of Alexander Island. Three dominantly volcanic formations are recognized on Adelaide Island, akin to the volcanic rocks of the Alexander Island Volcanic Group; the Mount Liotard Formation is formed of 2 km of basaltic andesite lavas, whilst the Bond Nunatak Formation is also dominated by basaltic andesite lavas, but interbedded with volcaniclastic rocks. The Reptile Ridge Formation has been dated at 67.6 ± 0.7 Ma and is characterized by hydrothermally altered rhyolitic crystal-lithic tuffs. Tentative correlations between Adelaide Island and Alexander Island preclude the two areas forming part of distinct terranes as has been suggested previously, and a proximal source for volcaniclastic sediments also indicates an exotic terrane origin is unlikely.

Description: New geological mapping combined with U–Pb ion microprobe zircon geochronology on the isolated but locally extensive exposures of crystalline basement inliers of eastern Graham Land has greatly improved our understanding of the region’s early crustal evolution and has allowed a more thorough evaluation of Patagonia–Antarctic Peninsula connections prior to Gondwana break-up. At Eden Glacier, diorite gneisses yield Early Ordovician protolith ages of 487 ± 3 and 485 ± 3 Ma and represent the oldest in situ rocks recorded on the Antarctic Peninsula, and indicate a significant spatial extension of Famatinian-age magmatism of Patagonia. Zircon overgrowths in the Early Ordovician protoliths and granitic leucosomes developed within them record two phases of Permian metamorphism at c. 275 and c. 257 Ma, coincident in part with diorite plutonism of the area at 272 ± 2 Ma. At Adie Inlet, granitic leucosomes from paragneiss have been dated at 276 ± 3 Ma, and these are in turn cut by 257 ± 3 Ma xenolith-rich diorite gneiss. The diorite intruded during a second phase of deformation, which folded the paragneiss leucosomes into tight folds. This whole assembly is cut by intensely brecciated megacrystic granodiorite, which yielded a 259 ± 3 Ma age. South of Cabinet Inlet a very different sequence of events is evident, with Triassic magmatism at c. 236 Ma extensive along the Joerg Peninsula. Migmatitic leucosomes are dated at c. 224 Ma and magmatism and deformation events apparently continued to c. 209 Ma at Cape Casey. Our data indicate that the Devonian and Carboniferous magmatism at Target Hill, considered to represent the ‘classic’ basement complex of the Antarctic Peninsula, is not representative regionally. The Target Hill crustal block contains a major break along Cabinet Inlet; to the north, Ordovician and Permian protoliths were variably migmatized during two episodes of Permian deformation and metamorphism, whereas to the south, Triassic protoliths and Triassic metamorphism are encountered.Supplementary material: U–Pb isotopic data are available at http://www.geolsoc.org.uk/SUP18526.

Description: TLS/FUS (TLS) is a multifunctional protein implicated in a wide range of cellular processes, including transcription and mRNA processing, as well as in both cancer and neurological disease. However, little is currently known about TLS target genes and how they are recognized. Here, we used ChIP and promoter microarrays to identify genes potentially regulated by TLS. Among these genes, we detected a number that correlate with previously known functions of TLS, and confirmed TLS occupancy at several of them by ChIP. We also detected changes in mRNA levels of these target genes in cells where TLS levels were altered, indicative of both activation and repression. Next, we used data from the microarray and computational methods to determine whether specific sequences were enriched in DNA fragments bound by TLS. This analysis suggested the existence of TLS response elements, and we show that purified TLS indeed binds these sequences with specificity in vitro. Remarkably, however, TLS binds only single-strand versions of the sequences. Taken together, our results indicate that TLS regulates expression of specific target genes, likely via recognition of specific single-stranded DNA sequences located within their promoter regions.

Description: Rare earth elements (REEs) generate characteristic absorption features in visible to shortwave infrared (VNIR-SWIR) reflectance spectra. Neodymium (Nd) has among the most prominent absorption features of the REEs and thus represents a key pathfinder element for the REEs as a whole. Given that the world’s largest REE deposits are associated with carbonatites, we present spectral, petrographic, and geochemical data from a predominantly carbonatitic suite of rocks that we use to assess the feasibility of imaging REE deposits using remote sensing. Samples were selected to cover a wide range of extents and styles of REE mineralization, and encompass calcio-, ferro- and magnesio-carbonatites. REE ores from the Bayan Obo (China) and Mountain Pass (United States) mines, as well as REE-rich alkaline rocks from the Motzfeldt and Ilímaussaq intrusions in Greenland, were also included in the sample suite. The depth and area of Nd absorption features in spectra collected under laboratory conditions correlate positively with the Nd content of whole-rock samples. The wavelength of Nd absorption features is predominantly independent of sample lithology and mineralogy. Correlations are most reliable for the two absorption features centered at ~744 and ~802 nm that can be observed in samples containing as little as ~1,000 ppm Nd. By convolving laboratory spectra to the spectral response functions of a variety of remote sensing instruments we demonstrate that hyperspectral instruments with capabilities equivalent to the operational Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) and planned Environmental Mapping and Analysis Program (EnMAP) systems have the spectral resolutions necessary to detect Nd absorption features, especially in high-grade samples with economically relevant REE accumulations (Nd 〉 30,000 ppm). Adding synthetic noise to convolved spectra indicates that correlations between Nd absorption area and whole-rock Nd content only remain robust when spectra have signal-to-noise ratios in excess of ~250:1. Although atmospheric interferences are modest across the wavelength intervals relevant for Nd detection, most REE-rich outcrops are too small to be detectable using satellite-based platforms with 〉30-m spatial resolutions. However, our results indicate that Nd absorption features should be identifiable in high-quality, airborne, hyperspectral datasets collected at meter-scale spatial resolutions. Future deployment of hyperspectral instruments on unmanned aerial vehicles could enable REE grade to be mapped at the centimeter scale across whole deposits.

Description: Rare earth elements (REEs) generate characteristic absorption features in visible to shortwave infrared (VNIR-SWIR) reflectance spectra. Neodymium (Nd) has among the most prominent absorption features of the REEs and thus represents a key pathfinder element for the REEs as a whole. Given that the world’s largest REE deposits are associated with carbonatites, we present spectral, petrographic, and geochemical data from a predominantly carbonatitic suite of rocks that we use to assess the feasibility of imaging REE deposits using remote sensing. Samples were selected to cover a wide range of extents and styles of REE mineralization, and encompass calcio-, ferro- and magnesio-carbonatites. REE ores from the Bayan Obo (China) and Mountain Pass (United States) mines, as well as REE-rich alkaline rocks from the Motzfeldt and Ilímaussaq intrusions in Greenland, were also included in the sample suite. The depth and area of Nd absorption features in spectra collected under laboratory conditions correlate positively with the Nd content of whole-rock samples. The wavelength of Nd absorption features is predominantly independent of sample lithology and mineralogy. Correlations are most reliable for the two absorption features centered at ~744 and ~802 nm that can be observed in samples containing as little as ~1,000 ppm Nd. By convolving laboratory spectra to the spectral response functions of a variety of remote sensing instruments we demonstrate that hyperspectral instruments with capabilities equivalent to the operational Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) and planned Environmental Mapping and Analysis Program (EnMAP) systems have the spectral resolutions necessary to detect Nd absorption features, especially in high-grade samples with economically relevant REE accumulations (Nd 〉 30,000 ppm). Adding synthetic noise to convolved spectra indicates that correlations between Nd absorption area and whole-rock Nd content only remain robust when spectra have signal-to-noise ratios in excess of ~250:1. Although atmospheric interferences are modest across the wavelength intervals relevant for Nd detection, most REE-rich outcrops are too small to be detectable using satellite-based platforms with 〉30-m spatial resolutions. However, our results indicate that Nd absorption features should be identifiable in high-quality, airborne, hyperspectral datasets collected at meter-scale spatial resolutions. Future deployment of hyperspectral instruments on unmanned aerial vehicles could enable REE grade to be mapped at the centimeter scale across whole deposits.

Description: The Antarctic Peninsula (AP) consists of a long lived and uniquely well preserved magmatic arc system. The broad tectonic structure of the AP arc is well understood. However, magmatic processes occurring along the arc are only constrained by regional geophysical and relatively sparse geological data. Key questions remain about the timing, volume, and structural controls on magma emplacement. We present new high resolution aeromagnetic data across Adelaide Island, on the western margin of the AP revealing the complex structure of the AP arc/forearc boundary. Using digital enhancement, 2-D modelling and 3-D inversion we constrain the form of the magnetic sources at the arc/forearc boundary. Our interpretation of these magnetic data, guided by geological evidence and new zircon U-Pb dating, suggests significant Palaeogene to Neogene magmatism formed ~25 per cent of the upper crust in this region (~7500 km 3 ). Significant structural control on Neogene magma emplacement along the arc/forearc boundary is also revealed. We hypothesize that this Neogene magmatism reflects mantle return flow through a slab window generated by Late Palaeogene cessation of subduction south of Adelaide Island. This mantle process may have affected the final stages of arc magmatism along the AP margin.

Description: DNA binding proteins find their cognate sequences within genomic DNA through recognition of specific chemical and structural features. Here we demonstrate that high-resolution DNase I cleavage profiles can provide detailed information about the shape and chemical modification status of genomic DNA. Analyzing millions of DNA backbone hydrolysis events on naked...