Basement-cover relations and internal structure of the Cape Smith klippe: A 1.9 Ga greenstone belt in northern Quebec, Canada

The Cape Smith Belt is a 380x60 km tectonic klippe composed of greenschistto amphibolite-grade mafic and komatiitic lava flows and fine-grained quartzose sediment, intruded by minor syn- to post-tectonic granitoids. Previously studied transects in areas of relatively high structural level show that the belt is constructed of seven or more north-dipping thrust sheets which verge toward the Superior Province (Archean) foreland in the south and away from an Archean basement massif (Kovik Antiform) external to the Trans-Hudson Orogen (Early Proterozoic) in the north. A field project (mapping and structural-stratigraphic-metamorphic studies) directed by MRS was begun in 1985 aimed at the structurally deeper levels of the belt and underlying basement, which are superby exposed in oblique cross-section (12 km minimum structural relief) at the west-plunging eastern end of the belt. Mapping now complete of the eastern end of the belt confirms that all of the metavolcanic and most of the metasedimentary rocks are allochthonous with respect to the Archean basement, and that the thrusts must have been rooted north of Kovik Antiform. The main findings follow

Quantitative elemental mapping of granulite-facies monazite: Textural insights and implications for petrochronology

Texturally complex monazite grains contained in two granulite-facies pelitic migmatites from southern Baffin Island, Arctic Canada, were mapped by laser ablation-inductively coupled plasma-mass spectrometry (using spot sizes < 5 µm) to quantitatively determine the spatial variation in trace element chemistry (with up to 1883 analyses per grain). The maps highlight the chemical complexity of monazite grains that have experienced multiple episodes of growth, resorption and chemical modification by dissolution-precipitation during high-grade metamorphism. Following detailed chemical characterisation of monazite compositional zones, a related U-Pb dataset is re-interpreted, allowing petrologically-significant ages to be extracted from a continuum of concordant data. Synthesis of these data with pseudosection modelling of prograde and peak conditions allows for the temporal evolution of monazite trace element chemistry to be placed in the context of the evolving P-T conditions and major phase assemblage. This approach enables a critical evaluation of three commonly used petrochronological indicators: linking Y to garnet abundance, the Eu anomaly to feldspar content, and Th/U to anatectic processes. Europium anomalies and Th/U behave in a relatively systematic fashion, suggesting that they are reliable petrochronological witnesses. However, Y systematics are variable, both within domains interpreted to have grown in a single event, between grains interpreted to be part of the same age population, and between samples that experienced similar metamorphic conditions and mineral assemblages. These observations caution against generalised petrological interpretations on the basis of Y content, as it suggests Y concentrations in monazite are controlled by domainal equilibria. The results reveal a ~45 Myr interval between prograde metamorphism and retrograde melt crystallisation in the study area, emphasising the long-lived nature of heat flow in high-grade metamorphic terranes. Such long timescales of metamorphism would be assisted by the growth, retention and dominance of high-Th suprasolidus monazite, as observed in this study, contributing to the radiogenic heating budget of mid- to lower-crustal environments. Careful characterisation of monazite grains suggests that continuum-style U-Pb datasets can be decoded to provide insights into the duration of metamorphic processes.Natural Sciences and Engineering Research Council Visiting Fellowship Isaac Newton Trust Research Grant (RG74916

Contextualising the Permian Sumdo eclogite belt, Lhasa block, Tibet

Abstract HKT-ISTP 2013 A

Reaction of Alkynyl- And Alkenyltrifluoroborates with Propargyldicobalt Cations: Alkynylation, Alkenylation, and Cyclopropanation Product Pathways

The Lewis acid-mediated Nicholas reactions of propargyl acetate–Co2(CO)6 complexes with a series of potassium alkynyltrifluoroborates and potassium alkenyltrifluoroborates are described. Alkynyltrifluoroborates directly alkynylate the intermediate propargyldicobalt cations. In contrast, alkenyltrifluoroborates proceed through one of the three modes of dominant reactivity: C-2-substituted alkenyltrifluorobrates directly alkenylate, predominantly with the retention of stereochemistry. C-1-substituted alkenyltrifluoroborates alkenylate at C-2. Potassium vinyltrifluoroborate incorporates a cyclopropane at the site propargyl to alkynedicobalt. Computational analysis of these systems explains the differential modes of reactivity of alkenyltrifluoroborates and outlines the probable mechanisms for the formation of each product

Ptarmigan Fiord basement-cover thrust imbricates, Baffin Island, Nunavut

The rocks at Ptarmigan Fiord on the Hall Peninsula of Baffin Island underwent midcrustal deformation during the formation of the Paleoproterozoic Trans-Hudson Orogen. The structural style in the region is dominated by imbricate panels of Archean basement orthogneiss and Paleoproterozoic supracrustal strata, interpreted to have been deformed by thick- skinned ductile thrusting. Basement rocks comprise amphibolite-facies metatonalite, metagranodiorite, metaquartz-diorite and metamonzogranite, and cover rocks comprise amphibolite-facies migmatitic pelitic and semipelitic schist, psammitic schist, amphibolite, calcsilicate and quartzite. The S 1a penetrative foliation is variably present in basement rocks and consis- tently present in cover rocks, and is defined by alignment of biotite, sillimanite and leucogranite that formed before and dur- ing the thermal metamorphic peak. The S 1a foliation was deformed by F 1b isoclinal folds with an amplitude of 100 m. These structures are interpreted as forming during a D 1 east-west crustal shortening event. Basement and cover imbrication oc- curred after the thermal metamorphic peak and is interpreted as D 2 thick-skinned ductile thrusting. Ductile thrust faults at the base of seven basement-cover slices are identified on the basis of repetition of units and strain localization, and are inter- preted as predominantly south-to-southeast verging on the basis of shear-sense indicators. There are two structural panels of D 2 thrust imbricates, one in the northwestern part of the map area and one in the eastern part of the map area. Map-scale crosscutting relationships indicate that the northwestern panel overthrusted the eastern panel on a southeasterly T 2c -di- rected thrust fault, following a F 2b folding event that folded the T 2a basement-cover thrust imbricates in the eastern panel. The Ptarmigan Fiord area contains a world-class exposure of thick-skinned structures as they are spectacularly delineated by belts of distinctive grey-weathering Archean basement rocks and brown- to black-weathering Paleoproterozoic supra- crustal rocks

Development And Field Application Of A Single Rotor Design Dry Gas Seal.

LecturePg. 107-116Improving centrifugal compressor seal performance and reliability can be accomplished through development of new technology and/or by improvement of existing technology. An improved dry gas lubricating seal of single rotor design has been designed for high pressure gas compressors. A more durable seal of simpler design has been created through implementation of ductile materials and reduction of components. Currently, the tandem dry gas seal configuration is the accepted standard for high pressure natural gas pipeline compressor applications. These applications still suffer problems with process and lube oil contamination, brittle fracture of carbide materials, and explosive decompression of 0-rings. Real costs associated with these problems are considerable. Development and potential benefits of the single rotor design seal, along with field application, in a high pressure natural gas centrifugal compressor is discussed

Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question

Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a ∆ R of 140 ± 30 14C years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25 are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full ice-shelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; ∆ R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge. At the end of HS1, IP25, brassicasterol and benthic forams indicative of sea-ice edge productivity increase, indicating warming interstadial conditions. Within the Bølling/Allerød interstadial a strong rise in IP25 content and IRD spikes rich in detrital carbonate from northern Baffin Bay indicate that northern Baffin Bay ice streams were retreating and provides evidence for increased open water, advection of Atlantic Water in the West Greenland Current, and formation of an IRD belt along the W. Greenland margin

Molecular probe technology detects bacteria without culture

<p>Abstract</p> <p>Background</p> <p>Our ultimate goal is to detect the entire human microbiome, in health and in disease, in a single reaction tube, and employing only commercially available reagents. To that end, we adapted molecular inversion probes to detect bacteria using solely a massively multiplex molecular technology. This molecular probe technology does not require growth of the bacteria in culture. Rather, the molecular probe technology requires only a sequence of forty sequential bases unique to the genome of the bacterium of interest. In this communication, we report the first results of employing our molecular probes to detect bacteria in clinical samples.</p> <p>Results</p> <p>While the assay on Affymetrix GenFlex Tag16K arrays allows the multiplexing of the detection of the bacteria in each clinical sample, one Affymetrix GenFlex Tag16K array must be used for each clinical sample. To multiplex the clinical samples, we introduce a second, independent assay for the molecular probes employing Sequencing by Oligonucleotide Ligation and Detection. By adding one unique oligonucleotide barcode for each clinical sample, we combine the samples after processing, but before sequencing, and sequence them together.</p> <p>Conclusions</p> <p>Overall, we have employed 192 molecular probes representing 40 bacteria to detect the bacteria in twenty-one vaginal swabs as assessed by the Affymetrix GenFlex Tag16K assay and fourteen of those by the Sequencing by Oligonucleotide Ligation and Detection assay. The correlations among the assays were excellent.</p

Comparison of earthquake-triggered turbidites from the Saguenay (Eastern Canada) and Reloncavi (Chilean margin) Fjords: implications for paleoseismicity and sedimentology

International audienceHigh-resolution seismic profiles along with physical and sedimentological properties of sediment cores from the Saguenay (Eastern Canada) and Reloncavi (Chile) Fjords allowed the identification of several decimeter to meter-thick turbidites. In both fjords, the turbidites were associated with large magnitude historic and pre-historic earthquakes including the 1663 AD (M > 7) earthquake in the Saguenay Fjord, and the 1960 (M 9.5), 1837 (M ~ 8) and 1575 AD major Chilean subduction earthquakes in the Reloncavi Fjord. In addition, a sand layer with exoscopic characteristics typical of a tsunami deposit was observed immediately above the turbidite associated with the 1575 AD earthquake in the Reloncavi Fjord and supports both the chronology and the large magnitude of that historic earthquake. In the Saguenay Fjord, the earthquake-triggered turbidites are sometimes underlying a hyperpycnite associated with the rapid breaching and draining of a natural dam formed by earthquake-triggered landslides. Similar hyperpycnal floods were also recorded in historical and continental geological archives for the 1960 and 1575 AD Chilean subduction earthquakes, highlighting the risk of such flood events several weeks or months after main earthquake. In both fjords, as well as in other recently recognized earthquake-triggered turbidites, the decimeter-to meter-thick normally-graded turbidites are characterized by a homogeneous, but slightly fining upward tail. Finally, this paper also emphasizes the sensitivity of fjords to record historic and pre-historic seismicity