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51.
52.
Geochemical and geochronological studies of the Muong Hum alkaline granitic pluton from the Phan Si Pan Zone,northwest Vietnam: Implications for petrogenesis and tectonic setting
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The Phan Si Pan zone in northwest Vietnam is an important tectonic unit for understanding the geological evolution of the southeast Asian Block. Numerous late Permian A‐type granites outcrop in this zone. In this study, new geochemical and geochronological data derived from the Muong Hum alkaline granitic pluton in the Phan Si Pan zone were investigated for its petrogenesis and tectonic setting. Zircon U–Pb analyses of three samples yielded 206Pb/238U ages of (251.1 ±3.5) Ma, (251.2 ±3.8) Ma, and (253.9 ±1.5) Ma, respectively, coinciding with the ages of the acid member of magma from Emeishan large igneous province, southwest China. The Muong Hum granite has 10 000 × Ga/Al and A/CNK values of 4.70–4.93 and 0.87–0.90, respectively, as well as negative Eu anomalies. It shows significant depletion of Ba, Sr, Ti, and P, similar to features of A‐type granite. Zircons have positive εHf(t) values (+1.9 to +8.6) and Hf model ages (TDM1) of 595–846 Ma, originating a mantle source. Compared with the Panzhihua A‐type granite of the southwest China domain and other A‐type plutons of the Phan Si Pan zone, including Ye Yen Sun, Phu Sa Phin, Nam Xe, Tam Duong Phan Si Pan, and Taihe, the geochemical characteristics and zircon Hf isotopic compositions of the Muong Hum granite demonstrate an affinity of mantle magma. It is believed that the Phan Si Pan zone is an important part of Emeishan large igneous province. It was reworked by the Cenozoic Aillaoshan‐Red River shear fault to its present location. 相似文献
53.
含钙聚硅氯化铁铝的表征与絮凝研究 总被引:3,自引:3,他引:0
用X粉晶衍射、红外光谱对以Ca(OH)2为碱化剂合成的含硅聚合氯化铝铁(PAFSCCa)、比较样聚合氯化铝铁(PAFCCa)、及其合成前体聚合氯化铝(PACCa)、聚合氯化铁(PFCCa)的低温干燥样进行了表征。XRD衍射结果显示.PAFSCCa中有Ca-Si-O-Al化合物存在,加热可促进Ca-Si-O-Al化合物的结晶和生长。Si/Al摩尔比在1:1时有利于Ca(Ⅱ)、Fe(Ⅲ)、Al(Ⅲ)与OH^-之间的共聚,无论是在加热、常温合成条件下,PAFSCCa中均有短程有序而长程无序的Ca(Ⅱ)、Fe(Ⅲ)、Al(Ⅲ)羟合物大量存在。Ca-Si-O-Al化合物的存在会抑制Ca-O-Fe之间的键合,破坏Fe(Ⅲ)羟合物的结晶,但促进低聚合度Fe(Ⅲ)羟合物的生成。红外光谱证实,PAFSCCa中硅铝之间通过Si-O-Al氧桥的键合程度随Si/Al摩尔比的增加而上升。在Si/Al摩尔比1:1及加热合成条件下,硅铝之间通过Si-O-Al氧桥的键合程度最高。絮凝实验证实PAFSCCa水解形成絮体时,含硅高的样品其絮体更大,絮凝效果好,硅铝共聚物对抑制微絮体再稳定的贡献大。 相似文献
54.
Solar light, seawater temperature, and nutrients, which one is more important in affecting phytoplankton growth? 总被引:2,自引:1,他引:1
Based on research results on the impacts of solar light, seawater temperature, and nutrient available to phytoplankton growth
and changes in phytoplankton physiology and assemblage, we discussed the order of influence of these factors. By clarifying
the mechanisms and processes of the impacts by these factors, we have determined the rising order of the importance as solar
light, seawater temperature, and nutrient silicon (Si). Therefore, for human interests in sustaining economic development,
the first thing to be considered is the input of nutrient Si into the ocean, followed by seawater temperature change. 相似文献
55.
The seasonal dynamics of nutrient ratios and abundance of phytoplankton cells from the central (CB) and western (WB) Bay of Bengal (BOB) were studied during the fall intermonsoon (FIM; September-October 2002) and spring intermonsoon (SpIM; April-May 2003). The nutrient molar ratios of macronutrients such as nitrate to phosphate (N:P), nitrate to silicate (N:Si) and silicate to phosphate (Si:P) in the top 120m were calculated for both FIM and SpIM. During both the seasons, the N:P ratios along the CB and WB were lower than 16, indicating nitrate deficiency. Whereas, along both transects the N:Si ratio was <1 and Si:P >3 in the top 20 and 40m during FIM and SpIM, respectively, indicating Si enrichment. Relatively greater nutrient concentrations along the WB than the CB appear to contribute to higher phytoplankton abundance. The preponderance of diatoms in the Bay could be attributed to rapid utilization of available nutrients in particular during FIM thus resulting in low N:Si ratios in the water column. Among diatoms, pennales were predominantly controlled by nutrients and their ratios. While, apart from nutrients, physical stratification, light and eddies also seem to influence the distribution and abundance of centrales. 相似文献
56.
1 INTRODUCTION In marine waters, water temperature and nutrient Si control the temporal and spatial variation of the phytoplankton growth (Yang et al., 2006). The effect of nutrient Si and water temperature on the mecha- nism of phytoplankton growth has p… 相似文献
57.
Maryna Strokal He Yang Yinchen Zhang Carolien Kroeze Lili Li Shengji Luan Huanzhi Wang Shunshun Yang Yisheng Zhang 《Marine pollution bulletin》2014
We analyzed the potential for eutrophication in major seas around China: the Bohai Gulf, Yellow Sea and South China Sea. We model the riverine inputs of nitrogen (N), phosphorus (P) and silica (Si) to coastal seas from 1970 to 2050. Between 1970 and 2000 dissolved N and P inputs to the three seas increased by a factor of 2–5. In contrast, inputs of particulate N and P and dissolved Si, decreased due to damming of rivers. Between 2000 and 2050, the total N and P inputs increase further by 30–200%. Sewage is the dominant source of dissolved N and P in the Bohai Gulf, while agriculture is the primary source in the other seas. In the future, the ratios of Si to N and P decrease, which increases the risk of harmful algal blooms. Sewage treatment may reduce this risk in the Bohai Gulf, and agricultural management in the other seas. 相似文献
58.
59.
Nikolay P. Laverov Vasily I. Velichkin Ai Fujiwara Naotatsu Shikazono Alexey P. Aleshin Enver E. Asadulin Vyacheslav N. Golubev Tatiana L. Krylova Alexander A. Pek Igor V. Chernyshev 《Resource Geology》2009,59(4):342-358
It has been shown that the main uranium ore mineral, pitchblende (uranium dioxide), is a natural analog of synthetic uraninite (also uranium dioxide), which constitutes 96% of spent nuclear fuel (SNF). Geochronological studies of the U‐Pb isotope systems in unaltered pitchblende from the orebodies reveal that these systems remained completely closed over the entire period (approximately 135 Ma) since the formation of the deposits. The bulk of the primary uranium ores within the Streltsovskoye ore field was influenced to various degrees by post‐ore hydrothermal solutions that led to pitchblende spherulites being replaced by pseudomorphs of an amorphous phase with a U‐Si composition; this phase also re‐precipitated in veinlets proximal to the pitchblende pseudomorphs. A technique specially developed by the authors was used to carry out quantitative counts of the abundance of uranium minerals by calculating the uranium mass balance in one of the orebodies subjected to hydrothermal alteration. The calculations reveal minimal uranium loss from the orebody. Uranium liberated in the process of the pseudomorphic replacement of pitchblende was immediately fixed, in situ, in the newly formed coffinite‐like amorphous U‐Si phase as a result of the development of an efficient geochemical barrier that prevented the long‐distance migration of uranium. In assessing the long‐term safety of underground SNF repositories, the results of the present study give us confidence that SNF uraninite, in terms of the preservation of its integrity as a mineral phase, provides for the reliable long‐term isolation of uranium, transuranium elements, and fission products that are “sealed” in the uraninite matrix. In the case of the mineral transformation of the uraninite matrix by hydrothermal solutions, the liberated uranium would be efficiently immobilized by the newly formed amorphous U‐Si phase. 相似文献
60.
ABSTRACTIn this paper, a mid- to long-term runoff forecast model is developed using an ideal point fuzzy neural network–Markov (NFNN-MKV) hybrid algorithm to improve the forecasting precision. Combining the advantages of the new fuzzy neural network and the Markov prediction model, this model can solve the problem of stationary or volatile strong random processes. Defined error statistics algorithms are used to evaluate the performance of models. A runoff prediction for the Si Quan Reservoir is made by utilizing the modelling method and the historical runoff data, with a comprehensive consideration of various runoff-impacting factors such as rainfall. Compared with the traditional fuzzy neural networks and Markov prediction models, the results show that the NFNN-MKV hybrid algorithm has good performance in faster convergence, better forecasting accuracy and significant improvement of neural network generalization. The absolute percentage error of the NFNN-MKV hybrid algorithm is less than 7.0%, MSE is less than 3.9, and qualification rate reaches 100%. For further comparison of the proposed model, the NFNN-MKV model is employed to estimate (training and testing for 120-month-ahead prediction) and predict river discharge for 156 months at Weijiabao on the Weihe River in China. Comparisons among the results of the NFNN-MKV model, the WNN model and the SVR model indicate that the NFNN-MKV model is able to significantly increase prediction accuracy.
Editor D. Koutsoyiannis; Associate editor Y. Gyasi-Agyei 相似文献