中国内生钼矿床辉钼矿的微量元素特征研究

近年来,金属硫化物微量元素研究取得了重大进展,但主要局限于少数常见的硫化物,如黄铁矿。辉钼矿作为内生金属矿床最常见的金属硫化物之一,目前对其微量元素的研究成果还很少,对微量元素的赋存状态及其揭示的成因意义还不明。文章尝试性地对中国57个内生独立钼矿床或共伴生钼矿床中的辉钼矿进行了ICP_MS微量元素分析。结合元素的地球化学性质及前人的研究成果,认为除Re、Os等少数元素可成类质同象存在于辉钼矿中以外,推测大部分微量元素可能以固溶体出溶、机械混入物或流体包裹体等形式存在于辉钼矿中。各矿床中辉钼矿微量元素相对于中国陆壳富集Cu、Zn、Pb、W等常见的成矿元素,暗示不同地质环境下不同时代和矿床类型的成钼流体搬运的成矿元素具有一致性和普遍性,这是造成钼多金属矿床金属元素矿化分带的基础。辉钼矿的主要微量元素呈对数正相关,受矿床类型和产出环境影响不大;辉钼矿Co/Ni比值多数1,集中于0.01~0.57,不同矿床类型的Co/Ni比值具有一定规律性:当w(Co)30μg/g时,斑岩型和矽卡岩型矿床中辉钼矿的Ni含量比较稳定;当w(Co)30μg/g时,Ni含量比较高;石英脉型矿床的Co/Ni比值变化较大,且小于斑岩型矿床的Co/Ni比值。在内生金属矿床中,辉钼矿主要形成于还原性环境中,但石英脉型矿床的形成条件与斑岩型矿床相比,其氧化性明显增强。根据分析结果和前人研究成果,推测成钼流体应为富CO2和Cl-(个别还富含F-)以及部分还原性气体成分(H2、CO、CH4等)的成矿流体。     

西秦岭成矿带中东段金矿床成矿规律和找矿预测

西秦岭近年来在新区发现新矿床和新类型金矿,矿床的地质特征表明金矿成矿受岩性、构造、岩浆活动的制约,许多金矿的地质、地球化学特征显示成矿与岩浆岩在时间和空间上关系密切;分析认为金矿主成矿时间为印支晚期-燕山早期,与区域大规模的岩浆活动在时间上一致;金矿主要有夕卡岩型、热液脉型和与岩浆活动有关的微细浸染型三种类型。矿石矿物元素组合显示由北而南成矿深度变浅、剥蚀程度较低;根据金、汞、锑矿床点和金、砷、锑、银元素分布特征,认为在北带岩体旁侧应注意寻找夕卡岩型和热液脉型金矿,中、南矿带在已知矿床深部注意寻找热液脉型金矿,有锑、汞矿点的区域注意深部及外围金矿的找矿;通过分析,最后圈定18处下一步重点工作区。     

Quartz resources in the Serra de Santa Helena formation,Brazil: A geochemical and technological study

This study presents an evaluation of Brazilian quartz deposits of Corinto and Olhos D'água, in Minas Gerais State, as potential high purity raw material for the production of silica glass. Both deposits are part of the Serra de Santa Helena formation, which holds other quartz deposits. Several quartz samples from these mines were analyzed to evaluate their chemical purity, by determination of the content of trace elements by ICP-MS after acid digestion. The technological characteristics of the ores after flame-fusion into silica glass were evaluated according to their bubble generation and UV transparency. The results indicate that silica glass with chemistry suitable for crucible applications can be obtained from materials of both mines, and even optical grade silica glass can be manufactured using transparent ore from one of the mines. In addition, this work explores the trace elements composition of each mine, as well as their fluid inclusions, and characterizes the mines as being of hydrothermal origin. Small differences in the physical and chemical characteristics of quartz that could affect the technological behavior of the ores are related to the geological history of the mines and provide interesting insights regarding the exploration of other quartz resources within the same geological formation.     

Permian volcanic rocks from the Apuseni Mountains (Romania): Geochemistry and tectonic constraints

An Early Permian volcanic assemblage is well exposed in the central-western part of the Apuseni Mountains (Romania). The rocks are represented by rhyolites, basalts and subordinate andesites suggesting a bimodal volcanic activity that is intimately associated with a post-orogenic (Variscan) syn-sedimentary intra-basinal continental molasse sequences. The mafic and mafic-intermediate rocks belong to sub-alkaline tholeiitic series were separated in three groups (I–III) showing a high Th and Pb abundances, depletion in Nb, Ta and Sr, and slightly enriched in LREE patterns (La_N/Yb_N = 1.4–4.4). Isotopically, the rocks of Group I have the initial ratios ⁸⁷Sr/⁸⁶Sr_(i) = 0.709351–0.707112, ¹⁴³Nd/¹⁴⁴Nd_(i) = 0.512490–0.512588 and high positive ?_Nd270 values from 3.9 to 5.80; the rocks of Group II present for the initial ratios values ⁸⁷Sr/⁸⁶Sr_(i) = 0.709434–0.710092, ¹⁴³Nd/¹⁴⁴Nd_(i) = 0.512231–0.512210 and for ?_Nd270 the negative values from −1.17 to −1.56; the rocks of Group III display for the initial ratios the values ⁸⁷Sr/⁸⁶Sr_(i) = 0.710751–0.709448, ¹⁴³Nd/¹⁴⁴Nd_(i) = 0.512347–0.512411 and for ?_Nd270 the positive values from 1.64 to 2.35. The rocks resembling continental tholeiites, suggest a mantle origin and were further affected by fractionation and crustal contamination. In addition, the REE geochemistry (1 > Sm_N/Yb_N < 2.5; 0.9 > La_N/Sm_N < 2.5) suggests that these rocks were generated by high percentage partial melting of a metasomatized mantle in the garnet peridotite facies. The felsic rocks are enriched in Cs, Rb Th and U and depleted in Nb, Ta, Sr, Eu, and Ti. The REE fractionation patterns show a strong negative Eu anomaly (Eu/Eu* = 0.23–0.40). The felsic rocks show the initial ratios the values: ⁸⁷Sr/⁸⁶Sr_(i) = 0.704096–0.707805, ¹⁴³Nd/¹⁴⁴Nd_(i) = 0.512012–0.512021 and for ?_Nd270 the negative values from −5.27 to −5.44. They suggest to be generated within the lower crust during the emplacement of mantle-derived magmas that provided necessary heat to crustal partial melting.     

Photoluminescence of synthetic titanite-group pigments: A rare quenching effect

Chromium-doped titanite and malayaite samples, which were synthesised to evaluate their performance as ceramic pigments, show remarkable photoluminescence behaviour. Emissions of centres related to traces of trivalent rare-earth elements (REE) are observed exclusively from chromium-free samples. Their Cr-doped analogues (containing the same REEs on the same concentration levels), in contrast, only show broad-band Cr³⁺ emission whereas all REE emissions are suppressed. This behaviour is assigned to quenching of REE emissions by chromium centres (i.e., REE³⁺ → Cr³⁺ energy transfer).     

斑岩型铜钼矿床重要共(伴)生元素赋存状态与分布规律

斑岩型铜钼矿床除主要成矿元素Cu,Mo外,还往往共(伴)生Re,Co,Au,Ag等重要元素,综合回收利用共(伴)生金属具有重大资源及环境效益。通过研究斑岩型铜钼矿床中共(伴)生元素Re,Co,Au,Ag的品位、储量、赋存状态及分布规律,认为Co主要以类质同象形式赋存于黄铁矿中,其分布与黄铁矿密切相关,通常浓集于绢英岩化带外侧;Au,Ag主要以自然金、银与金银系列矿物的形式产出,Au,Ag在不同硫化物中的含量、颗粒粒度以及赋存形式差异很大,Au在各蚀变带均有可能富集,但主要浓集区域是钾化带与石英-绢云母化带;Ag在早期主要以Cu-Ag-Au的形式富集于绢英岩化带,晚期以Pb-Zn-Ag形式赋存于青磐岩化带;Re的分布与绢云母化带的辉钼矿密切相关。     

磁铁矿中微量元素和铂族元素的组成特征

文章分析了磁铁矿中铂族元素(PGE)含量的特征,发现磁铁矿中铂族元素富集为10-9级,主要为PPGE(即Pd,Pt,Rh)。富集PPGE的主要原因是其在热液活动的晚期阶段可以被轻微的再分配和富集,其含量的高低严格受岩浆结晶过程中氧逸度的控制。磁铁矿的结晶程度直接影响岩浆体系的氧逸度,控制了PGE的含量分布,进而影响成矿。     

茶尖岭矿区M28异常分布区银多金属矿源条件浅析

茶尖岭矿区M28异常分布区银多金属矿的形成与燕山期中酸性浅成岩浆岩有空间、成因联系,属于浅成热液矿床中的矽卡岩型成因。银多金属的成矿是热液活动、构造作用的产物,根据地层中元素的初始含量及矿源岩来阐明该异常分布区银多金属矿源条件。初步分析认为,板岩类及闪长玢岩为M28异常分布区的矿源岩,该异常分布区地层中银多金属元素的初始含量较高,该异常分布区银多金属成矿的矿源条件比较好。     

内蒙拜仁达坝银铅锌多金属矿床地球化学异常分带模型研究

拜仁达坝银锌多金属矿床为岩浆热液矿床,通过分析该矿床不同中段微量元素和烃类组分的含量变化特征及其异常展布规律,建立了该矿床的地球化学异常分带模型。     

昌吉站迁站对气象要素影响及热岛强度指标分析

选取昌吉站旧址1981—2013年（其中1981—2008年为迁站前昌吉站资料,2009—2013年为旧址作为区域站Y5522所采集资料）、新址2009—2013年资料进行对比分析,并对新旧站址资料进行T检验,结果表明：迁站前后,新址与旧址气温、相对湿度、风速变化趋势基本一致,但变化幅度新址较旧址略大。两站气温差冬季变化最为明显,夏季变化最小;平均相对湿度新址较旧址偏高,各季差值在冬季最小;平均风速较旧址偏大0.9 m/s,最多风向新址为西风及西南风,旧址为西风;从年平均值的连续性看,年平均气温、年平均最低气温、年平均相对湿度连续性较差,年平均最高气温与年平均风速连续性相对较好。