秦岭镇-旬地区微细浸染型锑金矿床成矿条件及其找矿前景分析

镇（安）旬（阳）地区锑金矿化分布，与其区域地质地球化学因素，陆源断陷盆地沉积岩相变化，后期构造作用密切相关，认为镇旬地区为扬子与华北板块边缘对接过渡活动带，形成局部扩张断陷沉积盆地环境。海底同生断裂的发育，使盆地中心局限台盆环境造成陆源物质、内源组份和深部物质的混生，以及为深部含矿热液上升提供通道；在后期脆－韧性剪切变形构造叠加，地下热卤水循环改造作用，形成层控式细脉浸染型锑金矿床。该地区锑金成矿物质来源丰富，沉积构造环境优越，后期控矿构造发育，显示了潜在的细脉浸染型锑金矿床的找矿前景。     

高温高压下水岩界面反应与金的迁移富集

高温高压下水岩界面反应与金的迁移富集王玉荣阚小凤王志强（中国科学院广州地球化学研究所，广州５１０６４０）关键词水岩界面反应自发电池实验地球化学本实验以哈达门沟［１］及东坪金矿［２］为地质背景，研究钾长石岩中金矿化富集的物理化学条件。该区金矿既与早期变...     

三江地区高吉碱性岩体的岩石化学特征

三江地区的碱性岩有其独特的地质、岩石学与岩石化学特征；这些特征所记录的信息，不仅提供了高吉碱性岩区别于邻区及其它地方同类碱性岩的证据，而且也给出了识别碱性岩的标志与判定其所处的板块构造位置。     

略阳─石泉边界地质体特征

略阳─石泉构造带是一板块缝合带，经历了长期复杂的演化历史。现由不同时期、不同构造体制下的断裂构造系统，裹挟不同构造演化阶段的各类建造─蛇绿混杂岩、陆缘楔状体，岛孤岩浆岩及外来岩块等，共同组成了分隔秦岭、扬子地块的一个特殊边界地质体。     

陕西小秦岭地区太华群的重新厘定

陕西小秦岭地区太华群变质岩与国内外许多高级片麻岩区类似，存在大量的深成花岗质片麻岩体，它们经过多期变质变形作用，形成具不同基础岩石类型的多相片麻岩。本文在吸收前人研究成果的基础上，依据区内岩石组合的岩石学、岩石地球化学等特征，将原划太华群重新厘定为太华岩群、翁岔铺片麻岩套、太峪岭片麻岩套、佛头崖单元、罗斑花岗伟晶岩及葫芦沟变砂岩，并首次在本区建立了相应的构─岩石单位体系。     

Secondary ferrimagnetic minerals in Welsh soils: a comparison of mineral magnetic detection methods and implications for mineral formation

A study of mineral magnetic parameters was carried out on a Late Pleistocene and Holocene sedimentary sequence (of nearly 18 m) from Lake Bledowo (central Poland). Sediments of Lake Bledowo have already been analysed for bulk sediment mineralogy and biogenic materials. The mineral magnetic stratigraphy confirms the major changes in palaeo-environmental conditions that have been deduced from other methods. The most important mineral magnetic change results from the authigenetic formation of ferrimagnetic greigite, Fe₃S₄, during the beginning of lacustrine conditions (± 12 000 yr BP). Our data also indicate a detrital origin of overlying ferrimagnetic iron oxides. It is suggested that they originate from brown soils developed on the boulder clay constituting the west side of the lake shore. Variations of ferrimagnetic iron oxide size are related to the early diagenetic processes in the sediment. Larger particles are present in periods with early diagenesis of organic matter in anoxic conditions. This indicates the dissolution of fine magnetic particles by iron-oxide-reducing bacteria and results in homogeneous magnetic grain sizes, despite their origin from soils, characterized by a multimodal grain-size distribution.     

三峡工程永久船闸边坡岩体卸荷特性

从地貌学角度,分析了三峡工程永久船闸边坡岩体的自然及人为卸荷特性,指出了地表侵蚀、河流下切、开挖船闸等自然及人为地貌过程诱发了岩体的基本卸荷过程,构筑了一个三峡工程永久船闸边坡岩体卸荷特性的宏观模式。实地调砥及数值计算成果均表明,地貌分析法在分析实际岩体工程中,岩体卸荷特性方面具有较强的应用价值。     

Three-dimensional Rayleigh hysteresis of oriented core samples from the German Continental Deep Drilling Program: susceptibility tensor, Rayleigh tensor, three-dimensional Rayleigh law

Rayleigh hysteresis, as defined by the well-known Rayleigh relations, has been observed not only when magnetization of pyrrhotite-bearing KTB-samples is measured in parallel to a weak dc magnetic field, but also in experiments where field and measuring directions have been adjusted strictly perpendicularly to each other. Nine-tupels of independent Rayleigh hysteresis loops could thus be compiled. Their characteristic coefficients X ^ijk of initial susceptibility together with the Rayleigh loss coefficients α^jk have been proved to determine completely the samples' weak-field magnetic anisotropy. Interpreting the coefficient matrices ( X ^ijk) and (α^jk) as the tensor of initial susceptibility and the Rayleigh tensor, respectively, generalization of the isotropic Rayleigh relations in terms of corresponding tensor relationships has been suggested for the anisotropic case. Application to the KTB samples showed 3-D Rayleigh hysteresis measurements to be an excellent tool for rock magnetic analysis in terms of ore content and crystalline texture. In particular, a magnetocrystalline double texture of the basal planes of pyrrhotite precipitates and their [1120] directions of easy magnetization have been clearly detected. Surprisingly, the welt-known theorem α= const. X ²_I, formulated by Néel (1942) for the isotropic case, has been found to hold true even in tensor generalization (α_jk) = const ( X ²_jk). To reach sufficient resolution for the measurements performed, a sensitive vibrating coil magnetometer (VCM) has been developed.