Geochronology of Paleoproterozoic Augen Gneisses in the Western Gneiss Region, Norway: Evidence for Sveconorwegian Zircon Neocrystallization and Caledonian Zircon Deformation

The Western Gneiss Region, Western Norway, consists of Palaeoproterozoic crust of Baltica ancestry (Baltican Basement), partly subducted to high- and ultrahigh-pressure (HP-UHP) conditions during the Scandian Orogeny between 415 and 395 Ma. The dominant felsic gneisses carry little evidence for the HP-UHP history, but were affected by amphibolite-facies reworking during exhumation. LA-ICPMS and SIMS zircon U-Pb data collected in augen gneiss samples constrain the magmatic and metamorphic geochronology in this crust. Five samples from the eclogite-bearing HP-UHP basement near Molde yield intrusion ages ranging from 1644 ±6 to 1594 ±10 Ma. Two samples of the structurally underlying eclogite-free basement yield ages of 1685 ±18 and 1644 ±13 Ma, and a sample from the infolded Middle Allochthon Risberget Nappe yields an equivalent age of 1676 ±18 Ma. Two samples of the eclogite-bearing basement contain low Th/U neocrystallized zircon with an age of 950 ±26 Ma. This zircon provides the northernmost direct evidence for at least amphibolite-facies Sveconorwegian metamorphism in unquestionable Baltica crust, close to the known “Sveconorwegian boundary” in the Western Gneiss Region.The Western Gneiss Region (1686-1594 Ma magmatism), the Eastern Segment of the Sveconorwegian Orogen (1795-1640 Ma magmatism), and the Idefjorden terrane hosting the type Gothian active margin magmatism (1659-1520 Ma) probably represent three distinct Proterozoic growth zones of Baltica into which Sveconorwegian reworking propagated. Samples of the eclogite-bearing basement lack Scandian neocrystallized zircon, but do show partial recrystallization of zircon. Paired CL and EBSD images indicate that zircon crystals underwent crystal-plastic deformation during the Scandian subduction-exhumation cycle. They illustrate a relationship between crystal-plastic deformation by dislocation creep, fading of oscillatory growth zoning and loss of radiogenic lead

The chemistry of quartz in granitic pegmatites of southern Norway: Petrogenetic and economic implications

This is the author accepted manuscript. The final version is available from Society of Economic Geologists via the DOI in this record.Trace element concentrations in quartz from 188 granitic pegmatites in the Froland and Evje-Iveland pegmatite fields, southern Norway, have been determined to establish exploration targets for high-purity quartz and to gain a better understanding of the genesis of pegmatites hosting these deposits. Both pegmatite fields were formed during the Sveconorwegian (Grenvillian) orogeny (1145-900 Ma) at the western margin of the Fennoscandian Shield. In situ raster analyses within single quartz crystals were undertaken by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS); spot size 75 μm) to assess levels of lattice-bound impurities, rather than mineral and fluid inclusions that are relatively easily removed during high-purity quartz processing. Quartz in the Froland pegmatites has relatively pure and homogeneous compositions containing 46 ± 24 μgg-1Al, 8 ± 3 μgg-1Ti, 1.4 ± 0.8 μgg-1Ge, and 11 ± 7 μgg-1Li. The Ti-in-quartz geothermobarometer gives an average pegmatite crystallization temperature of 537° ± 39°C. Temperature estimates are highest along the northwestern margin of the pegmatite field (>550°C), whereas the most differentiated pegmatites occur toward the northeast. The area of greatest economic potential for high-purity quartz lies just north of the central part of the field where individual pegmatites contain >1 million metric tons (Mt) quartz with low average trace element contents of 67 ± 11 μgg-1. From mineral-chemical criteria, and a range of other geologic factors, we propose that pegmatite melts in the Froland field were generated by fluid-present crustal melting at about 1060 Ma, in zones of localized high-strain deformation during progressive thrusting along the Porsgrunn-Kristiansand fault zone. Quartz in the Evje-Iveland pegmatites has more variable compositions with 69 ± 57 μgg-1Al, 19 ± 11 μgg-1Ti, 2.3 ± 1.8 μgg-1Ge, and 7 ± 5 μgg-1Li. From its Ti content, it crystallized at temperatures of 613° ± 70°C. The regional spatial distribution of Ti-in-quartz temperatures appears irregular mainly due to the scattered distributions of chemical evolved pegmatites with "amazonite"-"cleavelandite" replacement zones, which show crystallization temperatures down to 442°C. Quartz from the Evje-Iveland pegmatites is unlikely to be of current economic interest due to its moderate to high trace element contents, heterogeneous chemistry, and low volume. The Evje-Iveland pegmatites show no apparent genetic link to a granite intrusion; instead they probably formed as a result of partial melting at the depth of their amphibolite country rocks at around 910 Ma. This is related to a regional low-pressure/high-temperature metamorphic event at about 930 to 920 Ma.Geological Survey of Norway in Trondhei

The source of Dalradian detritus in the Buchan Block, NE Scotland: Application of new tools to detrital datasets

Detrital zircons from four samples of upper Dalradian metasedimentary rocks from the Buchan Block in the NE Grampian Highlands of Scotland were analysed by laser ablation inductively coupled plasma mass spectrometry to establish their U–Pb age and trace element composition. The analysed grains (magmatic cores) mainly yield concordant ages ranging from Neoproterozoic to Eoarchaean. Kernel density plots of the data show pronounced peaks in the late Mesoproterozoic, Palaeoproterozoic and Neoarchaean eras. The data are indistinguishable from detrital zircon age spectra from Dalradian rocks elsewhere, an interpretation supported by application of a non-parametric multidimensional scaling algorithm, and are consistent with a Laurentian source. Similar to existing studies from other Dalradian rocks, the age spectra from the Buchan Block reveal an increase in the relative proportion of older detritus with time, suggesting derivation from late Mesoproterozoic (Grenville) then Palaeoproterozoic orogens before widespread exposure and denudation of their Archaean basement rocks. Application of a novel approach to estimate the most likely time of radiogenic-Pb loss indicates that some detrital zircon grains were affected by element mobility around 470–450 Ma as a result of Grampian orogenesis

Growth and collapse of a deeply eroded orogen : insights from structural, geophysical, and geochronological constraints on the Pan-African evolution of NE Mozambique

This paper presents results of a large multidiciplinary geological mapping project in NE Mozambique, with a focus on the structural evolution of this part of the East African Orogen (EAO). It integrates field structural studies with geophysical interpretations and presents new geochronological data. The tectonic architecture of NE Mozambique can be subdivided into five megatectonic units on the basis of lithology, structure and geochronology: unit 1, Paleoproterozoic Ponta Messuli Complex in the extreme NW corner of NE Mozambique, which represents the local NW foreland to the EAO; unit 2, a collage of Mesoproterozoic metamorphic complexes, which forms the basement to unit 3, a stack of Neoproterozoic, NW directed imbricate thrust nappes named here the ‘‘Cabo Delgado Nappe Complex’’ (CDNC); unit 4, restricted Neoproterozoic metasedimentary basins; and unit 5, two exotic Neoproterozoic granulite me´ lange complexes. The units were assembled during a long and complex history of NWdirected shortening, which commenced with nappe stacking and emplacement of the CDNC over the Mesoproterozoic basement terranes toward the NW foreland. It is proposed that the CDNC and the Eastern Granulites farther north in Tanzania are remnants of Neoproterozoic volcanic arcs and microcontinents formed ‘‘outboard’’ of the Mesoproterozoic continent after 596 ± 11 Ma. Field and potential field geophysical data show that the nappes were folded by regional-scale NE–SW trending folds that formed in response to a later stage of the same shortening episode and this episode gave rise to the Lurio Belt, a prominent structural feature of northern Mozambique and a key element (often as suture zone) in many Gondwana reconstructions. The Lurio Belt is here interpreted as a structure generated during folding of the CDNC during later stages of the progressive shortening event. It is, however, a repeatedly reactivated shear zone, probably at the site of an older (Mesoproterozoic?) discontinuity, with an intense pure shear deformation history. It is cored by strongly attenuated lenses of a granulitic tectonic me´lange, the Ocua Complex (megatectonic unit 5) and is intruded by Late Pan-African granitoids of the Malema Suite. The compressional phase of the orogen was postdated by NW–SE directed extension. New U-Pb zircon and monazite dates show that extension was initiated at circa 540 Ma in the eastern Lurio Belt. It is argued that extension was the result of a major episode of orogenic collapse of the EAO, initiated by gravitational instabilities resulting from crustal thickening during the shortening phase

Cellphone-Based Hand-Held Microplate Reader for Point-of-Care Testing of Enzyme-Linked Immunosorbent Assays

Standard microplate based enzyme-linked immunosorbent assays (ELISA) are widely utilized for various nanomedicine, molecular sensing, and disease screening applications, and this multiwell plate batched analysis dramatically reduces diagnosis costs per patient compared to nonbatched or nonstandard tests. However, their use in resource-limited and field-settings is inhibited by the necessity for relatively large and expensive readout instruments. To mitigate this problem, we created a hand-held and cost-effective cellphone-based colorimetric microplate reader, which uses a 3D-printed optomechanical attachment to hold and illuminate a 96-well plate using a light-emitting-diode (LED) array. This LED light is transmitted through each well, and is then collected via 96 individual optical fibers. Captured images of this fiber-bundle are transmitted to our servers through a custom-designed app for processing using a machine learning algorithm, yielding diagnostic results, which are delivered to the user within ∼1 min per 96-well plate, and are visualized using the same app. We successfully tested this mobile platform in a clinical microbiology laboratory using FDA-approved mumps IgG, measles IgG, and herpes simplex virus IgG (HSV-1 and HSV-2) ELISA tests using a total of 567 and 571 patient samples for training and blind testing, respectively, and achieved an accuracy of 99.6%, 98.6%, 99.4%, and 99.4% for mumps, measles, HSV-1, and HSV-2 tests, respectively. This cost-effective and hand-held platform could assist health-care professionals to perform high-throughput disease screening or tracking of vaccination campaigns at the point-of-care, even in resource-poor and field-settings. Also, its intrinsic wireless connectivity can serve epidemiological studies, generating spatiotemporal maps of disease prevalence and immunity

Reply to Guy et al.: Support for a bottleneck in the 2011 Escherichia coli O104:H4 outbreak in Germany

In our paper (1), we analyzed isolates from the Escherichia coli O104:H4 outbreaks in Germany and France in May to July 2011. We concluded that, although the German outbreak was larger, the German isolates represent a clade within the greater diversity of the French outbreak. We proposed several hypotheses to explain these findings, including that the lineage leading to the German outbreak went through a narrow bottleneck that purged diversity. Guy et al. (2) report the genomes of eight additional E. coli O104:H4 isolates sampled from the German outbreak. By focusing on the numbers of SNPs in their samples, they suggest that the German outbreak is more diverse than we reported and is similar to the French outbreak. In fact, Guy et al.’s data (2) strongly support our conclusion that the German outbreak represents a clade within the diversity

Zircon ages in granulite facies rocks: decoupling from geochemistry above 850 °C?

Granulite facies rocks frequently show a large spread in their zircon ages, the interpretation of which raises questions: Has the isotopic system been disturbed? By what process(es) and conditions did the alteration occur? Can the dates be regarded as real ages, reflecting several growth episodes? Furthermore, under some circumstances of (ultra-)high-temperature metamorphism, decoupling of zircon U–Pb dates from their trace element geochemistry has been reported. Understanding these processes is crucial to help interpret such dates in the context of the P–T history. Our study presents evidence for decoupling in zircon from the highest grade metapelites (> 850 °C) taken along a continuous high-temperature metamorphic field gradient in the Ivrea Zone (NW Italy). These rocks represent a well-characterised segment of Permian lower continental crust with a protracted high-temperature history. Cathodoluminescence images reveal that zircons in the mid-amphibolite facies preserve mainly detrital cores with narrow overgrowths. In the upper amphibolite and granulite facies, preserved detrital cores decrease and metamorphic zircon increases in quantity. Across all samples we document a sequence of four rim generations based on textures. U–Pb dates, Th/U ratios and Ti-in-zircon concentrations show an essentially continuous evolution with increasing metamorphic grade, except in the samples from the granulite facies, which display significant scatter in age and chemistry. We associate the observed decoupling of zircon systematics in high-grade non-metamict zircon with disturbance processes related to differences in behaviour of non-formula elements (i.e. Pb, Th, U, Ti) at high-temperature conditions, notably differences in compatibility within the crystal structure

Need and importance of health protection training in Nepal

By investing in health protection, the health of the nation can be safeguarded from future threats of uncontrolled infectious disease epidemics and disasters