2017 - 2018年冬季乌梁素海湖冰表面裂缝形态分析

在2017 - 2018年冬季使用无人机对乌梁素海湖冰的冰面裂缝进行了航拍, 采用改进的自适应阈值分割方法进行图像二值化处理, 提取了冰裂缝的密度和分形维数。分析结果显示： 在固定区域的冰裂缝分形维数在1.35 ~ 1.50间变化, 冰裂缝数量随时间增加, 其分形维数也随之线性增大; 在冰生长期间, 冰厚度与冰裂缝分形维数也呈现出明显的线性关系（相关系数R²=0.75）。冰面不同区域的冰裂缝密度和分形维数在0.017 ~ 0.079、 1.38 ~ 1.64间变化, 且两者之间存在显著的对数相关性（相关系数R²>0.96）, 不同日期航拍数据拟合结果近似相等, 说明冰裂缝密度越大, 对应的分形维数越大。作为表征冰面形态特征的一种物理指标, 建立得到的冰裂缝分形维数与冰厚、 裂缝密度的相关关系, 对未来利用冰面裂缝形态监测冰层的生消过程可提供科学的参考。     

地下水变化对大地原点重力影响的估算

地下水是影响重力变化的重要外部因素之一。从理论上分析了大地原点地下水变化对重力变化的影响,并采用Visual Basic.NET2005实现了模拟估算,得出了二者之间在理论上的函数关系。该结果可为消除地下水变化对大地原点高精度重力测量成果的影响提供参考。     

再论中国大陆斑岩Cu-Mo-Au矿床成矿作用

本文在综述斑岩铜矿(PCDs)最新研究进展基础上,结合最新资料,重点阐释了中国大陆非弧环境PCDs的地球动力学背景、成矿岩浆起源、岩浆-流体系统演化、成矿金属(Cu,Au,Mo)和H₂O来源及富集过程。中国大型PCDs除少量产于岩浆弧外,主要产于碰撞造山环境的构造转换和地壳伸展阶段、陆内造山环境的岩石圈伸展和崩塌阶段以及活化克拉通的边缘及内部。这些非弧环境成矿斑岩多呈彼此孤立的近等间距分布的岩株或岩瘤产出,以高钾为特征,显示埃达克岩地球化学亲和性。成矿岩浆主要起源于加厚的镁铁质新生下地壳或拆沉的古老下地壳,少数起源于遭受早期俯冲板片流体/熔体交代改造过的富集地幔。大陆碰撞和陆内俯冲引起的地壳大规模增厚和紧随其后的板片撕裂、断离、岩石圈拆沉和软流圈上涌,是形成这些成矿岩浆的主要动力机制。与岩浆弧环境斑岩类似,非弧环境斑岩也相对富水(>4%H₂O)和高f(O₂)值(ΔFMQ≥+2),但H₂O不是来自俯冲板片,而是主要来自新生下地壳的角闪石分解或/和幔源富水超钾质岩浆水注入;金属Cu(Au)主要来自新生的镁铁质下地壳中含Cu硫化物的熔融分解,或者来自拆沉下地壳熔体与金属再富集的地幔岩反应,而金属Mo则主要来自具有高Mo丰度的大陆地壳。不论在岩浆弧还是非弧环境,成矿岩浆通常相对富集成矿金属(Cu,Au,Mo),但PCDs的形成并不要求成矿岩浆在初始阶段就异常富集金属组分,但要求金属硫化物相在岩浆流体出溶前没有从岩浆中饱和分离。浅成侵位的斑岩体(1~6 km)虽然可以出溶成矿流体,但大型PCDs通常要求成矿流体出溶自深部(侵位深度≥6 km)、有镁铁质岩浆持续补给的稳定大体积岩浆房。斑岩体可以分凝出不混溶的低盐度的气相和高盐度的液相,岩浆房则直接出溶出高温低盐度的富金属超临界流体。高盐度液相和低密度的超临界气相流体均可以迁移金属,伴随大规模热液蚀变,形成PCDs。     

The environmental implication of diatom fossils in the surface sediment of the Changjiang River estuary(CRE) and its adjacent area

In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent waters, the diatom fossils from 34 surface sediment samples and their relationship with environmental variables were analyzed by principal component analysis and redundancy correspondence analysis. The diversity and abundance of diatom fossils were analyzed. Some annual average parameters of the overlying water (salinity, temperature, turbidity, dissolved oxygen, depth, dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved inorganic silicate) were measured at each sampling site. A total of 113 diatom taxa and one silicoflagellate species were identified in the investigation area. Diatom fossils were better preserved in fine sediments. The absolute abundance of diatom fossils did not significantly diff er between inshore and off shore areas, the species diversity decreased from inshore to off shore. This may be because high nutrients and low salinity promoted the growth of more brackish species in coastal waters. The diatom taxa were divided into three groups, on the basis of their response and indication to environmental changes. For example, Actinocyclus ehrenbergii and Cyclotella stylorum were dominant in coastal waters (Group 1 and Group 3) with high nutrients and low salinity;the relative abundances of Paralia sulcata and Podosira stelliger were significantly higher in off shore sites (Group 2, average 39.5%), which were characterized by high salinity and deep water. Four environmental variables (salinity, dissolved inorganic nitrogen, temperature and water depth) explained the composition and distribution of diatom taxa independently ( P< 0.05), this finding can be applied in further paleoenvironmental reconstruction research in this area.     

Study of the Population Carrying Capacity of Water and Land in Hainan Province

In recent years, the rapid growth of population in Haikou and Sanya has caused extensive concern about the carrying capacity of Hainan Province. To formulate scientific population and environmental policies, it is necessary to research the relationship between population, carrying capacity and economic growth. In this paper, three indicators, grain production, nutrient composition of agricultural products and water resources, are used to measure carrying capacity quantitatively; the employment elasticity coefficient method is used to set the employment elasticity coefficient and the growth rate of regional GDP to estimate the total population needed to support economic growth; PADIS-INT population forecasting software that has parameters to track total fertility rate and net migration rate is used to predict demographic changes. The results show that, as of 2050, the total population of Hainan Province will not have exceeded the upper limit of the carrying capacity of land and water resources. In general, there is no overpopulation problem in the province, but there may be structural problems related to population, such as a large proportion of elderly people, labor shortages, and a high social dependency ratio. It is suggested that the local government should adopt positive population policies, improve the management of natural resources and the environment, and guide the balanced development of population in the province.     

江苏省雷达降水估测集合分析

使用2019年、2020年5—8月江苏省降水分析场及站点观测资料,生成具有定量降水估测(Quantitative Precipitation Estimation, QPE)不确定性时间和空间结构的集合QPE,并用观测降水对集合QPE进行了确定性和概率性检验。确定性验证说明集合QPE能在总体上减小降水量的绝对误差和均方根误差,但也加重了某些区域的降水低估。集合平均能提高估测降水的准确率并减小空报率,也会使漏报增多,这使小雨的TS评分有所降低,但各量级降水TS评分仍能保持在较高水平。集合QPE对各量级降水都有较优的Brier评分,降水量级越大,估测效果越好。集合的离散度较小,且将集合成员排序后,观测值落在两头的频率更高,也反映了离散度偏小。此外,观测值大于集合成员最大值的频率更高,说明集合QPE倾向于低估降水。随着概率阈值的增大,集合估测降水发生的命中率(POD)和假警报率(POFD)逐渐增大,但POD增大的程度比POFD大得多,使相对作用特征曲线为折线。不同概率阈值下的POD和POFD体现了集合QPE对各量级降水都有较高的估测技巧,其中对小雨和中雨分辨能力最好。集合估测小雨和特大暴雨发...     

模拟增雨对荒漠土壤古菌多样性的影响

为探讨生长季增雨对荒漠土壤中古菌群落结构的影响,根据内蒙古磴口多年平均降水量,设计了模拟增雨试验,包括对照、2个增雨时段（生长季前期与后期）、每个时段2个增雨梯度（50%与100%）共计5种处理。增雨后提取荒漠土壤总DNA,对古菌群落编码16S rRNA基因的V4区进行Hiseq测序,分析古菌群落丰度、多样性及结构组成等。结果表明：该地区荒漠土壤中古菌群落均以奇古菌门（Thaumarchaeota）和广古菌门（Euryarchaeota）为优势菌群。NMDS和3种非相似性分析（MRPP、ANOSIM和Adonis）表明,生长季前期增雨未显著改变古菌的群落结构,生长季后期增雨显著改变了古菌的群落结构,当生长季后期增雨量达到100%时,古菌丰富度和多样性显著降低。与氨氧化过程密切相关的奇古菌门（Thaumarchaeota）相对丰度在生长季后期100%增雨条件下显著增加,将促进荒漠土壤的硝化过程。Mantel检验发现荒漠土壤古菌群落结构受土壤湿度、土壤温度、土壤硝态氮含量的影响。未来全球变化背景下降水格局变化将会对荒漠土壤古菌群落结构产生影响,并可能影响氮循环过程。     

地震属性参数在札达—泉水沟深地震测深资料预处理与震相识别中的应用

地震属性分析技术在地球物理勘探领域的广泛应用,启发研究人员将其应用于人工源宽角反射/折射深地震测深剖面的资料预处理和震相识别。采用札达-泉水沟深地震测深资料,提取振幅、信噪比、主频、瞬时带宽、瞬时高频能量等地震属性参数,分析不同参数的物理含义,挑选其中对界面变化敏感的参数,对深地震测深资料进行预处理,并利用P波和S波的联合扫描,提高震相识别的准确性。走时互换结果显示,采用地震属性参数可有效提高震相拾取的准确性,进而提高后续地壳速度结构反演结果的精度。     

Multiple phases analysis of deep seismic sounding records in North China Craton*

The North China Craton (NCC) is a key region to study the destruction of the ancient craton. Two groups of phases (denoted as “Pw1” and “Pw2”), which are parallel to the PmP phase reflected from the Moho discontinuity and the PLP phase reflected from the Lithosphere and Asthenosphere Boundary (LAB) respectively, are found on the record section of the Rongcheng-Xinzhou-Alxa long-range deep seismic sounding profile. The nature of the two phases is still unclear, although they are clearly observable and reverberant. In this paper, we use travel time inversion and amplitude forward modelling to fit the reflected and refracted phases in the lithosphere. The results show: (1) the Pw1 is a multiple reflected phase which is successively reflected by the crystalline basement, the surface, the Moho and then finally received on the surface; (2) the Pw2 phase is also a multiple reflected phase successively reflected by the crystalline basement, the surface, the LAB interface and then received on the surface. We conclude that the significant velocity difference between the thick sedimentary cover and the crystalline basement in the North China rifted basin may be the main reason for generating the multiple reflections. Furthermore, the two multiple reflections provide potent constraints on the lithospheric velocity model, and constitute seismological evidence for the lithospheric thinning in the eastern NCC.     

New paleomagnetic evidences of paleogene tectonic rotation of the Qaidam Basin and adjacent region: mechanism and its tectonic implication

In order to better understand the tectonic evolution of the Qaidam Basin. The authors carried out a paleomagnetic study on 39 samples of 7 sites from Hongsanhan section, northwest Qaidam Basin. Stepwise thermo-demagnetization isolated a high-temperature component (HTC), which passes the fold and reversal tests at 95% confidence level. It suggests that the HTC should be primary. Unblocking temperature (about 685℃) and the experiment of isothermal remanence indicate that hematite is the mainly carrier of the remanence. A tilt-corrected mean direction is: Ds=7.1°, Is=38.5°, α95=7.4°. Corresponding to a palaeopole at, φ＝250.1°E, λ＝72.0°N, A95=6.8°, Compared with the reference APWP of Eurasia, the sampling area occurred a non-significant rotation (3.4°±5.5°) relative to Eurasia since Eocene due to the affect of left-lateral Altyn fault, Based on the paleomagnetic results of early Cretaceous and Teritary within the Qaidam block, we can obtained the mean clockwise rotations from the samples deposited from 160 Ma to 45 Ma is 24.5°±9.0°, and from 38 Ma to present is -0.5°±7.5° relative to present geomagnetism respectively. During the Mid Eocene (45～38 Ma) rotation phase, there should existing an important early tectonic event in northern part of the present-day Tibetan Plateau, which probably represents one of large-scale strike-slip events of the Altyn strike-slip fault.