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691.
在大湖塘北区钨矿找矿勘查过程中,在总结分析20世纪80年代初针对石英大脉型黑钨矿的普查资料基础上,通过地表填图和老窿编录,发现前人认为的混合黑云母花岗岩与混合白云母花岗岩之间为截然清楚的侵入接触关系,二者之间稳定地分布着一层似伟晶岩壳;由空间关系和区域成矿规律推断似斑状黑云母花岗岩为燕山期侵入于晋宁期黑云母花岗闪长岩之中的成矿母岩。晋宁期黑云母花岗闪长岩为成矿有利围岩,在云英岩化等蚀变过程中释放出形成白钨矿的钙离子。燕山期似斑状黑云母花岗岩岩株与晋宁期黑云母花岗闪长岩岩基之间的侵入接触界面是最主要的成矿构造与成矿结构面,控制了主矿体的位置、形态与产状。在研究区内首次于新元古代花岗闪长岩中发现厚大的白钨矿工业矿体,并根据不同岩块混杂、被长英质充填物胶结等特征识别出热液隐爆角砾岩型矿体。基于对矿区成矿地质条件和矿床地质特征的新认识,修改了针对石英大脉型黑钨矿所做的详查设计,抓住细脉浸染型白钨矿这一主要矿床类型,及时调整了找矿目标和勘查手段,在短时间内实现了赣北地区钨多金属找矿的重大突破。通过与石门寺矿段成矿地质条件类比,预测毗邻的苗尾矿段与太平洞矿区找矿潜力大。  相似文献   
692.
Effects of nitrogen (N) and phosphorus (P) from different sources and at different concentrations on the growth of Levanderina fissa (= Gyrodinium instriatum) were studied in laboratory conditions. The findings might explain the recurrent blooms of this species in Pearl River Estuary, China. Results showed that nutrient limitation significantly inhibited the growth of L. fissa. The values of specific growth rate (μ max) and half-saturation nutrient concentration (K S) were 0.37 divisions/d and 8.49 μmol L?1 for N, and 0.39 divisions/d and 1.99 μmol L?1 for P, respectively. Based on K S values, dissolved inorganic N level in PRE was sufficient to support the high proliferation of L. fissa, while dissolved inorganic P concentration was far lower than the minimum requirement for its effective growth. L. fissa was not able to utilize dissolved organic N (DON) compounds such as urea, amino acids, and uric acid. However, it grew well by using a wide variety of dissolved organic P (DOP) sources like nucleotides, glycerophosphate, and 4-nitrophenylphosphate. The results from this study suggested that the ability in DOP utilization of L. fissa offers this species a competitive advantage in phytoplankton communities. The high level and continuous supply of DIN, enrichment of DOP, together with warm climate and low salinity in the Pearl River Estuary provided a suitable nutrient niche for the growth of L. fissa, and resulted in the recurrent blooms in the estuary.  相似文献   
693.
三种对流层延迟改正模型精度评估   总被引:9,自引:0,他引:9  
利用36个全球分布的IGS站2003全年GPS实测的对流层天顶延迟数据和气象数据,对目前国内外常用的两个对流层延迟改正模型;Hopfield模型、Saastamoinen模型和最近几年发展起来的EGNOS模型的改正精度和适用范围进行评估,指出Hopfield模型在应用中存在的缺陷,EGNOS模型可用作GNSS实时定位和导航的对流层天顶延迟的改正模型.  相似文献   
694.
深海温度变化对太阳活动的响应   总被引:6,自引:1,他引:5  
通过太平洋、大西洋深海温度场谱分析发现,地球海洋温度变化广泛盛行着22年尺度的年代际周期性变化,这种22年变化周期在深层海洋中更为清楚。分析认为,这是地球海洋温度场对太阳磁场周期性变化的响应。世界海洋不同海域深海温度对于太阳磁场磁性22年周期响应的相位存在显著不同,南北大西洋海温变化相位相差115度,即变化趋势接近相反;南北太平洋海温变化相位相差19度,南太平洋变化超前。另外,太阳活动所激发的海温变化的振荡幅度在不同海域也有显著差异,北大西洋海温22年周期振幅为0.07℃,而南大西洋则高达018℃,是北大西洋的2.5倍之多!在太平洋中,北太平洋深海温度22年周期振幅最大,南太平洋次之,赤道中太平洋最小  相似文献   
695.
亚洲中纬度气候主要受两大环流控制,继而划分出受亚洲季风控制季风区和受西风环流控制的西风区。已有研究发现在年代际至千年尺度上,两气候区的湿度演化存在错相位、甚至反相位的现象。文章综述了中更新世以来,多千年至轨道尺度上,两气候区的湿度演化模态的异同,以此深入了解亚洲气候演化的系统性。结果表明:二者的间冰期气候演化的整体趋势存在明显差别,尤其MIS 13以来,二者的演化趋势基本相反。在间冰期的多千年至万年尺度上,二者的气候演化模态呈现非同相位:高精度的释光测年结果显示天山地区的湿度变化滞后于黄土高原地区大概3~5 ka,且该现象在更早的间冰期可重复。在冰期的千年尺度上,两地的湿度演化基本一致,但西风区湿度的波动幅度更大。  相似文献   
696.
The concept and category of wind-sand engineering were discussed in this paper. The development processes of wind-sand engineering in China were reviewed preliminarily. Based on different regional environments, wind-sand engineering research in our country can be divided into two parts: aeolian research of major engineering in desert areas, and aeolian research of major engineering in other areas with special environment. Further than that, aeolian research of major engineering in desert areas can be divided into 4 stages, and aeolian research of major engineering in other areas with special environment mainly focuses on tropical coastal areas, Tibet Plateau and gobi in arid areas. Our research suggests that the development trends of major wind-sand engineering can be summarized as the following aspects. Revealing principles of the wind-sand engineering shelter systems; Evaluating environmental effects of the major wind-sand engineering; Functions of the wind-sand engineering transforming from simple sand prevention to eco-economic types shelter systems; A kind of treatment technology with fabricated materials and equipped construction processes needs to be studied urgently, which can make sand prevention with rapid pace, high efficiency and high quality.  相似文献   
697.
This paper describes the large scale aspects of the seasonal surface heat budget and discusses itsmain forcing mechanisms in the tropical Western Pacific Ocean.The high-resolution generalcirculation model (Semtner & Chervin,1992)used in this study reproduced well the observed upper-layer thermal structure and circulation.It is shown that at least on the average of the study region(20°S-20°N,west boundary-160°E)the semiannual variation is a dominant signal for all heat budgetcomponents and is presumably due to the sun’s passing across the equator twice a year,but that thecomponents have substantial differences in amplitude.The local Ekman divergence in the region doesnot change significantly through the year.As a result,the change in surface heat content is roughlyhalf due to ocean-atmosphere heat exchange and half due to heat advection by remotely forced verti-cal motion.Horizontal currents do not play a significant role directly by advection,because the wat-er which enters the region is not very muc  相似文献   
698.
屈中权  丁有济 《天文学报》1994,35(2):185-194
一种能从观测到的斯托克斯轮廓中提取太阳表面矢量磁场信息的方法在本文中提出,它利用斯托克斯轮廓非线心的极值点处相应参量对波长的导数为零这一数学事实,假设表面附近磁场矢量及热力学参量的变化梯度足够小以致所考虑的极值点的波长位置不随深度改变或此变化呆忽则使得偏振辐射围方程组得到极大的简化;再应用数值方法从此简化方程组中解出辐射表面附近的磁场矢量参数。通过拟合理论轮廓表明该法确实可以得到表面近似的磁场矢量  相似文献   
699.
Environmental changes of oases at southern margin of Tarim Basin,China   总被引:4,自引:1,他引:3  
The Tarim Basin is the largest inland basin in China. Its southern margin is a region with the most fragile eco-environment in China. According to archaeological data, historical documents and paleoclimatic information, great changes have taken place in the eco-environment of the region. Such changes are mainly manifested in the temporal-spatial changes of oases and the expansion of desertification extent, which led to the abandonment of some famous ancient cities and the disappearance of the southern route of the Silk Road. At present, desertification of the region is showing an accelerating tendency. This paper analyzes the distribution and evolution laws of oases in the region, deals with their natural and anthropogenic causes, and points out that before the 20th century evolution of the oases gradually occurred under the influence of natural factors, in particular the climatic aridification, while in the 20th century the desertification and environmental degradation of oases are mainly attributed to human activities under the background of arid climate. To halt further degradation of the environment of the oases great efforts should be made to use water and soil resources rationally, develop advantageous resources and protect the natural oases.  相似文献   
700.
鄂尔多斯块体定边—大罗山段大地电磁结果表明,鄂尔多斯块体内部电性结构简单,成层性好,上地幔第一高导层顶面埋深基本在109km左右,相当平坦,块体内部不存在壳内高导层。而靠近大罗山处,上地幔第一高导层向上隆起,隆起最高处距地表92km,此处测点壳内有电性分层,但由于断裂带的切割使测点之间的壳内分层不易连接,形成不连续层。分析认为该处为深大断裂带,是鄂尔多斯块体的西部边界  相似文献   
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