Occurrence of Alaskan-type mafic-ultramafic intrusions in the North Qilian Mountains, northwest China: Evidence of Cambrian arc magmatism on the Qilian Block

Field relationships, mineralogy and petrology, whole‐rock chemistry, and age of the Zhamashi mafic–ultramafic intrusion in the North Qilian Mountains, northwest China, have been studied in the present work. The Zhamashi intrusive body consists of ultramafic, gabbroic, and dioritic rocks in a crudely concentrically zoned structure. The ultramafic rocks are layered cumulates with rock types varying continuously from dunite through wehrlite and olivine clinopyroxenite to clinopyroxenite. The gabbroic and dioritic rocks are also layered or massive cumulates with rock types varying continuously from noritic gabbro through hornblende gabbro to diorite. The ultramafic and adjoining gabbroic rocks are discontinuous in lithology and discordant in structure across the interface. The interface is steep, sharp, and fractured. Contact metamorphic zones are well developed between the Zhamashi intrusive body and the country rock. The concentrically zoned structure of the intrusive body and the intrusion into the continental crust are the two main pieces of evidence for considering that the Zhamashi intrusion is Alaskan‐type. The mineral chemistry of the chromian spinels (Cr‐spinels) and clinopyroxenes, and the variation trend of the whole‐rock compositional plot in the (Na₂O + K₂O)–FeO–MgO (AFM) diagram are also supportive of this consideration. The age of the Zhamashi intrusive body, determined with sensitive high mass‐resolution ion microprobe on the zircon grains, is 513.0 ± 4.5 Ma. Parental magma of the Zhamashi intrusion is compositionally close to the primitive magma produced by partial melting of the mantle peridotite. It was differentiated by fractional crystallization at low total pressure and under H₂O‐rich conditions in an arc environment to form all the major rock types. The concentrically zoned structure of the Zhamashi intrusive body was constructed in two stages: formation of a stratiform‐type layered sequence, followed by diapiric re‐emplacement. The occurrence of the Alaskan‐type intrusion suggests an active continental margin and Cambrian arc magmatism for the northern margin of the Qilian Block.     

开采引起的含水层失水对地表下沉的影响

为了改善矿区开采沉陷预计精度,解释华东矿区地表下沉系数大于1的原因,减小采动损害,本文基于现场钻孔水位动态观测结果,获得了覆岩破坏与含水层水位变化的3种对应关系。根据含水层失水后固相颗粒有效应力增加引起岩土体孔隙比的变化,建立了含水层失水固结沉降机理,利用叠加原理,导出了地下开采与含水层失水共同引起的地面沉降计算方法。研究实例表明,失水下沉占煤层开采下沉的25%。      

富钾碱性粗面岩在焙烧过程中矿物结构变化研究

应用Ｘ衍射、化学分析结果和物理化学分析方法,研究富钾粗面岩在不同温度下焙烧所发生的矿物成分和结构变化及其变化机理。富钾粗面岩中钾长石向白榴石的转化率在１１００℃以前主要受焙烧温度控制,在１１００℃以后则受其后的降温速度控制。钾在不同温度焙烧样料中的活性与其中肥料矿物的含量呈正相关。     

电离层高频多普勒记录在扩展-F研究中的应用

本文通过观测实例探讨并论证了电离层高频多普勒观测在扩展-F研究中的应用.实例和相应分析表明:首先,由于高频多普勒记录的时间连续性,有利于从观测角度了解扩展-F的时间演化过程;其次,高频多普勒偏移对不规则结构造成的回波弥散、对不同尺度行进电离层扰动(TID)以及耀斑引起的突然频率偏移(SFD)效应都很敏感,这些现象在记录上出现的时间关系有利于了解扩展-F的触发因素或扩展-F与其他电离层背景扰动之间的联系或相互作用;最后,高频多普勒记录对于持续时间较长(几小时以上)或很短(小于1小时)的扩展-F都能够完整地反映,不会产生因为观测间歇形成的缺失,也可以有效区分究竟是连续一次还是一段时间内断续的扩展-F现象.高频多普勒观测有其自身的优点同时也具有一定的局限性,本文对其局限性诸如缺乏空间分辨率等也做了分析.指出发挥高频多普勒观测的优势,综合应用多种资料,通过不同手段的数据分析和比较,可以更好地为电离层扰动的物理机制和预报研究提供正确的观测依据.     

Simulating spatiotemporal variability of blue and green water resources availability with uncertainty analysis

Due to rapid socioeconomic development, continuous population growth and urbanization, the world is facing a severe shortage of fresh water, particularly in arid and semi‐arid regions. A lack of water will put pressure on agricultural production, water pollution, as well as eco‐environmental degradation. Traditional water resources assessment mainly focused on blue water, ignoring green water. Therefore, analysis of spatiotemporal distribution of blue and green water resources in arid and semi‐arid regions is of great significance for water resources planning and management, especially for harmonizing agricultural water use and eco‐environmental water requirements. This study applied the Soil and Water Assessment Tool (SWAT) model and the Sequential Uncertainty Fitting algorithm (SUFI‐2) to calibrate and validate the SWAT model based on river discharges in the Wei River, the largest tributary of the Yellow River in China. Uncertainty analysis was also performed to quantify the blue and green water resources availability at different spatial scales. The results showed that most parts of the Wei River basin (WRB) experienced a decrease in blue water resources during the recent 50 years with a minimum value in the 1990s. The decrease is particularly significant in the most southern part of the WRB (the Guanzhong Plain), one of the most important grain production bases in China. Variations of green water flow and green water storage were relatively small both on spatial and temporal dimensions. This study provides strategic information for optimal utilization of water resources in arid and semi‐arid river basin. Copyright © 2014 John Wiley & Sons, Ltd.     

Global distribution of thermosteric contribution to sea level rising trend

The sea level derived from TOPEX/Poseidon(T/P) altimetry data shows prominent long term trend and inter-annual variability.The global mean sea level rising rate during 1993-2003 was 2.9 mm a-1.The T/P sea level trend maps the geographical variability.In the Northern Hemisphere(15°-64°N),the sea level rise is very fast at the mid-latitude(20°-40°N) but much slower at the high-latitude,for example,only 0.5 mm a-1 in the latitude band 40°-50°N.In the Southern Hemisphere,the sea level shows high rising rate both in mid-latitude and high-latitude areas,for example,5.1 mm a-1 in the band 40°-50°S.The global thermosteric sea level(TSL) derived from Ishii temperature data was rising during 1993-2003 at a rate of 1.2 mm a-1 and accounted for more than 40% of the global T/P sea level rise.The contributions of the TSL distribution are not spatially uniform;for instance,the percentage is 67% for the Northern Hemisphere and only 29% for the Southern Hemisphere(15°-64°S) and the maximum thermosteric contribution appears in the Pacific Ocean,which contributes more than 60% of the global TSL.The sea level change trend in tropical ocean is mainly caused by the thermosteric effect,which is different from the case of seasonal variability in this area.The TSL variability dominates the T/P sea level rise in the North Atlantic,but it is small in other areas,and shows negative trend at the high-latitude area(40°-60°N,and 50°-60°S).The global TSL during 1945-2003 showed obvious rising trend with the rate of about 0.3 mm a-1 and striking inter-annual and decadal variability with period of 20 years.In the past 60 years,the Atlantic TSL was rising continuously and remarkably,contributing 38% to the global TSL rising.The TSL in the Pacific and Indian Ocean rose with significant inter-annual and decadal variability.The first EOF mode of the global TSL from Ishii temperature data was the ENSO mode in which the time series of the first mode showed steady rising trend.Among the three oceans,the first mode of the Pacific TSL presented the ENSO mode;there was relatively steady rising trend in the Atlantic Ocean,and no dominant mode in the Indian Ocean.     

Desertification Reversion in Relation to Land Use Change and Climate in Naiman County, Inner-Mongolia, China

Analyses of desertified land and land use change in Naiman County of Inner-Mongolia showed that there was a fluctuated in-crease of rain-fed cropland in the period from 1951 to 1960, then decreased until the middle of the 1990＇s, then increased again, while irrigated cropland consistently increased. The woodland and build-up land consistently increased while grassland area de-creased. The area of water body increased from 1975 to 1995 and then decreased while river beach decreased. Wetland change fluctuated with a maximum of 303.53km2 in 1995 and a minimum of 62.08 km2 in 2002. Invasion of cropland into river beach does not only change land coverage on the beach, but also the hydrological process of the river systems and deeply influence wa-ter availability. The correlation between cropland and underground water table is negative and significant. Increase of irrigated cropland is the primary cause of water availability reduction. Water table reduction is negatively correlated to cropland. The total desertified land has decreased since 1975. A rapid increase occurred before 1959, but it is difficult to assess the change of deserti-fication due to lack of data from 1959 to 1975. Changes of different types of desertified lands were different. There is no signifi-cant correlation between land use and different types of desertified land, but there is a significant negative correlation between woodland and total desertified land. The correlation between grassland and total desertified land is positive and significant. There is a significant correlation between different land cover and key factors such as water body and annual precipitation, river beach and runoff, area of shifting dune and annual precipitation, and cropland and underground water table. Desertification reversion in Naiman County is fragile and will be even much more fragile due to population growth, rapid land use and climate change. This will lead to continued invasion of irrigated cropland into more fragile ecosystems and reduction of water availability.     

Carbon and nitrogen mineralization in soils along a desertification gradient in the semiarid Horqin Sandy Land, Northern China

This experiment was conducted in three sites along a desertification gradient in Horqin Sandy Land, Northern China. Soils una-mended and amended with five types of plant residue in a wide range of C:N ratios from 9.9 to 82.2 were incubated for 70 days, during which C and N mineralization were measured. Along the desertification gradient from fixed sand dune to semifixed, and mobile sand dune: cumulative CO2-C produced from the unamended soils was 231.6, 193.3 and 61.9 μg/g, respectively, while net inorganic N was 22.9, 17.6 and 0.9 mg/kg. Soils amended with residues produced more CO2-C than the unamended soils across all sites. During the first 10 days, C mineralization rate of residue-amended soils decreased with the increase of C:N ratio at each site. However, the mineralization rates were poorly correlated with the C:N ratio in subsequent stage of incubation. Soils of mobile sand dune amended with higher C:N ratio (more than 32) residues produced less CO2-C than that of fixed and semifixed sand dune. NO3--N was the predominant form of inorganic N during the mineralization process in sandy soils. Carbon-to-nitrogen ratio (C:N) can be regarded as a predictor of the speed of N mineralization in sandy soil. The more C. microphylla residue with the lowest C:N ratio (9.9) added in soils, the more net inorganic N released. Our results suggest that C. microphylla residue when added to soil would potentially provide short-term plant available N and improve the soil quality in sandy land. The desertification process postponed the release of inorganic N from plant residues.     

基态修正模型的时空数据组织和快照查询方法研究

基态修正模型是目前应用较广的一种时空数据模型.本文分析了基态修正模型中的时空数据特点,采用shapefile文件作为基态数据文件,自主设计差文件格式来存储和组织变化数据.在此基础上设计了快照查询的算法、流程和查询结果的显示方法.为了给用户提供更直观、更充分的时空信息,本文提出了一种双屏幕多视图的时空数据显示模式.采用VC.NET从底层开发了一个时态地理信息系统平台,并以中南大学主校区的时空数据为实验数据对上述算法和模式进行了检验.实验表明,本文所设计的算法可行,快照显示模式能够提供更直观、更丰富、对比性强的信息内容,是时空信息显示的一种可行模式.     

科尔沁沙地植物功能性状的尺度变异及关联

调查了科尔沁沙地流动沙丘、半固定沙丘和固定沙丘18个样地的物种组成,测定了28种植物的叶面积(LA)、比叶面积(SLA)和叶干物质含量(LDMC)等3个植物功能性状,并用性状梯度分析法对3个功能性状在群落水平上的变化进行了分解,研究了沙丘固定过程中的植物功能性状的尺度变异及其与生境变化的关系。结果表明:(1)随着沙丘的固定,群落平均LA逐渐增大,群落平均SLA及LDMC在半固定沙丘上最小;(2)群落平均SLA的生态位宽度随着沙丘固定程度依次减小,流动、半固定沙丘植物群落的适应能力较固定沙丘更强;(3)沙丘固定过程中物种性状值的变化与群落内共生植物种性状间变异的关联相比于群落间性状的变异更密切。沙丘固定导致了物种LA与LDMC较强的正相关关系,两性状在群落间的依赖性比群落内的强。物种在群落内和群落间采取不同的策略来适应沙丘固定过程生境的变化。