Compositional characteristics and Existing Forms of Major,Trace and Rare—earth Elements in Cassiterite,Dupangling Tin Ore Field,Guangxi

Trace elements in cassiterite,including Ta,W,Fe,Mn,Ti,Zr,V,Sc,Si,Al,In,Ga,Ge,Be,Bi,Ag,Sb,As,Cu,Pb,Zn,Co and REE,have been studied by many workers (Shan Zhenhua etal.,1998;Huang Zhou Tianren et al.,1987;Wu Qingsheng et al.,1988;Hu Zening,1988,Li Zhong-qing 1988 Mingzhei et al.,1988;Wang Lihua et al.,1988;Liu Kanghuai,1990).Up to now,however,most of the previous studies are concerned with trace-element variations in cassiterites of different occurrences and colors from different types of ore deposits,Data concerning the modes of occurrence of these trace elements are rare,except for the contention that Nb-Ta,Fe^2 -Mn-Fe^3 and W-Fe^3 may substitute isomorphously for Sn as pointed out by Zhou Tianren et al.(1987) and Moller et al.(1988).In this paper we are concerned with the compositional characteristics as well as the modes of occurrence of trace elements in cassiterites from quartz veins and greisens in the Dupangling tin field,Guangxi,based on multivariate statistical analyses.Tin mineralization in the Dupangling area is found associated with the medium-to fine-grained protolithionite-albite granite(γ5^2b) and its outer contacts.Cassiterite occurs,with wolframite,both in quartz veins in the contact and in greisens within the granite.^1) Spatially,greisens become dominant over quartz veins in the contact andin greisens with the granite.^1)Spatialy,gresens become dominant over quartz veins in going from the contact to the interior of the granite and with increasing depth.The greisens are of various shapes.The vein-shaped and the sheet-shaped greisens at the top of the granie are rich in quartz and the chambered greiens always constitute rich ores and contain abundant topaz or mica.Genetically,Sn,W mineralizations associated with the protolithionite-albite granite(γ5^2b) are considered to have been formed from fluid melt derived from the ore-forming magma responsible for the granite(γ5^2b).     

广西六景泥盆纪吉维阶-弗拉斯阶界线层牙形石生物地层

广西六景泥盆系剖面是我国泥盆系标准剖面之一 ,通过对其吉维阶 -弗拉斯阶界线上下地层进行详细的牙形石生物地层研究 ,自上而下识别出 12个牙形石带 :Palmatolepis jamieae带、Palmatolepis hassi带、Palmatolepispunctata带、Palmatolepistransitans带、上 Mesotaxisfalsiovalis带、下 Mesotaxisfalsiovalis带、Klapperina dispar-ilis带、上 Schmidtognathus hermanni- Polygnathus cristatus带、下 Schmidtognathus hermanni- Polygnathus cristatus带、上 Polygnathus varcus带、中 Polygnathus varcus带、下 Polygnathus varcus带。吉维阶 -弗拉斯阶界线 (即中 -上泥盆统界线 )由 Ancyrodella binodosa→ Ancyrodella rotundiloba early form→ Ancyrodella rotundiloba late form这一演化线系中的 Ancyrodella rotundiloba early form的首次出现确定 ,处于下 Mesotaxis falsiovalis带下部 ,在谷闭组底界之上 1.80 m处。     

琼东南盆地梅山组海底扇天然气成因类型及成藏模式

琼东南盆地梅山组海底扇勘探面临烃源、运移通道及圈闭有效性评价等难题.通过开展区域油-气-岩地球化学指标对比、源-汇-岩性圈闭描述及成藏动力学分析,明确了梅山组海底扇优势运聚区及有利勘探目标.研究表明,乐东-陵水凹陷梅山组发现的天然气主要来自近凹斜坡区崖城组陆源海相烃源岩;梅山组一段海底扇储层发育规模大,扇的远端及浊积砂...     

江西庐山地区早元古代星子群变质作用和岩石地球化学特征

早元古代星子群遭受吕梁期以低角闪岩相为主的区域动力热流变质作用，变质温度约为５３０－６００℃，压力约为４００－５７０ＭＰａ。根据岩石组合及岩石地球化学特征．推测该群形成于大陆边缘环境。     

Genesis of Sr Isotopes in Groundwater of Hebei Plain

To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of 87Sr/86Sr ratio was studied. It is shown that 87Sr/86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4Heexc and a negative correlation to δ18O and δD. The groundwater is divided into three groups to discuss the relation between 87Sr/86Sr ratio and Sr2 content: ① moderate Sr2 content and higher 87Sr/86Sr ratio (water I); ② lower Sr2 content and higher 87Sr/86Sr ratio (water II); and ③ higher Sr2 content and lower 87Sr/86Sr ratio (water III), that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater (Q4-Q1) originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate disso- lution, with lower 87Sr/86Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate 87Sr/86Sr ratio. How- ever, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies.     

基于遥感技术的土地利用与土地覆盖的分类方法

分类方法在土地利用和土地覆盖变化研究中占据重要的地位。土地利用与覆盖分类首先涉及图像的处理以及分类系统的建立。目前机助分类技术主要着眼于统计模式识别和基于知识的分类决策。最终的精度评价可以进一步完善分类决策。     

凌云县麻竹种植的气象条件分析

根据麻竹的生物学特性,结合凌云县1971～2000年30a的气候资料进行分析,得出：凌云县造林季节温度适宜．旺长期和出笋期水分条件充分,地形、土壤符合种植条件,是种植麻竹理想的区域,但个别年份干旱、雨涝和低温冻害等是影响麻竹生长和产量的不利因素,应加以防范,以达到充分利用当地气候资源,提高麻竹产量和品质及进一步推广发展...     

Dynamic analysis of an axially loaded pile embedded in elastic-poroelasitc layered soil of finite thickness

This paper presents an analytical solution for determining the dynamic characteristics of axially loaded piles embedded in elastic-poroelastic layered soil of finite thickness. The interface between the elastic and poroelastic soil coincides with the groundwater table level, which is explicitly taken into account in the solution. The pile is modelled as elastic one-dimensional rod to account for the effect of its dynamic characteristics on the response of the soil-pile system. The solution is based on Biot's poroelastodynamic theory and the classical elastodynamic theory, which we use to establish the governing equations of the soil and pile. Accordingly, the pile base resistance, shaft reaction, and the complex impedance of soil-pile system are obtained using the method of Hankel integral transformation. Following the validation of the derived solution, we identify the main parameters affecting the vertical dynamic impedance of the pile via a parametric study. The presented method poses as an efficient alternative for quickly estimating the dynamic characteristics of axially loaded piles, without having to resort to complex numerical analyses.     

FASTL波段多波束馈源设计的初步分析

把抛物面天线的偏焦理论应用于FASTL波段多波束馈源系统的设计,分析了馈源喇叭横向偏焦距离与相应波束偏离角之间的关系,结合多波束射电望远镜扫描方式的要求,给出了FASTL波段多波束馈源的工作带宽、多波束馈源中相邻喇叭的间距以及喇叭口径大小的限制,并对正六边形阵列中处于不同位置的喇叭对应的波束的主瓣情况作了详细计算和分析。由此说明了FASTL波段多波束馈源采用19波束的可行性。另一方面,根据得到的工作频率带宽和喇叭口径大小的情况,对OMT和喇叭类型的选择进行了探讨。本文给出了FASTL波段多波束系统的大概轮廓,为进一步精确设计指明了方向。     

涡旋流自发辐射惯性重力波的初步解析研究

平衡流(或粗略地说涡旋流)调整目前被认为是惯性重力波产生的一种新的机制并被称为自发辐射问题。基于f平面上正压模式,该文对涡旋流自发辐射惯性重力波这一问题进行了初步解析研究。首先,通过该模式讨论了慢流形和平衡流的概念并强调了平衡流的涡旋运动特征。假定Froude数F《1且Rossby数ε=O(1)(即近似为平衡流的涡旋流包括了梯度风和其他非地转成分),于是基本方程可以写为有关惯性重力波的非齐次波动方程,其非齐次项与涡旋流的非平衡性质有关,而对于严格平衡的涡旋流,非齐次项消失,故涡旋流的非平衡性实际上提供了惯性重力波的强迫源,通过找出该方程的格林函数给出了反映自发辐射的非齐次解。在远离波源的区域,该非齐次解可以展开为远场形式,包括单极、偶极和四极辐射,另一方面,在波源区域以内及其附近,解的近场形式可以看作是慢流形的近似表达式。结果表明:与涡旋流相伴随的辐合/辐散运动主要由两部分组成,即由它自发辐射出的惯性重力波以及从属于平衡流的缓慢变化的辐合/辐散运动。与Ford的匹配渐近展开方法相比较,尽管不能给出更高阶近似,但格林函数法得到的非齐次解形式,在描写自发辐射方面更具物理直观性。