云蒙山变质核杂岩抬升过程中伸展拆离和岩浆底辟联合作用的证据     

张家声  C.W.Passchier  J.Konopasek  牛向龙  黄雄南 《地学前缘》2007,14(6):26-39

北京地区云蒙山变质核杂岩在白垩纪阶段抬升的早期,伴随着沿四合堂剪切带由北向南的拆离滑脱和大型花岗闪长岩的垂向侵位,晚期变形发生在花岗闪长岩岩基周边及其邻近围岩中,形成云蒙山剪切带,并伴随大量同构造的花岗岩和伟晶岩岩脉灌入。剪切带中所有的岩脉都随时间发生了不同程度的变形,较老的岩脉形成紧闭的圆柱状褶皱,枢纽与剪切带的线理和面理接近平行。岩脉与剪切带中L-S组构的平行化作用主要是由于这种转动的结果。岩脉的成分和长英指数随它们的变形程度发生变化,说明持续的岩浆分异作用与韧性剪切变形是同时发生的。云蒙山剪切带由岩浆底辟引起的上盘岩石重力所驱动,并不断得到同构造侵位岩脉的补充,起到存储和不断改造侵位岩脉的作用。早期伸展体制下形成的四合堂剪切带局部遭受云蒙山剪切带的改造或复合。该地区的岩石、构造和同构造岩脉的变形几何学和运动学证据表明,太古宙结晶基底的抬升是下部岩浆底辟与上部地壳伸展拆离共同作用的结果。  相似文献   

升温过程中盐岩动力特性实验研究   总被引：2，自引：0，他引：2  

陈剑文  杨春和  冒海军 《岩土力学》2007,28(2):231-236

利用超声波技术对盐岩进行了升温过程中(无侧压,温度为20～270 ℃) 的动力学测试,分析了超声波波速、动弹性常数以及温度所导致的损伤变化规律。试验结果表明,随着温度升高,盐岩的超声波波速、动弹性模量和泊松比都有不同程度地降低,且呈现一定的规律性。试验过程中所观察到的现象和理论分析说明,盐岩的热损伤主要由矿物失水和晶间裂纹所导致,损伤变量和平行轴向相对裂纹密度随温度的升高而增大,但速度逐渐变缓,试验中未观察到温度对盐岩损伤的门阀值以及损伤愈合现象。  相似文献   

长江口盐沼土壤有机质更新特征的滩面趋势   总被引：1，自引：0，他引：1  

陈庆强  谷河泉  周菊珍  孟翊  胡克林 《地理学报(英文版)》2007,17(1):101-113

Characteristics and tidal flat trends of soil organic matter （SOM） turnover were studied for the Chongmingdongtan Salt Marsh in the Yangtze River estuary, based on analyses of stable carbon isotope composition （δ^13C）, grain sizes and contents of particulate organic carbon （POC）, total nitrogen （TN） and inorganic carbon （TIC） for three cores excavated from high tidal flat, middle tidal flat and bare flat. Results demonstrate that correlations between soil POC contents and δ^13C values of the salt marsh cores were similar to those between soil organic carbon （SOC） contents and δ^13C values of the upper soil layers of mountainous soil profiles with different altitudes. SOM of salt marsh was generally younger than 100 years, and originated mainly from topsoil erosions in catchments of the Yangtze River. Correlations of TN content with C/N ratio, POC content with TIC content and POC content with δ^13C values for the cores suggest that turnover degrees of SOM from the salt marsh are overall low, and trends of SOM turnover are clear from the bare flat to the high tidal flat. Bare flat samples show characteristics of original sediments, with minor SOM turnover. Turnover processes of SOM have occurred and are discernable in the high and middle tidal flats, and the mixing degrees of SOM compartments with different turnover rates increase with evolution of the muddy tidal flat. The exclusive strata structure of alternate muddy laminae and silty laminae originated from dynamic depositional processes on muddy tidal flat was a great obstacle to vertical migration of dissolved materials, and SOM turnover was then constrained. The muddy tidal flat processes exerted direct influences on sequestration and turnover of SOM in the salt marsh, and had great constraints on the spatial and temporal characteristics of SOM turnover of the Chongmingdongtan Salt Marsh in the Yangtze River estuary.  相似文献   

Mantle diapir-induced arc volcanism: The Ueno Basalts, Nomugi-Toge and Hida volcanic suites, central Japan   总被引：2，自引：0，他引：2  

Jun-Ichi Kimura  & Takeyoshi Yoshida 《Island Arc》1999,8(2):304-322

Stratigraphic and geochronological data show that the late Cenozoic Ueno Basalts and related Nomugi-Toge and Hida volcanic suites of the Norikura Volcanic Chain, Japan, were active for ~ 1 million years. Temporal and spatial variations of the volcanic activity and chemistry of the volcanic products suggest that it was induced by a common mantle diapir. The Ueno Basalts are small monogenetic volcanoes scattered over an area 50 km in diameter, and comprise a small volcanic province. The Ueno Basalts are almost all subalkalic basalt to basaltic andesite, erupted through the late Pliocene to the earliest Pleistocene (2.7–1.5 Ma). Andesite to dacite of the Nomugi-Toge volcanic rocks were concurrently active in the back arc side, and two eruption stages (2.6–2.2 and 2.1–1.7 Ma) are recognizable. Two voluminous dacite and rhyolite ignimbrites, the Hida Volcanic Rocks, were erupted deeper in the back-arc region, at ca 1.75 and 1.7 Ma. Both the Nomugi-Toge and Hida suites are also subalkalic, except for the last ignimbrite. In the Ueno Basalts, alkali olivine basalt was erupted in the earliest stage, and was followed by subalkalic basalt, showing that the magma segregation depth ascended with time. This coincided with uplift of the volcanic province and with quasi-concentric expansion of the eruption centers, suggesting that an upwelling mantle diapir was the cause of the volcanism. The Nomugi-Toge andesite–dacite lavas and the Hida dacite and rhyolite ignimbrites are considered to have originated from the same mantle diapir, because of their close proximity to the Ueno Basalts and their near-contemporaneous activity. Mantle diapirs have a significant role in the origin of subalkalic volcanic rocks in the island arcs.  相似文献   

土壤水研究进展与评述   总被引：98，自引：7，他引：91       下载免费PDF全文

雷志栋  胡和平  杨诗秀 《水科学进展》1999,10(3):311-318

土壤水是联系地表水与地下水的纽带,在水资源的形成、转化及消耗过程中有重要作用,与农业、水文、环境等领域都有密切联系。所以土壤水研究越来越引起人们的重视,有了长足的进步。目前,土壤水研究走向多学科的交叉,如水热盐的耦合运移,冻结土壤中水分的运移,土壤-植物-大气连续体中的水热运移等。土壤水运动机理研究也更加深入,如优先流、土壤水参数的测定及确定、土壤水参数的空间变异性等。土壤水研究的数值模拟方法也有一些突破,如有限解析法、特征有限元法、交替方向有限元法等。土壤水研究的应用也更加广泛,如用于水资源评价、土壤水分与作物的关系、水环境评价等。  相似文献   

内蒙古伊克昭盟地区盐湖生物地层与古气候研究   总被引：1，自引：0，他引：1  

刘振敏 《化工矿产地质》1999,21(1):40-46

内蒙古伊克昭盟地区自全新世以来,湖沼发育,随气候的波动,大部分已演化成为盐湖。各类反映与气候有关的信息均保留在盐湖沉积物中。通过对其中具有代表性的4个盐湖5个钻孔剖面有关生物化石的鉴定与分析,发现介形类化石4个属种,硅藻39个属种和较多的植物种子、草茎及虫管化石。在含有抱粉层位的样品中分析出木本、草本及蕨类孢子等化石41个属种。通过对各钻孔剖面生物地层组合特征综合的分析表明,该区自全新世以来,其气候波动特点为暖湿→冷湿→温干→温凉湿润→凉干的气候波动格局。  相似文献   

N₂, N₂O and O₂Profiles in a Tagus Estuary Salt Marsh     

P. Cartaxana  D. Lloyd 《Estuarine, Coastal and Shelf Science》1999,48(6):751

Vertical gas profiles of N₂, N₂O and O₂were obtained in intact sediment cores from a Tagus estuary salt marsh using membrane inlet mass spectrometry. This technique allows direct measurements of dissolved gas concentrations with minimal disturbance. O₂concentrations decreased sharply with depth, becoming undetectable below 14mm. Denitrification products (N₂and N₂O) occurred in the surface layer of the sediment where O₂was present. Diffusion of N₂and N₂O from the anaerobic zone, denitrification in anaerobic microsites and aerobic denitrification are possible explanations for this observation. N₂was the sole product of denitrification in control sediment cores probably because of the great demand for electron acceptors in this sediment. The addition of NO₃ ⁻ and CH₃CO₂ ⁻ increased the concentrations of N₂and N₂O in the sediment. Significantly higher concentrations in treated cores occurred between 1·5 and 2·0cm for N₂and between 0·5 and 1·5cm for N₂O. The peak in N₂concentration occurred in the anaerobic zone of the sediment, close to the aerobic–anaerobic interface while the peak in N₂O concentration occurred above this interface where concentrations of O₂were approximately 10μM. This is indicative that, in this sediment, production of N₂O is less sensitive to the presence of O₂than reduction of N₂O to N₂.  相似文献   

雷氏盐特异沉淀法提取和分离海藻中的季铵化合物     

韩丽君  符瑞文  孙汉章 《海洋科学》2000,24(5):44-46

采用了与季铵化合物有高度化学反应特异性的雷氏盐(四硫氰基二氨合铬酸氨 ,Am moniumreinecke,ammoniumtetrathiocyanatodiamminechromate)将季铵化合物从样品中沉淀出来以达到提取和分离的目的。分析结果表明 ,海藻中季铵化合物的含量很丰富 ;绿藻特别是浒苔中的季铵化合物含量最高可达到1.31 %。  相似文献   

On Biochemical Formation of Salt Deposits     

WEI Dongyan  DENG Xiaolin  LIU Zhenmin  YANG GengshengGeological Institute for Chemical Minerals  Zhuozhou  Hebei 《《地质学报》英文版》2000,74(3):613-617

A water/salt system in an evaporative environment is both a physicochemical region and a biological one. All the parameters of the system, such as the salinity, temperature and CO2 partial pressure, are affected by halo-philic bacteria. The system controls salt deposition but is modified by an accompanying ecological system; therefore it should be called a water/salt/biological system. Salt minerals result from accumulation of the remains of bacteria/algae, namely, bacteria/algae formation; whereas biological, biophysical and biochemical processes provide full evidence for organic involvement. Consequently, salt deposits should not be called purely chemical but biological/chemical ones. This new argument supplements and develops the traditional idea and helps perfect the mineralization theory of salts and even general deposits, thus giving guidance to prospecting for salt deposits.  相似文献   

西北地区干旱化趋势及水盐失衡的生态环境效应   总被引：17，自引：0，他引：17       下载免费PDF全文

徐恒力  周爱国 《地球科学》2000,25(5):499-504

基于对西北地区干旱化趋势的讨论, 研究了西北内陆封闭盆地水盐迁移聚集的系统动力学模式, 阐明了盆地浅表积盐与水盐失衡的根本原因.在此基础上, 探讨了水盐分布与生态适宜性之间的内在联系以及水循环节律的变化对土壤生态指数时空分布的影响, 提出建立西北地区各物种的生存域及土壤生态指数对西部大开发具有重要意义.此外, 还讨论了内陆盆地水库工程兴建与灌溉技术选择问题   相似文献