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.     

内蒙古东珺铅锌银矿床地质特征及成因探讨

在矿床地质、地球化学特征研究的基础上,讨论了内蒙古东珺铅锌银矿床的成因。地球化学研究表明：矿区岩浆岩属于钙碱性岩石系列,轻稀土和大离子亲石元素相对富集;矿石与岩浆岩稀土元素配分模式相似,矿石、矿化蚀变岩、火山岩和二长斑岩的K、Th、U、Rb均具有明显的正异常,Ta、Nb均显示负异常,暗示本矿区各种岩石具有相同的源区,主要来源于富集大离子亲石元素的富集地幔,可能有少量地壳物质的混染。矿石中金属硫化物Pb、S同位素研究表明,成矿物质来源于岩浆系统。通过矿床地质及地球化学研究,认为东珺铅锌银矿为一与火山-次火山岩浆作用有关、受断裂构造控制的热液脉型矿床,成矿与中生代火山-次火山岩浆作用关系密切,NW向和NE向断裂构造为控矿和容矿构造。     

周宁芹溪铅锌银矿床地质特征与成因初探

位于周宁芹溪铅锌银矿床产在晚侏罗—早白垩世中一酸性火山活动带上,成矿与断裂构造及次火山活动有关。该矿床经普查—详查工作,已基本查明了⑥号构造蚀变带矿床地质特征、控矿条件、矿体规模及形态特征,初步研究认为该矿床应属中低温浅成火山热液成因的硫化铅锌银矿。     

The effect of hydrodynamic conditions on true flotation and entrainment in flotation of a complex sulphide ore

The separation efficiency and selectivity of flotation are directly proportional to recoveries of the mineral species in the feed due to true flotation and entrainment. In this study, effects of the hydrodynamic conditions on true flotation and entrainment were investigated by using a fractional factorial experimental design. A method previously described in the literature was applied to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore. In order to apply the method, the kinetic flotation tests were conducted under various hydrodynamic conditions defined by some physical variables. Some of these tests were conducted in the presence and absence of a collector to evaluate the self-induced floatability. The selectivity index of the mineral species for entrainment was seen to be suitable evaluation of the non-selectivity and efficiency of the entrainment. Furthermore, the results of the size-by-size analysis of the froth products indicated that the presence of the self-induced hydrophobic particles in the feed is as important as the presence of very fine particles for accurate estimation of true flotation and entrainment in flotation of a complex sulphide ore. In addition, the estimated results for entrainment in flotation of the complex sulphide ore can be misleading. Therefore, a new approach would be necessary to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore.     

Variations of Ag/Au ratios in hydrothermal ore bodies

The analysis of the Ag and Au contents in ore bodies of different formation types reveals that the Ag/Au ratio functionally depends on the relative sulfide index of the ores (the ratio between the product of the Pb, Zn, and Cu content and the gold content). The functional dependence is best approximated by a power function. Based on 85 geochemical characteristics of 29 deposits, it is shown that the Ag/Au ratios differ in the ore bodies of volcanic and volcano-plutonic types.     

Ore-finding method of fault tectono-geochemistry in the Tongchang Cu-Au polymetallic orefield, Shaanxi, China： I. Dynamics of tectonic oreforming processes and prognosis of concealed ores

Based on the research content and conception of dynamics of tectonic ore-forming processes, with the focus on the dynamics and processes of mineral source, ore formation, transport, accumulation, dissipation and mineralization in response to magmatic invasion and metallogenic fluid under tectonic stress, this paper deals with the ore-finding method of fault tectono-geochemistry and its application on the basis of ore deposit genesis, “giant pressure shadow” structure and ore-finding method of tectonic stress field in the Tongchang orefield, expounds the rules of magmatic emplacement and ore fluid migration and concentration under the control of the structural stress field, hence providing the theoretical basis for the localization and prognosis of concealed ores. The fault tectono-geochemical features show that the Cu-Au polymetallic ore deposits (mineralization) in the orefield are closely related with volcano-(exhalation) sedimentation, magmatism and tectono-reworking. Fault tectono-geochemical anomalies can be applied to prognosis of metallogenetic target areas for ore exploration and can provide strong evidence of “giant pressure shadow” structure. In addition, quite a number of important target areas have been defined in combination with the characteristics of the tectonic stress field, and part of the target areas have been proved by practical activities.     

福建浦城双坑铅锌银矿区地质地球化学特征及找矿方向

双坑矿区位于浦城管查-建阳溪东铜多金属找矿远景区内,水系沉积物和土壤金属量测量异常规模大,套合好、峰值高,具明显的浓集中心。区内分布有铅锌银丰度值高的大金山组变质岩和燕山早期黑云母花岗岩,断裂裂隙发育,成矿地质条件有利。通过区域地质条件、异常元素组合与分布特征分析,探讨矿区找矿方向。     

豫西骆驼山硫多金属矿床的成因——来自纹层状矿石中硫化物LA-ICP-MS微量元素证据

骆驼山硫多金属矿床位于豫西栾川钼多金属矿集区,矿体主要呈似层状和透镜状产于新元古界栾川群三川组和南泥湖组的层间断裂带内的矽卡岩中,受NWW向层间断裂带的控制。该矿床在成因方面的争论的焦点在于:是否存在元古代的喷流沉积成矿作用?具有纹层状构造的硫化物矿石以往被认为是喷流沉积成因矿床的关键证据,但这种矿石结构也可能为热液交代成因。通过详细的野外地质观察,纹层状矿石在空间上主要产于矽卡岩与致密块状硫化物矿石之间,在透辉石长英角岩、矽卡岩及大理岩等围岩中也有分布,纹层状矿石交代了矽卡岩。针对纹层状矿石中的金属硫化物开展LA-ICP-MS原位微区分析,结果表明:(1)闪锌矿形成于中高温环境,其微量元素以富Fe、Mn、In、Co(均值分别为8.5%、6144×10~(-6)、321×10~(-6)和28.54×10~(-6)),贫Ga、Ge、Tl(均值分别为4.31×10~(-6)、0.98×10~(-6)和0.0476×10~(-6))等元素为特征;(2)磁黄铁矿和黄铁矿的微量元素组成均具有富Co(均值分别为57.75×10~(-6)和2787.68×10~(-6))、贫Ni(均值分别为19.24×10~(-6)和11.29×10~(-6))的特征,二者的Ni-Co关系图指示其与岩浆热液密切相关。以地质现象为基础,结合硫化物原位微区分析数据,笔者认为骆驼山硫多金属矿床中的纹层状矿石属于岩浆热液成因。     

福建清流仁场铅锌银矿找矿方向分析

清流仁场铅锌银矿是受推覆构造和层位双重控制的热液矿床．已控制矿体的赋存位置有明显的规律性,大致分布于“S”形的中部破碎带较厚的部位．由于断裂面产状变化引起的局部张性环境有利于热液交代和充填所致。根据这一观点,相应的构造位置就是今后的找矿靶区。