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431.
浙江景宁鹤溪群斜长角闪岩变质新生锆石特征、离子探针(SHRIMP)U-Pb年龄及地质意义 总被引:10,自引:0,他引:10
景宁鹤溪群斜长角闪岩变质新生锆石特征是粒度均匀(约70μm),晶体结晶和透明度极好,色调一致的淡粉红色,呈金刚光泽.未见裂隙、表面熔蚀、环带和核心构造。离子探针质谱GHRIMPⅡ)的206Pb/238U、207Pb/235U两组年龄在误差范围内基本谐和,206Pb/238U年龄的加权平均值(252±5Ma)为变质新生铁石的结晶年龄。锆石的精确定年(252±5Ma)为丽水—余姚断裂以东地区呈“天窗式”零星出露于中生代火山岩系中的鹤溪群提供了一个变质作用的确切年龄,也为印支运动在丽水—余姚断裂以东地区的存在提供了重要的年代学佐证。 相似文献
432.
433.
Processes of the deposition and vicissitude of Mu Us Desert, China since 150 ka B.P. 总被引:1,自引:0,他引:1
Li Baosheng Jin Heling Lü Haiyan Zhu Yizhi Dong Guangrong Sun Donghuai Zhang Jiashen Gao Quanzhou Yan Mancun 《中国科学D辑(英文版)》1998,41(3):248-254
“Milanggouwan stratigraphical section” named lately takes down 27 cycles of alternately evolutionary histories of desert depositions
in the Mu Us area with the fluviolacustrine facies and palaeosols since 150 ka B. P. Studies show that the sedimentary form
was induced by the growth and decline and confrontation each other between the winter monsoon and the summer monsoon of East
Asia in the past 150 ka.
Project supported by the National Natural Science Foundation of China (Grant No. 49473192). 相似文献
434.
水震波与地震面波的对比研究及其应用 总被引:16,自引:2,他引:14
利用同一地质单元内的水震波与地震面波资料进行对比研究,估算水位对含水层应力庆变的响应“格值”,选取唐山矿井水震波资料,唐山陆河地震台记录的地震面波资料,估算“格值”是9.182×10^-10/cm,即唐山矿井观测含水层垂直应变量为9.182×10^-10/cm时,井水位变化1cm。 相似文献
435.
436.
研究了枞树板铅锌矿区的磁组构特征。结果表明,在变形较弱及无应变标志体的地区,利用磁组构进行构造变形分析是非常有效的,其结果不仅与其它方法的结果大体一致,而且能够获得用其它方法难以获得的认识(如变形类型问题)。据此可以分析控矿构造的变形性质及演化,查明构造控矿的规律。 相似文献
437.
通过对比中国长白山区和朝鲜白头山区新生代火山岩系的层序和同位素年代学资料,首次编制出中朝边境地区新生代火山岩系分布图和新生代火山喷发阶段对比表。其岩石化学和地球化学演化趋势表明,该区新生代火山完全有可能再次喷发。 相似文献
438.
439.
Mission to asteroids and comets has been the hot spot of deep space exploration in the new century. The choice of a suitable target, which involves both scientific value and technical feasibility, becomes a difficult task to accomplish due to limited energy and technology. The aim of this paper is to provide an approach to selecting a target and evaluating accessibility for rendezvous with a Near-Earth Asteroid mission, taking into account scientific value and engineering feasibility. Firstly, according to the orbital characteristics and physical properties of Near-Earth asteroids, we make a summary of some of the most frequent factors influencing the target selection of scientific significance. When selecting the target for a space mission, these factors can be regarded as the scientific motivations. Then in order to avoid the possibility that some high priority targets for science would be discarded due to requiring too high an energy budget by using a classical direct transfer strategy, we calculate the transfer trajectory for rendezvous with candidates by using the planetary swingby technique and the global optimal two-impulse method. Finally, through a comparison between the scientific relevance of each possible target and the corresponding estimate of energy needed for rendezvous missions, the ranking of some candidates is identified. 相似文献
440.
Experiments withLaminaria japonica were conducted in Meidao Bay and Pier Bay, Qingdao, China, Nitrogen-starved plants were fertilized intermittently with 7.1
mM NH4−N solution for 1 hour at 3 day intervals, after which chlorophyll a, fucoxanthin, chlorophyll c and β-carotene contents were
analyzed. Photosynthetic and growth rates of plants and nitrogen content of seawater were determined. their contents of chlorophyll
a, fucoxanthin, chlorophyll c and β-carotene were 1.65, 0.67, 0.33 and 0.06 mg.dm−2 respectively, or 2.46, 2.03, 1.86 and 1.81 times those of the controls. The ratio of fucoxanthin to chlorophyll a in nitrogen-enriched
plants was lower than that of the controls. Normal growth rate of the plants (2 cm·day−1 in length) were reached when the chlorophyll a content exceeded 0.1 mg·g−1 fresh wt., indicating that chlorophyll a content can serve as an indicator of normal growth.
Experimental results show that seawater is regarded as fertile for the normal growth ofLaminaria if the total inorganic nitrogen (including ammonium salt, nitrate and nitrite) content in seawater is about 2 μm, and infertile
if less than 1 μm, in which case fertilizer should be applied.
Contribution No. 1703 from the Institute of Oceanology, Academia Sinica 相似文献