滇东地区铂钯无模型定量成矿预测与评价

文章对滇东地区在分析、建立致矿地质异常概念模型的基础上,以东川-曲靖图幅为例,探讨了采用铂钯地球化学异常与各种成矿有利地质标志相结合计算成矿有利信息量和单元总信息量,进行无模型指导下的定量成矿预测和评价的方法,圈定、评价了铂钯找矿可行地段5处,找矿有利地段3处,认为有一定的找矿潜力,可供找矿解剖验证.同时指出了该方法普遍适用于其它矿种的预测、评价及其诸多优点.     

新疆东天山土墩铜镍硫化物矿床中铂的赋存形式及其地质意义

土墩铜镍矿床位于东天山黄山—镜儿泉铜镍成矿带的西端,具有较好的铜、镍资源前景。铜镍矿石中主要金属矿物为黄铜矿、磁黄铁矿、镍黄铁矿、磁铁矿以及黄铁矿等。在详细研究土墩铜镍矿床成矿地质背景的基础上,通过对土墩铜镍矿床中浸染状矿石和块状矿石中主要金属矿物进行电子探针原位测试发现,金属矿物中Pt含量较高,范围在490~2 450 g/t之间,平均为1 713 g/t,而Pd含量则较低。进一步研究Pt的赋存形式及矿石中伴生元素Co、Se、Ag、Sb等的元素地球化学特征,结果表明,晚期成矿热液对早期镍黄铁矿和磁黄铁矿的交代使Pt常发生扩散交代作用,这种热液改造作用对贵金属元素的活化和再富集具有重要意义。此外,土墩铜镍矿床中具有高Se含量、较低S/Se比值以及高R因子值的矿段是极有可能形成铂族元素(PGE)的矿化富集带。     

Noble metals in ash-cinder wastes of the Far East thermal power plants

The distribution and speciation of gold and platinum in ash-cinder wastes of the thermal power plants of Khabarovsk krai and Primorye are considered in terms of the research methods and the results obtained. The Au and PGE contents attain 2 g/t and higher, being 0.8–1.5 g/t on average. The ash of brown coal from the Pavlovka, Khurmuli, and some other fields is characterized by elevated PGE contents. The causes of discrepancies in the analytical determination of noble metals in coaly and carbonaceous rocks are considered. Accumulation of noble metals in coal is caused largely by their sorption on carbonaceous matter. The content of noble metals in ash-cinder wastes depends on their grade in the burnt coal. The latter, in turn, depends on the metallogenic characteristics of the coalfield. Gold and platinum are of economic importance, and a special technology for their recovery should to be worked out.     

Early Palaeozoic sub-arc chromitite-bearing peridotite in the Kudi ophiolite on the westernmost Tibetan Plateau

ABSTRACT

A chromite deposit was discovered in the Kudi ophiolite in the Palaeozoic western Kunlun orogenic belt. Chromite forms elongated (<2 m in width) and banded chromitite bodies (<0.1 m in width for each band) in dunite and podiform chromitite bodies (<1.5 m in width) in harzburgite. Dunite is classified into two types. Type I dunite hosting massive and banded chromitites shows low Fo in olivine (88.1–90.9), moderate Cr^# [=Cr/(Cr + Al), 0.47–0.56] in chromite, and a positively sloped primitive mantle-normalized platinum group elements (PGE) pattern, suggesting that it is a cumulate of a mafic melt. Harzburgite and type II dunite show olivine with high Fo (>91.1) and chromite with moderate to high Cr^# (0.44–0.61), and flat to negatively sloped primitive mantle-normalized PGE patterns, indicating that they are residual mantle peridotite after partial melting. Chromite in all three types of chromitites has relatively uniform moderate values Cr^# ranging from 0.43 to 0.56. Massive chromitite contains euhedral chromite with high TiO₂ (0.40–0.43 wt.%) and has a positively sloped primitive mantle-normalized PGE pattern, suggesting that it represents a cumulate of a melt. Rocks containing disseminated and banded chromite show overall low total PGE, < 117 ppb, and a negatively sloped primitive mantle-normalized PGE pattern. Chromite grains in these two types of occurrences are irregular in shape and enclose olivine grains, suggesting that chromite formed later than olivine. We suggest that chromite-oversaturated melt penetrated into the pre-existing dunite and crystallized chromite. The oxygen fugacity (fO₂ values of chromitites and peridotites are high, ranging from FMQ+0.8 (0.8 logarithmic unit above the fayalite-magnetite-quartz buffer) to FMQ+2.3 for chromitites and from FMQ+0.9 to FMQ+2.8 for peridotites (dunite and harzburgite). The mineral compositions and high fO₂ values as well as estimated parental magma compositions of the chromitites suggest that the Kudi ophiolite formed in a sub-arc setting.     

改进BCR法测定公路两旁表层土壤中铂钯铑的化学形态

铂、钯、铑是汽车催化转换器中的主要成分,在有效治理汽车尾气污染的同时,不断排放并在环境中累积增加,随着元素的迁移、转化及地下水的循环,可能成为一种新的环境污染问题.本文将改进的BCR顺序提取法应用于铂族元素形态分析,结合铂族元素的性质,将公路两旁表层土壤样品中Pt、Pd、Rh分为酸溶态、可还原态、可氧化态和残渣态四种形态.实验优化了原始的BCR浸取条件,利用电感耦合等离子体质谱法测定Pt、Pd、Rh的各形态.各形态的精密度、检出限满足地质矿产实验室测试质量管理规范的监控要求,各形态浸取量之和与样品各元素的总量之比(回收率)在95.3％ ～ 110.0％,说明方法具有较好的准确性和重现性.通过实际样品分析,公路两旁表层土壤样品中铂族元素非残渣态含量顺序为Pd (57.23％ ～ 58.03％)＞Rh (22.64％ ～25.80％) ＞Pt(17.91 ～20.57％),研究认为铂族元素进入生物圈的几率是Pd＞ Rh＞ Pt.     

云南金宝山铂钯矿床铂族元素地球化学及找矿意义

金宝山是中国目前发现的最大的独立铂钯矿床,该岩体基性程度高,主要由橄榄石、单斜辉石组成,含大量铬铁矿〔w(Cr)约为0.5%〕。铂钯矿石呈稀疏浸染状,硫化物含量少,高铂族元素、低铜镍含量。矿体与超基性围岩界线不明显,且二者具有相似的微量、稀土元素参数和微量、稀土、铂族元素标准化配分模式,表明两者的原始岩浆具有相似的性质。超基性围岩具有高的Pd/Ir、Ni/Cu比值和Pb负异常,相反,铂钯矿石显示为低的Pd/Ir、Ni/Cu比值和Pb正异常,两者具有相似的Cu/Pd、Cu/Pt比值(≤原始地幔值),表明铂钯矿石形成于地幔柱S低度饱和环境,超基性围岩可能形成于S饱和/不饱和的地球化学界面。铂族元素地球化学的差异表明含少量富铂族元素的硫化物的含矿岩浆可能注入于稍前侵入的、且未完全固结的超基性围岩中,形成似层状矿体。峨眉地幔柱早期硫低度饱和、融离出少量硫化物以及铂族元素在硫化物/硅酸盐相中极高的分配系数是导致金宝山矿石富铂钯、贫铜镍的根本原因。金宝山是极少有的全岩体Cu/Pd、Cu/Pt值均小于原始地幔值的矿床,表明该岩体的岩浆经历了硫化物富集铂族元素的过程,推测靠近峨眉地幔柱喷发中心的基性-超基性岩体是寻找铂族元素矿床最佳远景区之一。     

四川省丹巴县竹子沟铂镍矿床铜镍铂族元素赋存状态

杨柳坪铂镍铜硫化物矿集区中分布有许多成因相似的铜镍硫化物矿床,本文在野外地质调查和镜下鉴定的基础上,通过电子探针成分测试,对四川省丹巴县竹子沟铜镍铂矿床矿石矿物成分作了详细研究。根据矿物共生组合特征,将成矿过程划分为岩浆熔离成矿期、岩浆热液成矿期和表生风化期;根据成矿作用,矿体可分为贯入型和分异型矿体;通过矿物成分晶体化学式计算,阐述了矿物的赋存状态和成因;最后结合矿床产出的大地构造环境、构造控矿等特点分析,认为丹巴竹子沟铂镍矿床为典型的岩浆熔离型矿床。     

Determination of Platinum‐Group Elements and Re‐Os Isotopes using ID‐ICP‐MS and N‐TIMS from a Single Digestion after Two‐Stage Column Separation

We report an improved procedure for the determination of the platinum‐group elements (PGE) and Re, and Os isotopes from a single sample aliquot by isotope dilution (ID) using inductively coupled plasma‐mass spectrometry (ICP‐MS) and negative thermal ionisation mass spectrometry (N‐TIMS), respectively. A two‐stage column method was used to purify PGE‐Re from their sample matrix and interfering elements (e.g., Mo, Zr and Hf) after Os had been separated by CCl₄ solvent extraction. The first column separation step used cation exchange resin (AG50W‐X8) to concentrate PGE‐Re and some potential interfering elements (e.g., Mo, Zr and Hf). In the second step, N‐benzoyl‐N‐phenylhydroxylamine (BPHA) extraction resin was used to separate PGE‐Re from the remaining interfering elements, which all remained strongly absorbed to the resin. The method was used to determine the PGE and rhenium, and Os isotope ratios in a range of geochemical reference materials (TDB‐1, WGB‐1, BHVO‐2 and UB‐N). The obtained results agree well with those previously published. This new method enables PGE‐Re abundances and Os isotopic ratios to be determined on the same sample digestion, and circumvents the problems created by sample heterogeneity when comparing PGE and Re‐Os isotope data.     

吉林省油页岩中铂族元素的化学牲及分配规律研究

采用电感耦合等离子体发射质谱仪(ICP-MS)测定了吉林省油页岩中铂族元素的含量,并对油页岩中铂族元素的化学特征、与无机组分的相关性及其分布模式等进行了分析和阐述.通过油页岩中铂族元素的含量与地壳和中国东部出露地壳中铂族元素丰度的比较表明,Rh、Ru、Ir等元素相对富集,其中松原油页岩中Rh、Ir的含量约为地壳平均值的10倍.研究区油页岩中铂族元素以Pt-Pd分配模式为典型特征,一般Pt的丰度大于Pd.油页岩中铂族元素与无机组成相关分析的结果表明,油页岩中铂族元素可能呈吸附态存在于高岭石、伊利石等粘土矿物中.     

北极8种典型痕量金属及3种铂系贵金属浓度水平变化趋势及生态风险

痕量金属进入北极的途径包括洋流注入、大气传输、陆架河流、陆地径流以及海洋中的直接沉降。研究表明,北极区域介质中Pb、Hg与Cd、Zn、Cu水平随着工业化的发展呈现出不同的变化趋势,并且铂系贵金属在北极冰雪中被检测出反映了大范围的全球污染。对北极各海域表层沉积物中的痕量金属As、Cd、Cr、Cu、Hg、Pb、Zn进行生态风险评价发现:As、Cd、Cu很有可能已经对多数海域的海洋生物产生威胁;Hg、甲基汞(MeHg)、Zn在极地动物器官中已出现了食物链累积效应,相关的毒性数据目前还缺乏研究。