岩湾矿段风化磷矿形成条件及其三种类型     

陈拥军 《化工矿产地质》1999,21(4):225-230

湖北省鹤峰磷矿走马矿区岩湾矿段风化磷矿是湖北境内首次探明的一中型风化磷矿。矿床成因类型有风化残余型、风化淋滤型、洪积型砂磷矿等三类。在时间上 ,风化淋积型矿体位于风化残余型矿体之下 ,是风化残余型的继承发展。在雨水和洪水冲刷下 ,风化残余磷矿在适当的低洼地带堆积成洪积型砂磷矿。对这种风化矿的勘探应因地制宜 ,灵活运用。对岩湾矿段风化磷矿的成因探讨和勘探研究为东山峰寻找和勘探类似风化磷矿积累了经验。  相似文献   

Isotopic constraints on the Easter Seamount Chain source     

Q. C. Cheng  J. D. Macdougall  P. Zhu 《Contributions to Mineralogy and Petrology》1999,135(2-3):225-233

New isotopic data (Sr, Nd and Pb) for lavas from Easter and Salas y Gomez Islands, and nine seamounts along the length of the Easter Seamount Chain (ESC) to the east of these islands, exhibit a regular behavior that is consistent with two-component mixing between a MORB-like source and more enriched mantle (the Easter Plume source) characterized by relatively radiogenic Pb and unradiogenic Sr. Based on the linearity of mixing trends on the isotope diagrams, the plume source appears to have maintained approximately the same isotopic composition over the 20 to 30 Ma history of the Easter Plume sampled by the seamounts. In current nomenclature, the plume source resembles a mix of predominantly HIMU mantle with a small amount of EMI. The proportions of MORB and plume source mantle sampled by the lavas erupted along the ESC vary in a systematic way, with Easter Island and seamounts to the west containing larger fractions of the MORB component than Salas y Gomez Island and the older seamounts to the east. This variability is probably a reflection of the nearness to the spreading center, and therefore lithospheric thickness, at the time of volcanism Received: 27 April 1998 / Accepted: 11 December 1998  相似文献   

参数化线状符号设计思想与实现   总被引：2，自引：0，他引：2  

程朋根 《华东地质学院学报》1999,22(3):282-287

提出了组合式绘制线符号的方法,在此基础上提出了参数化线状符号设计思想,并用面向对象的方法和程序设计语言予以组织,实现。  相似文献   

剧冲式高速滑坡全程动力学机理分析   总被引：7，自引：0，他引：7  

程谦恭  胡厚田 《水文地质工程地质》1999,26(4):19-23

剧冲式高速滑坡是具有剧动启程,高速运行,碰撞解体及冲击成坝的高速岩质滑坡。本文根据高山峡谷区大型滑坡坝的形成过程,分析了高速岩质滑坡的临床峰残强降加速机理,滑体势动转化加速机理,空气动力擎托持速机理及滑坡坝冲击夯实机理,论述了其运动学特征。  相似文献   

地震前兆群体空间非均匀性指标Cv值研究   总被引：5，自引：0，他引：5  

王晓青  李志雄 《中国地震》1999,15(3):199-209

本文描述了排除地台站空间分布不均匀、台站观测项目数量不同等非地震成因因素影响后的前兆群体空间非均匀性研究思路及其指标Ｃｖ值,确定了Ｃｖ值反映的前兆群体空间分布图象的类型及其判定方法。利用Ｃｖ值对华北地区１９９５年以来的水氡短临前兆异常群体空间非均匀性及其与地震的关系进行了分析,结果表明,华北地区１９９５年１月１日至１９９８年２月１日发生的５次５级以上中强地震前,前兆群体空间分布出现５次非均匀性增强  相似文献   

A model for simulating the response of runoff from the mountainous watersheds of inland river basins in the arid area of northwest China to climatic changes   总被引：1，自引：0，他引：1  

Ersi Kang  Guodong Cheng  Yongchao Lan  Huijun Jin 《中国科学D辑(英文版)》1999,42(1):52-60

The subaerial tidal sand area in the northern Jiangsu Province (Subei), stretching from Dongtai towards east with a fan shape, is an early developing stage of radial sand ridges distributed in the South Yellow Sea. Since 5000–6000 a BP, after the Holocene transgression maximum in the northern Jiangsu Province, subaqueous tidal sand bodies were exposed and changed into land gradually. The environmental magnetism analysis shows that subaerial tidal sand strata are formed by the convergent-divergent paleo-tidal current field. The sediment source of tidal sand strata came early from the Changjiang River and late from the Yellow River. Sea floor erosion by tidal currents also served as an important sand source. Drilling cores and ground-penetrating profile show that there exists no probability of sand supplying directly by a large river through the apical area of tidal sand ridges either on land or in the sea. Fluvial deposits supplied the tidal sand bodies by alongshore transportation, which corresponds to the conclusions obtained by the analyses of provenance and paleocurrent field. Project supported by the National Natural Science Foundation of China (Grant Nos. 43236120 and 49676288).  相似文献   

Constitutive theories on viscoelastoplasticity and damage of frozen soil     

Ping He  Guodong Cheng  Yaanlin Zhu 《中国科学D辑(英文版)》1999,42(1):38

The constitutive theory on the viscoelastoplasticity and damage of frozen soil is based on the continuous mechanics and thermodynamics. The basic principles of the theory, dissipation potential function and damage model are presented. The constitutive theory explains the mechanical properties of frozen soils under complicated stresses, especially under high confining pressures which make frozen soil harden and soften. The agreement between the calculated results by the constitutive theory and the experimental results of triaxial creep of frozen soil is seen to be very good.  相似文献   

蒙脱石酸处理产物的表面结构变化   总被引：7，自引：0，他引：7  

吴平霄  张惠芬  郭九皋  胡澄 《矿物学报》1999,19(4):399-404

本文对广东和平蒙脱石及其酸处理产物进行了化学分析、Ｘ射线粉末衍射分析、红外吸收光谱分析、原子力显微镜及魔角旋转核磁共振等研究。结果表明,酸处理浓度对蒙脱石的表面结构有很大的影响。当酸处理浓度达到２０％时,蒙脱石硅氧四面体中的Ｑ＾３Ｓｉ环境发生结构重组,有部分转变为畸变的Ｑ＾３Ｓｉ环境和Ｑ４Ｓｉ环境,而Ａ１的结构状态则没有发生任何变化,这与原子力显微阄的观察结果相一致。  相似文献   

连云港西大堤工程后港区自然环境变化概述   总被引：1，自引：0，他引：1  

程琪  虞志英 《海洋工程》1999

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1998/1999年南极夏季普里兹湾及北部海区叶绿素a和初级生产力的分布特征   总被引：11，自引：1，他引：11       下载免费PDF全文

刘子琳  蔡昱明  陈中元  刘诚刚  朱根海  王小谷 《极地研究》2002,14(1):12-21

1998 /1 999年南极夏季 ,作者随“雪龙船”在南极普里兹湾及其北部海区 (63° - 69°1 2′S ,70°30′- 75°30′E) 3条断面 2 4个测站进行浮游生物现存量和初级生产力的现场观测 ,研究叶绿素a浓度和初级生产力的分布特征。测区表层叶绿素a浓度为 0 .1 6 - 3 .99μg/dm3,普里兹湾内和湾西部四女士浅滩海域浓度在 3 .5μg/dm3以上 ;平面分布趋势从湾内向西北方向递减 ,深海区浓度在 0 .5μg/dm3以下。从垂向看叶绿素a浓度的最大值大多出现于 2 5m或 50m层 ,50m以下更深层的浓度随深度的增加而降低 ,2 0 0m层叶绿素a浓度分布范围为 0 .0 1 - 0 .95μg/dm3。粒径分级叶绿素a浓度以微小型浮游生物的贡献占优势 (56 % ) ,微型浮游生物的贡献占2 4 % ,微微型浮游生物的贡献占 2 0 %。测区潜在初级生产力为 0 .1 1～ 1 1 .67mgC/(m3·h) ,平均值为 2 .0 0± 2 .80mgC/(m3·h)。高生产力区位于普里兹湾 ,平均现场生产力达到 0 .86gC/(m2 ·d) ;依次为陆架区、陆坡区 ,深海区生产力较低 ,平均现场生产力为 0 .1 7gC/(m2 ·d)。光合作用同化数较低 (1 .53± 1 .1 1mgC/(mgChla·h) )。粒径分级初级生产力以微小型浮游生物的贡献占优势 (58% ) ,微型浮游生物的贡献占 2 6 % ,微微型浮游生物的贡献占 1 6 %。浮游植  相似文献