| 1. |
- Ahlsson, Anders, 1962-, et al.
(författare)
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A Swedish consensus on the surgical treatment of concomitant atrial fibrillation
- 2012
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Ingår i: Scandinavian Cardiovascular Journal. - London, United Kingdom : Informa Healthcare. - 1401-7431 .- 1651-2006. ; 46:4, s. 212-218
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Forskningsöversikt (refereegranskat)abstract
- Atrial fibrillation (AF) is a common arrhythmia among patients scheduled for open heart surgery and is associated with increased morbidity and mortality. According to international guidelines, symptomatic and selected asymptomatic patients should be offered concomitant surgical AF ablation in conjunction with valvular or coronary surgery. The gold standard in AF surgery is the Cox Maze III ("cut-and-sew") procedure, with surgical incisions in both atria according to a specified pattern, in order to prevent AF reentry circuits from developing. Over 90% of patients treated with the Cox Maze III procedure are free of AF after 1 year. Recent developments in ablation technology have introduced several energy sources capable of creating nonconducting atrial wall lesions. In addition, simplified lesion patterns have been suggested, but results with these techniques have been unsatisfactory. There is a clear need for standardization in AF surgery. The Swedish Arrhythmia Surgery Group, represented by surgeons from all Swedish units for cardiothoracic surgery, has therefore reached a consensus on surgical treatment of concomitant AF. This consensus emphasizes adherence to the lesion pattern in the Cox Maze III procedure and the use of biatrial lesions in nonparoxysmal AF.
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| 2. |
- Erlinge, D., et al.
(författare)
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Bivalirudin versus Heparin Monotherapy in Myocardial Infarction
- 2017
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Ingår i: New England Journal of Medicine. - : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 377:12, s. 1132-1142
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Tidskriftsartikel (refereegranskat)abstract
- Background The comparative efficacy of various anticoagulation strategies has not been clearly established in patients with acute myocardial infarction who are undergoing percutaneous coronary intervention (PCI) according to current practice, which includes the use of radial-artery access for PCI and administration of potent P2Y12 inhibitors without the planned use of glycoprotein IIb/IIIa inhibitors. Methods In this multicenter, randomized, registry-based, open-label clinical trial, we enrolled patients with either ST-segment elevation myocardial infarction (STEMI) or non-STEMI (NSTEMI) who were undergoing PCI and receiving treatment with a potent P2Y12 inhibitor (ticagrelor, prasugrel, or cangrelor) without the planned use of glycoprotein IIb/IIIa inhibitors. The patients were randomly assigned to receive bivalirudin or heparin during PCI, which was performed predominantly with the use of radial-artery access. The primary end point was a composite of death from any cause, myocardial infarction, or major bleeding during 180 days of follow-up. Results A total of 6006 patients (3005 with STEMI and 3001 with NSTEMI) were enrolled in the trial. At 180 days, a primary end-point event had occurred in 12.3% of the patients (369 of 3004) in the bivalirudin group and in 12.8% (383 of 3002) in the heparin group (hazard ratio, 0.96; 95% confidence interval [CI], 0.83 to 1.10; P=0.54). The results were consistent between patients with STEMI and those with NSTEMI and across other major subgroups. Myocardial infarction occurred in 2.0% of the patients in the bivalirudin group and in 2.4% in the heparin group (hazard ratio, 0.84; 95% CI, 0.60 to 1.19; P=0.33), major bleeding in 8.6% and 8.6%, respectively (hazard ratio, 1.00; 95% CI, 0.84 to 1.19; P=0.98), definite stent thrombosis in 0.4% and 0.7%, respectively (hazard ratio, 0.54; 95% CI, 0.27 to 1.10; P=0.09), and death in 2.9% and 2.8%, respectively (hazard ratio, 1.05; 95% CI, 0.78 to 1.41; P=0.76). Conclusions Among patients undergoing PCI for myocardial infarction, the rate of the composite of death from any cause, myocardial infarction, or major bleeding was not lower among those who received bivalirudin than among those who received heparin monotherapy. (Funded by the Swedish Heart-Lung Foundation and others; VALIDATE-SWEDEHEART ClinicalTrialsRegister.eu number, 2012-005260-10 ; ClinicalTrials.gov number, NCT02311231 .).
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| 3. |
- Lindh, Anders, et al.
(författare)
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A model for granite evolution based on non-equilibrium magma separation : evidence from the Gharib and Qattar fluorite-bearing granites, Eastern Desert, Egypt
- 2019
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Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 108:4, s. 1201-1232
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Tidskriftsartikel (refereegranskat)abstract
- We present 77 new granite whole-rock analyses from the Qattar and Gharib areas, Eastern Desert, Egypt. Both areas include a “normal” granite and either a hypersolvus (Gharib) or an almost plagioclase-free granite (Qattar) enriched in fluorite. According to earlier results, F influences element distribution in granitic melts forming complexes with specific elements as Nb, Ta, Ga, Hf, Th, Zn, Sn, whereas F excludes Ba and Sr. We use principal component analyses to split the granite into chemical groups allowing an unbiased study of the inter-group element distribution. This adds the heavy REEs and Y to the earlier lists of elements with an affinity for F. The light REEs show a decreasing affinity with decreasing atomic mass; fluorine separates Sm from Nd, whereas Zr follows La. Opposite to some, but in accordance with other earlier results, the ratio Nb/Ta is higher in the fluorite-enriched than in the other granite. Weak tetrad effects are present. Zircon in the hypersolvus granite is high in common lead. We suggest F to be instrumental for separating Pb 2+ from Pb 4+ . Two hypotheses may explain the occurrence of the two contrasting granites: they have either different sources, or they are co-magmatic, but the magma was split into two discrete types. We apply the second hypothesis as our working hypothesis. The liquidus has a gentler slope with pressure than the diapir requiring crystallisation to be most important in the lower part of the magma chamber. Our hypothesis suggests that globules of magma, enriched in volatile components, form during crystallisation due to slow diffusion rates in the crystallizing magma. Elements accompanying F are distributed into this magma batch, which has a lowered density and viscosity than the rest of the magma due to its increased contents of volatile components. A mushroom-formed diapir rises, forming the hypersolvus (or almost plagioclase-free) granite. Due to an edge effect, it is concentrated close to the wall of the magma chamber. The size and form of the outcropping granite depend on the intersection of the diapir with the erosion surface. Fluorine only makes it possible to follow the process. The model may be generalised to explain the diversification of non-F enriched granite, since the buoyancy of a magma batch several thousand m 3 in size has a much larger impact on the system than the small negative buoyancy of crystals or small crystal aggregates. A-type granite classified merely from its trace element content may form from separated F-enriched magma batches. This may be the reason for their high frequency in the Eastern Desert.
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| 4. |
- Plan, Anders, et al.
(författare)
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Exceptional preservation of reidite in the Rochechouart impact structure, France: New insights into shock deformation and phase transition of zircon
- 2021
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Ingår i: Meteoritics and Planetary Science. - : Wiley. - 1086-9379 .- 1945-5100. ; 56:10, s. 1795-1828
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Tidskriftsartikel (refereegranskat)abstract
- Reidite, the high-pressure zircon (ZrSiO4) polymorph, is a diagnostic indicator of impact events. Natural records of reidite are, however, scarce, occurring mainly as micrometer-sized lamellae, granules, and dendrites. Here, we present a unique sequence of shocked zircon grains found within a clast from the Chassenon suevitic breccia (shock stageIII) from the ~200 Ma, 20–50 km wide Rochechouart impact structure in France. Our study comprises detailed characterization with scanning electron microscopy coupled with electron backscatter diffraction with the goal of investigating the stability and response of ZrSiO4 under extreme P–T conditions. The shocked zircon grains have preserved various amounts of reidite ranging from 4% up to complete conversion. The grains contain various variants of reidite, including the common habits: lamellae and granular reidite. In addition, three novel variants have been identified: blade, wedge, and massive domains. Several of these crosscut and offset each other, revealing that reidite can form at multiple stages during an impact event. Our data provide evidence that reidite can be preserved in impactites to a much greater extent than previously documented. We have further characterized reversion products of reidite in the form of fully recrystallized granular zircon grains and minute domains of granular zircon in reidite-bearing grains that occur in close relationship to reidite. Neoblasts in these grains have a distinct crystallography that is the result of systematic inheritance of reidite. We interpret that the fully granular grains have formed from prolonged exposure of temperatures in excess of 1200 °C. Reidite-bearing grains with granular domains might signify swift quenching from temperatures close to 1200 °C. Grains subjected to these specific conditions therefore underwent partial zircon-to-reidite reversion, instead of full grain recrystallization. Based on our ZrSiO4 microstructural constraints, we decipher the grains evolution at specific P–T conditions related to different impact stages, offering further understanding of the behavior of ZrSiO4 during shock.
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| 5. |
- Albåge, Anders, et al.
(författare)
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Long-Term Follow-Up of Cardiac Rhythm in 320 Patients After the Cox-Maze III Procedure for Atrial Fibrillation
- 2016
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Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 101:4, s. 1443-1449
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Tidskriftsartikel (refereegranskat)abstract
- Background. The Cox-maze III (CM-III) procedure is the gold standard for surgical treatment of atrial fibrillation (AF). Excellent short-term results have been reported, but long-term outcomes are lesser known. The aim was to evaluate current cardiac rhythm in a nationwide cohort of CM-III patients with very long follow-up.Methods. Perioperative characteristics were retrospectively analyzed in 536 "cut-and-sew" CM-III patients operated on from 1994 to 2009 in 4 centers. Of these, 54 patients had died and 20 were unavailable at follow-up. The remaining 462 patients received a survey concerning arrhythmia symptoms, rhythm, and medication; of these, 320 patients (69%), comprising 252 men, with a mean age of 67 years (range, 47 to 87 years), and 83% with stand-alone CM-III, returned a current 12-lead electrocardiogram. Long-term monitoring was evaluated in 40 sinus rhythm patients. Postoperative stroke/transient ischemic attack was evaluated by register analysis.Results. Mean follow-up was 111 44 months (range, 36-223 months). Electrocardiogram analysis showed sinus rhythm in 219 of 320 patients (68%), and regular supraventricular rhythm (sinus, nodal, or atrial pacing) in 262 (82%), with 75% off class I/III antiarrhythmic medication. This group had lower arrhythmia symptom scores and medication use. Rhythm outcome did not differ by gender, age, type of AF, or stand-alone vs concomitant operation. Patients with more than 10 years of follow-up had a lower rate of regular supraventricular rhythm (69% vs 91%, p = 0.02). Long-term monitoring showed freedom from AF/atrial flutter in 38 of 40 patients (95%). The incidence of stroke/transient ischemic attack was 0.37% per year (11 patients).Conclusions. In a single-moment electrocardiogram evaluation 9 years after the cut-and-sew CM-III, 82% of patients were in sinus rhythm or other regular supraventricular rhythm. These findings support a long-lasting positive effect of the CM-III procedure, which is relevant when evaluating current nonpharmacologic therapies for AF. (C) 2016 by The Society of Thoracic Surgeons
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| 6. |
- Albåge, Anders, et al.
(författare)
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Long-Term Risk of Ischemic Stroke After the Cox-Maze III Procedure for Atrial Fibrillation
- 2017
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Ingår i: Annals of Thoracic Surgery. - : Elsevier BV. - 0003-4975 .- 1552-6259. ; 104:2, s. 523-529
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Tidskriftsartikel (refereegranskat)abstract
- Background The long-term risk of stroke after surgical treatment of atrial fibrillation is not well known. We performed an observational cohort study with long follow-up after the “cut-and-sew” Cox-maze III procedure (CM-III), including left atrial appendage excision. The aim was to analyze the incidence of stroke/transient ischemic attack (TIA) and the association to preoperative CHA2DS2-VASc (age in years, sex, congestive heart failure history, hypertension history, stroke/TIA, thromboembolism history, vascular disease history, diabetes mellitus) score. Methods Preoperative and perioperative data were collected in 526 CM-III patients operated in four centers 1994 to 2009, 412 men, mean age of 57.1 ± 8.3 years. The incidence of any stroke/TIA was identified through analyses of the Swedish National Patient and Cause-of-Death Registers and from review of individual patient records. The cumulative incidence of stroke/TIA and association with CHA2DS2-VASc score was estimated using methods accounting for the competing risk of death. Results Mean follow-up was 10.1 years. There were 29 patients with any stroke/TIA, including 6 with intracerebral bleedings (2 fatal) and 4 with perioperative strokes (0.76%). The remaining 13 ischemic strokes and six TIAs occurred at a mean of 7.1 ± 4.0 years postoperatively, with an incidence of 0.36% per year (19 events per 5,231 patient-years). In all CHA2DS2-VASc groups, observed ischemic stroke/TIA rate was lower than predicted. A higher risk of ischemic stroke/TIA was seen in patients with CHA2DS2-VASc score 2 or greater compared with score 0 or 1 (hazards ratio 2.15, 95% confidence interval: 0.87 to 5.32) but no difference by sex or stand-alone versus concomitant operation. No patient had ischemic stroke as cause of death. Conclusions This multicenter study showed a low incidence of perioperative and long-term postoperative ischemic stroke/TIA after CM-III. Although general risk of ischemic stroke/TIA was reduced, patients with CHA2DS2-VASc score 2 or greater had a higher risk compared with score 0 or 1. Complete left atrial appendage excision may be an important reason for the low ischemic stroke rate.
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| 7. |
- Albåge, Anders, et al.
(författare)
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The Berglin apical stitch : a simple technique to straighten things out in atrial fibrillation surgery
- 2014
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Ingår i: Interactive Cardiovascular and Thoracic Surgery. - : Oxford University Press (OUP). - 1569-9293 .- 1569-9285. ; 19:4, s. 685-686
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Tidskriftsartikel (refereegranskat)abstract
- In the Cox-Maze IV procedure, or in endocardial left atrial ablation, correct positioning of the surgical ablation probe within the left atrium might be difficult due to bulging or folds in the posterior left atrial wall. The Berglin apical stitch is a simple trick of the trade to create a smooth surface in the posterior left atrium that facilitates performing a safe transmural lesion and, consequently, may increase antiarrhythmic efficiency.
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| 8. |
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| 9. |
- Alwmark, Carl, et al.
(författare)
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An Early Ordovician 40Ar-39Ar age for the ∼50 km Carswell impact structure, Canada
- 2017
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Ingår i: Geological Society of America Bulletin. - 0016-7606. ; 129:11/12, s. 1442-1449
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Tidskriftsartikel (refereegranskat)abstract
- The formation age of the large (∼50 km) Carswell impact structure, Canada, has been a matter of debate ever since its discovery five decades ago, with proposed ages ranging from Mesoproterozoic to Early Cretaceous. Here, we present new 40Ar-39Ar data for aliquots of euhedral adularia, separated from vesicles in an impact melt rock from the central uplift of the structure. The analyses of the adularia yielded a statistically robust Early Ordovician crystallization age of 481.5 ± 0.8 Ma (2σ, mean square of weighted deviates = 1.06, P = 0.30). The most plausible explanation for the formation of vesicle-filling adularia is through low-temperature mineral precipitation during residual hydrothermal circulation that followed the impact, as no other known major intrusive, extrusive, or thermal events have occurred in the Carswell region in the Phanerozoic. The new age of the Carswell impact structure overlaps within uncertainty with the most precise Ar-Ar ages proposed for the L-chondrite parent body breakup event, but not with the age of the stratigraphic sequence from which the meteorites and micrometeorites from this event were recovered. Thus, either the Carswell impact represents a separate, unrelated impact event, or the dynamic evolution of the L-chondrite parent body breakup is more complicated than presently understood, and Carswell represents one of the earliest and largest known impacts of this event on Earth.
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| 10. |
- Bech-Hanssen, Odd, 1956, et al.
(författare)
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Pressure reflection in the pulmonary circulation in patients with severe mitral regurgitation indicates adverse postoperative outcome.
- 2013
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Ingår i: European Journal Cardio-Thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 44:6, s. 1037-1044
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Severe pulmonary hypertension (PH) is a known risk factor in valvular surgery. In the present study, we hypothesized that the assessment of pressure reflection (PR) in the pulmonary circulation, indicating increased pulmonary vascular resistance, might improve the identification of patients with increased morbidity and mortality following surgery for severe mitral regurgitation. METHODS: A total of 103 patients without atrial fibrillation were divided into three groups: Group 1 (n = 48), patients without PR; Group 2 (n = 36), patients with PR and pulmonary artery systolic pressure (PASP) ≤60 mmHg and Group 3 (n = 19), patients with PR and PASP >60 mmHg. Three variables related to PR were selected: the acceleration time in the right ventricular outflow tract (RVOT), the interval between peak velocity in the RVOT and peak tricuspid regurgitant jet velocity and the right ventricular pressure increase after peak RVOT velocity. RESULTS: There were no differences between groups in age, ejection fraction, need for coronary bypass grafting or creatinine. Patients with PR (Groups 2 and 3) had more use of vasoactive drugs (overall P < 0.0001, Group 1 vs Group 2 P = 0.018). The proportion of patients with >24 h in the intensive care unit was 27% in Group 1, 54% in Group 2 and 84% in Group 3 (overall P < 0.0001, Group 1 vs Group 2 P = 0.006). The in-hospital mortality in patients without PR (n = 49) was 0% compared with 10.9% in patients with PR (P = 0.029). CONCLUSIONS: Echocardiography assessment of PR in the pulmonary circulation and severe PH may identify patients with adverse outcome following mitral surgery.
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| 11. |
- Bjärnborg, Karolina, et al.
(författare)
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Geochronology and geochemical evidence for a magmatic arc setting for the Ni-Cu mineralised 1.79Ga Kleva gabbro-diorite intrusive complex, southeast Sweden
- 2015
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 137:2, s. 83-101
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Tidskriftsartikel (refereegranskat)abstract
- Magmatic Ni-Cu sulphide deposits are commonly associated with mafic rocks within the marginal areas of Archean or Proterozoic cratons. The Kleva Ni-Cu sulphide deposit in southeast Sweden is hosted by gabbro-diorite rocks and is sandwiched between two Palaeoproterozoic magmatic arcs: the Transscandinavian Igneous Belt (TIB) and the Oskarshamn-Jonkoping Belt (OJB). Major and trace element data corroborate an arc origin for the Kleva intrusive complex. The variety of rocks and geochemical signatures suggest that it formed from several magmatic pulses. Despite the occurrence of supracrustal xenoliths, there is a lack of trace element evidence for significant assimilation. Mafic intrusions are abundant in southeast Sweden and are generally inferred to be synchronous with the TIB. Of these, Kleva is the only known Ni-Cu deposit, and it is unclear if it is associated with the OJB or TIB. Here, we present zircon and baddeleyite U-Pb dates of 1788 +/- 4Ma, 1788 +/- 5Ma and 1792 +/- 3Ma. We interpret a 1790Ma date to be the best estimate of the crystallisation age of the Kleva intrusive complex, indicating that the emplacement of mafic magma is coeval with the voluminous arc-related TIB magmatism in the area.
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| 12. |
- Bjärnborg, Karolina, et al.
(författare)
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The age of the Kleva intrusion, southeast Sweden
- 2013
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Ingår i: Mineral deposit research for a high-tech world : Proceedings of the 12th Biennial SGA Meeting, 12-15 August 2013, Uppsala, Sweden. - 9789174032079 ; , s. 1647-1649
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Konferensbidrag (refereegranskat)abstract
- The Kleva nickel-copper mineralization is situated within a gabbro-diorite intrusion on the border between the late Svecofennian rocks of the Oskarshamn-Jonkoping belt and rocks of the slightly younger Transscandinavian Igneous Belt (TIB). The sulphides present in the mafic intrusion are pyrrhotite, chalcopyrite, pentlandite and pyrite, occurring as massive mineralization, disseminations and thin, predominantly chalcopyrite-bearing veins. Age determinations of the gabbro-diorite were conducted to determine the age of the mineralization and its regional context. U-Pb analyses of baddeleyite (TIMS) and zircon (SIMS) from the gabbro-diorite and related rocks indicate an age of c. 1.79 Ga for the Kleva intrusion, broadly coeval with the TIB-rocks in the area, but younger than the late Svecofennian rocks. Further studies will help to constrain whether the sulphide mineralization was modified during later alteration, regional tectonism and metamorphism.
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| 13. |
- Braathen, Bjørn, et al.
(författare)
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One single dose of histidine-tryptophan-ketoglutarate solution gives equally good myocardial protection in elective mitral valve surgery as repetitive cold blood cardioplegia: A prospective randomized study.
- 2011
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Ingår i: The Journal of thoracic and cardiovascular surgery. - : Elsevier BV. - 1097-685X .- 0022-5223. ; 141:4, s. 995-1001
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Histidine-tryptophan-ketoglutarate (HTK-Custodiol) cardioplegic solution is administered as one single dose for more than 2 hours of ischemia. No prospective randomized clinical study has compared the effects of HTK and cold blood cardioplegia on myocardial damage in elective mitral valve surgery. Thus, the main aim of the present study was to examine whether one single dose of cold antegrade HTK gives as good myocardial protection as repetitive antegrade cold blood cardioplegia in mitral valve surgery. METHODS: Eighty consecutive patients undergoing elective isolated mitral valve surgery for mitral regurgitation, with or without ablation for atrial fibrillation, were included in the study and randomized to HTK or blood cardioplegia. Markers of myocardial injury (troponin-T and creatine kinase MB) were analyzed at baseline and 7 hours, 1 day, 2 days, and 3 days after surgery. RESULTS: No significant difference in creatine kinase MB and troponin-T between HTK and blood cardioplegia groups was found at any time point. There was a significant correlation between ischemic time and markers of myocardial injury in the HTK group only and significantly more spontaneous ventricular fibrillation after release of crossclamping in the HTK group. CONCLUSIONS: One single dose of antegrade cold HTK cardioplegic solution in elective mitral valve surgery protects the myocardium equally good as repetitive antegrade cold blood cardioplegia.
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| 14. |
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| 15. |
- Calner, Mikael, et al.
(författare)
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Vandring runt Hunnebo klåvor
- 2017
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Ingår i: Geologiskt Forum. - 1104-4721. ; 95, s. 22-24
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 16. |
- Caton, Summer A., et al.
(författare)
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Evolution of the sources of TTG and associated rocks during the Archean from in-situ 87Sr/86Sr isotope analysis of apatite by LA-MC-ICPMS
- 2022
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937 .- 1872-6143. ; 428-429
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Tidskriftsartikel (refereegranskat)abstract
- Radiogenic isotopes provide an important means towards elucidating Archean crustal evolution. The global Hf and Nd isotope record of Archean crustal fragments has been instrumental to unveiling the history of ancient crustal growth and differentiation. The Rb-Sr system could provide valuable complementary constraints in this regard, as this system is particularly sensitive to magmatic fractionation processes, and the chemical and isotopic evolution of magma sources. Application of this system has so far been complicated, however, by its susceptibility to isotope re-equilibration or alteration of the Rb/Sr parent-daughter ratio. In-situ Sr isotope analysis of primary igneous minerals with very low Rb/Sr, such as apatite, provides a new means to determine the initial 87Sr/86Sr (87Sr/86Sri) values for igneous rocks directly. In this study, we apply in-situ Sr isotope analysis of apatite by LA-MC-ICPMS to tonalite-trondhjemite-granodiorite (TTG) rocks and end-member sanukitoids from Archean cratons worldwide. The 87Sr/86Sri values of sanukitoids are relatively radiogenic, supporting the model in which such rocks are formed by flux melting of a mantle strongly enriched by metasomatism, possibly by slab-derived fluids. The 87Sr/86Sri values for TTGs formed between 3.72 and 3.45 Ga are generally radiogenic, indicating aged amphibolite sources. The 87Sr/86Sri values of younger TTGs are systematically lower and were derived from mafic sources that had an average age of ≤0.2 Gyr. This evolution matches with observations from Hf isotopes for TTGs of similar age and indicates a systematic change in the nature or efficiency of TTG crust formation during the Paleoarchean. In-situ Sr isotope analysis of apatite provides a useful method to uncover the Sr record of the early continental crust, and enables constraints on local source evolution and the general two-step evolutionary process of Archean crust formation.
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| 17. |
- Cornell, David H., 1948, et al.
(författare)
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A new chronostratigraphic paradigm for the age and tectonic history of the Mesoproterozoic Bushmanland Ore District.
- 2009
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Ingår i: Economic Geology. ; 104, s. 385-404
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Tidskriftsartikel (refereegranskat)abstract
- The four giant stratiform Cu-Pb-Zn-Ag base metal deposits of the Bushmanland Ore District have long been regarded as Paleoproterozoic sedimentary-exhalative deposits formed in a continental basin at about 1650 Ma and overlying the Achab Gneiss, an approximately 2.0 Ga basement complex, with no known Archean crustal history. The supracrustal sequence was thought to include the Hoogoor 'pink' metavolcanic gneiss at the base and the ore-bearing metaquartzites to be unconformably overlain by the 1650 Ma Koeris Formation. All the supracrustals were regarded as predating the 1200 to 1000 Ma Namaqua-Natal orogenic cycle. In this work we present ion probe and laser ablation zircon dating of xenocrystic, magmatic, detrital and metamorphic zircon which leads to fundamental changes in our understanding of the age and tectonic history of the Bushmanland Ore District. The Bushmanland base metal deposits are not older than 1650 Ma as entrenched in the literature, but younger than the 1285 ± 14 Ma detrital zircons found within the ore horizon at Gamsberg. The ore is probably older than the 1198 ±10 and 1154 ± 18 Ma detrital zircons found in the unconformably overlying Koeris Formation, and most likely older than the 1130 ± 35 Ma Koeris Formation metabasalts. The existence of an Archean crustal component in the Bushmanland Ore District has now been established by detrital zircon ages and by Sm-Nd model ages. However no outcrops of Archean rocks have yet been found. The Bushmanland Group metasediments were derived largely from 1850 to 2100 Ma Paleoproterozoic rocks, which probably reflects their provenance in the Richtersveld Subprovince to the north. However they also contain Mesoproterozoic detrital zircon which constrains their minimum age. The Bushmanland Ore District metasediments conform to the same chronostratigraphic and tectonostratigraphic pattern as recently established at Bitterfontein to the southwest. An older group represented by the Bushmanland Group and including the sedimentary-exhalative Cu-Pb-Zn-Ag ores, formed before, but within 80 Ma of, the main collision event at 1200 Ma. A younger group, represented by the Koeris Formation, formed after the main collision at about 1130 Ma. The older group should thus have experienced an early collision-related D1 folding event and metamorphism, whereas the younger group should show only D2-D3 and M2-M3 metamorphism, between 1130 and 1000 Ma. This prediction should be tested against more structural observations. The 1204 ± 11 Ma Aroams Gneiss is now recognised as the oldest known granitoid in the Bushmanland Ore District, in agreement with other recently published ion probe data. However it probably does not represent basement to the older metasediments. The Achab Gneiss, previously thought to be about 2000 Ma old and the polydeformed basement, is dated by our published 1166 ± 13 and 1163 ± 11 Ma concordia ages for magmatic emplacement. The Aroams Gneiss is confirmed to belong to the 1200 Ma syn-collisional Little Namaqualand Suite documented in the Okiep Copper District to the west. The 30 Ma younger Achab and Hoogoor Gneisses may be grouped in the Aggeneys Suite. Microbeam zircon dating has established a new chronostratigraphic paradigm for the geological history of the Bushmanland Ore District, however many issues related to ore formation and the deformation history remain to be resolved.
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| 18. |
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| 19. |
- Cornell, David H., 1948, et al.
(författare)
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Evidence from Dwyka tillite cobbles of Archean basement beneath the Kalahari sands of southern Africa
- 2011
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Ingår i: Lithos. - 0024-4937. ; 125, s. 482-502
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Tidskriftsartikel (refereegranskat)abstract
- We have found a new source of information about what lies beneath the Kalahari sands. The Kheis and Rehoboth Provinces of southern Africa were thought to be underlain by either an ~1800 Ma orogenic belt, or a northern branch of the ~1200 Ma Namaqua–Natal Province. Glacial diamictites of the Permocarboniferous Dwyka Group exposed at Rietfontein west of the Kalahari sands carry cobbles plucked from the bedrock by the ice sheet which covered the Gondwana supercontinent about 300 Ma ago. Despite altered mineralogy, the cobbles are not severely altered geochemically. Their normative mineral compositions give classifications as trondhjemites and granites, supported by rare earth element diagrams. Microbeam U–Pb zircon dating of the granitic cobbles shows that they contain no evidence of crustal growth or orogeny at either 1800 or 1200 Ma. Rather they testify to the presence of 2500 to 2900 Ma Archaean trondhjemitic and granitic crust beneath the Kalahari, with a lesser ~2050 Ma granite component. The pebble assemblages from the diamictites we sampled lack the diagnostic banded iron formation (BIF), stromatolitic limestone and other supracrustal pebbles which characterise diamictites derived from the Kaapvaal Craton, thus we envisage shorter transport distances and derivation from the region now beneath the Kalahari sands. Three of the Archaean granite cobbles have unusual less-than-mantle zircon oxygen isotope values around +3 (δ18O VSMOW), which may reflect interaction of their source with high-temperature, originally meteoric water before melting to produce the granites. The mafic cobbles described in a companion paper are much younger and are related to intrusions of the 1.1 Ga Umkondo Large Igneous Province, probably located on the Kalahari Line or Rehoboth Province. Five trondhjemitic granites from the westernmost outcrops of the Kaapvaal Craton were dated, the oldest being 3061±9 Ma and four others between 2882±7 Ma and 2854±7 Ma, reflecting the cratonisation of the Kimberley Terrane. Four of the Archaean Dwyka cobbles we dated are younger than the 2.7 Ga Kaapvaal cover sequence and are thus too young to be derived from the craton. All the Dwyka cobbles described here are most likely derived from either the Rehoboth Province or the Kalahari Line with origins from the Kheis Province, Kaapvaal Craton, or further afield considered unlikely. We envisage the Rehoboth Province to consist of an Archaean core supplemented by Palaeoproterozoic granitoids, which was joined to the Kaapvaal Craton at an early stage of crustal development and played an important role during later tectonic events. This has important implications not only for the tectonic framework and assembly of Southern Africa, but also for exploration for diamonds and other ore deposits.
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| 20. |
- Cornell, David H., 1948, et al.
(författare)
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Reply to comments by Mc Clung, C.R., Gutzmer, J., Beukes, N.J, on: A new chronostratigraphic paradigm for the age and tectonic history of the Mesoproterozoic Bushmanland Ore District.
- 2009
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Ingår i: Economic Geology. - 0361-0128. ; 104, s. 1282-1285
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Tidskriftsartikel (refereegranskat)abstract
- We were pleased and encouraged by the congratulations expressed in the first paragraph of our friend McClung et al.’s (2009) comment. However, as we read further, we found that not all was rosy. We were dismayed to discover that we had made a lot of mistakes and in the end, all we had achieved was to add to the confusion about the origin of the Bushmanland ore district!
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| 21. |
- Cornell, David H., 1948, et al.
(författare)
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Zircon dating reveals an Archaean crust beneath the Kalahari sand.
- 2008
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Ingår i: Annual Meeting Mineralogical Network, Natural History Museum, University of Oslo, June 2008. ; abstracts
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Continents are subdivided into structural provinces based on the age of the last orogeny or major magmatic event which imprinted the structural fabric on the bedrock. These first-order subdivisions are important in understanding how the continents were assembled. The continuity and boundaries of provinces such as the Namaqua-Natal Province in Southern Africa have been established, however adjoining Kheis province which lies almost entirely under the Tertiary to Recent Kalahari sands, has thus far defied attempts to understand its age and geological history. A foreland thrust complex developed in 1.92 Ga redbeds at Olifantshoek (Fig. 1a) was postulated by Cornell et al. 1998. However the much younger 1.2 Ga to 1.1 Ga Sinclair Sequence volcanic and plutonic rocks exposed in the same area suggest that the Kheis Province could have experienced an Andean-type orogeny at ~1.2 Ga. Thus Moen (1999) suggested that much of the Kheis Province was coeval with and belonged to the ~1.2 Ga Namaqua-Natal Province. At Rietfontein on the eastern margin of the Kheis, tillites of the Permian Dwyka Group, were found to contain abundant cobble-sized clasts of crystalline bedrock. Bearing in mind the generally westward transport directions for the Dwyka Ice sheet (Fig. 1a), these exposures were investigated to see if they contained information about what lies under the Kalahari. These granotoid cobbles are badly weathered, but we succeeded in dating them using an ion probe and laser ablation ICPMS, by the U-Pb method. The data is largely discordant, reflecting ancient lead loss at the time of glaciation. Nevertheless we find compelling evidence that Archean and 2.0 Ga (Bushveld Complex age) granitic crust exists beneath the Kalahari. We also failed to find any evidence for the existence of younger granitic crust or high-grade metamorphic terranes. The published concepts of the Kheis Province as either a 1900 - 1750 Ma collisional orogen, or an extension of the 1200 Ma Namaqua Province find no support in our data. The possibility of Archean and Bushveld-aged rocks occuring as basement beneath the Kalahari has important implications for diamond, base and precious metal prospecting in the western Kalahari in South Africa, Botswana and Namibia. These possibilities should be tested by drilling with geophysical control, the last such campaign having been completed in Botswana in 1984.
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| 22. |
- Dahlman, S., et al.
(författare)
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Expanding the donor pool: lung transplantation with donors 55 years and older
- 2006
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Ingår i: Transplant Proc. - 0041-1345. ; 38:8, s. 2691-3
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Tidskriftsartikel (refereegranskat)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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| 23. |
- Dyhr, Charlotte T., et al.
(författare)
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Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla and new Ar-40/Ar-39 dating from the Mendoza Region, Argentina
- 2013
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937. ; 179, s. 67-83
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Tidskriftsartikel (refereegranskat)abstract
- Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquen has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new Ar-40/Ar-39 age results of major and trace elements as well as Nd, Sr and Pb isotopic data. Four million years of eruptions from 24.4 +/- 0.3 Ma (2 sigma) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (similar to 36.50 degrees S) provide evidence for the presence of back-arc mantle devoid of subduction-related components. In contrast, the lower Huantraico lavas (similar to 37.30 degrees S) require an atypical back-arc mantle, almost devoid of arc-like components (e.g. low La/Ta = 15-18 and Ba/La = 12-18), but with a more depleted isotopic signature (e.g. Sr-87/Sr-86, 0.7033-0.7037) than observed elsewhere in the Andean back-arc. The Lower to Upper Series development in the Huantraico sequence represents a gradual change from basaltic to trachyandesitic back-arc lavas with a weak but temporally increasing arc geochemical signature (e.g. La/Ta = 15-21; Ba/La = 12-45), which is accompanied by Sr, Nd and Pb isotopic compositions approaching present day values of the Andes arc. The compositional change is accompanied by a gradually decreasing role for garnet in the mantle source, a decreasing degree of melting, but also simultaneously increasing influence from subducted fluids, probably as the slab geometry changes through time. The volcanism at Huantraico ceased when a flat slab was established around 15 Ma. (C) 2013 Elsevier B.V. All fights reserved.
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| 24. |
- Erlinge, David, et al.
(författare)
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Bivalirudin versus heparin monotherapy in non-ST-segment elevation myocardial infarction
- 2019
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Ingår i: European Heart Journal. - : Sage Publications. - 2048-8726 .- 2048-8734. ; 8:6, s. 492-501
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The optimal anti-coagulation strategy for patients with non-ST-elevation myocardial infarction treated with percutaneous coronary intervention is unclear in contemporary clinical practice of radial access and potent P2Y12-inhibitors. The aim of this study was to investigate whether bivalirudin was superior to heparin monotherapy in patients with non-ST-elevation myocardial infarction without routine glycoprotein IIb/IIIa inhibitor use.METHODS: In a large pre-specified subgroup of the multicentre, prospective, randomised, registry-based, open-label clinical VALIDATE-SWEDEHEART trial we randomised patients with non-ST-elevation myocardial infarction undergoing percutaneous coronary intervention, treated with ticagrelor or prasugrel, to bivalirudin or heparin monotherapy with no planned use of glycoprotein IIb/IIIa inhibitors during percutaneous coronary intervention. The primary endpoint was the rate of a composite of all-cause death, myocardial infarction or major bleeding within 180 days.RESULTS: A total of 3001 patients with non-ST-elevation myocardial infarction, were enrolled. The primary endpoint occurred in 12.1% (182 of 1503) and 12.5% (187 of 1498) of patients in the bivalirudin and heparin groups, respectively (hazard ratio of bivalirudin compared to heparin treatment 0.96, 95% confidence interval 0.78-1.18, p=0.69). The results were consistent in all major subgroups. All-cause death occurred in 2.0% versus 1.7% (hazard ratio 1.15, 0.68-1.94, p=0.61), myocardial infarction in 2.3% versus 2.5% (hazard ratio 0.91, 0.58-1.45, p=0.70), major bleeding in 8.9% versus 9.1% (hazard ratio 0.97, 0.77-1.24, p=0.82) and definite stent thrombosis in 0.3% versus 0.2% (hazard ratio 1.33, 0.30-5.93, p=0.82).CONCLUSION: Bivalirudin as compared to heparin during percutaneous coronary intervention for non-ST-elevation myocardial infarction did not reduce the composite of all-cause death, myocardial infarction or major bleeding in non-ST-elevation myocardial infarction patients receiving current recommended treatments with modern P2Y12-inhibitors and predominantly radial access.
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| 25. |
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