The longevity of subcontinental lithospheric mantle beneath Jiangsu-Anhui Region——The Os isotope model age of mantle-derived peridotite xenoliths

The basalt-borne peridotite xenoliths from Jiangsu-Anhui provinces were analyzed for whole rock Os isotopic compositions in two laboratories of USTC, China and CRPG, France, respectively. The ^(187)Os/^(188)Os ratio of the sample set ranges from 0.119 to 0.129 (25 samples, USTC) and from 0.117 to 0.131 (17 samples, CRPG). The Os isotopic compositions of most samples are less than 0.129 and depleted relatively to the primitive mantle, showing a good correlation with the major element compositions. With the ^(187)Os/^(188)Os-AI2O3 alumichron, the samples yield a model age of 2.5±0.1 Ga (data of USTC) and 1.9±0.1 Ga (data of CRPG), late Archean to early Pro-terozoic. The two samples with the lowest ^(187)Os/^(188)Os ratio (0.119 and 0.117) have the T_(RD) (Re depleted age) of 1.1 Ga (USTC) and 1.4 Ga (CRPG), mid-Proterozoic. The Os isotope model age shows that the peridotite xenoliths from Cenozoic alkali basalt in Jiangsu-Anhui provinces have an old formation age (early- to mid- Proterozoic). They are not newly produced mantle after the Phanerozoic replacement of the lithosphere mantle, but residual fractions of Proterozoic mantle.

Geological Characteristics and Model Ages of Marius Hills on the Moon

Marius Hills is a volcanic plateau on the nearside of the Moon. It is of great interest for its high concentration of volcanic features, including domes, cones, ridges, and rilles. However, the morphological and chronological characteristics of this plateau were not well studied due to the low resolution of early mission data. This study describes the detailed morphology of the volcanic features using the latest high spatial resolution images of the Terrain Camera （TC） onboard Selene-1 （10 m/pix） and Narrow Angle Camera （NAC） onboard the Lunar Reconnaissance Orbiter （LRO） （0.5 m/pix）. We report here some new structures such as skylights and remnants of lava tubes. We have divided spectrally homogenous areas with Clementine UVVIS data and did crater size frequency distribution （CSFD） measurements with Lunar Orbiter （LO） IV and TC images in every spectral unit. We first report absolute model ages of 1.10 Ga for Marius basalt 1, 1.49 Ga for Fiamsteed basalt, and 1.46 Ga for Schiaparelli Basalt. In addition, we have identified several younger lava events： they are Marius basalt 2 （814 Ma）, medium to low titanium basalt （949 Ma）, and undifferentiated medium titanium basalt （687 Ma）. Finally, we propose a mantle plume scenario for the formation of Marius Hills, which could solve the inconsistency of previous models.

Luminescence chronology and age model application for the upper part of the Chumbur-Kosa loess sequence in the Sea of Azov, Russia

A reliable chronology is essentially critical for correlating loess records with other paleoenvironmental time series, as well as for continuing improvements in the reconstruction of paleoenvironment and paleoclimate changes. It is exactly that the scarcity of chronologies across the Sea of Azov has limited the interpretation of climatic and environmental information in the East European Plain. In view of this, this paper conducted an exploratory study to investigate whether the optically stimulated luminescence(OSL) dating of medium-grained quartz could be used to obtain a set of chronologies and the age models could be used to establish an independent time scale since the Late Pleistocene for the Sea of Azov loess. The results showed that an internally consistent set of optical ages for the Azov loess deposited up to ~76 ka. In addition, the ages developed based on magnetic susceptibility and grain size ages models showed good comparability with independent OSL ages at an acceptable range, suggesting that it might be practicable to establish an independent time scale using age models at the Sea of Azov loess, at least for the uppermost part of the Chumbur-Kosa section. Comparison with the ages based on two age models,the grain size ages using fine-grain fractions may provide a more reliable chronological sequence at the Azov loess since the Late Pleistocene. With the help of absolute ages and climate proxies(magnetic susceptibility and grain size), paleoclimatic change in the Sea of Azov have been traced for the Late Pleistocene.

Grain-size Age Model in Reconstructing Orbital-and Suborbital-scale Climate Changes on the Northeastern Tibetan Plateau Since the Late Glacial

Reconstructions of past climatic changes on the northeastern Tibetan Plateau(NETP) can provide insights into the Asian summer monsoon(ASM) variability. However, the regional climate changes on both orbital and suborbital time scales since the late Glacial remain controversial. Here we present the results of high-resolution geochemical and grain-size analyses of a sediment core from Genggahai Lake, a small, shallow lake in this area. Changes of the accumulation rate of the core sediments show a similar trend with variations of the coarse fraction. Accordingly, the chronological framework is constructed using a grain-size age model. In addition, the histories of chemical weathering and aeolian activity since the late Glacial are reconstructed based on the Al/Ti ratios and coarse fractions, respectively. The results suggest that an enhanced chemical weathering and a weakened aeolian activity occurred on the NETP under a warmer, wetter climate during the early to mid-Holocene(11.3–6.3 ka cal BP), compared with the late Glacial(17.1–11.3 ka cal BP) and the late Holocene(6.3 ka cal BP to present), which responded mainly to the strengthened ASM on orbital time scale. In addition, the synchronous occurrences of weakened chemical weathering, low lake level and intense aeolian activity on suborbital time scale reflect several episodes of weakened ASM. Furthermore, these episodes largely coincide with the centennial-to millennial-scale cold events in the North Atlantic, which demonstrates the close connection between the ASM and the cooling at high latitudes.

Nd-Pb Isotopes of Basement Rocks,Granitoids and Basalts from the Western Margin of the Yangtze Craton:Implications for Crustal Evolution

Neodymium (Nd) depleted mantle model ages indicate that the Kangding complexes in the northern segment of the western Yangtze craton, argued as representative of the craton's basement, actually formed after 1.6 Ga. An Sm-Nd isochron of 706 Ma constrains the upper limit formation of the complex from Shaba, Sichuan Province. Lead (Pb) isotopic compositions imply that the southern and northern basements of the western Yangtze craton can not be correlated. The southern basement is characterized by higher ~206Pb/~204Pb ratios (≥17.69) than the northern ones (<17.69). However, Hercynian granitoids, gabbros as well as the Permian basalts in the northern segment show no difference from the southern segment in Pb isotopic compositions. This suggests that the southern and northern segments were controlled by one common mantle domain during the Late Paleozoic. Based on Nd model ages of sediments and metasediments, as well as the ages of their relict zircons, we infer that the Yangtze craton is mainly composed of 2.0 Ga crustal components. The Kangding complex represents the accretion products to the Yangtze craton in Neoproterozoic.

An updated constraint on the local stratigraphy at the Chang'E-4 landing site

The Chang’E-4 mission has been exploring the lunar farside.Two scientific targets of the rover onboard are(1)resolving the possible mineralogy related to the South Pole-Aitken basin and(2)understanding the subsurface processes at the lunar farside.Publications to date that are based on the reflectance spectra and radar data obtained by the rover have shown a persistent inconsistency about the local stratigraphy.To explain both the abnormal surface topography at the landing site and the unexpected radargram observed by the rover,the Alder crater has been frequently reported to be older than the mare basalts at that landing site.However,this argument is not supported by earlier geological mapping nor recent crater statistics.Resolving this controversy is critical for a full understanding of the geological history of the landing area and for correct interpretations of the scientific data returned.Employing detailed crater statistics,rigorous statistical analyses,and an updated crater chronology function,this study is determined to resolve the relative ages of the Alder crater,Finsen crater,and the mare basalts on the floor of Von Kármán.Our results reveal that while background secondaries and local resurfacing have widely occurred in the study area,affecting age determinations,the statistics are significant enough to conclude that the Alder crater is the oldest among the three targets.This independent constraint is consistent with both the crosscutting relationships of different terrains in this area and global stratigraphic mapping.Our results exclude Alder as a possible contributor of the post-mare deposits at the landing site,appealing for a more systematic stratigraphy study to resolve the provenances of these deposits.

Source and Significance of Detrital Zircons from Mesozoic Sandstones of the Upper Yangtze Block, China

In this study, we report U–Pb and Lu–Hf isotopic data for zircons from the Mesozoic sandstones of the Upper Yangtze area, which provide critical constraints on the provenance of these sediments and further shed light on the crustal evolution of the Upper Yangtze block. The results of isotopic chronology indicate the following：（1） The provenances of the study area are very complex, and the tectonic evolution process is relatively closed.（2） The provenances are mainly Archean–Proterozoic crystalline basement or recycled material; Paleoproterozoic crustal accretion in the western margin of the Yangtze block and Neoproterozoic magmatic activities related to subduction of the western margin of the Yangtze block; early Cambrian oceanic magmatic activity, which resulted from the intraplate extension of the northern margin of the Yangtze block; late Ordovician–early Silurian magmatic activity in the northern Yangtze block and Hercynian–Indochina uplift and erosion during the Hercynian movement.（3） The Yangtze crustal growth is episodic, and an increasing amount of ancient recycled material became part of the magmatic activity, as the zircon U–Pb ages are relatively young.

Time-dependent force of infection and effective reproduction ratio in an age-structure dengue transmission model in Bandung City,Indonesia

Dengue virus infection is a leading health problem in many endemic countries,including Indonesia,characterized by high morbidity and wide spread.It is known that the risk factors that influence the transmission intensity vary among different age groups,which can have implications for dengue control strategies.A time-dependent four−age structure model of dengue transmission was constructed in this study.A vaccination scenario as control strategy was also applied to one of the age groups.Daily incidence data of dengue cases from Santo Borromeus Hospital,Bandung,Indonesia,from 2014 to 2016 was used to estimate the infection rate.We used two indicators to identify the changes in dengue transmission intensity for this period in each age group:the annual force of infection(FoI)and the effective reproduction ratio based on a time-dependent transmission rate.The results showed that the yearly FoI of children(age 0–4 years)increased significantly from 2014 to 2015,at 10.08%.Overall,the highest FoI before and after vaccination occurred in youngsters(age 5–14 years),with a FoI of about 6%per year.In addition,based on the daily effective reproduction ratio,it was found that vaccination of youngsters could reduce the number of dengue cases in Bandung city faster than vaccination of children.

Secular trends of asthma mortality in China and the United States from 1990 to 2019

Background:Asthma imposes a large healthcare burden in China and the United States(US).However,the trends of asthma mortality and the relative risk factors have not been comparatively analyzed between the countries.The aim of this study was to compare the mortality and risk factors between China and the US.Methods:The deaths,and mortality rates of asthma in China and the US during 1990–2019 were obtained from the Global Burden of Disease Study 2019.The age–period–cohort model was used to estimate these mortality rates based on a log-linear scale with additive age,period,and cohort effects.The population attributable fractions of risk factors for asthma were estimated.Results:In 1990–2019,the asthma mortality rate was higher in China than in the US.The crude and age-standardized asthma mortality rates trended downward in both China and the US from 1990 to 2019.The decline in mortality was more obvious in China.Mortality gap between the two countries was narrowing.A sex difference in asthma mortality was observed with higher mortality in males in China and females in the US.The age effects showed that mortality increased with age in adults older than 20 years,particularly in the elderly.Downward trends were generally observed in the period and cohort rate ratios in both countries,with China experiencing a more obvious decrease.Smoking and high body mass index(BMI)were the leading risk factors for asthma mortality in China and the US,respectively.Mortality attributable to occupational asthmagens and smoking decreased the most in China and the US,respectively.Conclusions:In 1990–2019,the asthma mortality rate was higher in China than in the US;however,the mortality gap has narrowed.Mortality increased with age in adults.The improvements in asthma death risk with period and birth cohort were more obvious in China than in the US.Smoking,high BMI,and aging are major health problems associated with asthma control.The role of occupational asthmagens in asthma mortality underscores the importance of management and prevention of occupational asthma.

Widespread testing, case isolation and contact tracing may allow safe school reopening with continued moderate physical distancing: A modeling analysis of King County, WA data

Background:In late March 2020,a“Stay Home,Stay Healthy”order was issued in Washington State in response to the COVID-19 pandemic.On May 1,a 4-phase reopening plan began.We investigated whether adjunctive prevention strategies would allow less restrictive physical distancing to avoid second epidemic waves and secure safe school reopening.Methods:We developed a mathematical model,stratifying the population by age,infection status and treatment status to project SARS-CoV-2 transmission during and after the reopening period.The model was parameterized with demographic and contact data from King County,WA and calibrated to confirmed cases,deaths and epidemic peak timing.Adjunctive prevention interventions were simulated assuming different levels of pre-COVID physical interactions(pC_PI)restored.Results:The best model fit estimated~35%pC_PI under the lockdown which prevented~17,000 deaths by May 15.Gradually restoring 75%pC_PI for all age groups between May 15-July 15 would have resulted in~350 daily deaths by early September 2020.Maintaining<45%pC_PI was required with current testing practices to ensure low levels of daily infections and deaths.Increased testing,isolation of symptomatic infections,and contact tracing permitted 60%pC_PI without significant increases in daily deaths before November and allowed opening of schools with<15 daily deaths.Inpatient antiviral treatment was predicted to reduce deaths significantly without lowering cases or hospitalizations.Conclusions:We predict that widespread testing,contact tracing and case isolation would allow relaxation of physical distancing,as well as opening of schools,without a surge in local cases and deaths.

Mesoproterozoic to Paleozoic Nd isotope stratigraphy of the South China continental nucleus and its geological significance

The Yangtze continental nucleus in South China is situated in the Huangling-Shennongjia area in western Hubei Province.It comprises the early Precambrian crystalline basement and generally successive Proterozoic to Phanerozoic sedimentary covers.This paper reports a comprehensive Nd isotope study of fine-grained sedimentary rocks from the regional Mesoproterozoic to early Paleozoic strata.The Nd model ages display a V-shaped variation from ～2.5-2.8 Ga during the late Mesoproterozoic through ～1.5-1.7 Ga during the Neoproterozoic Nanhua Period to ～1.8-2.1 Ga during the Paleozoic Ordovician,with corresponding Nd (t) ranges of 11 to 14,1.1 to 5.3,and 7.9 to 9.9,respectively.This evolutionary trend broadly resembles those documented in the sedimentary strata along the southeastern margin of the Yangtze Craton and within the Jiangnan orogenic belt,indicating that the whole South China block underwent a mantle-input related tectono-magmatic event at ～0.8 Ga or earlier.However,the Huangling-Shennongjia area is discriminated from the other two regions by highly variable model ages (～1.5-2.7 Ga) and Nd (t) values (1.38-12.0) of the early Mesoproterozoic strata.Combined with the Archean model ages of the late Mesoproterozoic strata,it is suggested that the Mesoproterozoic sedimentary provenance of the Yangtze continental nucleus was distinct from that of the southeastern Yangtze Craton,likely indicative of an intervening aulacogen (or rift zone) or oceanic basin.In addition,the high comparability in Neoproterozoic to Paleozoic Nd isotope stratigraphy between the Yangtze Craton and the Jiangnan orogenic belt infers that the whole South China block had shared the same sedimentary basin and provenance since the Yangtze-Cathaysia welding at ～0.9 Ga.Thus,it is proposed that the Yangtze Craton had comprised a collage of micro-continents during the pre-Neoproterozoic until the Rodinia assemblage when the primitive South China block was formed.