The Mesoarchaean Akia terrane, West Greenland, revisited : new insights based on spatial integration of geophysics, field observation, geochemistry and geochronology

NJG thanks Australian Research Council grant FL160100168 for financial support.The northern part of the North Atlantic Craton (NAC) in southern West Greenland comprises a large tract of exposed Meso-Neoarchaean continental crust, divided into the ca 3300–2900 Ma Akia and ca 2900–2500 Ma Tuno terranes. We combine aeromagnetic, stream sediment geochemical, new litho-chemical and zircon geochronological data with previously published data to re-evaluate the crustal architecture and evolution of the Akia terrane and its boundary towards the Tuno terrane. The previously recognised, but overlooked, Alanngua complex, situated between the Akia and Tuno terranes is bounded by aeromagnetic lineaments interpreted as Neoarchaean shear zones and has a distinct spectrum of Neoarchaean magmatic and metamorphic zircon ages that are rare in the Akia terrane. The Alanngua complex comprises components derived from both the Akia and Tuno terranes and is interpreted as a tectonic melange created during the Neoarchaean assembly of the NAC. Within the Akia terrane, the chemistry of orthogneiss samples indicate that a large percentage is too mafic to classify as TTG s.s., implying that not only partial melting of mafic crust, but also some yet unaddressed mantle involvement is necessary in their formation. Previous models for the generation of the ca. 3015–2990 Ma quartz-dioritic Finnefjeld and Taserssuaq complexes conflict with their geochemical variation. The complexes are spatially associated with strong aeromagnetic responses that are interpreted to reflect a large gabbro-diorite intrusion, and we propose that the protoliths of the Finnefjeld and Taserssuaq complexes are genetically linked to such intrusion. Formed at same time are carbonatite, high-Mg gabbro and tonalite-trondhjemite, and we propose that this wide spectrum of rocks could have formed by lithospheric and crustal melting in response to asthenospheric upwelling possibly in an extensional setting. Periods of extensive magmatism in the Akia terrane were previously recognised at ca. 3220-3180 Ma and 3070-2970 Ma. We now subdivide the latter period into three episodes: juvenile basaltic-andesitic volcanism at 3070–3050 Ma; tonalitic and dioritic plutonism at 3050–3020 Ma, and gabbroic-dioritic plus tonalitic-trondhjemitic plutonism at 3020–2985 Ma. This last episode was immediately followed by crustal reworking during collision at 2980–2950 Ma.Publisher PDFPeer reviewe

Disease status, reasons for discontinuation and adverse events in 1038 Italian children with juvenile idiopathic arthritis treated with etanercept

Background: Data from routine clinical practice are needed to further define the efficacy and safety of biologic medications in children with juvenile idiopathic arthritis (JIA). The aim of this analysis was to investigate the disease status, reasons for discontinuation and adverse events in Italian JIA patients treated with etanercept (ETN). Methods: In 2013, all centers of the Italian Pediatric Rheumatology Study Group were asked to make a census of patients given ETN after January 2000. Patients were classified in three groups: group 1 = patients still taking ETN; group 2 = patients discontinued from ETN for any reasons; group 3 = patients lost to follow-up while receiving ETN. All three groups received a retrospective assessment; patients in group 1 also underwent a cross-sectional assessment. Results: 1038 patients were enrolled by 23 centers: 422 (40.7%) were in group 1, 462 (44.5%) in group 2, and 154 (14.8%) in group 3. Median duration of ETN therapy was 2.5 years. At cross-sectional assessment, 41.8% to 48.6% of patients in group 1 met formal criteria for inactive disease, whereas 52.4% of patients in group 2 and 55.8% of patients in group 3 were judged in clinical remission by their caring physician at last visit. A relatively greater proportion of patients with systemic arthritis were discontinued or lost to follow-up. Parent evaluations at cross-sectional visit in group 1 showed that 52.4% of patients had normal physical function, very few had impairment in quality of life, 51.2% had no pain, 76% had no morning stiffness, and 82.7% of parents were satisfied with their child's illness outcome. Clinically significant adverse events were reported for 27.8% of patients and ETN was discontinued for side effects in 9.5%. The most common adverse events were new onset or recurrent uveitis (10.2%), infections (6.6%), injection site reactions (4.4%), and neuropsychiatric (3.1%), gastrointestinal (2.4%), and hematological disorders (2.1%). Ten patients developed an inflammatory bowel disease and 2 had a malignancy. One patient died of a fulminant streptococcal sepsis. Conclusions: Around half of the patients achieved complete disease quiescence under treatment with ETN. The medication was overall well tolerated, as only one quarter of patients experienced clinically significant adverse events and less than 10% had treatment discontinued for toxicity

Geophysical targeting of Fe-oxide Cu-Au deposits in the northern fennoscandian sheild

In the last decades Fe-Oxide Cu-Au deposits have been discovered and developed in Australia, South America and Canada. This class of mineral deposits is also present in northern Sweden and thus represents a potential target for improving the mineral production of the country. The project aims at defining a geophysical signature of IOCG deposits from regional scale to local scale by using available geophysical data and newly measured petrophysical data. The Kiruna district was selected for regional investigations, while the Tjårrojåkka prospect was selected as testing site for the local study. The Tjårrojåkka prospect is located around 50 km west of Kiruna and is constituted by an apatite-iron ore (Kiruna type) and an associated Cu(-Au) deposit. The host rock is an altered andesite of Palaeoproterozoic age. The working hypothesis to be tested was that a spatial relationship exists between IOCG deposits and major tectonic lineaments and between IOCG deposits and alteration zones and that geophysical data can be used to delineate prospective areas. Gravity and magnetic data were used to map faults and associated fracture zones at regional scale, whereas airborne radiometric data were used to map potassic alteration, which appears to be related to the Cu(-Au) mineralising event. The K/Th ratio maps at both regional and local scale seem to be able to define prospective areas for IOCG deposits. Magnetic maps are also used to indicate presence of highly magnetic bodies associated to high concentrations of Fe-minerals. In the Tjårrojåkka area, Anisotropy of Magnetic Susceptibility on oriented samples was used as tectonic indicator for the geological study of the area. Three major tectonic events were identified, one of which is interpreted to be related to the main mineralising event. Density, bulk susceptibility and Natural Remanent Magnetisation were measured for oriented samples and for borehole specimens at the main Cu deposit. Thermal demagnetisation cycles were applied to the specimens to define the main magnetic mineral, which is mostly multidomain magnetite as confirmed by Königsberger ratios lower than one. Haematite is also present and is caused by oxidation of magnetite. The haematitisation of magnetite is contemporaneous to the Cu(-Au) ore deposition and to potassic alteration. At local scale, high magnetic anomalies define magnetite bodies, while intermediate magnetic anomalies mark areas that were affected by haematitisation. These areas also show high K/Th ratios and are associated to Cu-(Au) occurences. The proposed model for IOCG exploration begins with the analysis at regional scale of potential field data to define the major tectonic lineaments and fracture zones that may have acted as pathways for mineralising fluids. The second step is to identify high/intermediate magnetic anomalies caused by magnetite/haematite deposits. High values of K/Th ratio from airborne radiometric data show areas affected by potassic alteration, which often accompanies Cu-(Au) deposition.<p>Godkänd; 2014; 20141021 (andbra); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Alessandro Sandrin Ämne: Prospekteringsgeofysik/Exploration geophysics Avhandling: Geophysical Targeting of Fe-Oxide Cu-Au Deposits in the Northern Fennoscandian Shield Opponent: Docent Satu Mertanen Head of Geophysics laboratory, Geological Survey of Finland/ Adj Professor of Geophysics, University of Helsinki, Helsingfors, Finland Ordförande: Professor Sten-Åke Elming, Avd för geovetenskap och miljöteknik, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Fredag den 21 november 2014, kl 10.00 Plats: F531, Luleå tekniska universitet</p

Semi-conventional play: definition, exploration strategy and the example of the Chalk Group in Denmark

Play analysis has been widely used in hydrocarbon exploration for decades with great success. In recent years, progress has also been made to describe reservoir properties of very low permeability reservoirs. However, comparatively little research has been conducted into play analysis for such reservoirs, which may lead to misleading estimates of their hydrocarbon potential. Here, the concept of a semi-conventional play is defined and characterised as having a reservoir of such low permeability that a hydrocarbon column can form down-dip of an effective dry trap. A new exploration approach is proposed for such plays using the Chalk Group Play in the Danish North Sea as an example. It is suggested that together with the usual risk elements, a more detailed analysis of ‘charge’ is necessary, paying particular attention to identifying possible hydrocarbon entry-points, palaeostructures and the maximum distance from these entry-points that the hydrocarbons may have reached since they first entered the reservoir. The application of this novel approach for semi-conventional plays in mature basins could help unlock further resources in proximity of existing fields, and reduce the risk of failure in frontier exploration