青海沱沱河地区多才玛铅锌矿床成因:原位S和Pb同位素证据

青海沱沱河地区多才玛铅锌矿床是西南三江特提斯北段新生代铅锌矿集区的典型矿床之一,本文首次应用飞秒激光剥蚀多接受器等离子体质谱法对多才玛铅锌矿床中金属硫化物的原位S和Pb同位素进行了测定。结果显示:黄铁矿、方铅矿和闪锌矿的原位S同位素的δ~(34)S_(V-CDT)值介于-26.34‰～4.24‰之间,均值-12.15‰(n=20),其中闪锌矿的δ~(34)S_(V-CDT)值介于-10.30‰～-3.52‰,均值-7.39‰(n=9);方铅矿的δ~(34)S_(V-CDT)值为-26.34‰～-11.74‰,均值-20.36‰(n=9);黄铁矿的δ~(34)S_(V-CDT)值分别为2.50‰,4.24‰。矿床δ~(34)S数据范围较宽,总体表现为富集负值硫的特征,说明有机质可能参与成矿。岩浆热液期发育的黄铁矿δ~(34)S值具有深源特征,沉积热液期发育的方铅矿和闪锌矿的δ~(34)S值表明成矿过程存在还原作用,指示盆地地层还原流体的混入,综上可认为多才玛铅锌矿床硫具有混合来源的特征。方铅矿原位Pb同位素结果为~(206)Pb/~(204)Pb=18.866～18.929,~(207)Pb/~(204)Pb=15.674～15.689,~(208)Pb/~(204)Pb=39.052～39.174。方铅矿与地层的Pb同位素组成一致,位于上地壳平均Pb演化线之上,具上地壳和地幔混合俯冲带铅的特征,表明其成矿物质的来源多样。结合矿床学、矿物学及同位素数据,本文认为多才玛铅锌矿床S元素主要来源于赋矿围岩,Pb金属元素主要来源于藏北钾质火山岩,侵入地层岩浆与盆地流体的混合是金属硫化物沉淀的重要机制。     

甘肃毕家山铅锌矿床成矿地球化学特征

本文系统地研究了甘肃西成铅锌矿田毕家山矿床的成矿地球化学条件、矿床成因和成矿物质来源。研究结果表明:(1)该区成矿金属物质主要取自基底地层,而不是含矿层。地层地球化学和铅同位素研究都证实了这一论点;(2)该矿床矿石硫主要取自海水硫酸盐的还原硫;(3)矿床成矿流体的水主要来源于渗流加热的大气降水和部分回灌的海水;(4)该矿床应属于同生热液沉积-动力分异热液强改造型层控铅锌矿床。本文并建立了该矿床的成矿模式,以便直观地了解该矿床的成矿地球化学条件。     

赣中南产铀钨系列花岗岩岩石化学数值多元判别及地质效果

由于赣中南及邻区地壳初始物质应分的不均匀性而导致的地壳重熔型花岗岩岩石化学成分和成矿元素的差异,以及U、W-Sn、TR、Nb-Ta等与壳型花岗岩有关的成矿元素地球化学性质的差异,决定了这些元素的不共生性,而各自有其成矿专属岩体。按成矿专属性可将本区燕山期花岗岩划分为产U系列花岗岩和产TR、W-Sn、Nb-Ta系列花岗岩。二系列岩体的岩石化学成分和副矿物组合有明显的差别。据此建立的岩石化学数值多元线性判别函数式能判别二系列岩体;对产W-Sn、TR、Nb-Ta系列岩体能进行二级判别,同时能判别壳源型花岗质侵出岩的产矿性,以及区分加里东期交代花岗岩及混熔过渡型Cu花岗若。     

北京市怀柔县北干沟金矿床地质特征及找矿方向

北干沟金矿床位于燕山金矿成矿带中段,属含金韧性剪切带石英脉型金矿床.新太古代变质岩含金丰度高,是金成矿的矿源层.韧性剪切带对金矿化具有控制作用.金矿化可分为2期,其与韧性剪切带脆性变形作用有关.自然金主要分布于黄铁矿、黄铜矿及其氧化物的微裂隙、粒间或空洞中.围岩蚀变强烈,主要类型有黄铁矿化、硅化、绢云母化、碳酸盐化、钠长石化、绿泥石化、重晶石化等.矿区今后的主要找矿方向是在I号断裂破碎带中寻找石英脉型、蚀变岩型金矿化和在Ⅱ号韧性剪切带东段的张性扩容段中寻找含金剪切带石英脉型金矿化.     

Extreme P-, Bi-, Nb-, Sc-, U- and F-rich zircon from fractionated perphosphorous granites: The peraluminous Podlesí granite system, Czech Republic

The strongly peraluminous and P-rich, protolithionite and zinnwaldite leucogranites from Podlesí, western Krušné Hory Mts., Czech Republic, contain accessory zircon with extraordinary enrichment of several elements, which constitute trace elements in common zircon. Elements showing a not yet reported anomalous enrichment include P (up to 20.2 wt.% P₂O₅; equivalent to 0.60 apfu, formula calculated on the basis of 4 oxygen atoms), Bi (up to 9.0 wt.% Bi₂O₃; 0.086 apfu), Nb (up to 6.7 wt.% Nb₂O₅, 0.12 apfu), Sc (up to 3.45 wt.% Sc₂O₃; 0.10 apfu), U (up to 14.8 wt.% UO₂; 0.12 apfu) and F (up to 3.81 wt.% F; 0.42 apfu). Strong enrichment of P preferentially involved the berlinite-type substitution (2 Si⁴⁺  P⁵⁺ + Al³⁺) implying that significant Al may enter the Si position in zircon. Incorporation of other exotic elements is primarily governed by the xenotime (Si⁴⁺ + Zr⁴⁺  P⁵⁺ + Y³⁺), pretulite (Sc³⁺ + P⁵⁺  Zr⁴⁺ + Si⁴⁺), brabantite-type (Ca²⁺ + (U, Th)⁴⁺ + 2P⁵⁺  2Zr⁴⁺ + 2Si⁴⁺), and ximengite-type (Bi³⁺ + P⁵⁺  Zr⁴⁺ + Si⁴⁺) substitution reactions. One part of the anomalous zircons formed late-magmatically, from a strongly peraluminous, P–F–U-rich hydrous residual melt that gave rise to the zinnwaldite granite. Interaction with aggressive residual fluids and metamictization have further aided in element enrichment or depletion, particularly in altered parts of zircon contained in the protolithionite granite. Most of the zircon from F-rich greisens have a composition close to endmember ZrSiO₄ and are chemically distinct from zircon in its granite parent. This discrepancy implies that at Podlesí, granitic zircon became unstable and completely dissolved during greisenization. Part of the mobilized elements was reprecipitated in newly grown, hydrothermal zircon.     

Thermodynamics of U(VI) sorption onto Shewanella putrefaciens

We have conducted acid–base potentiometric titrations and U(VI) sorption experiments using the Gram negative, facultatively anaerobic bacterium Shewanella putrefaciens. Results of reversed titration studies on live, inactive bacteria indicate that their pH-buffering properties result from the equilibrium ionization of three discrete populations of functional groups. Carboxyl (pK_a=5.16±0.04), phosphoryl (pK_a=7.22±0.15) and amine (pK_a=10.04±0.67) groups most likely represent these three resolvable functionalities, based on their pK_a values. Site densities for carboxyl, phosphoryl and amine groups on the bacterial surface were approximately 31.7 μmol sites/g bacteria (0.35±0.02 sites/nm²), 8.95 μmol/g (0.11±0.007 sites/nm²) and 38.0 μmol/g (0.42±0.008 sites/nm²), respectively, based on an estimated bacterial specific surface area of 55 m²/g. Sorption experiments showed that U(VI) can reversibly complex with the bacterial surface in the pH 2–8 interval, with maximum adsorption occurring at a pH of 5. Sorption is not strongly sensitive to ionic strength (NaCl) in the range 0.02–0.10 M. The pH and ionic strength dependence of U(VI) sorption onto S. putrefaciens is similar to that measured for metal-oxide surfaces and Gram positive bacteria, and appears to be similarly governed by competitive speciation constraints. Measured U(VI) sorption is accounted for by using two separate adsorption reactions forming the surface complexes >COO–UO₂⁺ and >PO₄H–UO₂(OH)₂. Using S. putrefaciens as a model organism for dissimilatory metal-reducing Gram negative anaerobes, our results extend the applicability of geochemical speciation models to include bacteria that are capable of reductively solubilizing or precipitating a wide variety of environmentally and geologically important metals and metallic species.     

云南金平地区金矿化类型及找矿方向

云南金平地区位于三江造山带哀牢山成矿带南段,是我国重要黄金勘查、生产基地。区内金矿化类型主要有蚀变岩型、石英脉型、红土型和冲(洪)积型。通过对金平地区内的地层、构造、岩浆岩等控矿因素的分析,发现区内的金矿床(点)与构造—岩浆活动关系密切。区内金矿床(点)主要产于古生代浅变质岩系地层中,受NNW向、NW向及NE向断裂及各类侵入岩控制,金矿化与区内岩浆类型有成因上的联系。最后,指出铜厂—大坪一带为区内重要的金成矿远景区。     

华南火山岩及铀成矿相关的Sr,Nd,Pb同位素演化规律研究

本文应用Ｓｒ,Ｎｄ,Ｐｂ同位素演化示踪获得：华南各地区中生代火山岩的同位素演化受区域古陆（基底）变质岩、早期改造衍生体和再循环陆壳制约;铀成矿同位素组成具有地壳来源性。燕山期大陆边缘增生作用,导致陆内下地壳岩浆活动及拉张裂陷等地壳运动,促成铀的迁移富集成矿。     

赣南双峰式火山盆地铀成矿性的地球化学评价

赣南的白面石盆地、东坑盆地、菖蒲盆地均分布有双峰式火山岩。在白面石盆地,已探明及开采有铀矿床,而多年的野外工作及室内研究,在菖蒲和东坑盆地却未发现有重要工业价值的铀矿床。笔者通过对这些盆地的铀含量进行分形特征研究,加上其他地球化学论证,认为白面石盆地具有典型的成矿特征,而菖蒲盆地、东坑盆地有一定的成矿潜能。     

汞热释谱在寻找铀,金矿床中的应用

本文介绍了汞热释谱技术及在找铀矿、金矿中的应用。其主要内容是；成矿期石英的ＨｇＳ／ＨｇＣｌ２比值的Ｒ＞１，而矿前期石英Ｒ＜１；岩石的矛热释话通常为低温（＜２８０℃）普通峰，而矿石、矿物的汞热释谱则为中温（２８０—６００℃）、高温（６００—８００℃）特征峰；在矿床中汞化合物具有水平分带性：ＨｇＳ在内带，ＨｇＣｌ２在外带；成功地应用于对硅化带合矿性评价。