Low-field variation of magnetic susceptibility measured by the KLY-4S Kappabridge and KLF-4A magnetic susceptibility meter: Accuracy and interpretational programme

The KLY-4S Kappabridge and KLF-4A Magnetic Susceptibility Meter enable automated measurement of susceptibility variation with field in the ranges of 2–450 A/m and 5–300 A/m (in effective values), respectively. Unfortunately, the measurement accuracy decreases with decreasing field and it is not easy to decide whether the susceptibility variation at the lowest fields is natural phenomenon or results from measuring errors. To overcome this problem, the accuracies of both the above instruments were investigated experimentally using artificial specimens (mixture of pure magnetite and plaster of Paris) with variable susceptibilities ranging from 1 × 10⁻⁵ to 5 × 10⁻². The complete curve of the field variation of susceptibility of each specimen was measured 10 times and the relative error was calculated for each field. In the KLY-4S Kappabridge, in specimens with susceptibilities higher than 100 × 10⁻⁶, the relative errors are lower than 3% in all fields and lower than 1% in the fields stronger than 10 A/m. In the KLF-4A Magnetic Susceptibility Meter, in relatively strongly magnetic specimens with susceptibilities 5 × 10⁻⁴ to 5 × 10⁻², the relative error is less than 1.5% in the entire field range. While the former instrument is convenient for investigating almost all rock types, the latter instrument is convenient for measuring moderately and strongly magnetic specimens. To facilitate work with field variation of susceptibility curves, showing variable accuracies with field, the programme FieldVar was written. One of its options is plotting the measured data with corresponding field-variable error bars. In this way, a tool is offered for interpreting such susceptibility changes that are sound and reasonable from the point of view of measuring accuracy.     

矿床学的发展前景和思维方法

阐述了矿床学正面临量为社会提供充足的能源和资源的严重挑战。新时期的矿床学将朝量整体化和综合化的方向发展，将研究和认识多种新型的矿产资源、矿床类型、成矿方式、矿床模式、成矿规律，乃至创立新的成矿理论体系。提出更新矿床学观念和思维法则的思想观点。     

杨家杖子钼矿开展新一轮找矿勘查前景分析

按照现代成矿理论分析，认为杨家杖子矿区及其外围寻找多矿种、新的矿床类型仍有较大的找矿空间和远景。开展新一轮找矿研究，是解决杨家杖子钼矿矿山资源危机的根本途径。     

新疆阿尔金地区清水泉铜金铂矿床特征及成因浅析

阿尔金南缘断裂带是一条深达上地幔的区域性大断裂。沿断裂分布着众多基性—超基性杂岩体。岩浆结晶分异晚期，铜、金、铂、钯元素富集，在后期断裂及热液作用下形成工业矿体，仅清水泉一处即发现三个规模较大的矿化带，通过对该化带地质特征及矿床成因分析，指出该带找矿前景极佳。     

The use of ultra-sound in the preparation of carbonate and clay sediments for chironomid analysis

Initial investigations of Holocene carbonate sediment from Hawes Water, Northwest England, yielded lower numbers of chironomid head capsules than anticipated. Standard techniques used to prepare sediment for chironomid analysis were ineffective in breaking up the coarse crystalline sediment structure sufficiently. This led to large amounts of sediment being retained and increased sample processing times. The low yield of head capsules also meant that more sediment was needed to produce adequate numbers of head capsules for analysis. The use of ultra-sound as part of the sediment processing was investigated. This technique reduced the amount of sediment left for sorting and yielded significantly more head capsules which were of equivalent structural condition and cleaner than those produced by conventional methods. The technique was extended to clay samples where similar results were obtained although shorter treatment times are recommended. The proportion of Tanytarsini and Tanypodinae heads increased significantly in carbonate and clay samples, respectively; both sediment types showed a significant decline in the proportion of Chironomini. The results indicate that ultra-sonic preparation of samples will yield a more accurate representation of chironomid assemblages in sediments leading to greater sensitivity and reliability in analysing past environmental conditions.     

胶东芦家金矿钠长石成因矿物学研究

芦家金矿钠长石化为胶东东北部成矿带中首次发现。对芦家金矿钠长石进行矿物成因分类,确定钠长石为１个演化系列、２种成因、３种产状。通过钠长石化学成分、晶体结构、形成温度、热发光、阴极发光的研究,发现了芦家金矿钠长石的标型特征和找矿标志。     

辽阳市区软土的工程地质特征

辽阳市区地表浅部呈透镜状断续分布的松软土体———淤泥质粉质粘土为静水或缓慢流水环境沉积,经生物化学作用而形成的。本文对其分布、形成、物质结构及工程地质特性进行了较系统的描述。并依据大量现场测试及室内土工试验成果,分析论述了该层软土天然独特的含水量高,孔隙比大,强度低,压缩性高,具触变性及承载力低的工程地质特性对勘察施工及建筑物稳定性的不良影响,提出了避让、挖除、选择合适桩型等科学合理的工程处理建议。     

赣中相山元古宙斜长角闪岩的矿物学、岩石学特征及同位素地球化学研究

通过岩石学、矿物学、稀土及微量元素地球化学和Nd、Sr、Ph、O同位素组成的研究,确定相山斜长角闪岩的原岩为基性火山岩（玄武岩）,井形成于岛弧环境,主要衍生于弱亏损地幔源区,并受到地壳物质某种程度的混染。造岩矿物成分具有低角闪岩相变质作用的特征,表明它们是低角闪岩相变质作用的产物,变质作用的温压条件为550℃±,0．69Gpa±。根据斜长角闪岩原岩的形成年龄（1113Ma）及变质年龄值（726．6Ma）结合其地质地球化学特征,确认赣中相山地区存在元古宙岛弧。     

Geochemical and mineralogical properties of sulfide-bearing fine-grained sediments in Finland

 The geochemical and mineralogical characteristics of bulk samples and various size fractions of sulfide-bearing fine-grained sediments in the Petalax area, western Finland, were studied with ICP-AES (aqua regia digestion and "total" digestion) and X-ray diffraction. The sediments, which are dominated by particles <0.06 mm (clay and silt size), are composed of phyllosilicates (micas, kaolinite, chlorite, vermiculite), quartz, feldspars, amphiboles, organic matter, and secondary S minerals. The chemical analyses show that Na, Ca, and Sr are enriched in the silt and sand fractions, that Zr is enriched in the silt fraction, and that the concentrations of all other studied metals (Al, Ba, Co, Cr, Cu, Fe, K, La, Mg, Mn, Nb, Ni, Sc, Th, Ti, V, Y, and Zn) increase from the sand to the clay fraction. Sodium, Ca, and Sr occur largely in poorly dissolved feldspars, which explains the distribution of these metals in the sediments. The increase in the concentrations of most metals in the clay fraction is interpreted to be the result mainly of an increase in phyllosilicates in this size fraction. A geochemical comparison between the sulfide-bearing fine-grained sediments and glacial till shows that the former are enriched in several potentially toxic metals. It is therefore argued that the hydrological and ecological problems associated with the sulfide-bearing sediments are related not only to the production of acidity in oxidized layers, but also to mobilization and dispersion of toxic metals. Strategies to minimize damage of freshwater systems in areas covered with sulfide-bearing fine-grained sediments are suggested. Received: 20 February 1997 · Accepted: 25 August 1997