Late Neoproterozoic crustal growth in the European Variscides: Nd isotope and geochemical evidence from the Sierra de Córdoba Andesites (Ossa-Morena Zone, Southern Spain)

Because the Hercynian overprint was extremely weak, the Sierra de Córdoba (southeastern Ossa-Morena Zone, OMZ) provides an excellent opportunity to study the tectonic evolution of sequences deposited close to the Late Neoproterozoic–Early Palaeozoic boundary. In order to put constraints on the sources and geodynamic significance of the Late Proterozoic magmatism, a representative set of 18 igneous rocks, and 3 interbedded sedimentary rocks from the San Jerónimo Formation have been studied for major and trace element geochemistry and for the Sm–Nd isotopic systematics. The igneous rocks are generally porphyritic to microporphyritic andesites, with abundant plagioclase (±amphibole) phenocrysts. With the exception of two intrusive rocks, possibly not related to the Late Proterozoic episode, all the samples display positive _{Nd550 Ma} values, ranging from +2.9 to +7.6. Most of them, with +4<_{Nd550 Ma}<+6, exhibit LREE enrichment, high La/Nb ratios, and elevated Zr/Nb ratios ranging from 21 to 32. There is no obvious correlation between the shape of REE patterns, La/Nb ratios and _{Nd550 Ma} values, precluding simple models of late-stage interaction with typical crustal components having low _Nd and high LREE/HREE and La/Nb ratios. Based on their major element composition and enriched, continental crust-like trace element characteristics, combined with distinctly positive _Nd initial values, the Córdoba andesites document an episode of crustal growth through the addition of calc-alkaline magmas, extracted from a mantle reservoir which was strongly depleted in LREE on a time-integrated basis. The occurrence of interlayered sediments of continental provenance (negative _Nd values) does not favour a purely ensimatic arc setting, remote from continental land masses, for this subduction-related magmatism, but the geochemical data suggest an active margin environment located on relatively juvenile crust. In any case, the Córdoba andesites document the addition of materials chemically similar to the bulk continental crust which were extracted from mantle sources with strong time-integrated LREE depletion. Therefore, they provide evidence for crustal growth related to Cadomian orogenic events during Late Proterozoic times.     

Substrate damage and recovery after giant clam shell mining at remote coral reefs in the southern South China Sea

Giant clam shell mining(GCSM),a unique phenomenon occurring at remote coral reefs in the southern South China Sea(SCS),forms striking scars on the reef flats and damages the reef flat substrate.Through image analyses at three times(2004.02.02,2014.02.26,and 2019.04.10)and in situ surveys at Ximen Reef,a representative site that has experienced GCSM,we quantified the GCSM-generated substrate damage and the corre-sponding recovery.GCSM was estimated to have occurred sometime between 2012 and 2014,causing reduction in live coral subarea and formation of micro-relief as trenches and mounds.GCSM-generated damage was restricted to the reef flat.After GCSM,coral and algae subarea increased,and the trenches and mounds tended to be filled and eroded,rep-resenting a natural recovery of the substrate.The legal prohibition on human disturbances at the coral reefs contributed to substrate recovery at Ximen Reef.This case also implied that recovery of the other coral reefs that suffered from GCSM is possible.     

滇西南发现石英面状变形构造

采自云南省西南部澜沧江中游临景大桥以东约2km、勐戛河下游北岸的岩石样品的薄片中发现了非常清晰的石英面状变形构造(PDFs)。根据伦敦大学矿物岩石与冰物理实验室费氏台(universalstage)测量分析结果、样品所在地地层时代特征和航卫遥感图像特征的综合分析,认为该PDFs属陨击成因,其陨击事件大约发生在白垩/第三纪边界(距今65Ma),所引起的冲击变质作用已接近最高级阶段的高压二氧化硅相,样品位置接近陨击坑的中心。     

德国能源转型进程及对中国的启示

总结发达国家能源转型过程中的经验和教训,对中国推动能源转型和实现“双碳”目标具有重要意义。文中回顾了中国和德国电力结构的演变进程,阐述了中国和德国能源转型的机制,并以2022年3月19日为例,分析了德国电力系统灵活性调节的经验。研究表明,健全的法律体系为德国能源转型提供了重要保障,“煤炭委员会”和相关财政支持有效解决了煤电转型过程中的问题,电力市场化是发展可再生主体新型电力系统的重要前提,风力和光伏发电精准预测与管理是可再生能源消纳的关键,煤电和互联互通的欧洲电网是当前德国电力供给的重要保障,过于激进的退煤去核战略是造成2022年德国能源危机的重要原因。最后,从法律保障、市场改革和可再生能源预测与管理等方面提出了中国能源转型的政策建议。     

CHARACTERISTICS OF MULTI-SCALE GRAVITY FIELD VARIATION AND SEISMOGENIC MECHANISM ANALYSIS IN THE SOUTHEASTERN TIBETAN PLATEAU

As the most basic geophysical field, the earth gravity field has achieved wide attention, and its spatial anomaly characteristics and dynamic variation can provide important scientific basis for studying the internal structure and dynamics of the Earth. Based on the mobile gravity observation data of the southeastern Tibetan plateau from 2013 to 2016, the dynamic variation tendency and anomaly characteristics of the regional gravity field in different temporal resolutions are obtained before and after the Ludian and Jinggu earthquakes in the study area respectively. The method of wavelet multi-scale decomposition is used to analyze the relationships of gravity field variation with the earth movement, material density change, and strong earthquake preparation. The deep material variation, dynamic process and the mechanism of earthquake inoculation in the southeastern Tibetan plateau are further discussed. Results indicate that the gravity field variation in the source region before the Ludian and Jinggu earthquake respectively is characterized by obvious positive and negative anomalous transition zone and gradient zone that are consistent with the direction of fault tectonics, suggesting the strong crustal movement and mass migration during the earthquake incubation period. The result of wavelet multi-scale decomposition of the gravity field during the period from September 2013 to April 2014 shows that the gravity field variation at different depth and space scale in the crust and upper mantle of the southeastern Tibetan plateau is significantly correlated with seismic distribution and the location of active fault zone. This indicates that the earthquake inoculation in the study area is closely related to the fault movement and the distribution of material density in the crust and upper mantle, which may be affected by the complex deep dynamic process of the material migration in the crust and mantle. The characteristic that strong earthquakes always occur near positive and negative anomaly transition zones and gradient zones of gravity field change is preliminarily explained, based on the dynamic process of material migration in the crust and upper mantle of the southeastern Tibetan plateau. The research results of this paper have some reference value to the study on the earth movement and seismogenic mechanism.     

Detection of thermal pollution from power plants on China’s eastern coast using remote sensing data

The acceleration of the industrialization process in China has increased the demand for electricity and triggered a power-plant building boom, especially along China’s eastern coast, where the economy gets off early and enjoys a fast development. The thermal plumes, residual chlorine, nuclides and other pollutions produced by the thermal and nuclear power plants have exerted an impact on the coastal eco-environment. To monitor the thermal pollution from the power plants at Yueqing Bay on the eastern coast, in this research, the distribution of sea surface temperature (SST) surrounding the power plants is obtained by using the SST retrieval methods developed for Landsat Enhanced Thematic Mapper Plus (ETM+), HJ-1B infrared sensor (IRS) and Terra moderate resolution imaging spectroradiometer (MODIS) data. The comparison of the SST retrieval results before and after the operation of power plants indicates that the total area of sea waters that is impacted by the thermal discharge from the two power plants at Yueqing Bay is approximately 17.95 km², with the highest SST rise of 4.5 °C appearing over the waters around the outlet of the Huaneng Yuhuan power plant on the eastern shore, whereas the highest SST rise around the Zheneng Yueqing power plant on the western shore reaches 3.8 °C. The intensity and scope of influence of the thermal discharge mainly depend on the installed capacity of power plants, coastal terrain, and tide. Although the area where the SST rise is more than 3 °C is not large, thermal discharge still has an impact on bay ecosystems due to the relatively closed nature of the bay environment. Due to the influence of rising water temperatures on the reproduction and individual evolution of fish, shrimp, crabs, shellfish and other aquatic creatures, in the long term, the thermal pollution from coastal power plants will affect the volume of natural fishery and biological resources throughout the waters. The quantitative retrieval results also suggest that relative to MODIS data, Landsat ETM+ and HJ-1B IRS data with a high spatial resolution are more applicable to the estimation of small-scale SST, and IRS data with a high temporal resolution are more helpful in the study of spatio-temporal variability of thermal plumes from coastal power plants.     

跨南海西南次海盆OBS、多道地震与重力联合调查

对跨南海西南次海盆及两侧陆缘的一条1050km长的、包括海底地震(OBS)、长排列多道地震和重磁在内的综合地球物理探测剖面(CFT)进行了构造成像和研究。在多道地震成像基础上建立了CFT剖面初始速度模型, 进而通过初至波层析成像方法反演了CFT剖面的速度结构模型, 在重力异常资料的约束下建立了CFT剖面的综合地壳结构模型。讨论了沿CFT剖面出现的下地壳高速体、龙门海山的低密度物质等地质问题。结果表明, 下地壳高速层在北部陆坡、西南海盆和南部南沙地块均有分布, 厚度在0~4km之间, 可能与陆缘下地壳物质和地幔物质熔融混合, 以及深海盆海底扩张期间构造拉伸导致地幔蛇纹岩化有关。     

Intelligent modelling of clay compressibility using hybrid meta-heuristic and machine learning algorithms

Compression index Ccis an essential parameter in geotechnical design for which the effectiveness of correlation is still a challenge.This paper suggests a novel modelling approach using machine learning(ML)technique.The performance of five commonly used machine learning(ML)algorithms,i.e.back-propagation neural network(BPNN),extreme learning machine(ELM),support vector machine(SVM),random forest(RF)and evolutionary polynomial regression(EPR)in predicting Cc is comprehensively investigated.A database with a total number of 311 datasets including three input variables,i.e.initial void ratio e0,liquid limit water content wL,plasticity index Ip,and one output variable Cc is first established.Genetic algorithm(GA)is used to optimize the hyper-parameters in five ML algorithms,and the average prediction error for the 10-fold cross-validation(CV)sets is set as thefitness function in the GA for enhancing the robustness of ML models.The results indicate that ML models outperform empirical prediction formulations with lower prediction error.RF yields the lowest error followed by BPNN,ELM,EPR and SVM.If the ranges of input variables in the database are large enough,BPNN and RF models are recommended to predict Cc.Furthermore,if the distribution of input variables is continuous,RF model is the best one.Otherwise,EPR model is recommended if the ranges of input variables are small.The predicted correlations between input and output variables using five ML models show great agreement with the physical explanation.     

基于 Biot-Stoll 模型声速反演中的参数选择——以南海南部沉积物为例

研究海底表层沉积物性质对海洋矿产资源探测、海洋工程建设等有重要的意义。Biot-Stoll模型可以模拟预测海底沉积物的物理性质,但采用不同的参数模拟的效果不同。Stoll参数是各种海洋环境下模型达到最佳预测的单一数值的形式;Schock参数则是对渗透率、孔隙大小、沉积物孔隙曲折度等修改后的函数表达式形式,更接近沉积物实际情况。采用Stoll参数和Schock参数分别计算了南海南部海区海底沉积物纵波速度,并对南海南部沉积物样品进行了计算和实测对比,结果表明,采用Stoll参数计算误差较大,平均为3.962%;采用Schock参数计算误差较小,平均为0.847%。因此,在南海南部海区采用Schock参数预测海底表层沉积物物理性质更准确。     

浅剖资料在南海北部东沙西南海域水合物调查中的应用

南海北部东沙海域陆坡已经被证实为天然气水合物前景分布区,浅地层剖面数据以其高效率采集过程和浅表层高分辨率的特点被国内外学者应用到天然气水合物调查中并取得了很多成果。以南海北部东沙西南海域的两条浅剖测线为例,分析了该区浅表层沉积物的声学特征,并在浅剖剖面上发现了浅层含气带以及气体泄露现象,初步推测为深部的天然气水合物分解后通过断层运移到浅层中形成了浅层含气带,部分浅层气体还通过泄露点喷射到海水中从而形成了剖面中的气体泄露现象。最后,进一步通过对研究区域的沉积及气源条件、温压条件、地质及生物证据的讨论,证实该区具有天然气水合物发育的基本条件,因此,可以证实上述浅剖资料解释中关于天然气水合物的推测。