Impact of climate change and variability on water resources in Heihe River Basin

Studies indicate that the climate has experienced a dramatic change in the Heihe River Basin with scope of temperature rise reaching 0.5-1.1oC in the 1990s compared to the mean value of the period 1960-1990, precipitation increased 18.5 mm in the 1990s compared to the 1950s, and 6.5 mm in the 1990s compared to the mean value of the period 1960-1990, water resources decreased 2.6×108 m3 in the 1990s compared to the 1950s, and 0.4×108 m3 in the 1990s compared to the mean value of the period 1960-1990. These changes have exerted a greater effect on the local environment and socio-economy, and also made the condition worsening in water resources utilizations in the Heihe Rver Basin.     

Eco-environment range in the source regions of the Yangtze and Yellow rivers

Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×104 km2. Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×104 km2. Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River.     

Quantitative classification and analysis on plant communities in the middle reaches of the Tarim River

Plant communities were sampled in the lower reaches of the Tarim River, Xinjiang. The results showed that there are 23 species belonging to 21 genera in 11 families, most of which have low occurrence frequency in quadrats. The most common species is Tamarix ramosissima, which occurred in 17 sites accounting for 89.47% of the total 19 sites. Quantitative classification (TWINSPAN) and ordination (CCA) methods were used to study the distribution patterns of 23 plant species in 19 sites in this valley. TWINSPAN results showed that the plant communities in the middle reaches of the Tarim River could be divided into 3 groups and the sampling sites could be divided into 7 types in 3 groups. CCA results were consistent with TWINSPAN results, and showed species distribution patterns correlated with major environmental variables of groundwater level and soil moisture.     

Water discharge changes of the Changjiang River downstream Datong during dry season

Based on hydrometric data and extensive investigations on water-extracting projects, this paper presents a preliminary study on water discharge changes between Datong and Xuliujing during dry season. The natural hydrological processes and human factors that influence the water discharge are analyzed with the help of GIS method. The investigations indicate that the water-extracting projects downstream from Datong to Xuliujing had amounted to 64 in number by the end of 2000, with a water-extracting capacity up to 4,626 m3/s averaged in a tidal cycle. The water extraction from the Changjiang River has become the most important factor influencing the water discharge downstream Datong during dry season. The potential magnitude in water discharge changes are estimated based on historical records of water extraction and a water balance model. The computational results were calibrated with the actual data. The future trend in changes of water discharge into the sea during dry season was discussed by taking into consideration of newly built hydro-engineering projects. The water extraction downstream Datong in dry season before 2000 had a great influence on discharges into the sea in the extremely dry year like 1978-1979. It produced a net decrease of more than 490 m3/s in monthly mean discharges from the Changjiang into the sea. It is expected that the water extraction will continually increase in the coming decades, especially in dry years, when the net decrease in monthly mean water discharge will increase to more than 1000 m3/s and will give a far-reaching effect on the changes of water discharge from the Changjiang into the sea.     

长江中下游晚中生代中基性岩的铅同位素特征:富集地幔的证据

长江中下游东段庐枞、怀宁、繁昌、铜陵和宁芜地区的中基性岩属于碱性系列 ,具有高的U ,Th含量和Th/Pb ,U/Pb比值 ,分别平均为 2 .82× 10 -6,9.5 6× 10 -6和 0 .6 35 ,0 .184。样品的初始铅同位素 (130Ma)组成为 :(2 0 6Pb/ 2 0 4Pb) i=17.6 5～ 18.6 0 ,(2 0 7Pb/ 2 0 4Pb) i=15 .4 2～ 15 .5 0 ,(2 0 8Pb/ 2 0 4Pb) i=37.6 7～ 38.0 4。形成中基性岩的原始岩浆来源于富集的岩石圈地幔 ,具有EMⅠ和EMⅡ ,且以EMⅡ为主的特征。和长江中下游西段黄石地区以及大别地块西南部玄武岩的比较表明 ,长江中下游地区岩石圈地幔高的Th/Pb和U/Pb比值可能和俯冲板片析出流体的交代有关。晚中生代时期 ,华北板块岩石圈地幔以EMⅠ特征为主 ,华南板块岩石圈地幔以EMⅡ特征为主 ,岩石圈地幔性质的区域性分布与印支期扬子板块深俯冲事件密切相关。虽然中国东部新生代玄武岩因岩石圈大规模减薄表现了亏损特征 ,但残留的富集岩石圈地幔在中国东部新生代玄武岩的Pb同位素中仍有所反映     

从江县翁浪金矿床容矿岩石与围岩蚀变及其找矿标志

文章简单介绍了构造蚀变岩型金矿翁浪金矿床的容矿岩石和围岩蚀变特征，指出该类矿床的找矿标志，对进一步寻找此类矿床有一定的意义。     

贵州地区油气勘探反思

文章简单回顾了贵州40余年油气勘探历史，较客观地评价了贵州地区油气地质条件，提出了符合贵州石油地质条件的油气勘探方针，指出贵州油气勘探要想有所突破应注重研究油气成藏机制，勘探重点应放在浅层气藏成藏领域上。     

大功率激电在双阳煤田找矿应用

大功率激电法在双阳煤田找煤的应用中,证实了山河推覆构造的存在;在充分研究工作区的地质、地球物理特征前提下,恰当地选用了方法技术,并正确理解异常的地质、地球物理意义,取得了较好的找煤效果,在Ⅰ号剖面的激电异常上经钻探和坑探证实磨盘山组灰岩下存在质量较好的可采煤层。     

西藏得几蛇绿岩体中玻安岩的地球化学特征及其地质意义

西藏日喀则蛇绿岩是我国发育最好的蛇绿岩之一，目前有关日喀则蛇绿岩形成的构造背景存在多种不同的认识。作者在研究得几蛇绿岩剖面时发现存在玻安岩，从而为日喀则蛇绿岩具有弧前背景提供了直接证据。得几蛇绿岩中玻安岩类样品具有高硅、高镁、低铁的特征，岩石中Zr、Yb和Y的含量也较低，具有明显的玻安岩特征。根据这些岩石的地球化学性质，认为岩石是由早期经历过较高程度的部分熔融的残余在含水条件下再发生部分熔融形成的。得几蛇绿杂岩体部分形成于弧前环境。