云南金顶超大型铅锌矿床沥青Re-Os法测年及地质意义

油气藏与金属矿床在世界许多沉积盆地内共存,油气成藏与金属成矿的动力学关系备受关注。云南兰坪金顶产有中国目前最大铅锌矿床,也是世界上唯一陆相沉积岩容矿、且形成于新生代的超大型铅锌矿床。矿床中常见沥青、重油等有机质,它们的形成早于或晚于铅锌硫化物成矿存在明显分歧,限制了对油气成藏与铅锌成矿关系的认识。本文针对金顶超大型矿区以古新统云龙组含砾砂岩和砂砾岩为主岩铅锌矿石中沥青,开展了Re-Os法同位素测年,获得68±5Ma的等时线年龄(MSWD=9.2,n=6),指示金顶古油气成藏形成于古新世,先于铅锌硫化物大规模成矿;烃类物质具有通过热化学还原硫酸盐提供铅锌成矿所需硫化氢的客观条件;油气成藏与铅锌成矿在云南金顶矿区很可能是一个先后发生的连续地质过程,成藏为成矿奠基,成矿伴随着油气藏的破坏。     

微波消解电感耦合等离子体质谱法测定地球化学样品中钒铬镍锗砷

地质样品中多种元素的分析,通常采用高压密封消解电感耦合等离子体质谱法(ICP-MS),而应用于测定地球化学样品中的V、Cr、Ni、Ge、As等元素,影响分析准确度的主要原因有:样品前处理方面,高压密封罐会释放Cr和Ni污染样品,同时Ge和As属于易挥发元素容易造成损失;质谱测定方面,多原子分子离子会产生干扰。本文针对两方面的干扰因素,对比了微波消解硝酸提取、微波消解王水提取、高压密封硝酸复溶、高压密封王水复溶四种前处理方法中待测元素的溶出效果以及污染或损失情况。结果表明,采用微波消解替代高压密封罐消解可消除引入的Cr、Ni污染,避免了Ge、As挥发损失,同时微波消解的时间短。而采用硝酸提取,由于避免了氯的引入,分析效果优于王水提取。且使用八极杆ICP-MS氦气碰撞模式消除了样品基体中的氯多原子分子离子干扰(如37Cl14N对51V干扰,35Cl16OH对52Cr干扰,35Cl37Cl对72Ge干扰以及40Ar35Cl对75As干扰等)。应用微波消解硝酸提取、ICP-MS测定岩石、水系沉积物和土壤国家标准物质,V、Cr、Ni、Ge、As的检出限分别为1.09、0.19、0.55、0.02、0.50μg/g,精密度(RSD)4%,而采用高压密封消解、ICPMS测定V、Cr、Ni的检出限为3.48、13.09、21.67μg/g(Ge和As由于挥发无法用此法检测)。运用微波消解硝酸提取-ICP-MS氦气碰撞模式测定地球化学样品中V、Cr、Ni、Ge、As,简化了分析流程,样品消解时间仅2 h,相比于高压密封方法(消解时间48 h)具有消解快速、多元素同时测定、检出限低的特点。     

内蒙古中部地区中新元古代黑色岩系中的金矿床及找矿远景

内蒙古中部地区中-新元古代黑色岩系发育,形成于渣尔泰白云鄂博裂陷槽内,命名为渣尔泰群和白云鄂博群。目前,仅在白云鄂博群的黑色岩系中发现并勘查了一批原生金矿。矿石主要类型为细脉型和蚀变变质岩型。金矿受层位和构造破碎带控制,金平均品位低,可形成大型或超大型矿床。因此,内蒙古中部中-新元古代黑色岩系中金矿资源潜力大,找矿远景好。     

Sillimanite group minerals: a new promising raw material for the Russian aluminum industry

The raw-material base of the Russian aluminum industry is considered. The raw materials include common (bauxites, nepheline syenites) and uncommon (nepheline ores, synnyrites, anorthosites, power-and-heating plant ashes, kaolines) types of ores. With regard to many criteria (reserves and quality of ores, technology of their processing, etc.), the problem of alumina deficit can be solved by mining sillimanite group minerals Al₂SiO₅ (wt.%: Al₂O₃ = 62.9, SiO₂ = 37.1), namely, andalusite, sillimanite, and kyanite. Their proved reserves converted to the final product (aluminum) exceed 400 mln tons. This will be enough for more than a hundred years provided that aluminum is produced in the present-day output (4 mln tons in 2008). Almost all deposits can be explored by strip mining, with application of the gravitation, flotation, and electromagnetic separation methods for ore dressing. The alumina content in concentrates reaches 60–62 wt.%. Only high-grade bauxites and the above concentration methods can ensure such a high yield of Al₂O₃. Sillimanite group minerals can be processed together with nepheline ores by sintering or be used for the direct electrothermal production of silumin and aluminum, excluding the alumina production stage. The latter method is the most promising in Russia.     

Mineralogical Characteristics of Iron Ores in Joda and Khondbond Areas in Eastern India with Implications on Beneficiation

Precambrian iron ores of the Singhbhum-North Orissa region occur in eastern India as part of the Iron Ore Group (IOG) within the broad horse-shoe shaped synclinorium. More than 50% of Indian iron ore reserves occur in this region. Massive-hard, flaky-friable, blue dust and lateritic varieties of iron ores are the major ore types, associated with banded hematite, jasper and shales. These ores could have formed as a result of supergene enrichment through gradual but extensive removal of silica, alumina and phosphorus from banded iron formations and ferruginous shale. Attempts for optimal utilization of these resources led to various ore characterization studies using chemical analysis, ore and mineral petrography, XRD analysis, SEM and electron probe micro analysis (EPMA). The ore chemistry indicates that the massive hard ores and blue dust have high iron, low alumina and phosphorus contents. Because of high quality, these ores do not require any specialized beneficiation technique for up-gradation. However, flaky-friable, lateritised and goethitic ores are low in iron, high in alumina and phosphorus contents, requiring specific beneficiation techniques for up-gradation in quality. XRD, SEM and ore microscopic studies of massive hard ores indicate the presence of hematite and goethite, while flaky and lateritic ores show a higher concentration of goethite, kaolinite, gibbsite and hematite. EPMA studies show the presence of adsorbed phosphorous as fine dust in the hard ores. Sink and float studies reveal that most of the gangue minerals are not completely liberated in the case of goethitic and lateritic ores, even at finer fractions.     

基于主成分回归分析法预测中国铁矿石需求

在论述铁矿石需求预测途径的基础上,选取影响我国铁矿石需求的8个基本因素,采用回归分析方法进行了铁矿石需求的单因素分析.单因素分析结果表明,选取的8个基本因素与铁矿石需求的相关度基本都大于0.9.对8个基本影响因素进行了主成分分析,最终降维为4个主成分.将主成分分析方法与回归分析方法相结合,建立了铁矿石的需求预测模型,并对我国2015年和2020年铁矿石的需求量进行了预测,分别为29.76亿t和26.68亿t.     

湖北古城锰矿Fe同位素特征及其地质意义

本文报导了湖北古城锰矿含锰层位中黄铁矿Fe同位素的研究结果,并利用黄铁矿Fe同位素对黄铁矿成因和大塘坡早期阶段沉积环境的氧化还原状态进行了制约。黄铁矿δ56Fe值变化范围为-0.13‰~+0.54‰,平均值为+0.22‰,显示相对于当时海水（0~-0.5‰）明显富集Fe的重同位素。本文认为黄铁矿的Fe来自海水中Fe2+部分氧化形成的Fe3+,这些Fe3+在成岩过程中被全部还原,与细菌硫酸盐还原作用形成的H2S结合最终以黄铁矿形式保存在沉积物中。大塘坡式锰矿含锰层位中黄铁矿Fe同位素特征表明,古城冰期（Sturtian冰期）结束之后,大塘坡早期阶段海洋深部已经开始氧化,但是并没有完全被氧化。     

酸消解-车载偏振能量色散X射线荧光法现场测定祁曼塔格多金属矿中高品位铜铅锌

能量色散X射线荧光光谱法(ED-XRF)是勘查与找矿现场常用的分析手段.对于高矿化度样品或矿石样品,由于存在严重的基体效应,难以找到与基体匹配的校准样品,分析数据的准确度会受到严重影响,乃至给出错误的结果,成为制约现场分析高矿化度地质样品的主要难题.本文针对XRF现场分析高矿化样品存在的问题,研制了两种具有双层薄膜结构的液体样品盒,以强酸性溶液进样,应用车载台式偏振激发能量色散X射线荧光光谱(PE-EDXRF)技术,采用标准溶液进行含量校准,二级靶钼Kα谱线的康普顿散射峰作为内标校正基体效应,实现了现场准确分析青海祁曼塔格高原矿区铜铅锌多金属矿石中的铜、铅、锌三种元素.为制备适合PE-EDXRF分析的溶液,在祁曼塔格矿区现场对实验室管理样及未知样品试验了水浴加热与电热板加热两种样品处理方式.采用电热板加热方式,分析2件矿区样品的方法精密度(RSD,n=10)均优于2％;分析4件管理样的方法准确度均优于5％(当含量＞5‰时);13件矿区未知样品PE-EDXRF与原子吸收分光光度法(AAS)分析结果的平均相对偏差为:Cu 2.87％(含量范围在0.75％～8.57％),Pb 2.82％(含量范围在0.78％ ～29.1％),Zn 6.84％(含量范围在0.11％ ～2.51％),两种方法的分析结果具有很好的一致性.而采用水浴加热方式消解样品,由于在海拔四千多米地区水的沸点仅约为88℃C,样品消解不够完全,导致测定结果系统偏低.现场实验和结果表明,在高原低气压环境下,采用电热板加热方式消解样品,结合使用双层膜液体样品盒建立的PE-EDXRF分析方法,可以解决高矿化度样品及矿石样品的较高精度现场分析问题.本文建立的溶液制样方法可以解决基体匹配的难题,结合使用研制的双层膜溶液样品盒保护了仪器,是对粉末制样法PE-EDXRF现场分析技术的一个补充和完善.     

The ‘orogenic andesite’ puzzle of C. E. Tilley: 1—Is the volatile phase the missing piece?

Some 65 years ago, C. E. Tilley, in his 1950 Presidential Address to the Geological Society of London, brought into sharp focus the then perhaps-not-fully-recognised problem of the origin of what he termed the ‘orogenic andesites’—and, in particular, their commonly constituent calc-alkaline lineage of lavas and pyroclastic materials. In spite of much investigation and progress since, the problem remains not fully resolved. The two most conspicuous features of such orogenic—i.e. island arc—volcanism are its copious, explosive, degassing and, as Tilley noted, its copious development of andesites and their more felsic associates. If these rock types were derived from basalt, the principal relevant changes in major element composition are reductions in Fe, Ca and Mg, and increases in Si, Al and (Na + K). Four principal mechanisms for inducing these changes have been proposed: (1) magmatic differentiation induced by fractional crystallisation, (2) magma mixing, (3) partial melting of an ultramafic-derived basaltic parent, and (4) crustal contamination. A fifth postulate—long recognised but only occasionally seriously considered—is that loss in the volatile phase during eruption and later degassing may make a significant contribution to the overall process. On the basis that Tilley's (and others’) orogenic basalt–andesite–dacite–rhyolite series constitutes a linear arrangement on the conventional FeO_t–MgO–(Na₂O + K₂O) diagram it is shown on numerical grounds that fractional crystallisation alone cannot account for the observed compositional trend—that, while accumulates are neither uncommon nor insubstantial in amount in modern arcs, they are olivine-rich, not magnetite-rich, and that numerical, petrological and field evidence indicates that the high oxidation/magnetite subtraction hypothesis of orogenic andesite genesis can no longer be seriously entertained. The partial melting hypothesis encounters contrary numerical evidence, closely analogous with that adduced for fractional crystallisation. Magma mixing eventually encounters the difficulty of the nature of the felsic material required for rhyolite formation, and assimilation of the preservation of primitive isotope ratios as lava evolution progresses. A fifth mechanism—volatile loss—may make a significant contribution to the relevant compositional change, perhaps in combination with one or more of the other proposed processes. Geochemical, petrological and field evidence pertaining to this is reviewed and examined, and it is postulated that indeed a combination of fractional crystallisation as the principal mechanism, volatile loss as a contributing factor, provides a plausible process. A case is made for an exploratory experimental investigation of the possibility of significant loss in a gas/vapour phase.     

ESR测年技术在第四纪冰川年代学中的研究综述

近些年,宇宙成因核素暴露年代、光释光和放射性碳埋藏年代等方法在第四纪冰碛物的年代测定中已经取得显著进展.但对于第四纪冰川沉积物10万年甚至百万年以上的冰碛物样品的埋藏年代和暴露年代,由于方法自身问题或沉积物后期地质地貌过程的改造,使上述方法存在定年方面的挑战.而电子自旋共振（ESR）广泛的测年范围,使其在第四纪样品的测年中发挥着不可替代的作用.目前,石英ESR信号的衰退特征已有许多研究进展,但是对于冰碛物中的ESR信号的研究还很少.ESR测年方法由于缺乏测年机理的研究,西方学者和国内一些测年学者对这种方法的定年存有疑虑.因此,我们在典型冰川区开展对冰碛物中石英砂ESR信号变化的机理研究,得到人工研磨可以使ESR信号强度下降到原来值的53%~69%,但并不能使ESR信号完全归零.如果在以后的研究中能够找出这些残留信号值大小,并予以扣除,将会大大提高ESR冰碛物测年精度.在今后的研究中应探求其测年机理,提高测试样品的石英纯度,增强ESR测年信号的精度,使这种方法成为冰碛物交叉测年中独立可信的测年方法之一,为第四纪冰川研究中的老冰碛物的定年提供准确的年代依据.