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991.
Skarn-type tungsten mineralization associated with the Caledonian (Silurian) Niutangjie granite,northern Guangxi,China 总被引:1,自引:0,他引:1
YANG Zhen WANG RuCheng ZHANG WenLan CHU ZhuYin CHEN Jun ZHU JinChu ZHANG RongQing 《中国科学:地球科学(英文版)》2014,57(7):1551-1566
The Niutangjie tungsten deposit is a bedded skarn-type scheelite deposit and is located at the junction between Ziyuan and Xingan counties in the north of Guangxi,China.The deposit is genetically related to a fine-grained two-mica granite within the orefield.Zircon LA-ICP-MS U-Pb dating of the granite yielded a Silurian(Caledonian)age of 421.8±2.4 Ma,which is contemporaneous with the adjacent Yuechengling batholith.Mineralization within the skarn is associated with a quartz,garnet,and diopside gangue,and scheelite is present in a number of different mineral assemblages,such as quartz-scheelite and quartz-sulfide-scheelite;these assemblages correspond to oxide and sulfide stages of mineralization.Sm-Nd isotope analysis of scheelite yielded an isochron age of 421±24 Ma.Although the uncertainty on this date is high,this age suggests that the scheelite mineralization formed during the Late Caledonian,at a similar time to the emplacement of the Niutangjie granite.Zircons within the granite have?Hf(t)values and Hf two-stage model ages of?6.5 to?11.6,and 1.79 to 2.11 Ga,respectively.These data suggest that the magma that formed the granite was derived from Mesoproterozoic crustal materials.Scheelite?Nd(t)values range from?13.06 to?13.26,also indicative of derivation from ancient crustal materials.Recent research has identified Caledonian magmatism in the western Nanling Range,indicating that this magmatism may be the source of contemporaneous tungsten mineralization. 相似文献
992.
Li Zongkai Pan Yunxian Zhou Chaofu Jiang Weimei Tang Shibao Zhu Zengwang 《Acta Meteorologica Sinica》1988,2(2):196-204
The fumigation during the mountain-valley wind shift has been first identified as a special type of pol-lutant diffusion using the monitoring measurements of Dukou,Southwest Sichuan,China.Such a pheno-menon occurs frequently all year around but summer,particularly in winter months.A new model for thefumigation during the mountain-valley wind shift period is developed that allows satisfactory explanation ofthe fact.Analyses indicate that the model can more accurately predict not only the high concentration ofPollutants but the time and locality of the occurrence as well.The ground concentration of SO_2 during fumigation is several times up to over a decade higher thanthe daily mean for the whole region,one of the main contamination processes that affect the air quality ofthe city.The medel analyses provide a basis for more effective prediction of the quality and precautionstudy against the disaster. 相似文献
993.
994.
LI Jie HU Jin-ming DENG Wei HUANG Sheng-li JIA Hai-feng ZHU Chun-ling LUO Huai-xiu 《山地科学学报》2013,10(4):553-563
Mountains and plateaus in Southwest China contain many subalpine and alpine wetlands, with significant hydroecological functions. But ungauged or poorly gauged conditions limit the study and understanding of hydrological regimes of these wetland types. This study selects an ungauged subalpine wetland-Napahai in Northwest Yunnan, China-as a case for developing a practical approach to revealing its storage-area relationship of open water. A Trimble R8 GNSS (Global Navigation Satellites Systems) RTK (Real-time Kinematic system) and sonar fathometer were used to survey fine-resolution elevation data and generate a digital elevation model of the Napahai Wetland. Forty-four Landsat images from 1987 to 2011 were collected, and the Normalized Difference Water Index was used to classify open water features in the area. The area of open water in Napahai was calculated for each phase. With these data and a developed conceptual model, the storage of open water for each phase was estimated using ArcGIS tools. Both storage and area of open water showed significant intra-annual and inter-annual variations. In the rainy season, the monthly change of average storage of open water in Napahai showed about 1-2 months lag behind mean monthly rainfall. The storage-area relationship of open water was well fit by a power function equation (R 2 ≈0.91, n=44). This study indicates that if detailedelevations are available for similarly ungauged subalpine wetlands in Southwest China, researchers can use this practical approach to estimate multi- temporal areas and storages and reveal the storage-area relationship of open water in the wetlands. The study provided valuable information of this case wetland for optimizing its hydro-ecological managements and a new method to wetland researchers and managers for the hydrological study of similarly ungauged wetland complex. 相似文献
995.
996.
通用地震数据采集器EDAS-24GN引入一种新型的数据传输方式,通过AT91SAM9263CPU板带有的同步串行控制器进行数据传输,可以有效解决前一种方式存在的问题.经过实验验证,新型的数据传输方式在每秒传输50 kB数据时,引起的中断次数只有十几次,有效提高了CPU处理效率,且不存在数据丢失现象. 相似文献
997.
Both land use/land cover change (LUCC) and the effects of nutrients cycles on terrestrial ecosystems and biodiversity are key environmental problems in the 21st century (Yang etal., 2002; Li, 1996; Bai and Bai, 1998). Land cover change is the accumulated result of land use, which includes three types, i.e., deterioration, transition and amelioration of land cover (Cai, 2001). The nutrient cycle is the main functional process to maintain stability and production of an ecosystem. Land cover … 相似文献
998.
Swe Hlaing Htar Wei Zhu Jingyu Huang Philip Nti Nkrumah 《Environmental Earth Sciences》2013,70(7):3185-3195
The experiment was conducted to ascertain net production and consumption rates of 15NH4 + and 15NO3 ? for water and sediment in a wetland. This was done using 15N isotope pool dilution methodology under ambient and elevated atmospheric CO2 concentrations in experimental riparian wetlands to obtain the gross N transformation rates. The 15N budget for sediment was also estimated. The results suggested that the differences in high proportion of 15N concentration in the overlying water body under elevated CO2 could be attributed to the low production and high consumption rates of 15NH4 + in sediment. The elevated CO2 effect on production and consumption of NH4 + decreased by 144 % (P = 0.014) and increased by 153 % (P = 0.009), respectively. Thereby, 15NH4 + production rates are negatively related with 15NO3 ? consumption rates and this accounted for the decreases in net 15NO3 ? consumption under CO2 enrichment in the wetland sediment by 11 % (P = 0.528). Therefore, 15NO3 ? production and consumption rates may strongly depend on NH4 + production. Inorganic 15N and total 15N exported from sediment to overlying water body by the effect of CO2 were 41 % (P = 0.071) and 18 % (P = 0.000), respectively. Therefore, low net 15NH4 + production and high 15NH4 + consumption rates under elevated CO2 may partly explain the significant reduction of N from the sediment. 相似文献
999.
Cenozoic volcanic rocks widespread in eastern China constitute an important part of the circum-Pacific volcanic belt.This paper presents more than 150K-Ar dates and a great deal of petrochemical analysis data from the Cenozoic volcanic rocks distributed in Tengchong,China‘s southeast coast,Shandong,Hebei,Nei Monggol and Northeast China.An integrated study shows that ubiquitous but uneven volcanic activities prevailed from the Eogene to the Holocene,characterized as being multi-eqisodic and multicycled.For example,in the Paleocene(67-58Ma),Eocene(57-37.5Ma),Miocene(22-18,16-19Ma),Pliocene(8-3Ma),and Early Pleistocene-Middle Pleistocene(1.2-0.5Ma) there were upsurges of volcanism,while in the Oligocene there was a repose period.In space,the older Eogene volcanic rocks are distributed within the region or in the central part of the NE-NNE-striking fault depression,while the younger Neogene and Quaternary volcanic rocks are distributed in the eastern and western parts.Petrologically,they belong essentially to tholeiite-series and alkali-series basalts,with alkalinity in the rocks increasing from old to youg.The above regularities are controlled by both global plate movement and regional inherent tectonic pattern. 相似文献
1000.
Contribution of climatic and technological factors to crop yield: empirical evidence from late paddy rice in Hunan Province,China 总被引:1,自引:1,他引:1
Zhu Wang Tao Ye Jun Wang Zhuo Cheng Peijun Shi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):2019-2030
Climatic and technological factors are two remarkable aspects that are thought to contribute to crop yield change. However, the most significant factors and their contribution rate remain debatable. Selecting Hunan Province, which is one of the largest paddy rice producing regions in China as the research area, the marginal contributions of climatic and technological factors to late paddy yield change are estimated using a county-level panel data regression model with explicit consideration of technological variables during 2000–2011. The results indicate that the mean daily temperature and adoption rate of hybrid rice have significant positive impacts on late paddy rice yield. During the research period, 1 °C temperature increase will cause 7.220 t/km2 increase in late paddy rice yield, and 1 % increase in the adoption rate of hybrid rice will cause 0.212 t/km2 increase. Climatic factors, especially their annual variability, exhibit a stronger overall linkage to changes in late paddy rice yield in the study area compared with the technological factors. Climatic factors accounted for 67.645 and 74.585 % of the trend and variability in late paddy rice yield, respectively. The results of this study can provide valuable information for stakeholders to adjust the input on late paddy rice production and better adapt to the effect of climate change. 相似文献