| 1. |
- Szilas, Kristoffer, et al.
(author)
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Remnants of arc-related Mesoarchaean oceanic crust in the Tartoq Group of SW Greenland
- 2013
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In: Gondwana Research. - : Elsevier BV. - 1342-937X. ; 23:2, s. 436-451
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Journal article (peer-reviewed)abstract
- The Tartoq Group, located in SW Greenland, consists of supracrustal rocks of mainly tholeiitic basaltic composition, including pillow lavas, sills/dykes and gabbros, as well as ultramafic rocks. Metamorphic grade ranges from greenschist fades to granulite facies. The Tartoq Group crops out as a series of blocks and slivers that are imbricated with originally intrusive Mesoarchaean TTG orthogneisses. The supracrustal rocks form part of a SE vergent fold and thrust belt consistent with the imbrication of TTG gneisses and supracrustal rocks along a convergent margin. LA-ICP-MS U-Pb zircon dating of an intrusive TTG sheet yields a minimum age of 2986 +/- 4 Ma for the Tartoq Group. This age is consistent with MC-ICP-MS Lu-Hf and Sm-Nd isotopic whole-rock data for mafic samples from different blocks of the Tartoq Group, which yield errorchron ages of 3189 +/- 65 Ma and 3068 +/- 220 Ma, respectively. The mafic supracrustal rocks of the Tartoq Group have chondrite-normalized REE patterns with La-CN/Sm-CN of 0.67-1.96 and rather flat primitive mantle-normalized multi-element patterns, except for scattered LILE contents, and generally negative Nb-anomalies with Nb/Nb* of 0.26-1.31. Th/Yb varies between 0.06 and 0.47 and Nb/Yb between 0.45 and 4.4 indicative of an arc affinity when compared to rocks from modern settings. The similar geochemistry of the different lithological units, together with their coeval formation, as evident from trace element geochemical trends, supports a co-magmatic origin for the rock assemblage and their formation as imbricated relics of oceanic crust Accordingly, we propose that the Tartoq Group represents remnants of Mesoarchaean oceanic crust, which formed in a suprasubduction zone geodynamic environment (C) 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Dziggel, A., et al.
(author)
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Thermal structure and evolution of an Archean large hot orogen : Insights from the Tasiusarsuaq terrane, SW Greenland
- 2019
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In: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 335
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Journal article (peer-reviewed)abstract
- The Tasiusarsuaq terrane represents an Archean continental upper plate that was assembled and thickened by a series of igneous and tectonic events between c. 2970 and 2700 Ma. A review of the available data combined with thermodynamic modelling and U-Pb titanite and zircon dating allows detailed insight into the processes of crustal growth during the Meso- and Neoarchean. Following the intrusion of the c. 2970–2950 Ma Fiskenæsset complex in an arc-type setting, the southern part of the Tasiusarsuaq terrane was intruded by an early TTG generation between c. 2920 and 2880 Ma to create the Bjørnesund block. Subsequently, from c. 2880 to 2830 Ma, TTG magmatism migrated to the Sermilik block in the central and northern part of the Tasiusarsuaq terrane, whereas monzogranite magmatism occurred in the south. We interpret this pattern of igneous activity to be a result of accretion of the Sermilik block to the Bjørnesund block and the formation of a new plate interface behind the accreted terrane. Fabrics related to this early accretionary stage are preserved in the prograde amphibolite facies (580–630 °C; 4–6 kbar) lithologies from the Bjørnesund block that have U-Pb titanite ages of c. 2820 Ma. Afterwards, ongoing southwards-directed subduction led to substantial thickening, manifested by high-pressure granulite facies metamorphism (870 °C, 9.0–9.2 kbar) and the intrusion of the c. 2805–2785 Ma Ilivertalik intrusive complex. Convergence and underthrusting by Eoarchean continental crust (Færingehavn terrane) at c. 2760 to 2720 Ma led to the extrusion of hot, ductile granulite nappes into the mid crust. At this time, large sections of the Tasiusarsuaq terrane underwent extensive amphibolite facies reworking, at conditions ranging from ~725 °C to 5.0–5.5 kbar in the central parts to 6.5–7 kbar and 700 °C in the north. These conditions lasted until the final collision of the terranes at 2720–2700 Ma. Collectively, our model describes the evolution of an Archean large hot orogen that is characterized by continuous convergence rather than intermittent subduction. In many respects, it resembles more recent large hot orogens such as the Grenville, including the accretion of terranes prior to collisional orogeny.
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| 4. |
- Keulen, Nynke, et al.
(author)
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Meso- and Neoarchaean geological history of the Bjornesund and Ravns Storo Supracrustal Belts, southern West Greenland: Settings for gold enrichment and corundum formation
- 2014
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In: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 254, s. 36-58
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Journal article (peer-reviewed)abstract
- To understand the Mesa- and Neoarchaean geological history of the Bjornesund region, southern West Greenland (ca. 62-63 degrees N), we have undertaken an integrated study combining field observations with U-Pb zircon geochronology by LA-ICP-MS, metamorphic petrology, and microstructural analyses. The Bjornesund region links the southern part of the Fiskenaesset anorthosite complex to the well-preserved metavolcanic rocks of the Ravn Story Supracrustal Belt and the Bjornesund Supracrustal Belt, so the development of this region is of key interest to unravelling the Archaean geology of the entire region. In this study, we couple the observed phases of gold-enrichment and corundum formation to the geological history. The leucogabbroic rocks of the Bjornesund region, which are part of the Fiskenaesset complex, intruded at ca. 2.95 Ga into the tholeiitic and calc-alkaline metavolcanic rocks of the two studied belts. Following isoclinal folding, the rocks were intruded by diorite (2.92 Ga) and granodiorite (2.91 and 2.88 Ga), which are now texturally orthogneisses. The area was affected by three major phases of folding; F1 (undated), F2 at 2.85-2.83 Ga, and F3 at 2.71-2.70 Ga. The former deformation event is associated with the gold-enrichment in alteration zones in shear folds in metavolcanic amphibolite near the contact with the orthogneiss. Intrusion of granitic sheets during the F3 deformation triggered the formation of corundum, which is locally of gem quality, at the contact between leucogabbroic and ultramafic rocks. Peak metamorphic conditions were calculated as 580-630 degrees C and 6-4 kbar at 2.85-2.83 Ga. Later retrogression in the southern part of the area at ca. 500-450 degrees C and 4.5-3 kbar, and extensional fault reactivation overprinted some of the older structures. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
- Kiviniemi, T., et al.
(author)
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A randomized prospective multicenter trial for stroke prevention by prophylactic surgical closure of the left atrial appendage in patients undergoing bioprosthetic aortic valve surgery––LAA-CLOSURE trial protocol
- 2021
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In: American Heart Journal. - : Elsevier BV. - 0002-8703 .- 1097-6744. ; 237, s. 127-134
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Journal article (peer-reviewed)abstract
- Patients undergoing surgical aortic valve replacement (SAVR) are at high risk for atrial fibrillation (AF) and stroke after surgery. There is an unmet clinical need to improve stroke prevention in this patient population. The LAA-CLOSURE trial aims to assess the efficacy and safety of prophylactic surgical closure of the left atrial appendage for stroke and cardiovascular death prevention in patients undergoing bioprosthetic SAVR. This randomized, open-label, prospective multicenter trial will enroll 1,040 patients at 13 European sites. The primary endpoint is a composite of cardiovascular mortality, stroke and systemic embolism at 5 years. Secondary endpoints include cardiovascular mortality, stroke, systemic embolism, bleed fulfilling academic research consortium (BARC) criteria, hospitalization for decompensated heart failure and health economic evaluation. Sample size is based on 30% risk reduction in time to event analysis of primary endpoint. Prespecified reports include 30-day safety analysis focusing on AF occurrence and short-term outcomes and interim analyses at 1 and 3 years for primary and secondary outcomes. Additionally, substudies will be performed on the completeness of the closure using transesophageal echocardiography/cardiac computed tomography and long-term ECG recording at one year after the operation. © 2021 The Author(s)
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| 6. |
- Landin-Olsson, M., et al.
(author)
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Islet cell and thyrogastric antibodies in 633 consecutive 15- to 34-yr-old patients in the diabetes incidence study in Sweden
- 1992
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In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 41:8, s. 1022-1027
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Journal article (peer-reviewed)abstract
- The effect of age on ICA and thyrogastric antibodies at diagnosis of IDDM was evaluated in 633 consecutively diagnosed Swedish diabetic patients aged 15-34 yr and in 282 volunteers of the same age. ICAs were present in 61% (383 of 633) of the patients and in 2% (5 of 282) of control subjects. When the initial classification was considered, ICAs were detected in 69% (327 of 473) of patients with IDDM, 23% (19 of 83) of those with NIDDM, 50% (36 of 72) of those with unclassifiable diabetes, and 20% (1 of 5) of those with secondary diabetes. The frequency of ICA fell significantly (P < 0.001) with age in IDDM patients from 77% (104/135) in those 15-19 yr old to 52% (50 of 96) in 30- to 34-yr-old IDDM patients. The low frequency of ICA in 30- to 34-yr-old IDDM patients was confined to men (42%, 28 of 66). The frequency of gastric (H+, K+-ATPase) antibodies was significantly (P < 0.05) higher in IDDM patients (10%, 47 of 449) than in patients with NIDDM (3%, 3 of 80) and unclassifiable diabetes (4%, 3 of 72). In conclusion, the frequency of ICA at the diagnosis of IDDM in young adult subjects decreases with increasing age, particularly in men. The frequent finding of ICA in patients considered to have NIDDM or unclassifiable diabetes indicates that misclassification of diabetes is frequent in young adult patients recently diagnosed with diabetes.
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| 7. |
- Szilas, Kristoffer, et al.
(author)
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Complex calc-alkaline volcanism recorded in Mesoarchaean supracrustal belts north of Frederikshab Isblink, southern West Greenland: Implications for subduction zone processes in the early Earth
- 2012
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In: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 208, s. 90-123
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Journal article (peer-reviewed)abstract
- We present new geochemical data for three Mesoarchaean supracrustal belts (Ravns Storo, Bjornesund and Perserajoorsuaq) situated north of Frederikshab Isblink in southern West Greenland for which we propose the collective name 'The Ikkattup Nunaa Supracrustal Association'. They comprise mainly amphibolites of tholeiitic basalt composition and leucoamphibolites of calc-alkaline andesite composition. Both lithological units are cut by aplite sheets of tonalite-trondhjemite-granodiorite (TTG) composition with U-Pb zircon ages of c. 2900 Ma. Lu-Hf and Sm-Nd isochrons based on whole rock amphibolite and leucoamphibolite samples yield ages of 2990 +/- 41 Ma and 3020 +/- 78 Ma, respectively, which are within error of the age of the Fiskenaesset Complex situated 5-25 km to the north. Leucoamphibolites from the three supracrustal belts show apparent geochemical mixing trends between tholeiitic amphibolites and TTG gneisses, as the end-members. By assimilation-fractional-crystallisation (AFC) modelling we can show that one group of leucoamphibolites can indeed be explained by contamination of the parental melts by a TTG-like end-member and another group of high P2O5, La and Nb leucoamphibolites can be explained by contamination involving a hypothetical low-silica adakite end-member. However, the leucoamphibolites are juvenile with epsilon Nd-(2970 Ma) from +2.1 to +3.5 and epsilon Hf-(2970 (Ma)) of +3.5 to +4.3. Thus, the mafic source of the felsic contaminant melts must have been derived from a depleted mantle source more or less at the same time (<60 Ma) as the volcanism took place. Our preferred interpretation of the geochemical and isotope data is that the protoliths of the supracrustal rocks formed in an island arc setting, where early tholeiitic volcanism gave way to calc-alkaline volcanism in a maturing arc. The apparent AFC trends are thus explained by in situ partial melting of basaltic arc crust to form juvenile TTG- and adakite-melts that mixed with mafic magmas or contaminated their mantle source to produce the calc-alkaline leucoamphibolite protolith. This model has important implications for the general interpretation of other Archaean supracrustal belts, because AFC and geochemical mixing trends towards a TTG end-member are not uniquely diagnostic of crustal contamination, but may rather reflect processes operating at lower crustal or source levels in arcs, such as melting-assimilation-storage-homogenisation (MASH) or slab-melt (low-silica adakite) metasomatism of the mantle source, respectively. (C) 2012 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
- Broome, Michael, et al.
(author)
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Prolonged extracorporeal membrane oxygenation and circulatory support as bridge to lung transplant
- 2008
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In: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 86:4, s. 1357-1360
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Journal article (peer-reviewed)abstract
- A 38-year-old man with progressive alveolitis secondary to polymyositis was treated for 52 days with venovenous and venoarterial extracorporeal membrane oxygenation as a bridge to bilateral lung transplantation. The patient survived, despite multiple complications, and is now back home with good pulmonary function. He is working part-time nearly 3 years post-transplant. This case shows that long-term extracorporeal lung assist is a viable but demanding alternative for bridging patients to pulmonary transplantation. This case also shows that right ventricular failure necessating conversion to veno-arterial assist does not necessarily predict right ventricular failure post-transplant.
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| 10. |
- Dahlman, S., et al.
(author)
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Expanding the donor pool: lung transplantation with donors 55 years and older
- 2006
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In: Transplant Proc. - 0041-1345. ; 38:8, s. 2691-3
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Journal article (peer-reviewed)abstract
- The scarcity of donor organs is one of the major limitations to lung transplantation. This has led to a progressive expansion of criteria for donor selection in lung transplantation. This study evaluated the outcome of recipients of lungs from donors >/=55 years. We performed a retrospective analysis of 212 consecutive lung transplantations. Recipients were divided into two groups, those receiving lungs from donors >/=55 years (older donor group) and those receiving lungs from donors <55 years (younger donor group). Recipient baseline characteristics, time in the intensive care unit (ICU), early mortality, and long-term survival (Kaplan-Meier) were compared between the groups. Forty-one donors (19%) were >/=55 years. Mean recipient age in the older donor group was higher than in the younger donor group (52 +/- 8 vs. 47 +/- 12 years; P = .015). Indication for transplantation did not differ between the groups. ICU stay was comparable between the two groups (6 +/- 12 vs. 7 +/- 11 days; P = .64). Actual 30-day mortality (10.8% vs. 6.4%; P = .32), 1-year mortality (17.1 vs. 19.6%; P = .50), and cumulative long-term survival (65% and 62% at 5 years, P = 1.00) did not differ between the older and younger donor group. This study indicated that transplantation of lungs from selected donors aged >/=55 years did not impair short-or long-term results. The use of lungs from elderly donors may help to increase the number of donor organs for lung transplantation.
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