粤东成矿地质背景及银-铜-铅-锌成矿物质来源探讨

通过对粤东地区地层和岩石中成矿元素含量和区域地质背景的分析,认为粤东地区铜铅-锌-银成矿作用与燕山期的构造-岩浆作用关系密切,成矿物质中银-铜-锌以下地壳来源为主,铅则以上地壳及沉积地层来源为主。     

河南省南召县梅子垛铁矿矿床成矿地质特征及矿石加工技术性能

2005～2007年,在河南省南召县白土岗-南河店-带发现数十个风化花岗闪长岩型超贫磁铁矿床。矿体的形态、产状、规模与花岗闪长岩体基本一致,矿石类型、成分简单,磁性铁品位2．79～13．28％,平均9．02％,矿石易采易选,在当前经济技术条件下,开采该类矿床具较好经济效益。笔者以梅子垛铁矿为例分析说明该类矿床成矿地质特征及矿石加工技术性能。     

济宁颜店铁矿地质特征及济宁岩群含矿性研究

伏于济宁滋阳山一带千米盖层之下的古元古代济宁岩群是一套低绿片岩相变质含铁岩系,主要岩石组合为千枚岩、板岩、磁铁石英岩等,其原岩为海相含灰质泥岩、砂岩类中酸性火山岩、硅铁岩等,该套岩系最大控制厚度达580m。其中赋存的条带状磁铁石英岩呈层状、似层状埋深在1612．89～1796．54m之间,共有5层铁矿,总厚度85．53m。估算预测的铁矿资源量（334）9．76亿t,mFe平均品位22．37％;低品位矿体预测的资源量（334）2．64亿t,mFe平均品位16．99％。     

泥石流堆积物的粒度分布及其分形结构

泥石流堆积物主要由砾石、砂砾、粉粒和粘粒组成,组成泥石流堆积物的颗粒级配变幅很大,从直径大于数十米的巨砾到肉眼难以看见的几微米的胶体微粒均有分布,大小颗粒粒径之比可达106—107。泥石流堆积物颗粒具有明显的自相似性和无标度区间。本文以小江流域多处泥石流堆积物为研究对象,采用图解法全面分析了泥石流堆积物的粒度组成特征,根据分形理论计算了泥石流堆积物颗粒的分维值,对泥石流堆积物的分形特征进行探讨,并与泥石流堆积物粒度特征相联系,发现分维很好的反映了泥石流堆积物颗粒组成及其粒度分布特征。将泥石流堆积物颗粒分维与泥石流的粘性、形成年代等性质相联系,以找出它们彼此之间的关系。     

Climatic changes and alluvial-sedimentation settings in southeastern Transbaikalia in the Middle-Late Holocene (by the example of the Ilya floodplain)

Climatic changes in southeastern Transbaikalia in the Middle and Late Holocene and their influence on alluvial sedimentation environments are reconstructed from the results of study of the Ilya floodplain sediments (Alkhanai National Park). At the beginning of the Subboreal period, the regional climate became more arid, which led to a significant increase in steppe species communities in the landscapes. Intense climate aridization also took place at the beginning and at the end of the Subatlantic period of the Holocene. The alluvial-sedimentation rate increased during the weakening of aridization and decreased during cooling and the intensification of aridization. The obtained regional data are compared with data on the adjacent areas and the global climatic changes in the Northern Hemisphere.     

Radiocarbon redating of contaminated samples from a tropical volcano: the Mansion ‘Series’ of St Kitts,West Indies

Heavy rainfall and dense vegetation on tropical volcanoes produce abundant carbonized wood in pyroclastic deposits, in addition to easy contamination of this wood by root systems and soluble humic material. Because the physical nature of the charcoal varies, some samples are more prone to contamination. Two independent studies of the same volcano, Mt Liamuiga on St Kitts in the Lesser Antilles, sometimes using samples from the same carbonized tree, yielded a systematic difference in radiocarbon ages. An exchange of samples and a re-investigation of three physically distinct types of charcoal yielded the following results. Rare, hard, dense charcoal, lacking contamination, which had yielded a spurious age of 2860 years bp, was redated at 1845±58 years bp. Common soft, friable charcoal with good cellular structure proved to be susceptible to contamination. A field decontamination technique utilized by one group seems significant as it yields older ages than when only routine laboratory pre-treatment was used, indicating that the latter technique only partly removes the dried and hard residue produced by the decomposition of modern plant rootlets. A previous date of 24870 years bp obtained from powdery charcoal in a horizon beneath the Mansion Series contradicted ages older than 41000 years bp from common friable charcoal in the lower Mansion Series. The soft powdery charcoal was re-investigated using a sample collected a few centimeters from the original, although field decontamination of this sample was not possible, more extensive laboratory treatment yielded an age of ca. 43000 years bp, again proving that routine laboratory pretreatments are inadequate. A revised geochronology for the Mansion Series is described and a cautionary discussion is presented for the benefit of investigators using radiocarbon ages to date volcanic deposits.     

新疆第四纪盐类矿产的形成和控制因素——兼论“高山深盆”成盐模式

根据袁见齐教授“高山深盆”成盐模式,探讨新疆天山对第四纪盐类矿床的形成和控制作用,阐述了天山地貌、气候、水文特征与盐类矿产的分布规律和特征。认为“高山深盆”并非一定是四周环山的深盆,可以是某一高山与其间深盆或两侧盆地的有机组合。高山的屏障作用造成了垂直的气候分带,在潮湿多雨的山区利于成盐组份的析出并迁移到干旱少雨的闭流深盆中,形成盐类矿床。     

中国南方离子吸附型稀土矿床成矿类型及其母岩控矿因素探讨

传统认为中国南方的离子吸附型稀土矿床可划分为以“足洞式”为代表的重稀土型和以“河岭式”(或“花山式”)为代表的轻稀土型两种矿化类型。然而，近年来发现的许多矿床(如清溪、寨背和馒头山等)的赋矿风化壳中出现了轻稀土矿与重稀土矿并存现象，表现出特殊的“上轻下重”双层矿体结构。这指示了除重稀土型和轻稀土型之外，还存在着轻重稀土共生型的过渡类型。本研究通过对三种不同成矿类型的若干典型矿床系统对比，指出成矿类型的多样性与母岩性质密切相关，尤其是母岩的稀土元素地球化学和稀土载体矿物属性是制约成矿类型变化的关键因素。统计数据表明，从重稀土型→轻重稀土共生型→轻稀土型，成矿母岩的全岩稀土总量变化不大(ΣREY: 200×10-6~450×10-6→200×10-6~500×10-6→200×10-6~800×10-6)，但轻重稀土配分值出现较显著的区间性差异(ΣLREE/ΣHREY: 02~1→1~5→2~10)。与之同时，母岩中能为离子相稀土提供物源且具有重稀土配分属性的稀土副矿物类型和数量明显减少，这与全岩稀土元素地球化学特征中重稀土分量占比的降低趋势也互相匹配。该结果指示，以往认为重稀土配分母岩形成重稀土矿床、轻稀土配分母岩形成轻稀土矿床的传统观点需要外延，即一部分具有低度轻稀土配分属性(1＜ΣLREE/ΣHREY＜5)且含有丰富易风化稀土副矿物的母岩还可能形成轻重稀土共生型矿床，该认识可为今后离子吸附型稀土矿床勘查工作提供新的找矿依据。     

High-resolution sequence stratigraphy of the Lower Triassic ‘Buntsandstein’ in the Netherlands and northwestern Germany

Detailed log correlations of the largely fluvio-lacustrine Lower Triassic Buntsandstein (Late Permian-Early Anisian), carried out on 80 wells in the Dutch onshore and offshore areas, can be linked to northwest-German high-resolution sequence stratigraphy. The correlations show that cyclic sedimentation occurred in large parts of the basin. Seven 1st-order sequences are recognised, namely the Main Claystone, Rogenstein, Volpriehausen, Detfurth, Hardegsen, Solling and Lower Röt Sequences. They are overlain by the lower part of the Upper Röt–Lower Muschelkalk Sequence. Distinct sequence boundaries have been identified at the bases of four sequences: Volpriehausen, Detfurth, Solling and Upper Röt. The higher-order sequences consist of fining-upwards cycles with a thickness of up to tens of metres. The sequences are laterally persistent and have a characteristic expression on gamma-ray and sonic logs. In the Lower Buntsandstein, they display a uniform character throughout most of the area, with only minor differences in thickness or lithology. NNE-oriented lows and swells were formed during deposition of the Volpriehausen, Detfurth and Hardegsen Sequences. Uplift prior to the deposition of the Solling Sequence caused deep erosion on the swells in the basin and minor erosion in the lows. The high-resolution sequences probably represent alternating, relatively wet and dry climatic periods, with a periodicity of about 100 000 years. An analysis of the sequences suggests that their reduced thickness on the swells is mainly the effect of erosion. This is supported by analyses of the accumulation patterns and rates.     

Sector collapse,sedimentation and clast population evolution at an active island-arc volcano: Stromboli,Italy

Sciara del Fuoco is the subaerial part of a partially filled sector-collapse scar that extends to 700 m below sea level on Stromboli volcano. The collapse occurred <5000 years ago, involved 1.81 km³ of rock and is the latest of a series of major collapses on the north-west flank of Stromboli. A north-east trending arc-axial fault system channels magmas into the volcano and has caused tilting and/or downthrow to the north-west. The slope of the partial cone constructed between the lateral walls of the collapse scar acts as a channelway to the sea for most eruptive products. From 700 m below sea level and extending to >2200 m and >10 km from the shore to the NNW, a fan-shaped mounded feature comprises debris avalanche deposits (>4 km³) from two or more sector collapses. Volcaniclastic density currents originating from Sciara del Fuoco follow the topographic margin of the debris avalanche deposits, although overbank currents and other unconfined currents widely cover the mounded feature with turbidites. Historical (recorded) eruptive activity in Sciara del Fuoco is considerably less than that which occurred earlier, and much of the partial fill may have formed from eruptions soon after the sector collapse. It is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the Tyrhennian basin. Evidence that the early post-collapse eruptive discharge was greater than the apparent recent flux (2kg/s) counters suggestions that a substantial part of Stromboli's growth has been endogenous. The partial fill of Sciaria del Fuoco is dominated by lava and spatter layers, rather than by the scoria and ash layers classically regarded as main constituents of Strombolian (cinder) cones. Much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra, which is therefore rapidly transported to the sea. Delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport, mainly in avalanches and by shoreline wave reworking, and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast-forming processes. Considerable amounts of dense (non-vesicular) fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate. The submarine extension of the collapse scar, and the continuing topographic depression to >2200 m below sea level, are zones of considerable by-passing of fine sand and silt, which are transported in turbidity currents. Evidently, volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast-forming processes that occurred during an eruption. Marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration, unless there is a high rate of discharge of pyroclastic material into the sea.