铜陵冬瓜山层状铜矿同位素地球化学及成矿机制研究   总被引：12，自引：0，他引：12  

徐兆文陆现彩  高庚方长泉  王云健杨小男蒋少涌  陈帮国 《地质论评》2007,53(1):44-51

长江中下游地区是中国重要的铜、金、硫产地,区内分布着一系列喷流沉积及喷流沉积热液叠加改造型层状铜金矿床。本文以冬瓜山层状铜矿床为例,通过热液流体和矿石同位素地球化学研究,探讨层状铜矿床的成矿机制,重点分析了成矿物质的来源。冬瓜山铜矿床热液流体氢、氧、碳和锶同位素分析表明,成矿热液流体主要来自岩浆,混有少量大气降水;CO2可能主要来自被岩浆同化的原始地层中海相沉积碳酸盐;ISr具有地壳物质来源的特征。各种类型矿石的硫、铅同位素研究显示,硫具有海底喷流沉积和后期岩浆热液叠加作用的特征,铅则以上地壳铅为主,混有少量的地幔铅。上述同位素地球化学特征表明冬瓜山层状铜矿床是在原始沉积基础上,经燕山期岩浆热液叠加成矿作用所形成。  相似文献   

Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China   总被引：1，自引：1，他引：0  

L&#; E  ZHANG Lei  CHEN Min  QIU Yusheng  XING N  YANG Weifeng  LI Yanping  HUANG Yipu 《海洋学报(英文版)》2008,27(1):29-41

Surface water was collected from the Jiulong Estuary for determination of activity concentrations of uranium isotopes in different size fractions, namely, greater than 53, 10 -53, 2 - 10, 0.4 -2 μm, 10 000 u -0.4 μm and less than 10 000 u fractions by microfihration and cross-flow uhrafiltration technologies. Results indicated that most of the dissolved uranium （ 〈 0.4 μm） exis- ted in the low molecular mass fraction （ 〈 10 000 u）, and the colloidal uranium-238 （10 000 u -0.4 μm） only contributed less than 1% of the dissolved uranium-238. The fractions of colloidal uranium in the dissolved phases decreased with the increasing sa- linity. A positive linear relationship between uranium-238 activities and salinities was observed for the dissolved, colloidal and low molecular mass fractions, indicating a conservative behavior of uranium in the Jiulong Estuary. In the particulate phases （ 〉 0.4 μm）, the partitioning of uranium isotopes among different size fractions was controlled by the partitioning of particle concentrations. In the regions with salinities below 20, the partitioning of uranium-238 among different size fractions was as follows： 10 - 53 μm 〉 2 - 10 μm 〉 0.4 - 2 μm greater than above 53 μm. However, the order at the offshore station with salinities above 30 changed as follows ： 0.4 - 2 μm 〉 10 - 53 μm 〉 2 - 10 μm greater than above 53 μm. The fraction of the 0.4 - 2 μm particles increased at the offshore station, suggesting the increased contribution of the authigenic uranium. The activity ratio of uranium-234 to uranium-238 in the dissolved phases, including the low molecular mass fraction and the colloidal fraction, was larger than unity, showing the occurrence of excess uranium-234. In contrast, the activity ratio of uranium-234 to uranium-238 in all size fractions of the particulate phase was close to the equilibrium value （1.0）. The observed different values of the activity ratio of uranium-234 to uranium-238 in the dissolved phase and the partic  相似文献   

大豆蛋白废水处理中泡沫分离过程的数学模型     

杨向平  刘元东  席作家  翟绪丽 《中国海洋大学学报(自然科学版)》2008,38(1):111-115

假设吸附过程始终处于平衡态、气泡大小均一以及每一个气泡均为正十二面体,构建了泡沫分离过程的数学模型.模拟了液池中蛋白质在气液界面上的吸附过程和泡沫层中气泡的失水过程,得出了富集比的表达式,可用于分离效果的预测.经验证,模型与实验条件下的泡沫分离过程基本符合.  相似文献   

沁水煤层气田高阶煤解吸气碳同位素分馏特征及其意义   总被引：3，自引：0，他引：3  

胡国艺  李谨  马成华  李志生  张敏  周强 《地学前缘》2007,14(6):267-272

沁水盆地是我国煤层气勘探开发的重要有利区,沁水煤层气田位于盆地东南部。对采自沁水煤层气田两口井的煤开展了罐解吸实验。结果表明,该地区煤层气解吸速率很快,96 h后解吸气量都达到了总解吸气量的60%~85%,720 h后解吸过程基本结束;解吸气量大,平均在18 m3/t以上。煤层气解吸过程中甲烷发生碳同位素分馏,δ13C1值变化与解吸率呈良好的线性关系,参考这种正相关关系曲线,定期监视煤层气降压排采过程中甲烷δ13C1值的变化情况,可以大致推测出该地区煤层气解吸率,从而预测煤层气的采出程度。跟踪测试沁水煤层气田A1和A1-3井在试采过程的甲烷δ13C1变化情况,推测现在采出的煤层气可能主要是煤层裂隙中以游离形式存在的煤层气,表明该区煤层气稳产性较好,资源前景广阔。  相似文献   

Archean (about 2500 Ma) anatexis in eastern North China Block     

Si-hong Jiang  Leon Bagas  Yi-fei Liu  Li-li Zhang 《China Geology》2021,4(2):215-229

Two Neoarchean alkaline feldspar-rich granites sourced from partially melted granulite-facies granodioritic orthogneiss have been here recognised in the eastern part of the North China Block (NCB). These poorly foliated granites have previously been assumed to be Mesozoic in age and never dated, and so their significance has not been recognised until now. The first granite (AG1) is a porphyritic syenogranite with megacrystic K-feldspar, and the second (AG2) is a quartz syenite with perthitic megacryst. Zircons from the granites yield LA-ICP-MS U-Pb ages of 2499 ± 10 Ma (AG1), and 2492 ± 28 Ma (AG2), which are slightly younger than the granodioritic orthogneiss that they intrude with a crystallisation U-Pb age of 2537 ± 34 Ma. The younger granites have higher assays for SiO₂ (71.91% for AG1 and 73.22% for AG2) and K₂O (7.52% for AG1 and 8.37% for AG2), and much lower assays for their other major element than the granodioritic orthogneiss. All of the granodioritic orthogneiss and granite samples have similar trace element patterns, with depletion in Th, U, Nb, and Ti and enrichment in Rb, Ba, K, La, Ce, and P. This indicates that the granites are derived from the orthogneiss as partial melts. Although they exhibit a similar REE pattern, the granites have much lower total REE contents (30.97×10⁻⁶ for AG1, and 25.93×10⁻⁶ for AG2), but pronounced positive Eu anomalies (Eu/Eu* = 8.57 for AG1 and 27.04 for AG2). The granodioritic orthogneiss has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70144, εNd(t) value of 3.5, and εHf(t) values ranging from −3.2 to +2.9. The orthogneiss is a product of fractional crystallisation from a dioritic magma, which was derived from a mantle source contaminated by melts derived from a felsic slab. By contrast, the AG1 sample has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.6926 that is considered too low in value, εNd(t) value of 0.3, and εHf(t) values between +0.57 and +3.82; whereas the AG2 sample has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70152, εNd(t) value of 1.3, and εHf(t) values between +0.5 and +14.08. These assays indicate that a Sr-Nd-Hf isotopic disequilibrium exists between the granite and granodioritic orthogneiss. The elevated εHf(t) values of the granites can be explained by the involvement of Hf-bearing minerals, such as orthopyroxene, amphibole, and biotite, in anatectic reactions in the granodioritic orthogneiss. Based on the transitional relationship between the granites and granodioritic orthogneiss and the geochemical characteristics mentioned above, it is concluded that the granites are the product of rapid partial-melting of the granodioritic orthogneiss after granulite-facies metamorphism, and their crystallisation age of about 2500 Ma provides the minimum age of the metamorphism. This about 2500 Ma tectonic-metamorphic event in NCB is similar to the other cratons in India, Antarctica, northern and southern Australia, indicating a possible connection between these cratons during the Neoarchean.  相似文献   

多接收电感耦合等离子体质谱Cu同位素测定中的干扰评估   总被引：15，自引：1，他引：14  

蔡俊军  朱祥坤  唐索寒  李世珍  何学贤 《高校地质学报》2006,12(3):392-397

多接收电感耦合等离子体质谱（MC—ICP—MS）是高精度测定铜同位素的新方法,然而在测定中也可能存在干扰。为此对MC—ICPMS Cu同位素测定中的可能干扰进行了评估。主要包括以下方面的内容：（1）对所用标准物质和试剂进行了纯化,所用标准物质和试剂对Cu同位素的同质异位素干扰可以忽略;（2）运用K和／参数进行了讨论,其中K为样品中的Cu浓度与标准溶液中Cu浓度的比值,f为在一定Cu浓度的标准溶液中干扰信号相对于^63Cu真实信号的比值。理论模拟表明,当K值小于1时,即使在质量为63处的干扰很小,对ε^65 Cu的影响也可能很大;（3）通过对理论模拟结果与实际测定结果的对比,发现对所用的试剂而言质量数为65的干扰可以忽略不计;（4）实际测定结果表明,当样品中Cu的浓度是标样中Cu的浓度的0．5～4倍时,测试获得的样品的ε^65值与其真值在误差范围内一致;（5）对潜在的基质效应重点研究了Fe和Co对Cu同位素测定的影响。实验结果表明,当Fe／Cu〈100,Co／Cu〈7时,Fe,Co不影响Cu同位素比值的测定;（6）10个月的重现性研究结果为ε^65=3．5±1．0（2SD）。该测定值在误差范围内与文献报道的值一致  相似文献   

汞同位素地球化学研究及其在矿床学中的应用进展     

徐春霞  孟郁苗  黄诚  唐春  郑芳文 《岩矿测试》2021,(2):173-186

汞作为一种重要的成矿元素,广泛分布于不同地质体中,并参与成岩成矿作用.随着质谱技术的飞跃发展,汞同位素地球化学研究取得引人瞩目的进展.汞同位素被广泛地应用于示踪地球表生生物地球化学过程及汞污染等.近年来,汞同位素又被应用于揭示行星的演化过程、识别地质历史时期大火成岩省及示踪矿床成矿物质来源等方面.本文在前人研究的基础上...  相似文献   

南海北部东沙天然气水合物区浮游植物生物量和生产力粒级结构特征及其环境影响分析     

康建华  梁前勇  王建军  林毅力  何雪宝  夏真  郑新庆  王雨 《海洋学报(英文版)》2018,37(1):97-107

本文讨论了2013年5月南海东沙天然气水合物区浮游植物生物量和生产力粒级结构特征及其环境影响因素。结果表明,研究海域表现出典型的低营养盐、低叶绿素a、低生产力特征,浮游植物叶绿素a和初级生产力具有明显的次表层最大值现象。东沙海域生物量和初级生产力粒级结构差异性显著,从生物量和生产力贡献度来看,表现为微微型浮游植物> 微型浮游植物> 小型浮游植物。生物量的垂直分布结果表明,春季不同粒级类群浮游植物在真光层内的分布存在明显不同,比如小型浮游植物在真光层内分布较均匀;微型浮游植物则主要分布于近表层或真光层中部,而微微型浮游植物则主要分布于真光层中部和底部。微微型浮游植物在纬度较低的热带贫营养海区之所以能够占主导优势,最主要的原因是其极小的细胞体积和较大的表面积使其有利于营养竞争。相关性分析表明,南海东沙浮游植物各粒级生物量与温度、pH显著正相关,与硅酸盐、磷酸盐显著负相关;浮游植物各粒级生产力与温度显著正相关,与盐度、磷酸盐显著负相关。磷酸盐含量是影响东沙海域浮游植物粒级结构差异的重要因素之一,同时,光辐照度和水体的真光层深度对东沙天然气水合物区不同粒径浮游植物的垂直分布起着更为重要的调控作用。  相似文献   

多接收器等离子体质谱(MC-ICPMS)高精度测定Nd同位素方法   总被引：24，自引：1，他引：23  

何学贤  唐索寒  朱祥坤  王进辉 《地球学报》2007,28(4):405-410

多接收器等离子体质谱是近年发展起来的高精度同位素分析手段之一,通过用等离子体质谱测量Nd国际标准材料La Jolla和JMC Nd203以及实际样品GBW04419,研究MC-ICPMS测量Nd的质量分馏特点,解决MC-ICPMS测量的关键所在质量分馏校正.通过修正分馏系数,可以实现理想的分馏校正.结果显示出所得到的分析精度达到热电离质谱的测量水平.具有实际地质样品代表性的实验室内部标准CAGS-Nd-1重现性长期分析结果为:143Nd/144Nd=0.512072±0.000008(2σ,n=140).  相似文献   

Nb–Ta fractionation induced by fluid‐rock interaction in subduction‐zones: constraints from UHP eclogite‐ and vein‐hosted rutile from the Dabie orogen,Central‐Eastern China     

J. HUANG  Y. XIAO  Y. GAO  Z. HOU  W. WU 《Journal of Metamorphic Geology》2012,30(8):821-842

Niobium and Ta concentrations in ultrahigh‐pressure (UHP) eclogites and rutile from these eclogites and associated high pressure (HP) veins were used to study the behaviour of Nb–Ta during dehydration and fluid‐rock interaction. Samples were collected through a ～2 km profile at the Bixiling complex in the Dabie orogenic belt, Central‐Eastern China. All but one eclogite away from veins (EAVs) display nearly constant Nb/Ta ratios ranging from 16.1 to 19.2, with an average of 16.9 ± 0.8 (2 SE), similar to that of their gabbroic protolith from the Yangtze Block. Nb/Ta ratios of rutile from the EAVs range from 12.7 to 25.3 among different individual grains, with the average values close to those of the corresponding bulk rocks. These observations show that Nb and Ta were not significantly fractionated by prograde metamorphism up to eclogite facies when no significant fluid‐rock interaction occurs. In contrast, Nb/Ta ratios of rutile from eclogites close to veins (ECVs) are highly variable from 17.8 to 49.8, which are systematically higher (by up to 17) than those of rutile from the veins. These observations demonstrate that Nb and Ta were mobilized and fractionated during localized fluid flow and intensive fluid‐rock interaction. This is strongly supported by Nb/Ta zoning patterns in single rutile grains revealed by in situ LA‐ICP‐MS analysis. Ratios of Nb/Ta in the ECV‐hosted rutile decrease gradually from cores towards rims, whereas those in the EAV‐hosted rutile are nearly invariable. Furthermore, the vein rutile shows Nb/Ta zoning patterns that are complementary to those in rutile from their immediate hosts (ECVs), suggesting an internal origin for the vein‐forming fluids. The Nb/Ta ratios of such fluids evolved from low values at the early stage of subduction to higher values at later supercritical conditions with increased temperature and pressure. Quantitative modelling was conducted to constrain the compositional evolution of metamorphic fluids during dehydration and fluid‐rock interaction focusing on Nb–Ta distribution. The modelling results based on our proposed multistage fluid phase evolution path can essentially reproduce the natural observations reported in the present study.  相似文献