Stability of arsenopyrite and As(III) in low-temperature acidic solutions

Arsenopyrite is one of the most important pri-mary arsenic mineral. In the Eh-pH diagram of the As-O2-S-H2O system, if the total arsenic concentration (TAs) is taken to be 0.75 mg/L, the total sulfur con-centration, 32 mg/L, the temperature, 25℃and the pressure, one atmosphere pressure for the discrimina-tion of arsenic species, it may be found that under hy-pergene conditions, arsenopyrite is a moderately stable mineral. Only in the strongly alkaline and reducing environment can arsenopy…     

Model Simulations on the Variability of Particulate MSA to Non-Sea-Salt Sulfate Ratio in the Marine Environment

A box model was constructed to investigate connections between the particulate MSA to non-sea-salt sulfate ratio, R, and DMS chemistry in a clean marine boundary layer. The simulations demonstrated that R varies widely with particle size, which must be taken into account when interpreting field measurements or comparing them with each other. In addition to DMS gas-phase chemistry, R in the submicron size range was shown to be sensitive to the factors dictating sulfate production via cloud processing, to the removal of SO₂ from the boundary layer by dry deposition and sea-salt oxidation, to the entrainment of SO₂ from the free troposphere, to the relative concentration of sub- and supermicron particles, and to meteorology. Three potential explanations for the increase of R toward high-latitudes during the summer were found: larger MSA yields from DMS oxidation at high latitudes, larger DMSO yields from DMS oxidation followed by the conversion of DMSO to MSA at high latitudes, or lower ambient H₂O₂ concentrations at high latitudes leading to less efficient sulfate production in clouds. Possible reasons for the large seasonal amplitude of R at mid and high latitudes include seasonal changes in the partitioning of DMS oxidation to the OH and NO₃ initiated pathways, seasonal changes in the concentration of species participating the DMS-OH reaction pathway, or the existence of a SO₂ source other than DMS oxidation in the marine boundary layer. Even small anthropogenic perturbations were shown to have a potential to alter the MSA to non-sea-salt sulfate ratio.     

鄂尔多斯盆地南部旬邑-宜君地区直罗组古层间氧化带地球化学特征及水-岩作用探讨

鄂尔多斯盆地南部旬邑-宜君地区直罗组古层间氧化带具有明显分带特征,通过对不同分带砂岩主量、微量、稀土元素及环境敏感参数特征对比研究,将旬邑-宜君地区古层间氧化带发育的水-岩作用过程划分成两个阶段：古层间氧化带形成和大规模成矿阶段、二次还原改造阶段。(1)古层间氧化带形成和大规模成矿阶段：含氧水进入目的层砂体,使砂体中Fe²⁺氧化成Fe³⁺(Fe²⁺含量最低,Fe³⁺最高);砂体中的U被氧化为U⁶⁺,形成铀酰腐殖酸盐络合物发生迁移(U、Corg、S含量最低、Th/U比值最高);长石高岭土化使Si发生流失(SiO₂含量降低);携带大量U的氧化流体运移至氧化还原过渡带(Corg、∑S含量最高、Fe²⁺含量仅低于灰绿色砂体),还原剂(有机质和黄铁矿等)将U⁶⁺还原成U⁴⁺,形成沥青铀矿;U⁴⁺与SiO₄^4-发生反应形成铀石(Th/U比...     

砂岩型铀矿的成矿地质条件与战略选区——以二连盆地和鄂尔多斯盆地为例

砂岩型铀矿是当前铀矿勘查的重点，按照其成矿特点，一般分为3种类型，即古河道型，层间氧化带型和潜水－层间氧化带型，本对这3种砂岩型铀矿产出地质条件的异同点进行了分析，初步总结了各种类型铀矿床的成矿模式，并以二连盆地和鄂尔多斯盆地例，对其成矿前景进行了宏观分析和评价。     

柴达木盆地西北部可地浸砂岩型铀矿成矿条件及找矿方向

根据水成铀矿成矿理论，本文对柴达木盆地西北部大地构造背景，盆地发展演化史，新构造运动特征，古气候及水文地质条件，铀源及找矿目的层岩性，岩相，地层结构，厚度，埋深，产状等因素综合分析，认为该盆地西北部某些地段具备形成层间氧化带砂岩型铀矿的条件。牛鼻子梁以东是新构造运动相对稳定的地区，其中冷湖地区具备形成大型层间氧化带的条件，是寻找可地浸砂岩型铀矿的有利地区。     

Corrosion behavior of anodic oxidized TiO<Subscript>2</Subscript> film in seawater

TiO₂ films were formed on metallic titanium substrates by the anodic oxidation method in H₂SO₄ solution under the 80V D.C.. Phase component and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions. Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum (EIS) and polarization curves. The result showed that the TiO₂ film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface. The average water contact angle of the film was 116.4° in dark, in contrast to an angle of 42.7° under the UV illumination for 2 hours, which demonstrates good hydrophobic property. The anti-corrosion behavior of the TiO₂ film was declining with the extended immersion time. Under dark conditions, however, the hydrophobic TiO₂ film retarded the water infiltrating into the substrate. The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight. All of those mentioned above indicate that the TiO₂ film possesses much better performance under dark condition, and it can be applied as an engineering material under dark seawater environment.     

吐哈盆地十红滩铀矿床地质特征及控矿因素分析

叙述了吐哈盆地地质概况；十红滩铀矿区找矿目的层地质和砂体特征；重点对层间氧化带的纵横展布规律、地球化学分带性及前锋与铀矿化的关系作了阐述；对十红滩铀矿床南、北矿带的空间分布、形态、规模、物质成分、铀存在形式及南、北矿带差异做了研究。通过分析，最后得出十红滩铀矿床控矿因素是层间氧化带、鼻状隆起（南矿带）和北西向断裂构造（北矿带）、同时说明了局部铀矿化产出的决定因素。     

石煤中钒的氧化动力学初步研究

含钒石煤是我国一种新类型钒矿资源,钒的氧化是石煤提钒的基础。本文对钒的氧化动力学作了初步工作,通过试验数据处理结果表明,采用Ерофеев综合动力学公式:描述石煤中钒的氧化过程:2VO2固+1/2O2=Y2O5固简明可行,较为适宜。 钒氧化反应初期阶段以动力学方式进行:n1=1,属一级反应过程;继之,n2=0.2,反应受扩散制约。测定了由动力学过程转换为扩散过程所需的反应时间及其钒氧化率,计算了这两种过程的速率常数和表观活化能。     

自然电场法在寻找层间氧化带型砂岩铀矿中的应用

介绍了自然电场形成的原理及在寻找层间氧化带砂岩型铀矿中的应用.根据氧化带与还原带的自然电位变化特征,利用自然电场法可以确定盆地层间氧化带前锋线,由此推测层间氧化带砂岩型铀矿大体空间位置.     

Sulfur Isotopic Study of the Toyoha Deposit, Hokkaido, Japan Comparison between the Earlier-Stage and the Later-Stage Veins

Abstract: The sulfur isotopic ratios (δ³⁴S) of ore minerals from the Toyoha deposit, Hokkaido, one of the largest Pb–Zn–Ag polymetallic vein-type deposits in Japan, were studied. More than 90% of the δ³⁴S values of the studied sulfide minerals collected from the Toyoha deposit range from +5 to +9%, with an average of approximately +7% irrespective of the mineral species, veins, elevations, depth, mineralization stages and mineral assemblages. Relatively uniform δ³⁴S values obtained in this study suggest that the reduced aqueous sulfur species predominated over the oxidized sulfur in the ore solution throughout the mineralization stages. Thus, the source of sulfur for the ore sulfides is postulated to be magmatic.
The temperature obtained from the fluid inclusion study and the temperature of the sulfur isotopic geothermometer are not consistent. This suggests that each mineral precipitated under disequilibrated conditions with respect to the sulfur isotope.
The change in redox conditions presumably encountered between the mineralization stages did not account for the isotopic fluctuations since the isotopic exchanges between the oxidized and reduced aqueous sulfurs are much slower than the rate of oxidation of the ore solution.