西藏多不杂铜矿床硫铅同位素地球化学示踪

多不杂铜矿床的发现是西藏地质找矿工作取得的重大突破,前人对其做了大量的研究,但始终未能合理解释该矿床的形成过程,究其原因主要是因为成矿物质和成矿流体来源认识上存在争议。本次研究指出了前人在多不杂铜矿床成因机制认识中存在的问题,并测试了岩矿石及单矿物的硫铅同位素组成。研究表明,矿床中硫主要来源于深源岩浆,幔源岩浆和流体在参与成岩成矿过程中伴随岩浆结晶成岩交代岩石而致自身流体性质演变,进而引发壳幔物质混染;铅同位素具有由岩浆作用形成的地壳与地幔混合的俯冲带铅的特征,伴随着含矿地幔流体的上升侵位,不可避免的混染了地壳铅,导致了多不杂铜矿床铅同位素组成的变化。综合分析认为该矿床的成矿物质和成矿流体主要来源于地幔,成矿动力主要来自深部地质过程,矿床的形成与地幔流体作用有关。     

中国新生代上地幔铅同位素地球化学场对成岩、成矿物质来源的制约——以斑岩铜矿床及铜镍硫化物矿床为例

区域成矿带铅稳定同位素地球化学研究是区域地球化学分区、示踪成岩成矿物质来源、阐明矿床成因的有效途径。本文以中国特有的大地构造背景为基础,以新生代上地幔铅同位素组成的地球化学场为依据,示踪了中国大型、超大型斑岩型铜矿床及铜镍硫化物型矿床的成岩成矿物质来源。结果显示:①斑岩型铜矿床及铜镍硫化物型矿床成矿母岩继承了所属陆块的上地幔铅同位素组成特征;②两类矿床的含矿岩体和矿石矿物铅同位素组成十分一致,示踪两者同源;壳熔花岗岩和围岩地层的铅同位素组成与矿石铅同位素组成迥异;③位于各陆块的斑岩型铜矿床及铜镍硫化物型矿床的成矿母岩和矿石铅同位素组成除继承了各陆块上地幔不同的铅同位素组成特征外,还示踪了壳幔层圈间耦合性的"块体效应",同时,上地幔铅同位素组成可能还具"延迟效应"。     

阿尔泰造山带岩石和矿石的氩同位素研究

通过对新疆阿尔泰造山过程中形成的岩石、矿石样品氩同位素组成的研究 ,认为阿尔泰造山带的形成与壳幔相互作用有关 ,造山过程中的地幔脱气现象是存在的。喀拉通克铜镍硫化物矿床的成矿物质主要来自于地幔。可可托海 3 脉伟晶岩型超大型稀有金属矿床的成矿物质及基性超基性岩的母岩浆主要也来自于地幔。而大喀拉苏花岗岩结晶分异型伟晶岩矿床与库威变质型伟晶岩矿床的成矿物质来自于地壳 ,将军山天河石花岗岩与富蕴县城附近的含铜石英脉也主要是地壳物质演化的结果     

西藏邦铺铅锌矿床S、Pb、C、O同位素组成及成矿物质来源研究

邦铺铅锌矿床系邦铺钼铜矿区斑岩矿化体外围形成的矽卡岩型铅锌矿床;矿石品位较富,成矿元素以铅锌为主,基本不含铜。文章以矿床中主要金属硫化物为研究对象,采用S、Pb同位素研究方法对矿床成矿物质来源进行探讨。结果表明,矿石金属硫化物δ34S值分布范围较宽,但主要集中于-3.7‰～-0.7‰之间,具塔式分布特征,硫主要来源于岩浆;矿石铅同位素组成稳定,为正常普通铅,矿石铅的高μ值(大于9.58)及构造环境演化图解中样品点的分布特征指示矿石铅主要来源于上地壳物质。与驱龙外围知不拉、甲玛矽卡岩矿体对比研究发现,3个矿床硫均为岩浆来源;而金属物质来源空间上则显示出一定的规律,驱龙—甲玛—邦铺矿集区由南向北壳源物质的混染作用不断增加;大理岩及方解石碳-氧同位素组成特征显示矿床成矿流体中碳源主要来自于岩浆,碳酸盐岩地层提供了部分成矿物质。     

云南金顶铅锌矿床成矿物质来源及有机成矿作用

分析了金顶铅锌矿床同位素及生物标志化合物特征,探讨了矿床成矿物质来源及有机成矿作用。结果表明,矿石铅主要来自上地幔,成矿流体主要为地幔流体和盆地卤水。矿区有机质的母质来源以低等水生生源的海藻类为主,同时伴随有一定量的陆源高等植物组分的输入,有机质来源于三叠纪三合洞组碳酸盐岩地层。有机质在成矿作用中可能起到的作用有：还原硫酸盐提供成矿所需的硫源;形成有机一金属络合物,活化运移成矿金属元素;改变成矿物理化学环境对成矿物质的还原沉淀作用。     

滇西保山地块金厂河铁铜铅锌多金属矿床硫铅同位素特征与成矿物质来源示踪

滇西金厂河铁铜铅锌多金属矿床位于保山地块北部,是"三江"多金属成矿带内典型矿床之一。对该矿床开展硫铅同位素示踪研究,探讨成矿物质来源,并结合构造背景和成矿时代分析了矿床成矿机制。样品测试结果表明,矿石中硫化物的δ~(34)S值为+2.5‰～+11.1‰,平均值为+5.65‰,硫同位素来源为深部幔源岩浆和岩浆上侵混染壳源物质形成的多种硫源同位素组合;矿石矿物铅同位素组成中~(206)Pb/~(204)Pb为18.167～18.497,~(207)Pb/~(204)Pb为15.668～15.779,~(208)Pb/~(204)Pb为38.554～38.997,铅同位素总体较稳定,显示壳幔混染特征,以上地壳铅为主,可能来源有深部侵入岩浆及赋矿围岩。由矿床成矿物质来源表现出的多源、深源-浅源的特征推测,与成矿有关的中酸性岩体隐伏在区域深部。     

云南金宝山铂钯矿Nd-Os同位素特征及成因意义

金宝山铂钯矿是峨眉山大火成岩省具有典型意义的岩浆Ni-Cu-PGE矿床,成矿岩体岩矿石Sm-Nd、Re-Os同位素特征表明为地幔柱成因并受到岩石圈地幔和地壳混染作用的影响.∈Nda=+0.01～+0.89,显著高于大陆岩石圈地幔,而低于软流圈地幔,介于地幔柱与岩石圈地幔之间但明显靠近地幔柱的同位素组成.γOs=20～60,高于任何端员类型的地幔储集库,反映地壳混染作用.混合模型分析表明,成矿岩浆演化经历了10%左右的大陆岩石圈地幔熔体混合并受到下地壳5%～10%的混染.     

浙江淳安银山银铅锌多金属矿床硫铅同位素地球化学特征

银山银铅锌多金属矿是近几年来在该区域发现的中型以上的银铅锌多金属矿床,为地层-构造-岩浆综合控制型矿床。运用矿区的黄铁矿矿石S、Pb同位素示踪的方法探讨了矿床成矿物质来源。矿区黄铁矿和方铅矿的硫同位素组成δ34S值为-1.5‰~27.9‰,且硫同位素分布直方图中显示3种来源特征,指示成矿物质来源可能为海水、地层或岩浆。Pb同位素组成μ(~(238)U/~(204)Pb)值特征、Zartman构造模式、Δγ-Δβ成因分类研究表明,矿区矿石铅为幔-壳混源,指示物源主要来自于中生代岩浆热液,而非海底热液沉积物。综合表明银山银铅锌多金属矿床是中生代岩浆热液型矿床。     

贵州天桥铅锌矿床地球化学特征及其地质意义

通过对天桥铅锌矿床常量元素、稀土元素、同位素及微量元素等地球化学特征的分析,研究了天桥铅锌矿床的成矿物质流体来源及成矿过程。研究结果表明：（1）矿石、围岩等的稀土元素组成特点相似。∑REE相对较低,LREE/HREE比值较大,稀土配分曲线呈富轻稀土的右倾型曲线。Eu负异常明显,Ce具弱负异常特征。（2）矿床成矿物质流体多来源。受陆源影响较大,主要来自上地壳,且可能主要来自赋矿地层及围岩;无大洋地壳和原始地幔来源。（3）成矿作用为热液改造成矿。     

滇西地区下地壳铅同位素的组成及其意义

滇西地区新生代碱性侵入岩中广泛分布的麻粒岩包体可以代表该地区的下地壳岩石,为了确定滇西下地壳岩石的铅同位素组成,我们系统采集了该区碱性岩中的麻粒岩包体,挑选出其中的长石、石榴子石等造岩矿物,测定了其铅同位素组成,在Zartman等的铅构造演化模式图上,剔除个别异常的铅同位素组成,圈出投影于下地壳铅同位素演化趋势线上及附近的铅同位素分布范围,由此确定了该区下地壳的铅同位素组成的区域,并进一步结合作者先前确定的该区上地壳及上地幔铅同位素组成,构建了该区三维岩石圈铅同位素组成,并将这一结果用于滇西金顶超大型铅锌矿床的成矿物质来源的研究中,发现颇受争议的金顶铅锌矿床中的铅并非来自上地幔,而相当于下地壳来源的铅与兰坪盆地沉积岩铅二者的混合铅。     

Effects of the peat acid digestion protocol on geochemically and morphologically diverse tephra deposits

Tephra shards for electron probe microanalysis are most efficiently extracted from peat using acid digestion, which removes organic material that hinders density separation methods. However, strong acids are known to alter glass chemical compositions, and several studies have examined how acid digestion affects rhyolitic volcanic glass. The focus on rhyolitic tephra in these studies leaves considerable uncertainty, as the dissolution rates of natural glasses (including tephra) are determined by the chemical composition and surface area/volume ratio, both of which vary in tephra deposits. Here, we use duplicate samples of basaltic, trachydacitic and rhyolitic tephra to examine physical and geochemical alteration following acid digestion. Scanning electron microscope imagery reveals no discernible degradation of glass surfaces, and electron probe microanalysis results from duplicate samples are statistically indistinguishable. These findings suggest the acid digestion protocol for organic peats does not significantly alter glass geochemistry regardless of shard morphologies or geochemical compositions.     

Mineralogical features and genesis of Polyanskoye mercury deposit on Chukotka

The mineralogy of two gold deposits in southwestern China, which contain gold entirely in the form of microscopic or submicroscopic grains or inclusions, is examined. They contain refractory or low-grade ores similar in type to those near Carlin, Nevada. Mineralogical studies of ore samples from the two deposits (e.g., proton microprobe analysis, scanning electron microscope analysis, electron microprobe analysis, X-ray diffraction studies, ore microscopy) indicate that the predominant gold-bearing minerals are pyrite (Dongbeizhai deposit) and arsenopyrite and pyrite (Jinya deposit). Gold in the two deposits is closely correlated with As, S., and Fe.     

扫描电镜分析在大气颗粒物源解析中的应用

扫描电镜法作为大气颗粒物源解析的辅助方法,为源解析研究提供了定性和半定量的依据。运用扫描电镜法对吉林市采暖期和非采暖期的大气颗粒物样品以及源样品进行定性和半定量分析,将分析结果与CMB8.2化学质量平衡受体模型源解析结果进行比较,两者具有一致性。吉林市采暖期对TSP贡献较大的是扬尘和土壤风沙尘,非采暖期对TSP贡献较大的是土壤风沙尘和建筑尘。     

羌塘地区榴辉岩中矿物出溶体及其成因机制探讨

西藏羌塘地区榴辉岩石榴子石和磷灰石中均发育矿物出溶体,结合电子探针和扫描电镜分析及能谱分析,确定了石榴子石中的出溶体有金红石、石英和角闪石,指示其可能经历了高压/超高压变质作用。本研究在磷灰石中发现了金红石出溶,并认为其可能是在高压/超高压条件下元素相互置换的结果,置换方式为Ti~(4+)(Fe~(2+)、Si~(4+))=2Ca~(2+),这些出溶体的形成为榴辉岩曾经历高压/超高压变质作用提供了矿物学证据。     

深部粘性土的微观结构与力学性质试验研究分析

采用扫描电镜、X-射线衍射方法研究了拟建矿井龙固矿深部粘性土的微观结构，并进行了力学强度的测试，初步探讨了其工程地质特征及影响因素，其结果可为微观结构和宏观力学性质的研究提供参考依据。     

金牙金矿载金矿物及金的赋存状态研究

应用电子探针、电子衍射、电子顺磁共振和化学分析等多种现代方法和手段，综合研究载金矿物的特征及金的赋存状态，认为金牙金矿中载金矿物主要是毒砂和黄铁矿，金的主要赋存形式是超显微包体金，为解决金芽金矿床难处理的原生矿石提供了科学数据资料。     

SiO and GeO bonded interactions as inferred from the bond critical point properties of electron density distributions

The topological properties of the electron density distributions for more than 20 hydroxyacid, geometry optimized molecules with SiO and GeO bonds with 3-, 4-, 6- and 8-coordinate Si and Ge cations were calculated. Electronegativities calculated with the bond critical point (bcp) properties of the distributions indicate, for a given coordination number, that the electronegativity of Ge (∼1.85) is slightly larger than that of Si (∼1.80) with the electronegativities of both atoms increasing with decreasing bond length. With an increase in the electron density, the curvatures and the Laplacian of the electron density at the critical point of each bond increase with decreasing bond length. The covalent character of the bonds are assessed, using bond critical point properties and electronegativity values calculated from the electron density distributions. A mapping of the (3, −3) critical points of the valence shell concentrations of the oxide anions for bridging SiOSi and GeOGe dimers reveals a location and disposition of localized nonbonding electron pairs that is consistent with the bridging angles observed for silicates and germanates. The bcp properties of electron density distributions of the SiO bonds calculated for representative molecular models of the coesite structure agree with average values obtained in X-ray diffraction studies of coesite and danburite to within ∼5%. Received: 18 August 1997 / Revised, accepted: 19 February 1998     

Thermal evolution of organic matter in source rocks — Experimental and scanning electron microscopic studies

Five major forms (lamellar, banded, crack-like, disseminated and segregated encrustation) of organic matter distribution in source rocks have been revealed under scanning electron microscope by using the heavy metal staining technique. The degree of organic impregnation is related to the amount of liquid hydrocarbons in the rocks, and from this relationship a rough estimation of organic matter can be made on the basis of electron microscopic observations. In conjunction with experimental studies it has been found that the distribution forms of organic matter are a function of its maturity in the process of thermal evolution and accordingly some microscopic criteria can be developed for the assessment of source rocks.     

Mode of Occurrence of Gold in Micro-Disseminated Strata-Bound Sb-Au Deposits,Qinling Region,China

Optical studies,backscattered electron images,secondary ion spectrometry and highprecision transmission electron imaging demonstrate that gold is strongly correlated with arsenic on a microscopic scale in the sediment-hosted micro-disseminated gold deposits.The positive correlation between Au and As,despite varying Au/As ratio,is persistent in arsenian pyrite overgrowths and arsenopyrite,It is found that gold occurs in native state as submicro beads in association with arsenic-bearing sulfides,The extremely small grain size of gold may indicate a very rapid process of deposition.     

Nanostructural Study of a Devonian Sporoderm

The results of sporoderm studies for Paleozoic spores are obtained for the first time on a nanotomographic scanner. They are comparable to the results obtained on a scanning electron microscope (SEM) and transmitting electron microscope (TEM), verifying the interpretation of structures of the external and internal structure of the sporoderm for the objects studied. A nanotomographic scanner enables us to carry out complex studies of different sporoderm projections and to visualize the relationships and arrangement of its components without damaging the integrity of the object and losing unique Paleozoic material. Application of a nanotomographic scanner also reduces the time taken for object preparation for examination on a SEM or TEM. The nanosculpture of the exosporium of Devonian Kryshtofovichia africani Nikitin megaspores is revealed to show its two-layer structure, with the thicknesses and locations of the layers established.