1,932 research outputs found

    Into the High to Ultrahigh Temperature Melting of Earth's Crust: Investigation of Melt and Fluid Inclusions within Mg-Rich Metapelitic Granulites from the Mather Peninsula, East Antarctica

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    Precise constraints on the compositions of melts generated by anatexis under ultrahigh temperature (UHT) conditions are critical for understanding processes of partial melting and differentiation of the Earth's crust. Here we reveal geochemical and physical signatures of anatectic melts preserved as nanogranitoids (i.e. crystalized melt inclusions) within sapphirine-bearing UHT metapelitic granulites from the Mather Peninsula, East Antarctica. Their coexistence with high-Al orthopyroxene as inclusions in garnets strongly suggests that the investigated melts were at least partially UHT in origin. The nanogranitoids are enriched in SiO2 (69.9-75.6 wt.%), strongly peraluminous (ASI values = 1.2-1.6) and potassic to ultrapotassic (Na2O + K2O = 7.1-9.5 wt.%, K/Na = 2.2-9.3). When compared to the granulitic restite, the melts are enriched in Li, Cs, Rb, Ta, Sm, Nd, Zr, U and Pb, and depleted in Ce, Th, Ba, Sr and Nb. Their geochemical characteristics are consistent with biotite-dehydration melting in the absence of plagioclase. Our calculation results indicate that these hot crustal melts have low densities of 2.47 ± 0.07 g/cm3, low viscosities of 104.9 ± 1.2 Pa·s and high heat production values of ∌2.8 ÎŒW/m3. Therefore, such melts are mobile and susceptible to be extracted from the source, and consequently their flow and removal from the deep crust may greatly affect the chemical and thermal structure of the continental crust. Secondary C - O - H fluid inclusions within garnet and orthopyroxene have also been detected. These inclusions contain magnesite, pyrophyllite, corundum, with or without residual CO2. The minerals within the fluid inclusions are interpreted as stepdaughter minerals, which were produced by the reaction of the fluid with its host. The metamorphic timing of the investigated rocks is still a matter of debate. Zircon U-Pb dating results obtained in this study suggest that the metapelitic granulites may have undergone two separated thermal events at ∌1000 and ∌530 Ma, respectively. The presence of fluid inclusions indicates that fluid infiltration and Pan-African reworking may have played an important role in obscuring chronological information of the early thermal scenario in poly-metamorphic terranes

    Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

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    BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old

    Long-term neurological symptoms after acute COVID-19 illness requiring hospitalization in adult patients: insights from the ISARIC-COVID-19 follow-up study

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    in this study we aimed to characterize the type and prevalence of neurological symptoms related to neurological long-COVID-19 from a large international multicenter cohort of adults after discharge from hospital for acute COVID-19

    C–O–H fluid-melt-rock interaction in graphitic granulites and problems of quantifying carbon budget in the lower continental crust

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    Estimates on the geological carbon cycle are subject to large uncertainties that can be reduced by thorough observation of rocks. In this contribution, we focus specifically on C-O-H fluid-melt-rock interactions in graphitic metapelitic granulites and on their bearing to the carbon budget of granulitic roots of continents. We provide robust microstructural and thermometric constraints on the coexistence of anatectic silicate melts and C-O-H fluids up to near ultrahigh temperature conditions in the archetypal crustal section of Ivrea-Verbano Zone (IVZ, Italian Alps). Fluid inclusions in garnet are investigated before and after high-temperature experiments, and contain considerable proportions of CO2, CH4, N2, but lower H2O than predicted for graphitic systems at granulite facies. When comparing and contrasting the melt compositions obtained by Perple_X and rhyoliteMELTS with natural melts from IVZ, a much better match is obtained by the former, questioning the choice of rhyolite-MELTS for modelling melting equilibria of metasedimentary rocks and for quantifying carbon budget of the lower crust. Overall, data show that assuming only a limited extent of fluid-melt immiscibility in the deep crust contradicts the evidence from natural rocks and prompts to an incomplete view of actual carbon behavior and carbonic fluids. The available experimental dataset on CO2 solubility in felsic melts cannot be used to interpret the volatile budget of melt inclusions in graphitic migmatites and granulites, as most solubility experiments were conducted under carbonate-saturated (i.e. highly oxidizing) conditions which maximize CO2 content of melt, compared to graphitic (i.e. more reducing) protoliths. As a consequence, thermodynamic models still cannot account for all the complexities related with interactions among H2O-CO2-CH4 ternary fluids, H2Oand CO2-bearing anatectic melts and graphite-bearing residues in graphitic metapelites. Targeted experimental studies are therefore crucial to boost substantial computational efforts, before any precise estimates on carbon budget and fluxes in the lower anatectic crust can be made

    Association of Country Income Level With the Characteristics and Outcomes of Critically Ill Patients Hospitalized With Acute Kidney Injury and COVID-19

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    Introduction: Acute kidney injury (AKI) has been identified as one of the most common and significant problems in hospitalized patients with COVID-19. However, studies examining the relationship between COVID-19 and AKI in low- and low-middle income countries (LLMIC) are lacking. Given that AKI is known to carry a higher mortality rate in these countries, it is important to understand differences in this population. Methods: This prospective, observational study examines the AKI incidence and characteristics of 32,210 patients with COVID-19 from 49 countries across all income levels who were admitted to an intensive care unit during their hospital stay. Results: Among patients with COVID-19 admitted to the intensive care unit, AKI incidence was highest in patients in LLMIC, followed by patients in upper-middle income countries (UMIC) and high-income countries (HIC) (53%, 38%, and 30%, respectively), whereas dialysis rates were lowest among patients with AKI from LLMIC and highest among those from HIC (27% vs. 45%). Patients with AKI in LLMIC had the largest proportion of community-acquired AKI (CA-AKI) and highest rate of in-hospital death (79% vs. 54% in HIC and 66% in UMIC). The association between AKI, being from LLMIC and in-hospital death persisted even after adjusting for disease severity. Conclusions: AKI is a particularly devastating complication of COVID-19 among patients from poorer nations where the gaps in accessibility and quality of healthcare delivery have a major impact on patient outcomes

    Revealing the link between A-type granites and hottest melts from residual metasedimentary crust

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    Among S-, I-, and A-type granites, the latter are the most debated in terms of origin, and metasedimentary crust is usually discarded as a potential source. Here we tackle this issue by adopting an in-source perspective, rather than focusing on the final product (granite), documenting the occurrence of pristine melt inclusions (MIs) in garnet from residual metapelitic ultrahigh-temperature (UHT) granulite from East Antarctica. Coexistence of sapphirine + quartz, phase equilibria calculations, and Zr-in-rutile thermometry indicate that MIs trapped UHT melts formed at peak conditions (930–1000 °C) from a residual metapelitic source. MIs are granitic with weakly peraluminous to weakly peralkaline affinity, ferroan character, high alkali contents, high K/Na and Ga/Al, and low Ca, Ba, Sr, and H2O concentrations. These features and geochemical modeling indicate that MIs represent primary melts for high-SiO2 A-type granites. Therefore, MIs reveal the missing link between A-type granites and the hottest metasedimentary crust. Voluminous amounts of slightly peraluminous, high-SiO2 A-type granites can be produced in large, residual UHT terranes such as those of eastern Gondwana. Our results provide a wider view of processes responsible for granite formation and show that a larger variety of granites must be considered in models of the effects of UHT anatexis on crustal differentiation

    Thrombotic and hemorrhagic complications of COVID-19 in adults hospitalized in high-income countries compared with those in adults hospitalized in low- and middle-income countries in an international registry