姚家岭锌金多金属矿床围岩蚀变三维空间定量分析研究

姚家岭锌金多金属矿床是近年来在长江中下游成矿带铜陵矿集区新发现的大型多金属矿床。姚家岭锌金多金属矿床的成矿作用具有多阶段性的特点,矿床范围内围岩蚀变强烈,蚀变类型复杂多样。三维地质信息技术及三维空间分析方法为定量化分析围岩蚀变的空间分布以及与矿化之间的相关关系提供了有利工具。本文基于上述方法,有效地对姚家岭锌金多金属矿床的围岩蚀变的分带性及其与不同矿化之间的关联性行了定量分析。较之于传统研究方法,不仅能快速地对蚀变与矿化的分布特征进行分析,还能从定量的角度获取不同信息之间的规律性和相关性。本文采用的相关方法不但有助于更准确的判定蚀变分带及规律,还可为矿床的成矿模式及找矿模型的建立提供定量化的数据支持。     

电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中的铌钽锆铪

建立电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中铌、钽、锆、铪四种元素的分析方法。将样品与氢氧化钠、过氧化钠混合物放入高温炉中,熔融分解完全,用热水提取,过滤后弃去滤液,将滤纸及沉淀用酒石酸-盐酸溶液溶解,稀释至刻度测定。方法检出限(3s)为:LD(Nb)=0.08μg/g,LD(Ta)=0.04μg/g,LD(Zr)=0.5μg/g,LD(Hf)=0.04μg/g,精密度(RSD%,n=6)为:0.84%~4.21%。该测定方法具有灵敏度高、精密度好、分析速度快、线性范围宽、操作性强等优势。采用该方法对国家一级标准物质进行测定表明,其结果与标准值吻合。此方法已在实际地质调查样品分析中得到应用。     

川西江浪穹窿煌斑岩地球化学特征及锆石U-Pb定年

为精确厘定川西江浪穹窿煌斑岩的形成时代并探讨其成因,对其进行了LA-ICP-MS锆石U-Pb定年及岩石地球化学研究。结果表明,煌斑岩中发育大量2784~604Ma的捕获锆石,最年轻一组岩浆锆石206Pb/238U加权平均年龄为29.85±0.35Ma。岩石地球化学分析显示,煌斑岩具有较低的Si O2含量(47.66%~50.93%)及高的K2O含量(4.98%~6.77%)、(Th/Ta)PM值(14.7~17.6)、(La/Nb)PM值(9.69~13.0),富集轻稀土和大离子亲石元素(如Rb、Sr、Ba和U),亏损高场强元素(如Nb、Ta和Ti)。综合前人研究成果,认为煌斑岩结晶年龄为~30Ma,形成于印度-亚洲大陆后碰撞伸展背景下的板内岩浆作用,且基性岩浆上升过程中明显遭受地壳物质混染。煌斑岩与雅砻江断裂具有密切的时空联系,暗示区内发育的新生代走滑断裂体系可能为岩浆侵位提供了通道。此外,两粒207Pb/206Pb年龄为2784Ma与2439Ma的锆石表明江浪穹窿很可能存在太古宙-古元古代变质基底。     

Regional debris flow susceptibility analysis based on principal component analysis and self-organizing map: a case study in Southwest China

A method was developed to analyze the susceptibilities of 541 regional basins affected by debris flows at the Wudongde Dam site in southwest China. Determining susceptibility requires information on source material quantity and occurrence frequency. However, the large number of debris flows can hinder the individual field investigation in a each small basin. Factors that may trigger debris flows can be identified using remotely sensed interpretation information. Susceptibility analysis can then be conducted based on these factors. In this study, SPOT5 satellite imagery, digital elevation models (DEM), a lithology distribution map, and rainfall monitoring data were used to identify 12 debris flow trigger factors: basin relief ratio, slope gradient in the initiation zone, drainage density, downslope curvature of the main channel, vegetation coverage, main channel aspect, topographic wetness index, Melton’s ruggedness number, lithology, annual rainfall, form factor, and cross-slope curvature of the transportation zone. Principal component analysis was used to obtain the eight principal components of these factors that contribute to susceptibility results. Then, a self-organizing map method was adopted to analyze the principal components, which resulted in a debris flow susceptibility classification. Field validation of 26 debris flow basins was used to evaluate the errors of the susceptibility classification, as well as assess the causes of such errors. The study found that principle component analysis and self-organizing map methodologies are good predictors of basin susceptibility to debris flows.     

黄海南部小黄鱼洄游分布及种群结构特征

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics(especially body length and sex ratio) in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0+ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios(female to male) were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that "the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds" but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.     

中国水产品非关税贸易壁垒的实证研究——基于贸易引力模型

随着贸易自由化程度的提高以及"黄箱政策"的出台,关税壁垒在国际贸易竞争中的作用日益减弱,许多国家逐步设置以进口配额、许可证、检验检疫和技术标准等非关税壁垒为主的贸易保护措施,同时各国在政治、文化和风俗习惯等方面的差异也会对国际贸易产生一定的影响。文章以2000—2014年中国与美国、日本、韩国、加拿大和东盟的贸易面板数据为基础,在Tinbergen(1962)和Poyhonen(1963)所建立的传统贸易引力模型的基础上,对原有模型中的变量进行改进和拓展,创新提出使用军事冲突变量去量化非关税贸易壁垒对我国水产品贸易的影响,同时结合双因素方差分析方法探究贸易品种和国家区域的差异对于贸易总额的影响;结果显示,我国水产品贸易政策存在一定的调整空间,可根据不同国家背景和贸易种类在区域一体化政策、水产品生产、物流渠道建设和文化宣传方面进行政策和方法的改进。     

Effects of experimental warming on soil microbial communities in two contrasting subalpine forest ecosystems,eastern Tibetan Plateau,China

Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (PLFA) analysis and soil chemical characteristics in relation to soil depth in a dragon spruce plantation and a spruce-fir-dominated natural forestin the Eastern Tibetan Plateau. Open-top chambers were utilized to increase the soil and air temperature. Soil samples were collected from the 0-10 cm, 10-20 cm, and 20-30 cm layers after a 4-year warming. Our results showed that the soil microbial community and the contents of TC (Total carbon), TN (Total nitrogen), NO ₃ ^- , and NH ₄ ⁺ responded differently to warming in the two contrasting forests, especially at the 0-10 cm soil depth. Warming increased soil microbial biomass at the 0-20 cm depth of soil in natural forest but reduced it at the 0-10 cm depth ofsoil in the plantation. In contrast, the TC and TN contents were reduced in most soil layers of a natural forest but increased in all of the soil layers of the plantation under warming conditions. This result suggested that the effects of warming on soil microbial community and soil C and N pools would differ according to soil depth and forest types; thus, the two contrasting forests would under go differing changes following the future climate warming in this region.     

Altitudinal trends in δ<Superscript>13</Superscript>C value,stomatal density and nitrogen content of <Emphasis Type="Italic">Pinus tabuliformis</Emphasis> needles on the southern slope of the middle Qinling Mountains,China

In this study, a coniferous tree species (Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains (QLM) to detect the trends in carbon isotope ratio (δ¹³C), leaf nitrogen content (LNC) and stomatal density (SD) with altitude variation in north-subtropical humid mountain climate zone of China. The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m, whereas leaf δ¹³C exhibited a significantly negative correlation with the altitude. Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment, suggesting that the pattern of increasing δ¹³C with the altitude cannot be generalized. The negative correlation between δ¹³C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude. Furthermore, there was a remarkable negative correlation between leaf δ¹³C and LNC. One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ¹³C. The significant negative correlation between leaf δ¹³C and SD over altitudes was also found in the present study, indicating that increases in SD with altitude would reduce, rather than enhance plant δ¹³C values.     

Approximate optimal tracking control for near-surface AUVs with wave disturbances

This paper considers the optimal trajectory tracking control problem for near-surface autonomous underwater vehicles (AUVs) in the presence of wave disturbances. An approximate optimal tracking control (AOTC) approach is proposed. Firstly, a six-degrees-of-freedom (six-DOF) AUV model with its body-fixed coordinate system is decoupled and simplified and then a nonlinear control model of AUVs in the vertical plane is given. Also, an exosystem model of wave disturbances is constructed based on Hirom approximation formula. Secondly, the time-parameterized desired trajectory which is tracked by the AUV’s system is represented by the exosystem. Then, the coupled two-point boundary value (TPBV) problem of optimal tracking control for AUVs is derived from the theory of quadratic optimal control. By using a recently developed successive approximation approach to construct sequences, the coupled TPBV problem is transformed into a problem of solving two decoupled linear differential sequences of state vectors and adjoint vectors. By iteratively solving the two equation sequences, the AOTC law is obtained, which consists of a nonlinear optimal feedback item, an expected output tracking item, a feedforward disturbances rejection item, and a nonlinear compensatory term. Furthermore, a wave disturbances observer model is designed in order to solve the physically realizable problem. Simulation is carried out by using the Remote Environmental Unit (REMUS) AUV model to demonstrate the effectiveness of the proposed algorithm.