滇黔桂三角区微细浸染型金矿床成矿热液一种可能的演化途径:年代学证据   总被引：24，自引：1，他引：24  

胡瑞忠  苏文超  毕献武  李泽琴 《矿物学报》1995,(2)

本文主要根据年代学资料和金活化迁移的地球化学属性，探讨了滇黔桂三角区微细浸染型金矿床成矿热液的演化途径。多种定年方法揭示，该区金成矿初始流体（古流体）的年龄为260Ma左右；金成矿年龄约为140～75Ma。考虑到该区燕山晚期岩浆岩富含Cl，本文认为古流体（260～140Ma）向成矿流体（140～75Ma）的转化，可能主要是通过燕山晚期岩浆活动产生的富氯流体加入原已存在的贫氯古流体，从而使这种新的混合流体具有浸取金的能力来实现的。  相似文献   

新疆北天山晚古生代洋盆演化与推覆构造   总被引：5，自引：4，他引：5  

李向东 《新疆地质》1993,(3)

通过实地考察并综合区域及深部物探资料,研究了北天山逆冲推覆系统的构造样式、结构特征和组合方式;认为北天山晚古代洋盆为板内地壳扩张活动形成的裂陷构造产物,存在时限短暂、对生物群迁移基本没有阻隔作用,不应具有分隔岩石圈板块的大地构造意义。  相似文献   

成都平原秋季农业气候特征的分析利用     

张碧  胡毅  徐精文 《成都信息工程学院学报》1999,(4):9

对成都平原9个代表点的气候资料进行聚类,然后分析3种类型农业气候的光热水特征,最后分析了这些特征对农业生产的影响  相似文献   

2018年10月乌鲁木齐暴雪过程锋面分析     

李娜  李如琦  秦贺  于碧馨  赵凤环 《沙漠与绿洲气象(新疆气象)》2020,14(5):36-43

利用地面常规观测、NCEP/NCAR0.25°×0.25°再分析及风廓线雷达等资料，诊断分析了2018年10月17—18日乌鲁木齐极端暴雪天气过程的锋面特征。结果表明：在欧洲高压脊衰退，中亚长波槽分段东移的背景下，天山北坡强烈锋生并持续近30小时，此次锋生是热力和动力共同作用的，天山附近锋面呈带状准垂直分布，动力锋生激发的次级环流使垂直运动维持发展，为大暴雪提供动力条件； 400～600 hPa西南和地面～850 hpa西北路径输送的水汽，在600～800 hPa强烈辐合，为乌鲁木齐暴雪提供充沛水汽。风廓线雷达监测资料水平风向风速的垂直变化、Cn2能够反映锋生和水汽的演变特征，也从观测事实上证实了锋面对动力抬升及水汽辐合的重要作用。  相似文献   

Oscillator strengths for 2pnd−2pn′f transitions of Ci and identifications in the infrared solar photospheric spectrum (1 ≤ λ ≤ 3μ)     

E. Biémont 《Solar physics》1973,32(1):117-129

  相似文献   

利用抽水试验资料确定水文地质参数   总被引：3，自引：0，他引：3  

于传宁  宗先国  张利红  刘向东 《地下水》2006,28(1):44-45,50

本文根据抽水试验取得的数据,分别采用稳定流公式法、降深-距离配线法、漏斗疏干法和直线解析法四种方法,计算了黄河侧渗补给浅层地下水的各项水文地质参数,最后对试验成果的合理性进行了分析评价并确定了各项水文地质参数.  相似文献   

Historical trophic evolutions and their ecological responses from shallow lakes in the middle and lower reaches of the Yangtze River: Case studies on Longgan Lake and Taibai Lake     

YANG Xiangdong  SHEN Ji  DONG Xuhui  LIU Enfeng  WANG Sumin 《中国科学D辑(英文版)》2006,49(Z1)

The evolutions of diatom floras and the total phosphorous (TP) concentrations in the historical period were reconstructed for two lakes, Longgan and Taibai in the middle Yangtze River,based on high resolutional fossil diatom study from two sediment cores and an established regional diatom-TP transfer function. The TP concentration in Longgan Lake changed slightly in the range of 36-62 μg/L and kept its middle trophic level in the past 200 years. The changes of diatom assemblages reflect a macrophyte-dominated history of the lake. During the nineteenth century, the lake TP concentration increased comparatively, corresponding to the increase in abundance of benthic diatoms. The progressive increase of epiphytic diatoms since the onset of the twentieth century indicates the development of aquatic plants, coinciding with the twice drops of water TP level. The TP concentration in Taibai Lake kept a stable status about 50 μg/L before 1953 AD, while diatoms dominated by facultative planktonic Aulacoseira granulata shifted quickly to epiphytic diatom species, indicating a rapid expansion of aquatic vegetation. During 1953-1970 AD, the coverage of aquatic plants decreased greatly inferred by the low abundance of epiphytic diatoms as well as declined planktonic types, and the reconstructed TP concentration shows an obvious rising trend firstly, suggesting the beginning of the lake eutrophication. The lake was in the eutrophic condition after 1970, coinciding with the successive increase of planktonic diatoms. The comparison of the two lakes suggests the internal adjustment and purification function of aquatic plants for nutrients in water. The discrepancy of TP trends in the two lakes after 1960 reflects two different patterns of lake environmental response to human disturbance. Sediments in Taibai Lake clearly recorded the process of lake ecological transformation from the macrophyte-dominated stage to the algae-dominated stage. The limits of TP concentration (68-118 μg/L) in the transitional state can be considered as the critical value between the two stable ecosystems. Further work will be necessary to provide more evidence from the sediments in more eutrophic lakes for the primary inference. The reconstructive TP level and the inference of aquatic plants from fossil diatoms in different lakes, as well as their comparison provide a scientific basis for ecological restoration of eutrophic lakes in research regions.  相似文献   

Study on the nutrient evolution and its controlling factors of Longgan Lake for the last 200 years     

LIU Jian  YANG Xiangdong  WANG Sumin 《中国科学D辑(英文版)》2006,49(Z1)

Based on the total phosphorous (TP) concentration in sediment core, the TP concentration in lake water quantitatively reconstructed from fossil diatoms and diatom-TP transfer function in the Longgan Lake during the last 200 years, the temperature and precipitation data from meteorological observation for the last 50 years, the temperatures and precipitation sequences of climate simulation for the last 200 years, as well as the amount of the agricultural phosphate fertilizer in Longgan area for nearly 50 years, the characteristic and the law of the nutrient status evolution were analyzed, and the influence of the climatic factor, the anthropologic factor and the aquatic biology factor on the nutrient status evolution and its mechanism were discussed for the Longgan Lake during the last 200 years. The results showed that, in the nearly 200 years, the TP concentration in the sediment core of the Longgan Lake gradually increased, its range of variation was situated between 330-580 mg/kg, the mean value was 388 mg/kg, a nearly 30-year vibration adjustment period existed at 1950 around. The TP concentration in lake water changed in a different way. Before 1950, it had a slow increasing tendency in fluctuated background, to 1950 around it reached up to the mean value (52.18μg/L), and vibrated and adjusted around the mean value, then it fast declined, its change range was situated between 37.75-62.33μg/L. The analyses indicated that, in the centennial time scale, the climate change was the main controlling factor, while in the decadal time scale in the recent 50 years, human activities were the leading factors for the nutrient status evolution of the Longgan Lake. 60% of the variability of the TP concentration in the sediments and 57% of that in lake water were due to human activities. The differentiation between phosphorus concentration in the sediment and in the lake water reflected the response processes and the adjustment abilities of the lake aquatic ecosystems to the lake nutrient level, implying the maintenance and the destruction of the balances between the algae and the aquatic plants, as well as the corresponding accumulating characteristics of the phosphorus.  相似文献   

国内外气溶胶观测网络发展进展及相关科学计划   总被引：16，自引：6，他引：16  

延昊  矫梅燕  毕宝贵  刘桂清 《气象科学》2006,26(1):110-117

气溶胶是气候变化研究中的一个极大的不确定性因素,国内外在此方面开展了大量的观测和科学研究。本文首先对当前全球两大气溶胶观测网络,世界气象组织(WMO)的全球大气观测计划(GAW)和气溶胶自动观测网(AERONET)的组织、规模、设备、数据和气溶胶网络的规范作了介绍,并对近年来国际上的重大气溶胶科学计划的目标、实验方法、步骤作了介绍,说明观测网络的重要性。在此基础上对中国气溶胶观测网络的地位做了分析,并指出其在正在开展的中国气溶胶科学研究中的重要性。  相似文献   

Constructing temporal and spatial water vapor figures by GPS remote sensing along slant rays     

MAO Hui    MAO JieTai  BI YanMeng  LI ChengCai? & LIU XiaoYang Department of Atmospheric Sciences  School of Physics  Peking University  Beijing  China  Shenzhen Meteorological Bureau  Shenzhen  China 《中国科学D辑(英文版)》2007,50(2):296-305

A Global Positioning System (GPS) receiver can generally track 5-7 rays from GPS satellites at any moment, and water vapor along these ray paths (slant-path water vapor, SWV) may be retrieved using the methods developed in recent years. This paper suggests two new parameters-absolute vertical SWV (VSWV) and relative VSWV derived from SWV, and their temporal and spatial figures can reflect the heterogeneous distribution and variation of water vapor field. This approach has been applied to the weather diagnoses in a severe storm event in Beijing during July 2004, and it is concluded that the temporal and spatial figures of absolute VSWV and relative VSWV can be useful in monitoring the evolution of water vapor field and be potential in better understanding the precipitation process.  相似文献