Geochemistry and age of seamounts in the West Pacific: mantle processes and petrogenetic implications

Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province(WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new ^(40)Ar/^(39) Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt(OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element(REE) patterns and a spider diagram of the samples in this study show OIB(Ocean Island Basalt) like behavior. The range of ^(87)Sr/^(86) Sr values is from 0.704 60 to 0.706 24, the range of ^(206)Pb/^(204) Pb values is from 18.241 to 18.599, and the range of ^(143)Nd/^(144) Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new ^(40)Ar/^(39) Ar age data show that these seamounts formed at ～97 and ～106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins.

Geochemical characteristics of platinum-group elements in polymetallic nodules from the Northwest Pacific Ocean

Polymetallic nodules and cobalt (Co)-rich crusts are enriched in platinum-group elements (PGEs),especially platinum (Pt) and may be important sinks of PGEs.At present,little information is available on PGEs in polymetallic nodules,and their geochemical characteristics and the causes of PGEs enrichment are unclear.Here PGEs of polymetallic nodules from abyssal basin in the Marcus-Wake Seamount area of the Northwest Pacific Ocean are reported and compared with the published PGEs data of polymetallic nodules and Co-rich crusts in the Pacific.The total PGEs (ΣPGE) content of polymetallic nodules in study area is 258×10^–9) in average,markedly higher than that of Clarion-Clipperton Zone (CCZ) nodules (ΣPGE=127×10^–9) and lower than that of Co-rich crusts in the Marcus-Wake Seamount (ΣPGE=653×10^–9),similar to that of Co-rich crusts in the South China Sea(ΣPGE=252×10^~–9).The CI chondrite-normalized PGEs patterns in different regions of polymetallic nodules and cobalt-rich crusts are highly consistent,with all being characterized by positive Pt and negative Pd anomalies These results,together with those of previous studies,indicate that PGEs in polymetallic nodules and Co-rich crusts are mainly derived directly from seawater.Pt contents of polymetallic nodules from the study area are negatively correlated with water depth,and Pt/ΣPGE ratios in nodules there are also lower than those of the Corich crusts in the adjacent area,indicating that sedimentary water depth and oxygen fugacity of ambient seawater are the possible important controlling factors for Pt accumulation in crusts and nodules.

Evolution and diagenetic implications of framboids in the methane-related carbonates of the northern Okinawa Trough

Authigenic carbonate samples were collected from the northern Okinawa Trough.Based on their carbon and oxygen isotopes,these samples were found to be methane-related carbonates precipitated by the anaerobic oxidation of methane(AOM).Petrological analysis revealed numerous framboidal pyrites that had been partly oxidized.In order to trace the variation and diagenetic information of these framboidal pyrites,their diameters and geochemical components were studied using an electron probe.The results showed that their diameters varied from 4μm to 17μm(n=60;geometric mean of 9.9μm)and were of a normal distribution.The diameters of single pyrite that formed the framboidal pyrites varied from 1μm to 2μm.The framboidal pyrites with diameters of 6–14μm accounted for~80%of the total.The geometric mean of 9.9μm indicates that they are probably diagenetic pyrites that were precipitated in a lower dysoxic environment(weakly oxygenated bottom waters).The S/Fe ratio of the framboidal minerals ranged from 0 to 1.67,and the pyrite content of single framboid varied between 0%and 86.4%.Therefore,numerous pyrites were oxygenated to iron oxides or oxyhydroxides,and were retained as pseudomorphism pyrites.The size of framboidal pyrites precipitated in cold seeps can be used to trace the redox environment;however,acquisition of additional data via investigation of different cold seeps is necessary to obtain more persuasive results.

Petrology and geochemistry of serpentinized peridotites from Hahajima Seamount in Izu-Bonin forearc region

Serpentinites,which contain up to 13 wt%of water,are important reservoirs for chemical recycling in subduction zones.In the past two decades,forearc mantle serpentinites were identified in different locations around the world.Here,we present petrology and whole rock chemistry of ultramafic and mafic rocks dredged from the Hahajima Seamount,which is located 24–40 km west to the junction of the Izu-Bonin Trench and the Mariana Trench.Nearly all the collected samples are extensively hydrated,and olivine grains in ultramafic rocks are replaced by serpentine minerals,with only one sample preserving remaining trace of orthopyroxene.Our new results show that the Hahajima serpentinized peridotite samples are all MgO-rich(~42 wt%),but have low contents in Al2O3,CaO,rare earth and high field strength elements,which is consistent with the overall depleted character of their mantle protoliths.Model calculations indicate that these Hahajima peridotite samples were derived from 10%–25%partial melting of the presumed fertile mantle source,which is generally lower than those of peridotites from Torishima Forearc Seamount,Conical Seamount and South Chamorro Seamount(mostly>25%).All the serpentinites from these four forearc seamounts show strong enrichment in fluid-mobile and lithophile elements(Li,Sr,Pb and U).In details,Hahajima Seamount serpentinites do not have obvious enrichment in Cs and Rb,and display remarkably high abundances of U.These observations indicate that the serpentinization of Hahajima peridotites occurred by addition of seawater or low temperature seawater-derived hydrothermal fluid,without or with little contribution from slab-derived fluids.The geochemical signature of serpentinites from Hahajima Seamount could be interpreted as the result of the combination of extensive partial melting and subsequent percolation of seawater through the mantle wedge.

Petrology and geochemistry of cold seep carbonates from the northern Okinawa Trough,East China Sea:implications to early diagenesis

Carbonate samples were collected from the northern Okinawa Trough in the East China Sea in 2013.The petrology,mineralogy,carbon and oxygen isotopes,and rare earth elements(REEs)of these samples were analyzed.Aragonite,high-Mg calcite,and dolomite were the main carbonate minerals,the contents of which varied greatly among the carbonate samples.Petrological observations revealed the common occurrence of framboidal pyrites.Theδ^(13)C values of carbonates varied from-53.7‰to-39.3‰(average of-47.3‰based on Vienna Pee Dee Belemnite(V-PDB),n=9),and theδ^(18)O values ranged from 0.6‰to 3.4‰(average of 1.9‰;V-PDB,n=9).The carbon and oxygen isotope characteristics indicated that the carbonates precipitated during the anaerobic oxidation of methane.The carbon source was a mixture of thermogenic methane and biogenic methane,possibly with a greater contribution from the former.The oxygen isotope data showed that gas hydrate dissociation occurred during carbonate precipitation.The Ce anomalies suggested that the carbonates precipitated in an anoxic environment.A slight enrichment of middle REEs(MREEs)could be attributable to the early diagenesis.The structures,minerals,oxygen isotopes,and MREEs all indicated that the carbonates experienced some degree of early diagenesis.Therefore,the infl uence of early diagenesis should be considered when using geological and geochemical proxies to reconstruct original methane seepage environments.

Source and magmatic evolution of ocean island basalts from the Pohnpei Island,Northwest Pacific Ocean:Insights from olivine geochemistry

The compositional variability of ocean island basalts(OIBs)is thought to reflect partial melting of a lithologicallyheterogeneous mantle source dominated by either pyroxenite or peridotite.The Pohnpei Island in Micronesia,which is associated with the Caroline hotspot,is suggested to have been generated from partial melting of a pyroxenite-rich mantle.To examine this hypothesis,we present new major-and trace-element compositions of olivine phenocrysts in basalts from the island.The olivines exhibit large systematic inter-and intra-crystalline compositional variability.In Sample DS1,olivines record compositional zonation,in which cores have relatively high Fo(77–85),Ni(550×10^(-6 )–2392×10^(-6 )),and Fe/Mn ratios(66–82),whereas rims have lower Fo(71–78),Ni(526×10^(-6 )–1537×10^(-6 )),and Fe/Mn ratios(51–62).By contrast,olivines within other samples preserve no clear compositional zonation,exhibiting similar or slightly lower Fo values(66–78),Ni contents(401×10^(-6 )–1268×10^(-6 )),and Fe/Mn ratios(53–69)as the rims of zoned crystals.The distinct chemical contrast between the two different types of olivine suggests they formed in magma chambers at different depths.Analysis using forward petrological modeling and multi-element indicators(Fe/Mn,Zn/Fe,FC3MS(FeO^(T)/CaO-(3×MgO/SiO^(2))),Mn/Zn,and Ni/(Mg/Fe))of whole-rock samples and high-Fo olivines is inconsistent with a pyroxenite-rich mantle source.We suggest these inconsistencies reflect an influence on the partition coefficients of Ni and Mn between olivine and liquid during melting at variable pressures and temperatures.In addition,magma recharge and mixing within the magmatic plumbing system can change the composition of olivine.We suggest that identification of the mantle source of OIBs in volcanic islands such as the Pohnpei Island using olivine geochemistry should be treated with caution.

Bedrock samples from the Chukchi Borderland, Arctic Ocean——First Chinese dredge in the polar regions

The Chukchi Borderland is a relict continental block in the Arctic Ocean.Its origin and tectonic processes are of great significance for understanding the formation model of the Amerasia Basin and the configurations of the Mesozoic Arctic regions.Due to the harsh environment and rare geological and geophysical data,the evolution of the Chukchi Borderland is still unclear(e.g.,Grantz et al.,1998,2011).We conducted two rock dredges and a multibeam full coverage survey of 830 km2 in the Northwind Abyssal Plain of the Chukchi Borderland during the Chinese ninth Arctic scientific expedition in 2018.This is the first rock dredge survey of China in the polar regions with floating ice,and is just after the HLY0905 dredge at the Northwind Abyssal Plain in 2009(Mayer and Armstrong,2011).The retrieved samples will provide new information for understanding the origin and tectonic evolution of the Chukchi Borderland.

Nano-effect enhanced cooperative luminescence of Yb^(3+) clusters in bulk materials

In order to improve the multi-ion cooperative transition, we proposed and exploited a novel nanoscale effect, namely the nanoshell effect in bulk materials. Based on the effect, an optimal material structure was designed by coating the surfaces of Ca F_(2):Yb^(3+)micron size particles with ZrO_(2). An about 2 times higher intensity of cooperative luminescence is observed upon laser excitation at 980 nm. Dynamical analysis exhibits that the novel effect plays a key role in improving the performance of cooperative transitions. Our results also suggest that the nanoshell effect in bulk materials is likely to be significant in some special cases, which have not been reported yet in the literature.

Combined Effect of Outdoor Time and Other Modifiable Factors on Myopia Incidence Among Children and Adolescents—9 PLADs,China,2020

Summary What is already known about this topic?Myopia has been identified as a significant emerging challenge and policy priority among children and adolescents in China by the Ministry of Education and seven other departments.Limited research has been conducted to investigate the collective impact of outdoor time and other modifiable factors on the incidence of myopia.

奥斯瓦尔德熟化过程的控制

作为一种热力学的必然过程,奥斯瓦尔德熟化通常会发生在材料生长的后期阶段,并导致材料的性能参数变差.几十年来,如何阻止或控制奥斯瓦尔德熟化一直是材料制备领域的一个挑战.尤其在纳米材料制备中,奥斯瓦尔德熟化已经成为了获得优良材料的一大障碍.在大量实验和分析的基础上,本文发现临界浓度和时间窗口是阻止和抑制奥斯瓦尔德熟化发生的两个关键因素.我们利用全自动纳米材料合成仪,对制备NaREF4纳米材料的过程进行一系列精确控制,探明了奥斯瓦尔德熟化的规律,将熟化划分为三种类型.通过控制奥斯瓦尔德熟化的发生,不仅获得了高质量的纳米晶体,而且还开发了核-壳纳米材料制备策略.考虑到奥斯瓦尔德熟化的普遍性,这种方法可以应用于许多纳米材料的制备过程.

Bandgap narrowing and polarization enhancement in(K,Na,Li)(Nb,Sb,Ta)O_(3)+x%Fe_(2)O_(3) lead-free ceramics for photovoltaic applications

The need for ferroelectric materials with both narrow bandgaps(Eg)and large remanent polarization(Pr)remains a key challenge to the development of high-efficiency ferroelectric photovoltaic(FPV)devices.In this work,[(K_(0.43)Na_(0.57))_(0.94)Li_(0.06)][(Nb_(0.94)Sb_(0.06))_(0.95)Ta_(0.05)]O_(3)(KNLNST)-based lead-free ceramics with narrow Eg and large P are obtained via Fe_(2)O_(3) doping.By optimizing the level of Fe_(2)O_(3) doping,a KNLNST+1.3%Fe_(2)O_(3) ceramic is fabricated that simultaneously possesses a narrow Eg of 1.74 eV and a large Pr of 27.05μC/cm^(2).These values are much superior to those of undoped KNLNST ceramics(Eg=3.1 eV and Pr=17.73μC/cm^(2)).While the large P stems from the increment of the volume ratio between the orthorhombic and tetragonal phases(Vo/VT)in KNLNST ceramics by proper amount of Fe3+doping,the narrow Eg is attributed to the coupling interaction between the Fe3+dopants and the B-site Sb3+host ions.Moreover,a switchable photovoltaic effect caused by the ferroelectric depolarization electric field(Edp)is observed in the KNLNST+1.3%Fe_(2)O_(3) ceramic-based device.Thanks to the narrower Eg and larger P,of the doped ceramic,the photovoltaic performance of the corresponding device(open-circuit voltage(Voc)=-5.28 V and short-circuit current density(JSC)=0.051μA/cm^(2))under a downward poling state is significantly superior to that of an undoped KNLNST-based device(Voc=-0.46 V and Jse=0.039μA/cm^(2)).This work offers a feasible approach to developing ferroelectric materials with narrow bandgaps and large Pr for photovoltaic applications.

Association Between Combinations of 24-Hour Movement Behaviors and Depression Among Adolescents—Inner Mongolia Autonomous Region,China,2019–2021

Summary What is already known about this topic?In recent years,there has been growing concern regarding the escalating rates of depression among adolescents.While certain individual behaviors have been suggested as potential protective factors for mental health,there is a scarcity of research examining the collective influence of 24-hour movement behaviors.

Global trends and regional differences in non-transport unintentional injuries mortality among children and adolescents, 1990 to 2019: results from the Global Burden of Disease 2019 study

Background::Non-transport unintentional injuries(NTUIs)are major public concerns,especially among children and adolescents in low-and middle-income countries.With environmental and cognitive changes,a recent systematic description of global trends and regional differences concerning NTUIs is urgently needed for the global agenda of relevant policy-making and intervention target findings.Methods::We used mortality,population,and socio-demographic-index(SDI)data from Global Burden of Disease 2019 to analyze the trends of NTUIs mortality.We applied the slope index of inequality(SII)and relative index of inequality(RII)to measure the absolute and relative inequality between countries and territories.The concentration curve and concentration index(CI)were also used to measure the inequality.We conducted a sensitivity analysis to make our findings credible.Results::In 2019,there were 205,000 deaths due to NTUIs among children and adolescents aged 5 to 24 years,which decreased from 375,000 in 1990.In 2019,the age-standardized mortality rate(ASMR)was 8.13 per 100,000,ranging from the lowest in the Netherlands(0.90 per 100,000)to the highest in the Solomon Islands(29.34 per 100,000).The low-middle SDI group had the highest ASMR of NTUIs,while the low SDI group had the slowest decrease.After excluding the death caused by"exposure to forces of nature"and"other unintentional injuries",drowning accounted for the most deaths in almost every SDI group,gender,and age group,but the major causes of death varied in different subgroups.For example,animal contact was a major cause in low and low-middle SDI groups but less in high SDI groups,while high and high-middle SDI groups had a higher proportion of deaths for foreign body and poisonings.The SII showed a declining trend,but the RII and CI did not,which might indicate that inequality was persistent.Similar results were found in the sensitivity analysis.Conclusions::Despite the declining trend of the mortality rate and the narrowing gap between countries,there were still a large number of children and adolescents dying from NTUIs,and those experiencing social-economic disadvantages remained at high mortality.Embedding the prevention of NTUIs into sustainable development goals might contribute to the progress of reducing death and inequalities,which ensures that no one is left behind.

Growth regularity and phase diagrams of NaLu_(0.795−x)Y_(x)F_(4) upconversion nanocrystals synthesized by automatic nanomaterial synthesizer

The growth regularities of nanomaterials are often concealed by the contingency of preparation. Therefore, it is always very difficult to figure out growth regularities of nanomaterials due to the accompanying undulation of products. A series of precise synthesis was performed by using an automatic nanomaterial synthesizer (ANS) in order to explore the growth regularity of complex NaREF4 (RE: rare earth) upconversion nanocrystals (UCNCs). The use of ANS significantly enhances the experimental controllability, repeatability, and success rate. Mass experimental research exhibited that the NaLu_(0.795−x)Y_(x)F_(4):Yb^(3+)/Tm^(3+) (x = 0−0.795) UCNCs can vary their sizes continuously in a wide range to accurately meet the experimenter’s design merely by controlling the concentration of Y^(3+). A notable growth regularity was obtained and intuitively shown in growth phase diagrams. Furthermore, in the case of having excellent monodispersity, pure hexagonal phase, and uniform morphology, the prepared UCNCs still retained superior upconversion luminescent (UCL) properties. The regular changes in UCL properties further confirmed the growth regularity of the UCNCs. After analyzing the experimental data, we found that NaLu_(0.795−x)Y_(x)F_(4) combined the advantages of NaYF_(4) and NaLuF_(4) hosts with desired sizes. These results provide a guidance for the exploration of growth regularities of other similar nanomaterials and also for the structure design of the required nanomaterials.