Plume-lithosphere interaction in the Comei Large Igneous Province: Evidence from two types of mafic dykes in Gyangze, south Tibet, China

Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Tibet.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

Baddeleyite and zircon U-Pb ages of the ultramafic rocks in Chigu Tso area,Southeastern Tibet and their constraints on the timing of Comei Large Igneous Province

A suite of ultramafic and mafic rocks developed in the Chigu Tso area,eastern Tethyan Himalaya.Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 138.9±3.0 Ma and 139.0±1.9 Ma,respectively.These two Early Cretaceous ages are similar with the ages of the more abundant mafic rocks in the eastern Tethyan Himalaya,indicating that this suite of ultramafic and mafic rocks in the Chigu Tso area should be included in the outcrop area of the Comei Large Igneous Province(LIP).These ultramafic rocks provide significant evidence that the involvement of mantle plume/hot spot activities in the formation of the Comei LIP.Baddeleyite U-Pb dating by SIMS is one reliable and convenient method to constrain the formation time of ultramafic rocks.The dating results of baddeleyite and zircon from the olivine pyroxenite samples in this paper are consistent with each other within analytical uncertainties,suggesting that baddeleyite and zircon were both formed during the same magmatic process.The consistency of baddeleyite U-Pb ages in the Chigu Tso area with zircon U-Pb ages for a large number of Early Cretaceous mafic rocks in the eastern Tethyan Himalaya further support that zircon grains from such mafic rocks yielding Early Cretaceous ages are also magmatic in origin.

Behavior of apatite in granitic melts derived from partial melting of muscovite in metasedimentary sources

Fluid-absent and fluid-fluxed melting of muscovite in metasedimentary sources are two types of crustal anatexis to produce the Himalaya Cenozoic leucogranites.Apatite grains separated from melts derived from the two types of parting melting have different geochemical compositions.The leucogranites derived from fluid-fluxed melting have relict apatite grains and magmatic crystallized apatite grains,by contrast,there are only crystallized apatite grains in the leucogranites derived from fluid-absent melting.Moreover,apatite grains crystallized from fluid-fluxed melting of muscovite contain higher Sr,but lower Th and LREE than those from fluid-absent melting of muscovite,which could be controlled by the distribution of partitioning coefficient(D_(Ap/Melt))between apatite and leucogranite.D_(Ap/Melt) in granites derived from fluidabsent melting is higher than those from fluid-fluxed melting.So,not only SiO_(2) and A/CNK,but also types of crustal anatexis are sensitive to trace element partition coefficients for apatite.In addition,due to being not susceptible to alteration,apatite has a high potential to yield information about petrogenetic processes that are invisible at the whole-rock scale and thus is a useful tool as a petrogenetic indicator.

Nomogram for prediction of fatal outcome in patients with severe COVID-19:a multicenter study

Background:To develop an effective model of predicting fatal outcomes in the severe coronavirus disease 2019(COVID-19)patients.Methods:Between February 20,2020 and April 4,2020,consecutive confirmed 2541 COVID-19 patients from three designated hospitals were enrolled in this study.All patients received chest computed tomography(CT)and serological examinations at admission.Laboratory tests included routine blood tests,liver function,renal function,coagulation profile,C-reactive protein(CRP),procalcitonin(PCT),interleukin-6(IL-6),and arterial blood gas.The SaO2 was measured using pulse oxygen saturation in room air at resting status.Independent high-risk factors associated with death were analyzed using Cox proportional hazard model.A prognostic nomogram was constructed to predict the survival of severe COVID-19 patients.Results:There were 124 severe patients in the training cohort,and there were 71 and 76 severe patients in the two independent validation cohorts,respectively.Multivariate Cox analysis indicated that age≥70 years(HR=1.184,95%CI 1.061–1.321),panting(breathing rate≥30/min)(HR=3.300,95%CI 2.509–6.286),lymphocyte count<1.0×109/L(HR=2.283,95%CI 1.779–3.267),and interleukin-6(IL-6)>10pg/ml(HR=3.029,95%CI 1.567–7.116)were independent high-risk factors associated with fatal outcome.We developed the nomogram for identifying survival of severe COVID-19 patients in the training cohort(AUC=0.900,95%CI 0.841–0.960,sensitivity 95.5%,specificity 77.5%);in validation cohort 1(AUC=0.811,95%CI 0.763–0.961,sensitivity 77.3%,specificity 73.5%);in validation cohort 2(AUC=0.862,95%CI 0.698–0.924,sensitivity 92.9%,specificity 64.5%).The calibration curve for probability of death indicated a good consistence between prediction by the nomogram and the actual observation.The prognosis of severe COVID-19 patients with high levels of IL-6 receiving tocilizumab were better than that of those patients without tocilizumab both in the training and validation cohorts,but without difference(P=0.105 for training cohort,P=0.133 for validation cohort 1,and P=0.210 for validation cohort 2).Conclusions:This nomogram could help clinicians to identify severe patients who have high risk of death,and to develop more appropriate treatment strategies to reduce the mortality of severe patients.Tocilizumab may improve the prognosis of severe COVID-19 patients with high levels of IL-6.

Effective assignment of positional isomers in dimeric shikonin and its analogs by ^(1)H NMR spectroscopy

An approach for distinguishing two types of positional isomers of dimeric shikonin and its analogs was explored with ^(4)JC,H long-range correlation by prolonging the acquisition time at ^(2,3)JC,H values of 2.0 and 8.0Hz.Furthermore,the ^(1)H(proton)nuclear magnetic resonance(NMR)pattern of phenolic hydroxyl protons was developed as a“diagnosis signal”to ascertain the relative location of each side chain in DMSO-d_(6) at sample concentrations of 0.022-0.034 mol/L.The chemical shift differences of 0.6ppm between OH-5' and OH-1 and between OH-8'and OH-4 are assigned to Type A and Type B,respectively.All reported ambiguous structures were corrected by this pattern.Additionally,the steric structures of isolated compounds were elucidated by quantum chemical calculations of electronic circular dichroism(ECD)spectra.

One-versus two-stage partial hepatectomy for large resectable solitary hepatocellular carcinomas determined preoperatively to have a narrow resection margin:a propensity score matching analysis

Background:For patients with a large but resectable solitary hepatocellular carcinoma(HCC)of>5 cm in diameter,it is often difficult to achieve a sufficient resection margin.There is still no study on whether a two-stage hepatectomy to increase a narrow resection margin would be beneficial.Methods:From August 2014 to February 2017,patients with a large but resectable solitary HCC of>5 cm and a preoperative estimated resection margin of<1.0 cm were retrospectively studied.They were divided into one-and two-stage resection groups.A retrospective analysis was performed,followed by propensity score matching(PSM)analysis.Disease recurrence,survival,intraoperative and postoperative data were compared.Results:Before PSM,the 1-,2-,3-and 4-year recurrence-free survival rates for the one-and two-stage groups were 44.3%,31.7%,24.3%,19.2%versus 60.6%,45.4%,43.5%,32.3%,respectively(P=0.007).The corresponding OS rates were 61.0%,45.2%,43.8%,38.4%versus 69.6%,62.5%,60.7%,57.3%,respectively(P=0.029).After PSM,the 1-,2-,3-and 4-year recurrence-free survival rates for the one-and two-stage groups were 44.0%,31.5%,27.3%,21.0%versus 60.6%,45.4%,43.5%,32.3%,respectively(P=0.013).The corresponding OS rates were 62.5%,41.1%,41.1%,37.5%versus 69.6%,62.5%,60.7%,57.3%,respectively(P=0.038).Differences in the resection margins between the one-and two-stage groups before[0.3(0-0.5)versus 1.2(0.8-2.2)cm]and after[0.2(0-0.5)versus 1.2(0.8-2.2)cm]PSM were also significant.Conclusions:Two-stage hepatectomy allowed a wider resection margin for patients with a resectable but solitary HCC of>5 cm,and resulted in significantly better long-term survival outcomes after partial hepatectomy.